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(PMoVI11MoVO40)·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.