Recent Progress in Quinoidal Singlet Biradical Molecules
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Review Sheet on Determining Term Symbols
Review Sheet on Determining Term Symbols Term symbols for electronic configurations are useful not only to the spectroscopist but also to the inorganic chemist interested in understanding electronic and magnetic properties of molecules. We will concentrate on the method of Douglas and McDaniel (p. 26ff); however, you may find other treatments equal or superior to the D & M method. Term symbols are a shorthand method used to describe the energy, angular momentum, and spin multiplicity of an atom in any particular state. The general form is a given as Tj where T is a capital letter corresponding to the value of L (the angular momentum quantum number) and may be assigned as S, P, D, F, G, … for |L| = 0, 1, 2, 3, 4, … respectively. The superscript “a” is called the spin multiplicity and can be evaluated as a = 2S +1 where S is the spin quantum number. The subscript “j” is the numerical value of J, a new quantum number defined as: J = l +S, which corresponds to the total orbital and spin angular momentum of the system. The term symbol 3P is read as triplet – Pee state and indicates that there are two unpaired electrons in a state with maximum orbital angular momentum, L=1. The number of microstates (N) of a system corresponds to the total number of distinct arrangements for “e” number of electrons to be placed in “n” number of possible orbital positions. N = # of microstates = n!/(e!(n-e)!) For a set of p orbitals n = 6 since there are 2 positions in each orbital. -
States of Oxygen Liquid and Singlet Oxygen Photodynamic Therapy
Oxygen States of Oxygen As far as allotropes go, oxygen as an element is fairly uninteresting, with ozone (O3, closed-shell and C2v symmetric like SO2) and O2 being the stable molecular forms. Most of our attention today will be devoted to the O2 molecule that is so critically connected with life on Earth. 2 2 2 4 2 O2 has the following valence electron configuration: (1σg) (1σu) (2σg) (1πu) (1πg) . It is be- cause of the presence of only two electrons in the two π* orbitals labelled 1πg that oxygen is paramagnetic with a triplet (the spin multiplicity \triplet" is given by 2S+1; here S, the total spin quantum number, is 0.5 + 0.5 = 1). There are six possible ways to arrange the two electrons in the two degenerate π* orbitals. These different ways of arranging the electrons in the open shell are called \microstates". Further, because there are six microstates, we can say that the total degeneracy of the electronic states 2 3 − arising from (1πg) configuration must be equal to six. The ground state of O2 is labeled Σg , the left superscript 3 indicating that this is a triplet state. It is singly degenerate orbitally and triply degenerate in terms of spin multiplicity; the total degeneracy (three for the ground state) is given by the spin times the orbital degeneracy. 1 The first excited state of O2 is labeled ∆g, and this has a spin degeneracy of one and an orbital degeneracy of two for a total degeneracy of two. This state corresponds to spin pairing of the electrons in the same π* orbital. -
Photochemical and Magnetic Properties of Complex and Nuclear Chemistry
• Programme: MSc in Chemistry • Course Code: MSCHE2001C04 • Course Title: Photochemical and magnetic properties of complex and nuclear chemistry • Unit: Electronic spectra of coordination compounds • Course Coordinator: Dr. Jagannath Roy, Associate Professor, Department of Chemistry, Central University of South Bihar Note: These materials are only for classroom teaching purpose at Central University of South Bihar. All the data/figures/materials are taken from text books, e-books, research articles, wikipedia and other online resources. 1 Course Objectives: 1. To make students understand structure and propeties of inorganic compounds 2. To accuaint the students with the electronic spectroscopy of coordination compounds 3. To introduce the concepts of magnetochemistry among the students for analysing the properties of complexes. 4. To equip the students with necessary skills in photochemical reaction transition metal complexes 5. To develop knowledge among the students on nuclear and radio chemistry Learning Outcomes: After completion of the course, learners will be able to: 1. Analyze the optical/electronic spectra of coordination compounds 2. Make use of the photochemical behaviour of complexes in designing solar cells and other applications. 3. Design and perform photochemical reactions of transition metal complexes 4. Analyze the magnetic properties of complexes 5. Explain the various phenomena taking place in the nucleus 6. Understand the working of nuclear reactors 2 Lecture-1 Lecture Topic- Introduction to the Electronic Spectra of Transition Metal complexes 3 Crystal field theory (CFT) is ideal for d1 (d9) systems but tends to fail for the more common multi- electron systems. This is because of electron-electron repulsions in addition to the crystal field effects on the repulsion of the metal electrons by the ligand electrons. -
The Chemistry of Carbene-Stabilized
THE CHEMISTRY OF CARBENE-STABILIZED MAIN GROUP DIATOMIC ALLOTROPES by MARIHAM ABRAHAM (Under the Direction of Gregory H. Robinson) ABSTRACT The syntheses and molecular structures of carbene-stabilized arsenic derivatives of 1 1 i 1 1 AsCl3 (L :AsCl3 (1); L : = :C{N(2,6- Pr2C6H3)CH}2), and As2 (L :As–As:L (2)), are presented herein. The potassium graphite reduction of 1 afforded the carbene-stabilized diarsenic complex, 2. Notably, compound 2 is the first Lewis base stabilized diatomic molecule of the Group 13–15 elements, in the formal oxidation state of zero, in the fourth period or lower of the Periodic Table. Compound 2 contains one As–As σ-bond and two lone pairs of electrons on each arsenic atom. In an effort to study the chemistry of the electron-rich compound 2, it was combined with an electron-deficient Lewis acid, GaCl3. The addition of two equivalents of GaCl3 to 2 resulted in one-electron oxidation of 2 to 1 1 •+ – •+ – give [L :As As:L ] [GaCl4] (6 [GaCl4] ). Conversely, the addition of four equivalents of GaCl3 to 2 resulted in two- electron oxidation of 2 to give 1 1 2+ – 2+ – •+ [L :As=As:L ] [GaCl4 ]2 (6 [GaCl4 ]2). Strikingly, 6 represents the first arsenic radical to be structurally characterized in the solid state. The research project also explored the reactivity of carbene-stabilized disilicon, (L1:Si=Si:L1 (7)), with borane. The reaction of 7 with BH3·THF afforded two unique compounds: one containing a parent silylene (:SiH2) unit (8), and another containing a three-membered silylene ring (9). -
New Electron-Deficient Polycyclic Aromatic Dicarboximides by Palladium-Catalyzed C–C Coupling and Core Halogenation–Cyanation
New Electron-Deficient Polycyclic Aromatic Dicarboximides by Palladium-Catalyzed C–C Coupling and Core Halogenation–Cyanation Dissertation zur Erlangung des naturwissenschaftlichen Doktorgrades der Julius-Maximilians-Universität Würzburg vorgelegt von Sabine Seifert aus Marktredwitz Würzburg 2017 ii Eingereicht bei der Fakultät für Chemie und Pharmazie am: 18.10.2017 Gutachter der schriftlichen Arbeit: 1. Gutachter: Prof. Dr. Frank Würthner 2. Gutachter: Prof. Dr. Anke Krüger Prüfer des öffentlichen Promotionskolloquiums: 1. Prüfer: Prof. Dr. Frank Würthner 2. Prüfer: Prof. Dr. Anke Krüger 3. Prüfer: Prof. Dr. Ingo Fischer Datum des öffentlichen Promotionskolloquiums: 15.12.2017 Doktorurkunde ausgehändigt am: _________________________ iii iv Abbreviations abs absorbance/absorption Ac acetyl Ar aryl ap applied a.u. arbitrary unit (I)CT (intramolecular) charge transfer CV cyclic voltammetry dba dibenzylideneacetone DBN 1,5-diazabicyclo[4.3.0]non-5-ene DBU 1,8-diazabicyclo[5.4.0]undec-7-ene DCM dichloromethane DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (TD-)DFT (time-dependent) density functional theory DIPEA diisopropylethylamine DMAP 4-dimethylaminopyridine DMF dimethylformamide DMSO dimethyl sulfoxide dppf 1,1'-bis(diphenylphosphino)ferrocene em emission ESI electrospray ionization ex excitation Fc+/Fc ferrocenium/ferrocene redox couple fl fluorescence iPr iso-propyl HOMO highest occupied molecular orbital HPLC high performance liquid chromatography HR high-resolution I intensity L ligand LUMO lowest unoccupied molecular orbital PADI -
Photochemical Generation of Carbenes and Ketenes from Phenanthrene-Based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene
Colby College Digital Commons @ Colby Honors Theses Student Research 2017 Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene Tarini S. Hardikar Student Tarini Hardikar Colby College Follow this and additional works at: https://digitalcommons.colby.edu/honorstheses Part of the Organic Chemistry Commons Colby College theses are protected by copyright. They may be viewed or downloaded from this site for the purposes of research and scholarship. Reproduction or distribution for commercial purposes is prohibited without written permission of the author. Recommended Citation Hardikar, Tarini S. and Hardikar, Tarini, "Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene" (2017). Honors Theses. Paper 948. https://digitalcommons.colby.edu/honorstheses/948 This Honors Thesis (Open Access) is brought to you for free and open access by the Student Research at Digital Commons @ Colby. It has been accepted for inclusion in Honors Theses by an authorized administrator of Digital Commons @ Colby. Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene TARINI HARDIKAR A Thesis Presented to the Department of Chemistry, Colby College, Waterville, ME In Partial Fulfillment of the Requirements for Graduation With Honors in Chemistry SUBMITTED MAY 2017 Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene TARINI HARDIKAR Approved: (Mentor: Dasan M. Thamattoor, Professor of Chemistry) (Reader: Rebecca R. Conry, Associate Professor of Chemistry) “NOW WE KNOW” - Dasan M. Thamattoor Vitae Tarini Shekhar Hardikar was born in Vadodara, Gujarat, India in 1996. She graduated from the S.N. -
Chemical Shift (Δ)
Chapter 9 ● Nuclear Magnetic Resonance Ch. 9 - 1 1. Introduction Classic methods for organic structure determination ● Boiling point ● Refractive index ● Solubility tests ● Functional group tests ● Derivative preparation ● Sodium fusion (to identify N, Cl, Br, I & S) ● Mixture melting point ● Combustion analysis ● Degradation Ch. 9 - 2 Classic methods for organic structure determination ● Require large quantities of sample and are time consuming Ch. 9 - 3 Spectroscopic methods for organic structure determination a) Mass Spectroscopy (MS) ● Molecular Mass & characteristic fragmentation pattern b) Infrared Spectroscopy (IR) ● Characteristic functional groups c) Ultraviolet Spectroscopy (UV) ● Characteristic chromophore d) Nuclear Magnetic Resonance (NMR) Ch. 9 - 4 Spectroscopic methods for organic structure determination ● Combination of these spectroscopic techniques provides a rapid, accurate and powerful tool for Identification and Structure Elucidation of organic compounds ● Rapid ● Effective in mg and microgram quantities Ch. 9 - 5 General steps for structure elucidation 1. Elemental analysis ● Empirical formula ● e.g. C2H4O 2. Mass spectroscopy ● Molecular weight ● Molecular formula ● e.g. C4H8O2, C6H12O3 … etc. ● Characteristic fragmentation pattern for certain functional groups Ch. 9 - 6 General steps for structure elucidation 3. From molecular formula ● Double bond equivalent (DBE) 4. Infrared spectroscopy (IR) ● Identify some specific functional groups ● e.g. C=O, C–O, O–H, COOH, NH2 … etc. Ch. 9 - 7 General steps for structure elucidation 5. UV ● Sometimes useful especially for conjugated systems ● e.g. dienes, aromatics, enones 6. 1H, 13C NMR and other advanced NMR techniques ● Full structure determination Ch. 9 - 8 Electromagnetic spectrum cosmic X-rays ultraviolet visible infrared micro- radio- & γ-rays wave wave λ: 0.1nm 200nm 400nm 800nm 50µm IR X-Ray UV NMR Crystallography 1Å = 10-10m 1nm = 10-9m 1µm = 10-6m Ch. -
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. -
Arxiv:1906.08544V1 [Cond-Mat.Mes-Hall]
Exchange rules for diradical π-conjugated hydrocarbons R. Ortiz1,2,4, R. A. Boto3, N. Garc´ıa-Mart´ınez1,2, J. C. Sancho-Garc´ıa4, M. Melle-Franco3, J. Fern´andez-Rossier1∗ (1) QuantaLab, International Iberian Nanotechnology Laboratory (INL), Av. Mestre Jos´eVeiga, 4715-330 Braga, Portugal (2)Departamento de F´ısica Aplicada, Universidad de Alicante, 03690, Sant Vicent del Raspeig, Spain (3) CICECO, Departamento de Qu´ımica, Universidade de Aveiro, 3810-193 Aveiro, Portugal and (4)Departamento de Qu´ımica F´ısica, Universidad de Alicante, 03690, Sant Vicent del Raspeig, Spain (Dated: June 21, 2019) A variety of planar π-conjugated hydrocarbons such as heptauthrene, Clar’s goblet and, recently synthesized, triangulene have two electrons occupying two degenerate molecular orbitals. The re- sulting spin of the interacting ground state is often correctly anticipated as S = 1, extending the application of Hund’s rules to these systems, but this is not correct in some instances. Here we provide a set of rules to correctly predict the existence of zero mode states, as well as the spin multiplicity of both the ground state and the low-lying excited states, together with their open- or closed-shell nature. This is accomplished using a combination of analytical arguments and configu- ration interaction calculations with a Hubbard model, both backed by quantum chemistry methods with a larger Gaussian basis set. Our results go beyond the well established Lieb’s theorem and Ovchinnikov’s rule, as we address the multiplicity and the open-/closed-shell nature of both ground and excited states. PACS numbers: I. -
Nitrogen Versus Phosphorus
The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Electronegativity for carbon: 2.5 Electronegativity for hydrogen: 2.2 Inorganic Chemistry 5.03 The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Electronegativity for carbon: 2.5 Electronegativity for hydrogen: 2.2 Inorganic Chemistry 5.03 The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Electronegativity for carbon: 2.5 Electronegativity for hydrogen: 2.2 Inorganic Chemistry 5.03 The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Quartet ground state, spin multiplicity given by 3 2S + 1 = 2( 2 ) + 1 = 4 3 1 1 3 Four possible values for the spin: + 2 , + 2 , − 2 , − 2 Inorganic Chemistry 5.03 The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Quartet ground state, spin multiplicity given by 3 2S + 1 = 2( 2 ) + 1 = 4 3 1 1 3 Four possible values for the spin: + 2 , + 2 , − 2 , − 2 Inorganic Chemistry 5.03 The Free Atom Atomic energy levels, valence orbital ionization energies (VOIE) Quartet ground state, spin multiplicity given by 3 2S + 1 = 2( 2 ) + 1 = 4 3 1 1 3 Four possible values for the spin: + 2 , + 2 , − 2 , − 2 Inorganic Chemistry 5.03 Single versus Triple Bonds Atomic energy levels, valence orbital ionization energies (VOIE) ◦ ∆Hf for P2 is +144 kJ/mol ◦ ∆Hf for P≡N is +104 kJ/mol Inorganic Chemistry 5.03 Single versus Triple Bonds Atomic energy levels, valence orbital ionization energies (VOIE) ◦ ∆Hf for P2 is +144 kJ/mol ◦ ∆Hf for P≡N -
Appendix a Mathematical Operations
Appendix A Mathematical Operations This appendix presents a number of mathematical techniques and equations for the convenience of the reader. Although we have attempted to sum marize accurately some of the most useful relations, we make no attempt at rigor. A bibliography is included at the end of this appendix. A-1 COMPLEX NUMBERS A complex quantity may be represented as follows: u = x + iy = re+i<l> (A-I) where i 2 = -1, x, y, r, and cp are real numbers and ei<l> = cos cp + i sin cpo One refers to x and y as the real and the imaginary components, respectively of u, whereas r is the absolute magnitude of u, that is, r = lui. cp is called the phase angle. The complex conjugate of u, viz., u*, is obtained by changing the sign of i wherever it appears; that is, u* = x - iy. The relation between complex numbers and their conjugates is clarified by representing them as points in the "complex plane" (Argand diagram, see Fig. A-I). The abscissa is chosen to represent the real axis (x), and the ordinate the imaginary axis 391 392 ELECTRON SPIN RESONANCE Imaginary axis u iy ~E2---------t-- Real axis u' Fig. A-l Representation of a point u and of its complex conjugate u* in complex space (Argand diagram). (y). Note that the real component of u is equal to one-half the sum of u and u*; the product of u and its complex conjugate is the square of the absolute magnitude, that is, (A-2) A-2 OPERATOR ALGEBRA A-2a. -
Extension to Nanographenes with Zig-Zag Edges
ARTICLE DOI: 10.1038/s41467-018-07095-z OPEN Dehydrative π-extension to nanographenes with zig-zag edges Dominik Lungerich 1,2, Olena Papaianina1, Mikhail Feofanov 1, Jia Liu3, Mirunalini Devarajulu3, Sergey I. Troyanov4, Sabine Maier 3 & Konstantin Amsharov 1 Zig-zag nanographenes are promising candidates for the applications in organic electronics due to the electronic properties induced by their periphery. However, the synthetic access to 1234567890():,; these compounds remains virtually unexplored. There is a lack in efficient and mild strategies origins in the reduced stability, increased reactivity, and low solubility of these compounds. Herein we report a facile access to pristine zig-zag nanographenes, utilizing an acid-promoted intramolecular reductive cyclization of arylaldehydes, and demonstrate a three-step route to nanographenes constituted of angularly fused tetracenes or pentacenes. The mild conditions are scalable to gram quantities and give insoluble nanostructures in close to quantitative yields. The strategy allows the synthesis of elusive low bandgap nanographenes, with values as low as 1.62 eV. Compared to their linear homologues, the structures have an increased stability in the solid-state, even though computational analyses show distinct diradical character. The structures were confirmed by X–ray diffraction or scanning tunneling microscopy. 1 Department of Chemistry and Pharmacy, Organic Chemistry II, Friedrich-Alexander-University Erlangen-Nuernberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany. 2 Department of Chemistry & Molecular Technology Innovation Presidential Endowed Chair, University of Tokyo, 7-3-1 Hongo, Bunkyo- ku, Tokyo 113-0033, Japan. 3 Department of Physics, Friedrich-Alexander-University Erlangen-Nuernberg, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany. 4 Chemistry Department, Moscow State University, Leninskie Gory, Moscow, Russia 119991.