Fluorescent naphthalimide-based supramolecular gel system for detection phosgene, sulfoxide chloride and oxalyl dichloride

Abstract

A novel naphthalimide-based gelator ( 1 ) was designed and synthesized, which could form fluorescent gels in six kinds of solvents for all the solvents we tested. The self-assembly process of molecule 1 in six solvents was studied by different technologies. Under the main driving force of hydrogen bonding and π-π stacking, different self-assembly structures were obtained in the self-assembly process, which were all hydrophobic with the contact angles of 103°-140°. Interestingly, compound 1 exhibited sensitive response ability towards high active acyl chlorides due to its weak nucleophilicity of amino at 4-position in naphthalimide. Phosgene, sulfoxide chloride and oxalyl dichloride could be detected via compound 1 in solution, gel and xerogel states, and expressed the change of fluorescence, color and gel state. Especially for three kinds of acyl chlorides gases, xerogel 1 could detect phosgene, sulfoxide chloride and oxalyl dichloride with their corresponding low limits of detection of 23 ppb, 0.25 ppm and 0.19 ppm, respectively. 1 H NMR titration and HRMS experiments well explained the detection mechanism, which was that the reaction between acyl chloride and 4-amino group of molecule 1 weakened or prohibited the original ICT process, and further brought its fluorescent change and affected the noncovalent interaction. This research will bring a new way for construction multi-functional self-assembly system for detection of acyl chlorides.