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Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests

Hexahexyloxycalix[6]arene 2b leads to the endo-cavity complexation of linear and branched alkylammonium guests showing a conformational adaptive behavior in CDCl(3) solution. Linear n-pentylammonium guest 6a(+) induces the cone conformation of 2b at the expense of the 1,2,3-alternate, which is the m...

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Autores principales: Iuliano, Veronica, Talotta, Carmen, Della Sala, Paolo, De Rosa, Margherita, Soriente, Annunziata, Neri, Placido, Gaeta, Carmine
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10304928/
https://www.ncbi.nlm.nih.gov/pubmed/37375304
http://dx.doi.org/10.3390/molecules28124749
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author Iuliano, Veronica
Talotta, Carmen
Della Sala, Paolo
De Rosa, Margherita
Soriente, Annunziata
Neri, Placido
Gaeta, Carmine
author_facet Iuliano, Veronica
Talotta, Carmen
Della Sala, Paolo
De Rosa, Margherita
Soriente, Annunziata
Neri, Placido
Gaeta, Carmine
author_sort Iuliano, Veronica
collection PubMed
description Hexahexyloxycalix[6]arene 2b leads to the endo-cavity complexation of linear and branched alkylammonium guests showing a conformational adaptive behavior in CDCl(3) solution. Linear n-pentylammonium guest 6a(+) induces the cone conformation of 2b at the expense of the 1,2,3-alternate, which is the most abundant conformer of 2b in the absence of a guest. In a different way, branched alkylammonium guests, such as tert-butylammonium 6b(+) and isopropylammonium 6c(+), select the 1,2,3-alternate as the favored 2b conformation (6b(+)/6c(+)⊂2b(1,2,3-alt)), but other complexes in which 2b adopts different conformations, namely, 6b(+)/6c(+)⊂2b(cone), 6b(+)/6c(+)⊂2b(paco), and 6b(+)/6c(+)⊂2b(1,2-alt), have also been revealed. Binding constant values determined via NMR experiments indicated that the 1,2,3-alternate was the best-fitting 2b conformation for the complexation of branched alkylammonium guests, followed by cone > paco > 1,2-alt. Our NCI and NBO calculations suggest that the H-bonding interactions ((+)N–H···O) between the ammonium group of the guest and the oxygen atoms of calixarene 2b are the main determinants of the stability order of the four complexes. These interactions are weakened by increasing the guest steric encumbrance, thus leading to a lower binding affinity. Two stabilizing H-bonds are possible with the 1,2,3-alt- and cone-2b conformations, whereas only one H-bond is possible with the other paco- and 1,2-alt-2b stereoisomers.
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spelling pubmed-103049282023-06-29 Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests Iuliano, Veronica Talotta, Carmen Della Sala, Paolo De Rosa, Margherita Soriente, Annunziata Neri, Placido Gaeta, Carmine Molecules Article Hexahexyloxycalix[6]arene 2b leads to the endo-cavity complexation of linear and branched alkylammonium guests showing a conformational adaptive behavior in CDCl(3) solution. Linear n-pentylammonium guest 6a(+) induces the cone conformation of 2b at the expense of the 1,2,3-alternate, which is the most abundant conformer of 2b in the absence of a guest. In a different way, branched alkylammonium guests, such as tert-butylammonium 6b(+) and isopropylammonium 6c(+), select the 1,2,3-alternate as the favored 2b conformation (6b(+)/6c(+)⊂2b(1,2,3-alt)), but other complexes in which 2b adopts different conformations, namely, 6b(+)/6c(+)⊂2b(cone), 6b(+)/6c(+)⊂2b(paco), and 6b(+)/6c(+)⊂2b(1,2-alt), have also been revealed. Binding constant values determined via NMR experiments indicated that the 1,2,3-alternate was the best-fitting 2b conformation for the complexation of branched alkylammonium guests, followed by cone > paco > 1,2-alt. Our NCI and NBO calculations suggest that the H-bonding interactions ((+)N–H···O) between the ammonium group of the guest and the oxygen atoms of calixarene 2b are the main determinants of the stability order of the four complexes. These interactions are weakened by increasing the guest steric encumbrance, thus leading to a lower binding affinity. Two stabilizing H-bonds are possible with the 1,2,3-alt- and cone-2b conformations, whereas only one H-bond is possible with the other paco- and 1,2-alt-2b stereoisomers. MDPI 2023-06-13 /pmc/articles/PMC10304928/ /pubmed/37375304 http://dx.doi.org/10.3390/molecules28124749 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Iuliano, Veronica
Talotta, Carmen
Della Sala, Paolo
De Rosa, Margherita
Soriente, Annunziata
Neri, Placido
Gaeta, Carmine
Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title_full Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title_fullStr Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title_full_unstemmed Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title_short Hexahexyloxycalix[6]arene, a Conformationally Adaptive Host for the Complexation of Linear and Branched Alkylammonium Guests
title_sort hexahexyloxycalix[6]arene, a conformationally adaptive host for the complexation of linear and branched alkylammonium guests
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10304928/
https://www.ncbi.nlm.nih.gov/pubmed/37375304
http://dx.doi.org/10.3390/molecules28124749
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