G. Zotti et al., THIOPHENE OLIGOMERS AS POLYTHIOPHENE MODELS .1. ANODIC COUPLING OF THIOPHENE OLIGOMERS TO DIMERS - A KINETIC INVESTIGATION, Chemistry of materials, 5(4), 1993, pp. 430-436
The kinetics of anodic coupling to dimers of thiophene oligomers (n =
3-5), methyl protected at one alpha-terminal position, has been invest
igated in 1,2-dichloroethane by cyclic voltammetry and chronoamperomet
ry. The process, second-order in oligomer concentration, is characteri
zed by relatively high activation enthalpies (25/70 kJ mol-1) and nega
tive activation entropies (-100/-4 J K-1 mol-1). Though activation fre
e energies are linearly related to the inverse of the oligomer length
n (the dimerization rate decreases as n is increased), the activation
enthalpy and entropy for the pentameric radical cation are peculiarly
high, reflecting strong electron delocalization and ring coplanarizati
on.