Self-assembly of a 2D helical coordination polymer from Keggin-type polyoxoanion and metal-organic fragment by in situ ligand transformation

A new two-dimensional (2D) polyoxometalate (POM)-based helical coordination polymer, [Cu(3)(mu(2)-OH)(Pdon)(3) (pca)(H(2)O)(3)][SiW(12)O(40)]center dot 6H(2)O (1) (pdon = 1,10-phenanthroline-5,6-dione, Hpca = pyridine-4-carboxlic acid), has been synthesized by in situ generation of pyridine-4-carboxlic acid and 1,10-phenanthroline-5,6-dione from 2-(4-pyridine)imidazo[4,5-f]1,10-phenanthroline under hydrothermal condition, and characterized by elemental analysis, IR spectra, TGA and single-crystal X-ray diffraction. In complex 1, each [SiW(12)O(40)](4-) (SiW(12)) cluster connects with three trinuclear [Cu(3)(mu(2)-OH)(Pdon)(3)(pca)(H(2)O)(3)](4+) metal-organic fragments, meanwhile, each metal-organic fragment also links with three SiW(12) polyoxoanions to form two types of one dimensional (1D) helical chains. The adjacent 1D chains with different spiral orientations are connected by the terminal oxygen atom of SiW(12) polyoxoanions, leading to the formation of a 2D layer network. Moreover, the photochemical catalysis and electrochemical properties of complex 1 are also reported. (C) 2011 Elsevier B.V. All rights reserved.