title: Giant polyniobate clusters based on [Nb7O22]9- units derived from a Nb6O19 precursor.
abstract: Rational self-assembly of hexaniobate Lindqvist-type precursor [HNb6O19]7- with soluble Cu2+ salts utilizing different strategies produces a series of giant polyniobate clusters, namely, (H2en)1.25[Cu(en)2(H2O)]2Cl4[Nb24O72H21.5]7 H2O (1; en: ethylenediamine), [Cu(en)2]3[Cu(en)2(H2O)]9[{H2Nb6O19} subset{[({KNb24O72H10.25}{Cu(en)2})2{Cu3(en)3(H2O)3}{Na1.5Cu1.5(H2O)8}{Cu(en)2}4]6}]144 H2O (2), K12Na4[H23NaO8Cu24(Nb7O22)8]106 H2O (3), and K16Na12[H9Cu25.5O8(Nb7O22)8] 73.5 H2O (4). Their structures were determined and further characterized by single-crystal X-ray diffraction analysis, IR and Raman spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Structural analyses reveal that compound 2 comprises a giant capsule anion based on a wheel-shaped cluster encapsulating a Lindqvist diprotonated cluster [H2Nb6O19]6- unit, and forms a honeycomb-like structure with the inclusion of Lindqvist-type anions [H2Nb6O19]6- in the holes, whereas 3 and 4 represent an unprecedented giant cube-shaped framework. All the compounds are built from [Nb7O22]9- fundamental building blocks. Solution Raman spectroscopy studies of 2 and 3 reveal that the solid-state structures of these polyniobate cluster anions disassemble and exist in the form of the [Nb6O19]8- unit in solution. Magnetic susceptibility measurement of 3 shows antiferromagnetic coupling interactions between CuII ions with the spin-canting phenomenon.
authors.affiliation: Institute of Molecular and Crystal Engineering, School of Chemistry and Chemical Engineering, Henan University, Minglun Street 85, Kaifeng 475001, China.
authors.forename: Jingyang
authors.initials: J
authors.lastname: Niu
authors.forename: Pengtao
authors.initials: P
authors.lastname: Ma
authors.forename: Hongyu
authors.initials: H
authors.lastname: Niu
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Junwei
authors.initials: J
authors.lastname: Zhao
authors.forename: You
authors.initials: Y
authors.lastname: Song
authors.forename: Jingping
authors.initials: J
authors.lastname: Wang