The Si–B chromophore: A joint experimental and theoretical investigation

Silylboranes with aromatic substituents linked to boron and silicon exhibit an unexpected absorption band in the UV–Vis spectral region. When polar groups were introduced, a marked solvatochromic effect was observed in their fluorescence emission spectra, revealing a strong excited state dipole moment. Semi-empirical MNDO/d and AM1 calculations showed that, upon UV excitation, the polarity of the Si–B bond increased and the aromatic π-electrons migrated toward the Si–B bond, consistent with experimental observations.

Organosilylboranes with mesityl groups on boron exhibit an unexpected fluorescence emission band, along with a charge transfer from the silicon atom and the mesityl groups toward the boron atom. MNDO/d calculations showed that these phenomena can be ascribed to a large extent to an Si–B HOMO–LUMO transition.Figure optionsDownload as PowerPoint slide