Thiacalixarene derivatives bearing imidazole units: a ditopic hard/soft receptor for Na+ and K+/Ag+ with an allosteric effect and a reusable extractant for dichromate anions
journal contributionposted on 22.06.2016 by Jiang-Lin Zhao, Chong Wu, Xi Zeng, Shofiur Rahman, P.E. Georghiou, Mark Elsegood, Thomas G. Warwick, Carl Redshaw, Simon J. Teat, Takehiko Yamato
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Two novel receptors 5,11,17,23-tetra-tert-butyl-25,27-bis[(ethoxycarbonyl)methoxy]-26,28-bis-[1-methyl-(imidazole)meth-oxy]-2,8,14,20-tetra-thiacalixarene (L1) and 5,11,17,23-tetra-tert-butyl-25,27-bis-[(benzyl)methoxy]-26,28-bis-[1-methyl-(imidazole)-methoxy]-2,8,14,20-tetrathiacalixarene (L2) possessing imidazole moieties based on thiacalixarene in the 1,3-alternate conformation have been synthesized and characterized. The crystal structures of L1 and L2 have been determined. The binding behaviour towards Li+, Na+, K+ and Ag+ ions has been examined by 1H NMR titration experiments in (CDCl3/CD3CN; 10:1, v/v) solution. The exclusive formation of mononuclear complexes of L1 with metal cations is of particular interest revealing a negative allosteric effect in the thiacalixarene family. Liquid-liquid extraction experiments indicate that synthesized L2 can be utilized as an efficient reusable extractant for dichromate anion by controlling the pH of the aqueous solution.
We would like to thank the OTEC at SagaUniversity and the International Cooperation Projects of Guiz-hou P rovince (N o. 20137005) for financial support. The EPSRC isthanked for a travel grant (to CR).