DOCSLIB.ORG

Octapodal Corannulene Porphyrin-Based Assemblies: Allosteric Behavior in Fullerene Hosting

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Octapodal Corannulene Porphyrin-Based Assemblies: Allosteric Behavior in Fullerene Hosting pubs.acs.org/joc Article Octapodal Corannulene Porphyrin-Based Assemblies: Allosteric Behavior in Fullerene Hosting ́ Sergio Ferrero, Hectoŕ Barbero, Daniel Miguel, Rauĺ García-Rodríguez,* and Celedonio M. Alvarez* Cite This: J. Org. Chem. 2020, 85, 4918−4926 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: An octapodal corannulene-based supramolecular system has been prepared by introducing eight corannulene moieties in a porphyrin scaffold. Despite the potential of this double picket fence porphyrin for double- tweezer behavior, NMR titrations show exclusive formation of 1:1 adducts. ffi ± × The system exhibits very strong a nity for C60 and C70 (K1 = (2.71 0.08) 104 and (2.13 ± 0.1) × 105 M−1, respectively), presenting selectivity for the latter. Density functional theory (DFT) calculations indicate that, in addition to the four corannulene units, the relatively flexible porphyrin tether actively participates in the recognition process, resulting in a strong synergistic effect. This leads to a very strong interaction with C60, which in turn also induces a large structural change on the other face (second potential binding site), leading to a negative allosteric effect. We also introduced Zn2+ in the porphyrin core in an attempt to modulate its flexibility. The resulting metalloporphyrin ff also displayed single-tweezer behavior, albeit with slightly smaller binding constants for C60 and C70, suggesting that the e ect of the coordination of fullerene to one face of our supramolecular platform was still transmitted to the other face, leading to the deactivation of the second potential binding site. ■ INTRODUCTION buckybowl, has unique properties not seen in planar π- Since its establishment, supramolecular chemistry1 has been conjugated compounds arising from its nonplanarity, which enables it to form supramolecular assemblies with fullerenes used to design and develop new entities with a wide range of 10 applications in various areas of science. Inspired by nature, an through noncovalent interactions. Its net dipolar moment, interesting topic in supramolecular chemistry is the develop- together with its exceptional concave−convex complementary 11 ment of artificial receptors that echo the allosteric control of for π−π stacking, allows it to strongly interact with fullerenes more complex biological systems.2 The term allosterism via the well-known “ball-and-socket” interactions. Not describes structural changes that occur upon the coordination surprisingly, corannulene has proven to be a very useful Downloaded via UNIV DE VALLADOLID on June 19, 2020 at 08:57:53 (UTC). of a substrate to a binding site (allosteric site) of the host.3 The motif for the design of various materials and a very attractive information associated with the first event is transmitted to a building block in the construction of organic electronic different binding site by a change in the conformation, which devices, including solar cells and nonlinear optical materi- See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. can lead to activation (positive cooperation) or deactivation als.8b,12 In particular, it has played a central role in the design (negative cooperation or inhibition) of the binding site. This of efficient receptors for fullerenes. The use of corannulene as a represents a very useful tool to control the coordination of building block, however, has been limited by its tedious different sites, and not surprisingly, it has attracted a great deal synthesis, which requires a large number of steps. Considerable 4 of attention in the supramolecular chemistry community. efforts have been devoted to improving the current synthetic Additionally, carbon nanostructures, particularly fullerenes, methods as well as to its derivatization with suitable functional have found a variety of applications in supramolecular groups to enable its use in producing more complex chemistry due to their unique structures and electronic architectures. Although a single pristine corannulene unit 5 ff properties. Great e orts have been made to construct cannot bind fullerene strongly enough for the corannulene− supramolecular assemblies that host fullerenes through weak intermolecular forces6 to develop high-performance devices, in particular, photoelectrochemical devices and solar cells. Received: January 10, 2020 Size and shape complementarity is crucial to achieving Published: March 10, 2020 efficient supramolecular host−guest binding. In this regard, bowl-shaped aromatic hydrocarbons or buckybowls7 are attracting increasing attention and finding new applications in materials science.8 Corannulene,9 the most-interesting © 2020 American Chemical Society https://dx.doi.org/10.1021/acs.joc.0c00072 4918 J. Org. Chem. 2020, 85, 4918−4926 The Journal of Organic Chemistry pubs.acs.org/joc Article Figure 1. Development of systems bearing different numbers of corannulene units. 13 3 −1 fullerene inclusion complex to be observed in solution, the 10 M (C60) for D and E systems, respectively) seem to stem careful design of molecules incorporating two corannulene from their much greater flexibility, which favors self-interaction units has proven to be a very useful strategy to improve and consequently notably reduces their interaction with corannulene−fullerene interactions. fullerenes. These examples highlight the importance of the Researchers have long focused on improving the strength preorganization and morphology of the supramolecular and selectivity of fullerene receptors. The historical evolution platform in fullerene association, which can be as important of multicorannulene “pincer” systems is shown in Figure 1, as the number of corannulene units attached. Therefore, to which shows selected examples. The first and most obvious increase host−guest surface contact, careful design of fullerene such pincer systems were based on two corannulene units and receptors is required in addition to increasing the number of 18 have had a great impact on supramolecular−fullerene corannulene units. interactions. In particular, Sygula’s buckycatcher I (Figure 1, We have recently explored the use of porphyrin-based ff A)14 represented a breakthrough as the first example of the systems as molecular sca olds for fullerene hosting. Although formation of a stable inclusion complex with fullerene and porphyrins and fullerenes can interact, the presence of only a × 3 −1 single porphyrin core usually results in interactions with presented association constants of 2.78 10 M (C60) and 19 × 3 −1 fullerenes that are too weak to be observed in solution. These 3.03 10 M (C70) in toluene at 298 K. Sygula subsequently engineered the tether between the two corannulene moieties to systems are relatively rigid and allow for the active improve the preorganization of the host and the fullerene participation of the tether in the supramolecular interaction guest, expanding the buckycatcher family (buckycatchers II and are therefore ideally suited to host fullerenes. We and III, not depicted in the figure)15 and improving the C envisaged that a meso-substituted tetraaryl porphyrin core 60 would be an ideal scaffold for supramolecular interactions and binding constant by an order of magnitude. We developed a prepared the meta-substituted porphyrin F with four platinum-based system with two corannulene moieties, which 18b fi corannulene units. However, while this tetrakis-corannulene was the rst system capable of discriminating C60 over C70 (B); porphyrin clip was able to associate with C60, F was present as subsequently, Chen et al. achieved outstanding discrimination adifficult-to-analyze mixture of four atropisomers resulting (K /K = 230:1) using the two-corannulene moiety system C70 C60 from the orientation of the four corannulene units above and C.16 In contrast, systems bearing tris-corannulene clips,17 such below the porphyrin plane. These atropisomers could not be as D and E, have not had the same success as systems bearing separated, resulting in a complex system and marked decrease two corannulene units due to their lower ability to associate in the C60 binding ability. In a recent work, we subsequently fullerenes. The lower binding constants observed for these circumvented the formation of atropisomers by introducing × 3 −1 × tripodal systems (K1 = 1.50 10 M (C60) and K1 = 2.19 eight pyrene units at the meta positions of the tetraaryl 4919 https://dx.doi.org/10.1021/acs.joc.0c00072 J. Org. Chem. 2020, 85, 4918−4926 The Journal of Organic Chemistry pubs.acs.org/joc Article a porphyrin system.20 This resulted in a double tweezer with a Scheme 1. Synthesis of 2H-POctaCor remarkably high association for fullerenes, despite the poor shape complementarity between pyrene and fullerenes, due to the synergistic effect between the porphyrin tether and the pyrene units. As the combination of well-organized corannu- lene fragments and a porphyrin tether resulted in synergistic effects and good fullerene hosting ability, in the present work, we explore the possibility of introducing eight corannulene units on a single porphyrin core (Figure 1, present work) and their impact on the fullerene affinity and selectivity of the new octapodal corannulene supramolecular platform (which contains the most corannulene moieties on a single-molecule receptor to date). The effect of the association on the geometry of the double tweezer (allosteric effect) and its impact on a second association event, which determines whether the receptor will exhibit double- or
Load more

Recommended publications
  • May-June 2013 OUTLOOK on Volume 35 No
    CHEMISTRY International The News Magazine of IUPAC May-June 2013 OUTLOOK ON Volume 35 No. 3 LATIN AMERICA Neglected Tropical Diseases INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY Green Chemistry in Teaching From the Editor CHEMISTRY International ay is a month of many celebrations. As we have mentioned several Mtimes before in CI, 20 May is World Metrology Day, which com- The News Magazine of the International Union of Pure and memorates the signing by representatives of 17 nations of The Metre Applied Chemistry (IUPAC) Convention on that day in 1875. This year, the theme is “Measurements in Daily Life”—see more at www.worldmetrologyday.org. www.iupac.org/publications/ci While living in the states, but having grown up in Belgium, I have found that measurements in my daily life can be quite bewildering. A simple Managing Editor: Fabienne Meyers length mentioned in inches, a travel distance Production Editor: Chris Brouwer referred to in miles, a quantity in a cook book Design: pubsimple specified in spoons or cups, or my own weight blurred in pounds on my bathroom scale make All correspondence to be addressed to: no sense to me. And, it is beyond me that this Fabienne Meyers “New World” is stuck in a nonmetric system. If IUPAC, c/o Department of Chemistry on 20 May I can convince just one friend that Boston University SI is the way to go, even for daily usage, it is Metcalf Center for Science and Engineering worth celebrating! 590 Commonwealth Ave. There are many more international and world days in May, several that Boston, MA 02215, USA are even recognized by the UN or UNESCO.
    [Show full text]
  • Molecular Tweezers for Lysine and Arginine –
    Volume 52 Number 76 1 October 2016 Pages 11307–11452 ChemComm Chemical Communications www.rsc.org/chemcomm ISSN 1359-7345 FEATURE ARTICLE Thomas Schrader, Gal Bitan and Frank-Gerrit Klärner Molecular tweezers for lysine and arginine – powerful inhibitors of pathologic protein aggregation ChemComm View Article Online FEATURE ARTICLE View Journal | View Issue Molecular tweezers for lysine and arginine – powerful inhibitors of pathologic protein aggregation Cite this: Chem. Commun., 2016, 52, 11318 a b a Thomas Schrader,* Gal Bitan* and Frank-Gerrit Kla¨rner* Molecular tweezers represent the first class of artificial receptor molecules that have made the way from a supramolecular host to a drug candidate with promising results in animal tests. Due to their unique structure, only lysine and arginine are well complexed with exquisite selectivity by a threading mechanism, which unites electrostatic, hydrophobic and dispersive attraction. However, tweezer design must avoid self-dimerization, self-inclusion and external guest binding. Moderate affinities of molecular tweezers towards sterically well accessible basic amino acids with fast on and off rates protect normal proteins from potential interference with their biological function. However, the early stages of Received 2nd June 2016, abnormal Ab, a-synuclein, and TTR assembly are redirected upon tweezer binding towards the Accepted 27th July 2016 generation of amorphous non-toxic materials that can be degraded by the intracellular and extracellular Creative Commons Attribution-NonCommercial 3.0 Unported Licence. DOI: 10.1039/c6cc04640a clearance mechanisms. Thus, specific host–guest chemistry between aggregation-prone proteins and lysine/arginine binders rescues cell viability and restores animal health in models of AD, PD, and www.rsc.org/chemcomm TTR amyloidosis.
    [Show full text]
  • Synthesis and Properties of Corannulene Derivatives: Journey to Materials Chemistry and Chemical Biology
    Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2008 Synthesis and properties of corannulene derivatives: journey to materials chemistry and chemical biology Hayama, Tomoharu Abstract: Corannulene, also called as [5]-circulene, is a C20H10 fragment of buckminsterfullerene, C60. The most interesting property of corannulene is probably its bowl structure and bowl-to-bowl inversion. The unique curvature has many possiblities for applications in different fields. Today, large-scale synthesis of corannulene is possible and thus, the time has come to exploit its physical properties. This disserta- tion is divided into four areas: 1) efficient synthesis of sym-pentaarylsubstituedcorannulene derivatives, 2) solvent effect on the bowl inversion, 3) development of the method for solution-phase nanotube syn- thesis, and 4) designing a corannulene-based synthetic receptor. sym-pentaarylsubstituedcorannulenes are quite attractive compounds because of their five-fold symmetry and curvature. The efficient synthesis has been accomplished from sym-pentachlorocorannulene with the coupling reaction using N-heterocyclic carbene ligands in a moderately good yield in spite of its five low-reactive chlorides. The inversion energies of some sym-pentaarylsubstituedcorannulenes have been investigated in different types of sol- vent. The variable temperature 1H-NMR spectra were measured, and line shape analysis or coalescence approximation were used to evaluate the rate parameters. This experiment suggested endo-group inter- actions of those compounds and shows influences of solvent polarity or volume on the inversion energies. In addition, the bowl depths will also be compared and discussed using the crystallographic structural data. The high-energy per-ethynylated polynuclear compound decapentynyl-corannulene has been pre- pared via aryl-alkyne coupling chemistry of decachlorocorannulene.
    [Show full text]
  • Polycyclic Aromatic Hydrocarbon Structure Index
    NIST Special Publication 922 Polycyclic Aromatic Hydrocarbon Structure Index Lane C. Sander and Stephen A. Wise Chemical Science and Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-0001 December 1997 revised August 2020 U.S. Department of Commerce William M. Daley, Secretary Technology Administration Gary R. Bachula, Acting Under Secretary for Technology National Institute of Standards and Technology Raymond G. Kammer, Director Polycyclic Aromatic Hydrocarbon Structure Index Lane C. Sander and Stephen A. Wise Chemical Science and Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 This tabulation is presented as an aid in the identification of the chemical structures of polycyclic aromatic hydrocarbons (PAHs). The Structure Index consists of two parts: (1) a cross index of named PAHs listed in alphabetical order, and (2) chemical structures including ring numbering, name(s), Chemical Abstract Service (CAS) Registry numbers, chemical formulas, molecular weights, and length-to-breadth ratios (L/B) and shape descriptors of PAHs listed in order of increasing molecular weight. Where possible, synonyms (including those employing alternate and/or obsolete naming conventions) have been included. Synonyms used in the Structure Index were compiled from a variety of sources including “Polynuclear Aromatic Hydrocarbons Nomenclature Guide,” by Loening, et al. [1], “Analytical Chemistry of Polycyclic Aromatic Compounds,” by Lee et al. [2], “Calculated Molecular Properties of Polycyclic Aromatic Hydrocarbons,” by Hites and Simonsick [3], “Handbook of Polycyclic Hydrocarbons,” by J. R. Dias [4], “The Ring Index,” by Patterson and Capell [5], “CAS 12th Collective Index,” [6] and “Aldrich Structure Index” [7]. In this publication the IUPAC preferred name is shown in large or bold type.
    [Show full text]
  • Design, Synthesis, and Testing of Bis-Corannulene Receptors for Fullerenes Based On
    Automated Template C: Created by James Nail 2013V2.1 Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers By Peumie Luckshika Abeyratne Kuragama A Dissertation Submitted to the Faculty of Mississippi State University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Chemistry in the Department of Chemistry Mississippi State, Mississippi December 2015 Copyright by Peumie Luckshika Abeyratne Kuragama 2015 Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers By Peumie Luckshika Abeyratne Kuragama Approved: ____________________________________ Andrzej Sygula (Major Professor) ____________________________________ Keith T. Mead (Committee Member) ____________________________________ Todd E. Mlsna (Committee Member) ____________________________________ Dongmao Zhang (Committee Member) ____________________________________ Stephen C. Foster (Graduate Coordinator/Committee Member) ____________________________________ R. Gregory Dunaway Dean College of Arts & Sciences Name: Peumie Luckshika Abeyratne Kuragama Date of Degree: December 11, 2015 Institution: Mississippi State University Major Field: Chemistry Major Professor: Andrzej Sygula Title of Study: Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers Pages in Study: 141 Candidate for Degree of Doctor of Philosophy The discovery of the new allotropic forms of elemental carbon (e.g. fullerenes and carbon nanotubes)
    [Show full text]
  • Monoradicals and Diradicals of Dibenzofluoreno[3,2-B]Fluorene Isomers: Mechanisms of Electronic Delocalization
    pubs.acs.org/JACS Article Monoradicals and Diradicals of Dibenzofluoreno[3,2‑b]fluorene Isomers: Mechanisms of Electronic Delocalization Hideki Hayashi,○ Joshua E. Barker,○ Abel Cardenaś Valdivia,○ Ryohei Kishi, Samantha N. MacMillan, Carlos J. Gomez-Garć ía, Hidenori Miyauchi, Yosuke Nakamura, Masayoshi Nakano,* Shin-ichiro Kato,* Michael M. Haley,* and Juan Casado* Cite This: J. Am. Chem. Soc. 2020, 142, 20444−20455 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: The preparation of a series of dibenzo- and tetrabenzo-fused fluoreno[3,2-b]fluorenes is disclosed, and the diradicaloid properties of these molecules are compared with those of a similar, previously reported series of anthracene-based diradicaloids. Insights on the diradical mode of delocalization tuning by constitutional isomerism of the external naphthalenes has been explored by means of the physical approach (dissection of the electronic properties in terms of electronic repulsion and transfer integral) of diradicals. This study has also been extended to the redox species of the two series of compounds and found that the radical cations have the same stabilization mode by delocalization that the neutral diradicals while the radical anions, contrarily, are stabilized by aromatization of the central core. The synthesis of the fluorenofluorene series and their characterization by electronic absorption and vibrational Raman spectroscopies, X-ray diffraction, SQUID measurements, electrochemistry, in situ UV−vis−NIR absorption spectroelectro- chemistry, and theoretical calculations are presented. This work attempts to unify the properties of different series of diradicaloids in a common argument as well as the properties of the carbocations and carbanions derived from them.
    [Show full text]
  • Synthesis of an Unsymmetrically Pentafunctionalized Corannulene Derivative (Part I) Synthesis of Platinum and Ethynyl-Platinum Corannulenes (Part II)
    Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2012 Synthesis of an Unsymmetrically Pentafunctionalized Corannulene Derivative (Part I) Synthesis of Platinum and Ethynyl-Platinum Corannulenes (Part II) Maag, Roman M Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-164179 Dissertation Published Version Originally published at: Maag, Roman M. Synthesis of an Unsymmetrically Pentafunctionalized Corannulene Derivative (Part I) Synthesis of Platinum and Ethynyl-Platinum Corannulenes (Part II). 2012, University of Zurich, Faculty of Science. Part I: Synthesis of an Unsymmetrically Pentafunctionalized Corannulene Derivative and Part II: Synthesis of Platinum and Ethynyl-Platinum Corannulenes Dissertation zur Erlangung der naturwissenschaftlichen Doktorwurde¨ Dr. sc. nat. vorgelegt der Mathematisch-naturwissenschaftlichen Fakult¨at der Universit¨at Zurich¨ von Roman M. Maag von Winkel ZH Promotionskommitee: Prof. Dr. Jay S. Siegel (Vorsitz) Prof. Dr. Kim K. Baldridge Prof. Dr. Cristina Nevado Prof. Dr. Roger Alberto Zurich,¨ 2012 Abstract of the Dissertation Part I: Synthesis of an Unsymmetrically Pentafunctionalized Corannulene Derivative and Part II: Synthesis of Platinum and Ethynyl-Platinum Corannulenes by Roman M. Maag University of Zurich, 2012 Prof. Dr. Jay S. Siegel, Chair Corannulene (C20H10) is a polyaromatic hydrocarbon that can be considered as the smallest fragment of Buckminsterfullerene exhibiting a curved surface. Among the in- teresting properties of corannulene are rapid bowl inversion and esthetically appealing fivefold symmetry (C5v), which is rare in chemistry. Whereas the first synthesis in 1968 only afforded milligram quantities, several improvements in the synthetic strategy finally culminated in the development of an efficient process which today furnishes corannulene in kilogram quantities.
    [Show full text]
  • On-Surface Synthesis of a Nitrogen-Embedded Buckybowl with Inverse Stoneâ
    ARTICLE DOI: 10.1038/s41467-018-04144-5 OPEN On-surface synthesis of a nitrogen-embedded buckybowl with inverse Stone–Thrower–Wales topology Shantanu Mishra1, Maciej Krzeszewski2, Carlo A. Pignedoli1, Pascal Ruffieux 1, Roman Fasel 1,3 & Daniel T. Gryko2 π 1234567890():,; Curved -conjugated polycyclic aromatic hydrocarbons, buckybowls, constitute an important class of materials with wide applications in materials science. Heteroatom doping of buck- ybowls is a viable route to tune their intrinsic physicochemical properties. However, synthesis of heteroatom-doped buckybowls is a challenging task. We report on a combined in-solution and on-surface synthetic strategy toward the fabrication of a buckybowl containing two fused nitrogen-doped pentagonal rings. We employ ultra-high-resolution scanning tunneling microscopy and spectroscopy, in combination with density functional theory calculations to characterize the final compound. The buckybowl contains a unique combination of non- hexagonal rings at its core, identified as the inverse Stone–Thrower–Wales topology, resulting in a distinctive bowl-opening-down conformation of the buckybowl on the surface. Our controlled design of non-alternant, heteroatom-doped polycyclic aromatic frameworks with established bottom-up fabrication techniques opens new opportunities in the synthesis of carbon nanostructures with the perspective of engineering properties of graphene-based devices. 1 Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf 8600, Switzerland. 2 Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44-52, Warsaw 01-224, Poland. 3 Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern 3012, Switzerland. Correspondence and requests for materials should be addressed to R.F. (email: [email protected]) or to D.T.G.
    [Show full text]
  • DFT Study of Five-Membered Ring Pahs
    DFT study of five-membered ring PAHs Gauri Devi1, Mridusmita Buragohain1*, Amit Pathak2, 1Department of Physics, Tezpur University, Tezpur 784028, India, [email protected], *Corresponding author 2Department of Physics, Banaras Hindu University, Varanasi 221 005, India ([email protected]) Abstract This work reports a ‘Density Functional Theory’ (DFT) calculation of PAH molecules with a five-member ring to determine the expected region of infrared features. It is highly possible that fullerene molecule might be originated from five-membered ring PAH molecules in the ISM. Effect of ionization and protonation on five-membered ring PAH molecule is also discussed. A detail vibrational analysis of five-membered ring PAH molecule has been reported to further compare with observations and to identify any observational counterpart. Keywords: PAH, Interstellar molecules, IR spectra, Unidentified infrared bands, Astrochemistry INTRODUCTION Polycyclic Aromatic Hydrocarbons(PAHs) are suspected to beoneofthe stableand largest aromatic compounds present in the interstellar medium (ISM) of the Milky Way and external galaxies. The ubiquitous presence of PAHs has been established through numerous observations of the unidentified infrared (UIR) emission bands in the mid- IR (Tielens, 2008, and references therein). PAH molecules, being stable, can survive acute conditions of the ISM in its regular as well as in ionized or de-hydrogenated phase. These properties help to understand the total carbon budget of the universe. PAHs, because of their ubiquitous presence, may provide some clues to some of the hitherto unsolved problems of astronomical spectroscopy, e.g. the 3.4 µm absorp- arXiv:1902.10464v1 [astro-ph.GA] 27 Feb 2019 tion feature (Sellgren et al., 1994), the far-UV steep of the interstellar extinction curve (Li and Draine, 2001), the 217.5 nm bump (Henning and Salama, 1998) and the diffuse interstellar bands (Salama et al., 1999) that appear as absorption features in the visible region of the interstellar extinction curve.
    [Show full text]
  • ROTATIONAL SPECTRA of SMALL Pahs: ACENAPHTHENE, ACENAPHTHYLENE, AZULENE, and FLUORENE S
    The Astrophysical Journal, 662:1309 Y 1314, 2007 June 20 A # 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A. ROTATIONAL SPECTRA OF SMALL PAHs: ACENAPHTHENE, ACENAPHTHYLENE, AZULENE, AND FLUORENE S. Thorwirth,1, 2, 3 P. Theule´,2, 3, 4 C. A. Gottlieb,2, 3 M. C. McCarthy,2, 3 and P. Thaddeus2, 3 Received 2007 January 5; accepted 2007 March 7 ABSTRACT Pure rotational spectra of four small polycyclic aromatic hydrocarbons have been observed by Fourier transform microwave spectroscopy of a molecular beam in the frequency range from 7 to 37 GHz. Initial searches for acenaphthene (C12H10), acenaphthylene (C12H8), and fluorene (C13H10) were guided by quantum chemical calculations performed at the B3LYP/cc-pVTZ level of theory. All three molecules exhibit b-type rotational spectra and are calculated to be moderately polar, with dipole moments of 0.3Y0.9 D. Close agreement (to better than 1%) between the calculated equilibrium and experimentally derived ground-state rotational constants is achieved. Selected transitions of acenaphthene and fluorene have also been measured in the 3 mm region by conventional free-space absorption spectroscopy, as have transitions of the previously studied azulene (C10H8). The data presented here facilitate deep radio astronomical searches with large radio telescopes. Subject headingsg: astrochemistry — ISM: molecules — molecular data Online material: machine-readable tables 1. INTRODUCTION (C12H8; molecule 2), and fluorene (C13H10; molecule 3) have been obtained for the first time employing Fourier transform The mid-infrared spectra from 3 to 20 m of many astronom- microwave (FTM) spectroscopy. Centimeter-wave transitions ical objects are dominated by emission features usually referred of azulene (molecule 4) were also measured, complementing the to as the unidentified infrared bands (UIRs).
    [Show full text]
  • Mechanochemical Transformation of Planar Polyarenes to Curved Fused-Ring Systems ✉ ✉ Teoh Yong1,2, Gábor Báti1,2, Felipe García 1 & Mihaiela C
    ARTICLE https://doi.org/10.1038/s41467-021-25495-6 OPEN Mechanochemical transformation of planar polyarenes to curved fused-ring systems ✉ ✉ Teoh Yong1,2, Gábor Báti1,2, Felipe García 1 & Mihaiela C. Stuparu 1 The transformation of planar aromatic molecules into π-extended non-planar structures is a challenging task and has not been realized by mechanochemistry before. Here we report that mechanochemical forces can successfully transform a planar polyarene into a curved geo- 1234567890():,; metry by creating new C-C bonds along the rim of the molecular structure. In doing so, mechanochemistry does not require inert conditions or organic solvents and provide better yields within shorter reaction times. This is illustrated in a 20-minute synthesis of cor- annulene, a fragment of fullerene C60, in 66% yield through ball milling of planar tetra- bromomethylfluoranthene precursor under ambient conditions. Traditional solution and gas-phase synthetic pathways do not compete with the practicality and efficiency offered by the mechanochemical synthesis, which now opens up a new reaction space for inducing curvature at a molecular level. 1 Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore. ✉ 2These authors contributed equally: Teoh Yong, Gábor Báti. email: [email protected]; [email protected] NATURE COMMUNICATIONS | (2021) 12:5187 | https://doi.org/10.1038/s41467-021-25495-6 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-25495-6 he synthesis of strained aromatic molecules from strain-free Br Br precursors is a challenging task. This requires the natural T 2 trigonal planar geometry of the sp -hybridised carbon atoms to become non-planar.
    [Show full text]
  • Effect of Molecular Clips and Tweezers on Enzymatic Reactions by Binding Coenzymes and Basic Amino Acids*
    Pure Appl. Chem., Vol. 82, No. 4, pp. 991–999, 2010. doi:10.1351/PAC-CON-09-10-02 © 2010 IUPAC, Publication date (Web): 20 March 2010 Effect of molecular clips and tweezers on enzymatic reactions by binding coenzymes and basic amino acids* Frank-Gerrit Klärner1,‡, Thomas Schrader1, Jolanta Polkowska1, Frank Bastkowski1, Peter Talbiersky1, Mireia Campañá Kuchenbrandt1, Torsten Schaller1, Herbert de Groot2, and Michael Kirsch2 1Institute for Organic Chemistry, University of Duisburg-Essen, Universitätsstrasse 7, 45117 Essen, Germany; 2Institute for Physiological Chemistry, Universitätsklinikum Essen, Hufelandstrasse 55, 45122 Essen, Germany Abstract: The tetramethylene-bridged molecular tweezers bearing lithium methanephos - phonate or dilithium phosphate substituents in the central benzene or naphthalene spacer-unit and the dimethylene-bridged clips containing naphthalene or anthracene sidewalls substi- tuted by lithium methanephosphonate, dilithium phosphate, or sodium sulfate groups in the central benzene spacer-unit are water-soluble. The molecular clips having planar naphthalene sidewalls bind flat aromatic guest molecules preferentially, for example, the nicotinamide ring and/or the adenine-unit in the nucleotides NAD(P)+, NMN, or AMP, whereas the ben- zene-spaced molecular tweezers with their bent sidewalls form stable host–guest complexes with the aliphatic side chains of basic amino acids such as lysine and argenine. The phos- phonate-substituted tweezer and the clips having an extended central naphthalene spacer-unit or extended anthracene and benzo[k]fluoranthene sidewalls, respectively, form highly stable self-assembled dimers in aqueous solution, evidently due to non-classical hydrophobic inter- actions. The phosphate-substituted molecular clip containing naphthalene sidewalls inhibits the enzymatic, ADH-catalyzed ethanol oxidation by binding the cofactor NAD+ in a com- petitive reaction.
    [Show full text]