Marie-Christine Nolet - University of Ottawa

Placement: University of Victoria
Supervisor: Dr. Cornelia Bohne

Complexation Dynamics of Naphthalene derivatives in Bile Salt Aggregates

Host-guest complexation provides many intriguing possible avenues for chemical research. The current study is investigating the complexation dynamics of a series of guest naphthalene (Np) probes within host bile salt aggregates (BsA). Bile salts are steroidal structures derived from a cholesterol base. The system is of interest as it has been shown to have more than one binding site for guest. At low bile salt concentration, primary aggregates are formed. The binding site within the primary aggregate is hydrophobic. It is also known that the structure of the guest is important for binding to occur and we have found the dissociation to be slow. At higher BsA concentration, further aggregation occurs and secondary aggregates are formed. Within these secondary aggregates, a second hydrophilic binding site is now available for guest molecules. There is no strict structural requirement for complexation and dissociation is fast. Probes can be complexed to either of the two sites. Preliminary work done with benzophenone has show the possibility of mobility between the primary and secondary aggregate. Thus the present work is focusing on a serie of Np derivatives in hope to further characterize the mobility within these aggregate systems. By creating a series of probes in which hydrophilicity varies, changes in the binding behavior of the probe to the host system can be characterized. We have shown that naphthalene itself as a probe complexes primarily to the primary site, thus by modifying it with polar substituents mobility characteristics are being investigated. The photophysics of complexation of both the singlet states (by fluorescence) and triplet state (by laser flash photolysis) studied through quenching methodology will also be presented. Understanding the structure of these aggregates, the dynamics of complexation and how mobility occurs will open many doors to further research.