Conformational disorder in polysilylenes studied theoretically on tetramers

Abstract

DFT calculations with B3LYP, M06 and ωB97X-D functionals with 6-31G∗ basis set are used for a study of non-bonding intramolecular interactions in tetra[methyl(phenyl)silylene] (MPSi4), tetra[(dimethyl)silylene], tetra(silylene) (Si4) and further in molecules of tetra[cyclohexyl(methyl)silylene] and carbon chain analogue of MPSi4. A tetramer can serve as a model for conformational defect – a kink that is worth to understand especially in case of polysilylenes. The kink disruptions are viable in poly[methyl(phenyl)silylene], poly[(dimethyl)silylene] as well as in poly[cyclohexyl(methyl)silylene] chains because the energy profiles of their oligomer analogues go through minimum in gauche conformation and moreover they are significantly stabilized by non-bonding interactions (either π-π or Van der Waals). The molecule of Si4 is more flexible and keeping of a kinked conformation is less probable due to lower energy barriers in its energy profile. The functional ωB97X-D was found to be reliable in approaching real conformer distribution. TDDFT analysis of conformation impact on frontier molecular orbital density distribution and electronic transitions was performed for MPSi4 to contribute understanding of the influence of conformational disorder on electronic properties of one of the most practically important member of polysilylene group of polymers. © 2017 Elsevier B.V.