Weak and Reversible Binding of Alkali Metal Ions (Na+/K+) by an Aza-Oxa Cryptand

摘要

A laterally asymmetric cryptand incorporating amino N and ethereal O was utilized to bind the hard alkali metal ions (Na+ and K+) in aqueous medium. Single crystal X-ray diffraction studies revealed that both Na+ and K+ ions were included inside the cryptand cavity. However, the trapped metal ions were weakly bound and could be released from the cavity of the cryptand. This cryptand had been used as a column chromatographic material for trapping Na+ and K+ ions from water as the trapped metal ion could be released back into water to extract the cryptand in its free state. Metal binding capability of the cryptand was evaluated using computational studies that revealed lower binding energy (B.E.) for the Na+ and K+ ions compared to first row transition metal ions.