Symmetry vs. fluxionality, a radical anion with borderline properties

Mazur, Stephen; Streekumar, C.; Schroeder, Albert H.

doi:10.1021/ja00437a056

Cited by 30 publications

(17 citation statements)

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“…Mazur and co-workers in their studies of dicarbonyl radical anions 65,66. Kubiak and Ito have further applied IR to inorganic mixed-valence complexes in the form of IR spectroelectrochemistry 67,68.…”

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confidence: 99%

Electron Localization of Anions Probed by Nitrile Vibrations

et al. 2015

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Localization and delocalization of electrons is a key concept in chemistry, and is one of the important factors determining the efficiency of electron transport through organic conjugated molecules, which have potential to act as "molecular wires". This, in turn, substantially influences the efficiencies of organic solar cells and other molecular electronic devices. It is also necessary to understand the electronic energy landscape and the dynamics that govern electron transport capabilities in one-dimensional conjugated chains so that we can better define the design principles for conjugated molecules for their applications. We show that nitrile ν(C≡N) vibrations respond to the degree of electron localization in nitrile-substituted organic anions by utilizing time-resolved infrared detection combined with pulse radiolysis. Measurements of a series of aryl nitrile anions allow us to construct a semiempirical calibration curve between the changes in the ν(C≡N) infrared (IR) shifts and the changes in the electronic charges from the neutral to the anion states in the nitriles; more electron localization in the nitrile anion results in larger IR shifts. Furthermore, the IR line width in anions can report a structural change accompanying changes in the electronic density distribution. Probing the shift of the nitrile ν(C≡N) IR vibrational bands enables us to determine how the electron is localized in anions of nitrile-functionalized oligofluorenes, considered as organic mixed-valence compounds. We estimate the diabatic electron transfer distance, electronic coupling strengths, and energy barriers in these mixed-valence compounds. The analysis reveals a dynamic picture, showing that the electron is moving back and forth within the oligomers with a small activation energy of ≤kBT, likely controlled by the movement of dihedral angles between monomer units. Implications for the electron transport capability in molecular wires are discussed.

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confidence: 99%

Electron Localization of Anions Probed by Nitrile Vibrations

et al. 2015

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“…Dichinon [49,252,253] und Hosoi et al [254] untersucht in Dimethylsulfoxid und Acetonitril ergaben. [252,253] Darüber hinaus konnte gezeigt werden, dass die vibronische Kopplung für das unerwartete Spektrum verantwortlich ist.…”

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“…[252,253] Darüber hinaus konnte gezeigt werden, dass die vibronische Kopplung für das unerwartete Spektrum verantwortlich ist. Temperaturabhängige ESR-Messungen belegen ganz klar einen Klasse-II-Charakter, wobei die ET-Geschwindigkeit stark von Gegenion und Lçsungsmittel beeinflusst wird.…”

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Organische gemischtvalente Verbindungen: ein Spielplatz für Elektronen und Löcher

2011

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Gemischtvalente (MV) Verbindungen sind ausgezeichnete Modellsysteme, um grundlegende Elektronentransport(ET)‐ und Ladungstransfer(CT)‐Phänomene zu untersuchen. Diese sind in komplexen biophysikalischen Prozessen wie der Photosynthese, aber auch in artifiziellen elektronischen Bauteilen von großer Bedeutung. So sind organische MV‐Verbindungen effiziente Lochtransportmaterialien in organischen lichtemittierenden Dioden (OLEDs), Solarzellen und photochromen Fenstern. Die Bedeutung der organischen gemischtvalenten Chemie sollte jedoch weniger in ihrer direkten Anwendbarkeit gesehen werden, als vielmehr in dem riesigen Kenntnisschatz über Elektronentransferphänomene, der durch ihr Studium gewonnen wurde. Die große Vielfalt an organischen Redoxzentren und Brückeneinheiten, die zu MV‐Verbindungen kombiniert werden können, sowie die stete Weiterentwicklung von ET‐Theorien und ET‐Untersuchungsmethoden förderten das enorme Interesse an organischen MV‐Verbindungen in den letzten Jahrzehnten und zeigen das große Potential dieser Verbindungsklasse auf. Das Ziel dieses Aufsatzes ist es, das letzte Jahrzehnt der organischen gemischtvalenten Chemie zusammenzufassen und ihren Einfluss auf moderne funktionelle Materialien hervorzuheben.

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“…[37] For the 1,2,4-substituted isomer 6 3 , the theoretical analysis is analogous. Therefore, only the relevant five diabatic states at energy 0 and H À R DG 0 are given in Scheme 4 as well as the reduced determinant Equation (6) in which the same simplification has been made as in the case of imately at the energy H À R DG 0 . Again, for determining V from the IV-CT band by using Equation (1), we have to divide this equation by a symmetry factor of p 4 which is derived from the four (nearly) degenerate excited states.…”

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confidence: 99%

Optically and Thermally Induced Electron Transfer Pathways in Hexakis[4-(N,N-diarylamino)phenyl]benzene Derivatives

Lambert¹,

Nöll²

2002

Chem. Eur. J.

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The optically and thermally induced electron transfer pathways of highly symmetrical (D3) hexaarylbenzene systems with six triarylamine redox sites have been investigated. Owing to slightly different local redox potentials, the radical trication could be selectively generated by electrochemical methods. This trication shows a strong intervalence charge‐transfer band in the near infrared (NIR) that was measured by spectroelectrochemistry and analysed using multi‐dimensional Mulliken–Hush theory. Quantum chemical AM1 CI calculations indicate that there is no optically induced concerted three‐electron transfer that transforms the ground state into a state in which all three positively charged triarylamine moieties change place with their neutral neighbours. The potential energy surface of the ground state was constructed by using quadratic potentials. From this potential surface it is apparent that there is also no thermally allowed concerted three‐electron transfer pathway. Instead, three consecutive one‐electron transfer steps are necessary for this process.

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Symmetry vs. fluxionality, a radical anion with borderline properties

Cited by 30 publications

References 1 publication

Electron Localization of Anions Probed by Nitrile Vibrations

Electron Localization of Anions Probed by Nitrile Vibrations

Organische gemischtvalente Verbindungen: ein Spielplatz für Elektronen und Löcher

Optically and Thermally Induced Electron Transfer Pathways in Hexakis[4-(N,N-diarylamino)phenyl]benzene Derivatives

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