Synthesis, structural characterization, solution chemistry, and preliminary biological studies of the ruthenium(III) complexes [TzH][trans-RuCl 4(Tz)2] and [TzH][trans-RuCl4(DMSO)(Tz)] ·(DMSO), the thiazole analogues of antitumor ICR and NAMI-A

Two ruthenium(III) complexes bearing the thiazole ligand, namely, thiazolium (bisthiazole) tetrachlororuthenate (I, TzlCR) and thiazolium (thiazole, DMSO) tetrachlororuthenate (II, TzNAMI) were prepared and characterized. The crystal structures of both complexes were solved by X-ray diffraction methods and found to match closely those of the corresponding imidazole complexes. The behavior in aqueous solution of both TzlCR and TzNAMI was analyzed spectroscopically. The time-dependent spectrophotometric profiles resemble closely those of the related ICR and NAMI-A anticancer compounds, respectively. It is observed that replacement of imidazole with thiazole, a less basic ligand, produces a significant decrease of the ligand exchange rates in the case of the NAMI-like compound. The main electrochemical features of these ruthenium(III) thiazole complexes were determined and compared to those of ICR and NAMI-A. Moreover, some preliminary data were obtained on their biological properties. Notably, both complexes exhibit higher reactivity toward serum albumin than toward calf thymus DNA; cytotoxicity is negligible in line with expectations. A more extensive characterization of the pharmacological properties in vivo is presently in progress.