Electrochemical studies of Ru(II) diimine bioconjugates.

The electrochemical behavior of the ruthenium(II) diimine complexes [Ru(CO)(CF 3 CO 2 )(dppene)(5-R-phen)][PF 6 ] (dppene = 1,2-diphenylphosphinoethene; phen = 1,10-phenanthroline; R = H, 1 ; R = NH 2 , 2 ; R = cholestoryl carbamate, 3 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 4 ), [Ru(CO)(H)(4,4′-R-bpy)(R′Ph 2 P) 2 ][PF 6 ] (bpy = 2,2′-bipyridine; R = H, R′ = Ph, 5 ; R = H, R′ = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 6 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, R′ = Ph, 7 ), [Ru(bpy) 2 (5-R-phen)][PF 6 ] 2 (R = NH 2 , 8 ; R = cholestoryl carbamate, 9 ; R = 1,2-dihexadecanoyl- sn -glycero-3-phosphoethanolamine, 10 ) is reported. Complexes 1 – 6 give cyclovoltammetric (CV) responses with multiple ill-defined reduction waves and one oxidation wave, all of which were chemically irreversible. Complexes 5 and 7 , containing axially coordinating phosphines, showed reversible oxidation and reduction CV responses, while 6 showed redox waves similar to 3 . Complexes 8 – 10 show a metal-centered irreversible oxidation around +1.4 V that, in the case of 8 and 9 , is heavily modified by adsorption phenomena. In the negative part of the CV, 9 and 10 show a single chemically and electrochemically reversible 1e − reduction both at E °′ = −1.29 V, about 500 mV cathodically shifted with respect to 8 . The interactions of complexes 1 and 2 with bovine serum albumin (BSA) and double stranded DNA (ds-DNA) were also studied by electrochemical methods. Both complexes showed strong binding to BSA. Evidence for intercalation of both complexes with DNA is presented, with 1 showing a stronger interaction than 2 . [ABSTRACT FROM AUTHOR]