Generation of Cryptophanes in Water by Disulfide Bridge Formation

Self-assembled tetrazine cryptophane for ion pair recognition and guest release by cage disassembly

Hereby, we describe the synthesis of a self-assembled syn-cryptophane using dynamic nucleophilic aromatic substitution of tetrazines. 1H NMR cage titrations reveal that the tetramethylammonium cation binds under slow exchange conditions while counter-anions show a fast exchange regime. Finally, the cryptophane can be disassembled by the addition of thiols allowing guest release.

A Water-Soluble Cryptophane Decorated with Aromatic Amine Groups Shows High Affinity for Cesium and Thallium(I)

An anti-cryptophane decorated with three aromatic amine and three phenol groups shows a high affinity for the cesium and thallium cations in LiOH/H2O (0.1 M). The formation of the complexes was studied by 133Cs NMR and by 205Tl NMR spectroscopy at different temperatures. Characteristic signals for caged cesium and thallium were observed at a high field with respect to the signals of the free cations present in the bulk. Isothermal titration calorimetric experiments performed in LiOH/H2O (0.1 M) and NaOH/KCl buffer (pH = 13) allowed us to determine the parameter of complexation and to ascertain the high affinity of this cryptophane for cesium and thallium. A comparison with other cryptophanes that bind these two cations shows that the introduction of nitrogen atoms into the cryptophane backbone has an effect on the binding properties. The affinity for cesium and thallium(I) ions is in the following order of substitution: OH > NH2 > OCH2COOH. This study paves the way to the design of new efficient host molecules for the extraction of these two cations in aqueous solution.

Alkynylgold(I) C3 -Chiral Concave Complexes: Aggregation and Luminescence

Chiral gold(I) acetylide trinuclear complexes 1-3 based on the cyclotribenzylene platform and terminal PR₃ ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission studied. They exhibited long-lived blue phosphorescence in CHCl₃ and a weak fluorescence in the UV. In MeOH/CHCl₃ mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30-80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac-1, suggesting that the latter is a true racemate.

Hemicryptophane Cages with a C1-Symmetric Cyclotriveratrylene Unit

Two new hemicryptophanes combining a cyclotriveratrylene unit with either an aminotrisamide or a tris(2-aminoethyl)amine (tren) moiety have been synthesized. Although a conventional synthesis approach was used, the molecular cages obtained are devoid of the expected C₃ symmetry. NMR analyses and X-ray crystal structure determination showed that these hemicryptophanes exhibited C₁ symmetry due to the unusual arrangement of the substituents of the cyclotriveratrylene unit. This unprecedented arrangement is related to a change in the regioselectivity of the Friedel-Crafts reactions that led to the CTV cap. This constitutes an original approach to access enantiopure chiral molecular cages with low symmetry.