A New Cryptophane Receptor Featuring Three endo‐Carboxylic Acid Groups: Synthesis, Host Behavior and Structural Study

Abstract

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.

Cryptophanes and Their Complexes—Present and Future

“…The syn-isomer 10, an achiral molecule, extracts a number of different metal ions with a large affinity for Ca 2+ and Sr 2+ and almost no affinity for Na + , following the sequence Ca 2+ ∼ Sr 2+ > Mg 2+ > Ba 2+ > Cs + > Na + (Figure 26). 30 The high affinity of 10 for Ca 2+ and Sr 2+ is in good agreement with their strong interaction with carboxylate anions and is a consequence of the preorganization of the host, in which the endooriented carboxylic acid functions favor the 1:1 complex formation. Furthermore, for the same reasons, the trivalent lanthanide ions Yb 3+ and Eu 3+ are also efficiently extracted by cryptophane 10, whose binding properties are comparable to that of spherand hosts.…”

“…50,121 Cryptophane-A (1) and one of its labeled analogues were mixed together with xenon, and 129 Xe NMR spectra were recorded. For example, when cryptophane-A-d 30 (81) was mixed with 1, at low temperature, two well-resolved resonances were observed at low frequency, corresponding to xenon encapsulated in the cavity of each cryptophane (Figure 37). The high sensitivity of the xenon resonance led to the discrimination of both cryptophanes (∆δ ) 1.2 ppm), differing only by their hydrogen or deuterium composition.…”

Isolation and Structure of an “Imploded” Cryptophane

“…[1,9] Furthermore, they display an impressive ability to bind and discriminate between guests on the basis of size, shape, and electronic characteristics in both hydrophilic and lipophilic solvents. We report herein the synthesis of a new exo-ester-functionalized mxylyl-bridged cryptophane [10] (AE )-anti-1 (Scheme 1) and the structure and thermal behavior of its crystalline inclusion compound with tetrahydrofuran (THF). Our studies reveal that, once emptied, the cryptophane containers equilibrate between "empty" and "imploded" conformers at high temperatures in the solid state, the latter of which is a kinetically stable atropisomer that has been isolated and structurally characterized.…”

Spontaneous chiral resolution directed by symmetry restriction and π-π interaction

“…New progress in the domain of macrocyclic CTV-based hosts includes applications in material science, sensing and separations232425262728. Owing to a pyramidal shape and convergent binding modes, CTV itself and CTV-based ligands are capable of forming coordination complexes with group one elements and transition metals29303132333435363738394041424344. Hardie et al conducted excellent works on pyridyl decorated CTV derivatives that form discrete or infinite metallo-supramolecular assemblies333435363738.…”

“…Hardie et al conducted excellent works on pyridyl decorated CTV derivatives that form discrete or infinite metallo-supramolecular assemblies333435363738. When it comes to carboxylic acid decorated CTV ligands, only a few structures have been reported394041424344, and their transition metal complexes are even rarer424344. We recently reported the first CTV based 1D ternary independent nanotubular framework with permanent porosity44.…”