Spectroscopic Determination of the Binding Constant and Thermodynamic Values of a Host-Guest System
Jennifer S. Holt
Arts and Sciences
A host-guest system occurs when a guest molecule, in this case Brooker’s merocyanine (BM), enters the host molecule, beta-cyclodextrin (B-CD), to form a complex. The equilibrium of a host-guest system becomes established through weak intermolecular interactions when the guest molecule binds to the host. The strength of the interactions can be studied using the equilibrium binding constant. By altering the structure of the B-CD through modifications of the chemical substituents along the outer rims of the B-CD cavity, we can better understand the different types of interactions between host and guest, such as hydrogen bonding and van der Waals forces. The determination of the binding constant at different temperatures allows for further understanding of these complexes. To determine the binding constant, the Benesi-Hildebrand equation can be used to analyze data collected using fluorescence spectroscopy. The binding constant of B-CD complex does appear to be temperature dependent, so the thermodynamic values of ΔG, ΔH, and ΔS were calculated. However, the binding constants for some of the modified B-CD complexes do not appear to exhibit a strong temperature dependence, so these thermodynamic values were not determined. Determining the temperature dependence of these complexes allows better insight into how strong the modified B-CDs will bind to a guest molecule, which allows for better predictions of their behaviors under different conditions.
Patton, Erica C., "Spectroscopic Determination of the Binding Constant and Thermodynamic Values of a Host-Guest System" (2014). Symposium on Undergraduate Research and Creative Expression (SOURCE). 384.