Construction of Mono-, Bi- and Trinuclear Clusters to Modify Wells–Dawson Anions through Using Different Transition Metals and Flexible Bis(Pyrazole) Ligands

Three new Wells–Dawson compounds, namely [CoII(edpz)(H2bdpm)3][(H4P2W18O62)] (1), [CdII2(mpz)(H2bhpe)2.5(H2O)(H2P2W18O62)] · (ppz) · 6H2O (2) and [CuII3(ppz)(H2bhpe)2(P2W18O62)(H2O)3] · 2H2O (3) (edpz = 4-ethyl-3,5-dimethyl-1H-pyrazole, H2bdpm = 1,1'-bis(3,5-dimethyl-1H-pyrazolate)methane, mpz = 4-methyl-4H-pyrazole, H2bhpe = 1,2-bis(1H-pyrazolyl)ethane, ppz = 4-propyl-1H-pyrazole), have been hydrothermally synthesized by using flexible bis(pyrazole) ligands and characterized by single-crystal X-ray diffraction analysis, IR spectra and elemental analyses. In compound 1, there are two discrete subunits: a mono-nuclear [Co(edpz)(H2bdpm)3]2+ cluster and a Wells–Dawson anion. The hydrogen bonding interactions between these subunits induce a 2D supramolecular structure. In compound 2, two Cd ions are fused by one mpz and five H2bhpe ligands to construct a bi-nuclear Cd cluster. The [P2W18O62]6– anions link bi-nuclear Cd clusters to form a 3D framework. In compound 3, four H2bhpe ligands fuse three CuII ions to construct a planar tri-nuclear cluster, with one ppz ligand vertical with this tri-nuclear cluster. The [P2W18O62]6– anions connect adjacent tri-nuclear clusters to form a 3D framework. Moreover, we also investigated the electrochemical and photocatalytic properties of compounds 1−3.