Three novel polyoxoanion-supported compounds: confinement of polyoxoanions in Ni-containing rigid concave surfaces with enhanced NLO properties.

Three novel polyoxoanion-supported compounds modified by conjugated organic ligand tris(2-benzimidazylmethyl)amine (NTB) and nickel ions, [Ni(NTB)(H2O)]2(H2P2Mo5O23)·9.25H2O (1), [Ni(H2O)(NTB)]2(PMoMo(V)O40)·4.5H2O (2) and [Ni(NTB)]2(Mo8O26)·9H2O (3), have been successfully synthesized under hydrothermal conditions at different pH values. The compounds 1-3 contain similar rigid concave surfaces composed of [Ni(NTB)](2+) cations, which connect with different clusters to form the first examples of metal-NTB-modified polyoxoanion-supported compounds. Transition metal-containing rigid concave surfaces successfully confine polyoxoanions in compounds 1-3. In the synthesis of the three compounds, the pH values play an important role in the formation of polyoxoanions and the stability of the compounds. Additionally, the third-order nonlinear optical properties (NLO) and electrochemical behaviors were also investigated.