Theoretical investigation on regiochemically well-defined alkyl-substituted oligothiophenes

摘要

A series of alkyl-substituted bithiophenes, terthiophenes, and sexithiophenes is theoretically investigated in the framework of semi-empirical quantum chemical calculations. Full geometry optimizations are performed to obtain the torsion energies of thiophene rings around the inter- ring bonds. Comparison among several semi-empirical techniques is presented. A dramatic dependence of torsion barriers as a function of substitution position is observed. These geometrical data are used to interpret the properties of the newly synthesized polymers, based on terthiophenes substituted in the edge rings as well as in the inner ring, that are reported in the literature. The influence of inter-chain coupling and solvent effects on the thermo- and solvatochromic properties of these materials also is investigated.