Molecular structures, redox properties, and photosubstitution of ruthenium(II) carbonyl complexes of porphycene

Two ruthenium(II) carbonyl complexes of porphycene, (carbonyl)(pyridine)(2,7,12,17-tetra-n-propylporphycenato)ruthenium(II) (1) and (carbonyl)(pyridine)(2,3,6,7,12,13,16,17-octaethylpor-phycenato)ruthenium(II) (2), have been structurally characterized by single-crystal X-ray diffraction analysis. Cyclic voltammetry has revealed that the porphycene complexes undergo multiple oxidations and reductions in dichloromethane and the reduction potentials are highly positive compared to porphyrin analogs. UV-light irradiation (400 nm or shorter wavelength region) of a benzene solution of 1 and 2 containing external pyridine leads to dissociation of the carbonyl ligand from the ruthenium(II) centers to give the corresponding bis-pyridine complexes. The identical reaction has been also studied for a porphyrin derivative (carbonyl)(pyridine)(2,3,7,8,12,13,17,18-octaethylporphyriato)ruthenum(II) (3). The first-order kinetic analysis has revealed that the photosubstitution of all of the compounds occurs in the order of 10^-3 s^-1 at 298 K but proceeds faster for complexes of porphycene (1 and 2) than that of porphyrin (3).