PHOTONS, ATTRACTIVE REAGENTS IN COORDINATION CHEMISTRY - THE PHOTOCATALYTIC ACTIVATION OF DIOXYGEN BY TRANSITION-METAL PORPHYRINATES

The initiation of chemical reactions of coordination compounds by usin g photons has become an increasingly popular technique for controlling and tuning the reactivity of transition-metal complexes and organomet allic compounds, Rather unusual reaction pathways for transition-metal complexes can be observed by electronic excitation of diverse spectro scopic states of these compounds, Besides stoichiometric redox, dissoc iation, substitution, and rearrangement reactions induced by light, ph otocatalytic processes and photoinduced chain reactions are of particu lar interest. The photocatalytic activation of dioxygen provides an il lustrative example of how photocatalysis can be used for the oxygenati on of selected alkene derivatives, particularly when higher valent tra nsition-metal porphyrinates with additional photochemical sacrificial ligands are used.