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The investigation of fac-[[Re[(CO).sub.3][([H.sub.2]O).sub.3]].sup.} cation shows that the putative DNA-binding species accounting for the biological activity of related Re(I) complexes, binds reversibly to N7 and 6-oxopurine nucleotide monophosphates (NMPs), in contrast to Pt(II) anticancer drugs.

The facile preparation of a ruthenium-labeled nucleoside was reported. Spectroscopic studies of 5-(Ru(bpy)2-(4-m-4'-pa-bpy))2+-2'-deoxyuridine showed that favorable photophysical properties associated with Ru(bpy)(sub 3)(super 2+), such as being a potent oxidant and reductant in its excited state and possessing a significant, excited state lifetime, were retained. In addition, the excited electron was localized on the uridine-modified bipyridine, the excited-state dipole was directed toward the nucleoside and the excited state was long-lived.

HPLC was employed to measure the rate of complexation between trans-(Pt(NH3)2(H2O2)2)2+ with two model nucleobases, inosine and 1-methylinosine, in aqueous solution at 298.2 K and pH = 2.8-9.6. The results, which showed that 2-methylinosine yields only N7-bound complexes, demonstrated the stepwise formation of 1:1 and 1:2 complexes from an excess of the nucleobase with the N7 binding mechanism predominant in 1:1 complexation.

Intervalence absorption spectroscopic studies show that an inert electrolyte exhibits significant influence on the energetics of optical electron transfer (ET) in (NC)5Fe(III)-bis(pyridyl)ethylene-Fe(II)(CN)(sub 5)(super 5-). A model incorporating energetic consequences of stepwise ion pairing explains the above compound in different ionic strength solutions of LaCl3, CaCl2 and NaCl. This model explains the optical intervalence properties of (NH3)5Ru(III)-4, 4'-bpy-Ru(II)(NH3)(sub 5)(super 5+) in aqueous Na2SO4 solution. Ion-pairing-stimulated symmetry reduction and subsequent restoration influence optical electron transfer.

The mixing of 5-substituted uracils and uridines (X = F, Cl, Br, I and COOH as 5-substituents) with Ru(hedta)(H2O)1- causes complexation by the eta(super 2) and N-3 binding modes, except for the substituents X = CH3 and COOH. A significant increase in isomer distribution occurs as a function of the withdrawing character of X, with the maximum value at 85% eta(super 2) coordination for X = Cl. A small decrease in the amount of eta(super 2) isomer occurs for the Br- and I-substituted ligands because of modest steric effects. Isomers of both eta(super 2)- and N-3-coordinated complexes occur for 5-fluoroudine.

The formation reactions of the complexes of Pd(R4en)(H2O)2(super 2+), where R4en = N-substituted ethylenediamine and R = H, Me, Et, with ribose, adenosine, inosine and guanosine 5'-monophosphate were studied as a function of monophosphate concentration and temperature in the pH range of 4 to 5. The nucleotides reacted faster than the nucleosides, indicating the transition state stabilization effect by the monophosphate group. Furthermore, the complex formation rate constants of ribose monophosphate were smaller than those of inosine but larger than those of adenosine.

Complex formation between the diaqua palladium(II) complex of ethylenediamine and adenosine or inosine is a two-step process. The reaction rate depends on the nucleoside concentration and, in the case of adenosine, on the pH level. The adenosine complex is less stable than the inosine complex, probably due to exocyclic amine (6-NH2) group interference. Steric hindrance is more pronounced with the inosine complex, where N(1) is already coordinated to the metal center and only N(7) is available for the other moiety. The mechanism therefore involves more of an associative ligand substitution, as indicated by the activation parameters.