Multiple bonds between main-group elements and transition metals .158. Photochemical and photophysical properties of the epoxidation catalyst CH3ReO(O-2)(2)center dot H2O

The photolysis of CH3ReO(O-2)(2) . H2O in methylene chloride yields, like the thermolysis, molecular oxygen in the tripler spin state, The quantum yield Q(Ph) of photolysis shows a remarkable dependence on the wavelength, increasing from 0.12 at 365 nm to 1.0 at 248 nm, One single excited state is responsible for this behaviour, The wavelength-dependent quantum yield profile corresponds in a first approximation to the ratio between the LMCT-band and the total absorption spectrum, The analysis of the latter spectrum was made on a mathematical basis using symmetrical Gauss curves, This is the first time that a fluorescence and phosphorescence emission of an alkyl transition-metal complex of d(0)-configuration has been detected, thus allowing for the determination of both the S-1- and the T-1-energy levels. The quantum yield of the fluorescence (Q(F)) is below 10(-3); that of the phosphorescence is below 0.04.