Substituent Effects in Parallel-Displaced π-π Stacking Interactions: Distance Matters.
Angew Chem Int Ed Engl
; 56(37): 11252-11257, 2017 09 04.
Article
em En
| MEDLINE
| ID: mdl-28493621
ABSTRACT
Host-guest systems with Rebek imide type receptors and a 2,6-di(isobutyramido)pyridine ligand were employed to investigate substituent effects in parallel-displaced π-π stacking interactions. Changing the intermolecular distance between the paraâ
substituent on the aromatic platform of the receptor and the pyridine ring of the guest results in a strongly different substituent effect. With a short ethyne-1,2-diyl spacer between the Rebek imide and the aromatic platform, partial overlap of substituent and guest stabilizes the π-π stacking interactions independent of the electronic nature of the substituent (Wheeler-Houk model). When the substituent is shifted further away by using a buta-1,3-diyne-1,4-diyl spacer, direct, through-space interactions between substituent and guest are prevented. A linear correlation between logKa (Ka =association constant) and the Hammett substituent constant σpara is observed, confirming predictions by the Hunter-Sanders model experimentally.
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Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article