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Published August 17, 2016 | Accepted Version + Supplemental Material
Journal Article Open

Sliding-Ring Catenanes


Template-directed protocols provide a routine approach to the synthesis of mechanically interlocked molecules (MIMs), in which the mechanical bonds are stabilized by a wide variety of weak interactions. In this paper, we describe a strategy for the preparation of neutral [2]catenanes with sliding interlocked electron-rich rings, starting from two degenerate donor-acceptor [2]catenanes, consisting of a tetracationic cyclobis(paraquat-p-phenylene) cyclophane (CBPQT4+) and crown ethers containing either (i) hydroquinone (HQ) or (ii) 1,5-dioxynaphthalene (DNP) recognition units and carrying out four-electron reductions of the cyclophane components to their neutral forms. The donor-acceptor interactions between the CBPQT4+ ring and both HQ and DNP units present in the crown ethers that stabilize the [2]catenanes are weakened upon reduction of the cyclophane components to their radical cationic states and are all but absent in their fully reduced states. Characterization in solution performed by UV-Vis, EPR and NMR spectroscopic probes reveals that changes in the redox properties of the [2]catenanes result in a substantial decrease of the energy barriers for the circumrotation and pirouetting motions of the interlocked rings, which glide freely through one another in the neutral states. The solid-state structures of the fully reduced catenanes reveal profound changes in the relative dispositions of the interlocked rings, with the glycol chains of the crown ethers residing in the cavities of the neutral CBPQT0 rings. Quantum mechanical investigations of the energy levels associated with the four different oxidation states of the catenanes support this interpretation. Catenanes and rotaxanes with sliding rings are expected to display unique properties.

Additional Information

© 2016 American Chemical Society. Received 14 May 2016. Published online 11 July 2016. We thank Dr. Amy Sarjeant and Charlotte C. Stern for solving the single-crystal X-ray structures. This research is part of the Joint Center of Excellence in Integrated Nano-Systems (JCIN) at King Abdulaziz City for Science and Technology (KACST) and Northwestern University (NU). The authors would like to thank both KACST and NU for their continued support of this research. This work was also supported by the US National Science Foundation (NSF) under grant no. CHE-1565925 (M.R.W.). W.A.G. gratefully acknowledges support (EFRI-1332411) from the NSF. Y.W. thanks the Fulbright Scholar Program for a Research Fellowship and gratefully acknowledges support from a Ryan Fellowship awarded by the NU International Institute of Nanotechnology (IIN).

Attached Files

Accepted Version - Sliding_Ring_Catenane_ja-2016-04982eR1.pdf

Supplemental Material - ja6b04982_si_001.pdf

Supplemental Material - ja6b04982_si_002.cif

Supplemental Material - ja6b04982_si_003.cif

Supplemental Material - ja6b04982_si_004.cif

Supplemental Material - ja6b04982_si_005.cif


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August 20, 2023
October 20, 2023