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 ruthenium-arene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(η(6)-arene)Ru(κ(2)-N,N-2-pydaT)Cl]X (X=BF(4), TsO; arene=p-cymene: 1·BF(4), 1·TsO; arene=benzene: 2·BF(4), 2·TsO). The neutral cyclometalated complex [(η(6)-p-cymene)Ru(κ(2)-C,N-PhdaT*)Cl] (3) was also isolated. The structures of complexes 2·BF(4) and 3·H(2)O were determined by X-ray diffraction. Complex 1·BF(4) 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) Ru-Cl complex 1·BF(4) was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1·BF(4) underwent basic hydrolysis to afford a Ru-OH complex (5). Fluorimetric studies revealed that the interaction of complex 1·BF(4) 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·BF(4) 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 Ru-OH complex could be responsible for such behavior.