Photolysis of methylcobalamin. Nature of the reactive excited state

Photolysis of methylcobalamin (Co(III)corrin(CH3)L + H2O + O2 �> Co(III)(H2O)L + H2CO + OH-) shows a pronounced wave-length dependence. It is suggested that the reactive excited state is of the ligand-to-ligand charge transfer (LLCT) type and involves the promotion of an electron from the Co-C sigma-bond to a pi*(corrin) orbital. This LLCT transition mixes with the pipi*(corrin) transitions. Owing to this LLCT contribution, the pipi*-absorption bands are also photoactive but with reduced efficiency

Photoluminescence of Tetranuclear Mercury(II) Complexes

The complexes [Hg4(SPh)6(PPh3)4]2+ and [Hg(2-pyridylphenyl)Cl]4 show an intense low-temperature (77 K) phosphorescence at λmax=690 and 500 nm. This emission is assumed to originate from a metal-centered ds excited state which contains considerable ligand-to-metal charge transfer character

Photochemistry and Photophysics of Coordination Compounds of the Main Group Metals

The photoproperties of main group metal complexes with the electron configurations s2 (e.g. T l + , Sb3 + , Te4 + ) and s° (e.g. T l 3 + , Pb4 + ) were studied on the basis of a general concept which relates characteristic excited states to typical photophysical and photochemical processes. The photochemistry is dominated by metalcentered sp (s2) and ligand to metal charge transfer (s°) excited states which are capable of inducing inter- and intramolecular redox reactions