Syntheses And Characterizations Of Organic Modification Vanadates

Vanadates are a new type of materials with unique structure and excellent properties,such as photocatalysis,magnetism,nonlinear optics,electrochemistry and the others,so that researchers have an interest in their syntheses,structures and properties.In order to explore the potential application of new kind of vanadate materials,fourteen new vanadates have been synthesized and structurally characterized by single crystal X-ray diffraction,powder X-ray diffraction,IR and UV-vis.The photocatalytic,magnetic and thermal stability of some of these compounds were investigated.1.Trihydroxymethylaminomethane modification vanadates:ten vanadium clusters modified by trihydroxymethylaminomethane?-[V₂O₂(acac)(CH₃C H₂O)(THAM)]₂(1)??-[V₂O₂(a ca c)(C H₃C H₂O)(TH A M)]₂(2)?[V₂O₂(ac ac)(C H₃O)(TH AM]₂(3)?[V₂O₂(acac)(O C H₂C H₂O H)(TH AM)]₂(4)?[V₂O₂(acac)(C₇H₇O)(TH AM)]₂(5)?[V₂O₃(acac)(THAM)]₂(6)?{V₂O₃(H₃C CON HC(C H₂O H)₃)(C H₃CO O)}₂(7)?[V₆O₁₀-(THAM)₃]·6H₂O(8)?{V₇(?-O)O₈(THAM)₄(C H₃COO)}₂(9)?{V₇(?-O)O₈(THAM)₄-(HCOO)}₂(10)were successfully synthesized by solvothermal methods.Compounds 1 and3-5 all contain[VO]²⁺,[VO(acac)]²⁺and THAM bridging ligands,which are interconnected to form tetranuclear vanadium cluster[V₄O₄(acac)₂(THAM)₂].Such cluster is further modified by different organic oxygen-containing ligands CH₃CH₂O,CH₃O,OCH₂CH₂OH and C₇H₇O,respectively.The cluster frameworks of 1-2 are the same,but the modes of stacking are different,resulting in different crystal structures.7 exhibits a tetranuclear vanadium cluster based on the combination of dimeric[V₂O₃],CH₃COO and H₃CCONHC(CH₂OH)₃ bridging ligands,where a new ligand H₃CCONHC(CH₂OH)₃ results from THAM and acetic acid undergoing an amidation reaction.Compound 8 shows a hexanuclear vanadium clusters modified by THAM.Compounds 9 and 10 display a rare fourteen-nuclear vanadium cluster{V₇(?-O)O₈(THAM)₄(L)}₂(L=CH₃COO,HCOO)based on two seven-nuclear vanadium clusters[V₇(?-O)O₈(THAM)₄(HCOO)]through the sharing edge.2.Formic acid modification vanadates:two formic acid modification vanadates(III)[V^III(OH)(?-HCOO)₂]_n(11)and[V^{I V}O(?-HCOO)₂]_n·n H₂O were successfully obtained by solvothermal methods.In compound 11,the vanadium ion adopts a six-coordination mode,and is bridged by both formic acid and OH^-to give a 1-D chain structure[V^III(OH)(?-HCOO)₂]_n.In compound 12,V⁴⁺adopts a five-coordination mode and is bridged by formic acid to form a 2-D layered structure.The thermal stability of compounds 11 and 12was studied.3.Borovanadates:Two 3-D borovanadates[K₄(H₂O)₅Zn₂V₅B₁₅O₃₈(OH)₅]·7H₂O(13)and K₆[Ni(H₂O)₄V₁₂B₁₈O₅₄(OH)₆]·2H₃O·17H₂O(14)were obtained under hydrothermal conditions.Compound 13 is composed of[Zn₄V₁₀B₃₀O₇₄(OH)₈]^8-cluster and 8 K-O bonds to form a three-dimensional network structure with 1-D tunnels filled with free H₂O molecules.Compound 14 is composed of[N i(H₂O)₄]²⁺and[V₁₂B₁₈O₅₄(OH)₆]^10-anion clusters to form a one-dimensional chain structure,which is connected by K-O bond to form a three-dimensional network structure with 1-D tunnels filled with protonated water H₃O⁺and free H₂O molecules.The introduction of transition metal into borovanadate structure leads usually to low-dimensional structure,while compound 14 is a rare three-dimensional structure.Compound 14 shows good photocatalytic activity.