The reactions of various derivatives of chelidamic acid (4-hydroxypyridine-2,6-dicarboxylic acid) with p-tert-butylcalixarene have produced several new mono- and difunctionalized derivatives of the calixarene in which tridentate functional groups suitable for the binding of rare earth metal cations have been incorporated. Single-crystal X-ray structure determinations have been performed on two difunctionalized calixarenes found to adopt different "cone" and "1,2-alternate" conformations, as well as on a complex of europium(III) with the phenoxide form of a monofunctionalized ligand, this structure confirming that charge factors are dominant in determining the site of lanthanide metal binding in these ligands.
Froidevaux, P., Harrowfield, J. M., & Sobolev, A. (2000). Calixarenes as Scaffolds: Introduction of Tridentate Rare Earth Metal Binding Units into Calixarene. Inorganic Chemistry, 39(2000), 4678-4687. https://doi.org/10.1021/ic000353z