Tetra-TTF calix[4]pyrrole: a rationally designed receptor for electron-deficient neutral guests.
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.
Nielsen
Kent A
KA
Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, 1 University Station-A5300, Texas 78712-0165, USA.
Cho
Won-Seob
WS
Jeppesen
Jan O
JO
Lynch
Vincent M
VM
Becher
Jan
J
Sessler
Jonathan L
JL