Electrochemical studies of Ru(II) diimine bioconjugates

• The electrochemical behavior of a series of Ru(II)-diimine complexes is discussed.
• Strong binding to bovine serum albumin of two model complexes was observed.
• Evidence for differential intercalation of the model complexes with DNA is presented.
• Phosphine ligand has a strong impact on the electrochemical behavior.

The electrochemical behavior of the ruthenium(II) diimine complexes [Ru(CO)(CF3CO2)(dppene)(5-R-phen)][PF6] (dppene = 1,2-diphenylphosphinoethene; phen = 1,10-phenanthroline; R = H, 1; R = NH2, 2; R = cholestoryl carbamate, 3; R = 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, 4), [Ru(CO)(H)(4,4′-R-bpy)(R′Ph2P)2][PF6] (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)][PF6]2 (R = NH2, 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.

The electrochemical behavior of a series of Ru(II)-diimine complexes is discussed. In particular, electrochemical techniques were use to evaluate the binding to bovine serum albumin of two model complexes. Moreover, evidence for differential intercalation of the model complexes with DNA is presented.Figure optionsDownload as PowerPoint slide