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oai:recercat.cat:2072/3058172026-01-15T14:12:34Zcom_2072_300912com_2072_4427col_2072_301309

RECERCAT author Aragay, Gemma author Hernández, Daniel author Verdejo, Begoña author Escudero-Adán, Eduardo C. author Martínez, Marta author Ballester, Pablo 2018-01-15T16:04:40Z2018-02-15T10:28:07Z2024-04-23T10:30:00Z 2018-01-15T16:04:40Z2018-02-15T10:28:07Z2024-04-23T10:30:00Z 2015 http://hdl.handle.net/2072/305817 https://doi.org/10.3390/molecules200916672 <p> We describe the use of two series of aryl-extended calix[4]pyrrole receptors bearing two and four electronically tunable phenyl groups, respectively, in their meso-positions as model systems for the quantification of CH-pi interactions in solution. The "four-wall" and the "two-wall" receptors formed thermodynamically stable 1:1 complexes in acetonitrile solution with both trimethylamine N-oxide and trimethylphosphine P-oxide as guests. The complexes were mainly stabilized by the formation of four convergent hydrogen bonds between the oxygen atom of the guests and the pyrrole NHs of the host. In general, the N-oxide produced thermodynamically more stable hydrogen bonding interactions than the P-oxide. Upon guest binding, the receptors adopted the cone conformation and the methyl groups of the included guests engaged in CH-pi interactions with the aromatic walls. We show that the modification of the electronic properties of the aromatic surfaces, in any of the receptor series, did not have a significant impact in the measured binding affinities for a given guest. However, the larger binding affinities determined for the "four-wall" receptors in comparison to the "two-wall" counterparts supported the importance of CH-pi interactions on guest complexation. The strength of the CH-pi interactions present in the inclusion complexes was quantified employing the octamethyl calix[4]pyrrole as reference. We determined an average magnitude of similar to 1 kcal.mol(-1) for each CH-pi interaction. The CH-pi interactions featured a reduced electrostatic nature and thus dispersion forces were assigned as main contributors of their strength.</p> eng © MDPI Quantification of CH-pi Interactions Using Calix[4]pyrrole Receptors as Model Systems info:eu-repo/semantics/article URL https://recercat.cat/bitstream/2072/305817/2/molecules-20-16672.pdf File MD5 24b1e2d83e90efb26489b57353c28809 1977656 application/pdf molecules-20-16672.pdf URL https://recercat.cat/bitstream/2072/305817/1/molecules-20-16672.pdf.txt File MD5 087ceb22887a0bdd5df40dabc780145d 45555 text/plain molecules-20-16672.pdf.txt