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Highly Stable Organic Bisradicals Protected by Mechanical Bonds

Cai, Kang and Mao, Haochuan and Liu, Wei-Guang and Qiu, Yunyan and Shi, Yi and Zhang, Long and Shen, Dengke and Chen, Hongliang and Jiao, Yang and Wu, Huang and Liu, Zhichang and Feng, Yuanning and Stern, Charlotte L. and Wasielewski, Michael R. and Goddard, William A., III and Stoddart, J. Fraser (2020) Highly Stable Organic Bisradicals Protected by Mechanical Bonds. Journal of the American Chemical Society, 142 (15). pp. 7190-7197. ISSN 0002-7863.

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Two new highly charged [2]catenanes—namely, mHe[2]C·6PF₆ and mHo[2]C·6PF₆—were synthesized by exploiting radical host–guest templation between derivatives containing BIPY•+ radical cations and the meta analogue of cyclobis(paraquat-p-phenylene). In contrast to related [2]catenanes that have been isolated as air-stable monoradicals, both mHe[2]C·6PF₆ and mHo[2]C·6PF₆ exist as air-stable singlet bisradicals, as evidenced by both X-ray crystallography in the solid state and EPR spectroscopy in solution. Electrochemical studies indicate that the first two reduction peaks of these two [2]catenanes are shifted significantly to more positive potentials, a feature which is responsible for their extraordinary stability in air. The mixed-valence nature of the mono- and bisradical states endows them with unique NIR absorption properties, e.g., NIR absorption bands for the mono- and bisradical states observed at ∼1800 and ∼1450 nm, respectively. These [2]catenanes are potentially useful in applications that include NIR photothermal conversion, UV–vis–NIR multiple-state electrochromic materials, and multiple-state memory devices. Our findings highlight the principle of “mechanical-bond-induced stabilization” as an efficient strategy for designing persistent organic radicals.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cai, Kang0000-0002-8883-0142
Liu, Wei-Guang0000-0002-6633-7795
Qiu, Yunyan0000-0001-9279-4714
Shi, Yi0000-0002-1981-8350
Liu, Zhichang0000-0003-3412-512X
Wasielewski, Michael R.0000-0003-2920-5440
Goddard, William A., III0000-0003-0097-5716
Stoddart, J. Fraser0000-0003-3161-3697
Additional Information:© 2020 American Chemical Society. Received: February 19, 2020; Published: March 30, 2020. The authors thank Northwestern University (NU) for their support of this research. This work also made use of the IMSERC at NU, which has received support from the State of Illinois and International Institute for Nanotechnology (IIN). Z.L. acknowledges support from the National Natural Science Foundation of China (No. 21971211) and the Supercomputer Center of Westlake University. The research at NU was also supported by National Science Foundation (NSF) grant no. CHE-1900422 (M.R.W.) The computational investigations at California Institute of Technology were supported by NSF grant no. CBET-1805022. The authors declare no competing financial interest.
Funding AgencyGrant Number
Northwestern UniversityUNSPECIFIED
State of IllinoisUNSPECIFIED
International Institute for Nanotechnology (IIN)UNSPECIFIED
National Natural Science Foundation of China21971211
Westlake UniversityUNSPECIFIED
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Issue or Number:15
Record Number:CaltechAUTHORS:20200330-102355321
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Official Citation:Highly Stable Organic Bisradicals Protected by Mechanical Bonds. Kang Cai, Haochuan Mao, Wei-Guang Liu, Yunyan Qiu, Yi Shi, Long Zhang, Dengke Shen, Hongliang Chen, Yang Jiao, Huang Wu, Zhichang Liu, Yuanning Feng, Charlotte L. Stern, Michael R. Wasielewski, William A. Goddard III, and J. Fraser Stoddart. Journal of the American Chemical Society 2020 142 (15), 7190-7197. DOI: 10.1021/jacs.0c01989
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102169
Deposited By: Tony Diaz
Deposited On:30 Mar 2020 17:38
Last Modified:11 Jul 2020 09:16

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