Fabrication And Fluorescent Sensory Properties Of Non-traditional ?-gels Based On Carbazole Modified Pyrimidine Derivatives

Recently,low molecular weight organogels(LMOGs)have received much attention on account of the potential applications in optoelectronic devices,field-effect transistors,chemosensors,near-IR probes.Generally,organogels are formed from the organogelators containing traditional gelation group based on hydrogen-bonding units(e.g.,amide,amino acid,sugars or urea)and/or auxiliary groups(e.g.,long alkyl chains or cholesterol),which lead to low atom economic and tedious synthesis.However,the ?-gelators without traditional gelation groups would promote the communication between the functional ?-conjugated units due to the absence of the domain formed from auxiliary groups.Therefore,the synthesis of non-traditional organogelators attracted increasing interest.Meanwhile,the nitrogen-containing heterocyclic compounds have the advantages of many reaction sites,high reactivity,easy modification,photostability,thermal stability and strong fluorescence emission ability.Therefore,the nitrogen-containing heterocyclic compounds have important applications in the photoelectric functional materials.In this paper,we study the synthesis,self-assembly and fluorescence sensing properties of nitrogen-based heterocyclic compounds.Some creative results have been obtained,which were outlined below:We have synthesized a series of new pyrimidine derivatives modified with carbazole(CM,CMH,CMCl and CMBr)and tert-butyl carbazole(TCM,TCMH,TCMCl and TCMBr).It was found that CM,CMCl,CMBr,TCM,TCMCl and TCMBr without traditional gelation groups could self-assemble into organogels with intense emission.It was found that V-shaped ?-conjugated skeleton and ?-? interactions were essential for the organogelation.It was interesting that the organogels could be destroyed by adding TFA(trifluoroacetic acid),accompanied with the quenching of the emission on account of the protonation of pyrimidine unit.In particular,the xerogel-based film of TCM emitting strong bluish green light could be used as fluorescent sensor to detect TFA vapor with the decay time and detection limit of 0.6 s and 95 ppb,respectively.Such high performance of the xerogel-based film in fluorescent responsive ability was originated from the high surface-to-volume ratios of nanomaterials and the large space in 3D networks,which were favorable for the adsorption and diffusion of the analytes.We provided new strategy for the design of non-traditional ?-gelators and the fabrication of fluorescent sensory materials with high performance to detect gaseous analytes.We have synthesized new pyrimidine-containing ?-iminoenolate CPPA and TCPPA and their difluoroboron complexes CPPAB and TCPPAB.It was found that only TCPPA and TCPPAB bearing tert-butyl carbazole could form organogels in some selected solvents,suggesting that tert-butyl played key role in the gel formation.It should be noted that ?-? interactions were the main driving forces for the gelation of the full-conjugated TCPPA and TCPPAB without any traditional gelation group.Meanwhile,the xerogel-based film of TCPPAB emitting strong yellow light could be used as fluorescent sensor to detect TFA vapor with the decay time and detection limit of 0.8 s and 260 ppb,respectively.Interestingly,the ?-iminoenolate difluoroboron complexes CPPAB and TCPPAB exhibited MFC behaviors,and the reversible changes in the emitting colors were performed via grinding and fuming.The XRD patterns for the MFC dyes in different solid states illustrated that the transformation between crystalline and amorphous states led to mechanofluorochromism.