Thermodynamic aspects of dicarboxylate recognition by simple artificial receptors

B. R. Linton, M. Scott Goodman, E. Fan, S. A. Van Arman, Andrew Hamilton

Research output: Contribution to journalArticle

Abstract

Recognition of dicarboxylates by bis-functional hydrogen-bonding receptors displays divergent thermodynamics in different solvent systems. NMR titration and isothermal titration calorimetry indicated that neutral bis-urea and bis-thiourea receptors form exothermic complexes with dicarboxylates in DMSO, with a near zero entropic contribution to binding. The increased binding strength of bis-guanidinium receptors precluded quantitative measurement of binding constants in DMSO, but titration calorimetry offered a qualitative picture of the association. Formation of these 1:1 complexes was also exothermic, but additional endothermic events occurred at both lower and higher host-guest ratios. These events indicated multiple binding equilibria but did not always occur at a discrete 2:1 or 1:2 host-guest molar ratio, suggesting higher aggregates. With increasing amounts of methanol as solvent, bis-guanidinium receptors form more endothermic complexes with dicarboxylates, with a favorable entropy of association. This switch from association driven by enthalpy to one driven by entropy may reflect a change from complexation involving the formation of hydrogen bonds to that promoted by solvent liberation from binding sites.

Original languageEnglish (US)
Pages (from-to)7313-7319
Number of pages7
JournalJournal of Organic Chemistry
Volume66
Issue number22
DOIs
StatePublished - Nov 2 2001

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Artificial Receptors
Titration
Guanidine
Association reactions
Thermodynamics
Calorimetry
Dimethyl Sulfoxide
Hydrogen bonds
Entropy
Thiourea
Complexation
Methanol
Urea
Enthalpy
Binding Sites
Switches
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Thermodynamic aspects of dicarboxylate recognition by simple artificial receptors. / Linton, B. R.; Scott Goodman, M.; Fan, E.; Van Arman, S. A.; Hamilton, Andrew.

In: Journal of Organic Chemistry, Vol. 66, No. 22, 02.11.2001, p. 7313-7319.

Research output: Contribution to journalArticle

Linton, B. R. ; Scott Goodman, M. ; Fan, E. ; Van Arman, S. A. ; Hamilton, Andrew. / Thermodynamic aspects of dicarboxylate recognition by simple artificial receptors. In: Journal of Organic Chemistry. 2001 ; Vol. 66, No. 22. pp. 7313-7319.
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