title: Tetra-TTF calix[4]pyrrole: a rationally designed receptor for electron-deficient neutral guests.
abstract: A calix[4]pyrrole incorporating four appended tetrathiafulvalene (TTF) units has been synthesized, and its receptor abilities toward neutral electron-deficient guests, such as 1,3,5-trinitrobenzene, tetrafluoro-p-benzoquinone, and tetrachloro-p-benzoquinone, have been studied in solution by UV-vis and 1H NMR spectroscopies as well as in the solid-state by X-ray crystallography. In its 1,3-alternate conformation a 1:2 sandwich-like complex-stabilized by charge transfer and hydrogen bonding interactions-is formed between the tetra-TTF calix[4]pyrrole and the guest molecules. However, upon addition of chloride ions to the complex the 1,3-alternate conformation is changed in favor of a cone conformation which serves to effect a release of the guests from the tetra-TTF calix[4]pyrrole.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, 1 University Station-A5300, Texas 78712-0165, USA.
authors.forename: Kent A
authors.initials: KA
authors.lastname: Nielsen
authors.forename: Won-Seob
authors.initials: WS
authors.lastname: Cho
authors.forename: Jan O
authors.initials: JO
authors.lastname: Jeppesen
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Lynch
authors.forename: Jan
authors.initials: J
authors.lastname: Becher
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler