1. Operative Mechanism of Hole-Assisted Negative Charge Motion in Ground States of Radical-Anion Molecular Wires
- Author
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Isaac Alcón, Jaume Veciana, Carlos Franco, Juan Casado, Marta Mas-Torrent, Vega Lloveras, Juan T. López Navarrete, Stefan T. Bromley, Concepció Rovira, Paula Mayorga Burrezo, Rubén Caballero, Fernando Langa, Ministerio de Economía y Competitividad (España), Generalitat de Catalunya, Centro de Investigación Biomédica en Red Bioingeniería, Biomateriales y Nanomedicina (España), and Universitat de Barcelona
- Subjects
Transferència de càrrega ,02 engineering and technology ,Electron ,010402 general chemistry ,Transport d'electrons ,01 natural sciences ,Biochemistry ,Catalysis ,Ion ,Molecular wire ,Electron transfer ,Colloid and Surface Chemistry ,Charge transfer ,Computational chemistry ,Length dependence ,Química quàntica ,Quantum tunnelling ,Chemistry ,Electron transport ,Cinètica química ,Charge (physics) ,General Chemistry ,021001 nanoscience & nanotechnology ,Thienylenevinylene oligomers ,0104 chemical sciences ,Espectroscòpia Raman ,Intramolecular electron-transfer ,Chemical kinetics ,Superexchange ,Chemical physics ,Conductance ,Raman spectroscopy ,0210 nano-technology ,Ground state ,Quantum chemistry - Abstract
Franco, Carlos et al., 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 Å. 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 tran-sient mobile polaronic states in the bridge that terminate by an electron-hole recombination at the other wire extreme. On the con-trary for the shorter radical-anions our results suggest that a flickering resonance mechanism which is intermediate between hop-ping 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 infor-mation obtained from UV-Vis and Raman spectroscopies and by quantum chemical modelling., We acknowledge the financial support from the Spanish MINECO/FEDER (grants CTQ2013-40480-R, CTQ2016- 7989-R, and CTQ2015-64618-R), Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (grant SEV2015-0496), the Generalitat de Catalunya (grants 2014SGR-17, 2014SGR-97, and XRQTC). We also acknowledge supercomputing resources provided by the Red Españ ola de Supercomputacion and the Networking Research Center of Bioengineering, Biomaterials and Nanomedicine (CIBERBBN). The work carried out at the University of Malaga was supported by MINECO/FEDER through the reference projects CTQ2012-33733 andCTQ2015-69391-P. The “Servicios Centrales de Apoyo a la Investigacioń ” of the University of Malaga are also acknowledged by generous access to its facilities. I.A. acknowledges the Spanish Ministerio de Educacion Cultura y Deporte for a FPU PhD scholarship.
- Published
- 2017