Lipophilic ditopic guanidinium receptors: selective extractants for tetrahedral oxoanions

Abstract

Ditopic open-chain guanidinium receptors have been developed especially for a selective extraction of tetrahedral oxoanions. The anion extraction behaviour of these host compounds has been studied in the system sodium salt-H₂O-buffer/host-CHCl₃. Lipophilic bisguanidines are capable of extraction of even strongly hydrated anions as hydrogen phosphate, sulfate and nucleotides over a wide pH range. A remarkable selectivity of sulfate over hydrogen phosphate was obtained using receptors 2, 5 and 7. The ditopic host 2 shows a pronounced preference for ATP versus ADP and AMP. The 1:1 complex formation observed in the organic phase points to a well-organized complex structure for the oxoanions investigated and ditopic hosts.