The Synthesis And Fluorescence Properties Of 5-(1,2,4-triazol-1-yl) Isophthalic Acid-based Coordination Polymer

The so-called coordination polymer is a material material with an infinite network structure formed by self-assembly of metal ions or metal ion clusters with certain organic ligands at a certain temperature or a certain pressure.In terms of structure,they often show a large specific surface area.,Adjustable porosity and other advantages,often show high selectivity,high sensitivity,low detection limit,fast response speed and other advantages in fluorescence detection,making it show great potential in emerging synthetic materials.In this article,5-（1,2,4-triazol-1-yl）isophthalic acid and transition metal salts,main group metal salts and rare earth metal salts were selected to synthesize 9 new coordination polymers.A variety of test methods are used to characterize the structure and performance,and the specific experimental contents are as follows:1.Firstly,5-（1,2,4-triazol-1-yl）isophthalic acid ligand reacted with transition metal salts such as Co（Ⅱ）,Mn（Ⅱ）,Cd（Ⅱ）,Ni（Ⅱ）and the main group metal salt such as Pb（Ⅱ）)at160℃for about 72h.By adjusting the ratio of organic solvent,changing the ratio of ligand and metal salt to adjust the p H of the system（the purpose is to control the degree of deprotonation of the ligand）and finally synthesized 5 kinds of complexes,{[Co₂（L）₂（H₂O）₄]·H₂O}_n（1）、{[Mn₂（L）₂（H₂O）₄]·H₂O}_n（2）、{[Cd₂（L）₂（H₂O）₄]·H₂O}_n（3）、[Ni（L）（H₂O）₂]_n（4）、{[Pb₂（L）₂（H₂O）₂]·H₂O}_n（5）,in complexes 1-5 throughπ...πstacking or intermolecular hydrogen bonding to make it present a 3D structure.The solid-state fluorescence analysis of complexes 3 and 5 was done.Complex 5 found bright yellow light under ultraviolet light.Then,complex 5 was used to identify solutions containing common inorganic anions and cations and some organic small molecule solutions.Through fluorescence spectroscopy shows that complex 5 has a strong quenching effect when docked with Fe³⁺,Cr₂O₇^2-,aniline,and nitrobenzene solutions.By contrast,has a larger quenching constant of 1.6x10⁴M^-1and a lower detection limit 1.75x10^-7M for NB.The complex is found5 it is more sensitive to the fluorescence detection of NB,and the quenching mechanism can be attributed to energy competition absorption.2.Secondly,5-（1,2,4-triazol-1-yl）isophthalic acid reacted with rare earth metal salts such as Eu（Ⅲ）,Gd（Ⅲ）,Dy（Ⅲ）,Nd（Ⅲ）at 160℃for about 72h,by controlling the ratio of ligand and metal salt,the ratio of organic solvent and the dosage of 0.01 mol/L oxalic acid solution（controlling the degree of decarboxylation of ligand）,finally synthesized 4 kinds of compounds,[Eu₄（L）₄（C₂O₄）（H₂O）₄（OH）₂]_n（6）、[Gd₄（L）₄（C₂O₄）（H₂O）₄（OH）₂]_n（7）、{[Dy₂（L）（H₂O）₂（C₂O₄）_0.5（OH）（H₂O）₂]（CH₃CH₂OH）}_n（8）、[Nd（L）（C₂O₄）_0.5（H₂O）]_n（9）,the structures of these complexes all show a three-dimensional network structure,in which oxalic acid also participates in the coordination,which increases the diversity of the complex structure.Among them,the complexes 6-8 do not form a coordination with the N of the triazole group.Complex 9 coordinated with both N and O.Subsequent studies on the solid-state fluorescence performance of complexes 6,7 and 8.The complex 6 emits dazzling red light under ultraviolet light and has relatively good fluorescence performance.The inorganic anion,cation and organic small molecule solutions are treated by complex 6.Sensing studies have found that Fe³⁺,aniline and nitrobenzene have a strong fluorescence quenching effect on compound 6.Through fluorescence titration experiments on the ethanol emulsion of complex 6,we found that complex 6 has a large quenching constant and a low detection limit of 1.06 x10⁴M^-1,4.67x10^-6M for NB,respectively.Indicates that complex 6 has a good fluorescence response to NB and the quenching mechanism can be attributed to energy competition absorption.