Effect of backbone conformation and its defects on electronic properties and assessment of the stabilizing role of π–π interactions in aryl substituted polysilylenes studied by DFT on deca[methyl(phenyl)silylene]s

Abstract

Background

Recent efforts in the field of mesoscale effects on the structure and properties of thin polymer films call to revival interest in conformational structure and defects of a polymer backbone which has a crucial influence on electronic properties of the material. Oligo[methyl(phenyl)silylene]s (OMPSi) as exemplary molecules were studied theoretically by DFT in the form of optimal decamers and conformationally disrupted decamers (with a kink).

Results

We proved that transoid backbone conformation is true energy minimum and that a kink in the backbone causes significant hypsochromic shift of the absorption maximum (λ_max), while backbone conformation altering from all-eclipsed to all-anti affects λ_max in the opposite way. π–π stacking was investigated qualitatively through optimal geometry of OMPSi and mutual position of their phenyls along the backbone and also quantitatively by an evaluation of molecular energies obtained from single point calculations with functionals, which treat the dispersion effect in the varying range of interaction.

Conclusions

The kink was identified as a realistic element of the conformational structure that could be able to create a bend in a real aryl substituted polysilylene chain because it is stabilized by attractive π–π interactions between phenyl side groups.