CaltechAUTHORS
  A Caltech Library Service

Size-Matched Radical Multivalency

Lipke, Mark C. and Cheng, Tao and Wu, Yilei and Arslan, Hasan and Xiao, Hai and Wasielewski, Michael R. and Goddard, William A., III and Stoddart, J. Fraser (2017) Size-Matched Radical Multivalency. Journal of the American Chemical Society, 139 (11). pp. 3986-3998. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20170211-114652730

[img] PDF - Accepted Version
See Usage Policy.

3095Kb
[img] PDF (Experimental details, including crystal structure refinement details, cyclic voltammograms, UV–Vis–NIR spectra, EPR spectra, DFT calculations, and details of data processing) - Supplemental Material
See Usage Policy.

4Mb
[img] Crystallographic Info File (CIF) (X-ray crystallographic data for [MS⊂m-CBPQT]·4PF6) - Supplemental Material
See Usage Policy.

1359Kb
[img] Crystallographic Info File (CIF) (X-ray crystallographic data for m-CBPQT·2PF6) - Supplemental Material
See Usage Policy.

131Kb
[img] Crystallographic Info File (CIF) (X-ray crystallographic data for MS·2PF6) - Supplemental Material
See Usage Policy.

722Kb

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20170211-114652730

Abstract

Persistent π-radicals such as MV^+• (MV refers to methyl viologen, i.e., N,Nꞌ-dimethyl-4,4ꞌ-bipyridinum) engage in weak radical-radical interactions. This phenomenon has been utilized recently in supramolecular chemistry with the discovery that MV+• and [cyclobis(paraquat-p-phenylene)]2(+•) (CBPQT2(+•)) form a strong 1:1 host-guest complex [CBPQT⊂MV]3(+•). In this full paper, we describe the extension of radical-pairing-based molecular recognition to a larger, square-shaped diradical host, [cyclobis(paraquat-4,4ꞌ-biphenylene)]2(+•) (MS2(+•)). This molecular square was assessed for its ability to bind an isomeric series of possible diradical cyclophane guests, which consist of two radical viologen units that are linked by two ortho-, meta-, or para-xylylene bridges to provide different spacings between the planar radicals. UV-Vis-NIR measurements reveal that only the m-xylylene-linked isomer (m-CBPQT2(+•)) binds strongly inside of MS2(+•), resulting in the formation of a tetra-radical complex [MS⊂m-CBPQT]4(+•). Titration experiments and variable temperature UV-Vis-NIR and EPR spectroscopic data indicate that, relative to the smaller tris-radical complex [CBPQT⊂MV]3(+•), the new host-guest complex forms with a more favorable enthalpy change that is offset by a greater entropic penalty. As a result, the association constant (Ka = (1.12+/- 0.08) x 10^5 M^(-1)) for [MS⊂m-CBPQT]4(+•) is similar to that previously determined for [CBPQT⊂MV]3(+•). The (super)structures of MS2(+•), m-CBPQT2(+•), and [MS⊂m-CBPQT]4(+•) were examined by single-crystal X-ray diffraction measurements and DFT calculations. The solid-state and computational structural analyses reveal that m-CBPQT2(+•) is ideally sized to bind inside of MS2(+•). The solid-state superstructures also indicate that localized radical-radical interactions in m-CBPQT2(+•) and [MS⊂m-CBPQT]4(+•) disrupt the extended radical-pairing interactions that are common in crystals of other viologen radical cations. Lastly, the formation of [MS⊂m-CBPQT]4(+•) was probed by cyclic voltammetry, demonstrating that the radical states of the cyclophanes are stabilized by the radical-pairing interactions.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jacs.6b09892DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jacs.6b09892PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/jacs.6b09892PublisherSupporting Information
ORCID:
AuthorORCID
Cheng, Tao0000-0003-4830-177X
Wu, Yilei0000-0001-6756-1855
Xiao, Hai0000-0001-9399-1584
Goddard, William A., III0000-0003-0097-5716
Stoddart, J. Fraser0000-0003-3161-3697
Additional Information:© 2017 American Chemical Society. Received: September 20, 2016; Published: February 7, 2017. This research is part of the Joint Center of Excellence in Integrated Nano-Systems (JCIN) at King Abdulaziz City of 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. Computational investigations were supported by the U.S. National Science Foundation under grant no. EFRI-1332411 (W.A. Goddard III and T. Cheng). Electron paramagnetic resonance studies were supported by the U.S. National Science Foundation under grant no. CHE-1565925 (M.R. Wasielewski). Y. Wu thanks the Fulbright Scholar Program for a Fellowship and the NU International Institute of Nanotechnology for a Ryan Fellowship. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
King Abdulaziz City of Science and TechnologyUNSPECIFIED
Northwestern UniversityUNSPECIFIED
NSFEFRI-1332411
NSFCHE-1565925
Fulbright FoundationUNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20170211-114652730
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170211-114652730
Official Citation:Size-Matched Radical Multivalency Mark C. Lipke, Tao Cheng, Yilei Wu, Hasan Arslan, Hai Xiao, Michael R. Wasielewski, William A. Goddard III, and J. Fraser Stoddart Journal of the American Chemical Society 2017 139 (11), 3986-3998 DOI: 10.1021/jacs.6b09892 Mark C. Lipke, Tao Cheng, Yilei Wu, Hasan Arslan, Hai Xiao, Michael R. Wasielewski, William A. Goddard, and J. Fraser Stoddart Journal of the American Chemical Society Just Accepted Manuscript DOI: 10.1021/jacs.6b09892
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74220
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:13 Feb 2017 17:03
Last Modified:03 Oct 2019 16:36

Repository Staff Only: item control page