Ru(II) polypyridine complexes with a high oxidation power.: Comparison between their photoelectrochemistry with transparent SnO2 and their photochemistry with desoxyribonucleic acids

The compounds which are discussed in the present review are highly oxidizing Ru(II) complexes. based on various polyazaaromatic ligands, and acting as efficient electron acceptors in the excited state. The photoinduced charge transfer process and the following associated kinetic steps are characterized for the whole series of complexes by quite different techniques and methods. Thus their behaviour in the presence of reductants such as hydroquinone and mononucleotides (guanosine-5'-monophosphate and adenosine-5'-monophosphate) are examined by flash photolysis. spectroelectrochemistry and photoelectrochemistry. II is explained how the light-initiated electron transfer process can be applied for spectral supersensitization of wide band gap SnO2 semiconductor electrodes. Moreover, it is shown that such a knowledge of the behaviour of these photoredox reactions leads to interesting applications of these oxidizing complexes in a biological area, i.e. for the study of nucleic acids. Thus it is illustrated how these compounds can be used as promising photoreagents of DNA. The easy modulation of their size and shape, and their irreversible anchoring on the DNA bases, triggered by the reductive photoelectron transfer process from the guanine bases to the excited complex, allow one to regard these complexes as attractive molecular tools for DNA study and maybe as future possible drugs activatable under visible light. (C) 1998 Elsevier Science S.A.