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Based on the analysis for recent progress in supramolecular gel and our group’s research, several series of low-molecular-weight gelators were design and synthesized. The design strategies as follow:to obtain stable low concentration supramolecular gel, the long alkyl chain, arygroup and aroyl hydrazonegroup were induced to a same gelator molecule. In order to achieve selective response for special ions, the aroyl hydrazone moieties contain a signal groups such as5-nitropheny furan, naphthol group or quinoline groups were induced into the gelators. By this strategies, a series of anion responsive gelators were obtained. Among these gelators, the gelator F1based on5-(4-nitrophenyl)-2-furan and3,4,5-tris(hexadecyloxy)benzoyl hydrazine groups, which could form a yellow opaque gel in DMF. This gel was characterized by SEM, XRD and IR techniques. Field emission scanning electron microscopy (FESEM) showed the formation of well-developed three-dimensional networks composed of interlocked fibers. F1and F1gels showed quite different emission behavior compared to their solution state. A strong emission compared to that of its diluted solution state was observed from the gel of F1. The results of1H NMR and XRD measurement indicated that the intermolecular H-bonds, Van der Waals interactions and π-π stacking may be self-assembly for the gel formation. It was demonstrated that the gel emission spectra was quenched and color was changed by addition of TBAF (tetra-n-butylammonium fluoride) due to the disruption of intermolecular H-bonds. Gel color and fluorescence recovery when added a protic solvent or an acid, such as methanol or perchloric acid. Compared with the hydrogen bonding self-assembly of gel, the gel presence the long alkyl chain and π-π stacking, the fluoride ion only deprotonation of its hydrogen bonds, color and fluorescence impact, not produce macroscopic damage to the gel state. The4-nitrophenylhydrazone and hexadecyloxy groups based gelator F2and F3had been designed and synthesized. F2could selectively recognize fluoride among different anions tested with color changes from pale yellow to purple for visual detection in DMSO. Simultaneously, it could gel in DMSO0.2-1.5%(w/v), FESEM showed the formation of well-developed three-dimensional networks composed of interlocked fibers. When treated with TBAF (tetra-n-butylammonium fluoride), the gel could undergo deprotonation effect accompanied by color changes. The gel color recovery when added a protic solvent or an acid, such as methanol or perchloric acid. The supramolecular gel could selectively "naked eyes" recognize F-efficiently and conveniently, which could be applied as a F-recogntion materials. Moreover, a quinoline acyl hydrazone and long alkyl chain based gelator F4was designed and synthesized, this gelator employ quinoline as fluorescence signal group. F4could form a stable gel in DMF and emitting a blue fluorescence. When Cu2+was added to the gel, the blue fluorescence was quenched and the color of the gel changed from gray to green. However, when CN-was added into the F4-Cu2+metal organogel, the color and fluorescence were recovered, other anions such as F-, Cl-, Br, I-, AcO-, H2PO4-, HSO4-, CIO4-did not influence with the recognition process for CN-. Therefore, the F4-Cu2+metal organogel could act as a cyanide sensor material.
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