Synthesis,Self-Assembly And Fluorescent Sensory Properties Of Iminazole And Chalcone Derivatives

Recently,low molecular weight organogels(LMOGs)have received much attention on account of the potential applications in optoelectronic devices,field-effect transistors and chemosensors.Therefore,the design and synthesis of novel organic molecule gelatas with desired optical and electronic properties has attracted much attention.The nitrogen-containing heterocyclic compounds(such as carbazole,phenothiazine,iminazole)have the advantages of many reaction sites,high reactivity,easy modification,thermal stability and strong fluorescence emission ability,which have important applications in the photoelectric functional materials.Herein,we synthesized a series of tert-butylcarbazole,phenothiazine,anthracene-modified imidazole derivatives and phenothiazine-modified 2-hydroxychalcone derivatives,and excellent self-assembling abilities.Meanwhile,the photochromic,mechanofluorochromic behavior and fluorescence sensing properties was studied.Some creative results have been obtained,which were outlined below:Four new imidazole-based compounds(Cbz-IM,PTZ-IM,ANT-IM and Cbz-PIM)were synthesized.Interestingly,they showed photochromic behaviour.The emission intensity of Cbz-IM decreased obviously at 385 nm upon exposure to UV light at 365 nm.Upon irradiation 60 s,a new band at 500 nm emerged in DCM,following the color of the solution from dark blue to green.At the same time,the solid powder also showed similar photochromic behavior under UV irradiation.PTZ-IM and ANT-IM exhibit similar photochromic behavior in solid powder or solution.According to the electron spin resonance(ESR)spectra,we deemed that the formation of a new species of radical led to the emitting color change of Cbz-IM stimulated by UV light.Imidazole derivatives had not only photochromic properties,but also self-assembly and fluorescence sensing properties.It was found that Cbz-IM and Cbz-PIM with a tert-butyl moiety could gel in cyclohexane,1,4-dioxane,acetonitrile and under ultrasound stimulus,but PTZ-IM and ANT-IM without a tert-butyl group failed to form an organogel in the selected solvents,revealing that tert-butyl played an important role in gel formation.The changes of UV-vis absorption spectra and fluorescence emission spectra in the gelation process indicate that ?-? interaction is the main driving force of molecular self-assembly.X-ray diffraction patterns of xerogels indicated that Cbz-IM and Cbz-PIM molecules self-assembled into lamellar structures in the gel state.In particular,xerogel-based films of Cbz-IM emitted strong blue light and the blue-emitting film was changed into the one emitting green light towards TFA vapor.The response time for the film in the detection TFA vapor was 1.21 s.When the concentration is below 112 ppm,the detection limit of the xerogel-based film of Cbz-IM was ca.208 ppb towards TFA vapor.New D-?-A type phenothiazine modified 2-hydroxychalcone analogues PTNn(n = 2,4,8,12,16)have been synthesized,and exhibited reversible mechanofluorochromism.Notably,the emission of PTNn in different solid-state was in the range of 600-800 nm,and the red-emitting mechanofluorochromic(MFC)materials were seldom reported.For example,the as-synthesized crystals of PTN16 emitted red light cantered at 667 nm,and were changed into deep red emitting ground powders after grinding.The fluorescence emission could be recovered to original state when the ground powders were fumed with DCM vapor or heated.The MFC processes were accompanied with the transformation between crystalline and amorphous states,which could be confirmed based on the results of XRD patterns in different solid-state.Additionally,it was found that the length of alkyl chain affected the performance in mechanofluorochromism for PTNn.The shorter was the carbon chain,and the higher-contrast was the MFC behavior.Moreover,PTN12 and PTN16 bearing long carbon chains could self-assemble into organogels in a certain amount of organic solvents,and the gelation-induced enhanced emission was observed during the organogelation.Therefore,the red light emission can be regulated by the phase transition of the D-?-A type 2-hydroxychalcone analogues.This work provides a new way to design a new type of ?-gel and to build a high-performance chemical sensing material.