Rational Design of a Nonbasic Molecular Receptor for Selective NH4+/K+Complexation in the Gas Phase

Ammonium halide selective ion pair recognition and extraction with a chalcogen bonding heteroditopic receptor

The first example of a heteroditopic receptor capable of cooperative recognition and extraction of ammonium salt (NH4X) ion-pairs is described. Consisting of a bidentate 3,5-bis-tellurotriazole chalcogen bond donor binding cleft, the appendage of benzo-15-crown-5 (B15C5) substituents to the tellurium centres facilitates binding of the ammonium cation via a co-facial bis-B15C5 sandwich complex, which serves to switch on chalcogen bonding-mediated anion binding potency. Extensive quantitative ion-pair recognition 1H NMR titration studies in CD3CN/CDCl3 (1 : 1, v/v) solvent media reveal impressive ion-pair binding affinities towards a variety of ammonium halide, nitrate and thiocyanate salts, with the heteroditopic receptor displaying notable ammonium halide salt selectivity. The prodigious solution phase NH4X recognition also translates to efficient solid-liquid and liquid-liquid extraction capabilities.

Remarkably selective NH4+ binding and fluorescence sensing by tripodal tris(pyrazolyl) receptors derived from 1,3,5-triethylbenzene: structural and theoretical insights on the role of ion pairing

Differences in pyrazole substitution result in dramatic changes in NH₄⁺ binding and fluorescence sensing, due to ion pairing and solvation effects.

σ-Hole⋯π and lone pair⋯π interactions in benzylic halides

Depending on the relative orientation of the halogen atom and the phenyl ring, the benzylic halides studied show “classical” halogen⋯π bonds as well as intramolecular interactions without σ-hole participation based on n → π* (LP⋯π) interactions.