Browsing by Author "Symons, Martyn C. R"

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    Solvation Spectra Part 52.1—The Aquation of Silver Atoms and Cations: a Radiation and Electron Spin Resonance Study
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (10), 1977) Brown, D. Robert; Symons, Martyn C. R
    Exposure of a range of aqueous solutions containing AgI cations to 60Co γ-rays at 77 K gave AgII and AgO together with other paramagnetic products. The AgII centres have [graphic omitted] configurations, which means that linear solvation for Ag+ is unlikely, since this would lead to a [graphic omitted] configuration. A range of distinct AgO centres displaying low (∼80 %) atom character was detected. Their yield was enhanced, but their distribution largely unaltered, when certain additives, such as potassium fluoride, were used to give glassy solids. However, their distribution varied with dose and with temperature. The major initial product exhibited an extra 6 G doublet splitting due to hyperfine coupling to a single proton. On further irradiation, this centre was superceded by others exhibiting no resolved coupling to protons but, in some cases, well defined g and A anisotropy. For all the AgO centres, gav was less than the free-spin value. When water enriched in 17O was used, superhyperfine coupling was detected for some of the AgO centres. From the apparent anisotropic and isotropic coupling constants, delocalisation of ∼5% per water molecule was deduced. The intensities indicated the presence of several equivalent water ligands but solvation numbers could not be derived accurately. These results for AgO are significant for two reasons; (1) they show that solvation is not lost in aqueous glasses when the charge on an ion is neutralised. This contrasts with the fact that when small neutral molecules become charged, solvation is acquired, even at 77 K. (2) They indicate the presence of a range of discrete AgI solvates in solution rather than a single preferred unit.
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    Solvation Spectra Part 54.1—A Low Temperature Infrared Spectroscopic Study of the Solvation of Ions in Methanol
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (11), 1977) Strauss, Imants M; Symons, Martyn C. R
    Broad featureless bands in the O—H stretching region for CH3OH in CH3OD containing a range of 1:1 electrolytes become narrower on cooling below the glass point and usually display several features. Lithium and sodium salts up to ∼3 mol kg–1 show narrow bands on the high-frequency side of the bulk methanol band that are assigned to solvent molecules bonded to the anions. The bulk methanol bands are broadened and shifted by the cations, but separate bands for the cation solvates are not resolved. At higher concentrations of salt, the anion bands are also shifted by the cations to give new high frequency bands assigned to solvent shared ion-pairs. Tetra-alkyl-ammonium salts in the 1 mol kg–1 region give new bands characteristic of the anions only. Sodium tetraphenylboron gives a narrow component at 3520 cm–1 and a very broad component centred at ∼3360 cm–1. The former is assigned to two O—H groups bonded to a single methanolic oxygen atom: the latter is assigned to oscillators in short chains or cyclic structures. A broad band at ∼3360 cm–1 for other concentrated electrolyte solutions is assigned similarly.