Three new polyoxoniobates constructed from Lindqvist-type hexaniobate and copper-amine complexes

Three new polyoxoniobates constructed from Lindqvist-type [Nb ₆O₁₉]^8- and copper-amine complexes, [Cu(1,2-dap)₂]{[Cu(1,2-dap)₂]₂[Nb ₆O₁₉H₂]}·10H₂O (1), [Cu(1,3-dap)₂]₂{[Cu(1,3-dap)]2[Nb₆O ₁₉]} 10H₂O (2), and [Cu(en)₂] _0.5{[Cu(en)₂]₂[Nb₆O ₁₉H₃]}·12H₂O (3) (1,2-dap = 1,2-diaminopropane, 1,3-dap = 1,3-diaminopropane, and en = ethylenediamine), have been synthesized and characterized by elemental analyses, infrared, powder X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectrum, and single-crystal X-ray diffraction. Compounds 1-3 exhibit bisupporting hexaniobate cluster structure, each with a [Nb₆O₁₉] ^8- cluster decorated by two copper-amine complexes. In 1, adjacent bisupporting clusters are connected with one [Cu(1,2-dap)₂] ²⁺ fragment via Cu⋯O weak interactions to generate a 1-D supramolecular chain structure. In contrast to 1, each bisupporting cluster in 2 is linked to another four neighboring ones through four [Cu(1,3-dap) ₂]²⁺ fragments by Cu⋯O weak interactions to yield a 2-D supramolecular network. Different from 1 and 2, no detected interaction was found between bisupporting cluster and [Cu(en)₂]²⁺ in 3, the [Cu(en)₂]²⁺ fragment merely acts as an isolated countercation.