Cis- and trans-strapped calix[4]pyrroles bearing phthalamide linkers: synthesis and anion-binding properties.
[reaction: see text] New cis-strapped calix[4]pyrrole derivatives 12, 13, and 19 and trans-strapped systems 14 and 15 bearing isophthalate-derived diamide spacers linked to the tetrapyrrolic core have been synthesized and characterized by spectroscopic means. The anion-binding behavior of these receptors was investigated by proton NMR spectroscopy and isothermal titration calorimetry (ITC). A 2:1 binding stoichiometry was observed under the conditions of NMR analysis but not at the lower concentration regime used for ITC. As gauged from both sets of analyses, these new strapped systems display affinities for halide anions that are enhanced compared to those of normal, unstrapped calix[4]pyrrole. However, contrary to expectations, no size-dependent selectivity for anions is observed as the length of the bridging strap is varied. Such results are interpreted in terms of anion-binding processes that occur outside the central pocket defined by the strap but that still favor strong associations as the result of the increased number of hydrogen-bonding donors the amide groups provide.
Lee
Chang-Hee
CH
Department of Chemistry and Institute of Basic Science, Kangwon National University, Chun-Chon 200-701 Korea. chhlee@kangwon.ac.kr
Lee
Jin-Suk
JS
Na
Hee-Kyung
HK
Yoon
Dae-Wi
DW
Miyaji
Hidekazu
H
Cho
Won-Seob
WS
Sessler
Jonathan L
JL
D000838:Anions / Q000737:chemistry; D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D006219:Halogens / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D010797:Phthalimides / Q000737:chemistry*; D011166:Porphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000838:Anions; D006219:Halogens; D010797:Phthalimides; D011166:Porphyrins; C469811:calix(4)pyrrole; D047250:Calixarenes