Effects of substitution position on electrochemical,electrochromic, optical,and photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives

This study aimed to investigate the effects of substitution position on the electrochemical, electrochromic, optical, and photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives. Therefore, a series of azobenzenen ester derivatives, including azobenzene-4,4′-dicarboxylic acid dialkyl ester derivatives (ADDEDs), azobenzene-3,3′-dicarboxylic acid dialkyl ester derivatives (ADADEs), and azobenzene-3,3′,5,5′-tetracarboxylic acid four alkyl ester derivatives (ATFAEDs), was synthesized in this work, and their electrochemical, electrochromic, optical, and photoresponsive properties were characterized. Substitution position significantly influenced the electrochemical, electrochromic, and optical properties but not the photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives. With regard to stability and response time, the electrochromic properties of azobenzenecarboxylic acid alkyl ester derivatives decreased in the following order: ADDEDs > ATFAEDs > ADADEs. However, ADDEDs, ADADEs, and ATFAEDs can all be reversibly and efficiently photoswitched between trans and cis states upon alternate irradiation at 365 and 440 nm under electrochromic conditions.