Tetraammine ruthenate complexes: Cationic SAMs for cytochrome c recognition

Abstract

The redox process of the cyt c metalloprotein was assessed by the cationic SAMs formed with [Ru(CNPy)(NH3)4(1,4-dt)]2+ and [Ru(CNPy)(NH3)4(pyS)]2+ complexes on gold, where CNPy = 4-cyanopyridine, pyS = 4-mercaptopyridine and 1,4-dt = dithiane. The observed cyt c redox potentials are indicative of the native protein form. The voltammograms, however, were observed to be affected by the conformation of the modifiers, determined by SERS spectroscopy. The [Ru(CNPy)(NH 3)4(pyS)]2+ complex, which exhibits trans conformation on the surface, presented a well-defined voltammogram. On the other hand, the gauche conformation of the [Ru(CNPy)(NH3) 4(1,4-dt)]2+ SAM seems to make the assessment of the cyt c hET reaction difficult. The reductive desorption potentials, at -0.52 and -0.64 V vs Ag|AgCl|Cl- for the [Ru(CNPy)(NH3) 4(1,4-dt)]2+ and [Ru(CNPy)(NH3) 4(pyS)]2+ SAMs, respectively, are indicative of the bonding mode with the surface and the π withdrawing capability of the CNpy ligand. © 2006 Sociedade Brasileira de Química.