Zero- or One-Dimensional Organic−Inorganic Hybrid Polyoxoniobates Constructed from Decaniobate Units and Transition-Metal Complexes

A series of novel organic−inorganic hybrids containing [Nb10O28]6− building blocks [Ni(2,2′-bipy)2]3 [Nb10O28]·2H2O (1), [Ni(2,2′-bipy)3]{[Ni(2,2′-bipy)2]2[Nb10O28]}·8.5H2O (2), [M(phen)3]{[M(phen)2]2[Nb10O28]}·8H2O (M = NiII for 3; M = ZnII for 4; M = CoII for 5) (2,2′-bipy = 2,2′-bipydine, phen = 1,10-phenanthroline) have been successfully synthesized using the hydrothermal method by introducing different transition-metal complexes and fully characterized by elemental analyses, X-ray powder diffraction (XRPD), IR spectroscopy, UV spectroscopy, single-crystal X-ray diffraction analyses, and thermogravimetric analyses. 1 is a one-dimensional (1D) infinite chain polyoxoniobate built by [Nb10O28]6− units and [Ni(2,2′-bipy)2]3 6+ cations. Furthermore, adjacent chains in 1 are further interacted by π−π stacking interactions resulting in a three-dimensional (3D) supramolecular network. 2−5 are constructed from [Nb10O28]6− units and different transition-metal complexes, in which neighboring units are combined together via the π−π interactions between pyridine rings of ligands forming a 1D linear supramolecular chain. Moreover, the photoluminescence properties of 1 and 3−5 have been investigated. Electron paramagnetic resonance (EPR) spectra reveal that high-spin CoII ions in 5 inhibit the octahedral environments.