Cyclodextrin molecules have been used to create unique nanomaterials for a variety of applications, but there is much to learn about the behavior of guest molecules found within the cavity. The binding and overall stability of the guest molecule must be well-characterized in order to optimize these materials for use in practical supramolecular chemical systems. Brooker's merocyanine (4-[(1-methyl-4(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one) has an interesting protolytic/photolytic isomerization cycle that was found to be affected by encapsulation within the �-cyclodextrin cavity. The focus of this study was to understand this isomerization behavior within a series of modified cyclodextrins and to characterize the binding efficiency and thermodynamics of complex formation of these systems using UV/Vis and fluorescence spectroscopy. Modifications included different degrees of substitution at the primary and secondary rims of the cyclodextrin cavity with hydroxyethyl, hydroxypropyl, methyl, or sulfate substituents in order to compare the effect of hydrogen bonding, ionic interactions and steric effects on the host-guest structure. Results indicated that the largest effect on the complex behavior was from the ionic charges and/or steric effects of the sulfate group, while the various hydrocarbon modifications had a smaller effect on binding. In all cases, however, the formation of the complex was hindered as substituents were added to the cyclodextrin. Computational modeling was also used to compare the resulting host-guest structures at the molecular level to determine where Brooker's merocyanine was located within the cavity in order to rationalize the isomerization behavior. An understanding of the behavior of Brooker's merocyanine with a variety of cyclodextrin molecules can then be applied to other related guest molecules that must remain stable when used in host-guest applications such as in drug delivery nanomaterials, and an increase in the fundamental knowledge of these materials can be achieved.

Host-guest nanomaterials:  A comparison of Brooker's merocyanine interactions with modified �-cyclodextrins

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.