2,3-Ethylene-bridged dihomooxacalix[4]arenes: synthesis, X-ray crystal structures and highly selective binding properties with anions†
Jing Sun,Chao-Guo Yan
New Journal of Chemistry Pub Date : 05/09/2018 00:00:00 , DOI:10.1039/C8NJ01284A
Abstract

Three novel 2,3-ethylene-bridged p-tert-butyldihomooxacalix[4]arenes 3a–3c were selectively synthesized by direct O-alkylation of p-tert-butyldihomooxacalix[4]arene 1 with excess of 1,2-dibromoethane in controlled basic systems. Their corresponding conformational features were clearly elucidated by 1H NMR spectra and single crystal structures. Their binding abilities toward a variety of anions (SO42−, SO32−, CO32−, HSO3, HCO3, NO3, CH3COO, Br, I and Cl) have been assessed (3a was taken for example) and compared to those afforded with the unconstrained p-tert-butyldihomooxacalix[4]arene 1 and the analogous 1,3-di-(2-bromoethyl) substituted calix[4]arene derivative 4 by determining the fluorescence titrations. The results showed that 2,3-ethylene-bridged dihomooxacalix[4]arene 3a has the most significant selectivity and high affinity for I. In contrast, p-tert-butyldihomooxacalix[4]arene 1 can mainly bind most anions (SO32−, CO32−, HCO3, NO3, and I), but has a poor selectivity preference. The analogous 4 exhibits only a weak binding ability for I, which suggests that 2,3-ethylene-bridged p-tert-butyl-dihomooxacalix[4]arene 3a would be useful in the design of new selective supramolecular receptors for anions.

Graphical abstract: 2,3-Ethylene-bridged dihomooxacalix[4]arenes: synthesis, X-ray crystal structures and highly selective binding properties with anions