title: New entangled coordination networks based on charge-tunable keggin-type polyoxometalates.
abstract: Investigation into a hydrothermal reaction system with transition-metal (TM) ions, 1,4-bis(1,2,4-triazol-1-lmethyl)benzene (BBTZ) and various charge-tunable Keggin-type polyoxometalates (POMs) led to the preparation of four new entangled coordination networks, [Co(II) (HBBTZ)(BBTZ)2.5 ][PMo12 O40 ] (1), [Cu(I) (BBTZ)]5 [BW12 O40 ]⋅H2 O (2), [Cu(II) (BBTZ)]3 [AsW(V) 3 W(VI) 9 O40 ]⋅10 H2 O (3), and [Cu(II) 5 (BBTZ)7 (H2 O)6 ][P2 W22 Cu2 O77 (OH)2 ]⋅6 H2 O (4). All compounds were characterized by using elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The mixed valence of W centers in compound 3 was further confirmed by using XPS spectroscopy and bond-valence sum calculations. In the structural analysis, the entangled networks of 1-4 demonstrate zipper-closing packing, 3D polythreading, 3D polycatenation, and 3D self-penetration, respectively. Moreover, with the enhancement of POM negative charges and the use of different TM types, the number of nodes in the coordination networks of 1-4 increased and the basic metal-organic building motifs changed from a 1D zipper-type chain (in 1) to a 2D pseudorotaxane layer (in 2) to a 3D diamond-like framework (in 3) and finally to a 3D self-penetrating framework (in 4). The photocatalytic properties of compounds 1-4 for the degradation of methylene blue under UV light were also investigated; all compounds showed good catalytic activity and the photocatalytic activity order of Keggin-type species was initially found to be {XMo12 O40 }>{XW12 O40 }>{XW12-n TMn O40 }.
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024 (P.R. China).
authors.forename: Xiu-Li
authors.initials: XL
authors.lastname: Hao
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Ma
authors.forename: Yong-Hui
authors.initials: YH
authors.lastname: Wang
authors.forename: Long-Yang
authors.initials: LY
authors.lastname: Xu
authors.forename: Fu-Chen
authors.initials: FC
authors.lastname: Liu
authors.forename: Mao-Mao
authors.initials: MM
authors.lastname: Zhang
authors.forename: Yang-Guang
authors.initials: YG
authors.lastname: Li
keywords: Keggin-type; entangled coordination networks; photochemistry; polyoxometalates