Fluorescence of Cyclotetrasilanes in Rigid Glass at 77 K, a Remarkably Large Stokes Shift.

The fluorescence of cyclotetrasilanes with an extremely large Stokes shift (up to 13700 cm–1) has been observed in rigid matrices at 77 K. The large Stokes shift is interpreted in terms of variation in potential energy for the S1 and S0 states as a function of the ring Si–Si bond distance. Fluorescence properties are dependent on the molecular structures (planar and bent forms) of the compounds; the fluorescence quantum yield, lifetime, and Stokes shift for the former are greater than those for the latter.