Chromium complexes intersystem crossing

In summary, spectroscopic studies show that at low temperatures higher excited states of chromium(III) complexes undergo rapid internal conversion to the metastable T2g or 2Eg levels. Intersystem crossing from the 4T2g to the aEg level occurs with near unit efficiency in many chromium(III) complexes. Phosphorescence competes, usually unfavorably, with radiationless decay from the 2Eg state. Studies of the excited states of Mo(III), (4d)3, based on absorption spectra of its complexes in solution, have recently been reported.134-137... 

Thus the activation volume AV for the rate constant kp of an individual ES reaction pathway can be evaluated if the pressure dependencies of the photoreaction quantum yield, of intersystem crossing and of the ES lifetime can be separately determined. However, such parameterization becomes considerably more complex if several different excited states are involved or if a fraction of the photosubstitution products are formed from states that are not vibrationally relaxed with respect to the medium. Currently, parameterization of pressure effects on photosubstitutions has been attempted for a limited number of metal complexes. These include certain rhodium(III) and chromium(III) amine complexes and some Group VI metal carbonyls, which will be summarized here. 

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