Semi-Empirical (PM3) Study of Conformational Analysis and Electronic Properties of Functionalized Oligohexylthiophenes

Abstract

A semi empirical analysis of a series of 3-hexylthiophenes [3-XHT, where X = Br, NH₂, SH, CN, COOH, CONC(CH₃)₂ and N(CH₃)₂] having functional group attached to the hexyl substituent up to four monomeric units with head-tail-headtail regioselectivity was carried out. The energy band gap obtained at PM3 level and the results showed that oligomers with 3-(N,N-dimethyl)aminohexylthiophene (3DAHT) present lowest energy band gap although larger that than 3-aminothiophene (3HT). 3DAHT and 3-aminothiophene (3AHT) both with electron donating substituents respond differently when the polymer was torsioned. The electronic donating ability of NH₂ through the hexyl carbon-carbon bonds was drastically reduced whereas that of N(CH₃)₂ was enhanced. The energy band gap changed with the functional group attached to hexyl substituents with some effects on the molecular properties related to electronic conductivity.