Redox‐triggered chiroptical switching activity of ruthenium(III)‐bis‐(β‐diketonato) complexes bearing a bipyridine‐helicene ligand.

Abstract: The charged, electroactive bipyridine‐helicene‐ruthenium(III) complex [<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻ has been prepared from 3‐(2‐pyridyl)‐4‐aza[6]helicene and a Ru‐bis‐(β‐diketonato)‐bis‐acetonitrile precursor (β‐diketonato: 2,2,6,6‐tetramethyl‐3,5‐heptanedionato). Its chiroptical properties (electronic circular dichroism and optical rotation) were studied both experimentally and theoretically and suggest the presence of 2 diastereoisomers, namely (P,Δ)‐ and (P,Λ)‐[<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻ (denoted jointly as (P,Δ*)‐[<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻) and their mirror‐images (M,Λ)‐ and (M,Δ)‐[<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻ ((M,Δ*)‐[<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻). The electrochemical reduction of (P,Δ*)‐[<bold>4</bold>]^{<bold>.</bold>+},PF₆⁻ to neutral complex (P,Δ*)‐<bold>4</bold> was performed and revealed strong changes in the UV‐vis and electronic circular dichroism spectra. A reversible redox‐triggered chiroptical switching process was then achieved. [ABSTRACT FROM AUTHOR]