NMR spectroscopy of silver and arsenic containing solids

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Liu, Xiaolong
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University of Guelph

Using high resolution CP/MAS NMR techniques, a series of organosilver compounds has been systematically studied by solid state 109Ag and 13C NMR spectroscopy. The chemical shift tensors obtained from the slow CP/MAS 109Ag and 13C NMR spectra have provided valuable structural information, most of which is in good agreement with the available crystal structure data. Computational studies have been carried out on a series of silver compounds. The slope between 109Ag experimental chemical shifts and calculated chemical shieldings at B3LYP/DGDZVP level is -1.1, which is very close to the theoretically ideal value of -1 and is good enough to be used to predict isotropic chemical shifts. Deuterium NMR spectra lineshapes and spin lattice relaxation times were used to investigate the molecular dynamics of the benzene silver perchlorate complex. Deuterium NMR spectra indicate that the benzene ring is rapidly reorienting about its 6-fold axis. Activation energies obtained from fitting the T 1 curve as a function of temperature were 23.9 ± 0.5 kJ/mol; simulations of the spectral lineshapes gave 23.2 ± 1.0 kJ/mol. T 1 measurements showed a phase transition at 303 (±3) K. In order to compare the 109Ag and 13C CP/MAS spectra to the low temperature phase, the solid state 109Ag and 13C NMR spectra were obtained at 320 K. The 109Ag chemical shift tensor values differ significantly between the two phases, where those for 13C show very little change. NMR measurements of chemical shifts and nuclear quadrupolar coupling constants ([chi]) of Arsenic and Iodine nuclei have been performed on Me 4AsI and Me4NI. 75As [chi] value of 12.38 ± 0.30MHz has been obtained for Me4AsI. Moreover, 127I [chi] values of Me4AsI and Me4NI were 62.0 ± 0.5 and 23.6 ± 0.2 MHz, respectively. The indirect spin-spin coupling constant 1J (13C-75As) was obtained as 20 ± 2 Hz for Me4AsI. This represents the first reported measurement of a 13C-75As J-coupling value.

high resolution, CP/MAS NMR techniques, organosilver compounds, solid state 109Ag spectroscopy, 13C NMR spectroscopy