A supramolecular self-assembly material based on a quinoline derivative and its sensitive response toward volatile acid and organic amine vapors

Abstract

A new gelator 1, containing a quinoline group, was designed, synthesized, and fully characterized. It was found that a stable organogel of 1 could be obtained in some solvents, including ethanol, acetonitrile, n-hexane, petroleum ether, and DMSO. It is worth mentioning that a supragel was formed in hexane and petroleum ether with critical gel concentrations of 0.16% and 0.17%, respectively. The self-assembly process of gelator 1 in the above five solvents was carefully investigated by FESEM, UV-vis, FL, FTIR, XRD, and water contact angle experiments. It was found that gelator molecule 1 could self-assemble into different self-assembly structures with different surface wettabilities – from super-hydrophilicity to super-hydrophobicity – in the self-assembly process. The organogel of 1 that was formed in acetonitrile could emit strong light when compared with that emitted by organogel 1 in the other four solvents under the stimulation of 365 nm light. At the same time, the fluorescence emission of the organogel state had a red-shift of 70 nm when compared with that of the solution state. The fluorescence emission of molecule 1 in solution and its gel state was further and well verified via theoretical calculations. The fluorescence emission of the acetonitrile solution of gelator 1 could reversibly respond to TFA and TEA, along with a change in the maximum emission wavelength between 382 nm and 458 nm, in turn. The xerogel of 1 formed in acetonitrile exhibited a sensitive responsive ability towards TFA and TEA. More interesting are the different changes in behavior of the fluorescence emission of molecule 1 in solution and the xerogel state in response to TFA and TEA. This research will provide a new way to design multi-functional soft matter materials that show a response to volatile acid and organic amine vapors.