A new cryptophane receptor featuring three endo-carboxylic acid groups: synthesis, host behavior and structural study

Examples of a new type of cryptophane molecule incorporating aromatic groups in the bridges (1-4) and, for the first time, being also supplied with three endo-positional ionizable carboxylic acid functions (1) have been synthesized and characterized. The cryptophane triester 2 yielded a solvate (channel inclusion compound) with trichloromethane and water, the X-ray crystal structure of which is reported. The complexation of 1 with low-molecular-weight alcohols in solution was studied, and the liquid-liquid extraction of different metal ions including alkali (Na(+), Cs(+)), alkaline earth (Mg(2+), Ca(2+), Sr(2+), Ba(2+)), and the lanthanide metal ions Eu(3+) and Yb(3+) in an extraction system containing metal nitrate buffer/H(2)O/1/CHCl(3) was examined. Molecular modeling calculations of the cryptophanes 1 and 2, and of the Eu(3+) complex of 1 were carried out contributing to the discussion.