Kinetics of Multielectron Transfers and Redox-Induced Structural Changes in N-Aryl-Expanded Pyridiniums: Establishing Their Unusual, Versatile Electrophoric Activity

0447852 - ÚFCH JH 2016 RIV US eng J - Článek v odborném periodiku
Lachmanová, Štěpánka - Dupeyre, G. - Tarábek, Ján - Ochsenbein, P. - Perruchot, Ch. - Ciofini, I. - Hromadová, Magdaléna - Pospíšil, Lubomír - Lainé, P. P.
Kinetics of Multielectron Transfers and Redox-Induced Structural Changes in N-Aryl-Expanded Pyridiniums: Establishing Their Unusual, Versatile Electrophoric Activity.
Journal of the American Chemical Society. Roč. 137, č. 35 (2015), s. 11349-11364. ISSN 0002-7863. E-ISSN 1520-5126
Grant CEP: GA ČR GA13-19213S; GA ČR(CZ) GA14-05180S; GA MŠMT(CZ) 7AMB15FR027
Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M200401202
Program: M
Institucionální podpora: RVO:61388955 ; RVO:61388963
Klíčová slova: multielectron transfer * electrochemistry * kinetics
Kód oboru RIV: CG - Elektrochemie
Impakt faktor: 13.038, rok: 2015

A combined electrochemical and theoretical study of a series of pyridinium-based electrophores, consisting of reference N-alkyl-2,4,6-triarylpyridiniums (1-3) and N-aryl-expanded pyridiniums (EPs), i.e. N-aryl-2,4,6-triarylpyridiniums (4-10), is presented with the aim of elucidating multifaceted mechanisms underpinning the complex electrophoric activity of fluxional EP systems. Series 1-10 constitutes a library of model electrophores showing an incremental variation of their composition, charge, and steric hindrance. By kinetic mapping of the first two heterogeneous electron transfers (ETs) of 1-10 and computational mapping, at the density functional theory level, of their electronic and geometrical features in various redox states, it is established that, depending on whether EPs are made of one (4, 5) or two "head-to-tail"-connected pyridinium rings (6-10), the nature of the redox-triggered distortions (when allowed) is different, namely, N-pyramidalization due to hybridization change in the former case versus saddle-shaped distortion originating from conflicting intramolecular interactions in the latter case (8-10). When skeletal relaxations are sterically hampered, zwitterionic states and electron delocalization with quinoidal features are promoted as alternative relaxation modes. It follows that "potential compression" is changed to "potential expansion" (i.e., a further separation of redox potentials) in single-pyridinium EPs (4, 5), whereas "potential inversion" (i.e., single-step two-electron transfer; 8-10) is changed to stepwise ETs of the Weitz type for two-pyridinium EPs (6, 7). Overall, kinetic rate constants not only consistently indicate the most prominent mechanistic aspects of the reduction pathways of EPs, but they are also instrumental in establishing EPs as a unique class of electrophores.
Trvalý link: http://hdl.handle.net/11104/0249614