pi-dimer from bithiophene radical cations. Investigation of equilibrium constants as a function of substituent size and supporting electrolyte using fast conversion electrochemical cells

摘要

The procedure for the determination of second order equilibrium constants K, using spectroelectrochemistry has been re-examined. Incomplete conversion of the starting material led to non-homogeneous concentration profiles and to considerable errors in the determinations of K. Values for three dialkylthiobithiophene radical cations have been measured in which the size of the thioalkyl group and of the counter anion of the supporting electrolyte are different. Large decreases observed in both cases may suggest that the association takes the form of a sandwich of two radical cations with the counter-anion in the middle. [References: 26]