Helquats, helical extended diquats, as fast electron transfer systems

0341536 - ÚFCH JH 2011 RIV GB eng J - Journal Article
Pospíšil, Lubomír - Teplý, Filip - Gál, Miroslav - Adriaenssens, Louis - Horáček, Michal - Severa, Lukáš
Helquats, helical extended diquats, as fast electron transfer systems.
Physical Chemistry Chemical Physics. Roč. 12, č. 7 (2010), s. 1550-1556. ISSN 1463-9076. E-ISSN 1463-9084
R&D Projects: GA ČR GA203/09/0705; GA ČR GP203/09/P502; GA MŠMT ME09114; GA MŠMT OC 140
Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506
Keywords : reversible redox systems * self-exchange kinetics * methyl viologen
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 3.454, year: 2010

Helicene-viologen structural hybrids, like [5]helquat, 6,7,10,11-tetrahydrodipyrido[2,1-a:1',2'-k][2,9]phenanthrolinediium, and its four methylated derivatives, are characterized by electrochemical admittance and EPR spectroscopy. All compounds are reversibly reduced in two one-electron steps. Formal redox potentials correlate with the calculated LUMO energies. The electron transfer is coupled with a weak adsorption of the reactants. The analysis of the frequency dependence of the electrode admittance is used for the separation of Faradaic and double layer contributions and finally to the estimation of heterogeneous rate constants. Heterogeneous rate constants determined this way are in the range 0.1 to 3 cm s(-1). In all cases the second electron transfer is faster than the first redox step by a factor of three. The Frumkin correction for the acceleration by the double layer potential further amplifies this difference.
Permanent Link: http://hdl.handle.net/11104/0184483