ION PAIRING IN H2O AND D2O SOLUTIONS OF LEAD NITRATE, AS DETERMINED WITH 207Pb NMR SPECTROSCOPY

lead nitrate contact-ion pair equilibrium exchange NMR spectroscopy.

ИОННАЯ ПОДВИЖНОСТЬ И ПРОВОДИМОСТЬ В PbSnF4, ДОПИРОВАННОМ CaF2, ПО ДАННЫМ ЯМР И ИМПЕДАНСНОЙ СПЕКТРОСКОПИИ, КРИСТАЛЛООБРАЗУЮЩИЕ ФУНКЦИИ ПЛОСКОСТЕЙ СКОЛЬЗЯЩЕГО ОТРАЖЕНИЯ В ОРГАНИЗАЦИИ СТРОЕНИЯ РЯДА (Pb, Bi)-СОДЕРЖАЩИХ СУЛЬФИДОВ, ...

The results are analyzed in terms of exchange between a solvated lead ion and the Pb(NO3)+ contact-ion pair. <...> Predictions of the chemical shift difference between the aquated ion and contact-ion pair are carried out for the gas-phase entities and for the solvated species with a DFT calculation. <...> Previously reported data on 207Pb NMR chemical shifts of Pb(NO3)2 in H2O are reevaluated. <...> INTRODUCTION Electrochemical and spectroscopic measurements have demonstrated that dissolution of certain salts in water leads to the formation of contact-ion pairs in equilibrium with fully aquated ions [ 1— 11 ]. <...> For example, Nancollas interpreted changes in conductivity of aqueous lead nitrate solutions as evidence for rapid exchange between contact-ion pairs and solvated ions by the mechanism of Eq. (1) [ 2 ]: Pb(NO ) Pb NO3(aq). 3 (aq) (aq) 2 (1) From the temperature and concentration dependences of the conductivity of lead nitrate solutions, he determined an equilibrium constant, Kdiss, of 0.065 at 298.15 K, and Hdiss = 2.38 kJ/mol and Sdiss = = –14.6 JK–1mol–1 for the process of Eq. (1). <...> Harrison et al. analyzed room-temperature concentration-dependent 207Pb chemical-shift data for aqueous lead nitrate solutions to determine an equilibrium constant for the process in Eq. (1) of 0.812 at 298.15 K [ 4 ]. <...> Altounian et al. measured the temperature and concentration dependences of the NMR chemical shift to determine the variation of the equilibrium constant for the same process in solutions of Pb(NO3)2 in H2O. <...> In unpublished work, Niessen noted the interesting effect that the 207Pb NMR chemical shift of lead nitrate dissolved in a mixed solvent of H2O and deuterium oxide, D2O, is linear in the mole fraction of D2O in the solvent [ 17 ]. <...> Deuterium oxide was purchased from Cambridge Isotopic Laboratories, Inc. The salts were used as received. <...> NMR chemical shieldings were calculated with the NMR module [ 27 ] associated with the ADF program package. <...> Thus, the NMR shift does not distinguish sodium ions coordinated to protonated or deuterated water ligands. 384 F. ALKAN, T. SMALL, S. BAI, A. DOMINOWSKI, C. DYBOWSKI Fig. 1. <...> Extrapolation of the apparent equilibrium constant to m = 0 gives the thermodynamic equilibrium constant <...>

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