Preparation And Properties Of Transition Metal Complexes Based On Carboxylic Acid Ligands With Sulfur-Containing Heterocycle

The reaction between thioheterocyclic carboxylic acid ligands and metal ions can yield novel multifunctional materials with magnetic,luminescent,adsorption,and catalytic properties.In this paper,three new transition metal complexes were synthesized by using two different types of sulfur-containing heterocyclic carboxylic acid ligands,their structures were characterized and analyzed,and some complexes were characterized by magnetic,catalytic,proton conduction and fluorescence sensing properties.The main findings are as follows:（1）Two molecular complexes（1 and 2）were prepared with benzotetrathiafulvalene tetracarboxylic acid（H₄DBTTF）as the main ligand and Zn²⁺and Co²⁺ions.Due to the different coordination modes of the carboxylic acids on the ligands,2 is a structure with a symmetrical binuclear configuration,while 1 is a mononuclear complex.In the study of the properties of 1and 2,it was found that 1 has a good selective adsorption effect on linear cationic dyes.Due to the effect of tetrathiafulvalene（TTF）group and variable valence metal Co²⁺ions,2 has a certain catalytic degradation effect on methylene blue（MB）dye under the irradiation of xenon lamp.In addition,the experiment of 2 and monopersulfate（PMS）combined to degrade dyes found that 2 can catalyze the rapid decomposition of PMS to generate O₂^·-and SO₄^·-radicals,which improved the degradation rate of PMS to rhodamine B（Rh B）dyes.（2）A metal organic framework（Zn-MOF,3）was synthesized from 4,4’,4’’,4’’’-（thieno[3,2-b]thiophene-2,3,5,6-tetraaryl）tetrabenzoic acid（H₄TPTB）and Zn²⁺ions.Due to the unique coordination structure of 3,it has good proton conductivity,and the proton conductivity reaches6.7×10^-4 S cm^-1（at 80°C and 98%relative humidity）.The activation energy is 0.99 e V.Fluorescence property test experiments found that the fluorescence intensity of 3 would be enhanced during fumigation with hydrochloric acid（HCl）steam,accompanied by a slight red-shift behavior.And the comparison of photoelectron diffraction patterns and infrared spectra of3 before and after fumigation found that it may be the carboxylic acid in 3 caused by the interaction of the group with HCl.In addition,3 exhibits photoluminescence quenching behavior under mercury lamp irradiation,and has good fluorescence quenching sensing behavior for Al³⁺,Ga³⁺and Cr³⁺ions in ethanol system.In-depth studies have shown that 3loaded with Rh B dye exhibits a single-peak enhanced sensing phenomenon for Al³⁺and Ga³⁺ions in cation sensing experiments for cations,accompanied by obvious fluorescence color changes.which is significantly different from the sensing phenomenon of 3 in ethanol or water systems.