The Properties Of Organogels And Fluoride Ion Colorimetric Sensor Containing Amide Groups

Recently, organogels formed by the low molecular weight gelatorswith different organic solvents have been the focus of much attention dueto their unique features and potential applications. Anions areubiquitous and play a crucial role in a wide range of chemical andbiological processes. Because the gel–sol transition allows naked eyedetection and the gels are more convenient to use, anion-responsive gelshave attracted increasing attention and some reports on anion-tuningorganogels have been reported. However, until now, the organogel systemswhich showed both reversible color change and sol-gel transition by anionstimulus were still limited.This paper aimed at investigating the organogels andanion-responsive behaviors of R8series containing amide groups withuv-vis absorption spectroscopy, infrared spectroscopy (IR) and scanningelectron microscopes (SEM),1H nuclear magnetic resonance (NMR) spectrum.The mechanism of the gel formation, the relationships between themolecular structure and gel ability, and the mechanism of anionic responsewere discussed in detail, which hope to provide effective theoreticalsupport for the development of anion recognition and probe design.In this paper, the main conclusions as follows:(1) The intermolecular hydrogen bonding between C=O and N-H groupwas the major driving force for the formation of self-assembling gelsprocesses, and the van der Waals force between alkyl chain also plays avery important role to the stability of the gel.(2) The terminal substituent is very important for gel behaviors. To the compounds having same structure, the gel ability of compounds withterminal nitro substitution is much stronger than that of with terminalamino substitution.(3) The terminal alkyl chain length is closely related to the gelability. The gel ability of compounds with long alkyl chain is strongerthan that of compounds with short alkyl chain.(4) The terminal substituent has important influence on theanion-responsive behaviors. the anion-responsive ability of compoundswith terminal nitro substitution is much stronger than that of withterminal amino substitution.(5) The number of hydrogen proton has an important impact on theanion-responsive behaviors. Anion-responsive ability of hydrazidederivatives containing two NH protons is stronger than that of amidederivatives containing a NH proton.(6) A possible mechanism of F anion induced gel-sol transition andcolor change for R8-NO2was proposed: Upon the addition of the F-, thehydrazide NH group perhaps underwent a deprotonation process. Itdestroyed the intermolecular hydrogen bonding between C=O and N-H groupswhich is the main driving force that supported gel formation, andsubsequently caused the gel-sol transition. Meanwhile, the color changeof gel was mainly attributed to the extended conjugated system formedthrough the adjacent phenyl group and a five-membered ring.