| Popis: |
Dihydroxycrownophanes (2a—c) were conveniently synthesized by intramolecular [2 + 2] photocycloaddition, and their derivatives with two cation-ligating side chains (3a—6a) were also readily prepared by the reaction of 2a—c and the corresponding halides in the presence of NaH. All of the crown compounds obtained were used as ionophores in single extraction experiments of heavy metal cations including transition metal cations in a H2O–CH2Cl2 system. Although 3a did not extract any alkaline earth metal cation at pH 7.0, it showed high affinity toward Pb2+ even under acidic conditions (pH 4.7). Crownophanes (4a—c) having two 2-pyridylmethyl ligands efficiently extracted Ag+ with excellent selectivity. |
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