Title

Thermodynamic Contribution of Water in Cryptophane Host-Guest Binding Reaction

Publication Date

7-30-2020

Document Type

Article

Department

Chemistry

Publication Title

Journal of Physical Chemistry B

Volume

124

Issue

30

DOI

10.1021/acs.jpcb.0c05354

First Page

6585

Last Page

6591

Abstract

A detailed examination of binding thermodynamics is undertaken for the interaction between rubidium ion and a water-soluble cryptophane molecule using isothermal titration calorimetry. The equilibrium-binding quotient for this host-guest pair decreases with increasing product formation. When analyzed with a thermodynamic framework that considers water explicitly in the governing equation, the shift in equilibrium is ascribed to an unfavorable change in the free energy of solvation upon formation of the inclusion complex. A van't Hoff analysis of the binding data, as well as an observation of aggregation between inclusion complexes, suggests that charge-charge interactions between rubidium ion and the phenolate groups of the cryptophane host provide the driving force for association in water that overcomes a large and unfavorable change in solvent enthalpy.

Funding Number

R15GM110654

Funding Sponsor

National Institutes of Health

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