Synthesis of calix[4]crowns containing soft and hard ion binding sites via click chemistry

A series of triazole-modified calix[4]crowns, 3, containing hard and soft ion binding sites were synthesized in good yields via click chemistry. The hard and soft ion binding sites may selectively complex alkali metal or transition metal cations. Compound 3a shows good complex selectivity towards Pb2+ and 3c shows the highest Li+/K+ extraction ratio, suggesting that the triazole groups play an important role in metal ion binding.