Oligo[methyl(phenyl)silane] ion-radical conformations calculated by the B3LYP method

A quantum mechanical study of ion-radical conformations in oligo[methyl(phenyl)silane] (OMPSi) was performed. The conformations of the neutral, positively, and negatively charged OMPSi were optimized by means of the Hartree-Fock (HF) and B3LYP methods. The common result of both methods is that the anion-radical conformation shows a significant stretching of the chain, whereas the cation-radical conformation is contracted. This fact is associated with changes of electron density distribution. On the other hand, the conformations of OMPSi calculated by the HF and B3LYP methods significantly differ in the spatial extent of the conformational defect associated with the presence of the introduced charge. The experimental and calculated infrared vibrational spectra of the cation-radical are discussed.