Axial coordination of azaferrocene to transition metal macrocyclic complexes: photoactivation of the macrocycle

摘要

Azaferrocene, (η~5 - C_4H_4N)(η~5 - C_5H_5)Fe, coordinates to the axial sites of metal macrocylic complexes such as cobaloximes, metalloporphyrins and phthalocyanines. Despite the "three-dimensional" structure of this organometallic ligand, X-ray crystal data and electronic properties of the adducts reveal tight coordination. This may be due to significant π acceptor properties of azaferrocene. The photochemical properties of the macrocyclic complex-azaferrocene adducts (or macrocyclic' complex in the presence of azaferrocene) have been examined. It has been established that the macrocyclic complex can be easily photoreduced either at the metal centre or at the macrocycle. This photoreactivity was attributed to the photoinduced electron transfer (PET) from azaferrocene to the macrocycle. The reverse transfer is hampered by fast decomposition of the azaferrocenium system (only in the case of methylcobaloxime complex was a reversible PET observed by laser flash photolysis). In all experiments azaferrocene proved much more efficient than classical organic electron donors (amines).