An eleetrochromic variable optical attenuator （ECVOA） was fabricated by layer-by-layer （LBL） assembly of disodium N,N-bis（p-sulfonatophenyl）naphthalenedicarboximide （Naph-SO3Na） and common cationic polymer poly（diallyldimethylammonium） chloride （PDDA）. The UV-Vis absorption spectra of the multilayer films revealed that approximately an equal amount of Naph-SO3Na was assembled in each deposition cycle. Upon one-electron reduction, multilayer films exhibited intense absorption around 452 nm and also a broad absorption band from 1200 nm to 1900 nm. Owing to the improved ionic conductivity, the optical attenuation at 1550 nm of the films showed rapid response time and reached 1.3 dB/μm within 5 s. These results indicate that layer-by-layer assembly could be an effective method for the preparation of ECVOA operating in near infrared region.
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 n＊-z＊ （SOMO---~LUMO） transitions of the radical anion of AQI and strong negative Cotton effects in the same spectral region. With further reduction at -1000 mY, 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-[3fl-cholest- 5-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.
