Preparation of Organometallic Ruthenium-Arene-Diaminotriazine Complexes as Binding Agents to DNA

The reactions of two diaminotriazine ligands 2,4-diamino-6-(2-pyridyl)-1,3,5-triazine (2-pydaT) and 6-phenyl-2,4-diamino-1,3,5-triazine (PhdaT) with rutheniumarene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(?6-arene)Ru(?2-N,N-2-pydaT)Cl]X (X=BF4, TsO; arene=p-cymene: 1.BF4, 1.TsO; arene=benzene: 2.BF4, 2.TsO). The neutral cyclometalated complex [(?6-p-cymene)Ru(?2-C,N-PhdaT*)Cl] (3) was also isolated. The structures of complexes 2.BF4 and 3.H2O were determined by X-ray diffraction. Complex 1.BF4 underwent a partial reversible-aquation process in water. UV/Vis and NMR spectroscopic measurements showed that the reaction was hindered by the addition of NaCl and was pH-controlled in acidic solution. At pH 7.0 (sodium cacodylate) RuCl complex 1.BF4 was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1.BF4 underwent basic hydrolysis to afford a RuOH complex (5). Fluorimetric studies revealed that the interaction of complex 1.BF4 with DNA was not straightforward; instead, its main features were closely linked to ionic strength and to the [DNA]/complex ratio. The bifunctional complex 1.BF4 was capable of interacting concurrently through both its p-cymene and 2-pydaT groups. Cytotoxicity and genotoxicity studies showed that, contrary to the expected behavior, the complex species was biologically inactive; the formation of a RuOH complex could be responsible for such behavior.