Reversible dimerization of 3,3',5,5',-tetramethyl-2,2'-bithiophene cations

Cyclic voltammetric measurements at different temperatures, concentrations and scan rates give evidence for the reversible dimerization of 3,3',5,5',tetramethyl-2,2'-bithiophene radical cations. The analysis of the experimental data confirm the mechanistic concept of a RR dimerization. The rate constants and equilibrium constants were determined from working curves and digital simulations. The reaction enthalpy is -60 kJ mol(-1). The weak temperature dependence of the rate constants for the dimerization results in values of the activation enthalpy that is close to zero or even negative. (C) 1997 Elsevier Science S.A.