Table 3. Summary of calculated binding affinities, K_a (M^–1) as determined by UV-Vis spectroscopy in two separate solvent systems ^a .

Anions a	3b b	3b c	7b c
H2PO4–	(8 ± 2) × 106	(2.1 ± 0.3) × 103	(1.4 ± 0.2) × 105
HP2O73–	(1.4 ± 0.1) × 105	(3.8 ± 0.6) × 103	(3.6 ± 0.2) × 104
HSO4–	(4.1 ± 0.2) × 103	nd	nd
NO3–	nd	nd	nd
Cl–	nd	nd	nd

^aThe anions were studied as their TBA⁺ salts.

^bIn CHCl₃; data from ref. 24.

^cIn CHCl₃ containing 3% (v/v) CH₃OH.