| 1. |
- Sharma, Rupali, et al.
(author)
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pH-Dependent solution dynamics of a manganese(II)polyoxometalate, [Mn-4(H2O)(2)(P2W15O56)(2)](16-), and [Mn(H2O)(6)](2+)
- 2015
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 44:44, s. 19068-19071
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Journal article (peer-reviewed)abstract
- The aqueous reaction dynamics of the manganese(II)-functionalised Wells-Dawson polyoxometalate [Mn-4(H2O)(2)(P2W15O56)(2)](16-) has been determined as a function of pH using variable temperature O-17 NMR, and compared with that of the well-studied monomeric manganese(II) hexa-aqua ion, [Mn(H2O)(6)](2+). While the rate of aquo-ligand exchange on the hexa-aqua ion remains independent of pH in the range 3.2-6.0, the rate of water exchange of the polyoxometalate ion varies by a factor of fifteen, from 1.98 x 10(7) s(-1) at pH 3.2 to 1.3 x 10(6) s(-1) at pH 6.0. This decrease in the rate of exchange correlates with the deprotonation of the polyoxometalate framework.
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| 2. |
- Sharma, Rupali, et al.
(author)
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Predicting O-17 NMR chemical shifts of polyoxometalates using density functional theory
- 2016
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:11, s. 8235-8241
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Journal article (peer-reviewed)abstract
- We have investigated the computation of O-17 NMR chemical shifts of a wide range of polyoxometalates using density functional theory. The effects of basis sets and exchange-correlation functionals are explored, and whereas pure DFT functionals generally predict the chemical shifts of terminal oxygen sites quite well, hybrid functionals are required for the prediction of accurate chemical shifts in conjunction with linear regression. By using PBE0/def2-tzvp//PBE0/cc-pvtz(H-Ar), lanl2dz(K-) we have computed the chemical shifts of 37 polyoxometalates, corresponding to 209 O-17 NMR signals. We also show that at this level of theory the protonation-induced pH dependence of the chemical shift of the triprotic hexaniobate Lindqvist anion, [HxNb6O19]((8-x)), can be reproduced, which suggests that hypotheses regarding loci of protonation can be confidently tested.
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| 3. |
- Spillane, Samuel, et al.
(author)
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Non-aqueous microwave-assisted syntheses of deca- and hexa-molybdovanadates
- 2017
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In: Angewandte Chemie International Edition. - : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 56, s. 8568-8572
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Journal article (peer-reviewed)abstract
- We report a new approach for the synthesis of heterohexa- and heterodecametalates via the use of non-aqueous, microwave-assisted reaction conditions. The two novel molybdovanadates have been isolated and characterized in the solid and solution states using single-crystal X-ray diffraction, FT-IR, UV/Vis, multinuclear NMR spectroscopy, and ESI-MS. The relative stabilities of the possible structural isomers were probed using dispersion-corrected DFT calculations for both polyoxometalate systems.
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