Experimental and theoretical study of the electro-oxidation of thiophene derivatives.

A serie of thiophene derivatives having functional groups of different natu re between 2 and 2' ring positions has been synthesized. Through ab-initio calculations using HF 631G basis, the geommetry was optimized and the atomi c distribution of the electronic densities of each neutral molecules were d etermined. It was found that the electronic density depends strongly on the nature of the atoms bonded to 2 and 2' ring positions. The electrooxidatio n potential of the molecules was measured by cyclic voltammetry on platinum work electrodes. An inverse relation between the electronic density and th e potential was found. The electrochemical oxidation of these compounds was irreversible and the voltammetric profiles showed assymetric peaks, which can be explain by the simoultaneous oxidation of the heterocyclic rings and the bridging functional groups.