Synthesis And Gelation Properties Of Acetal-based D-glucose Schiff Base Compounds

As a new class of soft materials,smart gels have attracted much attention in recent years due to their unique stimuli responsive properties.Derived from a platform molecule 2,4-(3,4-dichloro)benzylidene methy-d-gluconate,a series of novel Schiff-based gelators were designed and synthesized.The gelation behaviors and self-assembly mechanism of these compounds were studied in different solvents,the effects of mechanical force on the arrangement of these gelators and the aggregation-induced emission enhancement phenomena of the gel were investigated,and the metal ion stimuli was also explored.Compound 3a and 3d with different alkyl chain lengths were studied in detail.It was shown that the gelation abilities of these compounds depended on the type of the solvents and the length of the alkyl chains of the gelators.The morphology of these gels were observed with AFM and TEM and showed three-dimensional fibrous network structure.UV-Vis,PL and FT-IR showed that the ?-? interactions,hydrogen bond and Van Der Waals force were the driving force for the formation of gels.More importantly,compound 3d exhibited unique mechanochromic behaviors.This interesting phenomenon may due to the transformation of compound 3d between crystalline state and amorphous state,as indicated by the results of ~1H NMR?SEM?XRD and DSC.Compound 3a showed gel-induced emission enhancement phenomena.By comparing the fluorescence spectra of different compounds,it was found that the bending of carbon chain is an important factor for the gel-induced fluorescence enhancement.In addition,we also studied the metal ion stimulation on the Schiff base gelators(compound 3a to 3f)with different coordination groups and different alkyl chain lengths.It was found that the gelation ability of compound 3f was relatively weak due to the bigger space structure of the naphthalene ring.Besides,The stimulation of metal ions on gelators was gradually highlighting with the shorting of alkyl chain lengths,when it was less than or equal to 6,the addition of metal ions made the gel disintegration.UV-Vis showed that the complexes were formed between gelators and Ag+,and some of the hydroxyl groups of the gelators may also participate in the coordination.