Synthesis, structure and ion extraction properties of novel monooxa-diselkylene-1,ω-dioxy substituted calix[4]arene derivatives

Novel macrocyclic monooxa-diselkylene-1,omega-dioxy substituted calix[4]arene derivatives 1a-5a were synthesized by the reaction of calix[4]arene dibromides 1-5 with the disodium salt of bis(2-selenylethyl)ether in the yields between 28% and 64%. Their structures were characterized by proton and carbon NMR spectra. X-Ray structure analysis of 1a further confirmed the cone conformation of compounds 1a-5a. An interesting host-guest complex of 1a with dichloromethane via CH/pi and Cl/pi interactions was elucidated. Extraction experiments showed that these novel monooxa-diselkylene-1,omega-dioxy substituted calix[4]arene derivatives 1a-5a had strong extraction ability towards mercury ion. The interaction of Hg2+ with the calix ligand has also been investigated by H-1 NMR titration.