Synthesis And Fluorescence Sensing Properties Of Novel Functional Fluorene Compounds And Triazole Derivatives

Fluorescent organic materials,for example,fluorene,pyrene,styrene,biphenyl and triazole biphenyl have attracted tremendous attention in the field of technology and science.Among of them,fluorene,a major component of fossil fuels,has unique structural features: two benzene rings are fused into one plane by a five-member ring,providing high electron delocalization through increased overlap of ? molecular orbitals between the rings.Fluorene can be directly connected to aromatic hydrocarbon via aromatic coupling at the 2 and 7 positions,yielding a series of fluorene-derived compounds.Triazoles are 5-membered rings,which contain two carbon and three nitrogen atoms.According to the position of nitrogen atoms,the triazoles exist in two isomeric forms which are the 1,2,3-triazole and the 1,2,4-triazole.In the past two decades,a large amount of compounds containing 1,2,3-triazole group have been synthesized and widely used in pesticides,pharmaceuticals,dyes and rubber auxiliaries industries.Based on the electron-rich properties and conjugated structures of triazole and fluorene derivatives,it is important to study their performance in fluorescence sensing.In this paper,six fluorene derivatives,two triazole derivatives were synthesized using fluorine,p-nitroaniline and p-aminobenzoic acid as the starting material.And one copper complex was synthesized using 5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carboxylic acid as ligand.All of them were characterized by IR spectroscopy,1H NMR,13 C NMR and elemental analysis.Some of them were characterized by mass spectrometry,UV–vis spectroscopy,X-ray crystallographic determination and X-ray diffraction(PXRD).Then the three compounds were selected to study their fluorescence sensitivity to small molecules and ions.Simultaneously,the fluorescence quenching phenomenon between them was analyzed by density functional theory(DFT).The specific work of this paper is as follows:1.The 4,4‘-(9,9-dimethylfluorene-2,7-diyl)dibenzoic acid(6)was synthesized using fluorene as the starting material followed by processes of bromination,methylation,Suzuki coupling reaction and hydrolysis reaction.Simultaneously,two novel intermediates dimethyl 5-(7-bromo-9,9-dimethylfluorene-2-yl)isophthalate(3)and methyl 4-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)benzoate(4)was synthesized.2.The 5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carboxylic acid(8),1-(4-carboxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carboxylic acid(10)was synthesized using p-nitroaniline and p-aminobenzoic acid as the starting material followed by processes of diazotization reaction,ring-forming reaction.By using 5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carboxylic acid as ligand,a new complex [Cu(L)2][Cu(L)2(H2O)2](11)was prepared firstly.3.Compound 6 was used as exclusive fluorescence sensor for 2,4,6-trinitrophenol(TNP)and acetate ions.The experimental results suggested a high efficiency for TNP detection with Ksv values of 21215 M-1,which has achieved to micromolar level(10 ?M)of this material.The detection limit(1.39 × 10-6 M)was measured according to the fluorescence intensity changes of Ac O-.At the same time,compound 8,11 was used as exclusive fluorescence sensor for 2,4,6-trinitrophenol(TNP)and they exhibited highly sensitive(Ksv = 393685 M-1 and Ksv = 213269 M-1,respectively)and low detection limit(0.68?M and 0.37?M,respectively)sensing to TNP.4.The fluorescence quenching mechanism of compound 8 with TNP was analyzed by density functional theory(DFT).