scholarly journals Poly-p-hydroquinone Ethers: Isoenergetic Molecular Wires with Length-Invariant Oxidation Potentials and Cation Radical Excitation Energies

2017 ◽  
Vol 139 (12) ◽  
pp. 4334-4337 ◽  
Author(s):  
Maxim V. Ivanov ◽  
Vincent J. Chebny ◽  
Marat R. Talipov ◽  
Rajendra Rathore
Keyword(s):  
Cation Radical ◽  
Molecular Wires ◽  
Excitation Energies ◽  
Oxidation Potentials ◽  
Radical Excitation

scholarly journals Beyond the Woodward-Hoffman Rules: What Controls Reactivity in Eliminative Aromatic Ring-Forming Reactions?

2018 ◽  
Vol 71 (4) ◽  
pp. 249 ◽  
Author(s):  
A. D. Dinga Wonanke ◽  
Deborah L. Crittenden
Keyword(s):  
Molecular Wires ◽  
Chemical Diversity ◽  
Semiconducting Polymers ◽  
Cyclization Reactions ◽  
Rate Determining Step ◽  
Oxidation Potentials ◽  
Optimal Balance ◽  
Ring Oxidation ◽  
Dehydrogenation Reactions ◽  
Key Aspects

The Mallory (photocyclization) and Scholl (thermal cyclohydrogenation) reactions are widely used in the synthesis of extended conjugated π systems of high scientific interest and technological importance, including molecular wires, semiconducting polymers, and nanographenes. While simple electrocyclization reactions obey the Woodward-Hoffman rules, no such simple, general, and powerful model is available for eliminative cyclization reactions due to their increased mechanistic complexity. In this work, detailed mechanistic investigations of prototypical reactions reveal that there is no single rate-determining step for thermal oxidative dehydrogenation reactions, but they are very sensitive to the presence and distribution of heteroatoms around the photocyclizing ring system. Key aspects of reactivity are correlated to the constituent ring oxidation potentials. For photocyclization reactions, planarization occurs readily and/or spontaneously following photo-excitation, and is promoted by heteroatoms within 5-membered ring adjacent to the photocyclizing site. Oxidative photocyclization requires intersystem crossing to proceed to products, while reactants configured to undergo purely eliminative photocyclization could proceed to products entirely in the excited state. Overall, oxidative photocyclization seems to strike the optimal balance between synthetic convenience (ease of preparation of reactants, mild conditions, tolerant to chemical diversity in reactants) and favourable kinetic and thermodynamic properties.

Oxidation Potentials Correlate with Conductivities of Aromatic Molecular Wires

2007 ◽  
Vol 129 (41) ◽  
pp. 12376-12377 ◽  
Author(s):  
Jordan R. Quinn ◽  
Frank W. Foss ◽  
Latha Venkataraman ◽  
Ronald Breslow
Keyword(s):  
Molecular Wires ◽  
Oxidation Potentials

scholarly journals Trifluoromethyl-substituted tetrathiafulvalenes

2015 ◽  
Vol 11 ◽  
pp. 647-658 ◽  
Author(s):  
Olivier Jeannin ◽  
Frédéric Barrière ◽  
Marc Fourmigué
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Cation Radical ◽  
Radical Cations ◽  
Oxidation Potential ◽  
Low Energy ◽  
Charge Transfer Complexes ◽  
Mesomeric Effect ◽  
Oxidation Potentials ◽  
Homo Lumo

A series of tetrathiafulvalenes functionalized with one or two trifluoromethyl electron-withdrawing groups (EWG) is obtained by phosphite coupling involving CF3-substituted 1,3-dithiole-2-one derivatives. The relative effects of the EWG such as CF3, CO2Me and CN on the TTF core were investigated from a combination of structural, electrochemical, spectrochemical and theoretical investigations. Electrochemical data confirm the good correlations between the first oxidation potential of the TTF derivatives and the σmeta Hammet parameter, thus in the order CO2Me < CF3 < CN, indicating that, in any case, the mesomeric effect of the substituents is limited. Besides, crystal structure determinations show that the deformation of the unsymmetrically substituted dithiole rings, when bearing one, or two different EWG, and attributed to the mesomeric effect of ester or nitrile groups, is not notably modified or counter-balanced by the introduction of a neighboring trifluoromethyl group. DFT calculations confirm these observations and also show that the low energy HOMO–LUMO absorption band found in nitrile or ester-substituted TTFs is not found in TTF-CF3, where, as in TTF itself, the low energy absorption band is essentially attributable to a HOMO→LUMO + 1 transition. Despite relatively high oxidation potentials, these donor molecules with CF3 EWG can be involved in charge transfer complexes or cation radical salts, as reported here for the CF3-subsituted EDT-TTF donor molecule. A neutral charge transfer complex with TCNQ, (EDT-TTF-CF3)2(TCNQ) was isolated and characterized through alternated stacks of EDT-TTF-CF3 dimers and TCNQ in the solid state. A radical cation salt of EDT-TTF-CF3 is also obtained upon electrocrystallisation in the presence of the FeCl4 − anion. In this salt, formulated as (EDT-TTF-CF3)(FeCl4), the (EDT-TTF-CF3)+• radical cations are associated two-by-two into centrosymmetric dyads with a strong pairing of the radical species in a singlet state.

Energy Levels and Electromagnetic Transition of 90-94mo Nuclei Using Ibm-1

2020 ◽  
pp. 149-152
Keyword(s):  
Experimental Data ◽  
Transition Probability ◽  
Energy Levels ◽  
Dynamical Symmetry ◽  
Interacting Boson Model ◽  
Excitation Energies ◽  
Electromagnetic Transition ◽  
Boson Model ◽  
Energy States ◽  
Good Agreement

The energy states for the J , b , ɤ bands and electromagnetic transitions B (E2) values for even – even molybdenum 90 – 94 Mo nuclei are calculated in the present work of "the interacting boson model (IBM-1)" . The parameters of the equation of IBM-1 Hamiltonian are determined which yield the best excellent suit the experimental energy states . The positive parity of energy states are obtained by using IBS1. for program for even 90 – 94 Mo isotopes with bosons number 5 , 4 and 5 respectively. The" reduced transition probability B(E2)" of these neuclei are calculated and compared with the experimental data . The ratio of the excitation energies of the 41+ to 21+ states ( R4/2) are also calculated . The calculated and experimental (R4/2) values showed that the 90 – 94 Mo nuclei have the vibrational dynamical symmetry U(5). Good agreement was found from comparison between the calculated energy states and electric quadruple probabilities B(E2) transition of the 90–94Mo isotopes with the experimental data .

Endgroup and Sidechain Functionalization of Surface-Initiated ROMP Thin Films: Progress Towards ROMP-Based Molecular Wires

2018 ◽  
Author(s):  
Nicholas Marshall
Keyword(s):  
Thin Films ◽  
Contact Angle ◽  
Cyclic Voltammetry ◽  
Polymer Films ◽  
Conjugated Polymer ◽  
Ring Opening ◽  
Molecular Wires ◽  
Metathesis Polymerization ◽  
Cross Metathesis ◽  
Active Ester

A set of experiments in surface-initiated ring-opening metathesis polymerization, including end-functionalization of growing brushes and contact angle/cyclic voltammetry measurements. We report preparation and CV of two different conjugated polymer films, and several endgroup and sidechain functionalization experiments using cross-metathesis and active ester substitution.<br>

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