Visible and Near-infrared Chiroptical Gels Containing Electrochromic Anthraquinone Imide Groups

A cholesterol-based organogelator bearing an anthraquinone imide (AQI) group was synthesized and characterized. It self-assembled into chiral gels in acetonitrile at low concentrations, which displayed a combination of electrochromic and chiroptical properties. Upon electrochemical reduction at −700 mV, the gel exhibited new absorption bands at around 820 nm corresponding to π*-π* (SOMO→LUMO) transitions of the radical anion of AQI and strong negative Cotton effects in the same spectral region. With further reduction at −1000 mV, a new CD band with a negative Cotton effect in the range from 500 nm to 800 nm appeared concomitant with the variation of absorption spectrum. Thus, with the use of electrochromic AQI chromophore as a switch-responsive unit and the stable gel of compound N-[3β-cholest5-en-3-yl N-(2-aminoethyl) carbamate] anthraquinone-2,3-dicarboxylic imide as a chiral scaffold, a redox-triggered chiroptical switch operating in visible and near-infrared region was realized.