Comparison of the electrochemical reductions of Ru(II) complexes of dipyrido[3,2-a:2′,3′-c]phenazine and 10,12-dimethylpteridino[6,7-f][1,10]phenanthroline-11,13(10H,12H)-dione (an alloxazine analog) in aprotic and mixed aprotic/aqueous media

We obtained and compared voltammetric and coulometric data on the ligand-centered reductions of the complexes [(bpy)2RuII(dppz)]2+ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) and [(bpy)2RuII(pptd)]2+ (pptd = 10,12-dimethylpteridino[6,7-f][1,10]phenanthroline-11,13(10H,12H)-dione; an alloxazine analog) in both aprotic (DMSO) and protic (80 mol% H2O/DMSO pH ∼6.6) media. The (1e−) electrochemical behaviors in the aprotic environment were quite similar. However, in the protic media, the 2e− reduction for the dppz-complex showed very poor electrochemical reversibility compared to the pptd-complex.

Cyclic voltammetry and coulometry were used to compare the dppz-centered reductions in [(bpy)2RuII(dppz)]2+ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) with the analogous reductions in [(bpy)2RuII(pptd)]2+ (pptd = (10,12-dimethylpteridino[6,7-f][1,10]phenanthroline-11,13(10H, 12H)-dione). While the (1e−) electrochemical behaviors in aprotic media (DMSO) were quite similar, significant differences were observed for the 2e− reductions in mixed DMSO/H2O solvents.Figure optionsDownload as PowerPoint slideHighlights
► Electrochemical characterization of two DNA-intercalation complexes.
► Comparison of ligand-centered reductions of dppz and pptd-based Ru(II) complexes.
► Coulometry and cyclic voltammetry in aprotic and protic environments.
► One-electron reductions in aprotic solvent and two-electron in protic solvent.
► Dppz-centered reduction much less reversible (than pptd) in protic solvent.