Very Strong Binding for a Neutral Calix[4]pyrrole Receptor Displaying Positive Allosteric Binding

Troels Duedal, Kent Nielsen, Gunnar Olsen, Charlotte Burgdorf Guldager Rasmussen, Jacob Kongsted, Eric Levillain, Tony Breton, Eigo Miyazaki, Kazuo Takimiya, Steffen Bähring, Jan Oskar Jeppesen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The dual-analyte responsive behavior of tetraTTF-calix[4]pyrrole receptor 1 has shown to complex electron-deficient planar guests in a 2:1 fashion in the so-called 1,3-alternate conformation. However, stronger 1:1 complexes have been demonstrated with tetraalkylammonium halide salts that defer receptor 1 to its so-called cone conformation. Herein, we report the complexation of an electron-deficient planar guest, namely 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA, 2), that champions the complexation with 1 resulting in a very high association constant Ka = 3 × 1010 M−2. The tetrathiafulvalene (TTF) subunits in the tetraTTF-calix[4]pyrrole receptor 1 present a nearly perfect shape and electronic complementarity to the NTCDA guest, which was confirmed by X-ray crystal structure analysis, DFT calculations, and electron density surface mapping. The complexation results in formation of a charge transfer complex (22⊆1), that is visualized as a color change from yellow to brown.
Original languageEnglish
JournalJournal of Organic Chemistry
Volume82
Issue number4
Pages (from-to)2123–2128
ISSN0022-3263
DOIs
Publication statusPublished - 2017

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