organic compounds
2,3-Benzo-1,4-dioxa-7,11,15-triazacycloheptadec-2-ene-6,16-dione, C16H23N3O4, is a 17-membered ring with an envelope conformation in which amide N and ether O atoms form one plane and the amine N atom lies on the flap. 2,3-Benzo-1,4-dioxa-7,10,13-triazacyclopentadec-2-ene-6,14-dione-water (1/2), C14H19N3O4.2H2O, has a 15-membered ring with all the donor atoms in an approximately planar arrangement. The amide groups of this macrocycle are hydrogen bonded to the water molecules. It appears that the availability of the unsubstituted amine N atom is crucial for the extraction and transport of Pb2+ ions. Substitution of a side arm on the amine N atom significantly alters the coordination ability of this N atom in the 17-membered ring and decreases the extraction and transport ability of the macrocycle.