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 function (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 (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), and the lanthanide metal ions Eu³⁺ and Yb³⁺ in an extraction system containing metal nitrate buffer/H₂O/1/CHCl₃ was examined. Molecular modeling calculations of the cryptophanes 1 and 2, and of the Eu³⁺ complex of 1 were carried out contributing to the discussion.