Wheel-Shaped Cu20-Tungstophosphate [Cu20X(OH)24(H2O)12(P8W48O184)]25− Ion (X = Cl, Br, I) and the Role of the Halide Guest
| العنوان: | Wheel-Shaped Cu20-Tungstophosphate [Cu20X(OH)24(H2O)12(P8W48O184)]25− Ion (X = Cl, Br, I) and the Role of the Halide Guest |
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| المؤلفون: | Naresh S. Dalal, Johan van Tol, Ulrich Kortz, Rosa Ngo Biboum, Josep Poblet, Xavier López, Bineta Keita, Sib Sankar Mal, Masooma Ibrahim, Saritha Nellutla, Jorge A. Fernández, Bassem S. Bassil |
| المصدر: | Inorganic Chemistry. 48:11636-11645 |
| بيانات النشر: | American Chemical Society (ACS), 2009. |
| سنة النشر: | 2009 |
| مصطلحات موضوعية: | chemistry.chemical_classification, Chemistry, Iodide, Analytical chemistry, Infrared spectroscopy, Magnetic susceptibility, law.invention, Inorganic Chemistry, Magnetization, Crystallography, Unpaired electron, law, Physical and Theoretical Chemistry, Ground state, Electron paramagnetic resonance, Hyperfine structure |
| الوصف: | We have synthesized the known [Cu(20)Cl(OH)(24)(H(2)O)(12)(P(8)W(48)O(184))](25-) (1) and report here its bromide and iodide analogues, [Cu(20)Br(OH)(24)(H(2)O)(12)(P(8)W(48)O(184))](25-) (2) and [Cu(20)I(OH)(24)(H(2)O)(12)(P(8)W(48)O(184))](25-) (3). These polyanions were characterized in the solid state by IR spectroscopy and single-crystal X-ray diffraction. Magnetic susceptibility and magnetization data over 1.8-300 K show that the Cu(2+) ions in 1-2 are antiferromagnetically coupled, leading to a diamagnetic ground state. The effective exchange coupling constant J(eff) was estimated as approximately -3 K for both 1 and 2. Electron paramagnetic resonance measurements were made on 1 and 2 over 5-295 K at microwave frequencies of 9.5, 34, and 220 GHz. The observed (weak) signals were characteristic of randomly distributed Cu(2+) ions only, with g values and hyperfine constants typical of the unpaired electron in a 3d(x(2)-y(2)) orbital of Cu(2+). No signals attributable to the copper-hydroxo cluster were detected, supporting the conclusions from the magnetization measurements. DFT calculations were performed as well to obtain additional information on the anionic guest inside the cavity created by the copper-hydroxo cage related to electronic structure and energies of encapsulation. The polyanions 2 and 3 were also characterized by cyclic voltammetry (CV) in a pH 5 medium. Their CVs are composed by an initial two-step reduction of the Cu(2+) centers to Cu(0) through Cu(+), followed at more negative potential by the redox processes of the W centers. A comparison with the CV characteristics of the previously studied compound 1 indicates that the potential locations of the Cu or W waves of the three analogues do not depend significantly upon the identity of the central halide X. This observation is in accordance with conclusions of DFT calculations. The modified electrodes based on 2 and the room-temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate triggers an efficient reduction of nitrate. To our knowledge, this is the first example of electrocatalytic nitrate reduction by a polyanion entrapped in room-temperature ionic liquid films. |
| تدمد: | 1520-510X 0020-1669 |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::aa159d004a96e398ff2b49c9ee4b0137 https://doi.org/10.1021/ic901641f |
| رقم الأكسشن: | edsair.doi.dedup.....aa159d004a96e398ff2b49c9ee4b0137 |
| قاعدة البيانات: | OpenAIRE |
Find this issue from the American Chemical Society | تدمد: | 1520510X 00201669 |
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