Table 3. Association constants (K/M^–1) for 1 : 1 complexes formed with cations measured by UV/Vis absorption and ³¹P NMR titration experiments at 298 K ^a .

Anion	Cation	HBD	HBA/solvent
			1		2
			MeCN	Acetone	MeCN	Acetone
BPh4–	Guanidinium	8	33 800 ± 2000	— b	198 ± 61	225 ± 40
BPh4–	2-Ethylhexyl ammonium	9	— c	— c	147 ± 25	123 ± 34
BPh4–	Triethyl ammonium	10	— c	— c	85 ± 6	203 ± 50
BPh4–	N-Methyl imidazolium	11	— c	— c	102 ± 12	156 ± 18
BPh4–	Li+	d	27 400 ± 5900	— b	— b	—
BPh4–	Na+	13	390 ± 51	1700 ± 160	— e	73 ± 5
BPh4–	K+	14	— e	270 ± 75	— e	13 ± 3
BPh4–	Rb+	15	— e	220 ± 50	— e	— e
BPh4–	Cs+	16	— e	210 ± 35	— e	— e
BF4–	Ag+	17	— f	— b	8 ± 1	966 ± 40
PF6–	+I(4-tBuPh)2	18	38 300 ± 1100	48 000 ± 3000	62 ± 3	83 ± 12
PF6–	MOIM+	19	23 ± 9	200 ± 60	— e	— e
PF6–	N-Butyl-4-methyl pyridinium	20	12 ± 2	180 ± 40	— e	— e
PF6–	Tetra(n-butyl) ammonium	21	— e	10 ± 2	— e	— e
PF6–	Na+	22	391 ± 35	1700 ± 140	— e	55 ± 13
BF4–	Na+	23	300 ± 90	1900 ± 100	57 ± 6	57 ± 2
BArF4–	Na+	24	400 ± 160	1400 ± 400	53 ± 3	72 ± 2
N(SO2CF3)2–	Na+	25	410 ± 30	1500 ± 200	56 ± 5	78 ± 12
I–	Na+	26	320 ± 120	1000 ± 300	45 ± 1	59 ± 6

^aAverage of at least two titrations. Errors are quoted at the 95% confidence limit. Unless otherwise stated greater than 50% saturation of the binding isotherm was achieved.

^bAssociation constant was too high to be measured using UV/Vis spectroscopy.

^cProtonation of the H-bond acceptor was observed upon addition of guest.

^dLi salt is LiBPh₄ tris(1,2-dimethyoxyethane).

^eAssociation constant was too low to be measured, because the salt was not sufficiently soluble to obtain 50% saturation of the binding isotherm.

^fPoor fit to a 1 : 1 binding isotherm.