Synthesis and Characterization of a Ruthenium(II)-Based Redox Conjugate for Reagentless Biosensing (original) (raw)

Isomers of dichlorobis(2-phenylazopyridine)ruthenium(II) [Ru(azpy) 2 Cl 2 ], especially the so-called a isomer, display remarkably high cytotoxicities against human tumor cell lines. Unfortunately, the parent [Ru(azpy) 2 Cl 2 ] compounds are poorly water-soluble. In this paper the synthesis and characterization of the new water-soluble ligand 2-phenylazopyridine-5-sulfonic acid (Hsazpy) is described. Use of this ligand in reaction with RuCl 3 gave two isomers, which were isolated as aand b-[NEt 4 ] 2 [Ru(sazpy) 2 Cl 2 ]. The compounds have been fully characterized by (2D) NMR spectroscopy. The molecular structure of the a isomer of [NEt 4 ] 2 [Ru(sazpy) 2 Cl 2 ]Á2H 2 O has been determined by single-crystal structure analysis. The packing in the crystal structure of a-[NEt 4 ] 2 [Ru(sazpy) 2 Cl 2 ]Á2H 2 O shows an interesting hydrogen-bonding pattern in which two water molecules are involved. One water molecule bridges between a Cl ligand and a SO 3 À group within one ruthenium moiety, the other water molecule forms a bridge between two SO 3 À groups from two different ruthenium centers, resulting in a chain-like structure. Preliminary evaluation of the cytotoxicity by means of the IC 50 value in A2780 cell line classifies a-[NEt 4 ] 2 [Ru(sazpy) 2 Cl 2 ] as non-toxic, but this does not rule out other anticancer activities.