title: Three cobalt(II)-linked {P8W48} network assemblies: syntheses, structures, and magnetic and photocatalysis properties.
abstract: Three cobalt(II)-containing tungstophosphate compounds, Na8Li8Co5[Co5.5(H2O)19P8W48.5O184]⋅60 H2O (1), K2Na4Li11Co5[Co7(H2O)28P8W48O184]Cl⋅ 59 H2O (2), and K2Na4LiCo11[Co8(H2O)32P8W48O184](CH3COO)4Cl⋅47 H2O (3), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, elemental analyses, and magnetic measurements. The pH value impacts the formation of distinct cobalt-linked frameworks. The cyclic cavity of the polyanion accommodates 5.5, 7, and 8 cobalt ions in 1, 2, and 3, respectively. In compounds 1 and 2, each {Co5.5P8W48} and {Co7P8W48} fragment links to four others through multiple {Co-O-W} coordination bonds to generate a two-dimensional network. Compound 3 can be considered as a 3D network based on the {Co-O-W} coordination bonds and the {Co3(CH3COO)2(H2O)10} linkers between the {P8W48} fragments. Interestingly, acetate ligands have been employed to form the {Co3(CH3COO)2(H2O)10} unit, thereby inducing the construction of a 12-connected framework. To the best of our knowledge, compound 3 contains the largest-ever number of cobalt ions in a {P8W48}-based polyoxometalate when counterions are taken into account and the {P8W48} unit shows the highest number of connections thanks to the carboxyl bridges. The UV/Vis diffuse reflectance spectra of these powder samples indicate that the corresponding well-defined optical absorption associated with Eg can be assessed at 2.58, 2.48, and 2.73 eV and reveal the presence of an optical band gap. The photocatalytic H2 evolution activities of these {P8W48}-based compounds are evaluated.
authors.affiliation: Department Institute of Functional Material Chemistry, Key Lab of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024 (P.R. China), Fax: (+86) 431-5684009.
authors.forename: Yan-Qing
authors.initials: YQ
authors.lastname: Jiao
authors.forename: Chao
authors.initials: C
authors.lastname: Qin
authors.forename: Xin-Long
authors.initials: XL
authors.lastname: Wang
authors.forename: Chun-Gang
authors.initials: CG
authors.lastname: Wang
authors.forename: Chun-Yi
authors.initials: CY
authors.lastname: Sun
authors.forename: Hai-Ning
authors.initials: HN
authors.lastname: Wang
authors.forename: Kui-Zhan
authors.initials: KZ
authors.lastname: Shao
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
mesh_terms: D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006859:Hydrogen / Q000737:chemistry; D008280:Magnetics; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry; D013696:Temperature; D013818:Thermogravimetry; D014414:Tungsten / Q000737:chemistry*; D017973:Tungsten Compounds / Q000737:chemistry; D014466:Ultraviolet Rays; D000099294:Polyoxometalates
chemical_list: D003035:Cobalt; D006859:Hydrogen; D014414:Tungsten; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates
keywords: cobalt; magnetic properties; nanostructures; photochemistry; polyoxometalates; self-assembly