NMR studies of equilibriums in electrolytes: Ionic pairing in glymes

In this article, the formation constants of ionic pairs in salt-low molecular weight analogs of PEO (glyme, diglyme, triglyme) systems are estimated using NMR spectroscopy. The results from 7Li, 11B and 19F NMR titration are compared and the role of the nuclei studied is discussed. It is shown that even in the solvents of very similar coordination (in terms of the donor and acceptor number values) and dielectric properties, the ionic pair formation constant depends on solvent used. The role of the solvent is discussed in terms of effects related to ion agglomerate formation, non-covalent interactions between ions and liquid matrix as well as the number of interacting centers present in the molecules of the solvent. The discrepancies between the results obtained using various nuclei NMR as well as discrepancies between ion pair formation constant calculated for different experimental regimes are also analyzed.