The Synergetic Interplay of Weak Interactions in the Ion-Pair Recognition of Quaternary and Diquaternary Ammonium Salts by Halogenated Resorcinarenes

• Published in: European journal of organic chemistry Vol. 2014; no. 1; pp. 80 - 85
• Main Authors: Kodiah Beyeh, N., Göth, Melanie, Kaufmann, Lena, Schalley, Christoph A., Rissanen, Kari
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2014; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemical bonds; Chemistry; Chemistry, Organic; Host-guest systems; Ion pairs; Mass spectrometry; NMR spectroscopy; Physical Sciences; Resorcinarenes; Science & Technology; PYROGALLARENE; TETRAMETHYLAMMONIUM; CAPSULES; Ion pairs; COMPLEXES; SUPRAMOLECULAR CHEMISTRY; Resorcinarenes; Host-guest systems; HOST-GUEST CHEMISTRY; MOLECULAR RECOGNITION; GAS-PHASE; NMR spectroscopy; RECEPTORS; Mass spectrometry; BINDING
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201300886

The influence of halogens on the noncovalent interactions of different upper‐rim‐substituted hexylresorcinarenes with quaternary and diquaternary ammonium iodide salts was investigated in the gas phase by electrospray ionization Fourier‐transform ion‐cyclotron‐resonance (ESI‐FTICR) mass spectrometry and in solution by 1H NMR titration studies. The electronic nature of the substituents on the upper rim of the resorcinarene was directly reflected in the order of binding strengths of the hosts towards quaternary and diquaternary ammonium cations in the gas phase. In solution, the opposite trend was observed, with generally higher binding constants for the diquaternary over the quaternary salts. This phenomenon is explained by the synergetic effect originating from the interaction of the halogenated resorcinarenes with the counteranions through enhanced hydrogen bonding, leading to ion‐pair binding in solution. The electronegativity of the halogens renders the hydrogen of the hydroxy group more acidic, and hence enforces hydrogen bonding in solution. The collective effect of several weak interactions is manifested in solution, thereby emphasizing the benefits of comparing solution and gas‐phase studies in recognition processes. The noncovalent interactions of upper‐rim halogenated resorcinarenes with quaternary and diquaternary ammonium salts were analysed in the gas phase and in solution. Enhanced ion pair binding by a synergetic combination of cation···π and hydrogen‐bond interactions was observed in solution, while the electronic effects of the substituents prevailed in the gas phase in the absence of the counteranion.