Reactions of the complex trans-[RuCl4(Hind)(2)](-) (Hind = indazole), which is of clinical relevance today, with both the DNA model nucleobase 9-methyladenine (made) and the thioethers R2S (R = Me, Et), as models of the methionine residue in biological molecules possibly acting as nitrogen-competing sulfur-donor ligands for ruthenium atom, have been investigated to get insight into details of mechanism leading to antitumor activity. Three novel ruthenium complexes, viz., [(RuCl3)-Cl-III(Hind)(2)(made)], 1, [(RuCl2)-Cl-II(Hind)(2)(Me2S)(2)], 2, and [(RuCl2)-Cl-II(Hind)(2)(Et2S)(2)], 3, have been isolated as solids. Oxidation of 2 and 3 with hydrogen peroxide in the presence of 12 M HCl in chloroform afforded the monothioether adducts, viz., [(RuCl3)-Cl-II(Hind)(2)(Me2S)], 4, and [(RuCl3)-Cl-II(Hind)(2)(Et2S)], 5. By dissolution of 2 or 3 in DMSO, replacement of both R2S ligands by DMSO molecules occurred with isolation of trans, trans, trans[(RuCl2)-Cl-II(Hind)(2)(DMSO)(2)], 6. The products were characterized by elemental analysis, IR, UV-vis, electrospray mass spectrometry, cyclic voltammetry, and X-ray crystallography (1(.)CH(2)Cl(2)(.)CH(3)OH and 1(.)1.1H(2)O(.)0.9CH(3)OH, 2, and 5). The first crystallographic evidence for the monofunctional coordination of the 9-methyladenine ligand to ruthenium via N7 and the self-pairing of the complex molecules via H-bonding, using the usual Watson-Crick pairing donor and acceptor sites of two adjacent 9-methyladenine ligands, is reported. The electrochemical behavior of 1-5 has been studied in DMF and DMSO by cyclic voltammetry. The redox potential values have been interpreted on the basis of the Lever's parametrization method. The E-L parameter was estimated for 9-methyladenine at 0.18 V, showing that this ligand behaves as a weaker net electron donor than imidazole (E-L = 0.12 V). The kinetics of the reductively induced stepwise replacement of chlorides by DMF in 4 and 5 were studied by digital simulation of the cyclic voltammograms. The rate constant k(1) has been determined as 0.9 +/- 0.1 s(-1), which obeys the first-order rate law, while k(2) is concentration dependent (0.2 +/- 0.1 M1-n,S-1 with n > 1 for 4 mM solutions of 4 and 5), indicating higher-order reactions mechanism.