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Kinetic and Thermodynamic Approaches for the Efficient Formation of Mechanical Bonds

Dichtel, William R. and Miljanić, Ognjen Š. and Zhang, Wenyu and Spruell, Jason M. and Patel, Kaushik and Aprahamian, Ivan and Heath, James R. and Stoddart, J. Fraser (2008) Kinetic and Thermodynamic Approaches for the Efficient Formation of Mechanical Bonds. Accounts of Chemical Research, 41 (12, Sp). pp. 1750-1761. ISSN 0001-4842. doi:10.1021/ar800067h.

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Among the growing collection of molecular systems under consideration for nanoscale device applications, mechanically interlocked compounds derived from electrochemically switchable bistable [2]rotaxanes and [2]catenanes show great promise. These systems demonstrate dynamic, relative movements between their components, such as shuttling and circumrotation, enabling them to serve as stimuli-responsive switches operated via reversible, electrochemical oxidation−reduction rather than through the addition of chemical reagents. Investigations into these systems have been intense for a number of years, yet limitations associated with their synthesis have hindered incorporation of their mechanical bonds into more complex architectures and functional materials. We have recently addressed this challenge by developing new template-directed synthetic protocols, operating under both kinetic and thermodynamic control, for the preparation of bistable rotaxanes and catenanes. These methodologies are compatible with the molecular recognition between the π-electron-accepting cyclobis(paraquat-p-phenylene) (CBPQT4+) host and complementary π-electron-donating guests. The procedures that operate under kinetic control rely on mild chemical transformations to attach bulky stoppering groups or perform macrocyclizations without disrupting the host−guest binding of the rotaxane or catenane precursors. Alternatively, the protocols that operate under thermodynamic control utilize a reversible ring-opening reaction of the CBPQT4+ ring, providing a pathway for two cyclic starting materials to thread one another to form more thermodynamically stable catenaned products. These complementary pathways generate bistable rotaxanes and catenanes in high yields, simplify mechanical bond formation in these systems, and eliminate the requirement that the mechanical bonds be introduced into the molecular structure in the final step of the synthesis. These new methods have already been put into practice to prepare previously unavailable rotaxane architectures and novel complex materials. Furthermore, the potential for utilizing mechanically interlocked architectures as device components capable of information storage, the delivery of therapeutic agents, or other desirable functions has increased significantly as a result of the development of these improved synthetic protocols.

Item Type:Article
Related URLs:
URLURL TypeDescription
Dichtel, William R.0000-0002-3635-6119
Miljanić, Ognjen Š.0000-0002-7876-9034
Heath, James R.0000-0001-5356-4385
Stoddart, J. Fraser0000-0003-3161-3697
Additional Information:© 2008 American Chemical Society. Received on March 3, 2008. Publication Date (Web): October 7, 2008. The collaboration was supported by the Semiconductor Research Corporation (SRC) and its Focus Centers on Functional Engineered Nanoarchitectonics (FENA) and Materials Structures and Devices (MSD), the Moletronics Program of the Defense Advanced Research Projects Agency (DARPA), and the Center for Nanoscale Innovation for Defense (CNID). J.M.S. gratefully acknowledges the National Science Foundation (NSF) for a Graduate Research Fellowship.
Funding AgencyGrant Number
Semiconductor Research CorporationUNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:12, Sp
Record Number:CaltechAUTHORS:DICacc08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12959
Deposited By: Archive Administrator
Deposited On:11 Jan 2009 03:00
Last Modified:08 Nov 2021 22:34

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