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Issue 20, 2016
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pH-Controlled assembly of two novel Dawson-sandwiched clusters involving the in situ reorganization of trivacant α-[P2W15O56]12− into divacant α-[P2W16O57]8−

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Abstract

Modified classical trivacant Wells-Dawson α-[P2W15O56]12− and the assembly of related sandwiched transition metal clusters are of interest, but surprisingly few reports of these materials exist because of the sensitivity of α-[P2W15O56]12− to the assembly environment. Herein, we describe the pH-controlled assembly of two novel Dawson-sandwiched clusters, (H2bpz)6[Co2(P2W16O57)2]·22H2O (1, bpz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole) and (H2bpz)6[Co3H2(P2W16O57)(P2W15O56)(H2O)]·12H2O (2), involving the in situ transformation of α-[P2W15O56]12−. Both clusters were characterized by X-ray single-crystal diffraction, FT-IR spectroscopy, UV-Visible spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and elemental analyses. X-ray crystallography showed that both heteropolytungstates become divacant α-[P2W16O57]8− and symmetrically encapsulate two edge-shared CoO6 octahedra in the interior in 1, while only one divacant α-[P2W16O57]8− is observed in 2, which combined with another trivacant α-[P2W15O56]12− to asymmetrically clamp three edge-shared CoO6 octahedra. The α-[P2W16O57]8− heteropolytungstate should be generated in situ from α-[P2W15O56]12−via self-decomposition equilibria in solution. Their electrochemical behaviors reveal characteristic multi-electron redox processes related to WVI centers. The electrocatalytic reduction performances toward nitrite, hydrogen peroxide, chlorate, bromate and iodate were fully measured and discussed; among these species, both clusters exhibit the best electrocatalytic activity towards the reduction of bromate. Magnetic measurements indicate weak ferromagnetic exchange interactions between Co atoms sandwiched by vacant polyoxometalates.

Graphical abstract: pH-Controlled assembly of two novel Dawson-sandwiched clusters involving the in situ reorganization of trivacant α-[P2W15O56]12− into divacant α-[P2W16O57]8−

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Supplementary files

Article information


Submitted
29 Feb 2016
Accepted
09 Apr 2016
First published
12 Apr 2016

Dalton Trans., 2016,45, 8404-8411
Article type
Paper
Author version available

pH-Controlled assembly of two novel Dawson-sandwiched clusters involving the in situ reorganization of trivacant α-[P2W15O56]12− into divacant α-[P2W16O57]8−

L. Guo, M. Jagodič, S. Zeng, Z. Wang, Z. Shi, X. Wang, C. Tung and D. Sun, Dalton Trans., 2016, 45, 8404
DOI: 10.1039/C6DT00793G

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