Cucurbit[n]urils (CB[n]s) are pumpkin shaped macrocycles that possess hydrophilic carbonyl rims and an inner hydrophobic cavity. Within their hydrophobic cavity, cucurbiturils can bind several types of organic compounds ranging from proteins to dyes. The larger cavity size of higher analogs of CB[n]s, such as CB[7] and CB[8], enables these analogs to bind bulky aromatic guests within their cavities, and in the case of CB[8], it is possible to encapsulate two guests within its cavity. Due to cucurbiturils ability to bind numerous types of guest molecules, they are used extensively as host in host-guest chemistry. This ability has resulted in the synthesis and study of several mechanically interlocked cucurbiturils. In our lab, we are interested in synthesizing mechanically, interlocked catenane⊂CB[n]s for applications in affinity chromatography. Although there are several mechanically interlocked cucurbiturils known to date, cucurbiturils with catenanes molecular architecture have not been studied extensively. Catenanes are dynamic structures thus the interlocked molecules within the catenane possess the ability to move location with respect to one another depending on their environment. For example, a simple change in pH may trigger the interlocked molecules to move. The first step in our synthesis of catenane⊂CB[n]s is the synthesis of a macromolecule from 1,2-bis(4-pyridyl)ethane. This was done by decorating the two ends of the pyridinyl groups with an azide terminated tether and a terminal alkyne tether, thereby setting the stage for a click reaction. In the next step, the macromolecule is complexed with CB[n] to form pseudorotaxane⊂CB[n]. Lastly the click reaction is performed to mechanically interlock the macromolecule and the CB[n], hence completing the synthesis of catenane⊂CB[n].
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