Two new hexa-Ni-substituted polyoxometalates in the form of an isolated cluster and 1-D chain: syntheses, structures, and properties

Abstract

Two new hexa-Ni-substituted polyoxometalates (POMs), [Ni₆(μ₃-OH)₃(en)₂(dien)(H₂O)₅(B-α-PW₉O₃₄)]·3H₂O (1, en = ethylenediamine, dien = diethylenetriamine) and [Ni₆(μ₃-OH)₃(dap)₂(py)₆(H₂O)(B-α-PW₉O₃₄)]·H₂O (2, dap = 1,3-diaminopropane, py = pyridine), were successfully isolated under hydrothermal conditions. Compounds 1 and 2 were structurally characterized via single-crystal X-ray diffraction (XRD), infrared (IR) spectrometry, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Single-crystal X-ray structure analyses indicate that the {Ni₆PW₉} cluster units were modified via different organic ligands through Ni–N bonds, giving rise to the formation of 1 and 2. Interestingly, the formation of 1 involves new in situ ligand reactions under hydrothermal conditions: the intermolecular deamination coupling reactions of en. Compound 2 is a new Z-shaped 1-D chain, which is connected by Ni–OW bonds from two adjacent [Ni₆(μ₃-OH)₃(dap)₂(py)₆(H₂O)(B-α-PW₉O₃₄)] units. In addition, their photocatalytic activities, and electrochemical and magnetic properties have been investigated.