Elucidating the roles of enthalpy, entropy, and donor atom in the chelate effect for binding different bidentate ligands on the same metal center

Eric G. Moschetta, Kristina M. Gans, Robert M. Rioux

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We present a thermodynamic study of the chelate effect for a series of P-P, N-N, and P-N bidentate ligands binding to PdCl2(MeCN)2 in acetonitrile (MeCN), using isothermal titration calorimetry (ITC) to measure the solution-phase binding thermodynamics. The chelate effect is considered to be an entropic effect, that is, the enthalpic contributions attributed to binding for comparable monodentate and bidentate ligands are nearly identical, meaning that changes in ΔG are due to favorable changes in ΔS upon displacement of bound solvent molecules. However, our results demonstrate that enhanced enthalpic contributions (i.e. large and exothermic) control the stability of the chelated complexes and generally are accompanied by large entropic penalties. We discuss the contribution of solvent reorganization and its role in enthalpy-entropy compensation for the binding equilibria studied.

Original languageEnglish (US)
Pages (from-to)11-20
Number of pages10
JournalJournal of Catalysis
Volume309
DOIs
StatePublished - Jan 1 2014

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chelates
Enthalpy
Entropy
enthalpy
Metals
Ligands
Thermodynamics
entropy
Atoms
ligands
Calorimetry
Acetonitrile
Titration
metals
atoms
thermodynamics
Molecules
penalties
titration
acetonitrile

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

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title = "Elucidating the roles of enthalpy, entropy, and donor atom in the chelate effect for binding different bidentate ligands on the same metal center",
abstract = "We present a thermodynamic study of the chelate effect for a series of P-P, N-N, and P-N bidentate ligands binding to PdCl2(MeCN)2 in acetonitrile (MeCN), using isothermal titration calorimetry (ITC) to measure the solution-phase binding thermodynamics. The chelate effect is considered to be an entropic effect, that is, the enthalpic contributions attributed to binding for comparable monodentate and bidentate ligands are nearly identical, meaning that changes in ΔG are due to favorable changes in ΔS upon displacement of bound solvent molecules. However, our results demonstrate that enhanced enthalpic contributions (i.e. large and exothermic) control the stability of the chelated complexes and generally are accompanied by large entropic penalties. We discuss the contribution of solvent reorganization and its role in enthalpy-entropy compensation for the binding equilibria studied.",
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Elucidating the roles of enthalpy, entropy, and donor atom in the chelate effect for binding different bidentate ligands on the same metal center. / Moschetta, Eric G.; Gans, Kristina M.; Rioux, Robert M.

In: Journal of Catalysis, Vol. 309, 01.01.2014, p. 11-20.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Elucidating the roles of enthalpy, entropy, and donor atom in the chelate effect for binding different bidentate ligands on the same metal center

AU - Moschetta, Eric G.

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AU - Rioux, Robert M.

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N2 - We present a thermodynamic study of the chelate effect for a series of P-P, N-N, and P-N bidentate ligands binding to PdCl2(MeCN)2 in acetonitrile (MeCN), using isothermal titration calorimetry (ITC) to measure the solution-phase binding thermodynamics. The chelate effect is considered to be an entropic effect, that is, the enthalpic contributions attributed to binding for comparable monodentate and bidentate ligands are nearly identical, meaning that changes in ΔG are due to favorable changes in ΔS upon displacement of bound solvent molecules. However, our results demonstrate that enhanced enthalpic contributions (i.e. large and exothermic) control the stability of the chelated complexes and generally are accompanied by large entropic penalties. We discuss the contribution of solvent reorganization and its role in enthalpy-entropy compensation for the binding equilibria studied.

AB - We present a thermodynamic study of the chelate effect for a series of P-P, N-N, and P-N bidentate ligands binding to PdCl2(MeCN)2 in acetonitrile (MeCN), using isothermal titration calorimetry (ITC) to measure the solution-phase binding thermodynamics. The chelate effect is considered to be an entropic effect, that is, the enthalpic contributions attributed to binding for comparable monodentate and bidentate ligands are nearly identical, meaning that changes in ΔG are due to favorable changes in ΔS upon displacement of bound solvent molecules. However, our results demonstrate that enhanced enthalpic contributions (i.e. large and exothermic) control the stability of the chelated complexes and generally are accompanied by large entropic penalties. We discuss the contribution of solvent reorganization and its role in enthalpy-entropy compensation for the binding equilibria studied.

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