Synthesis and Study of Dynamic Halogen Bonding [1]Rotaxanes for Anion Recognition and Sensing

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The current topic of my research project is the synthesis and study of dynamic halogen bonding [1]rotaxanes for anion recognition and sensing. This project falls within the EPSRC physical science research theme and synthetic supramolecular chemistry research area. As part of the Beer Research Group at the University of Oxford, I am working towards increasing the understanding of molecular recognition processes in biological systems in order to be able to produce new molecular sensors, switches and devices. The objectives of my research project are to construct molecular lasso-type [1]rotaxanes which upon anion recognition are designed to undergo extended and contracted translational dynamic shuttling behaviour. This involves the synthesis of novel compounds as well as using NMR, UV-visible, fluorescence and electrochemical techniques in order to study the interlocked structure and the dynamic shuttling behaviour upon anion recognition. A further objective is the modification of a [1]rotaxane in order to make it operational in water. Interlocked molecules are being studied as host systems for anion recognition due to their unique structures containing three dimensional cavities which can bind complementary anions with high affinity. Combining small molecule recognition with molecular motion further explores the exciting potential nanotechnological applications of such interlocked system as molecular machines. Anion sensors are of great interest due to the importance of anions in a range of biological processes, which opens up a whole new range of potential applications. Such applications would require the system to function in an aqueous environment. Part of the research project could therefore involve the modification of a [1]rotaxane in order for it to be soluble and stable in water. Halogen bonding is a type of intermolecular interaction that has been widely studied in solid state systems but is less understood for solution chemistry. However, electron rich anions are thought to have strong interactions with halogens and act as halogen-bonding acceptors. Using the anion as part of the halogen-bonding system could then allow it to template the formation of a [1]rotaxane. Halogen bonding has furthermore been successfully used in anion host systems, which are capable of operating in water. Despite the great interest in interlocked structures, examples of [1]rotaxanes are still rare especiallycompared to examples of [2]rotaxanes. A successful synthesis of a novel dynamic halogen bonding [1]rotaxane for anion recognition and sensing would therefore allow new insights into this class of interlocked structures and its potential applications.