4.6 Author:
   Suezawa, Hiroko; Horiike, Norikazu; Yamazaki, Satomi; Kamachi, Hiroshi; Hirota, Minoru
Reference:
   Journal, JPCHAX, J.Phys.Chem., EN, 95, 26, 1991, 10787-10796
Title:
   Multinuclear NMR Spectroscopic Studies on Ionic Interactions. Interactions between Nitrogen Cations and Halide Ions
Abstract:
The NMR line widths of 14N nuclei in cations and 35Cl, 81Br, and 127I nuclei of halide ions of several pyridinium and anilinium halides were measured in aqueous solutions of rather high concentrations (0.5-4.0 m).Intrinsic line width (W), defined by W = Dn1/2T/k, was shown to be convenient for correlating the line width of quadrupolar nuclei with molecular size and other properties of these cations.The W(14N) was shown to be insensitive to the concentration of the solution and to be proportional to the size of the cation at least when compared within the series of 4-substituted pyridinium and anilinium halides.In the W vs concentration plots of halide (35Cl, 81Br, and 127I) ions, a characteristic plateau whose height reflected the size of the nitrogen countercation was observed in the concentration range from 1.5 to 3 m.These findings suggest the presence of contact ion pairs in this concentration range.