Design, Synthesis and Properties of Corannulene Based Blue Emitters and Carcerands

Home , Corannulene

Praveen Bachawala

A Dissertation submitted to the Graduate School

of University of Cincinnati in partial fulfillment of

the requirements for the degree of

Doctor of Philosophy

in Department of Chemistry

McMicken College of Arts and Science

Committee Chair: Dr. James Mack

Abstract

Corannulene (C20H10) – a curved polycyclic aromatic hydrocarbon synthesized in 1966 purely out of curiosity was synthesized first by Barth and Lawton to test the theory of aromaticity laid dormant until the discovery of fullerenes in mid-1980. Similarity in structure piqued the interest of researchers to find simpler route towards its synthesis which reached its peak in year 2000. Recently, corannulene was reported to be synthesized on a kilogram scale. However, its potential application for high emittance, thermally stable blue emitter needs has been limited.

Major part of my thesis (chapter two) focuses on this aspect to examine the outer rim of corannulene and target which sites resembles more like ortho/para vs. meta unlike benzene.

Functionlization of such sites with acetylene bonds would immensely help in designing highly efficient blue OLED’s with great thermal stability. We have identified two sites over corannulene’s outer rim 1,8 and 1,5 and functionalized them with acetylene bonds to extend conjugation of corannulene’s π-aromatic framework. Further enhancement in conjugation was possible by tethering terminal ends of acetylene bonds with chromophores such as phenyl, anthracene, corannulene and biphenyl to study absorption/fluorescence. Later data obtained was used to excite molecule with proper laser to examine their ability to emit intense blue fluorescence.

Chapter three focuses on our attempts to find out how the structural changes of the linker length would contribute to better understanding the aspect of conjugation and its impact on the overall bulk photophysical properties of corannulene based materials. Such study would help us identify the right proportion of linker length needed to exhibit effective conjugation with corannulene and result in designing a blue emitter with robust potential.

Chapter four demonstrates the use of corannulene as potential carcerands.

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Table of Contents

Chapter Pg.

1. Introduction 1

Corannulene…………………………………………………………. 8

Synthesis of corannulene…………………………………………….. 12

References…………………………………………………………… 20

2. Understanding Conjugation through Diethynylcorannulene series – Synthesis, Structure & Properties 23

Synthesis of 1,8 & 1,5-diethynylcorannulene…………………………. 24

(4-bromophenyl)corannulene acetylene synthesis (15) ……………...... 28

Synthesis……………………………………………………………... 30

Purity of Iodocorannulene (18) …………………………………... 34

Purity of diethynylcorannulene (16 & 17) ………………………… 35

Results & Discussion………………………………………………... 38

Conclusions…………………………………………………………. 51

References…………………………………………………………… 53

3. Importance of Linker: Synthesis, Structure & Properties 54

Synthesis…………………………………………………………….. 55

[(3Z)-4-chloro-3-buten-1-yn-1-yl)]corannulene synthesis (34)……….. 57

Results & Discussion………………………………………………... 61

Conclusions………………………………………………………….. 71

References…………………………………………………………… 72

4. Corannulene Based Carcerands – Synthesis, Structure & Properties 73

Synthesis……………………………………………………………... 75

Results & Discussion………………………………………………... 83

Conclusions…………………………………………………………. 91

References…………………………………………………………… 93

5. Experimental Details 95

6. Spectra 124

Acknowledgement

My graduate school would certainly be incomplete without acknowledging the guidance, support of several people. First and foremost I would like to thank God for bestowing his kindness upon me and providing me the strength and courage to overcome obstacles in life. I certainly extend my deepest and utmost thanks to my dear wife Mallika for her constant support, patience and endless motivation in the most needed times of my Ph.D career.

Words are certainly sparse to explain the constant support and helpful guidance by my research advisor Dr. James Mack. His strong passion and renewed excitement to explore has been the key to succeed in my career. He takes utmost care in molding a student as a whole and not just the academic aspects.

I would like to extend my sincere thanks to my committee members Dr. Bruce Ault and Dr. David Smithrud in helping me approach the problem in completely different perspective.

Further, I would like to acknowledge Dr. Necati Kaval (photochemistry/laser experiments), Dr. Jeanette Krause (crystallography) and Dr. Stephan Macha (MALDI experiments) for their helpful support in obtaining critical information to support my research.

I would also like to thank Mack group members for their continued support. Also, I would like to thank Department of Chemistry, University of Cincinnati for their financial support as to perform my research.

I would also like to thank my parents and sisters for their continued support in my highs and lows.

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List of Figures

Figure Pg.

Figure 1: OLED products and its increasing application…………………………….. 2

Figure 2: Stability & Importance of blue color……………………………………….. 3

Figure 3: Transition based on MO theory…………………………………………….. 4

Figure 4: Band-gap comparison of different π-conjugated system……………………... 5

Figure 5: Poly(p-phenylene-vinylene)…………………………………………………. 5

Figure 6: UV-Vis spectra of fullerene and difullerenylacetylene………………………. 6

Figure 7: Structural and chemical similarities of (1) with fullerene [C60] & benzene….. 7

Figure 8: Front & side view of bowl shaped corannulene (top left & bottom), Electron density map (top right) of corannulene (1)…………………………………... 9

Figure 9: Comparison study of multiethynylphenyl derivatives of (1)………………… 19

Figure 10: Target compounds to test conjugation with different chromophores……... 23

Figure 11: Two novel disubstiution patterns: 1,8 (16) & 1,5 (17) diethynylcorannulene. 24

Figure 12: Mechanistic pathway of Sonogashira coupling reaction……………………. 33

Figure 13: Absorption spectra of 1,8/1,5-diethynylcorannulene series………………... 39

Figure 14: Absorption spectra of 24, 25, and 26……………………………………… 40

Figure 15: Absorption from multiethynyl substituted corannulene (28 and 29)………. 42

Figure 16: B3LYP/6-31G* optimized structures of 20, 21, 22, 23, 24, and 25………... 43

Figure 17: HOMO to LUMO and HOMO-1 to LUMO+1 transition for 20, 21, 22 and 23…………..………………………………………………………… 44

Figure 18: HOMO to LUMO and HOMO-1 to LUMO transitions for 24 and 25…… 45

Figure 19: Fluorescence spectra with excitation at 300 nm…………………………… 46

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Figure 20: Fluorescence spectra (excitation at 400 nm)………………………………. 47

Figure 21: Excitation of 16 & 17 at different wavelengths based on its zero order

emission………………………………………………………………….. 48

Figure 22: Excitation of 20 and 21 at different wavelengths based on its zero order

emission data……………………………………………………………. 48

Figure 23: Laser excitation at 325 nm………………………………………………… 49

Figure 24: Fluorescence spectra of anthrancene along with laser excitation at 405 nm... 50

Figure 25: Laser excitation at 325 & 405 nm…………………………………………. 50

Figure 26: Surprising similarity in absorption for 20 and 31…………………………... 55

Figure 27: Influence of linker over absorption of corannulene based compounds……. 62

Figure 28: Influence of linker length on absorption of 22, 23 vs. 38, 43……………… 63

Figure 29: Influence of linker length on absorption of tetrasubstitued corannulene derivatives…………………………………………………………………. 64

Figure 30: B3LYP/6-31G* optimized structures of compound 38, 43, 44 and 47……... 65

Figure 31: B3LYP/6-31G* calculated orbital transitions for compounds 38, 39 and 43 66

Figure 32: Interaction of corannulene’s core orbitals with substituents………………. 68

Figure 33: Fluorescence of compounds with enediyne linker with emission at 300 nm.. 69

Figure 34: Laser excitation at 325, 405 and 442 nm…………………………………... 70

Figure 35: Metal complexes of different types……………………………………….. 73

Figure 36: Open [6,6] 1,5-corannulene cyclophane and [6,6] 1,8-corannulene cyclophane……………………………………………………………….. 74

Figure 37: Closed [2,2] 1,5-corannulene cyclophane and [2,2] 1,8-corannulene cyclophane……………………………………………………………….. 75

Figure 38: Synthesis of corannulene trimer held by enediyne bridges (49)……………. 80

Figure 39: Absorption spectra for compounds 31, 49, 55 and its comparison with 1,

16 and 17…………………………………………………………………. 85

Figure 40: B3LYP-6-31G* geometry optimized structures of 31, 49 and 55………….. 86

Figure 41: B3LYP, 6-31G* calculated orbital transitions of 31, 49 and 55……………. 87

Figure 42: Fluorescence spectra for 31……………………………………………….. 89

Figure 43: Fluorescence spectra of 55……………………………………………….. 90

Figure 44: Fluorescence spectra with laser excitation for compound 49……………… 90

List of Schemes

Scheme Pg.

Scheme 1: First synthesis of corannulene (1) by Barth & Lawton in 1966……………… 9

Scheme 2: Three step synthesis of corannulene using FVP……………………………. 10

Scheme 3: Second solution phase synthesis of corannulene (1) in 1996……………….. 10

Scheme 4: Semibuckministerfullerene synthesis……………………………………….. 11

Scheme 5: Importance of octabromofluoranthene towards synthesis of corannulene…. 11

Scheme 6: Large scale synthesis of corannulene (1)…………………………………… 12

Scheme 7: Total synthesis of Corannulene……………………………………………. 13

Scheme 8: Derivatives of Corannulene (1)…………………………………………….. 15

Scheme 9: Multiethynyl derivatives of corannulene (1)………………………………… 17

Scheme 10: Synthesis of 1,8-dialkyncorannulene (16)…………………………………. 25

Scheme 11: Different approach towards synthesis of 15 ……………………………… 29

Scheme 12: Synthesis of 20 and 21……………………………………………………. 30

Scheme 13: Synthesis of 22 & 23……………………………………………………… 31

Scheme 14: Synthesis of 24 & 25……………………………………………………... 32

Scheme 15: Revisiting the conditions for the synthesis of 18 & 20, to understand the failures elated towards synthesis of 24…………………………………… 35

Scheme 16: Synthesis of 26………………………………………………………….. 37

Scheme 17: Extending conjugation in multiple directions……………………………. 38

Scheme 18: Synthesis of 31...... 54

Scheme 19: Reterosynthetic strategy to incorporate novel enediyne linker……………. 56

Scheme 20: General approach towards synthesis of 32 and 33...... 56

Scheme 21: Importance of iodocorannulene in synthesizing 34……………………….. 57

Scheme 22: Synthesis of 35…………………………………………………………..... 58

Scheme 23: Synthesis of 36……………………………………………………………. 58

Scheme 24: General synthetic approach for synthesizing 37, 38, 39, and 41…………... 59

Scheme 25: Synthesis of 42, 43, 44 and 46……………………………………………. 60

Scheme 26: Synthesis of 47 and 48……………………………………………………. 61

Scheme 27: Proposed synthesis of [6,6]-1,8-corannulene cyclophane…………………. 77

Scheme 28: Failed attempt to synthesize cis-1,2-diiodoethylene...... 78

Scheme 29: Failed attempts to synthesize [6,6]-1,8-corannulene cyclophane…………… 81

Scheme 30: Failed attempt to synthesize [6,6]-1,8-corannulene cyclophane…………. 81

Scheme 31: Key intermediate 52 synthesis………………………………………….. 82

Scheme 32: Key intermediate 54 synthesis…………………………………………... 83

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List of Tables

Table Pg.

Table 1: Optimization test reactions…………………………………………… 26

Table 2: Different “Pd” sources used to synthesize 24…………………………... 36

Table 3: Calculated wavelength with TD-DFT in comparison with experimental results...... 42

Table 4: Calculated TD-DFT wavelength in comparison with experimental observation...... 67

Table 5: Experimental and TD-DFT calculated orbital transitions……………….. 85

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Introduction

Organic electronics have been of interest in several fields such as chemistry and physics for more than 50 years1. Up until recently, the electronic and optical phenomenon of these materials was restricted to academic research because of its limited practical applications. For example, electroluminescence from anthracene crystal manifested in 1960 by Pope et.al disclosed the phenomenon of organic electroluminescence2a. Unfortunately, the application of organic light emitting diodes (OLED’s) was still unrealistic due to high operating voltage and catastrophic decay of light in just few minutes of its operation2b,c. However, the ability of synthetic chemist to modify the chemical structure in ways that directly impacts the properties of the materials when deposited in thin film form has provided a new direction to this field. A breakthrough was made by Tang et.al and Slyke at Kodak, who demonstrated the use of a low voltage and highly efficient thin film light emitting diode3. Their double-layer design soon became a landmark achievement and a prototypical structure in OLED’s. Even though results reported weren’t on par with existing technology, their discovery opened the door for possibility of using organic thin films based light emitting diode

(OLED) as a platform for future generations to come. In last 15 years organic semiconductors has transformed itself rapidly from a topic of academic research interest to a wide range of applications, which include polymers LED’s4, small molecule based OLED’s5, organic lasers6, organic transistors7 and solar cells8.

Today, OLED technology has received considerable attention not only for their energy saving solid state lightning but also for their low cost, eco-friendly flat panel displays. Graphics displayed in figure. 1 clearly demonstrate their increasing popularity as display units9.

Figure 1: OLED products and its increasing applications9

Their commercial success is purely driven because of their low production cost, flexibility and lower power consumption. However, key issues like control over desired emission colors with high emission intensity, efficiency and ability to display both electrical and optical stability for longer periods of time remains a bottleneck for today’s synthetic chemist in designing these materials. More importantly, synthesis of stable blue electroluminescent organic molecules with high efficiency, good color purity at practical level of brightness remains a challenge10.

Although the OLEDs have come a long way there are still major hurdles which must be addressed in order to further advance the field. A major concern that plagues OLED display is their shorter lifetimes especially for blue OLED material1,10. 46,000 to 230,000 hours in case of red &

green OLEDs whereas only 14,000 hrs. for blue OLEDs (as OLED devices display picture with high brightness, such phenomenon would lead to higher voltages across larger band gap especially for blue emitting material in comparison to its counterpart green and red. Hence, results in faster degradation of blue emitting material over green and red OLED’s). Another issue is uneven color balance; over the period of time the OLED material which produces blue color tends to degrade faster than the rest which results in poor picture quality with unnatural color saturations as depicted in below graphics (fig. 2)9a.

Figure 2: Stability & Importance of blue color9a

Hence the future and thereby market capitalization of OLED based display technology greatly relies on synthesizing a more robust, thermally stable, easily processed and high quantum yield blue emitting OLEDs. In order to understand the concept of electroluminescence particularly with carbon based system, readers needs to familiarize themselves emphasizing the major role of conjugation and its influence in fluctuating the band gap between higher molecular orbital (HOMO)

and lower unoccupied molecular orbital (LUMO) which in turn dictates the conductance and emission color for that material.

Typically carbon is a poor conductor of electricity however, carbon based systems could act as a good conductor when arranged in form of conjugated π system. Conduction of electricity followed by its electroluminescence properties are based on band gap, ionization potentials and the difference of energies of highest occupied molecular orbital (HOMO) to its lowest unoccupied molecular orbital (LUMO). The difference between these two MOs is known as the HOMO-LUMO energy gap and is related to the minimum energy needed to excite an electron in a molecule. The energy required for an electronic transition corresponds to the molecules wavelength of radiation. An alkene bond is described by two π orbitals of different energies, bonding and antibonding (fig.3). In a conjugated molecule, there is an effective overlap of π orbitals, resulting in a π-π conjugated system. Each additional alkene bond extending conjugation creates two new energy levels allowing for the HOMO-LUMO gap to lower. The decreased gap requires less energy to excite an electron and bathochromically (red shift) shifts the wavelength of emission possibly into the visible region hence is a vital tool to control and fine tune emission color.

Let’s take a moment and examine various carbon based conjugated system with reference

Figure 3: Transition based on MO theory

to their band gap, commercial availability and processibility issues.

Figure 4: Band-gap comparison of different π-conjugated system

First conjugated polymer – Poly(p-phenylene-vinylene) (PPV) was used as active material in fabrication of an OLED (fig.5)12. PPV is insoluble and difficult to process, its incorportation into

OLED was via a soluble precursor method. This technique often involved intensive labor hours and generated high cost.

Figure 5: Poly(p-phenylene-vinylene)

In an attempt to improve processability, PPV derivatives bearing long alkyl chains13, alkoxy substitutuents13,14 and even metals15 were introduced following classical synthetic organic methods.

However, steric repulsions between sidechains causes a marked twisting of polymer backbone leading to very short conjugation lengths and corresponding aggregation led to a shift of emission into UV region. Additionally, conjugated polymeric materials are difficult to synthesize and purify.

Once an impurity is inbuilt it can either be removed by chemical treatment or thermal conversion.

Purification by either process is seldom 100% selective16.

Next in series is cyclic conjugated acenes: anthracene, tetracene, pentacene, hexacene etc. With increasing number of benzenoid rings, the band gap rapidly decreases and so is their chemical stability. For example, both green-hexacene and violet-pentacene must be handled under inert atmosphere. Similarly, dark-green heptacene has never been obtained in pure state due to rapid oxidation in air17. Moreover, strong π-π interactions are responsible for their aggregation in solution phase thereby raising concerns over their processing to produce thin films. To help improve processibility in case of anthracene; bulky substituents were introduced at 9, 10 – positions18.

Substituents introduce steric strain to help limit intermolecular π-π interactions and enhance solubility. Literature proceedings also suggest that anthracene derivative based devices showed recrystallization during device operation, because of high voltage, led to device failure19.

Fullerenes – closed π-conjugated aromatic system starts well below in comparison to acenes.

Absorbs strongly in ultra-violet region of the electromagnetic spectrum, with slight trailing into visible region, as depicted in fig(6)20. However, attempt to lower band gap by connecting two fullerene units together with an acetylene bridge introduces an sp3 hybridized carbon which disrupts the overall conjugation. Hence, even though two fullerenes are connected, because of disruption in

π-communication each fullerene unit acts independently from each other. As a result there is no net reduction of band gap.

Figure 6: UV-Vis spectra of fullerene and difullerenylacetylene

Carbon nanotubes are allotropes of carbon rolled in form of cylindrical nanostructures exhibits exceptional thermal conductivity, mechanical and electrical properties. Ability to exhibits such extraordinary properties stems from combination of discrete angle created during it’s roll up and radius formed. Inability to consistently produce carbon nanotube to tailor for specific needs remains a major bottleneck. Moreover, functionalization of carbon nanotubes to enhance its processibility often is non-regioselective21.

Different carbon based conjugated system detailed above suffers from variable aspects (solubility, reactivity, reproducibility). Fortunately, “Corannulene (1)” which appears to be placed above fullerene [60] in fig. 4 attracts the eyes of a synthetic chemist as it exhibits chemical properties similar to fullerene and other aromatic system (fig. 7).

Figure 7: Structural and chemical similarities of (1) with fullerene [C60] & benzene

Corannulene exhibits electrophilic substitution reactions, characteristic of aromatic systems and addition/insertion reactions like fullerene22. Additionally, corannulene also exhibits electrochromism

– a reversible color change via chemical or electrochemical reduction. Corannulene exhibits a permanent dipole moment of 2.07 D23, remains in solution and avoids aggregations/precipitation purely because of its rapid bowl to bowl inversion. Above all, corannulene if linked with itself via ethynyl bridge does not introduce a sp3 hybridized carbon unlike fullerene24. Because of these reasons and many more it’s worthwhile to investigate the hidden properties of corannulene which

would be highly beneficial in designing systems which could emit blue color with high quantum yields/thermal stability.

Corannulene:

Corannulene (C20H10) (1) – a curved, bowl shaped polycyclic aromatic system (fig.7), was first synthesized purely out of curiosity, to examine the theory of aromaticity, as it violates the basic principles of Huckel’s 4n+2π e’s rule, was first synthesized in 1966 in a linear 17 laborious steps, by

Barth and Lawton (Scheme 1)25. Inspite of its tedious synthesis important conclusions such as 1H

NMR showed that all ten rim protons are magnetically equivalent and appear as singlet at 7.8δ, electrochemical studies showed a reversible reduction of 1 to its radical anion and presumably dianion, and most importantly the X-ray crystal showed that corannulene is bowl shaped, with a bowl depth of 0.87Ǻ, as defined by the distance between the central ring and the rim CH carbon atoms. Unfortunately, the chemistry of corannulene became quickly dormant even after many unsuccessful attempts using fluoranthene framework to improve its synthesis failed26 but dramatic interest got renewed after the discovery of fullerenes solely due to its structurally similarities with buckminister fullerene. Hence search for more practical routes to synthesize corannulene began.

Figure 8: Front & side view of bowl shaped corannulene (top left & bottom). Electron density map (top right) of corannulene (1).

Scheme 1: First synthesis of corannulene (1) by Barth & Lawton in 1966

Inspired by pioneering work of R.F.C Brown27, Scott’s group first reported the synthesis of corannulene in 1991 on a milligram scale with 10-15% yields using flash vaccum pyrolysis (FVP) at the end to introduce curvature28. Later, the synthesis was restricted to only three steps, with FVP at the end to synthesize corannulene on gram scale (Scheme 2)29. Although this route was proved beneficial but suffered from the following: a) low yields, b) low functional group tolerance, c) gas phase reaction – hence little to no possibility of scale up.

Scheme 2: Three step synthesis of corannulene using FVP

FVP methodology was inarguably the most successful route to synthesize corannulene and other higher buckybowls but certainly its limitations far superseded its success in achieving realistically large quantities of corannulene. Thus synthesis of corannulene under mild synthetic condition

(solution phase) became an important goal. Sigel’s and Rabideau’s group spearheaded this area to find a non-FVP method based large scale synthesis of corannulene. Such an effort would certainly provide researchers an opportunity in future, to uncover beneficial properties of (1).

In 1996, Siegel et.al reported a solution based synthesis of corannulene starting from tetrasubsituted fluoranthene precursor30. Introduction of ring closure was achieved via low-valent titanium coupling and subsequent treatment with DDQ gave 2,5-dimethylcorannulene in albeit 18% combined yield (Scheme 3).

Scheme 3: Second solution phase synthesis of corannulene (1) in 1996

Inspite of the modest yield this route offers an elegant approach of using tetrabromide as a building block in the synthesis of corannulene and most importantly this solution based method introduces substituents regioselectively, which was not possible by FVP method. Soon after Sigel’s publication the chemistry of reductive coupling was put to test. Surprisingly, octakis-bromomethyl

derivative resulting from radical bromination of octamethylated hydrocarbon did not undergo reductive ring closure when treated with several reducing systems31. Instead the same protocol when applied on dodecabromide produced semibuckministerfullerene in modest yields (Scheme 4).

Scheme 4: Semibuckministerfullerene synthesis

Key points from these experiments where that octabromo-methyl groups are more sterically crowded and exhibit higher steric congestion hence could easily be aromatized in comparison to less croweded tetrabromo-methyl groups and additionally eliminates an extra step with DDQ.

Following this hypothesis, Rabideau’s group brominated tetramethyl fluoranthene with NBS under forcing conditions to produce octabromide which underwent ring closure with reducing agents in anhydrous condition to deliver (1) in an impressive yield of 70-75% (Scheme 5)32.

Scheme 5: Importance of octabromofluoranthene towards synthesis of corannulene

In an effort to further simplify the method, Rabideau’s group discovered an appealing alternative method to 1,2,5,6-tetrabromocorannulene from octobromocorannulene by the use of sodium hydroxide, where the ring closure is formed by the deprotonation of the benzylic hydrogen under basic conditions (Scheme 6)33.

Scheme 6: Large scale synthesis of corannulene (1)

Hence, after 35 years of its original report by Barth & Lawton, a practical & convenient synthetic procedure capable of producing corannulene on a multigram scale not involving high temperatures, harsh conditions, high dilutions and air sensitive organometallic reagents was reported by Sygula’s group. A recent publication from Sigel’s group provides a further refinement of corannulene synthesis on a kilogram scale34.

Synthesis of Corannulene (1):

However, the synthesis of corannulene (1) developed in our lab overlaps on multiple fronts in terms of intermediate with Siegel’s recent publication. Commercially available 2,7- dihydroxynapthalene (2) from Acros was treated with carbamylchloride in presence of pyridine to transform corresponding hydroxyl group to be a better leaving group. Subsequently, treated with methylmagnesium chloride in presence of Ni catalyst, undergoes a nucleophilic substitution reaction and forms corresponding 2,7-dimethylnapthalene (3). Formation of five membered ring across 1,8- positions of 2,7-dimethylnapthalene is achieved under high dilution conditions by dropwise addition

o of a mixture of both oxalyl chloride & 2,7-dimethylnapthalene to AlBr3 in CH2Cl2 at -16 C (4).

However, it’s hard to control the regioselectivity during this step as a ratio of 3:1 is obtained. Key to control the selectivity solely depends upon the rate of addition and firm control of temperature.

Later treatment of acenapthaquinone (4) with 3-pentanone a two-fold aldol condensation followed by retero electron demand Diel’s alder reaction gave 1,6,7,10- tetramethylfluoranthene (5) a key

intermediate to synthesize corannulene in 50% yield over two steps. Radical bromination of tetramethylfluoranthene with NBS in presence of cataytical amounts of benzoyl peroxide gave

1,6,7,10-tetrakis-(dibrommethyl)fluoranthene (6) in 80% yield. The crucial ring closure step to produce tetrabromocorannulene (7) was achieved by refluxing solution of octabromofluoranthene in aqeous dioxane with sodium hydroxide for 2 hrs. Tetrabromocorannulene (7) being sparingly soluble precipitates out of solution and was obtained in 70% yield. Debromination of tetrabromocorannulene is performed by refluxing with Zn/KI in ethanol over a period of 2 days to obtain corannulene (1) in 90% yield.

Hence, a total of 5gms of corannulene is obtained through this process starting from 50g of 2,7- dihyroxynapthalene and it takes 4 weeks of cycle time. A schematic representation of the total synthesis is outlined below (Scheme 7).

Scheme 7: Total synthesis of Corannulene

Practical amounts of corannulene (1) followed by simple synthesis of monobromocorannulene

(8) has provided an excellent ground work to further elaborate the aromatic framework of corannulene either to synthesize larger buckybowls or to build molecular architects with corannulene subunits24, 35. Scheme 8 summarizes several derivatives of corannulenes.

Scheme 8: Derivatives of Corannulene (1)

Interestingly, chlorination of corannulene with ICl gives symmetrically substituted 1,3,5,7,9- pentachlorocorannulene (9)36 as the only product, whereas chlorination under Balister conditions resulted in formation of decachlorocorannulene albeit in low yield37 (scheme 9). Several alkynyl derivattives either starting from bromocorannulene (8), tetrabromocorannulene (7), or pentachlorocorannulene (9) were synthesized employing improved Sonogashira, Neigishi coupling methods (Scheme 9)33b, 38. Therefore, rim halogenated corannulene derivatives with controlled substitution pattern provides an excellent opportunity to systematically investigate the effect of substitution over its photo-physical and electrochemical properties.

Scheme 9: Multiethynyl derivatives of corannulene (1)33b, 38

Corannulene, a C5v, bowl shaped polyaromatic hydrocarbon resembles the surface area similar to pyrene suggest that corannulene probably should display exceptional photophysical properties alike pyrene. As a contradiction to our hypothesis, it is relatively a weak fluorophore with quantum yield of Φ = 0.07Ǻ39. Fortunately, situation dramatically changes once corannulene is derivatized with ethynyl derivatives24. Bicorannlenylacetylene (10) (Scheme 8) – an example of monosubstituted corannulene derivative synthesized by Siegel’s group exhibit strong blue fluorescence with quantum yields of 0.57; more than eight times to that of parent corannulene24. However, bicorannulenylacetylene is unstable and quickly decomposes even at -16oC. Results clearly elucidate that π-conjugation can be extended between corannulene units if tethered by triple bonds and shows predominant red shift (302nm) in absorption spectrum. On the other hand, more recent reports from Siegel et.al highlight the expansion of ethnyl derivatives of disubstituted, tetrasubstituted and pentasubstituted alkynyl corannulene derivaties40.

Interesting absorption/quantum yields trends of multiethynyl corannulene derivatives were presented (fig. 8). Surprisingly, longer wavelength absorption was noticed for tetrasubstituted (11) followed by disubstituted (12) in comparison to highly symmetric pentasubstituted (13) corannulene derivatives40. Possible reasons for such anamoly could be symmetry forbidden transition states and presence of multiple non-radiative relaxation modes in ground state with higher rate of decay.

Meanwhile our group reported the synthesis/photophysical properties of a series of o, p-substituted bis(corannulenylethynyl)benzene (14) (Scheme 8)35a. The reason behind their synthesis was to examine the photophysical and thermal properties of these materials in comparison to bicorannuleneylacetylene. Surprisingly, none of these materials showed any sign of decomposition even at 300oC. As expected both ortho and para substitution showed enhanced conjugation (299,

371nm).

Figure 9: Comparison study of multiethynylphenyl derivatives of (1)

These finding raise an important question with reference to the nature of linker and corresponding conjugating site. Unlike benzene where it is an established fact that if groups placed in ortho and para are always in conjugation whereas in meta they are not. A detailed investigation related to site specificity on corannulene’s rim CH have to be undertaken in order to understand which substitution resembles more like o/p and meta. The data generated from this study would certainly help in designing materials with extreme robust and thermally stable blue LEDs.

References

1) Aziz, H.; Popovic, Z. D. Chem. Mater.2004, 16, 4522-4532.

2) a) Pope, M.; Kallmann, H. P.; Magnantt, P. J. Chem. Phys. 1963, 38, 2042, b) Helfrich, W.;

Schneider, G. Phys. Rev. Lett. 1965, 14, 229-231, c) Vincett, P.S.; Barlow, W. A.; Hann, R. A.;

Roberts, C. G. Thin Solid Films 1982, 94, 171-183.

3) Tang, C. W.; Van-Slyke, S. A. Appl. Phys. Lett. 1987, 51, 913-915.

4) Cao, Y; Parker, I. D.; Yu, G.; Zhang, C.; Heeger, A. J Nature 1999, 397, 414-

5) a) Tang, C. W.; Van-Slyke, S.A.; Chen, C. H. J. Appl. Phys. 1989, 65, 3610-3616, b) Baldo, M. A.;

Thompson, M. E.; Forrest, S. R. Nature 2000, 403, 750-753.

6) Schon, J. H.; Kloc, Ch.; Dodabalapur, A.; Batlogg, B. Science 2000, 289, 599

7) Schon, J. H.; Meng, H.; Bao, Z. Nature 2001, 413, 713

8) Huynh, W. U.; Dittmer, J. J.;Alivisatos, A. P. Science 2002, 295, 2425

9) a) Display Search - Press Relase 2009, b) http://digidelve.com/tech/ageless-oled

http://en.wikipedia.org/wiki/Organic_electronics#cite_note-6

10) Kulkarni, A. P.; Jenekhe, S. A. Macromolecules 2003, 36, 5285-5296.

11) McElvain, J.; Antoniadis, H.; Hueschen, M. R.; Miller, J. N.; Roitman, D. M.; Sheats, J. R.; Moon,

R. L J. Appl. Phys. 1996, 80, 6002-6007.

12) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.; Friend, R. H.;

Burns, P. L.; Holmes, A. B Nature 1990, 347, 539.

13) Andersson, M. R.; Yu, G.; Heeger, A. J. Synth. Met., 1997, 85, 1275

14) a) Schwartz, B. J.; Hide, F.; Andersson, M. R.; Heeger, A. J. Chem. Phys. Lett., 1997, 265, 327, b)

Salbeck, J.; Bunsenges, B. Phys. Chem., 1996, 100, 1666.

15) a) Chuah, B. S.; Hwang, D. H.; Kim, S. T.; Moratti, S. C.; Holmes, A. B.; Mello, J. C.; Friend, R.

H. Synth. Met., 1997, 91, 279, b) Kim, S. T.; Hwang, D. H.; Li, X. C.; Gruner, J.; Friend, R. H.;

Holmes, A. B.; Shim, H. K. Adv. Mater., 1996, 8, 979.

16) OIDA OLED’s Update 2002. http://www.oida.org

17) Clar, E.; Boggiano, B. J. Chem. Soc. 1957, 2681-2689.

18) a) Subramanian, S.; Park, S. K.; Parkin, S. R.; Podzorov, V.; Jackson, T. N.; Anthony, J. E. J. Am.

Chem. Soc. 2008, 130, 2706-2707, b) Kim, Y. H.; Shin, D. C.; Kim, S. H.; Ko, C. H.; Yu, H. S.;

Chae, Y. S.; Kwon, S. K. Adv. Mater. 2001, 13, 1690-1693.

19) Kim, Y.; Kwon, S.; Yoo, D.; Rubner, M. F.; Wrighton, M. S. Chem. Mater. 1997, 9, 2699-2701.

20) Tanaka, T.; Komatsu, K. J. Chem. Soc. Perkin Trans. 1, 1999, 1671-1675.

21) Balasubramanian, K.; Burghard, M. Small, 2005, 1, 180-192.

22) Yanney, M.; Fronczek, F. R.; Sygula, A. Org. Lett. 2012, 14, 4942-4945.

23) Lovas, F. J.; McMahon, R. J.; Grabow, J. U.; Schnell, M.; Mack, J.; Scott, L. T.; Kuczkowski, R. L.

J. Am. Chem. Soc. 2005, 12, 4345-4349.

24) Jones, C. S.; Elliott, E.; Siegel, J. S. Synlett 2004, 1, 187-191.

25) a) Barth, W. E.; Lawton, R. G. J. Am. Chem. Soc. 1966, 88, 380-381, b) Barth, W. E.; Lawton, R. G.

J. Am. Chem. Soc. 1971, 93, 1730-1745

26) Davy, R.; Iskander, M. N.; Reiss, J. A. Tetradedron Lett. 1978, 4085-4088.

27) Brown, R. F. C.; Harrington, K. J.; McMullen, G. L. J. Chem. Soc. Chem. Commun. 1974, 123-124.

28) Scott, L. T.; Hashemi, M. M.; Meyer, D. T.; Warren, H. B. J. Am. Chem. Soc. 1991, 113, 7082-7084.

29) Scott, L. T.; Cheng, P. C.; Hashemi, M. M.; Bratcher, M. S.; Meyer, D. T.; Warren, H. B. J. Am.

Chem. Soc. 1997, 119, 10963-10968.

30) Seiders, T. J.; Baldridge, K. K.; Siegel, J. S. J. Am. Chem. Soc. 1996, 118, 2754-2755.

31) Sygula, A.; Rabideau, P. W. J. Am. Chem. Soc. 1998, 120, 12666-12667.

32) Sygula, A.; Rabideau, P. W. J. Am. Chem. Soc. 1999, 121, 7800-7803.

33) a) Sygula, A.; Rabideau, P. W. J. Am. Chem. Soc. 2000, 122, 6323-6324, b) Sygula, A.; Xu, G.;

Marcinow, Z.; Rabideau, P. W. Tetrahedron 2001, 57, 3637-3644.

34) Butterfield, A. M.; Gilomen, B.; Siegel, J. S. Org. Process Res. Dev. 2012, 16, 664-676.

35) a) Mack, J.; Vogel, P.; Jones, D.; Kaval, N.; Sutton, A. Org. Biomol. Chem., 2007, 5, 2448-2452, b)

Sygula, A.; Sygula, R.; Kobryn, L. Org. Lett., 2008, 10, 3927-3929.

36) Scott, L. T. Pure Appl. Chem. 1996, 68, 291-300.

37) Huang, R.; Huang, W.; Wang, Y.; Tang, Z.; Zheng, . J. Am. Chem. Soc. 1997, 119, 5954-5955.

38) a) Sieder, J. T.; Elliott, E. L.; Grube, H.G.; Siegel, J. S. J. Am. Chem. Soc. 1999, 121, 7804-7813, b)

Gunther, H. G.; Elliot, E. L.; Steffens, R. J.; Jones, C. S.; Baldridge, K. K.; Siegel, J. S. Org. Lett.,

2003, 5, 713-716, c) Steinberg, B. D.; Jackson, E. A.; Filatov, A. S.; Wakamiya, A.; Petrukhina, M.

A.; Scott, L. T. J. Am. Chem. Soc. 2009, 131, 10537-10545

39) Rabideau, P. W.; Abdourazak, A. H.; Sygula, R.; Warner, I. M. J. Fluoresc. 1997, 7, 231.

40) Wu, Y. T.; Bandera, D.; Maag, R.; Linden, A.; Baldridge, K. K.; Siegel, J. S. J. Am. Chem. Soc. 2008,

130, 10729-10739.

Understanding Conjugation through Diethynylcorannulene series – Synthesis,

Structures and Properties

Practical amounts of corannulene and controlled substitution patterns of corresponding alkenyl functionality through bromo/tetrabromo/pentachloro corannulene derivatives (8, 7, and 9) offer us a unique opportunity to test the theory of conjugation. Such regioselective patterns could be examined for conjugation by tethering the open end of an alkyne with chromophores like: phenyl, anthrancene, corannulene and other corannulene based materials (fig.10).

Figure 10: Target compounds to test conjugation with different chromophores

Examining their absorption/emission/quantum yields data could provide useful information in designing corannulene based blue emitting materials with high quantum efficiency and stability.

Besides, selection of corannulene itself as chromophore will help us examine two things: a)

absorption /fluorescence, quantum yield data will provide information regarding corannulene’s role in extending conjugation, b) corannulene displays electrochromism; hence would increase the total number of possible reduction states unattainable previously. In case of 15, a benzene unit would promote additional conjugation which may lead the absorption into mid-visible region.

Fortunately, besides Siegel’s disubstitution pattern of 1,6-diethnylcorannulene1 (12) our group has discovered two novel substitution patterns: 1,8 and 1,5 about the corannulene rim (figure 11). Unlike ethynylcorannulene or bicorannlenylacetylene (10) both 1,8 (16) and 1,5-dialkynyl (17) derivatives are thermally stable and did not show any signs of decomposition even after months of their synthesis.

Among several possibilities for their stability, computational calculations performed at B3LYP-6-

31G* predicts that in case of disusbstituion the electron distribution is throughout the corannulene systems whereas in case of monosubstitution where it is purely localized on a single rim carbon.

Additionally, disubstitution patterns allows for more resonance structures when compared to monosubstitution.

Figure 11: Diethynylcorannulene derivatives

Synthesis of 1,8 & 1,5 – diethynylcorannulene:

Synthesis of both isomers 16 & 17 follows similar synthetic routes. Friedel-Craft acylation provides access to two isomers 1,8 and 1,5-diacetyl corannulene. Seperation of isomers was accomplished by combiflash column chromatography using silica gel prepacked columns and eluting

the material initially with pure dichloromethane and later applying a gradient 99:1 CH2Cl2: EtOAc to obtain 73% total yield with ratio of 1.6:1.0 respectively. 1H NMR together with computation studies at B3LYP/6-31G* helped in characterizing the isomers. Later bischlorovinyl corannulene was obtained by refluxing with 1,2-phenylene phosphotrichloride in anhydrous dichloroethane for 18 hours to obtain 95% yield. However, dehydrohalogenation using freshly generated lithium diisopropylamide (LDA) resulted in meager yields (scheme 10).

Scheme 10: Synthesis of 1,8-diethynylcorannulene (16)

Hence we decided to explore this step in order to enhance yields. Possibility of nBuLi can be

ruled out as it often results in dimers, instead bases such as: NaNH2, NaH, LiTMP and LiHMDS whose pKa aligns with LDA were chosen. Our intent was to examine how the level of base’s bulkiness affects the dehydrohalogenation step. THF and ether were chosen as our solvent medium.

We varied the reaction conditions ranging from -78oC to reflux with different proportions of base amount. Results clearly indicate the ineffectiveness of all bases irrespective of their level of bulkiness. Later the role of chelating agent TMEDA was questioned. Table 1 elucidates various sets of conditions employed to perform dehydrohalogenation.

Table 1: Optimization test reactions

Entry Reaction Conditions Result

1 LDA/-78oC/THF/10eq/18hr 10%

2 LiHMDS/-78oC/THF/10eq/18hr 10%

3 LiHMDS/0oC/THF/10eq/18hr 10%

o 4 NaNH2/-78 C/THF/10eq/18hr No reaction

o 5 NaNH2/0 C/THF/10eq/18hr No reaction

o 6 NaNH2/25 C/THF/10eq/18hr Recovered starting material

o 7 NaNH2/40 C/Ether/10eq/18hr Recovered starting material

8 NaH/THF/25oC/10eq/18hr Recovered starting material

9 NaH/ball mill/10eq/16hr Recovered starting material

10 LiTMP/-78oC/THF/10eq/18hr <10% product obtained

11 LiTMP/0oC/TMEDA/THF/ <10% product obtained 10eq/18hr

12 LiTMP/25oC/THF/10eq/18hr <10% product obtained

13 LiTMP/40oC/ether/10eq/18hr <10% product obtained

14 LiTMP/-78oC/THF/100eq/18hr Decomposition of starting material 15 TBAF/100oC/DMF/10eq/24hr 100% conversion by NMR 10% isolated yield 16 TBAF/75oC/DMF/10eq/1hr 100% conversion by NMR 30% isolated yield 17 TBAF/65oC/DMF/10eq/30 min 100% conversion by NMR 30-50% isolated yield

18 LDA/n-BuLi(excess)/-78oC/THF/4hr 80% isolated yield

Entry (11) clearly shows that there is no such effect. Next in line was to test the efficacy of ball milling over solution phase. Ball milling the material with NaH in a solvent less environment also led to disappointment (entry 9). Meanwhile, Mori et.al published a study emphasing the importance of

TBAF in synthesis of alkynes from corresponding vinylbromides2. Mild reaction conditions with more generalized approach using common reagents attracted our attention. To our surprise as detailed in the publication, trial reaction with dichlorovinylcorannulene showed complete disappearance of starting material and generated desired dialkyne within the first half hour of reaction. However, the expected product was obtained in relatively moderate yields of 30-50%.

Attempts to run the reaction on large scale often resulted in meager yields. On multiple occasions extraction proved to be challenging. Washing with water resulted in insoluble material which even after repeated extractions with dichloromethane failed to appreciably increase the amount of final compound. NMR analysis of insoluble material showed no peaks of interest. Change of extracting solvent to diethyl ether also resulted in similar outcome. A possible reason for low yields could be competing reaction between formation of final compound and polymerization of corresponding alkynes once formed.

Such limitations of TBAF induced dehydrohalogenation demanded us to search for a better alternative, and this led us to question quantitative generation of LDA -78oC, as several reports advice LDA to be produced at -20oC instead. Moreover, the true concentration of nBuLi and water content in diisopropylamine varies greatly depending upon the handling technique of the researcher.

These factors directed us to add excess of n-BuLi and monitor the progress of the reaction by

T.L.C. Surprisingly, the reaction is completed within 4hrs and isolated yields was 80% (entry 18), free from laborious extractions as seen in case of TBAF. Satisfied by the outcome, we diverted our

attention towards synthesizing chromophore (15) which will tether on the terminal ends of dialkyne

16 & 17.

(4-bromophenyl)corannuleneacetylene synthesis (15):

Monobromination of corannulene was achieved in quantitative yield by treatment with 3 eqs of

IBr in dry dichloroethane. Subsequent treatment with excess of trimethylsilylacetylene in presence

of CuI/PdCl2(PPh3)2/TEA in dry THF gave the desired product in 90% yield. Desilylation was achieved within 2 hrs of stirring the material with 3 eqs of K2CO3 in 1:1 ratio of methanol:DCM.

Generated alkyne was quickly reacted with excess of 1,4-diiodobenzene in presence of

CuI/PdCl2(PPh3)2/TEA in dry THF to obtain (4-Bromophenyl)corannuleneacetylene (15). To our surprise instead of 15, we obtained 14 as major product with high amounts of unreacted 1,4- diiodobenzene. Instead of using large excess of ethynylcorannulene which cannot be recovered due to stability reasons, we preferred halogen exchange following protocol published earlier by Sygula et.al3 to transform bromocorannulene (8) to more reactive Iodocorannulene (18). Refluxing (8) with

CuI in DMF for 30hrs under inert conditions gave the desired compound as yellowish solid in 81%

yield. Applying standard Sonogashira coupling conditions (PdCl2(PPh3)2/CuI/TEA in THF), 18 was successfully coupled with 4-bromoethynylbenzene (19) to deliver target compound (15) as a yellow solid in 50% isolated yield. Successful synthesis of 15 was possible by simply switching the reactivity of coupling partners. Moreover, this route offers easy recovery of unreacted iodocorannulene which is practically difficult in case of ethynylcorannulene for stability reasons (scheme 11).

Scheme 11: Different approach towards synthesis of 15

Next in line of synthesis was to couple different chromophores listed in fig.10 with 16 & 17. Target molecules synthesized will allowed us to understand how the nature of chromophores alter the bulk photophysical properties of 1 when conjugated regioselectively at 1,8 and 1,5 positions of corannulene outer rim.

Synthesis:

Coupling of chromophores with 16 & 17 follows similar synthetic methodology. 16 being symmetrical, analysis of crude reaction mixture, and characterization by NMR would be much simpler to understand. Keeping these key points into account, all coupling strategies, test reaction/optimization studies were first performed on 16. Once the coupling route delivered desirable yields, synthesis of corresponding 17 derivatives were performed. Hence, in following chapters we would only provide detailed studies with respect to 16 and its derivatives.

Using slight excess of iodobenzene with respect to 16 in presence of PdCl2(PPh3)2/CuI

o (1:1)/Et3N/THF at 40 C for 3 hrs in absence of light under inert conditions delivered the desired compound as yellow solid in 60% yield. 1H NMR analysis of 20 shows 0.2 δ downfield chemical shift for a corannulene proton next to an alkyne functionality. Applying similar synthetic methodology we also obtained 21 as shown in scheme 12.

Scheme 12: Synthesis of 20 and 21.

On the other hand, coupling of 9-bromoanthracene with 16 led to disappointment. Test reactions indicated recovery of large amount of unreacted 9-bromoanthrancene. Possible reasons for this failure could be the less reactive “bromine” as coupling partner. To circumvent this problem, 30

halogen swap of 9-bromoanthracene to 9-iodoanthrancene was attempted. Lithiation with n-BuLi

(1.05 eq) followed by quenching with dropwise addition of iodine solution in THF gave the desired

9-iodoanthrance in 90% yield. Later, refluxing 9-iodoanthracene with 16 & 17 in THF for 3hrs using above mentioned catalytic condition delivered the target compound in moderate yields (20%) as shown in scheme 13.

Scheme 13: Synthesis of 22 & 23.

Next in the series was to couple corannulene with 16 and 17. Test reaction of coupling iodocorannulene with 16 & 17 was attempted using the Sonogashira methodology listed above at

40oC for overnight. Later, crude reaction mixture was acidified with 10% HCl and extracted with dichloromethane. Combiflash column chromotagraphy was performed using a gradient of hexane and dicholoromethane. Apart from unreacted excess iodocorannulene, two compounds based on their U.V absorption were isolated. After full analysis of NMR and mass spectroscopy we were only able to fully characterize the first eluted compound. Surprisingly, 1H NMR showed slightly different splitting patterns when compared to (20). Four sets of doublets between 8.3 – 7.9δ representing protons 3,4,5,6 and two singlet at 8.2, 8.1δ corresponding to 2,7 protons. Additionally,

cluster of 18 protons at 7.8δ generated from branched corannulene on either side of alkyne were noticed. Encouraged by this result, sample was sent for mass analysis - MALDI-TOF. As expected, both 1H NMR and MALDI confirmed that target compound 24 has been synthesized but needs further purification. On the other hand, impurities were also observed in case of 25 (scheme 14).

Scheme 14: Synthesis of 24 & 25.

Due to low availability of both coupled product 24 & 25 and moreover it being a test reaction we tried to reproduce our reaction on a larger scale but unfortunately our attempts to synthesize the target compound 24 and 25 delivered complex mixture with unusually high mass number when analyzed by MALDI-TOF. Neither analysis of both crude reaction mixture nor after purification by column chromatography by 1H NMR showed any previously seen splitting pattern. Any attempt to couple would results in complete recovery of iodocorannulene with complete consumption of (16).

Hence, to resolve this issue we focused on altering catalyst loading and its mode of introduction to help Pd(0) catalyst to stay active for longer periods of time.

Catalyst loading was increased from 20 mol% to 30 mol% which did not change the outcome.

Later we incrementally added the catalyst in two portions over 2 hr period in order to keep catalyst active throughout the course of reaction. However, this strategy also failed to deliver the desired product 24. Next, instead of adding catalyst as a solid, we made a solution in THF and added dropwise. Unfortunately, the outcome was similar. Tracking the reaction progress by t.l.c suggested complete disappearance of 16 within the first 1 hr with large amount of 18 still unreacted.

Figure 12: Mechanistic pathway of Sonogashira coupling reaction

Complete recovery of (18) with disappearance of (16) suggests that may be “cu-acetylides” – step

F (fig. 12) formation is much faster and once formed gets consumed way before oxidative insertion of palladium with iodocorannulene – step B (fig. 12). Hence, efficacy of this hypothesis was put to test.

Instead of introducing 16 as solid in one pot, we made a solution in THF added dropwise to the reaction mixture over a period of 1 hr. But our attempt all led to disappointment. Next, we hypothesized that may be the active site over the catalyst is overcrowded and is unable to perform

the desired oxidative coupling – step B. Hence, we decided to perform the reaction at elevated temperatures and keeping the catalyst loading at 30 mol%. Varying the temperature from 40 to 65oC and even refluxing the reaction for 2 days in THF did not deliver 24. Meanwhile, Sharp et.al4 reported crystal structures of stable Pt complexes of corannulene by oxidative insertion starting from bromocorannulene.

This report gave a different prospective to understand the failure of our coupling reaction. May be the oxidative insertion of Pd with iodocorannulene happens quickly and leads to a more stable complex which may resists coupling with dialkyn (16). To examine this possibility, we synthesized

Pd complex of iodocorannulene by stirring Pd(PPh3)4 with iodocorannulene in THF at room temperature. Evaporation of solvent, followed by flash chromatography of the reaction mixture gave the desired compound as reddish brown in color with 70% yield.

Later newly synthesized Pd-complex was used with dialkyn 16, both in presence / absence of

additional 10 mol% PdCl2(PPh3)4 cataylst. Unfortunately in both cases we were unable to recover neither dialkyne (16) nor synthesize desired product (24). Disappointed with our attempts to resynthesize 24 & 25, we revisited the conditions required for synthesis of 15, 18, and 20.

Purity of Iodocorannulene (18):

As stated earlier, stoichiometric amount of CuI is required to perform halogen exchange hence even after workup/chromatography there lies a possibility of Cu being present with the product 18.

As “Cu” transforms alkyne to more reactive Cu-acetylides and if excess of such reactive metal is present, may prove to be detrimental during Sonogashira coupling and may well this could be the underlying cause for our failed attempts to produce 24 & 25. To examine this possibility, we performed a test reaction in presence/absence of catalytic amounts of CuI to couple 18 with 19.

As expected, we obtained the desired compound in 91% yield in presence of CuI and low yields of

15% was observed in absence of CuI. Hence, speculation surrounding excess of “Cu” with 18 can be easily ruled out (scheme 15).

Purity of diethynylcorannulene (16 & 17):

To test the purity of diethynylcorannulene, we set out a test reaction under standard Sonogashira reaction conditions in the presence of iodobenzene as coupling partner. The desired compound was obtained in excellent yields (scheme 15).

Scheme 15: Revisiting the conditions for the synthesis of 18 & 20, to understand the failures related towards synthesis of 24.

Trial reactions intended to check purity of coupling partners and possible presence of excess

“Cu” associated with iodocorannulene (18) proved to be negative. Apart from using PdCl2(PPh3)2 we also attempt to use other “Pd” sources as depicted in table 2.

Table 2: Different “Pd” sources used to synthesize 24.

Entry Reaction conditions Result

1 Pd(PPh3)4/CuI (1:1) – 20 mol% each, TEA 18 recovered

2 Pd(PPh3)4/CuI (0.5:1) – 10 mol% Pd, TEA 18 recovered

3 Pd(PhCN)2Cl2 / [(t-Bu)3PH] BF4 (1:2) - 20 mol% Pd 18 recovered diisopropylamine

4 Pd(PPh3)4/CuI (1:1) – 25 mol% Pd, piperidine 18 recovered

5 Pd(PPh3)4/CuI (1:2) – 10 mol% Pd, n-BuNH2 18 recovered

Hence, the most likely reason for failures may be steric crowding at the catalyst center and failure to undergo transmetallation step.

Next in the series was to couple 16 with 15. We successfully synthesized the desired compound

o 26 using PdCl2(PPh3)4/CuI (1:1) ratio in presence of TEA as base in THF at 65 C as shown in scheme 16. 1H NMR analysis after column chromatography showed a cluster of peaks from 8.2 -7.8

δ as expected. However, further evidence was provided from MALDI-TOF. Unfortunately, our attempts to reproduce the reaction conditions on a larger scale met with failures.

Scheme 16: Synthesis of 26.

Once extending the conjugation in two directions was complete, we diverted our attention to apply similar strategy to extend the corannulene’s π-aromatic framework in multiple directions. For this we selected tetrabromocorannulene – an intermediate in corannulene’s synthesis as our building

block. Under optimized conditions of Sonogashira coupling (PdCl2(PPh3)2/CuI

(1:1)/TEA/THF/40oC), (7) was coupled with excess of trimethylsilylacetylene to obtain corresponding coupled product (28). Desilylation with potassium carbonate in 1:1 methanol:dichloromethane followed by coupling with corresponding aryliodides delivered the desired target molecules 29 and 30. A complete synthetic strategy is detailed in scheme 17 below.

However, trial attempts to couple (27) with either (1) or (15) did not lead to any encouraging outcome. Possible reasons could be steric congestion in the target compounds.

Scheme 17: Extending conjugation in multiple directions

Results and Discussion:

Corannulene shows two prominent absorption bands centered at 254nm and 290 nm. However, corannulene does not absorb in the visible part of the electromagnetic spectrum. One step ahead is ethynylcorannulene reported by Siegel et.al5 which shows two prominent peaks centered at 261nm and 295 nm. Hence introduction of acetylene units on corannulene’s rim shifts the absorption by 5 nm. This suggests that the photophysical properties of corannulene can be altered if functionalized by alkynes. However, the change in absorption/fluorescence patterns could be far-reaching if we

know which disubstitution pattern on corannulene’s outer rim would be more analogus to an ortho/para vs. meta substitution pattern on a benzene ring. To study such effect we regioselectively functionalized 1,8 and 1,5 positions over corannulene’s outer rim and attached different chromophores to study its photophysical properties

0.8

0.7

0.6

0.5

0.4

Absorption 0.3

0.2

0.1

0 260 360 460 Wavelength (nm) Figure 13: Absorption spectra of 1,8/1,5-diethynylcorannulene series

1 0.9 0.8

0.7 0.6 0.5

Absorbance 0.4 0.3 0.2 0.1 0 260 360 460

Wavelength (nm)

Figure 14: Absorption spectra of 24, 25, and 26.

Upon synthesis of target molecules: 20, 21, 22, 23, 24, 25, 26, 28, and 29, a 1x10-5 M solution in dichloromethane was prepared to study the corresponding photophysical properties. Figure 13 elucidates the absorption spectra of synthesized corannulene derivatives.

In comparison to parent corannulene and ethynylcorannulene; both 16 and 17 shows considerable red shift with prominent absorption band centered at 269nm and 306 nm. A total of

16 nm red shifts is observed from parent corannulene. Whereas, tethering a phenyl unit at both ends of terminal bonds (20, 21) not only increase the molecular extinction coefficient but also the absorption trails well into visible region. In case of 20 we observed two absorption peaks centered at 290 nm and 317 nm with a shoulder at 360nm trailing into visible region of electromagnetic spectrum. On the other hand, 21 exhibit a broad peak with highest absorption at 307 nm and a shoulder at 360nm trailing into visible region. A similar pattern of broad absorption peak is also seen in case of 1,6-diethynylcorannulene reported by Siegel et.al.1 Subsequently, replacing phenyl unit with corannulene shows a similar pattern of absorption (fig. 14). In case of compound 24, two

major absorption bands were observed at 296nm and 317 nm with a weak shoulder at 380nm which trails well into visible region. On the other hand, similar to 21, 25 exhibits a stretch of broad peak with highest absorption at 290 nm with a long tail passing into visible region. Comparison of 20, 21 with 24, 25 shows overlapping results, which suggest that may be both corannulene’s tethered to triple bonds may not be participating to full extent, a more detailed study of their orbital will follow later. On the other hand, molecule 26 shows low absorption, with primary transition from parent corannulene shifted from 290 nm to 310 nm with multiple weak shoulders at 370 nm and 400 nm.

Anthracene does not absorb in visible region but when coupled with 16 and 17 as shown in fig.

13 (22 and 23), absorbs well into visible region. Absorptions from 22 and 23 overlap, exhibits primary absorption pertaining to parent corannulene shifted from 290 nm to 308 nm with two major transitions at 425 nm and 455 nm. A total of 165 nm red shift is detected in this case. Hence, from the study of UV-Vis absorption pertaining to 20, 21, 22, 23, 24, 25 and 26 we do not see a difference between 1,8 and 1,5-disubstituted pattern. Moreover, absorption pattern and extent of bathochromic shift reported for 1,6-diethynylcorannulene also shows overlapping results with our study (20 and 21). Hence, more experiments are needed to determine which disubstitution pattern resembles more like ortho/para and meta.

Next in series was to examine absorption of multiethnyl derivatives of corannulene: 28, 29. The longer wavelength transition from parent corannulene observed at 290nm is red shifted to 330 nm for 28 and 314 nm in case of 29. Additionally, long trail of absorption leads well into visible region

(fig. 15).

To gain further insight into the absorption spectra of molecules 20, 21, 22, 23, 24, 25, and 26, we performed density functional theory (DFT) and time-dependent density functional theory (TD-

DFT) calculations with B3LYP level of theory and 6-31G* as basis set. B3LYP level of theory with

6-31G* basis set accurately reproduces bond length, bond angles and dihedral angels for corannulene6, hence was used for calculation purposes.

0.8

0.6

0.4 Absorption 0.2

0 260 360 460 Wavelength (nm)

Figure 15: Absorption from multiethynyl substituted corannulene (28 and 29)

Table 3: Calculated wavelength with TD-DFT in comparison with experimental results

Molecule Experimental (nm) Calculated (nm) f

16 308 377 0.0063

17 305 379 0.0079

20 367, 317 410, 376 0.0629,0.3765

21 364, 304 411, 375 0.0548, 0.0446

22 452, 427 487, 459 0.4543, 0.4346

23 452, 427 494, 488 0.7456,0.0739

Figure 16: B3LYP/6-31G* optimized structures of 20, 21, 22, 23, 24, and 25

B3LYP/6-31G* optimized structures for 20, 21, 22, 23, 24, 25 and 26 shows a slight twist with respect to core corannulene. The twist angle measures approx. less than 2o with respect to central corannulene unit. This twist angle can be visually seen in fig. 16. Next we performed TD-DFT calculations to estimate which excitation is responsible for a particular transition seen in UV-Vis absorption (fig. 17). Table 3 depicts a comparison between calculated and experimental absorption values.

Figure 17: HOMO to LUMO and HOMO-1 to LUMO+1 transition for 20, 21, 22 and 23.

Longer wavelength absorption for compounds 20 and 21 (367nm, 364 nm) is generated from corresponding HOMO to LUMO, whereas a well resolved distinct absorption at 317 nm in case of

20 comes from HOMO-1 to LUMO transition. On the other hand HOMO-1 to LUMO+1

transition (290nm for 20 and 304 nm for 21) is the same orbital transition coming from parent corannulene’s HOMO to LUMO transition (290 nm).

Interesting results are observed in case of both 23 and 24. Since anthrancene absorbs at longer wavelength in comparison to corannulene, hence gets excited first. This transition is observed as a

HOMO to LUMO at 452 nm, whereas slight shorter wavelength absorption is seen in case of

HOMO-1 to LUMO+1 at 427 nm. On a contrary note, 9,10-bis(corannulenlethynyl)anthracene7 a system where conjugation is through anthracene bridge is recently synthesized in our lab.

B3LYP/6-31G* calculated orbital transitions indicate a HOMO to LUMO transition completely localized on anthracene unit whereas HOMO-1 to LUMO+1 transition are localized on corannulene unit. Visual interpretation of such transition difference is clearly seen when this molecule is laser excited at longer wavelength (488 nm) exhibits “green” color generated from anthrancene whereas at shorter wavelength (405 nm) shows blue emission arising from corannulene unit. This phenomenon of dual emission is not seen in our case as the LUMO and LUMO+1orbitals are delocalized throughout the molecule. As a result in laser excitation study shows a blend of green and blue color independent of excitation wavelength (fig. 22).

Figure 18: HOMO to LUMO and HOMO-1 to LUMO transitions for 24 and 25.

On the other hand, longer wavelength absorption observed in fig. 14 for both 24 and 25 is due to its HOMO to LUMO transition. Orbtial overlap shows an extended conjugation involving one of two corannulene unit in case of 24 (fig. 18).

Strong absorption data from corannulene based materials 16, 17, 20, 21, 22, 23, 24, 25 and 26 indicate that its corresponding fluorescence should exhibit predominant enhancement in its emission when compared to parent corannulene.

Corannulene shows a broad, weak blue emission centered at 430 nm. All molecules show considerable enhancement in fluorescence intensity in comparison with parent corannulene. All molecules were excited at 300 and 400 nm. Wavelength of excitation was choosen based on its absorption data as presented in fig.13. Compound 16 and 17 show a slight shift in their fluorescence emission from 430 to 434 nm (fig. 19).

400

300

200 Intensity

100

0 380 480 580 680 Wavelength (nm)

Figure 19: Fluorescence spectra with excitation at 300 nm

Corannulene exhibits a rapid bowl to bowl movement hence exhibits a continuous emission spectrum. However, in a locked configuration, the movement decelerates and results in appearance

of well resolved peaks8. This phenomenon is clearly depicted in case of 20 and 21 and surprisingly disappears in case of 22 and 23. A shift of 20 nm is observed in case of 20 and 21, whereas a difference of 60 nm is noticed for 22 and 23 from parent corannulene.

400

350

300

250

200

Intensity 150

100

0 410 510 610 Wavelength (nm)

Figure 20: Fluorescence spectra (excitation at 400 nm)

Corannulene does not exhibit emission at 400 nm region. A similar phenomenon is seen in case of 16 and 17 whose emission also appears to be feeble. However, phenylconjugated 20 and 21 does show a weak emission when excited at 400 nm. This is expected as both 20 and 21 have weaker absorption near 400 nm as per its absorption spectra (fig. 13). As expected both 23 and 24 exhibit strong intense fluorescence when excited at 400 nm.

To verify if we are performing fluorescence studies of each target molecule at its maximum intensity, we preliminarily examined their zero order emissions. Subsequently, excitation wavelengths were selected solely based on their highest emission and its absorption spectra. For a more general comparison of all target compounds we opted to compare the fluorescence at 300 and

400 nm.

160

120

Zero order for 17

at 306 nm for 17 80 at 339 nm for 17

Intensity(a.u.) Zero order for 16 40 at 306 nm for 16

at 339 nm for 16

0 260 360 460 560 Wavelength (nm) Figure 21: Excitation of 16 & 17 at different wavelengths based on its zero order emission

900

800

700 Zero order for 21 at 306 nm for 21 600

at 302 nm for 21 at 356 nm for 21 500 at 400 nm for 21 Zero order for 20 400

at 306 nm for 20 Intensity (a. u) 300 at 289 nm for 20 at 317 nm for 20 200 at 353 nm for 20 at 400 nm for 20 100

0 260 360 460 Wavelength ( nm)

Figure 22: Excitation of 20 and 21 at different wavelengths based on its zero order emission data

As shown in figure 21 and 22, zero order emission indicate that there is one major excitation peak which fruitfully transforms to corresponding observed fluorescence. This excitation corresponds to parent corannulene’s HOMO to LUMO transition at 289 nm. Increasing the conjugation certainly enhances the fluorescence intensity however, observed emission results are independent of excitation wavelengths obeying Kasha’s rule.

To examine the ability of these molecules to act as blue emitters, we excited them at 325 nm and

405nm (23, 24). Corannulene does not show any emission at 325 nm, however molecules from 16 to 21 shows strong blue emission. On the other hand, 22 and 23 shows a blend of blue and green color which is well expected due to effective conjugation and intermixing of orbitals. Out of curiosity we also examined the laser excitation at 405 nm (fig.23, 25). Interestingly, intensity of emission was further strengthened.

Figure 23: Laser excitation at 325 nm.

To rule out the possibility that the photophysical properties for compounds 22 and 23 are coming purely from anthrancene and not in conjunction with corannulene’s aromatic framework, we collected the absorption, fluorescence and laser excitation data of naked anthracene.

Anthrancene shows four absorption bands at 328, 343, 359 and 379 nm. It does not absorb in the visible region of electromagnetic spectrum. When excited at 300 nm shows four emission bands at

381, 402, 425 and 448 nm. No characteristic color was associated when laser excited at 405 nm as shown in figure 23.

Figure 24: Fluorescence spectra of anthrancene along with laser excitation at 405 nm

Figure 25: Laser excitation at 325 & 405 nm.

Conclusions:

In order to understand conjugation through corannulene’s π- aromatic framework and subsequently identify specific disubstitution sites which are more like ortho/para or meta alike benzene we performed a study by regioselectively functionalized outer rim of corannulene with ethynylbonds placed at 1,8 and 1,5 position. Upon functionalization we tethered the terminal end of ethynyl bonds with different chromophores (fig.10) including corannulene and its derivatives (15).

Molecules synthesized alike ethynylcorannulene or bicorannlenylacetylene (10) exhibit remarkable stability, did not show any signs of decomposition even months after their synthesis. Greatly improved yields for 16 and 17 were obtained using slight excess of n-BuLi, as a result 10% yield was improved to 80%. Optimizing Sygula et.al method led to discovery of iodocorannulene a better coupling partern when compared to its bromo analogue, was used several times at different occasion to synthesize various derivatives of corannulene. Test reaction pertaining to synthesis of 24, 25 and

26 showed encouraging results with reference to its synthesis, unfortunately led to disappointed even after several trials to duplicate the earlier used test reaction conditions. Attempts with different palladium sources/ligands resulted in failures.

Absorption spectra of 1,8/1,5-diethnynylcorannulene series substituted with different chromophores was studied and was determined that diethynyl units (16, 17) led to an overall red shift of , 17 nm, whereas tethering phenyl units at the open end of ethynyl units brings about a red shift of 75 nm. (20, 21). Substituting phenyl with anthrancene (22, 23) brings about a red shift of

164 nm with absorption trailing well into visible region. Additionally, it has been shown that all molecules exhibit an intense blue emission when excited with laser at 325 nm. Surprisingly, compounds 22 and 23 showed a intense blend of blue and green color when excited with laser at

405 nm.

TD-DFT calculations at B3LYP level of theory and using 6-31G* as basis set shows an over estimation of wavelength for transitions pertaining to HOMO to LUMO and HOMO-1 to

LUMO+1 as such behavior is commonly seen in highly conjugated system.

Molecules synthesized do not show any form of degradation even months after their synthesis.

Moreover, this study of diethynylcorannulene series do not show a conclusive difference between

1,8 and 1,5 positions. After examination of their photophysical properties both compound show similar behavior, hence more trial reactions are needed to identify different sites over outer rim of corannulene’s which can conclusively show a significant difference in their photophysical properties.

References

1) Wu, Y. T.; Bandera, D.; Maag, R.; Linden, A.; Baldridge, K. K.; Siegel, J. S. J. Am. Chem. Soc.

2008, 130, 10729-10739.

2) Okutani, M.; Mori, Y J. Org. Chem. 2009, 74, 442-444.

3) Sygula, A.; Xu, G.; Marcinow, Z.; Rabideau, P. W. Tetrahedron 2001, 57, 3637-3644.

4) Lee, H. B.; Sharp, P. R. Organometallics 2005, 24, 4875-4877.

5) Jones, C. S.; Elliott, E.; Siegel, J. S. Synlett 2004, 1, 187-191.

6) Petrukhina, M. A.;Andreini, K.W.; Mack, J.; Scott,L. T.; J. Org. Chem. 2005, 70, 5713-5716.

7) Jones, D. R.; Mack, J. Ph.D dissertation 2011, University of Cincinnati.

8) Dey, J.; Will, A. Y.; Agbaria, R. A.; Rabideau, P.W.; Abdourazak, A. H.; Sygula, R.; Warner, M. J.

Fluoresc. 1997, 7, 231-236.

Importance of Linker: Synthesis, Structure and Properties

1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31) an intermediate used to synthesize corannulene based carcerands discussed in next chapter was analyzed for its photophysical properties purely out of curiousity (scheme 18) . To our surprise, UV-Vis absorptions of this intermediate overlaps with absorption from 20. To gain insight, we theoretically calculated the UV-

Vis spectra using B3LYP level of theory with 6-31G* as the basis set, where calculated spectra also was in complete agreement with the experimental observation (fig. 26). For comparison we have also included the absorption of 1,8-dialkynylcorannulene (16). Two similar strong absorptions at

288 & 317 nm from either compound which are structurally different, raises an important question regarding enhancement of conjugation and the role of the linker.

Further is it possible that only one out of three π-bonds from the phenyl ring are participating in conjugation, if so then replacing the phenyl rings with a cis-double bond followed by attaching additional alkynyl chromophores may extend the absorption even further into mid visible regions than the moieties synthesized and discussed in chapter II.

Scheme 18: Synthesis of 31.

Figure 26: Surprising similarity in absorption for 20 and 31.

With this motive we initiated the synthesis of enediynes units keeping the chromophoric groups same.

Synthesis:

Reterosynthetically, we could cleave either sides of cis double bond as depicted in scheme 19.

Path a) results in dialkynylcorannulene (16) with the rest of the unit intact

b) results in bisenylcorannulene with arylalkyne as synthons

Path a) looks more promising and advantageous as corannulene unit in form of dialkyn derivative a hard to obtain moiety is used once and the coupling partner can be synthesized in a stepwise manner with commercially available reagents. Whereas, the major disadvantage associated with path b) is that it needs the use of corannulene unit twice for coupling: first to introduce cis double bond and later couple with arylalkyne.

Scheme 19: Reterosynthetic strategy to incorporate novel enediyne linker

Scheme 20: General approach towards synthesis of 32 and 33.

Corresponding aryl iodide was coupled with slight excess of trimethylsilylacetylene at room

temperature in presence of Pd(PPh3)4/CuI (1:1)/piperidine in THF. Later, desilyation was performed in presence of potassium carbonate. Subsequently, arylalkyne obtained was coupled quickly with corresponding cis-1,2-dichloroethene under Sonogashira conditions mentioned above to obtain corresponding chromophores depicted in scheme 20 in good yields.

[(3Z)-4-chloro-3-buten-1-yn-1-yl)]corannulene synthesis (34):

However, applying above mentioned synthetic methodology would need ethynylcorannulene to be used as one of the coupling intermediate. Unstable nature of the intermediate makes its recovery hard as excess quantities of corresponding alkyne is needed to drive the reaction forward. Hence, we slightly modified the route which would rather include iodocorannulene (18) instead of corresponding ethynylcorannulene. Below is the synthetic strategy we determine to use for the synthesis of [(3Z)-4-chloro-3-buten-1-yn-1-yl)]corannulene (34).

Scheme 21: Importance of iodocorannulene in synthesizing 34.

To our surprise, desilylated product reacted with itself and decomposed more quickly than we expected. A quick literature search supported our hypothesis; these compounds readily polymerize

and hence should be stored at -70oC1. Hence, we revisited general scheme 20 to synthesize 34. In case of synthesizing 35 rather than starting with trimethylsilylacetylene we started with (4- bromophenylethynyl)trimethylsilane (36) and followed the procedure as described in scheme 22.

Scheme 22: Synthesis of 35.

For comparison of photophysical properties with 35 we synthesized 1-bromo-4-

[(phenyl)ethnynyl]benzene (36). Scheme 23 elucidates the strategy used for its synthesis.

Scheme 23: Synthesis of 36.

Once desired chromophores with enediyne bonds were synthesized, we diverted our attention to couple these chromophores with 16 and 17 using optimized conditions of Sonogashira coupling

methodology (Pd(PPh3)4 / CuI (1:2) /n-BuNH2 /toluene). It is important to note that we have screened different conditions and finally obtained good yields when Pd:Cu ratio was (1:2) with n-

BuNH2 as base and either benzene or toluene as solvent.

A general synthetic route is presented in scheme 24 and 25 to help illustrate the coupling sequence.

Scheme 24: General synthetic approach for synthesizing 37, 38, 39, and 41.

Scheme 25: Synthesis of 42, 43, 44 and 46.

Trial reactions to obtain both 40 and 45 in multiple attempts met with failures. On the other hand, after synthesis, hard to remove impurities were detected for compound 37, 44 and 46.

Multiple purification (silica gel column/prep t.l.c) with different solvents including carbon disulfide resulted in failures. Even, refluxing the compound for short periods in dichloromethane/carbon disulfide/ethanol failed. Hence, these compounds were not analyzed for their photophysical properties.

Next in series was to test the Sonogashira optimized conditions on a higher level, by coupling

1,2,7,8-tetraethynylcorannulene with different chromophores. Scheme 26 describes our synthetic methodology. Multiple trials to couple 36 resulted in failures, whereas coupling with 34 and 35 was never attempted.

Scheme 26: Synthesis of 47 and 48

Results and Discussion:

U.V-Vis absorption spectra of 31 looks strikingly similar to that of 20 raises an important question; are all 3 π bonds of phenyl pendent in case of 20 participating in conjugation with the corannulene core or is it only one π bond ?

This question was the motive behind synthesizing compounds listed in scheme 24, 25 and 26.

From chapter 2 we already knew corannulene based compounds exhibits strong red shifts with absorption well into visible region along with intense fluorescence and blue emission upon excitation with laser at 325 nm. We were eager to find out how the structural changes of the linker length would contribute to better understanding the aspect of conjugation and its impact on bulk photophysical properties of corannulene. This study would help us identify the right proportion of

linker length needed to exhibit effective conjugation with corannulene and result in blue emitter with robust potential.

Upon completion of synthesis, 1X10-5 M solutions in dichloromethane were prepared and used to examine their photophysical properties. For comparison purpose absorption spectra present in fig. 27 elucidates the difference in conjugation, enhancement in presence/absence of linker.

0.8

0.7

0.6

0.5

0.4

Absorption 0.3

0.2

0.1

0 260 360 460 Wavelength (nm) Figure 27: Influence of linker over absorption of corannulene based compounds

Presence of enediyne units show significant shifts in absorption for 41 and 42 in comparison to

20 and 21. However, the absorption band still resembles the appearance to its predecessors (20, 21).

In case of compound 41, we can still see broad absorption peak at 324 nm with a red shift of 20 nm when compared to 21. Additionally, the shift of 20 nm is also depicted in its weak shoulder at 382 nm which trails well into visible region. Surprisingly, we notice a similar extent of red shift for compound 42. In other words, incorporating an additional phenyl unit (42) does not bring a drastic change in its absorption pattern. Above all, 39 exhibited maximum red shift among all the

compounds reported in fig. 27. Transition at 305 nm arises from parent corannulene while it’s weak shoulder absorptions at 393 nm and 430 nm trailing well into visible region.

Next in series was to examine absorption of anthracene attached corannulene systems (fig. 28).

1.2

0.8 Absorption 0.4

0 260 360 460 Wavelength (nm)

Figure 28: Influence of linker length on absorption of 22, 23 vs. 38, 43

Interestingly, we did not see any appreciable red shift by structurally modifying the length of the linker. However, the appearance of the absorption peaks for compounds 38 and 43 rather shows a broad absorption at 454 nm instead of two distinct peaks observed in case of 22 and 23.

Next in series was to determine if length of the linker has any substantial change in absorption pattern in case of tetrasubstituted corannulene systems. Figure 28 shows the absorption for compounds 47, 48 and for comparison we have included compounds 28, 29 and 1.

1.2

0.8 Absorption

0.4

0 260 360 460 560 Wavelength(nm)

Figure 29: Influence of linker length on absorption of tetrasubstitued corannulene derivatives

Compound 47 shows a continuous broad absorption with two weak bands centered at 339 and

383 nm with a slight shoulder at 480 nm. Weak absorption resembles the two distinct peaks in case of 20; a quick calculation shows a difference of 49 nm and 66 nm red shift for 47. The long trail in case of 20 ends at 425 nm whereas for compound 47 ends at 500 nm, hence a total red shift of 75 nm. On the other hand, we observed a continuous broad absorption for 48 with a long trail which ends at 540 nm. When compared with 38 and 43, a total red shift in absorption is 75 nm for 48.

To gain further insight into the absorption spectra, we performed density functional theory

(DFT) and time dependent density functional theory (TD-DFT) calculations using B3LYP level of theory and 6-31G* as basis set. Optimized structures obtained are shown in fig. 30 below.

Compound Top View Side view

Figure 30: B3LYP/6-31G* optimized structures of compound 38, 43, 44 and 47

Geometry optimized structures for 38, 43 shows a slight twist between pendent anthracene unit and the cis-double bond. The twist accounted for a deviation of 6o, whereas the distance between the hydrogen’s over anthracene with respect to corannulene unit was 3Ǻ. Possible reason for this

slight twist could be close proximity between hydrogens of substituents and hydrogens over corannulene. For compound 43, the distance between two pendent corannulene bowls was measured to be as 9Ǻ. On the other hand the distance between the two rim hydrogens were measured to be 5.1Ǻ. Corannulene units are slightly twisted and its deviation from planarity can be seen in side view, a deviation of 5.6o from planarity was noticed. In case of compound 47 the distance between the benzene rings connected at 1,8 position on corannulene’s outer rim is measured to be 5.5Ǻ. Moreover, we have also noticed that the pendent benzene ring is slightly twisted by 0.5o from planarity.

HOMO HOMO-1 LUMO LUMO+1

Figure 31: B3LYP/6-31G* calculated orbital transitions for compounds 38, 39 and 43

Table 4: Calculated TD-DFT wavelength in comparison with experimental observation

Molecule Experimental (nm) Calculated (nm) f

38 454 nm 557 nm 0.0051

39 430, 393 nm 481, 446 nm 0.3409, 0.5591

41 324, 382 nm - -

42 382, 324 nm 455, 389 nm 0.2705, 0.0599

43 454 nm 527 nm 0.2825

47 480, 383 nm 572 nm 0.2050

48 448, 415, 392, 367 nm - -

To understand orbital transitions observed in absorption spectra (fig. 27, 28 and 29) we performed TD-DFT calculations using B3LYP level of theory and 6-31G* as basis set (fig. 31). The transition at 382 nm for 42 generates from its HOMO to LUMO transition, whereas the prominent peak at 324 nm generates from HOMO -2 to LUMO transition. For compounds 38 and 43, both

HOMO, HOMO-1 and LUMO orbitals are almost centered on anthracene unit with some leakage into corannulene, it is for this reason we are seeing a more of a green emission than in previous case

(22 and 23). Hence, a broad transition at 454 nm which arises from HOMO to LUMO transition excites the anthracene unit alone. Since majority of transition are centered on anthrancene and linker we noticed a more of a green emission upon laser excitation at different wavelengths.

For compound 39, weak shoulder absorption at 430 nm comes from HOMO to LUMO transition centered mainly on the linker with leakage into pendant corannulene. A transition at 393 nm arises from HOMO-1 to LUMO+1 which involves the orbital delocalized on other side of linker with similar leakage into pendant corannulene.

Trends in higher absorptions for tetrasubstituted compound in comparison to corresponding disubstituted compounds is probably due to two reasons: a) with increasing no. of chromophores the overall absorption increases, b) four substituents sets up a symmetry field which present a different spatial distribution of orbital densities and phase when compared to disubstituted pattern.

Pictorially such effect can be visualized in fig. 32 were HOMO to HOMO-3 core orbitals interact with the substituents orbitals in case of tetrasubstitution, whereas such intermixing is not seen for disubstitution.

Figure 32: Interaction of corannulene’s core orbitals with substituents

The fluorescence spectra for compounds 38, 39, 41, 42, 43, 47 and 48 were recorded at 300 nm as depicted in fig.33.

600

500

400

300

Intensity 200

100

0 400 500 600 700 800 Wavelength (nm)

Figure 33: Fluorescence of compounds with enediyne linker with emission at 300 nm

Disubstituted corannulene compounds 39, 41 and 42 all exhibited emission between 400-600 nm which was expected from its absorption spectra. Moreover, the prominent peaks of emission at 441 nm were slightly shifted from its parent corannulene. However, in comparison with its predecessor

(22, 23) both 38 and 43 do not show any shift in their emission because of the additional conjugation. However, tetrasubstituted corannulene derivative 48 exhibited a strong shift in its fluorescence emission (475-728 nm). This particular feature was surprisingly more than what we were expecting. A total shift of 130nm in emission was detected in comparison to its parent corannulene.

In order to check the viability of compounds 38, 39, 41, 42, 43, 47 and 48 as potential blue emitter, we excited compounds at 325, 405 and 442 nm as shown in fig. 34. As expected presence of corannulene or phenyl as substituent (39, 42) gave a bright blue emission, whereas anthracene tethered compounds 43, 38 showed a distinct green emission due to additional conjugation brought in by the length of the linker. Most of our excitement came from the emission of tetrasubstituted derivatives: emission from compound 47 appeared as a blend of green and yellow color, on the other hand we were delighted to witness a pure bright yellow fluorescence which has been observed

for the first time for compound 48. To our knowledge, yellow emission from corannulene based system has never been reported before.

Figure 34: Laser excitation at 325, 405 and 442 nm.

Conclusions:

Serendipitously, we discovered that 1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31) UV-

Vis absorption bands overlapped with that of compound 20. This observation raised a vital question regarding chromophores ability to completely interact with core orbitals of corannulene to exhibit extended conjugation. Hence, in order to confirm if the length of linker has any role to further enhance the overall photophysical properties led to synthesis of compounds mentioned in scheme 24, 25 and 26.

UV-Vis absorption data shows that compounds synthesized with enediyne linker absorbs well into visible region. All compounds still show prominent peak of parent corannulene absorption at approx. 300 nm. A remarkable red shift of 200 nm is noticed in case of 48 from its parent corannulene, which places its absorption well into mid visible region.

As expected a bright blue emission was observed in case of both 39 and 42, whereas extended conjugation in form of linker length now transforms previously seen blend of blue and green color for 22 and 23 into a bright green emission for 38 and 43. Novel yellow emission is observed for compound 48 for the first time.

TD-DFT calculations performed using B3LYP level of theory and 6-31G* as basis set provides evidence for longer wavelength absorption of tetrasubstituted corannulene compounds (47, 48) vs. disubstituted compounds (20).

Compounds synthesized did not show any evidence for decomposition even after months following its synthesis. However, as a precautionary measure we have stored compounds in refrigerator for long standing.

References

1) Kowalewski, J.; Granberg, M.; Karlsson, F.; Vestin, R. J Magn. Resonance 1976, 21, 331-335

Corannulene Based Carcerands – Synthesis, Structure and Properties

The chemistry of cyclophanes with well-defined cavities and shape piques interest among synthetic and theoretical chemists for their elegant applications: host-guest, electron donor-acceptor complexes1,2. Planes above and below act as ligand towards metal by means of their π-electrons.

Figure 35: Metal complexes of different types

As depicted in fig.35, in case of A & B either one or both ligands coordinate with metal center whereas in case of C, metal center is restricted inside the cage of cyclophanes. For example, endohedral fullerenes (EF’s), which offers interesting applications related to magnetism, superconductivity and non-linear optics3,4. Additionally, EF’s are ideal for medicinal applications, for example they can act as hosts for radioactive atoms or as effective magnetic resonance imagining contrast agents5,6. Finally, because of their electron accepting nature can be used as dyads, in solar energy conversion/storage systems7.

However, methods to produce EF’s are cumbersome and often require high temperature (600-

1000oC), high pressure due to its closed shell structure. Moreover, entry also is highly dependent on the size of the guest atom. Saunders et.al have reported EF’s formation by applying 650oC and

3,000 atm which only results encapsulation of 1 out of every 1000 fullerenes, with net results less than 1%8.

As an alternative, researchers attempted to retrosynthetically disconnect C-C bond, create an orifice, insert the guest atom and systematically reconnect the bonds. Komatsu and co-workers have

reported a 7-step synthesis in inserting hydrogen gas inside fullerene9. Even though this process shows promise but certainly is not devoid of complications as the opening and closing of orifice requires high temperatures and once the gas is introduced requires low temperatures to avoid escape of guest atom during the process of rebuilding the ring. Moreover, disconnection is non regioselective process.

Fortunately, corannulene - polar cap of fullerene offers both open concave and convex carbon surface for binding with metals. As an example, several stable complexes of corannulene with metals like Ru, Rh, Os, and Ir are reported in literature10. Dunbar et. al reported that alkali metals

Li+, Na+, K+ and transition metal ions Ti+, Cr+, Ni+ and Cu+ can bind with corannulene with calculated binding energies between 20-50 kcal/mol11. Alkali metals, prefer convex face whereas transition metal ions due their pronounced size preferentially form complexes on convex face.

Examples in literature also suggest that complexation of corannulene with Ru leads to flattening of bowl10.

Hence, the open structure and the ability of corannulene to form metal complex motivated us to design & examine the ability of corannulene based cyclophane to encapsulate small guest atom. As depicted in fig. 36 each cyclophane unit is held together by an enediyne bridge, can undergo thermal cycloaromatization also known as Bergmann cyclization to manifest into carcerands12.

7.2 10.5 Ǻ Ǻ

Figure 36: Open [6,6] 1,5-corannulene cyclophane and [6,6] 1,8-corannulene cyclophane

[6,6] 1,8-cyclophane and [6,6] 1,5-cyclophane offers a variation in cavity size 10.5Ǻ & 7.2Ǻ respectively. Cycloaromatization according to B3LYP-6-31G* calculations results in 5.9Ǻ & 5.4Ǻ for 1,8 and 1,5 cyclophanes (fig. 37). Unfortunately, for an effective Bergmann cycloaromatization to initiate the distance between the two terminal alkyne carbons should be in the range of 2.9-3.5Ǻ13.

5.4 5.9 Ǻ Ǻ

Figure 37: Closed [2,2] 1,5-corannulene cyclophane and [2,2] 1,8-corannulene cyclophane

Hence, complexation of metal could possibly bring the change to initiate cycloaromatization at ambient temperature.

Synthesis:

Sankararaman and co-workers have recently reported the synthesis of [6,6]metacyclophan-3-15- diene-1,5,13,17-tetrayne starting from 1,3-diethynylbenzene14. His elegant and simple synthetic procedure attracted our attention and motivated us to follow similar route starting from diethynylcorannulene, (16, 17), towards synthesizing corresponding [6.,6]-corannulene cyclophanes

(scheme 27).

A two-fold Friedel craft’s acylation over corannulene results in formation of isomers: 1,8-diacetyl corannulene and 1,5-diacetyl corannulene. After purification of individual isomers they will be used separately to give two distinct cyclophanes. However, for the purpose of simplification, we will detail our accomplishments pertaining to the 1,8-isomer.

Subsequently, bischlorovinylcorannulene is obtained in excellent yield upon refluxing for 18 hrs with 1,2-phenylenephosotrichloridite in dry dichloroethane. Base treatment with excess of n-BuLi in presence of insitu generated lithium diisopropylamide in tetrahydrofuran undergoes dehydrohalogenation at -78oC and delivers corresponding 1,8-diethynylcorannulene in good yield.

Next in the series was to add a formyl group one end of alkyne while Sonogashira coupling reaction could be performed over the other end. Unfortunately, trial reactions performed on both test molecules: 1,3-diethynylbenzene & 1,8-diethynylcorannulene by Jennifer Riepenhoff, a former Mack group member, with lithium diisopropylamide as a base did not give any success15. However, when ethylmagnesium bromide was used as a base, meager yields pertaining to desired protection over terminal alkyne was obtained. Discouraged with low yields, the need for protection followed by coupling strategy was re-examined. As an alternative, high dilution technique with different Pd(0) mediated coupling of (z)-1,2-dichloroethene with 1,8-diethynylcorannulene in presence of triethylamine and n-butylamine as base was tested. Analysis of the mixture gave 1,8-bis(4-chloro-3- buten-1-ynyl)-(Z, Z)-corannulene (31) as the only, fully characterized, product in 7.5 % yield.

Scheme 27: Proposed synthesis of [6,6]-1,8-corannulene cyclophane

Even though the attempt to form the desired cyclophane did not result in fruitful outcome, we discovered 1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31)as a potential intermediate with

“chlorides” placed in cis orientation to pursue the synthesis using alternative route.

The first half of this chapter will focus on our attempts to boost the yields of 1,8-bis- chloroenyecorannulene and 1,5-bis-chloroenyecorannulene. Subsequently trial reactions performed to synthesize corresponding carcerands. Whereas, the second half explains the photophysical aspects of synthesized compounds.

Reactivity trend of organic halides towards terminal alkyne follows the corresponding order: vinyl iodides vinylbromide aryl iodide vinyl chloride aryl bromide16. We proceeded to synthesize corresponding vinyl iodide (cis-1,2-diiodoethylene). In a study to separate radioactive isotopes of iodine, Yeung et.al reported synthesis of both cis and trans diiodoethylene17.

Encouraged by simple synthetic procedure we were able to synthesize corresponding trans 1,2- diiodoethylene in excellent yield. Later conversion of trans to cis isomer remained a challenge.

Heating the trans isomer at 165oC for even 7 days did not result in cis isomer. Additionally, we also irradiated the sample under UV light for 3 days and found no change in stereochemistry (scheme

28).

Scheme 28: Failed attempt to synthesize cis-1,2-diiodoethylene

Disappointed with the result, we revisited the coupling of commercially available cis 1,2- dichloroetheylene with 1,8-diethynynylcorannulene. Previous work from our lab specifies the use of

15 both Pd(PPh3)4 and Pd Cl2(PPh3)2 as catalyst . Since both resulted in meager yields they were not choosen initially for further study to boost yields for 31. Pd(PhCN)2Cl2 was chosen for its high solubility in organic solvent and its ease of displacement of PhCN ligands which often leads to high

oxidative insertion – the first step in Sonogashira coupling reaction18. Trial reaction with 1:2 ratio of

Pd:Cu, piperidine as base in THF at room temperature resulted in 12% yield. In as little as 30 min coupling had occurred, however low yields were detected. Reactivity of active catalyst if controlled may result in improved yields. To test the efficacy of the reaction, we decreased the catalytic amount of Pd from 10 mol% to 5 mol%, observing no change in yield %. Later, reducing the temperature to 0oC then to -16oC also did not change the outcome of the reaction. Next, stability of

1,8-diethynylcorannulene in presence of piperidine as base was questioned. 1,8-diethynylcorannulene was found to be intact after overnight stirring with piperidine. Addition of copper (I) co-catalyst in few cases was shown to inhibit product formation. However, test reactions in absence of copper (I) co-catalyst did not deliver any product. Hence, presence of copper (I) halide is imminent for this coupling reaction.

Even, dropwise addition of 1,8-diethynylcorannulene along with piperidine in THF did not improve the yield of the reaction. However, the product obtained was relatively clean. Recent

reports from Fu et. al highlights the use of Pd(PhCN)2Cl2/P(t-Bu)3 capable of performing

19 Sonogashira coupling reactions at room temperature . P(t-Bu)3 is an electron rich, bulky ligand, but is air-sensitive and highly pyrophoric. As an alternative, air stable phosphonium salt [(t-Bu)3 PH]BF4 was used20. No change in the isolated yield was detected under above conditions.

Even though Pd(PhCN)2Cl2 did not prove to be an efficient catalyst, certainly its worth pointing out that high dilution technique delivers clean desired product.

Linstrumelle reported that both nature of catalyst and selection of amine are vital for success in

21 Sonogashira coupling reactions . Following his experimental procedure we replaced Pd(PhCN)2Cl2 with Pd(PPh3)4 and used above optimized conditions. To our delight we boosted the yield of 1,8- bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31) from 12% to 52%.

Once we obtained appreciable amount of 1,8-bis-chloroenynecorannulene, we performed the coupling reaction with 1,8-diethynylcorannulene. Instead of desired [6,6] 1,8-corannulene cyclophane we obtained a trimer of corannulene (49) held with enediyne bridges as shows in fig.38.

Figure 38: Synthesis of corannulene trimer held by enediyne bridges (49)

Self-coupling of terminal alkynes on one end instead of cross coupling with vinylchloride in above carcerand (49) suggests that the amount of copper (I) co-catalyst may be crucial22. Moreover, if the reaction is performed under high dilution technique with addition of 16 at a much slower rate should deliver the desired [6,6]-1,8-corannulene cyclophane.

As depicted in scheme below, neither altering the amount of copper (I) co-catalyst nor did diluting conditions alter the outcome. Hence, we attempted to directly couple excess of 16 with cis-

1,2-dichloroethene under the above mentioned optimized conditions. Unfortunately, every attempt led to formation of 31 (scheme 29) as a major product along with incomplete coupled product as side product (50) as shown in scheme 30.

Scheme 29: Failed attempts to synthesize [6,6]-1,8-corannulene cyclophane

Discouraged by the outcome, we focused our attention to selectively protect one end of 1,8- diethynylcorannulene’s alkyne with triisopropylsilyl-chloride and later perform Sonogashira coupling

Scheme 30: Failed attempt to synthesize [6,6]-1,8-corannulene cyclophane

on the other end. Deprotection with 0.9 eq’s of n-BuLi followed by quenching with triisopropylsilyl-chloride resulted in moderate yields of desired TIPS-protected corannulene derivative (51).

Encouraged by the result, Sonogashira coupling of cis-1,2-dichloroethylene with TIPS-protected corannulene under the optimized conditions was performed. As expected we were able to synthesize the corresponding 1-chloro-8-(triisopropylsilylethynyl)-1-ene-3-ethynylcorannulene (52).

Later when compound was further treated with tips-protected corannulene unit, we did not observed any coupled product as described in scheme 31 below. A similar coupling protocol starting with 17 was also performed (scheme 32).

Scheme 31: Key intermediate 52 synthesis

Scheme 32: Key intermediate 54 synthesis

Results and Discussion:

Corannulene shows prominent absorption bands at 289nm and upon excitation emits fluorescence in the blue part of electromagnetic spectrum. Extending the aromatic π-framework by means of acetyelene bonds as demonstrated by Siegel’s group displays a red shift in absorption from parent corannulene to 295 nm, 302 nm respectively in case of ethynylcorannulene and bicorannlenylacetylene. Even though both compounds reported from Siegel’s group are not thermally stable their shift in absorption patterns promises models engineered based of such linkages by substituting appropriate rim protons of corannulene promises potential application in OLED technology

In regards to this, we have regioselectively synthesized 16 and 17. Absorption of 16 and 17 shows a strong absorption band at 304 nm and 301 nm. To our surprise both 16 and 17 are thermally stable and do not show any signs of decomposition. Moving forward the π-framework of 1,8 and

1,5-diethynylcorannulene was further extended by coupling pendant alkyne bond with cis-1,2- dichloroethene to deliver corresponding compounds. Serendipitously, in an attempt to synthesize 83

[6,6]-1,8-corannulene cyclophane by coupling 31 with 16 instead of desired compound we obtained a novel cyclophane 49 consisting of three corannulene units and held together by enediyne bridges.

Below graphical representation illustrates the absorption data of these compounds and a comparsion study.

In an attempt to examine the absorption data of each synthesized compound, 1x10-5 M dichloromethane solutions for each compound was prepared to examine their absorption spectra, fluorescence and laser excitation.

Both 16 and 17 show an overlapping strong absorption at 305 nm with a shoulder that appears at

354 nm which trails into visible region. Upon further extending the conjugation by coupling with cis-1,2-dichloroethylene we start to see the difference in absorption of 1,8 and 1,5 isomers. 31 shows two prominent absorption centered at 285 nm and 316 nm with a weak absorption at 365 nm with a long trail extending into visible region. On the other hand 1,5-bis(4-chloro-3-buten-1-ynyl)-

(Z, Z) (55) corannulene shows a broad absorption peak λmax at 299 nm, shoulder at 337 nm, 361 nm and 400 nm and trailing into visible region. The absorption pattern for 55 look very close to 1,6- disubstituted derivative of corannulene synthesized by Sigel et.al. Surprisingly, the absorption pattern for carcerand was found to be weaker than parent corannulene. Two prominent weak absorption bands centered at 322nm and 400 nm were observed with a long trail ending at 450 nm.

0.8

0.7

0.6

0.5

0.4

Absorbance 0.3

0.2

0.1

0 270 300 330 360 390 420 450 480 wavelength (nm)

Figure 39: Absorption spectra for compounds 31, 49, 55 and its comparison with 1, 16 & 17

To better understand the absorption data we performed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations with B3LY level of theory and 6-

31G* as basis set. B3LYP level of theory with 6-31G* basis set accurately reproduces bond length, bond angles and dihedral angels for corannulene, hence was used for calculation purposes.

Furthermore, results obtained are in good correlation with experimental data.

Table 5: Experimental and TD-DFT calculated orbital transitions

Molecule Experimental (nm) Calculated (nm) f

31 365, 316 410, 331 0.025, 0.2291

55 360, 299 410, 305 0.0624, 0.2726

49 400 467 0.02

There is a slight difference in values obtained from calculation versus the experimental value, possible reason could be an overestimation of energy levels, as literature proceedings suggests that such scenario happens in case of highly conjugated systems23.

B3LYP geometry optimized structures of 31 and 55 suggests that C-C bond which connects

Molecule Top view Side view

Figure 40: B3LYP-6-31G* geometry optimized structures of 31, 49 and 55 the cis-double bond with alkyne unit is slightly twisted and deviates from planarity. The twist can be viewable from a side view of the molecule in which chlorines facing each other are slightly pushed towards inside (fig. 40).

To get deeper understanding of electronic transition, we calculated the HOMO and LUMO,

HOMO-1 and LUMO +1 orbitals as depicted in figure 41 below:

HOMO HOMO-1 LUMO LUMO+1

Figure 41: B3LYP, 6-31G* calculated orbital transitions for 31, 49 and 55.

The HOMO to LUMO transition in case of 31 and 55 extends from one side of cis-double bond to other through corannulene’s π-aromatic framework, showing the presence of extended conjugation throughout the system. The prominent peak of absorption at 365nm for 1,8 and 360nm in case of 1,5 is due to this transition. Whereas, Homo-1 to Lumo+1 transition generates the transition 316 nm and 299 nm respectively. In both cases experimental values predict a similar pattern of absorption but calculation show a difference of 50 nm. Whereas, transitions generated from cyclophane (49) provides clues for its lower absorption. Cyclophane upon excitation undergoes goes transition and in process of relaxation emits light which rather getting detected at the detector gets captured internally by other two corannulene units held together by alkyne bonds.

TD-DFT calculations further supports this statement as all the transition from HOMO to LUMO are effectively blocked. Reason for such anamoly could be symmetry present within the molecule, a similar lower observation is also depicted in compound 26 as seen in fig. 14. Highly symmetric molecule, but emits low fluorescence. Additionally, it is possible that symmetry at the ground state could allow for more non-radiative relaxation modes and hence results in low absorption and fluorescence.

Absorption data elucidates the fact that conjugation of corannulene’s π-aromatic framework can be extended by means of enyne unit which results in higher absorption and significant red shift in comparison to parent corannulene. Such effect should also be reflected in corresponding fluorescence. To test this we excited all molecules at different wavelength. Consequently, laser excitation of molecules was performed at 325 and 405 nm. Corannulene shows a weak broad low intensity blue emission centered at 420 and 440 nm when excited at 300 nm. The emission profile of corannulene shows two unresolved bands which is primarily due to its bowl to bowl inversion.

However, reports from Rabideau et.al suggest that by locking the bowl as in cyclopentacorannuene shows a restriction in bowl to bowl inversion resulting in resolution of two bands24. Similar

120 300 nm

100 313 nm 400 nm

80 corannulene at 300 nm

325 nm 405 nm

60 Intensity 40

0 360 410 460 510 560 Wavelength (nm) Figure 42: Fluorescence spectra for 31. observation can be seen in present case of fluorescence pattern of dialkyne substituted corannulenes.

The peak emission wavelength for 31 is slightly shifted from parent corannulene by 20 nm.

Additionally, enhanced conjugation delivers higher intensity fluorescence in comparison to parent corannulene. Excitation with 325 nm shows bright blue fluorescence, whereas a weaker emission at

405 nm (fig. 42)

A similar pattern is fluorescence data is observed in case of 55. Shows two emission bands centered at 430 and 460 nm. Enhanced conjugation with high fluorescence intensity is observed in comparison to parent corannulene. As expected from absorbance data, no emission was detected above 400 nm. Laser excitation at 325 nm shows a bright blue fluorescence which fades when excited at 405 nm (fig. 43).

140 300 nm 313 120 400 100 corannulene at 300 325nm 405nm 80

Intensity 60

0 360 410 460 510 560 Wavelength (nm) Figure 43: Fluorescence spectra of 55

Corannulene trimer cyclophane 49 due to its low absorption fails to deliver higher fluorescence in par with its intermediate cis-dichloroenyene derivatives. However, due to its caged structure we

300 nm 50 400 nm

40 corannulene at 300 nm

30 325 nm 405 nm

Intensity 20

0 405 455 505 555 605 Wavelength (nm) can clearly

Figure 41: Fluorescence spectra with laser excitation for compound 49

visualize its resolved emission bands of corannulene centered at 450 and 470 nm. A shift of 30 nm in fluorescence emission is seen in comparison to parent corannulene. Laser excitation at 325 nm shows a intense blue emission whereas at 405 nm the emission fades.

Conclusions:

Previous work from our lab identified corresponding 1,8-bis(chloroenyne)corannulene as potential intermediate to synthesize corresponding [6,6]-1,8-corannulene cyclophane. However, the conditions and the yields of corresponding intermediate were meager. Our initial attempt was to boost the yields of this intermediate. Hence, considering the reactivity pattern, synthesis of cis-1,2- diiodoethylene was attempted. Unfortunately, neither heating trans-1,2-diiodoethylene at 160 °C for

6 days nor irradiation resulted in the desired product. Henceforth, commercially available cis-1,2- dichloroethylene was used in synthesis. Next we examined different “Pd” catalyst in conjunction

with piperidine as base in tetrahydrofuran as solvent. Surprisingly, Pd(PPh3)4 has shown remarkable activity towards coupling vinylchlorides with alkyne. We were able to boost the yield of this intermediate from 12% to 52%. Serendipitously, application of optimization conditions resulted in formation of a novel cyclophane of corannulene which has three corannulene unit intact. Several attempts to obtain desired [6,6]-1,8-corannulene cyclophane resulted in failure. Hence, stepwise construction of cyclophane by protecting alkyne with tips-cl followed by coupling with cis-1,2- dichloroethylene was revisited. Synthesis of corresponding was performed.

No difference in either absorption or emission pattern is detected in case of 1,8 and 1,5 isomer.

Hence, it cannot be concluded which disubstitution pattern is more conjugated (ortho or para like) and which is meta like in case of benzene. Absorption spectra of both intermediates 1,5 and 1,8- bis(chloroenyne)corannulene along with novel corannulene cyclophane was recorded and compared

with 1,8/1,5-dialkyn corannulene and parent corannulene. Extended conjugation leads to significant redshift with higher absorption and fluorescence in case of both 1,5 and 1,8- bis(chloroenyne)corannulene in comparison to parent corannulene. A 40 nm red shift with a tail trailing well into visible region was detected in absorption spectra. However, corannulene cyclophane inspite of its rigid structure exhibits low absorption and low fluorescence. Orbital transitions predict excitation of HOMO-1 is re-absorbed by LUMO or in other words gets quenched. TD-DFT calculations performed at B3LYP level of theory using 6-31G* basis set predict

HOMO to LUMO transitions to be forbidden.

Fluorescence of all three molecules at different excitation (300, 316, 400 nm) shows emission pattern very similar to parent corannulene. It can be concluded that same transition is being excited in all molecules. Hence, increasing conjugation does not lead to higher wavelength emission but certainly intensifies the emission which is in accordance with Kasha’s rule. Laser excitation at 325 and 400 nm nm shows a strong blue emission for all three molecules.

Molecules synthesized did not show any signs of decomposition even after several days from its synthesis.

References

1) Jeppesen, J. O.; Nielsen, M. B.; Becher, J. Chem. Rev. 2004, 104, 5131.

2) Hopf, H.; Gleiter, R.; Mordern Cyclophane Chemistry, Wiley, 2004.

3) Whitehouse, D. B.; Buckingham, A. D. Chem. Phys. Lett., 1993, 207, 332-338.

4) Hu, H.; Cheng, W, D.; Huang, S, H.; Xie, Z.; Zhang, H. J. Theor. Comput. Chem. 2008, 7, 737-749.

5) Dunsch, L., Yang, S. Small, 2007, 3, 1298-1320.

6) Laus, S.; Sitharaman, B.; Toth, E.; Bolskar, R. D.; Helm, L.; Wilson, J.; Merbach, A. E. J. Phys.

Chem. C, 2007, 111, 5633-5639.

7) Guldi, D. M.; Feng, L.; Radhakrishnan, S. G.; Nikawa, H.; Yamada, M.; Mizorogi, N.; Tsuchiya,

T.; Akasaka, T.; Nagase, S.; Herranz, M. A.; Martin, N. J. Am. Chem. Soc. 2010, 132, 9078-9086.

8) Saunders, M.; Jimenez-Vazquez, H. A.; Cross, R. J.; Mroczkowski, S.; Gros, M. L.; Giblin, D. E.;

Poreda, R. J. J. Am. Chem. Soc. 1994, 116, 2193-2194.

9) a) Murata, Y.; Murata, M.; Komatsu, K. J. Am. Chem. Soc. 2003, 125, 7152-7153, b) Komatsu,

K.; Murata, M.; Murata, Y. Science, 2005, 307, 238-240.

10) a) Seider, T. J.; Baldridge, K. K.; O’Connor, J. M.; Siegel, J. S. J. Am. Chem. Soc. 1997, 119, 4781-

4782, b) Alvarez, C. M.; Angelici, R. J.; Sygula, A.; Sygula, R; Rabideau, P. W. Organometallics

2003, 22, 624-626, c) Vecchi, P. A.; Alvarez, C. M.; Ellern, A.; Angelici, R. J.; Sygula, A.; Sygula,

R.; Rabideau, P. W. Organometallics 2005, 24, 4543-4552, d) Petrukhina, M .A.; Andreini, K. W.;

Mack, J.; Scott, L. T. Angew . Chem. Int. Ed. Engl. 2003, 42, 3375-3379.

11) Dunbar, R. C. J. Phys. Chem A. 2002, 106, 9809-9819.

12) Jones, R. R.; Bergman, R. G. J. Am. Chem. Soc. 1972, 94, 660-661.

13) Nath, M.; Huffman, J. C.; Zaleski, J. M. J. Am. Chem. Soc. 2003, 125, 11484-11485.

14) Srinivasan, M.; Sankararaman, S.; Dix, I.; Jones, P. G. Org. Lett. 2000, 2, 3849-3851.

15) Riepenhoff, J. L.; Mack, J. Master’s dissertation, Univ. of Cincinnati, 2006.

16) a) Sonogashira, K. In Metal-Catalyzed Cross-Coupling Reactions; Diederich, F.; Stang, P. J.; Eds.;

Wiley-VCH: New York, 1998; Chapter 5, b) Rossi, R.; Carpita, A.; Bellina, F. Org. Prep. Proced.

Int. 1995, 27, 127-160, c) Sonogashira, K. In Comprehensive Organic Synthesis; Trost, B. M.;

Pergamon: New York, 1991, 3, Chapter 2.4.

17) Cecilia, M. Y.; Yeung, E. S. J. Am. Chem. Soc. 1986, 108, 7529-7533.

18) a) Alami, M.; Linstrumelle, G. Tetrahedron Lett. 1991, 32, 6109-6112, b) Alami, M.; Crouss, B.;

Ferri, F. J. Organomet. Chem. 2001, 624, 114-123.

19) Hundertmark, T.; Littke, A. F.; Buchwald, S. L.; Fu, G. C. Org. Lett. 2000, 2, 1729-1731.

20) Netherton, M. R.; Fu, G. C. Org. Lett. 2001, 3, 4295-4298.

21) Huynh, C.; Linstrumelle, G. Tetrahedron, 1988, 6337-6344.

22) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem., Int. Ed. 2000, 39, 2632-2657.

23) Cai, Z. L.; Sendt, K.; Reimers, J. R. J Chem. Phys. 2002, 117, 5543-5549.

24) Dey, J.; Will, A. Y.; Agbaria, R. A.; Rabideau, P. W.; Abdourazak, A. H.; Sygula, A.; Warner, M J.

Fluoresc. 1997, 7, 231-236.

Experimental Details

All experiments were carried in oven dried glassware with magnetic stirring unless otherwise stated. Commercially available solvents: diethyl ether, dichloroethane, tetrahydrofuran were purified from an MBraun solvent purification system. Flash column chromatography was performed using

Isco Combiflash Companion with prepacked silica gel columns purchased from Silicycle. 1H NMR and 13C NMR spectra were recorded on Bruker 400MHz instrument. MALDI-TOF experiments for molecular mass analysis was carried out using Bruker Biflex III with either anthracene or tetracyanonapthaquinone as matrix. Absorption and emission studies were performed in dichloromethane as solvent in 1-cm path quartz cell using a Cary 50 UV-Vis spectrophotometer and

Cary Eclipse fluorescene spectrophotometer respectively. Luminescence was recoreded using a

Power Technologies laser at respective wavelength. Palladium catalysts used in the study was purchased from Strem and used without any further purification. 1,2-phenylene phosphotrichloridite was purchased from Alfa-Aaesar and used without any further purification.

Other reagents used were purchased from Sigma-aldrich. Photocopies of 1H NMR & 13C NMR for molecules (1-8) were complied from Ph.D dissertation of former graduate student Derek Jones &

Jennifer L. Riepenhoff from our group.

2,7-dimethylnaphthalene (3):

A 1L, one necked round bottom flask equipped with magnetic stirrer was charged with 2,7- dihyroxynaphthalene (2) (49.7g, 0.310 mol), pyridine (500ml) and diethylcarbamoylchloride (130ml) and allowed to reflux overnight. The reaction contents were transferred slowly into a 2-L-beaker containing aq.HCl (6M, 600ml). Light brown solid cake obtained was filtered using Bucher funnel, dissolved in dichloromethane and washed with water. Organic fractions were combined and dried over magnesium sulphate and evaporated the solvent to obtain 110.86g, (99%) of 2,7- bis(diethylcarbamoyloxy)naphthalene as light brown solid. Subsequently, under inert conditions, a

2-L-3-neck round bottom flask is equipped with reflux condenser and oven dried dropping funnel was charged with 2,7-bis(diethylcarbamoyloxy)naphthalene (90.42, 0.253 mol), NiCl2(dppp) (2.44g), and anhydrous diethyl ether (500ml). Methylmagnesium bromide (3M in diethyl ether, 350ml), was added dropwise to the reaction contents over a period of 30 min. The mixture is allowed to refluxed for 2 days. Later addition of aq. HCl(6M, 400ml) is performed over a period of 1 hr. Rate of addition is controlled in such a manner to allow a gentle reflux. Contents were poured into a seperatory funnel and extracted with dichloromethane. Combined organic fractions were washed with water and dried over magnesium sulfate. Crude mixture obtained was purified by passing through a plug of silica gel with cyclohexane as eluting solvent to obtain desired product as white

1 solid (35.4g, 90%). H NMR (400 MHz, CDCl3):  7.67 (d, J = 8.4Hz, 2H), 7.49 (d, J = 8.2, 2H),

7.07 (s, 2H), 2.47 (s, 6H).

3,8-dimethylacenaphthenequinone (4):

A combined solution of 2,7-dimethylnaphthalene (36.24 g, 0.27 mol) and oxalyl chloride (19.27 ml,

0.221 mol) diluted with dichloromethane (100ml) is added dropwise for a period of 1 h to a mechanically stirred ice cold solution (-20oC) of Aluminium bromide (117.88g, 0.44 mol) in

dichloroethane (500 mL) under nitrogen. Maintained the temperature for additional 4 hrs and then left for overnight stirring. The reaction mixture was quenched carefully by slow addition of 1:1 HCl solution, organic layer was washed twice with water (200 mL), dried over magnesium sulfate, filtered, and evaporated to yield a black oily material. The crude product was purified by passing through a silica gel plug following a dichloromethane/cyclohexane (1:1, 1000ml), dichloromethane: cyclohexane (2:1, 2000ml), 100% dichloromethane (1000ml) as a gradient pattern. Fractions containing the desired compound were concentrated to yield 25 g (42%) of diketone as yellow solid.

1 H NMR (400 MHz, CDCl3):  8.04 (d, J = 8.1Hz, 2H), 7.51 (d, J = 8.4Hz, 2H), 2.86 (s, 6H).

1,6,7,10-tetramethylfluoranthene (5):

(I) A 20% solution of potassium hydroxide in methanol (150 mL) was added dropwise to a stirred solution of diketone (15.8 g, 0.08 mol) and 3-pentanone (50 mL) in methanol (48 mL). The solution was continued to stir vigorously at room temperature for 1 h, diluted with water, neutralized with

10% aq.HCl and extracted with dichloromethane. Dried over magnesium sulfate, and solvent evaporated under reduced pressure. (II) Crude oil obtained was quickly transferred to a 350 ml pressure flask containing 2,5-norbornadiene (30 ml) and acetic anhydride (100 ml). Flask was sealed tightly and placed in a wax bath at 140oC for 3 days. The reaction is then cooled to room temperature and neutralized with 10% aq. sodium hydroxide (300 ml), washed with water (300 ml) and extracted with dichloromethane. Organic fractions were combined, dried over magnesium sulfate and solvent is concentrated to dryness to yield a dark brown oil. Crude oil is impregnated over silica and poured over silica plug for purification using cylcohexane as eluting solvent to obtain

1 11g (56%) of desired compound as yellow gummy oil. H NMR (300 MHz, CDCl3):  7.78 (d, J =

8Hz, 2H), 7.46 (d, J = 8Hz, 2H), 7.21(s, 2H), 2.94 (s, 3H), 2.86 (s, 3H).

1,6,7,10-tetrakis(dibromomethyl)-fluoranthene (6):

A three necked round bottom flask equipped with magnetic stirrer under nitrogen atmosphere was charged with 1,6,7,10-tetramethylfluoranthene (4.93 g, 0.02 mol), NBS (34 g, 0.19 mol) and benzoyl peroxide (20 mg). The reaction mixture was refluxed in carbon tetrachloride (200 mL) while irradiation using incandescent light (150 W) for 3 days. The reaction progress was monitored by

TLC. Solvent was evaporated under reduced pressure and the orange solid washed well with water and extracted with dichloromethane, dried and evaporated to yield yellow solid 16 g (94 %). 1H

NMR (400 MHz, CDCl3):  8.28 (d, J=8.7Hz, 2H), 8.20 (s, 2H), 8.0 (d, J=8.4Hz, 2H), 7.20 (s, 2H),

7.08 (s, 2H).

1,2,7,8-tetrabromocorannulene (7):

4.18 g of octabromofluoranthene (4.7 mmol) was refluxed in a mixture of dioxane (200 mL), water

(80 mL) and 3 g of NaOH for 15 minutes. Originally formed dark red color faded with time. The reaction contents were cooled, poured into water (200 mL) and acidified with HCl. Yellowish brown insoluble solid was filtered and dried to yield 2.45 g (92 %) of desired compound. 1H NMR

(400 MHz, CDCl3):  7.96 (s, 2H), 7.96 (d, J=8.7Hz, 2H), 7.85 (d, J=8.1Hz, 2H).

Corannulene (1):

4% aq. HCl (4 mL) was added to a stirring solution of 14 (1 g, 1.76 mmol), KI (4.3 g), Zn (12 g) in ethanol (200 mL) and was refluxed for three days. The reaction progress was monitored by GC, which showed a gradual increase of 6 with time. Solvent was removed under reduced pressure and the product was extracted with dichloromethane, washed couple of times with water, dried and evaporated. Chromatography (silica gel, hexane / dichloromethane (5:1)) gave 0.45 g (59 %) of 6 as a pale yellow solid. 1H NMR (400 MHz, CDCl3):  7.78 (s, 10H).

Bromocorannulene (8)

Corannulene (1) (1g, 4 mmol) and Iodobromide (2.5g, 12 mmol) were dissolved in anhydrous 1,2- dichloroethane (150 mL) and the mixture was stirred at room temperature for 16hrs under nitrogen atmosphere. Later, the solvent was removed under reduced pressure and purified over silica gel using cyclohexane as eluting solvent to obtain a pale yellow solid 1.2g (90%). 1H NMR (400 MHz,

CDCl3):  8.03 (s, 1H), 7.93 (d, J = 8.6Hz, 1H), 7.87-7.78 (m, 6H).

Diacetylcorannulene:

To a solution of aluminium chloride (3.5g, 26 mmol) in dry dichloroethane with nitrogen inlet was added acetyl chloride (3.71 ml, 52 mmol) and stirred at 0oc for 20 min. Later corannulene (0.65g, 2.6 mmol) was added and kept for 2 days stirring. A color change was detected from yellow to orange with time. After 2 days, reaction was carefully quenched with 10% aq. HCl, washed with water and extracted with dichloromethane. Combined organic fractions, dried over magnesium sulfate and rotovaped to obtain green solid. Crude was purified by column chromatography using a gradient of

100% dichloromethane and later ramping down to 95:05 dichloromethane:ethylacetate. First peak separated is 1,5-diacetylcorannulene (19) 0.23g (29%) and the second peak corresponds to 1,8-

1 diacetylcorannulene (18) 0.4g (45%). H NMR (400 MHz, CDCl3):  8.67 (d, J = 6.4Hz, 1H), 8.64

(d, J = 6.4Hz, 1H), 8.51 (s, 1H), 8.48 (s, 1H), 7.92-7.85 (m, 4H), 2.84 (s, 6H), 2.34 (s, 3H). 13C NMR

(400 MHz, CDCl3,):  199.56, 199.40, 137.93, 136.64, 136.36, 136.24, 136.04, 134.71, 134.05, 133.25,

132.21, 131.76, 129.56, 129.27, 128.90, 128.55, 128.48, 128.31, 128.29, 127.96, 127.325, 28.41, 28.38.

1 13 H NMR (400 MHz, CDCl3):  8.45 (s, 1H), 8.28 (s, 1H), 7.65 (m, 2H), 2.78 (s, 3H). C NMR (400

MHz, CDCl3): 199.30, 137.67, 135.94, 134.64, 133.54, 132.74, 132.30, 129.47, 128.30, 127.97,

127.76, 127.37, 28.44

1,8-dichlorovinylcorannulene:

To a solution of 1,8-diacetylcorannulene (18) (0.58g, 1.01 mmol) in dry dichloroethane (40 ml) add carefully add 1,2-phenylene phosphotrichloridite (3.43g, 13 mmol) as solid and set the contents for reflux under inert atmosphere for 18 hours. Later the reaction mixture was quenched with water (10 mL) and extracted with dichloromethane. The organic fractions were combined, dried over magnesium sulfate and concentrated under vacuum. The crude product was purified by column chromatography (cyclohexane) to give 0.59g of 19 (91%) as yellow solid. 1H NMR (400 MHz,

13 CDCl3):  8.09 (s, 1H), 8.03 (s, 1H), 7.84-7.80 (m, 2H), 5.93 (d, J = 6Hz, 2H). C NMR (400 MHz,

CDCl3):  137.86, 137.118, 136.12, 135.32, 134.21, 131.23, 129.72, 128.31, 127.43, 127.24, 127.05,

126.83, 118.11

1,5-dichlorovinylcorannulene:

To a solution of 1,5-diacetylcorannulene (19) (0.18g, 0.54 mmol) in dry dichloroethane (40 ml) add carefully add 1,2-phenylene phosphotrichloridite (1.08g, 4.39 mmol) as solid and set the contents for reflux under inert atmosphere for 18 hours. Later the reaction mixture was quenched with water (10 mL) and extracted with dichloromethane. The organic fractions were combined, dried over magnesium sulfate and concentrated under vacuum. The crude product was purified by column chromatography (cyclohexane) to give 0.18g of 21 (92%) as pale yellow solid. 1H NMR (400 MHz,

13 CDCl3):  8.04-8.0 (m, 3H), 7.96 (s, 1H), 7.76-7.69 (m, 3H), 7.68 (s, 1H), 5.89-5.88 (m, 4H). C

NMR (400 MHz, CDCl3):  137.87, 137.62, 137.32, 136.09, 135.99, 135.407, 134.82, 134.66, 130.91,

129.68, 129.66, 128.55, 128.30, 127.72, 127.63, 127.42, 127.28, 127.23, 127.04, 126.78, 126.73,

126.61, 126.34, 118.

100

1,3,5,7,9-pentachlorocorannulene (9):

In a 100ml one neck round bottom under positive flow of argon, charge the flask with corannulene

(100mg, 0.4mmmol), ICl (0.84g, 5.2 mmol) in anhydrous dichloroethane (10 ml) and left stirring for

3 days. A sudden change in color was noticed upon addition of ICl from yellow to black.. After stipulated time flask was diluted with 30 ml of chloroform and washed with 5% sodium thiosulphate and later with water to obtain yellow precipate which was rotovaped. Later, solid was sonicated with cyclohexane and dichloromethane to obtain a pale yellow title compound 120 mg (71%). 1H NMR

(400 MHz, CDCl3):  7.98 (s, 5H).

(4-bromophenyl)corannuleneacetylene (15):

In presence of nitrogen atmosphere, a 100 ml round bottom flask was charged with PdCl2(PPh3)2

(0.038g, 0.05 mmol), CuI ( 0.01g, 0.05 mmol), 4-bromoethynylbenzene (0.1g, 0.55 mmol), iodocorannulene (0.20g, 1.1 mmol) was charged in the order specified along with triethylamine (40 ml) as base and anhydrous tetrahydrofuran (20 ml) as solvent. Reaction contents were left for stirring at 40oC for 24 hours. After specified time, contents were carefully neutralized with 12M

HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and rotovaped. Column chromatography (silica gel, cyclohexane:dichloromethane (95:5)) delivered the

1 desired target compound 0.11g (46%) was obtained as yellow solid. H NMR (400 MHz, CDCl3): 

7.97 (d, J = 8.8 Hz, 1H), 7.93 (s, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.67- 7.65 (m, 4H), 7.62 (s, 1H), 7.59

13 (d, J = 8.0 Hz, 1H), 7.49-7.44 (m, 4H). C NMR (400 MHz, CDCl3):  136.10, 135.67, 135.65,

135.34, 135.14, 133.20, 131.84, 131.78, 131.31, 131.18, 131.12, 130.94, 130.75, 130.24, 127.26,

12750,127.46, 127.43, 127.14, 126.63, 125.91, 122.79, 122.25, 121.00, 92.08, 88.96. HRMS calculated

for C26H13Br: 428.02, found [M+] 428.02

101

1,8-diethynylcorannulene (16):

An oven dried 100 mL round bottom equipped with magnetic stirrer under nitrogen flow was charged with diisopropylamine (3 ml, 21 mmol) in dry THF (30 ml). To this n-Buli (48 ml,

1.6M, 30 mmol) was added at -78oC and stirred for 20 min. Later, 1,8-dichlorovinylcorannulene

(0.74g, 1.9 mmol) solid was added in one pot. A quick color change from colorless to blue color was detected. Reaction progress was monitored by tlc, complete transformation to product takes place after 4 hrs of stirring. Reaction mixture was quenched with water, acidified with 10% aq. HCl and extracted with dichloromethane. Organic fractions were combined, dried over magnesium sulfate and evaporated to yield yellowish-black solid. Purification by column chromatography on silica gel (cyclohexane) yielded the desired product 22 as yellow solid 0.47g, (81%). 1H NMR (400

13 MHz, CDCl3):  8.093 (s, 1H), 8.04 (s, 1H), 7.79-7.73 (m, 2H), 3.44 (s, 1H). C NMR (400 MHz,

CDCl3):  135.75, 135.43, 134.94, 132.57, 131.67, 131.29, 13012, 127.55, 127.04, 126.53, 120.29,

81.56, 80.95.

1,5-diethynylcorannulene (17):

An oven dried 100 mL round bottom equipped with magnetic stirrer under nitrogen flow was charged with diisopropylamine (1.45 ml, 10 mmol) in dry THF (30 ml). To this n-Buli (24 ml,

1.6M, 15 mmol) was added at -78oC and stirred for 20 min. Later, 1,5-dichlorovinylcorannulene

(0.18g, 0.50 mmol) solid was added in one pot. A quick color change from colorless to blue color was detected. Reaction progress was monitored by tlc, complete transformation to product takes place after 4 hrs of stirring. Reaction mixture was quenched with water, acidified with 10% aq. HCl and extracted with dichloromethane. Organic fractions were combined, dried over magnesium sulfate and evaporated to yield yellowish-black solid. Purification by column chromatography on silica gel (cyclohexane) yielded the desired product 23 as yellow solid 0.12g, (80%). 1H NMR (400

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13 MHz, CDCl3):  7.99-7.97 (m, 4H), 7.78-7.69 (m, 4H), 3.43 (s, 1H), 3.42 (s, 1H). C NMR (400

MHz, CDCl3):  135.64, 135.33, 135.26, 135.20, 134.80, 132.59, 132.26, 131.44, 131.32, 130.98,

130.23, 130.01, 127.70, 127.17, 126.89, 126.27, 120.50, 120.20, 81.59, 81.56, 80.97, 80.93.

Iodocorannulene (18):

To a solution of bromocorannulene (8) (1.05g, 3.19 mmol) in dimethylformamide (40 ml), CuI (3.0g,

15.78 mmol) and KI (5.88 g, 35.42mmol) was added in one pot in presence of nitrogen and left stirring for 30 hours. A sudden change in color was notice from yellow to dark brown. Upon completion of time, excess iodine was quenched with 10% aq.sodium thiosulphate solution, washed with water and extracted with dichloromethane. Organic fractions were collection, dried over magnesium sulfate and rotovaped to obtain a yellow solid. Chromatography (silica gel, cyclohexane)

1 delivered the desired compound as pale yellow solid 1.15 g (96%). H NMR (400 MHz, CDCl3): 

8.30 (s, 1H), 7.85-7.67 (m, 8H).

(Trimethylsilylacetylene) corannulene:

Charge PdCl2(PPh3)2 (84.5 mg, 0.12 mmol), CuI (30 mg, 0.15 mmol), trimethylsilylacetylene (0.44 g,

4.55 mmol), bromocorannulene ( 0.5g, 1.51 mmol) in one neck 100 ml round flask in presence of nitrogen with triethylamine (30 ml) as base and tetrahydrofuran (30 ml) as solvent. Stir the contents at room temperature for 24 hours. Upon completion of time, neutralize the contents carefully with

12 M HCl and wash with water (50 ml) and extract with dichloromethane. Combine the organic layers, dry over magnesium sulfate and rotavap. Column chromatography (silica gel, cyclohexane)

1 delivered the title compound as yellow solid 0.5g (96.1%). H NMR (400 MHz, CDCl3):  7.95 (s,

1H), 7.942-7.80 (m, 3H), 7.73-7.66 (m, 5H), 0.498 (s, 9H).

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Ethynylcorannulene:

To a stirred solution of (trimethylsilylacetylene) corannulene (0.12g, 0.35 mmol) in 1:1 methanol/dichloromethane, potassium carbonate (0.14g, 1.05 mmol) is added in one pot and allowed to stir for 2 hour at room temperature. Reaction contents were quickly neutralized with

10% aq. HCl, washed with water (50 ml) and extracted with dichloromethane. Organic layers were combined, dried over magnesium sulfate and rotovaped. Column chromatography (silica gel, cyclohexane) delivered the title compound 0.095g (98%) as pale yellow solid. 1H NMR (400 MHz,

CDCl3):  8.00-7.97 (m, 2H), 7.82 (d, J = 8.8 Hz, 1H), 7.77-7.71 (m, 6H), 3.38 (s, 1H).

1,8-Bis(phenynyl)corannulene (20):

In presence of nitrogen atmosphere, a 100 ml round bottom flask was charged with Pd(PPh3)4 (

0.046g, 0.04 mmol), CuI (0.008g, 0.04 mmol), iodobenzene (0.08g, 0.41 mmol), 1,8- dialkyncorannulene (0.06g, 0.20 mmol) in the manner as specified. To this mixture triethylamine (3 ml) as base and tetrahydrofuran (3 ml) as solvent were added, kept for overnight stirring at 40oC.

Progress of the reaction was monitored by tlc. Once completed, the reaction mixture was neutralized with 12M HCl, washed with water, extracted with dichloromethane. Organic layers were combined, dried over magnesium sulfate and concentrated under reduced pressure. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed with gradient starting from 100% cyclohexane and ramping down to 50% cyclohexane using automated system. Title

1 compound was obtained as yellow solid 40mg (44%). H NMR (400 MHz, CDCl3):  8.20 (s, 1H),

13 8.07 (s, 1H), 7.79-7.78 (m, 2H), 7.76-7.76 (m, 2H), 7.42-7.40 (m, 4H). C NMR (400 MHz, CDCl3):

135.63, 135.18, 131.62, 131.38, 131.30, 130.64, 128.60, 128.51, 127.67, 12704, 126.65, 123.01, 121.63,

93.48, 87.58. HRMS: calculated for C36H18: 450.14 found [M+] 450.14.

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1,5-bis(phenylnyl)corannulene (21):

To a 100 ml one neck round bottom flask, under a flow of nitrogen was added Pd(PPh3)4 ( 0.02g,

0.01 mmol), CuI (5 mg, 0.02 mmol), iodobenzene (0.04g, 0.21 mmol), 1,5-dialkyncorannulene (

0.03g, 0.10 mmol), triethylamine (3 ml), tetrahydrofuran (3 ml) in the order specified and was allowed to stir for overnight at 40oC. Reaction was quenched with 12M HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and concentrated under reduced pressure to obtain black solid. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting from 100% cyclohexane to 50% cyclohexane, which gave

1 the title compound 10mg (21%) as yellow solid. H NMR (400 MHz, CDCl3):  8.13 (d, J = 8.00Hz,

1H), 8.07 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 8 Hz, 1H), 7.83-7.77 (m, 1H), 7.69 (d, J = 8 Hz, 2H), 7.42-

13 7.41 (m, 4H). C NMR (400 MHz, CDCl3): 135.59, 135.53, 135.17, 131.81, 131.42, 131.34, 131.22,

131.14, 131.04, 130.69, 130.47, 128.58, 128.48, 127.67, 127.55, 127.20,127.01, 126.50, 126.43, 123.18,

121.84, 93.47, 93.42, 87.56. HRMS: calculated for C36H18: 450.14, found [M+] 450.18

1,8-bis(9-anthranyl)corannulene (22):

To a 100 ml one neck round bottom flask, under a flow of nitrogen was added Pd(PPh3)4 ( 0.038g,

0.032 mmol), CuI (6.6 mg, 0.03 mmol), 9-iodoanthracene (0.13g, 0.42 mmol), 1,8- dialkyncorannulene (0.05g, 0.16 mmol), triethylamine (5 ml), tetrahydrofuran (5 ml) in the order specified and was allowed to stir for overnight at 40oC. Reaction was quenched with 12M HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and concentrated under reduced pressure to obtain reddish-orange solid. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting from 100% cyclohexane to

50% cyclohexane, which gave the title compound 25mg (22%) as yellowish orange solid. 1H NMR

(400 MHz, CDCl3):  8.82 (d, 2H), 8.49 (s, 1H), 8.46 (s, 1H), 8.32 (s, 1H), 8.05 (d, 2H), 7.87 (d, 2H),

105

7.69-7.65 (t, 2H), 7.56-7.53 (t, 2H). 13C NMR (400 MHz, CDCl3):  135.66, 135.22, 132.68, 131.55,

131.10, 130.09, 128.70, 128.05, 127.58, 126.99, 126.87, 126.75, 126.73, 125.70, 121.99, 120.40,

117.716, 117.08, 99.26, 90.63.

1,5-bis(9-anthranyl)corannulene (23):

To a 100 ml one neck round bottom flask, under a flow of nitrogen was added Pd(PPh3)4 ( 0.038g,

0.032 mmol), CuI (6.6 mg, 0.03 mmol), 9-iodoanthracene (0.13g, 0.42 mmol), 1,5- dialkyncorannulene (0.05g, 0.16 mmol), triethylamine (5 ml), tetrahydrofuran (5 ml) in the order specified and was allowed to stir for overnight at 40oC. Reaction was quenched with 12M HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and concentrated under reduced pressure to obtain reddish-orange solid. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting from 100% cyclohexane to

50% cyclohexane, which gave the title compound 20mg (17%) as yellowish orange solid. 1H NMR

(400 MHz, CDCl3):  8.83 (d, J = 8.8Hz, 4H), 8.48 (s, 2H), 8.40-8.30 (m, 4H), 8.07 (d, J = 8.8Hz,

4H), 8.039 (d, J = 8.8Hz, 1H), 8.035 (d, J = 8.8Hz, 1H), 7.91 (s, 2H), 7.71 (t, 4H), 7.59 (t, 4H).

HRMS: calculated for C52H26: 650.20 found [M+] 650.01.

1,8-bis(corannulenyl)corannulene (24):

Under the positive flow of nitrogen, charge a 100 ml round bottom flask with PdCl2(PPh3)2 (23 mg,

0.03 mmol), CuI (6 mg, 003mmol), 1,8-dialkyne corannulene (50 mg, 0.16 mmol), iodocorannulene

(0.15 g, 0.41 mmol) along with triethylamine (5 ml) and tetrahydrofuran (5ml) in the order specified.

Allow the contents to stir for 18 hours at room temperature in absence of light. Upon completion of time, quench the reaction with 12M HCl, wash with water, extract with dichloromethane, dry over magnesium sulfate and evaporate the solvent under reduce pressure to obtain black solid.

106

Column chromatography (silica gel, hexane:dichloromethane) was performed following a gradient profile starting from 100% cyclohexane to 50% dichloromethane. Desired compound is eluted in

70% cyclohexane fraction. Title compound is obtained as a yellow solid 30 mg (22%). 1H NMR

(400 MHz, CDCl3):  8.32 (d, J = 8 Hz, 1H), 8.27 (d, J = 8.8 Hz, 2H), 8.20-8.17 (m, 4H), 8.17 (s,

1H), 7.95 (d, J = 8.8 Hz, 2H), 7.85-7.75 (m, 16H). HRMS: calculated for C64H26: 794.91, found

[M+] 794.20.

1,5-bis(corannulenyl)corannulene (25):

To a 100 ml one neck round bottom flask, under positive flow of nitrogen was added PdCl2(PPh3)2

(23 mg, 0.03 mmol), CuI (6 mg, 0.03 mmol), 1,5-dialkyncorannulene (0.05g, 0.167 mmol), iodocorannulene (0.15g, 0.41 mmol), triethylamine (15 ml), tetrahydrofuran (5 ml) in the order specified and the solution was allowed to stir for 36 hours. Later, reaction was quenched with 12M

HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and rotovaped. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed with a gradient profile starting with 100% cyclohexane and ramping up the amount of dichloromethane.

Desired product was obtained in meager amounts 5 mg (4%) as yellow solid. 1H NMR (400 MHz,

CDCl3):  8.24-8.20 (m, 2H), 7.97-7.95 (d, J = 8.8Hz, 2H), 7.84-7.79 (m, 10H). HRMS: calculated

for C64H26: 794.91 found [M+] 794.20.

1,8-bis(phenylacetylenecorannuenyl)corannulene (26):

To a 50 ml one neck round bottom flask, under positive flow of nitrogen was added 1,8- dialkyncorannulene (0.023g, 0.079mmol), (4-bromophenyl)corannuleneacetylene (0.102mg,

0.231mmol), PdCl2(PPh3)2 (23 mg, 0.03 mmol), CuI (6 mg, 0.03 mmol), triethylamine (15 ml), tetrahydrofuran (8 ml) in the order specified and the solution was allowed to stir at 90oC for 18

107

hours. Later, reaction was quenched with 12M HCl, washed with water, extracted with dichloromethane, dried over magnesium sulfate and rotovaped. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed with a gradient profile starting with 100% cyclohexane and ramping up the amount of dichloromethane. Desired product was obtained in

1 meager amounts 5 mg (4%) as yellow solid. H NMR (400 MHz, CDCl3):  8.22(s, 1H), 8.15 (d, J=

8.8Hz, 1H), 8.10-8.06 (m, 2H), 7.99-7.8 (m, 11H), 7.72 (s, 2H). HRMS: calculated for C80H34:

994.27 found [M+] 994.27.

1,2,7,8-tetrakis(1-ethynyl)corannulene (27):

400 mg (0.63 mmol) of 28 was stirred in conjunction with K2CO3 (3 eq., 1.89 mmol) in 1:1 ratio of

CH2Cl2 / MeOH (15 ml each) for 2 hrs. Crude reaction mixture was diluted with water and extracted with dichloromethane, dried over MgSO4 and rotovaped. Column chromatography (silica gel, cyclohexane), yielding 190 mgs (90%) of 27 as yellow solid, shows quick decomposition on standing at room temperature. 1H NMR (400 MHz, CDCl3):  8.05 (s, 1H), 8.02 (d, J = 8.8 Hz,

1H), 7.85 (d, J = 8.8 Hz, 1H), 3.808 (s, 1H), 3.801 (s, 1H).

1,2,7,8-tetrakis[2-(trimethylsilyl)ethynyl]corannulene (28):

400 mg (0.706 mmol) of tetrabromocorannulene was refluxed under inert atmosphere for 3hrs with

400 mg (12 eqs) of trimethylsilylacetylene, 156 mgs of PdCl2(PPh3)2, 56 mgs of CuI in 1:1 ratio of 30 ml of triethylamine and THF. Reaction mixture was neutralized with 10% HCl solution, washed twice with water and extracted with dichloromethane. Organic layer was dried over MgSO4, and rotovaped. Crude material was chromatographed (silica gel, cyclohexane), yielding 386 mg (86%) of

1 28 as yellow solid. %). H NMR (400 MHz, CDCl3):  7.99 (s, 1H), 7.96 (d, J = 8.8 Hz, 1H), 7.81

(d, J = 8.8 Hz, 1H), 0.37 (s, 18 H). HRMS: calculated for C40H42Si4: 634.24 found [M+] 634.11. 108

1,2,7,8-tetrakis(2-phenylethynyl)corannulene (29):

400mg (0.706 mmol) of tetrabromocorannulene was refluxed for 48 hrs in a pressure vessel under

inert atmosphere with phenylacetylene (12 eq, 0.93 ml), PdCl2(PPh3)2 (156mg, 0.22 mmol), CuI (56 mg, 0.28 mmol) in 1:1 ratio of triethylamine (30 ml) and THF (30 ml). Reaction mixture was neutralized with 10% HCl solution, washed twice with water and extracted with dichloromethane.

Combined organic phase was dried over MgSO4 and rotovaped. Later crude material was chromatographed (silica gel, cyclohexane:dichloromethane), yielding 300mg (65%) of 29 as yellow

1 solid. H NMR (400 MHz, CDCl3):  8.15 (s, 1H), 8.11 (d, J = 8.8 Hz, 1H), 7.88 (d, J = 8.8 Hz, 1H),

7.75-7.72 (m, 5H), 7.44-7.40 (m, 5H). HRMS: calculated for C52H26: 650.20 found [M+] 650.08.

9, 9’, 9’’, 9’’’- (1,2,7,8-corannulenetetra-2, 1-ethynetetrayl)tetrakis-anthracene (30):

A mixture of 27 (120 mgs, 0.347 mmol), 9-iodo-anthracene (0.52g, 1.7 mmol), Pd(PPh3)4 (80 mg,

0.069 mmol), CuI (26.2 mg, 0.13 mmol) was stirred in a 1:1 mixture of THF (10 ml) and triethylamine (10 ml) at 60oC for overnight. Crude solid reaction mixture was rotovaped and filtered using dichloromethane to wash soluble impurities, yielding sparingly soluble 30 as orange solid (50

1 mg, 15%). H NMR (400 MHz, CDCl3):  8.89 (d, J = 8Hz, 4H), 8.61 (s, 1H), 8.51 (d, J = 8.4 Hz,

1H), 8.48 (s, 2H), 8.10 (d, J = 8.8 Hz, 1H), 8.01-7.98 (m, 4H), 7.36-7.35 (m, 4H), 7.069-7.046 (m,

4H). HRMS: calculated for C84H42: 1050.33 found [M+] 1050.3.

1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31):

A 50 ml one neck round bottom flask was charged with Pd(PPh3)4 (0.06 g, 0.05 mmol), CuI (0.02g,

0.10 mmol), cis-1,2-dichloroethene (0.15 g, 1.56 mmol), piperidine (0.18g, 2.13 mmol) and tetrahydrofuran (10 ml) and allowed to stir for 30 min. In a separate 25 ml one neck round bottom flask charge 1,8-dialkyncorannulene (0.08g, 0.26 mmol), piperidine (0.06g, 0.70 mmol) and

109

tetrahydrofuran (3 ml) in presence of nitrogen and let it stir for 30 min. After specified time, using a automated syringe add 1,8-dialkyncorannulene solution at a rate of 1ml/10 min. Let the reaction stir for overnight at room temperature. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap.

Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title

1 compound 40 mg (35%) as yellow solid. H NMR (400 MHz, CDCl3):  8.18 (s, 1H), 8.03 (s, 1H),

13 7.77-7.68 (m, 2H), 6.57 (d, J = 7.2 Hz, 1H), 6.26 (d, J = 7.2 Hz, 1H). C NMR (400 MHz, CDCl3):

 135.45, 135.15, 134.66, 131.81, 131.56, 131.35, 130.86, 129.98, 128.87, 127.38, 127.16, 126.92,

126.65, 126.38, 120.83, 112.18, 95.68, 87.16.

1-chloro-4-phenyl-(Z)-1-buten-3-yne (32):

To a solution of phenylacetylene (0.19g, 1.82 mmol) in benzene (10 ml) were added in succession

1,2-cis-dichloroethene (0.35g, 3.7 mmol), n-butylamine (0.26g, 3.64 mmol), Pd(PPh3)4 (0.10 g, 0.09 mmol), CuI (4 mg, 0.018 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography

(silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.25 g (85%) as

1 white syrupy liquid. H NMR (400 MHz, CDCl3):  7.56-7.51 (broad, 2H), 7.38-7.33 (broad, 3H),

13 6.47 (d, J = 8 Hz, 2H), 6.12 (d, J = 8 Hz, 2H). C NMR (400 MHz, CDCl3): 131.73, 128.66, 128.41,

123.15, 119.47, 97.62, 87.32. GC/MS: calculated for C10H7Cl: 162.62, found [M+]: 162.1

110

9-(4-chloro-3-buten-1-ynyl)-(Z)-anthracene (33):

To a solution of 9-ethynyl anthracene (0.28g, 1.38 mmol) in benzene (20 ml) were added in

succession 1,2-cis-dichloroethene (0.4g, 4.1 mmol), n-butylamine (0.5g, 6.9 mmol), Pd(PPh3)4 (0.08 g, 0.07 mmol), CuI (26 mg, 0.13 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.25

1 g (77%) as reddish solid. H NMR (400 MHz, CDCl3):  8.66 (d, J = 8.8 Hz, 2H), 8.45 (s, 1H), 8.02

(d, J = 8.4 Hz, 2H), 7.62 (m, 4H), 6.61 (d, J = 7.2 Hz, 1H), 6.43 (d, J = 7.6 Hz, 1H). 13C NMR (400

MHz, CDCl3):  132.75, 131.11, 128.66, 128.45, 128.29, 126.90, 126.72, 125.74, 116.68, 112.48.

1-chloro-4-corannulene-(Z)-1-buten-3-yne (34):

To a solution of ethynylcorannulene (0.43g, 1.44 mmol) in benzene (20 ml) were added in

succession 1,2-cis-dichloroethene (0.41g, 4.3 mmol), n-butylamine (0.52g, 7.2 mmol), Pd(PPh3)4

(0.08 g, 0.07 mmol), CuI (27 mg, 0.14 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.23

1 g (48%) as yellowish-green solid. H NMR (400 MHz, CDCl3):  8.13 (d, J = 8.4 Hz, 1H), 8.02 (s,

1H), 7.87 (d, J = 8.8 Hz, 1H), 7.81-7.74 (m, 6H), 6.57 (d, J = 7.6 Hz, 1H), 6.26 (d, J = 7.2 Hz, 1H).

13 C NMR (400 MHz, CDCl3):  136.14, 135.66, 135.51, 135.15, 131.64, 131.27, 131.19, 130.95,

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130.83, 130.18, 128.87, 127.76, 127.53, 127.50, 127.42, 127.17, 127.13, 126.65, 126.14, 120.86,

112.26, 95.85, 87.00.

1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylcorannynyl)-benzene (35):

To a solution of 1-ethynyl-(4-ethynylcorannulene)benzene (0.5g, 1.33 mmol) in benzene (20 ml) were added in succession 1,2-cis-dichloroethene (0.39g, 4.0 mmol), n-butylamine (0.48g, 6.6 mmol),

Pd(PPh3)4 (0.16 g, 0.14 mmol), CuI (27 mg, 0.14 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.16

1 g (27%) as yellowish-green solid. H NMR (400 MHz, CDCl3):  8.10 (d, J = 8.8 Hz,1H), 8.04 (s,

1H), 7.87 (d, J = 8.8 Hz, 1H), 7.80-7.75 (m, 5H), 7.63 (d, J = 8.4 Hz, 2H), 7.54 (d, J = 8.4 Hz, 2H),

13 6.48 (d, J = 7.6 Hz, 1H), 6.12 (d, J = 7.2 Hz, 1H). C NMR (400 MHz, CDCl3):  136.11, 135.68,

135.65, 135.36, 135.15, 131.74, 131.69, 131.35, 131.19, 131.13, 130.93, 130.78, 130.25, 128.80,

127.65, 127.43, 127.45, 127.40, 127.13, 126.63, 125.94, 123.60, 122.73, 121.04, 111.96, 97.04, 92.78,

89.90, 85.26.

1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylphenyl)-benzene (36):

To a solution of (4-phenylacetylene) ethynylbenzene (0.22g, 1.13 mmol) in benzene (20 ml) were added in succession 1,2-cis-dichloroethene (0.32g, 3.9 mmol), n-butylamine (0.41g, 5.6 mmol),

Pd(PPh3)4 (65.2 mg, 0.05 mmol), CuI (21 mg, 0.11 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column

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chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.2 g

1 (67%) as white solid. H NMR (400 MHz, CDCl3):  7.58-7.49 (m, 6H), 7.40-7.37 (m, 3H), 6.50 (d,

13 J = 7.2 Hz, 1H), 6.14 (d, J = 7.2 Hz, 1H). C NMR (400 MHz, CDCl3): 131.68, 131.57, 128.76,

128.57, 128.44, 123.69, 122.98, 122.50, 112.02, 97.10, 91.55, 89.05, 85.10.

1,8-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (37):

To a solution of 32 (0.08g, 0.5 mmol) in benzene (20 ml) were added in succession 1,8-

dialkyncorannulene (0.05g, 0.16 mmol), n-butylamine (0.06g, 0.83 mmol), Pd(PPh3)4 (20 mg, 0.017 mmol), CuI (21 mg, 0.033 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography

(silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.2 g (67%) as

1 white solid. H NMR (400 MHz, CDCl3):  8.00 (s, 1H), 7.99 (s, 1H), 7.76 (d, J = 8.8Hz, 1H), 7.72

(d, J = 8.8Hz, 1H), 7.50-7.47 (m, 2H), 7.39-7.31 (broad peak, 3H). 6.28 (d, J = 10.4 Hz, 1H), 6.24

(d, J = 10.4 Hz, 1H).

1,8-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl]corannulene (38):

To a solution of 33 (0.15g, 0.6 mmol) in benzene (15 ml) were added in succession 1,8-

dialkyncorannulene (0.08g, 0.26 mmol), n-butylamine (0.09g, 1.34 mmol), Pd(PPh3)4 (31.6 mg, 0.026 mmol), CuI (4 mg, 0.06 mmol). The resulting solution was kept stirring at room temperature for overnight. Reaction mixture was filtered and obtained solid was triturated with cupious amounts of dichloromethane to remove any soluble impurity, which resulted the title compound 0.02 g (36%) as

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orange solid. 1H NMR (400 MHz, CDCl3):  1H NMR (400 MHz, CDCl3): 8.65 (d, J = 8.8 Hz,

2H), 8.41 (s, 1H), 8.03 (s, 1H), 7.93 (d, J = 8 Hz, 2H), 7.81 (d, J = 8.8 Hz, 2H), 7.70 (d, J = 8.8 Hz,

1H), 7.65 (s, 1H), 7.27 (m, 6H), 7.17 (m, 2H), 6.59 (d, J = 10.4 Hz, 1H), 6.41 (d, J = 10.4 Hz, 1H).

13 C NMR (400 MHz, CDCl3):

1,8-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (39):

To a solution of 34 (0.12g, 0.36 mmol) in benzene (15 ml) were added in succession 1,8-

dialkyncorannulene (0.05g, 0.16 mmol), n-butylamine (0.063g, 0.83 mmol), Pd(PPh3)4 (20 mg, 0.017 mmol), CuI (6.3 mg, 0.033 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography

(silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title compound 0.03 g (22%) as yellow solid. Later, gently boiled in dichloromethane, filtered and obtained 20 mg (13%) of yellow

1 solid. H NMR (400 MHz, CDCl3):  8.07 (s, 1H), 8.034 (s, 1H), 7.96 (d, J = 8.4 Hz, 1H), 7.92 (s,

1H), 7.80-7.38 (m, 10H), 7.59 (s, 1H), 7.40 (s, 1H), 6.26 (d, J = 10.8 Hz, 1H), 6.19 (d, J = 10.8 Hz, 1

13 H). C NMR (400 MHz, CDCl3):  135.76, 135.64, 135.44, 135.39, 135.22, 139.22, 134.86, 134.81,

131.80, 131.40, 130.89, 130.83, 130.68, 130.46, 130.04, 129.78, 127.35, 127.30, 127.20, 127.16,

126.94, 126.91, 126.87, 126.81, 126.77, 126.43, 125.87, 121.26, 120.81, 119.60, 119.24, 96.81, 96.28,

92.06, 91.73. HRMS: calculated for C72H30: 894.23 found [M+] 894.33.

1,8-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (41):

To a solution of 36 (0.13g, 0.51 mmol) in benzene (15 ml) were added in succession 1,8-

dialkyncorannulene (0.07g, 0.23 mmol), n-butylamine (0.085g, 1.17 mmol), Pd(PPh3)4 (27.1 mg, 114

0.023 mmol), CuI (6.3 mg, 0.047 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title compound 0.03

1 g (17%) as yellow solid. H NMR (400 MHz, CDCl3):  8.02 (s, 1H), 7.96 (s, 1H), 7.72-7.71 (m,

2H), 7.50-7.406 (m, 6H), 7.32 (s, 3H), 6.25 (d, J = 10.4 Hz, 1H), 6.09 (d, J = 10.4 Hz, 1H). 13C NMR

(400 MHz, CDCl3):  135.65, 135.00, 131.62, 131.48, 131.40, 131.12, 130.23, 128.30, 128.26, 127.44,

126.98, 126.85, 123.54, 122.99, 122.58, 121.34, 119.72, 119.34, 97.82, 95.96, 91.80, 91.78, 89.72,

89.51.

1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (42):

To a solution of 32 (0.05g, 0.05 mmol) in benzene (15 ml) were added in succession 1,5-

dialkyncorannulene (0.03g, 0.10 mmol), n-butylamine (0.06g, 0.5 mmol), Pd(PPh3)4 (11.6 mg, 0.010 mmol), CuI (4 mg, 0.021 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography

(silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 50% dichloromethane, which gave the title compound 0.02 g (36%) as

1 yellow solid. H NMR (400 MHz, CDCl3):  8.178 (d, J = 8.8 Hz, 1H), 8.172 (d, J = 8.8 Hz, 1H),

13 8.01 (s, 1H), 7.98 (s, 1H), 7.75 (d, J = 8.8 Hz, 2H), C NMR (400 MHz, CDCl3): 135.68, 135.46,

135.22, 134.95, 131.97, 131.77, 131.70, 131.49, 131.25, 130.94, 130.55, 130.30, 128.84, 128.46,

127.76, 127.55, 127.30, 126.98, 126.79, 123.07, 121.63, 121.39, 120.61, 120.08, 119.42, 98.08, 95.70,

91.50, 87.73. HRMS: calculated for C44H22: 550.17 found [M+] 550.2. 115

1,5-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl]corannulene (43):

To a solution of 33 (0.15g, 0.58 mmol) in toulene (15 ml) were added in succession 1,5-

dialkyncorannulene (0.08g, 0.26 mmol), n-butylamine (0.049g, 0.67 mmol), Pd(PPh3)4 (31 mg, 0.026 mmol), CuI (10.2 mg, 0.052 mmol). The resulting solution was kept stirring at room temperature for overnight. Later the mixture was filtered and washed twice with dichloromethane to remove soluble impurities. Title compound was obtained 0.02 g (36%) as orange insoluble solid. 1H NMR

(500 MHz, CDCl3):  8.64-8.61 (m, 4H), 8.41 (s, 1H), 8.389 (s, 1H), 8.052-8.022 (m, 2H), 7.98-7.92

(m, 7H), 7.88 (s, 1H), 7.71 (d, J = 8.5Hz, 1H), 7.66 (d, J = 8.5 Hz, 1H), 7.46 (d, J = 9Hz, 1H), 7.34-

7.30 (m, 5H), 7.23-7.18 (m, 4H), 6.54 (d, J = 10.5Hz, 2H), 6.40 (d, J = 10.5 Hz, 2H). 13C NMR (500

MHz, CS2 , CDCl3):  135.72, 135.51, 135.37, 134.95, 132.69, 132.62, 132.38, 131.42, 131.29, 131.02,

130.96, 130.41, 130.19, 128.55, 128.40, 127.52, 127.48, 127.05, 126.93, 126.87, 126.80, 126.75,

125.65, 126.60, 121.47, 121.25, 120.22, 120.18, 118.93, 116.85, 98.96, 96.24, 96.20, 95.20, 92.03.

HRMS: calculated for C60H30: 750.23 found [M+] 750.27.

1,5-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (44):

To a solution of 34 (0.09g, 0.26 mmol) in benzene (15 ml) were added in succession 1,5-

dialkyncorannulene (0.05g, 0.13 mmol), n-butylamine (0.075g, 0.1 mmol), Pd(PPh3)4 (15.5 mg, 0.013 mmol), CuI (5.1 mg, 0.025 mmol). The resulting solution was kept stirring at room temperature for overnight. Rotovap the crude mixture, pass it quickly through a silica flash plug to remove the catalyst and later titurate the solid with dichloromethane and filter to obtain title compound (20mg,

1 15%) as yellow solid. H NMR (500 MHz, CDCl3):  8.15 (d, J = 8.8 Hz, 1H), 8.07 (d, J = 9.2 Hz,

1H), 8.04 (s, 1H), 8.047 (d, J = 8.8 Hz, 1H), 7.99 (s, 1H), 7.93 (s, 1H), 7.93 (d, J = 8.4 Hz, 1H), 7.75

(s, 1H), 7.73-7.59 (m, 8H), 7.50-7.43 (m, 3H), 7.19-7.08 (m, 2H), 6.37 (m, 4H).

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1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (46):

To a solution of 36 (0.11g, 0.44 mmol) in benzene (15 ml) were added in succession 1,5-

dialkyncorannulene (0.06g, 0.20 mmol), n-butylamine (0.073g, 1.0 mmol), Pd(PPh3)4 (11.6 mg, 0.010 mmol), CuI (4 mg, 0.04 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography

(silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title compound 0.1 g (66%) as

1 yellow solid. H NMR (400 MHz, CDCl3):  8.17 (d, J = 8.8 Hz, 1H), 8.16 (d, J =8.8 Hz, 1H), 8.009

(s, 1H), 8.004 (s, 1H), 7.8 (d, J = 8.8 Hz, 1H), 7.75 (d, J = 8.8 Hz, 1H), 7.61-7.53 (m, 14 H), 7.37-

7.35 (m, 6H), 6.28-6.20 (m, 4H).

1,2,7,8-tetrakis-(4-phenyl-(Z)-1-buten-3-yne)corannulene (47):

To a solution of 32 (0.156g, 0.96 mmol) in benzene (15 ml) were added in succession 1,2,7,8-

tetraethnylcorannulene (76.4mg, 0.22 mmol), n-butylamine (0.032g, 4.4 mmol), Pd(PPh3)4 (51 mg,

0.044 mmol), CuI (16.7 mg, 0.084 mmol). The resulting solution was kept stirring at room temperature for overnight. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap. Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title compound 0.02

1 g (10%) as yellowish-red solid. H NMR (400 MHz, CDCl3):  8.14 (d, J = 8.8 Hz, 1H), 7.94 (s,

13 1H), 7.57(dd, J = 7.7 Hz, 2H), 7.45-7.28 (m, 10H), 6.24-6.11 (m, 4H). C NMR (400 MHz, CDCl3):

 134.99, 134.11, 132.128, 132.07, 131.40, 130.92, 128.79, 128.74, 128.36, 128.13, 127.40, 127.05,

117

124.93, 124.58, 123.00, 122.75, 120.37, 120.26, 119.44, 119.21, 98.45, 98.23, 97.28, 96.99, 94.63,

94.42, 87.85, 87.65.

1,2,7,8-tetrakis-(9-anthranyl-(Z)-3-buten-1-ynyl)corannulene (48):

To a solution of 33 (0.25g, 0.96 mmol) in benzene (15 ml) were added in succession 1,2,7,8-

tetraethnylcorannulene (81 mg, 0.23 mmol), n-butylamine (0.034g, 4.6 mmol), Pd(PPh3)4 (54 mg,

0.046 mmol), CuI (18 mg, 0.094 mmol). The resulting solution was kept stirring at room temperature for overnight. Under reduced pressure evaporate the solid and filter the contents and wash with cupious amounts of dichloromethane and hexane to remove soluble impurities. Title compound is hardly soluble hence can be obtained by simple filteration. Collected 0.02 g (6%), as

1 dark red solid. H NMR (400 MHz, CDCl3):  8.59 (d, J = 8.4 Hz, 2H), 8.48-8.45 (m, 2H), 8.34 (s,

1H), 8.24 (s, 1H), 7.93 (d, J = 8.8 Hz, 1H), 7.865 (d, J = 8.4 Hz, 2H), 7.74-7.71 (m, 2H), 7.251 (s,

1H), 7.21-7.16 (m, 5H), 7.05-7.03 (m, 4H), 6.924 (d, J = 8.4Hz, 1H), 6.32-6.18 (m, 4H). 13C NMR

(400 MHz, CDCl3):  134.98, 134.80, 133.911, 132.73, 132.65, 131.69, 131.23, 130.99, 130.87,

130.77, 128.55, 128.42, 127.67, 127.02, 126.98, 126.75, 126.72, 126.54, 125.59, 125.37, 125.16,

124.79, 120.31, 120.27, 119.03, 116.96, 116.73, 98.79, 98.72, 97.79, 97.53, 95.37, 95.19, 95.03.

HRMS: calculated for C100H50: 1250.39 found [M+] 1250.25.

Dehydro-1,8-corannuleno[16}annulene (49):

In a 25 ml one neck round bottom flask under the positive pressure of argon were added 31 (0.036g,

0.085 mmol) Pd(PPh3)4 (20 mg, 0.022 mmol), CuI (6.4mg, 0.03 mmol), piperidine (0.014g,

0.17mmol) in 4ml of THF and left for stirring for 30mts. A separate 25 ml flask was charged with

1,8-dialkyncorannulene (0.025g, 0.085mmol), piperidine (0.021g, 0.255 mmol) in 3ml of THF was allowed to stir for 30 mts. Later using a syringe pump solution of 1,8-dialkyncorannulene was added

118

to the other flask with a flow rate of 1ml/10mts. Reaction mixture was left for stirring overnight.

Quenched with 12M HCl and extracted with dichloromethane, dried over magnesium sulfate, rotovaped. Column chromatography (silica gel, hexane:dichloromethane) was performed starting with 100% hexane and ramping to 100% dichloromethane resulted in obtaining the target

1 compound in as fluorescent yellow solid (8mg, 10%). H NMR (400 MHz, CDCl3):  8.29 (s, 1H),

8.16 (s, 1H), 8.07 (s, 1H), 7.99 (d, J = 8.8 Hz, 2H), 7.83-7.77 (m, 4H), 7.06 (d, J = 8.8 Hz, 1H), 6.47

13 (d, J = 10.4 Hz, 1H), 6.37 (d, J = 10.4 Hz, 1H). C NMR (400 MHz, CDCl3):  135.99, 135.32,

134.87, 134.69, 134.57, 134.28, 134.07, 131.89, 131.52, 130.94, 130.53, 130.36, 130.00, 129.59,

129.45, 128.34, 127.91, 127.82, 127.70, 127.61, 127.53, 127.44, 127.00, 126.92, 121.91, 121.51,

120.79, 120.53, 120.16, 120.01, 96.74, 96.09, 92.11, 91.83, 88.91. HRMS: calculated for C76H28:

940.22 found [M+] 940.40.

1,1’-(4-chloro-3-buten-1,-ynyl)-8,8’-(3-hexene-1,5-diynyl)-,(Z,Z)-corannulene (50):

In a 25 ml one neck round bottom flask under the positive pressure of argon were added cis-1,2-

dichloroethene (0.03g, 0.3 mmol) Pd(PPh3)4 (0.070 g, 0.06 mmol), CuI (18mg, 0.09 mmol), piperidine (0.05g, 0.61mmol) in 10ml of THF and left for stirring for 30mts. A separate 25 ml flask was charged with 1,8-dialkyncorannulene (0.3g, 0.67 mmol), piperidine (0.14g, 2.01 mmol) in 3ml of

THF was allowed to stir for 30 mts. Later using a syringe pump solution of 1,8-dialkyncorannulene was added to the other flask with a flow rate of 1ml/10mts. Reaction mixture was left for stirring overnight. Mixture was acidified with 12M HCl and later extracted with dichloromethane, dried

over MgSO4 and rotovaped. Column chromatography (silica gel, hexane:dichloromethane) was performed initially with 100% hexane and ramping to 50:50 hexane:dichloromethane to obtain two compounds. NMR analysis indicated major compound to be 31 and whereas minor compound was

1 characterized to be 50 as yellow solid (8mg). H NMR (400 MHz, CDCl3):  8.23 (d, J = 8 Hz, 1H),

119

8.09 (s, 1H), 7.97 (s, 1H), 7.89(d, J =8 Hz, 1H), 7.78-7.72 (m, 3H), 7.53 (d, J = 8 Hz, 1H), 6.42 (d, J

= 8 Hz, 1H), 6.38 (s, 1H), 6.07 (d, J = 8 Hz, 1H). HRMS: calculated for C54H22Cl2: 741.67 found

[M+] 741.2.

1,8-bis-(3-triisopropylsily-l-ethynyl)corannulene (51):

To a mixture of 1,8-dialkyne corannulene (0.06 mg, 0.2mmol) in tetrahydrofuran (8 ml), n-BuLi (0.9 eqs, 1.6 M, 0.32 ml) was added at -78oC under argon. With addition of n-BuLi the color of the solution turned from golden yellow to dark and then turbid. After stirring the contents for 20 min. added tips-cl dropwise (3eqs). With addition of tips-cl the turbidness was disappearing and the color of the solution became lighter. Allowed to contents to stir for an additional 30 mins. Quenched the reaction with water (10 ml), extracted with dichloromethane, dried over magnesium sulfate and rotovaped. Column chromatography (silica gel, cyclohexane:dichloromethane) with a gradient elution from 100% cyclohexane to 100% dichloromethane was performed to obtain the desired

1 product 20 mg (23%). H NMR (400 MHz, CDCl3):  8.10 (s, 1H), 8.08 (s, 1H), 8.027 (d, J = 8.4

13 Hz, 2H), 8.01 (d, J = 8.4 Hz, 2H), 3.46 (s, 1H). 1.22-1.19 (m, 21 H). C NMR (400 MHz, CDCl3):

 135.66, 135.46, 135.42, 134.93, 132.51, 132.06, 131.46, 131.22, 130.32, 130.03, 127.48, 127.44,

127.04, 126.85, 126.73, 126.48, 121.79, 120.20, 104.78, 104.57, 95.49, 95.17, 81.73, 80.88.

1-ethynyl-8-[2-[tris(1-methylethyl)silyl]ethynylcorannulene (52):

In a 25 ml one neck round bottom flask under the positive pressure of argon were added cis-1,2-

dichloroethene (0.03g, 0.33 mmol) Pd(PPh3)4 (0.013 g, 0.011 mmol), CuI (4.1mg, 0.044 mmol), piperidine (0.05g, 0.66mmol) in 10ml of THF and left for stirring for 30mts. A separate 25 ml flask was charged with 51 (0.05g, 0.11 mmol), piperidine (0.03g, 0.33 mmol) in 3ml of THF was allowed to stir for 30 mts. Later using a syringe pump solution of 1,8-dialkyncorannulene was added to the

120

other flask with a flow rate of 1ml/10mts. Reaction mixture was left for stirring overnight.

Mixture was acidified with 12M HCl and later extracted with dichloromethane, dried over MgSO4 and rotovaped. Column chromatography (silica gel, hexane:dichloromethane) was performed initially with 100% hexane and ramping to 50:50 hexane:dichloromethane to obtain two compounds.

As expected the first compound eluted was the desired coupled product obtained as a yellow solid

(20mg, 35%), whereas the other compound when analyzed over NMR was characterized as a self

1 coupled product of starting material (51). H NMR (400 MHz, CDCl3):  8.20 (d, J = 8.8 Hz, 2H),

8.12 (d, J = 8.8 Hz, 2H), 8.036 (s, 1H), 8.030 (s, 1H), 7.78-7.75 (m, 4H), 6.59 (d, J = 8 Hz, 1H), 6.28

13 (d, J = 8Hz, 1H), 1.24-1.23 (s, 21H). C NMR (400 MHz, CDCl3):  135.73, 135.54, 135.51, 135.02,

132.09, 131.89, 131.49, 131.02, 130.38, 130.20, 128.95, 127.50, 127.45, 127.06, 126.92, 126.77,

126.69, 121.82, 120.92, 104.72, 95.67, 95.16, 87.10.

1,5-bis-(3-triisopropylsily-l-ethynyl)-corannulene (53):

To a mixture of 1,5-dialkyne corannulene (0.06 mg, 0.2mmol) in tetrahydrofuran (8 ml), n-BuLi (0.9 eqs, 1.6 M, 0.32 ml) was added at -78oC under argon. With addition of n-BuLi the color of the solution turned from golden yellow to dark and then turbid. After stirring the contents for 20 min. added tips-cl dropwise (3eqs). With addition of tips-cl the turbidness was disappearing and the color of the solution became lighter. Contents were stir for an additional 30 mins. Quenched the reaction with water (10 ml), extracted with dichloromethane, dried over magnesium sulfate and rotovaped.

Column chromatography (silica gel, cyclohexane:dichloromethane) with a gradient elution from

100% cyclohexane to 100% dichloromethane was performed to obtain the desired product 50 mg

1 13 (57%). H NMR (400 MHz, CDCl3):  8.03-7.89 (m, 4H), 7.80-7.72 (m, 4H), 3.4 (s, 1H). C NMR

(400 MHz, CDCl3): 135.50, 135.36, 135.08, 134.96, 131.97, 131.76, 131.39, 131.31, 131.16, 130.48,

130.26, 127.64, 127.41, 127.17, 126.86, 126.37, 126.31, 121.95, 121.68, 104.80, 104.76, 95.08, 95.04.

121

1-ethynyl-5-[2-[tris(1-methylethyl)silyl]ethynylcorannulene (54):

In a 25 ml one neck round bottom flask under the positive pressure of argon were added cis-1,2-

dichloroethene (0.025g, 0.26 mmol) Pd(PPh3)4 (0.010 g, 0.009 mmol), CuI (2mg, 0.006 mmol), 17 (40 mg, 0.088 mmol) n-BuNH2 (0.1g, 1.34mmol) in 15ml of toulene and left for stirring overnight.

Rotovaped the solvent under reduced pressure and performed column chromatograpy (silica gel, hexane:dichloromethane). The desired compound was obtained as a yellow solid (20mg, 44%). 1H

NMR (400 MHz, CDCl3):  8.09 (d, J = 8.8 Hz, 1H), 8.02-7.98 (m, 3H), 7.84-7.73 (m, 4H), 6.5 (d, J

= 7.6 Hz, 1H), 6.28-6.26 (d, J = 7.6 Hz, 1H), 1.25 (m, 22H).

1,5-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (55):

A 50 ml one neck round bottom flask was charged with Pd(PPh3)4 (0.15 g, 0.134 mmol), CuI (0.05g,

0.26 mmol), cis-1,2-dichloroethene (0.39 g, 4.02 mmol), piperidine (0.68g, 8.09 mmol) and tetrahydrofuran (15 ml) and allowed to stir for 30 min. In a separate 25 ml one neck round bottom flask charge 1,5-dialkyncorannulene (0.20g, 0.67 mmol), piperidine (0.17g, 2.01 mmol), and tetrahydrofuran (5 ml) in presence of nitrogen and let it stir for 30 min. After specified time, using a automated syringe add 1,5-dialkyncorannulene solution at a rate of 1ml/10 min. Let the reaction stir for overnight at room temperature. Quench the reaction with 12M HCl, wash with water, extract with dichloromethane, combine organic extraction and dry over magnesium sulfate, rotovap.

Column chromatography (silica gel, cyclohexane:dichloromethane) was performed using a gradient starting with 100% cyclohexane and ramping to 100% dichloromethane, which gave the title

1 compound 70 mg (25%) as yellow solid. H NMR (400 MHz, CDCl3):  8.11 (d, J = 8.8Hz, 1H),

8.10 (d, J = 8.8Hz, 1H), 8.00 (s, 1H), 7.99 (s, 1H), 7.83-7.73 (m, 4H), 6.57 (d, J = 8.0 Hz, 2H), 6.26

13 (d, J = 8.0, 2H). C NMR (400 MHz, CDCl3): 135.75, 135.30, 134.96, 131.96, 131.53, 131.17,

122

130.86, 130.48, 130.23, 128.99, 127.79, 127.58, 127.32, 126.99, 126.58, 126.55, 126.51, 121.27,

120.97, 112.18, 95.63, 95.58, 87.25, 87.21.

123

1H NMR of 2,7-dimethylnapthalene (3)

124

13C NMR of 2,7-dimethylnapthalene (3)

125

1H NMR of 3,8-dimethylacenapthaquinone (4)

126

13C NMR of 3,8-acenapthaquinone (4)

127

1H NMR of 1,6,7,10-tetramethylfluoranthene (5)

128

13C NMR of 1,6,7,10-tetramethylfluoranthene (5)

129

1H NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)

130

13C NMR of 1,6,7,10-tetrakis(dibromomethyl)fluoranthene (6)

131

1H NMR of corannulene (1)

132

13C NMR of corannulene (1)

133

1H NMR of bromocorannulene (8)

134

13C NMR of bromocorannulene (8)

135

1H NMR of 1,3,5,7,9-pentachlorocorannulene (9)

136

1H NMR of (4-bromophenyl)corannuleneacetylene (15)

137

13C NMR of (4-bromophenyl)corannuleneacetylene (15)

138

139

1H NMR of 1,8-diacetylcorannulene

140

13C NMR of 1,8-diacetylcorannulene

141

1H NMR of 1,5-diacetylcorannulene

142

13C NMR of 1,5-diacetylcorannulene

143

1H NMR of 1,8-dichlorovinylcorannulene

144

13C NMR of 1,8-dichlorovinylcorannulene

145

1H NMR of 1,5-dichlorovinylcorannulene

146

13C NMR of 1,5-dichlorovinylcorannulene

147

1H NMR of 1,8-diethynylcorannulene (16)

148

13C NMR of 1,8-diethynylcorannulene (16)

149

1H NMR of 1,5-diethynylcorannulene (17)

150

13C NMR of 1,5-diethynylcorannulene (17)

151

1H NMR of iodocorannulene (18)

152

1H NMR of ethynylcorannulene

153

13C NMR of ethynylcorannulene

154

1H NMR of 1,8-bis(phenynyl)corannulene (20)

155

13C NMR of 1,8-bis(phenynyl)corannulene (20)

156

MALDI-TOF of 1,8-bis(phenynyl)corannulene (20)

157

1H NMR of 1,5-bis(phenynyl)corannulene (21)

158

13C NMR of 1,5-bis(phenynyl)corannulene (21)

159

MALDI-TOF of 1,5-bis(phenynyl)corannulene (21)

160

1H NMR of 1,8-bis(9-anthranyl)corannulene (22)

161

13C NMR of 1,8-bis(9-anthranyl)corannulene (22)

162

1H NMR of 1,5-bis(9-anthranyl)corannulene (23)

163

MALDI-TOF of 1H NMR of 1,5-bis(9-anthranyl)corannulene (23) 164

1H NMR of 1,8-bis(corannulenyl)corannulene (24)

165

MALDI-TOF of 1,8-bis(corannulenyl)corannulene (24)

166

1H NMR of 1,5-bis(corannulenyl)corannulene (25)

167

MALDI-TOF of 1,5-bis(corannulenyl)corannulene (25)

168

1H NMR of 1,8-bis(phenylacetylenecorannuenyl)corannulene (26)

169

MALDI-TOF of 1,8-bis(phenylacetylenecorannuenyl)corannulene (26)

170

1H NMR for 1,2,7,8-tetrakis(1-ethynyl)corannulene (27)

171

1H NMR of 1,2,7,8-tetrakis[2-(trimethylsilyl)ethynyl]corannulene (28)

172

MALDI-TOF of 1,2,7,8-tetrakis[2-(trimethylsilyl)ethynyl]corannulene (28) 173

1H NMR of 1,2,7,8-tetrakis(2-phenylethynyl)corannulene (29)

174

MALDI-TOF of 1H NMR of 1,2,7,8-tetrakis(2-phenylethynyl)corannulene (29)

175

1H NMR of 9, 9’, 9’’, 9’’’- (1,2,7,8-corannulenetetra-2, 1-ethynetetrayl)tetrakis-anthracene (30)

176

9, 9’, 9’’, 9’’’- (1,2,7,8-corannulenetetra-2, 1-ethynetetrayl)tetrakis-anthracene (30) 177

1H NMR of 1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31)

178

13C NMR of 1,8-bis(4-chloro-3-buten-1-ynyl)-(Z, Z)-corannulene (31)

179

1H NMR of 1-chloro-4-phenyl-(Z)-1-buten-3-yne (32)

180

13C NMR of 1-chloro-4-phenyl-(Z)-1-buten-3-yne (32)

181

1H NMR of 9-(4-chloro-3-buten-1-ynyl)-(Z)-anthracene (33)

182

13C NMR of 9-(4-chloro-3-buten-1-ynyl)-(Z)-anthracene (33)

183

1H NMR of 1-chloro-4-corannulene-(Z)-1-buten-3-yne (34)

184

13C NMR of 1-chloro-4-corannulene-(Z)-1-buten-3-yne (34)

185

1H NMR of 1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylcorannynyl)-benzene (35)

186

13C NMR of 1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylcorannynyl)-benzene (35)

187

1H NMR of 1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylphenyl)-benzene (36)

188

13C NMR of 1-[(3Z)-4-chloro-3-buten-1-ynyl]-4-(ethnynylphenyl)-benzene (36)

189

1H NMR of 1,8-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (37)

190

1H NMR of 1,8-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (38)

191

1H NMR of 1,8-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (39)

192

13C NMR of 1,8-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (39)

193

MALDI-TOF of of 1,8-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (39)

194

1H NMR of 1,8-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (41)

195

13C NMR of 1,8-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (41)

196

1H NMR of 1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (42)

197

13C NMR of 1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (42)

198

MALDI-TOF of 1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (42) 199

1H NMR of 1,5-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (43)

200

13C NMR of 1,5-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (43)

201

2D-NMR (COSY) of of 1,5-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (43)

202

MALDI-TOF of 1,5-bis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (43)

203

1H NMR of 1,5-bis[(3Z)-4-corannunylethynyl-3-buten-1-yn-1-yl]corannulene (44)

204

1H NMR of 1,5-bis[(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl]corannulene (46)

205

1H NMR of 1,2,7,8-tetrakis([(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl])corannulene (47)

206

13C NMR of 1,2,7,8-tetrakis([(3Z)-4-phenylethynyl-3-buten-1-yn-1-yl])corannulene (47)

207

1H NMR of 1,2,7,8-tetrakis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (48)

208

13C NMR of 1,2,7,8-tetrakis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (48)

209

MALDI-TOF of of 1,2,7,8-tetrakis([9-[(3Z)-4-anthranyl-3-buten-1-yn-1-yl])corannulene (48) 210

1H NMR of Dehydro-1,8-corannuleno[16]annulene (49)

211

13C NMR of Dehydro-1,8-corannuleno[16]annulene (49)

212

MALDI-TOF of Dehydro-1,8-corannuleno[16]annulene (49)

213

1H NMR of 1,1’-(4-chloro-3-buten-1,-ynyl)-8,8’-(3-hexene-1,5-diynyl)-,(Z,Z)-corannulene (50)

214

MALDI-TOF of 1,1’-(4-chloro-3-buten-1,-ynyl)-8,8’-(3-hexene-1,5-diynyl)-,(Z,Z)-corannulene (50)

215

1H NMR of 1-ethynyl-8-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (51)

216

13C NMR of 1-ethynyl-8-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (51)

217

1H NMR of 1-ethynyl[4-chloro-(3Z)]-8-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (52)

218

1H NMR of 1-ethynyl[4-chloro-(3Z)]-8-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (52)

219

1H NMR of 1-ethynyl-5-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (53)

220

13C NMR of 1-ethynyl-5-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (53)

221

1H NMR of 1-ethynyl[4-chloro-(3Z)]-5-[2-[tris(1-methylethyl)silyl]ethynyl]corannulene (54)

222

1H NMR of 1,5-bis(dichloroenyne)corannulene (55)

223

13C NMR of 1,5-bis(dichloroenyne)corannulene (55)

224