Design,Synthesis Of 1 2,3-Triazole Derivatives As Fluorescent Molecules And Investigation On Its Photoluminescence Properties

In the past decade,1,2,3-triazole has emerged as a novel molecular scaffold for the development in synthetic chemistry,materials science and pharmaceutical industry owing to the great progress made in the synthesis of triazole derivatives.Due to its unique five-member-ring heterocyclic structure,triazoles could adopt a variety of coordination modes with metals to serve as an excellent ligand for transition metal catalysis.1,2,3-triazole has also been applied as the fluorescence materials.In the past,a great number of studies has been focusing on directly using 'Click chemistry' to link the functional groups and fluorescent active structures by generating triazole moiety as a connection.In other case,triazole structures was used as a ligand to the fluorescent structures,so to achieve both functionalized and fluorescent active structures.However,as far as we know,there are few studies on triazole as the core structure for the fluorescent molecules'synthesis and functionalization.In general,two types of regioselective products have been observed in the 'Click reaction'.N1 substituted triazole has no significant photoluminescence properties.On the other hand,the N2-aryl substituted 1,2,3-triazoles have been reported to possess good photoluminescence properties and excellent photostability in the UV/blue reign.Inspired by these unique findings,we have designed synthesis of a series of N2 substituted triazole as the fluorescent molecules.The photoluminescence properties were also explored and addressed in this thesis.The original research results are as follows:(1)A series of Triazole-imidazole(TA-IM)were designed and synthesized and found to generate the emission wavelength of 330-380 nm and up to 98%quantum.Intramolecular hydrogen bonds were observed with incorporation of imidazole moiety with the triazole ring C-4 position.This has successfully avoided the twisted conformation caused by the lone pair electron repulsion between nitrogen at C-4 position substituents and N3-position of triazole ring.Furthermore,compound TA-IM 5a as a fluorescence was used as a fluorescent sensor for silver cation detection in aqueous solution.The sensor can detect and identify silver ions rapidly(<30 s)with low detection limit(9.4 nmol/L).The Wider range of pH(4.0-10.0),realizing the efficient,ultrafast and selective detection of trace silver ions in the aqueous solution(2)A class of fluorescent active N2-aryl substituted triazole molecules with yellow-green fluorescence emission were synthesized by introducing benzoyl,cyano,acetyl,ethoxyl and other electron acceptors directly into the C-4 position of the triazole ring and introducing electron donor groups such as p-dimethylaminophenyl and p-Diphenylamine phenyl at the N2 position.The fluorescence emission of these triazole compounds in THF solution is 351-542 nm with the quantum yield up to 96%.The emission wavelength of these triazole compounds in solid state is at 362-513 nm with the fluorescence quantum efficiency up to 43%.Most of the structures also exhibited aggregation-induced emission.In addition,the compounds NAT-2c,3c,3e,3g and 3m also demonstrated mechanochromic properties.The red shift of fluorescence emission from 11 to 35 nm can be observed by physical grinding,and the initial emission can be recovered by heating or fumigation of organic gas.Through the single crystal structure study and functional density calculation of these molecules,the relationship between their structural changes and their photophysical properties is systematically explored.We found that the fluorescence emission of triazole molecule could show red-shift by introducing electron-withdrawing groups such as benzoyl group at C-4 position and electron-withdrawing groups at N2 position.The quantum yield of C-5 substituted triazole can be significantly increased by linking substituents with smaller steric hindrance.Too small twist angle between triazole and its C-4 benzoyl group cannot produce piezochromism.(3)Bis-TA-Py-2,4 as a bistriazole-pyridine derivative was designed and synthesized.The photophysical properties of Bis-TA-Py-2,4 in solution and in solid state were studied.The emission wavelength of these bistriazole-pyridine derivatives in ethanol solution ranges from 368 to 495 nm,with the quantum yield up to 90%.In the solid state,the emission wavelength ranges from 374 to 457 nm,with the quantum yield up to 57%.These molecules exhibit a sensitive fluorescence response to acid vapor in the solid state,and a new fluorescence emission signal appeared between 567 nm and 614 nm.Bis-TA-Py-2b and 4b exhibited significantly different proton binding ability based on different substituent positions of triazole mainly because,the compound Bis-TA-Py-4b exist a more twisted conformation in their solid state.The fluorescence emission response of the tridentate ligands Bis-TA-Py-2b and 4b to metal ions was investigated.It was found that the change of the substituent structure of triazole had a significant effect on the coordination ability of these molecules.The fluorescence of complexes formed by those triazole compounds had significant solvent effect.The multiple fluorescence stimulus response properties of the above triazole derivatives provide a novel perspective for the application of triazole.