engleski

Formation, photophysics, and photochemistry of cadmium(II) complexes with 5,10,15,20-tetrakis(4-sulphonatophenyl)porphyrin and its octabromo derivative: the effects of bromination and the axial hydroxo ligand

In slightly alkaline solution (pH = 8) Cd(II) ion and 5, 10, 15, 20-tetrakis(4- sulphonatophenyl)porphyrin form a kinetically labile complex, in which the metal center is located out of the ligand plane, partly due to the effect of the axial hydroxo ligand. Both acidification and irradiation at the Soret-band can result in the dissociation of the axial ligand, forming a less distorted structure. Besides, irradiation of both types of metalloporphyrins promotes an irreversible ligand- to-metal charge transfer leading to the oxidative degradation of the coordinated porphyrin. Under same conditions, in the case of the octabromo derivative of this water-soluble porphyrin the distorted structure accelerates the formation of the corresponding complex with Cd(II), compared to its reaction with the parent, unbrominated ligand. The structure of this porphyrin strongly distorted by the bromo substituents significantly affects the characteristic features of the absorption (and emission) spectra, red-shifting the position of the main bands of this metalloporphyrin compared to those of the complex with the non-brominated ligand.

water-soluble porphyrin ; sitting-atop complex ; cadmium(II) ion ; photochemistry

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