Interaction of water soluble metalloporphyrins with nucleic acid bases

Abstract

The interaction of metalloderivatives [Cu²⁺, Zn²⁺ and Co²⁺) of tetrakis (4-N-methylpyridyl)porphyrin (MTMpyP) with nucleic acid bases is described in terms of 1:1 molecular complexes. The binding constants evaluated from optical studies vary as CuTMpyP > ZnTMpyP with a given base and this variation is accounted in terms of structure of the macrocycle. The magnitude of binding constant for adenine complex is larger than that for cytosine complex with a given metal derivative. The Co^IITMpyP undergoes oxidation to CO^IIITMpyP in the presence of molecular oxygen and adenine. ESR studies of the complexes reveal that the π-complexation results in changes in the electronic structure of the central metal ion.