Two Keggin compounds constructed from tri−/tetra-nuclear Cu clusters linked mono copper(II)-substituted phosphomolybdates

Temperature-controlled formation of Anderson-type compounds and their conversion to [γ-Mo8O26]4−-based variants using pendent ligands

By tuning the reaction temperature, two Anderson- and two [γ-Mo8O26]4−-based compounds decorated by pendent organic ligands, [CuII 9(bpz)2(pz)2(H2O)24][H2(Cr(OH)5Mo6O19)4]·11H2O (1), [CuII(bpz)2(H2O)2(γ-H4Mo8O26)]·2H2O (2), [CuII 2(tea)2(H2O)6(HCr(OH)6Mo6O18)2]· 6H2O (3) and [AgI(bpz)(H2O)(γ-H4Mo8O26)0.5] (4) (bpz=4-butyl-1H-pyrazole, pz=1H-pyrazole, tea=2-[1,2,4]triazol-4-yl-ethylamine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, IR spectra and elemental analyses. In compound 1, there are two kinds of tri-nuclear CuII clusters induced by bpz and pz ligands, respectively. Four Anderson-type anions are linked by these tri-nuclear clusters to form a “W”-type subunit. In compound 2, the [Cu(bpz)2(H2O)2]2+ subunits connect the γ-Mo8 anions to construct a chain. The remaining two non-coordinated N donors in [Cu(bpz)2(H2O)2]2+ further link two adjacent γ-Mo8 anions through Mo–N bonds. In compound 3, there exists a bi-nuclear CuII cluster [Cu2(tea)2(H2O)6]4+. The discrete bi-nuclear CuII clusters and the CrMo6 anions link each other through abundant hydrogen bonding interactions. In compound 4, the [Ag(bpz)(H2O)]+ subunits connect γ-Mo8 anions to build a zigzag chain. The chains are further fused by other [Ag(bpz)(H2O)]+ cations to form a grid-like layer. There still exist Mo–N bonds in 4. We also have investigated the electrochemical and photocatalytic properties of 1–4.

Two new POM-based compounds containing a linear tri-nuclear copper(II) cluster and an infinite copper(II) chain, respectively

Using the pendent organic ligand 1-butyl-1H-(1,3,4)triazole (btz), two new polyoxometalate (POM)-based compounds, [Cu3(btz)6(H2O)4(H3P2W18O62)2]·6H2O (1) and [Cu2(btz)(tz)(H2O)2(SiMo12O40)]·5H2O (2) (tz=1H-(1,3,4)triazole), have been synthesized under hydrothermal conditions. In compound 1, three CuII ions are fused by six btz ligands to form a linear tri-nuclear CuII cluster, with water as bridging molecules. Two Wells-Dawson anions offer two terminal O atoms to link two apical CuII atoms of this tri-nuclear cluster. In compound 2, the btz and tz molecules connect CuII ions to construct an infinite CuII chain still with water molecules as bridges. The adjacent chains are linked by one type of POM anions to build a 2D grid-like layer. Considering the long-range coordinative Cu–O bonds, the other types of POM anions connect adjacent layers to form a 3D framework. The electrochemical and photocatalytic properties of compounds 1 and 2 were also studied.