Photophysical Features of the M2(CO)10, M = Mn and Re, Solution Photochemistry

In the UV photolysis of M2(CO)10, M = Mn or Re, flash photochemical methods were used for the determination of the primary product, i.e., nonacarbonyl (M2(CO)9) and pentacarbonyl (M(CO)5) quantum yields. The quantum yield based action spectra are very metal dependent and indicative of different mechanisms for the Re and Mn photochemistry. In the figure, the action spectra for the Re decacarbonyl photoproducts, φP for Re(CO)5 and φN for Re2(CO)9, are superimposed with the absorption spectrum. The results in the photochemistry of Re2(CO)10 suggest that the upper electronic states, i.e., populated by irradiating below 340 nm, produce some Re(CO)5.