Understanding the driving force for the molecular recognition of S6-corona[3]arene[3]pyridazine toward organic ammonium cations

• Published in: Organic chemistry frontiers an international journal of organic chemistry 2018, Vol.5 (5), p.760-764
• Main Authors: Meng-Yao, Zhao, Qing-Hui Guo, Mei-Xiang, Wang
• Format: Article
• Language: English
• Subjects: Ammonium; Cations; Chemical bonds; Crystallography; Dichloroethane; Enthalpy; Entropy; Hydrogen bonding; Hydrogen bonds; Magnetic resonance spectroscopy; Mass spectrometry; Mass spectroscopy; NMR spectroscopy; Organic chemistry; Pyridazines; Recognition; Titration; X-ray crystallography
• ISSN: 2052-4110; 2052-4110
• DOI: 10.1039/c7qo00900c

The molecular recognition of S6-corona[3]arene[3]pyridazine toward various N-alkyl ammonium cations was systematically studied by means of ITC titration, NMR spectroscopy, mass spectrometry and X-ray crystallography. As a powerful and selective macrocyclic host molecule, S6-corona[3]arene[3]pyridazine was able to form dominantly 1 : 1 complexes with cations in a mixture of CH3CN and 1,2-dichloroethane (v : v = 1 : 1) giving association constants in the range of (1.08 ± 0.01) × 103 M−1 to (1.48 ± 0.11) × 105 M−1. In all cases, the favorable host–guest complexation processes were driven by the combination of beneficial enthalpy and entropy effects. While the enthalpy effect was attributable to the multiple non-covalent bond attractions such as lpe/π, π/π and nonconventional hydrogen bonds between host and guest, the entropy increase was most likely due to the desolvation of the guests.