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Multi-point interaction-based recognition of fluoride ions by tert-butyldihomooxacalix[4]arenes bearing phenolic hydroxyls and thiourea†
Ling-Ling Zhao,Xiao-Song Yang,Hui Chong,Yang Wang,Chao-Guo Yan
New Journal of Chemistry Pub Date : 03/20/2019 00:00:00 , DOI:10.1039/C8NJ06333H
Abstract

A series of p-tert-butyldihomooxacalix[4]arenes bearing phenolic hydroxyls and thiourea moieties were prepared to investigate their anion binding behavior. These compounds showed F binding according to 1H NMR titration experiments. Among them, dihomooxacalix[4]arenes bearing phenyl and benzyl thiourea (2a and 2b) showed multiple interactions with added F, including N–H⋯F, O–H⋯F hydrogen bonds and “through-space” C–H⋯F interactions between F and the attached aromatic segment of thiourea. A conformational change of the dihomooxacalix[4]arene cavity was observed as well and proved by theoretical calculations. The dihomooxacalix[4]arene bearing methyl thiourea (2c) also showed the formation of N–H⋯F, O–H⋯F hydrogen bonds, but less conformational change of the dihomooxacalix[4]arene cavity according to 1H NMR titration results. The bis-dihomooxacalix[4]arene (3) showed clear N–H⋯F hydrogen bond formation upon addition of F as characterized by 1H NMR spectroscopy.

Graphical abstract: Multi-point interaction-based recognition of fluoride ions by tert-butyldihomooxacalix[4]arenes bearing phenolic hydroxyls and thiourea
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