Ursula Kisiel - University of Windsor

Placement: University of Victoria
Supervisor: Dr. Cornelia Bohne

Complexation Dynamics of Pyrene with Cyclodextrins

The focus of my project is to study the complexation dynamics of guest molecules within cylcodextrins (CD’s). Utilization of pyrene as a guest/probe is frequent since the shape and intensity of its fluorescence spectra are extremely sensitive to the polarity of the microenvironment. Thus, most of my experiments center around pyrene and its interaction with cyclodextrins. The 1:1 pyrene:CD complex is formed readily, however, our main interest lies in the study of the effect of excimer formation (2:2 complex) on the overall kinetics of complex formation and dissociation.

The supramolecular chemistry between pyrene and g-CD’s is studied with the help of a fluorimeter and a stopped flow apparatus. The former allows us to see the slow kinetics (slower than 20 s), whereas the latter permits the study of complexation on a microsecond time scale. The data gathered from the instruments is fitted via Kaleidagraph (software v.3.0) to yield equilibrium constants and entry/exit rate constants. We have shown that the binding dynamics for the complex with 2:2 stoichiometry is not straightforward and occurs on time scales slower than milliseconds. This time scale is at least one hundred times slower than previously observed for the complexation dynamics of various compounds in guest:CD stoichiometries of 1:1.