title: Super Aryl-Extended Calix[4]pyrroles: Synthesis, Binding Studies, and Attempts To Gain Water Solubility.
abstract: We describe the synthesis of unprecedented calix[4]pyrrole receptors featuring "super aryl extended" (SAE) cavities. We elaborated the aromatic cavity provided by the αααα-isomer of para-tetraiodo-meso-phenyl calix[4]pyrrole by installing ethynyl-aryl substituents at its upper rim. We report the binding properties of the prepared SAE-calix[4]pyrrole tetraester towards pyridyl-N-oxides. The binding data revealed the formation of thermodynamically and kinetically highly stable 1:1 complexes. The complexation-induced chemical shifts indicated the formation of hydrogen bonds and aromatic interactions with the calix-core adopting the cone conformation. We quantified the additional interactions established between the four terminal aryl groups and the para-phenyl substituent of 4-phenyl pyridine N-oxide to be in the order of 1 kcal mol(-1) . The complex formation rate was found to be close to the diffusion control suggesting that the free host adopted a 1,3-alternate conformation. Finally, we attempted to gain water solubility of SAE-calix[4]pyrroles using derivatives that display four ionizable or charged groups at their upper rims.
authors: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avgda. Països Catalans 16, 43007, Tarragona, Spain.
authors: Luis
authors: http://orcid.org/0000-0003-0392-8245
authors: L
authors: Escobar
authors: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avgda. Països Catalans 16, 43007, Tarragona, Spain.
authors: Gemma
authors: http://orcid.org/0000-0002-2405-0278
authors: G
authors: Aragay
authors: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Avgda. Països Catalans 16, 43007, Tarragona, Spain. pballester@iciq.es.|ICREA, Passeig Lluís Companys 23, 08018, Barcelona, Spain. pballester@iciq.es.
authors: Pablo
authors: http://orcid.org/0000-0001-8377-6610
authors: P
authors: Ballester
keywords: cross-coupling; kinetics; molecular recognition; noncovalent interactions; supramolecular chemistry