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

New Journal of Chemistry Pub Date: 2019-03-20 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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