Anion added

Compound 5

beta-octamethoxy-

meso-tetraspirocyclohexyl

calix[4]pyrrole

Compound 8

beta-octabromo-

meso-octamethyl

calix[4]pyrrole
fluoride

1.7 (± 0.2) x 102

2.7 (± 0.4) x 104b

chloride

<10

4.3 (±0.6) x 103

dihydrogen phosphate

not determined

6.5 (± 0.4) x 102

Table 3 Stability constants for compounds 5 and 8 with anionic substratesa in CD2Cl2 at 298K.

Footnotes to Table 3

aAnions were added as 0.03 M CD2Cl2 solutions of their tetrabutylammonium salts to 3 mM solutions of the receptor in CD2Cl2 with concentration changes being accounted for by EQNMR. In determining the stability constants, the possible effects of ion pairing (if any) were ignored. bEstimated value. The NH proton resonance broadened considerably during the titration, forcing the frequency of the resonance to be noted manually. This value should, therefore, be treated with caution.

Link to Table 1 - 'beta-free' analogues

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