Table 11.

Anion association constants (K_a) for receptors 52 and 53 and that of their corresponding Na⁺ and K⁺ complexes (errors <10%)

	Ka/M−1
	52	[52·2Na+]	[52·K+]	[53·2Na+]	[53·K+]
Cl−a	5	<5	15	<5	150
OBz−a	25	<5	270	20	205
H2PO4−b	10	<5	60	<5	c

^aSolvent: DMSO-d₆/CD₃CN (1/1, v/v).

^bSolvent: 100% DMSO-d₆.

^cNo satisfactory fit to the data could be obtained using EQNMR.