Preparation?Characterization And Properties Of Organofunctionalized Multi-vanadium Molybdenum Oxide Clusters

Multi-vanadium molybdenum oxide clusters are important members of polyacid scientific research,and have important application value in many research fields,such as optoelectronics,biology and medicine.In recent years,due to the more variable structural characteristics and excellent performance of multi-vanadium molybdenum oxide clusters,researchers at home and abroad have received extensive attention.Based on the concept of coordination chemistry and the principle of self-assembly of crystalline materials,introducing organic components with specific structures and functions,or rich and diverse metal-organic coordination units with outstanding performance,,to prepare organofunctional molecular-based clusters that have the advantages of multi-vanadium molybdenum oxide clusters and organic units in a mixed coordination configuration,is one of the most challenging and attractive research topics.In this paper,ammonium metavanadate(NH₄VO₃),vanadyl acetylacetonate(VO(acac)₂),phosphomolybdic acid(H₃PO₄·12Mo O₃),etc.are mainly used as the precursors of polyvanadium molybdenum oxide clusters,and organic phosphonic acid with biological activity as bridging ligand,using multifunctional N-imidazole as the reaction medium,self-assembled into a new organic functionalized poly-vanadium molybdenum oxide cluster under solvothermal conditions.Through single crystal X-ray powder diffraction,elemental analysis,Thermogravimetric,infrared,ultraviolet,fluorescence and other means to characterize the structure of the compounds,and studying the influence of the precursors of different multi-vanadium molybdenum oxide clusters on the structure of the compounds and the role of auxiliary ligands in the cluster compounds,and to explore the control synthesis method of multi-vanadium molybdenum oxide clusters,the catalytic performance of some compounds as catalysts on characteristic organic reactions was discussed.The specific work is as follows:1.Introduce risedronic acid(H₅L)into ammonium metavanadate and vanadyl acetylacetonate.Neutral organic ligands(N-methylimidazole and N-ethylimidazole)are used as the reaction medium,under solvothermal conditions,two tetranuclear vanadium clusters with similar structures were obtained.Compound 1 is a sheet-like cluster compound formed by four metal vanadium ions bridged by two risedronic acid,eight N-methylimidazoles are embedded in the framework as auxiliary ligands.Compound 2 is similar in structure to compound 1,but the auxiliary ligands are different.N-methylimidazole is replaced with N-ethylimidazole.This is of great significance for the controlled synthesis of polynuclear vanadium clusters.The controlled synthesis of the compound 1 is of great significance.The compound 1 is used as a catalyst to study its catalytic oxidation performance for alcohols(p-methoxybenzyl alcohol),which shows a good catalytic performance.2.Introduce risedronic acid(H₅L)into ammonium metavanadate,adjust different solvents,respectively in the acetic acid/sodium acetate(CH₃COOH/CH₃COONa)buffer solution at p H=4.6 and hydrochloric acid solution,using conventional reflux-filtration-standing,two multi-vanadium oxide cluster compounds are obtained:compound 3 and compound 5.Compound 3 is a pinwheel-like shape composed of six metal vanadium ions and two metal sodium ions through six bridging ligand risedronic acid Cluster compound,compound 5 is a centrosymmetric cluster which is composed of 5 metallic vanadium and two risedronic acid,and its structure is characterized.Compound 4 is a mononuclear compound unexpectedly obtained when changing ammonium metavanadate to vanadyl sulfate,indicating that the type of polyvanadyl cluster precursor has an important influence on the products?3.Using ammonium metavanadate,phosphomolybdic acid and PMo₁₀V₂ as the vanadium source and molybdenum source of polyvanadyl molybdate,introduce neutral organic ligands N-methylimidazole and butylimidazole,respectively,under solvothermal conditions,two clusters with different structures were obtained by adjusting the reaction temperature:compound 6 and compound 7,both of which contain polyacid spheres.The polyacid sphere of compound 6 has three metal vanadium ions to balance the polyacid anion.the twelve auxiliary ligands,N-methylimidazole,are like three claws protruding from the polyacid ball,forming an isolated cluster of three-supported structure.Compound 7 is a cluster compound formed by V-O-V bridges between polyacid spheres and eight auxiliary ligands,butyl imidazole,comparing the synthesis methods,it is found that temperature and auxiliary ligands are very important for the synthesis of specific compounds,which will change the synergy between ions and affect the coordination and stacking methods of compounds.