ELECTRONIC-SPECTRA, RESONANCE RAMAN-SPECTRA AND SOLUTION PROPERTIES OF WATER-SOLUBLE CU(II), NI(II) AND CO(III) PORPHYRINS

The Cu(II), Ni(II) and Co(III) complexes of the following water-soluble meso-substituted porphyrins were prepared: tetrakis(2-N), (3-N-) and (4-N-)methylpyridylporphyrin (1, 2, 3), tris(4-N-methylpyridyl)monophenylporphyrin (4), two isomeric bis(4-N-methylpyridyl)diphenylporphyrins (5, 6) and tetrakis(4-N,N,N-trimethylanilinium)porphyrin (7). The metalloporphyrins were characterized by UV-Vis and resonance Raman spectroscopy. The Cu(II) porphyrins are always four-coordinate; the complexes of more basic porphyrins, 4 through 7, have a marked tendency to aggregate in aqueous and electrolyte solutions. In aqueous solution, the Ni(II) complexes of more acidic porphyrins, 1 through 4, exist as equilibrium mixtures of four-coordinate square-planar species and six-coordinate diaquo forms; the relative amount of the latter increases with the acidity of the porphyrin. The Ni(II) derivatives of other porphyrins, 5 through 7, are four-coordinate in water, but tend to form aggregates. The Co(III) complexes are six-coordinate in all cases. Resonance Raman spectra have been recorded for all complexes, band assignments are given, and structure-sensitive bands are discussed. © 1990.