The Studies Of Photo-Responsive And Anion-Responsive Properties Based On Azobenzene Derivatives

Low molecule organogelators owning the responsiblity to the physical or chemical stimuli, such as light, mechanical stress, molecular recognition, ultrasonic, ion stimulation, etc., have been attracted comprehensive attentions due to their potential applications in chemical sensor, molecular recognition,smart materials and other fields. In this thesis, we have designed and synthesized two kinds of low molecular organogelators an azobenzene derivative(BNB-t4) with amide groups and azobenzene derivatives(AOB-t4) with 1,3,4-oxadiazoles. The photophysical properties and gelation ability of AOB-t4,the anionic response behavior and recognition ability of BNB-t4 have been systematically investigated. On the basis of the obtained experimental results, the involved physical and chemical mechanisms have been discussed as well in this work.The specific results can be listed as follows:1. AOB-t4 has been synthesized with azo phenyl groups and oxadiazoles as rigid primitives, and alkoxy as tail substituent. BNB-t4 was synthesized with azo phenyl group, amide groups as rigid primitives,and alkoxy as tail substituent. The element analysis and structure characterization of these two molecules have been performed by using 1HNMR spectra, FT-IR spectra and elemental analysis. The obtained results confirm the successful systhesis of these two kinds of compounds.2. The experimental results indicate that AOB-t4 gelator can form a stable organogels in the medium polarity solvent, such as dichloromethane, chloroform, and acetone etc. The mechanism for the formation of gel can be attributed to the synergy of intermolecular hydrogen bond, azobenzene ?-? stacking and van der Waals force via the alkyl chain, which has been proved by the FT-IR spectrum, UV-visiblespectroscopy, and theoretical analysis. With the UV irradiation, it has been observed the isomerization transformation of AOB-t4 from trans- to cis- conformation both in solution and gel states. Meanwhile, the transformation of morphology from fiber to particle and an aggregation induced fluorescence enhancement have also been observed in AOB-t4 gel. The results indicate that the photoisomerization of AOB-t4 plays an important role in the fluorescence enhancement for AOB-t4 dilute solution and the self-assembly structure transformation in gel state.3. In this thesis, it has been observed that the BNB-t4 can form stable organogels in the medium polarity solvent, such as benzene, toluene, dichloromethane, chloroform, etc., while it is dissolved in the larger polarity solvent and insoluble in the nonpolar solvents. The anion response behaviours study of the compound BNB-t4 demonstrates a good selectivity and high sensitivity in sensing F-, H2PO4- and Ac Oions, which can be observed from the spectral changes and by “naked-eye”. For the recognition mechanisms, it have been confirmed that these three kinds of anion can interact/protonate with the BNB-t4 through hydrogen bonding via –NH and –OH groups. With the excess of these anions, the deprotonation will take place, especially for fluoride anion. The colorimetric sensing property of BNB-t4 in sensing fluoride anion can be recycled upon the addition of HSO4-ions into the solution. As a result, this switchable spectral property of BNB-t4 in recognition for fluoride anion could also be used as a molecular logic gate.