The creation of dynamic compartmentalization has potential ramifications throughout chemistry. This program of research focuses on concave hosts that assemble around guest molecules to form dynamic, nano-capsules. Driven by the hydrophobic effect, the formation of these containers engenders a dry, inner-space quite distinct from the external aqueous environment. Synthesis plays a key part in this work. The hosts – deep-cavity cavitands – must be designed carefully so that they are able to dissolve in water at the required pH, bind the requisite guests, and affect them in the desired manner. Characterization of the cavitands and their assemblies requires an array of Nuclear Magnetic Resonance (NMR) spectroscopic techniques, including: 1H/13C, NOESY, COSY, EXSY, and PGSE/DOSY experiments.
The engendering of compartmentalization can lead to many unusual and unique phenomena. For example, the compartments can be used as yoctoliter (10-24 L) reaction vessels to carry out processes that cannot normally be performed in water. Being of exceedingly small volume, the contents of these vessels are at high concentration (M range). Additionally, the nature of the solubilizing groups on the outer surface of the hosts controls the net electrostatic potential within the nano-space. These points, combined with the constant, intimate contacts with the walls of the capsule lead to precise and unusual reactivity of encapsulated guests.
Compartmentalization can also lead to physical and kinetic separation technologies. An example of the former is the passing of a mixture of hydrocarbon gases over a solution of a host; whichever guest forms the most stable capsular complex is selectively sequestered into the aqueous solution from the gas phase. Regarding kinetic resolutions, if a mixture to be separated is placed in a reactive medium along with a host, then it is the most strongly bound guest that is encapsulated within the dry nano-space and hence protected from the reactive medium. Thus, the host capsule adds a protection bias to any intrinsic difference in the reaction rates of the guests.