title: Very Strong Binding for a Neutral Calix[4]pyrrole Receptor Displaying Positive Allosteric Binding.
abstract: The dual-analyte responsive behavior of tetraTTF-calix[4]pyrrole receptor 1 has been shown to complex electron-deficient planar guests in a 2:1 fashion by adopting a so-called 1,3-alternate conformation. However, stronger 1:1 complexes have been demonstrated with tetraalkylammonium halide salts that defer receptor 1 to its cone conformation. Herein, we report the complexation of an electron-deficient planar guest, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA, 2) that champions the complexation with 1, resulting in a high association constant Ka= 3 × 1010M-2. The tetrathiafulvalene (TTF) subunits in the tetraTTF-calix[4]pyrrole receptor 1 present a near 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. Moreover, the complexation of these species results in the formation of a charge transfer complex (22⊂1) as visualized by a readily apparent color change from yellow to brown.
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Troels
authors.initials: T
authors.lastname: Duedal
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Kent A
authors.initials: KA
authors.lastname: Nielsen
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Gunnar
authors.identifier: 0000-0003-2254-3543
authors.initials: G
authors.lastname: Olsen
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Charlotte B G
authors.initials: CB
authors.lastname: Rasmussen
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Kongsted
authors.affiliation: MOLTECH Anjou - UMR 6200 du CNRS, Université d'Angers , 2 Bd Lavoisier, Angers F-49045 Cedex, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Levillain
authors.affiliation: MOLTECH Anjou - UMR 6200 du CNRS, Université d'Angers , 2 Bd Lavoisier, Angers F-49045 Cedex, France.
authors.forename: Tony
authors.initials: T
authors.lastname: Breton
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University , Higashi-Hiroshima 739-8527, Japan.
authors.forename: Eigo
authors.initials: E
authors.lastname: Miyazaki
authors.affiliation: Emergent Molecular Function Research Group, RIKEN Center for Emergent Matter Science (CEMS) , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Kazuo
authors.identifier: 0000-0002-6001-1129
authors.initials: K
authors.lastname: Takimiya
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Steffen
authors.identifier: 0000-0001-5113-2458
authors.initials: S
authors.lastname: Bähring
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, Odense M DK-5230, Denmark.
authors.forename: Jan O
authors.identifier: 0000-0002-3088-2994
authors.initials: JO
authors.lastname: Jeppesen