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.
AU - Gans, Kristina M.
AU - Rioux, Robert M.
N1 - Funding Information:
The work was supported by The Pennsylvania State University and The Penn State Institutes of Energy and Environment (PSIEE) through start-up funds and a 3M Non-Tenured Faculty Grant. K.G. acknowledges support from the NASA WISER program for undergraduate research.
PY - 2014
Y1 - 2014
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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U2 - 10.1016/j.jcat.2013.09.002
DO - 10.1016/j.jcat.2013.09.002
M3 - Article
AN - SCOPUS:84884699200
SN - 0021-9517
VL - 309
SP - 11
EP - 20
JO - Journal of Catalysis
JF - Journal of Catalysis
ER -