Lh. Uppadine et al., Ion pair cooperative binding of potassium salts by new rhenium(I) bipyridine crown ether receptors, INORG CHEM, 40(12), 2001, pp. 2860-2869
The new rhenium(I) bipyridine crown ether receptors 1-4 have been prepared
and their ion pair recognition properties examined. The crystal structure o
f [1 . KCl](2). 2H(2)O demonstrates that potassium is coordinated by benzo-
18-crown-6 and chloride is hydrogen bonded to the amide groups. Receptor 3
extracts solid KCl and KOAc into chloroform via ion pair complexation. NMR
and emission titration studies with receptors 1-4 and KCl/KOAc show that co
bound potassium enhances anion binding strength by electrostatic and confor
mational effects. Significant cooperative interactions are observed between
the anion and cation sites for host 4 in CH3CN. This molecule coordinates
potassium to form a 1:1 intramolecular sandwich complex, which preorganizes
the host for acetate binding.