Table 1.

Anion Affinities for Hosts 1 and 2

anion	host 1,a KNMR (M−1)	host 1,a KITC (M−1)	host 2,b $K_{\mathrm{a}}^{\text{cav}}$ (M−1)	host 2,b $K_{\mathrm{a}}^{\text{crown}}$ (M−1)
PF6−	1560	2303	>5000c	3600
CF3SO3−	67	314	>5000d	710
ReO4−	322	371	7200	1800
ClO4−	95	160	4300	2400
BH3CN−	67	152	3600	1300
BF4−	e	e	35	1200
SCN−	33	44	2000	830
I−	11	17	930	3200f
CCl3CO2−	5383	6337	70300g	h
CHCl2CO2−	50	52	1500	e
Br−	e	e	17	740
NO3−	e	e	95	180
Cl−	e	e	e	120
F−	e	e	e	e

^aAffinities for 1 determined using ¹H NMR spectroscopy and ITC are taken from an earlier report.^11a

^bAffinities to 2 were determined using ¹H NMR spectroscopy (10 mM phosphate buffered D₂O, pD = 7.3). Determinations involving 2 were carried out in at least triplicate, with errors (CV) in anion affinity generally <10% for most anions (see Supporting Information for details). Unless otherwise noted, determinations of $K_{\mathrm{a}}^{\text{cav}}$ utilized the H_b (Figure 2) signal of free 2, whereas $K_{\mathrm{a}}^{\text{crown}}$ determinations utilized the H_j (Figure 2) signal of the 2·Ada-CO₂⁻ complex.

^cH_b signal shifts indicated strong binding, but pseudospecific binding to the trimethylammonium groups prevented accurate determination.

^dH_b signal shifts indicated strong binding, but due to overlap with the host benzylic signal, insufficient data could be collected.

^eBinding too weak to determine accurately.

^fK_a with 1:1 model of the H_l (Figure 2) signal fitting to the titration using the 2·Ada-CO₂⁻ complex.

^gDetermined using ITC.

^hUnable to estimate 1:1 binding to crown due to competitive displacement of guest of 2·Ada-CO₂⁻ complex.