Fluorescence-based thermodynamic studies of the inclusion of anilinonaphthalene sulfonates by cyclodextrins

Fluorescence spectroscopy can be used to investigate the formation of host-guest inclusion complexes. Host-guest inclusion involves the noncovalent interactions between a host and a guest in which a guest molecule is small enough to enter the cavity of a macrocyclic host molecule. A thermodynamic study of the formation of an inclusion complex allows information to be obtained about the inclusion process, such as the enthalpy and entropy of inclusion. Such studies involve measuring the binding constant K at various temperatures. A pure and homogenous sample of a host molecule is required to perform an accurate thermodynamic analysis. This project involves the thermodynamic study of the inclusion of anilinonaphthalene sulfonates as guests with pure samples of cyclodextrin, with the goal of a full determination of the thermodynamics of these complexations, including the enthalpy and entropy of inclusion. A thermodynamic study of the inclusion of 2,6-ANS and 2,6-DM-β-CD was attempted but due to the unavailability of obtaining more of both the host and the guest, only three temperatures trials were performed. The study was then changed to the thermodynamic study of 2,6-TNS with α-cyclodextrin. After performing fluorescent titrations at seven temperatures, a van't Hoff plot was made and observed to be scattered. The higher temperatures seemed to follow a linear trend and was therefore investigated.