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 diazatetralactam and 6,6′-bis(bromomethyl)-2,2′-bipyridine or 2,6-bis(3-bromomethyl-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 template effects. Optimum yields were obtained for Li+ and Na+ in the preparation of 1 and 2, respectively. The cryptate structure of the corresponding complexes of Ln(III) (Ln=Eu, Tb, Gd) is discussed on the basis of spectroscopic and photophysical data.