New macrobicycles containing a tetralactam moiety: Template synthesis and study of their binding with lanthanides

The synthesis of macrobicyclic cryptands 1, 2 from an 18-membered diazatetr alactam and 6,6'-bis(bromomethyl)-2,2'-bipyridine or 2,6-bis(3-bromomethy1- 1-pyrazolyl)pyridine has been investigated using various metal carbonates. The analysis of the distribution products by gel permeation chromatography showed that macrocyclization process was markedly conditioned by cation tem plate effects. Optimum yields were obtained for Li+ and Na+ in the preparat ion of 1 and 2, respectively. The cryptate structure of the corresponding c omplexes of Ln(III) (Ln=Eu, Tb, Gd) is discussed on the basis of spectrosco pic and photophysical data. (C) 2000 Elsevier Science Ltd. All rights reser ved.