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, [Cu3(μ2-OH)(pdon)3(pca)(H2O)3][SiW12O40]·6H2O (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 [SiW12O40]4− (SiW12) cluster connects with three trinuclear [Cu3(μ2-OH)(pdon)3(pca)(H2O)3]4+ metal-organic fragments, meanwhile, each metal-organic fragment also links with three SiW12 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 SiW12 polyoxoanions, leading to the formation of a 2D layer network. Moreover, the photochemical catalysis and electrochemical properties of complex 1 are also reported.