Two Ni-Substituted Trilacunary Keggin-Type Polyoxometalates: Syntheses, Crystal Structures, Nlo Studies, And Magnetic Properties

Two Ni- substituted polyoxometalates (NiSPs), [Ni-6(Py)(6)(H2O)(5)(mu(3)-OH)(3)(PW9O34)](2)center dot 10H(2)O (1), [Ni-7(Py)(6)(Im)(H2O)(5)O(WO4)(()mu(3)-OH)3(H2PW9O34)]center dot 3H(2)O (2) (Py = pyridine, Im = imidazole), were successfully hydrothermally synthesized. Compounds 1 and 2 have significantly different configurations by introducing different amounts of imidazole ligands. For compound 1, two malposed {Ni-6(Py)(6)PW9} units that are face to face are bridged by two Ni-O-W bonds to constitute an isolated dimeric structure. Differently, the {Ni-7(Py)(6)(Im)PW9}(2) dimer in compound 2 connects with four adjacent dimers by four {WO4} groups in an interesting two-dimensional (2-D) arrangement. The magnetism of compounds 1 and 2 was studied, and magnetic test results demonstrated that both compounds have ferromagnetic interactions between the nickel centers. Meanwhile, the third-order nonlinear optical (NLO) measurements indicated that compound 1 can serve as potential nonlinear optical materials.