Synthesis,crystal Structure And Characterization Of Transition-metal Complexes Based On Polyoxovanadates

In this paper, combining with molecular design and self-assembly, six new complexes were prepared by means of hydrothermal techniques on the basis of ligands (bpp = 1,3'-di-pyridylpropane, dpa = 2,2′-dipyridylamine) and polyoxovanadates. All these complexes have been structurally characterized by ICP, IR, TG-DGA, XPRD and X-ray single crystal diffractions. The study on synthetic conditions and electrochemical property for some of them are also carried out.1. Two new 3D complexes constructed from {VO₃}_n^n- chains and woven {M(bpp)(H₂O)₂}_n chains, [M(bpp)(H₂O)₂V₂O₆]·0.4H₂O (M = Ni²⁺ (1)å’ŒCo²⁺ (2) ) were synthesized. They are isomorphous, {M(bpp)(H₂O)₂}_n^2n- chains are projected up along the a and b axises, woven into a three-dimensional crisscross structure. The {VO₃}_n^n- chains connected with M(II) are located in the {M(bpp)(H₂O)₂}_n^2n- channels.2. By optimizing reaction conditions, complex [Cu(dpa)V₃O_8.5] (3) exhibit an interesting 2D structure based on {V₃O_8.5}^2- layers inlaid with {Cu(dpa)}²⁺ subunits. The {V₃O_8.5}^2- layers consist of ladder-like chains of edge sharing {VO₅} square pyramids bridged through {V₂O₇} subunits, which is a novel layered structure of polyoxovanadates as well as a new connecting mode with metal-ligand subunits.3. Two new complexes based on cyclic polyoxovanadates, [{(Cu(dpa)₂)₂(OX)}₂V₄O₁₂]·H₂O (4) and [Zn₂(dpa)₃V₄O₁₂] (5) were isolated. Complex 4 was a discrete octanuclear heterometallic cluster composed of a cyclic {V₄O₁₂}^4- anions covalently attached to two [(Cu(dpa))₂(OX)]²⁺ fragments. Complex 5 exhibits 1D ribbon-like structure constructed from cyclic {V₈O₂₄}^8- subunits bridged through {Zn(dpa)}²⁺ and {Zn(dpa)₂}²⁺ fragments. The {V₄O₁₂}^4- and {V₈O₂₄}^8- ring have a cyclic eight/sixteen-numbered {V₄O₄} core formed by corner sharing of four/eight distorted {VO₄} tetrahedra, respectively. Both the cyclic polyoxovanadates exhibit a chair-like configuration.4. Complex [Ni(dpa)₂V₂O₆] (6) consists of {VO₃}_n^n- chains bridged through {Ni(dpa)₂}²⁺ fragments into 1D chains. The 1D chains are connected into a 2D network via the hydrogen-bonding interaction.5. Electrochemical measurement shows that lithium ions are reversibly intercalated and deintercalated in 1,2 and 3, which may be a potential active cathode material in reversible lithium ion batteries.