Manifestations of conformational defects in electronic spectra of polysilanes - A theoretical study

Abstract

In this paper, density functional theory (DFT) and time dependent DFT (TDDFT) are applied on the calculation of electronic properties of alkyl- and aryl-substituted oligosilanes with conformational defect introduced into their silicon chain. Oligo[methyl(phenyl)silane]s and oligo(dimethylsilane)s up to 10 or 13 mer units, respectively, are treated as model structures by DFT and TDDFT with B3LYP/6-31 G* base. Frontier molecular orbital (FMO) energies evince the dependence on the presence as well as on the position of the defect in oligomer backbones. Delocalization of FMO is strongly influenced by position of the defect which in some cases divides the molecule to the FMO-rich part and the part almost without FMO delocalization and therefore affects location of electrons. Behaviour of longer chains in analogous polysilanes is deduced from linear regression of plots of FMO energy over the inverse of the polymerization degree. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.