Photochemical and photophysical behaviour of phenylsilanes and naphthylsilanes

The photochemical and photophysical properties of phenyl- and naphthyl-silanes have been studied quantitatively. It was found that the photochemical reaction of naphthyldisilanes originates from the intramolecular charge-transfer state 1(2pπ, 3dπ) produced by 2pπ*→ 3dπ charge transfer. The rearrangement (ϕr) and decrease (ϕR) quantum yields at 254 nm and the quantum yield (ϕct) for the charge-transfer emission for disilanylnaphthalenes decreased markedly with solvent polarity because of fast intersystem crossing (through the charge-transfer state) in competition with the radiative and reaction rates. Activation parameters for the photochemical reaction have been obtained. It is demonstrated that the substitution of a disilanyl group into a phenyl or naphthyl species strongly affects not only the photochemical reaction but also the photophysical processes containing fast intersystem crossing.