Design, Syntheses, Structures And Bromination Catalytic Activity Of Oxovanadium Complexes With N-heterocyclic Ligands

The coordination chemistry of vanadium has attracted much attention recent years due totheir vital roles in biologic system, such as nitrogen fixation, haloperoxidation, glycogenmetabolism and so on. In particular, vanadium dependent bromoperoxidase have receivedgreat interest owing to their potential applications in biological fields for the introduction ofbromine group to aromatic compounds, many of which have anti-bacterial and anti-cancer properties.They have also fascinated inorganic chemists and biochemists with respect to their mechanistic details anddependence on vanadium for their activity. Therefore, the syntheses of vanadium functional modelcomplexes have been became hot issue.It is important to choose appropriate ligands in the process of preparing oxovanadium functionalcomplexes. In recent years several vanadium complexes of multidentate ligands containing O and N donorsites were tested for catalysis of bromide oxidation. The results indicated that a part of vanadiumcomplexes becomes too much stabilised by the donating properties of the ligand, oxidation of bromide isnot observed. However, also various complexes have been published that are not stable under the appliedreaction conditions, which shows bromination catalytic activity. In order to investigate the relation betweenbromination activity and structure, we chose a system of vanadium complexes with N heterocyclic asligands to study their catalytic activity. Heterocycles containing nitrogen atom have receivedattention because of their good coordination capability, so far, pyridine and pyrazolederivatives are much popular. So we choose2,2’bipy,1,10-phen, pyridinedicarboxylic acid,pyrazole derivatives as ligands and synthesize a series of vanadium complexes with Nheterocyclic mimicking the active center of enzymes.In this paper, we designed and synthesized10complexes, the strucures of complexes1-10are determined by X-ray single crystal diffraction. All of them are characterized byelemental analysis, IR spectra, UV-vis spectroscopy and thermal analysis, discussed theirsyntheses rule and properties. In addition, we also tested the bromination catalytic activity ofcomplexes1-8and discuss the influence between the change of reaction system and catalyticactivity.VO₂（C₅H₇O₂）（C₁2H₈N₂）（1）（VO）₂（O）₂（OCH₃）₂(C₁₀H₈N₂)（2）[VO（C₇H₃O₄N）(C₁₀H₈N₂)]·CH₂Cl₂（3） VO（C₇H₃O₄N）₂（4）[VO（SO₄）(C₁₅H₁₇N₅)（H₂O）]·H₂O （5）[VO（SO₄）(C₁₃H₁₃N₅)]·H₂O （6）VO(C₁₇H₂₆N₈)（SCN）₂（7）[（VO）₂(C₂₈H₃₄N₈)（C₂O₄）₂]·2CH₂Cl₂（8）[Co（C₃H₄N₂）₄]Cl₂（9）[Co（C₃H₄N₂I）₄Cl₂]₂·2H₂O （10）...