Reaction Controlled Assemblies of Polyoxotungstates (-molybdates) and Coordination Polymers

To investigate the influence of reaction conditions on the compound structures, five polyoxometalate (POM)-supported inorganic-organic hybrid compounds, [Cu-3(I)(L-1)(4)][PW12O40] (1), [Cu-3(I)(L-1)(4)][PMo12O40] (2), [Cu-3(I)(L-1)(4)][PW12O40] (3), [Cu-3(I)(L-1)(3)][PW12O40] (4), and [Cu-3(I)(L-2)(3)][PMo12O40] (5) [L-1 = 1,4-bis(pyrazol-1-ylmethyl)benzene, L-2 = 4,4'-bis(pyrazol-1-ylmethyl)biphenyl], were hydrothermally synthesized by tuning the reactant species and molar ratio and reaction temperature and were characterized by elemental analysis, IR spectroscopy, PXRD, XPS, electrochemistry, SPS, and X-ray crystallography. Compounds 1 and 2 were synthesized in the isostructural state at 150 degrees C, in which L-1 ligands link Cu-1 ions, generating a cationic 2D 6(3) (hcb) skeleton {[Cu-3(L-1)(4)](3+)}n-like sheet that further connects with POM anions, forming a neutral 2D (3,4)-connected network with a Schlafli symbol of (5(3))(2)(5(4);8(2)). In contrast, compound 3 was synthesized at a relatively lower reaction temperature (130 degrees C) than that for the synthesis of 1 and 2, which exhibits a similar 2D sheet-like cationic skeleton with 1 and 2. Interestingly, the POM anions do not coordinate with the cationic moieties in 3. Compounds 4 and 5 were synthesized with a relatively lower reactant molar ratio in comparison with that for the synthesis of 1-3, in which the cationic coordination moieties all present 1D chain-like structures. Compound 4 exhibits a 3D (3,4)-connected sqc74 framework with a Schlafli symbol of (6;8(2))(6(4);8:10) formed by the POM anions linking {[Cu-3(L-1)(3)](3+)}(n) cationic chains. In comparison to 4, compound 5 shows a 3D supramolecular framework, which is formed by POM anions and {[Cu-3(L-2)(3)](3+)}(n) cationic chains via hydrogen bonds. The structural difference of compounds 1-5 indicates that the reaction conditions perform a crucial influence on the structures of this series. The electrochemical properties of 2 and 5 and the S PS responses of 3-5 suggest that these compounds can be used as potential electrocatalytic or photocatalytic framework materials. In addition, EFISPS curves indicate that 3-5 possess the n-type semiconductor characteristic.