ION PAIRING IN H2O AND D2O SOLUTIONS OF LEAD NITRATE, AS DETERMINED WITH 207Pb NMR SPECTROSCOPY
F. Alkan, T. Small, S. Bai, A. Dominowski, C. Dybowski
University of Delaware, Newark, Delaware 19716, USA
Keywords: lead nitrate, contact-ion pair, equilibrium, exchange, NMR spectroscopy
Abstract
The temperature and concentration dependences of 207Pb NMR chemical shifts of Pb(NO3)2 in D2O are reported. 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. From the analysis, the enthalpy of dissociation of the contact-ion pair is found to be -42.3±1.0 kJ/mol.
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