Polyoxometalate-directed assembly and various structures of inorganic-organic hybrid compounds based on a semi-rigid bis-pyridyl-bis-amide

摘要

Through tuning different kinds of polyoxometalates (POMs), four POM-based inorganicorganic hybrid compounds with different dimensionalities, namely [(H2L)(2)(Mo8O26)] (1), [(Cu2L6)-L-II(P2W24O79)center dot 4H(2)O]center dot 7H(2)O (2), {(Cu2L2)-L-II(mu(2)-OH)[CrMo6(OH)(6)O-18]center dot 4H(2)O}center dot 4H(2)O (3), and {(Cu2Cu2L2)-Cu-I-L-II(mu(3)-OH)(2)[CrMo6(OH)(5)O-19]center dot 6H(2)O}center dot 4H(2)O (4) [L = 1,4-bis(3-pyridinecarboxamido)benzene], have been synthesized under hydrothermal conditions and characterized by IR spectroscopy, TG analysis, powder XRD and single-crystal X-ray diffraction. Single-crystal X-ray analyses reveal that compound 1 exhibits a two-dimensional (2D) supramolecular network, which is constructed from protonated L ligands and [Mo8O26](4-) anions through hydrogen bonding interactions. Compound 2 is a 1D hybrid chain based on an uncommon inorganic [P2W24O79](4-) chain and Y-shaped (CuL3)(2+) subunits. Compound 3 shows a 2D network constructed from 1D inorganic Cu-2-CrMo6 chains and bidentate L ligands, which is obtained at pH = 4.1. When the pH was adjusted to 4.8, compound 4 is obtained which exhibits a 4-connected {6(6)} 3D framework. The CrMo6 anions are connected by adjacent [(Cu2Cu2II)-Cu-I(mu(3)-OH)(2)(H2O)(6)](4+) subunits to form 1D Cu-4-CrMo6 inorganic chains, which are further extended by L ligands to construct a 3D network. The effect of different types of polyanions and pH values on the assembly and various structures of the title compounds has been discussed. Furthermore, the electrochemical properties of 1 and 2, and the photocatalytic properties of 2 and 3 under different conditions have been investigated.