Figure 1.

(a) ¹H (top) and ¹³C (bottom) NMR spectra of 1H (blue) and 1D (red) in DMSO-d₆. C^ab is the aryl carbon between H^a and H^b. (b) Binding isotherm with Cl^– for 1:1 1H:1D in DMSO-d₆ by ¹H (solid lines) and ¹³C (dashed lines) NMR spectroscopy; lines added as a guide for the eye. Isotherm shape is consistent with weak 1:2 binding where K_a^1:1 ≫ K_a. ¹³C NMR peaks are used for linear EIE fitting; the isotherms overlap, although the peaks are resolved. (c) Linearized plot of K_a^H/K_a (eq 1) for 1H:1D¹³C NMR peak corresponding to alkyne C¹.