We performed a theoretical investigation
on a series of π-conjugated
organic molecules containing naphtho[2,3-b]thiophene
and their derivatives using density functional theory calculations.
All molecules considered exhibit planar structures and aromaticity.
Energy levels of frontier orbitals and reduction and oxidation potentials
of these compounds predicted by our solvation model reveal good agreement
with available experimental values. The UV absorption spectra point
out a clear trend that maximum peaks corresponding HOMO–LUMO
transitions are red-shifted: (i) from compounds containing O to those
containing Se, (ii) from dimers 1a–3a and 1b–3b to trimers 4a–6a and 4b–6b, and (iii) from parent compounds 1a–6a to perfluorinated derivatives 1b–6b. Parent compounds 1a–6a can be
considered as p-type semiconducting materials with low reorganization
energies, high transfer integrals, and hole mobility. Perfluorinated
compounds 1b–6b are suggested to
be very good candidates for ambipolar semiconducting materials. Introduction
of fused-ring core molecules considerably improves the charge transport
characteristics of the co-oligomers 4a–6a and 4b–6b as compared to those
of corresponding molecules 1a–3a and 1b–3b. Accordingly, the former have lower
reorganization energies, higher electron transfer integrals, and higher
rates of charge hopping.