Polyoxometalate charge directed coordination assemblies: Macrocycles and polymer chains

Abstract

To investigate the charge influence of polyoxometalates (POMs) on the compound structures, six POM-containing transition metal complexes (TMCs), [CuI2L2][Mo6O19] (1), [CuI3L3]2[PMo12O40]2 (2), [CuI4L4][SiMo12O40] (3), [CuI4L4][SiW12O40] (4), [CuI4L4][GeMo12O40] (5), [CuI5L5][BW12O40]·H2O (6), [L = 1,4-bis(pyrazol-1-ylmethyl)benzene], were hydrothermally synthesized by using polyoxoanions with different charges as the building blocks and characterized by elemental analysis, IR spectra, PXRD, XPS, electrochemistry, surface photovoltaic spectra (SPS) and X-ray crystallography. Compound 1 consists of Lindqvist type [Mo6O19]2− anions with two negative charges linking zigzag-type {[CuI2L2]2+}n cationic chains to construct a 2D neutral 63 wall-like network. In compound 2 the [PMo12O40]3− anions with three negative charges act as the template directing L ligands to link with CuI ions forming an interesting triangular [CuI3L3]3+ macrocyclic type TMC. Compounds 3–5 are crystallographically isomorphous, and they contain Keggin type POMs anions of [SiMo12O40]4−, [SiW12O40]4−, and [GeMo12O40]4− with four negative charges as the template that induce the square [CuI4L4]4+ cationic macrocyclic structures of the TMC moieties. Compound 6 is composed of [BW12O40]5− anions with five negative charges linking 1D zigzag-type {[CuI5L5]5+}n cationic chains to build up a novel 2D neutral network. The structural differences of compounds 1–6 indicate that POM anions serve as the structure-directing components performing a crucial influence on the assembly progress of TMCs in 1–6. In addition, the electrochemical properties of 1–6, and the SPS responses of 1, 5, 6 were studied, suggesting that these compounds could be used as potential electrocatalytic or photocatalytic materials.