Assembly of two novel coordination polymers constructed from metal-organic framework and Keggin-template

Two new Keggin polyoxometalate (POM)-based compounds combined copper metal complexes have been synthesized under hydrothermal conditions: {[Cu-I(biPY)(2 center dot)(H2O)(2)](4)}center dot[SiW12O40](2)}center dot{(H(2)bipy)(2)}center dot(bipy)(2))center dot 8H(2)O (1) (bipy=4,4'-bipyridine) and (Cu-I(bipy)(2)center dot (H2O)(2)}center dot{Cu-I(bipy)(2)}[H2SiW12O40]center dot 20H(2)O (2), and structurally characterized by elemental analysis, IR spectra, EPR, TGA and single crystal X-ray diffraction. Two compounds are all based on [SiW12O40](4-) Keggin building block and synthesized under the same reaction condition, only different pH values. The copper complex cations of compound 1 and 2 construct covalently 2D square grid structure, furthermore, the 2D square grids are held together into a three-dimensional supramolecular network through hydrogen-bonding interactions, whereas Keggin anions are sited in 3D square grid channels alternately. The results show that the pH value of the reaction system plays a crucial role in structural control of self-assembled processes. (c) 2006 Elsevier B.V. All rights reserved.