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

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 pi-pi stacking, different selfassembly structures were obtained in the self-assembly process, which were all hydrophobic with the contact angles of 103 degrees -140 degrees. 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. 1H 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.