Excited-State Behavior of Phenylethynyldisilanes: An Intramolecular Charge-Transfer Emission

Article abstract of DOI:10.1021/j100292a015

Photochemical and photophysical properties of phenylethynyldisilanes in MP (methylcyclohexane/isopentane, 3:1 v/v) have been studied by means of picosecond and the nanosecond spectroscopy along with steady-state experiments.Intramolecular charge transfer in the excited singlet state of phenylethynyldisilanes occurs very rapidly (<10ps) at both 77 and 294 K.His finding shows that internal rotation (or twisting) or solvatation is not necessary for the intramolecular CT formation of phenylethynyldisilanes.The mechanism on the intramolecular CT from the ¹(?,?*) state to the ¹(2p?,3d?) CT state of the compounds is quite different from that of the usual TICT (twisted intramolecular charge transfer).Two decay components (fast and slaw) of the ¹CT state are observed, which are ascribed to the intersystem crossing rates from ¹CT to ³(?,?*), depending upon the molecular conformations of the ¹CT state of phenylethynyldisilanes.The photochemical reaction to produce silacyclopropenes takes place efficiently via the ¹CT state at room temperature, but not in MP glass at 77 K.