MACROCYCLES FOR RADIONUCLIDE CAPTURE. Alexander Sobolev,^A Zouhair Asfari,^B Volker Böhmer,^C Jack Harrowfield^A and Jacques Vicens^{B A}University of Western Australia, ^BUniversité Louis Pasteur de Strasbourg, ^CUniversität Mainz

Many derivatives of the macrocyclic oligophenols known as the "calixarenes" have attracted considerable interest for their metal ion binding ability, and it is well-established that they may both selectively and strongly bind to heavy metals such as caesium, the lanthanides and the actinides. Some of these ligands are therefore under consideration as reagents for use in the treatment of nuclear waste. As part of the analysis of coordination selectivity and ultimately the optimisation of ligand design, it is essential to know the structures and conformations of the "free" ligands, and in the conduct of such a programme of research we have recently determined the structures of the ligands 1, 2, 3 and 4.

(2) R = H, Bridge = OCH₂CH₂O

(3) R = (CH₃)₃C, Bridge = OCH₂CH₂O

(4) R = H, Bridge = 1,3 -C₆H₄O₂