A new doubly armed crown compound fused in a cyclophane skeleton was prepared by intramolecular [2 + 2] photocycloaddition. The compound efficiently extracted Ag+ with excellent selectivity in a liquid-liquid system, and the high Ag+-affinity was not reduced even at low pH region.
Azacryptophane was obtained by irradiation of the precursor diammonium chloride in the presence of γ-CD (γ-cycodextrin) in aqueous solution. In the liquid-liquid extraction, the azacryptophane showed a moderate affinity toward all alkali metal picrates without any significant selectivity, whereas it selectively extracted both Ag+ and Pb2+ cations in series of heavy metal nitrates.