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2017-01-18

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Operative mechanism of hole-assisted negative charge motion in ground states of radical-anion molecular wires

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https://doi.org/10.1021/jacs.6b08649

Resum

Charge transfer/transport in molecular wires over varying distances is a subject of great interest. The feasible transport mechanisms have been generally accounted for on the basis of tunneling or superexchange charge transfer operating over small distances which progressively gives way to hopping transport over larger distances. The underlying molecular sequential steps that likely take place during hopping and the operative mechanism occurring at intermediate distances have received much less attention given the difficulty in assessing detailed molecular-level information. We describe here the operating mechanisms for unimolecular electron transfer/transport in the ground state of radical-anion mixed-valence derivatives occurring between their terminal perchlorotriphenylmethyl/ide groups through thiophene-vinylene oligomers that act as conjugated wires of increasing length up to 53 angstrom, The unique finding here is that the net transport of the electron in the larger molecular wires is initiated by an electron hole dissociation intermediated by hole delocalization (conformationally assisted and thermally dependent) forming transient mobile polaronic states in the bridge that terminate by an electron hole recombination at the other wire extreme. On the contrary, for the shorter radical-anions our results suggest that a flickering resonance mechanism which is intermediate between hopping and superexchange is the operative one. We support these mechanistic interpretations by applying the pertinent biased kinetic models of the charge/spin exchange rates determined by electron paramagnetic resonance and by molecular structural level information obtained from UV-vis and Raman spectroscopies and by quantum chemical modeling.

Matèries

Transferència de càrrega, Transport d'electrons, Cinètica química, Espectroscòpia Raman, Química quàntica

Matèries (anglès)

Charge transfer, Electron transport, Chemical kinetics, Raman spectroscopy, Quantum chemistry

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Articles publicats en revistes (Ciència dels Materials i Química Física)

Citació

FRANCO, Carlos, MAYORGA BURREZO, Paula, LLOVERAS, Vega, CABALLERO, Ruben, ALCÓN ROVIRA, Isaac, BROMLEY, Stefan thomas, MAS TORRENT, Marta, LANGA, Fernando, LÓPEZ NAVARRETE, Juan t., ROVIRA I ANGULO, Concepció, CASADO, Juan, VECIANA, Jaume. Operative mechanism of hole-assisted negative charge motion in ground states of radical-anion molecular wires. _Journal of the American Chemical Society_. 2017. Vol. 139, núm. 2, pàgs. 686-692. [consulta: 20 de gener de 2026]. ISSN: 0002-7863. [Disponible a: https://hdl.handle.net/2445/124977]

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