Syntheses And Structural Characterizations Of Vanadium And Vanadium-Molybdenum (Tungsten) Polyoxometalate

Polyoxometalates (POMs) represent a fascinating class of inorganic chemistry with a structural variety and interesting properties, which are of use in fields as diverse as catalysis, sorption, molecular electronics, medicine, etc. the synthesis of the previously reported polyoxometalates are mainly related to the preparations of simple, discrete metal-oxygen clusters. Recently, studying on the POMs which link into supramolecular structure via hydrogen bonding interactions has become a hotspot gradually.During our research for metal-oxygen clusters, we synthesized some supramolecular structure compounds based on vanadium clusters and tungsten-vanadium clusters. Some compounds have been characterized by IR, XPS, ESR spectra and X-ray structural analyses. The thermal analyses properties of some compounds have also been studied, which would take a role in explorations of structures and functions for the compounds.1. Vanadium clustersThe hydrothermal reactions give three vanadium clusters, (H₂dien)₄[H₁₀V₁₈O₄₂(PO₄)](PO4)·2H₂O 1(dien = diethylenetriamine), (Him)₈[HV₁₈O₄₂(PO₄)] 2 and [Fe(2,2'-bipy)₃]₂[Fe(2,2'-bipy)₂(im)₂][V₁₅O₃₆(Cl)] 3 (im = imidazole). Their structure were determined by single crystal X-raydiffraction analyses and characterized by XPS, EPR, IR, ICP, and TG. Both compound 1 and 2 are novel supramolecular structure complexes based on [V₁₈O₄₂(PO₄)] cluster via hydrogen bonding interactions. There are protonate diens and protonated ims as charge balance cations in compound 1 and 2 respectively. And more interestingly, there is a {PO₄}^3- as charge balance anion outside of the shell in compound 2. Compound 3 is a discrete V₁₅O₃₆ cluster. In the charge balance cations, Fe2+ are coordinated by one im and two 2, 2'-bipy. 2. Molybdenum-vanadium cluster The hydrothermal reaction gives one molybdenum-vanadium cluster, (H4, 4'-bipy)₃[PMo₈V₆O₄₂]·4H₃O·2H₂O 4. Its structure was determined by single crystal X-ray diffraction analysis and characterized by XPS, EPR, IR, ICP, and TG. Compound 4 contains cluster anions with bicapped-Keggin structure. 3. Tungsten-vanadium cluster The hydrothermal reaction gives one tungsten-vanadium cluster, [im]2[Fe(2,2'bipy)₃]₂[W₁₂V₆O₄₂(PO₄)]·[(OH)]·4H₂O 5. Its structure was determined by single crystal X-ray diffraction analysis and characterized by XPS, EPR, IR, ICP, and TG. Compound 5 contains cluster anions with six-capped Keggin structure, the cluster anions link into one novel three-dimensional supramolecular structure via hydrogen bonds.