Le. Bolivarmarinez et al., ELECTRONIC-STRUCTURE OF PUSH-PULL MOLECULES BASED ON THIOPHENE OLIGOMERS, Journal of physical chemistry, 100(26), 1996, pp. 11029-11032
Thiophene oligomers (alpha-alpha' linkages) have been intensively stud
ied in the past few years. In particular, sexithiophenes have been syn
thesized with a high degree of purity and good crystallinity, allowing
the fabrication of reliable field effect transistors. When donor-acce
ptor terminal groups are attached to thiophene oligomers, ail anomalou
s behavior of the fluorescence as a function of the number of rings is
reported. There are experimental evidences of charge transfer suppres
sion for oligomers containing more than four rings. In this work, we h
ave investigated the electronic structure of these systems. Geometrica
l optimizations and spectroscopic features of both ground and excited
states were obtained through the use of sophisticated semiempirical me
thods. Our results have shown that charge transfer suppression can be
explained in terms of the evolution of the electronic spectrum.