Macrocyclic ligands for uranium complexation

Macrocycles with cavity diameters in the region 4.5-5.2 Angstrom, based on computer modeling studies, have been prepared by high dilution cyclocondensation of 2-aminopyridyl substituted biurets and thiobiurets with appropriately substituted, reactive intermediates such as chlorocarbonyl isocyanate and malonyl dichloride. Detailed high field 1H NMR studies have been used to identify all protons in these macrocycles for structural verification and in confromation studies, and by-products obtained in their synthesis as well as in complexation studies have been characterized and identified using these NMR techniques, as well as single crystal X-ray studies. 5 refs