Excitations in oligosilanes with photochromic side groups

A quantum mechanical study of conformations, electronic densities, and absorption spectra of neutral and cation-radical hepta[methyl(phenyl)silanes] (7MPSi) substituted with a photochromic spiropyran derivative (SP/MR) was performed. 7MPSi-SP exhibit similar differences between the neutral and cation-radical conformation as unsubstituted 7MPSi, while 7MPSi-MR do not show any significant main chain conformation differences between the neutral and positively charged macromolecule. Population analysis shows that the positive charge in the cation-radical of 7MPSi-SP is located on the main chain, while in the cation-radical of 7MPSi-MR it is located on the photochromic unit.