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Rotaxane-based transition metal complexes: effect of the mechanical bond on structure and electronic properties

Rotaxane-based transition metal complexes: effect of the mechanical bond on structure and electronic properties
Rotaxane-based transition metal complexes: effect of the mechanical bond on structure and electronic properties
Early work by Sauvage revealed that mechanical bonding alters the stability and redox properties of their original catenane metal complexes. However, despite the importance of controlling metal ion properties for a range of applications, these effects have received relatively little attention since. Here we present a series of tri-, tetra-, and pentadentate rotaxane-based ligands and a detailed study of their metal binding behavior and, where possible, compare their redox and electronic properties with their noninterlocked counterparts. The rotaxane ligands form complexes with most of the metal ions investigated, and X-ray diffraction revealed that in some cases the mechanical bond enforces unusual coordination numbers and distorted arrangements as a result of the exclusion of exogenous ligands driven by the sterically crowded binding sites. In contrast, only the noninterlocked equivalent of the pentadentate rotaxane CuII complex could be formed selectively, and this exhibited compromised redox stability compared to its interlocked counterpart. Frozen-solution EPR data demonstrate the formation of an interesting biomimetic state for the tetradentate CuII rotaxane, as well as the formation of stable NiI species and the unusual coexistence of high- and low-spin CoII in the pentadentate framework. Our results demonstrate that readily available mechanically chelating rotaxanes give rise to complexes the noninterlocked equivalent of which are inaccessible, and that the mechanical bond augments the redox behavior of the bound metal ion in a manner analogous to the carefully tuned amino acid framework in metalloproteins.
0002-7863
879-889
Cirulli, Martina
96448dc8-63d7-4f0b-9a09-18f96452aec2
Kaur, Amanpreet
d6c7e09a-e2e2-4d97-ad62-ea8c112c1fdd
Lewis, James E.M.
42b46a03-a7ca-4d3a-96e5-a5c962fc9573
Zhang, Zhihui
57097735-da7b-48b8-a815-b3da868d142e
Kitchen, Jonathan A.
3999f5cb-d53e-4c51-b750-627bd2a1b9b6
Goldup, Stephen M.
0a93eedd-98bb-42c1-a963-e2815665e937
Roessler, Maxie M.
3baa37c6-6453-4e49-a662-a0930ae9a07f
Cirulli, Martina
96448dc8-63d7-4f0b-9a09-18f96452aec2
Kaur, Amanpreet
d6c7e09a-e2e2-4d97-ad62-ea8c112c1fdd
Lewis, James E.M.
42b46a03-a7ca-4d3a-96e5-a5c962fc9573
Zhang, Zhihui
57097735-da7b-48b8-a815-b3da868d142e
Kitchen, Jonathan A.
3999f5cb-d53e-4c51-b750-627bd2a1b9b6
Goldup, Stephen M.
0a93eedd-98bb-42c1-a963-e2815665e937
Roessler, Maxie M.
3baa37c6-6453-4e49-a662-a0930ae9a07f

Cirulli, Martina, Kaur, Amanpreet, Lewis, James E.M., Zhang, Zhihui, Kitchen, Jonathan A., Goldup, Stephen M. and Roessler, Maxie M. (2019) Rotaxane-based transition metal complexes: effect of the mechanical bond on structure and electronic properties. Journal of the American Chemical Society, 141 (2), 879-889. (doi:10.1021/jacs.8b09715).

Record type: Article

Abstract

Early work by Sauvage revealed that mechanical bonding alters the stability and redox properties of their original catenane metal complexes. However, despite the importance of controlling metal ion properties for a range of applications, these effects have received relatively little attention since. Here we present a series of tri-, tetra-, and pentadentate rotaxane-based ligands and a detailed study of their metal binding behavior and, where possible, compare their redox and electronic properties with their noninterlocked counterparts. The rotaxane ligands form complexes with most of the metal ions investigated, and X-ray diffraction revealed that in some cases the mechanical bond enforces unusual coordination numbers and distorted arrangements as a result of the exclusion of exogenous ligands driven by the sterically crowded binding sites. In contrast, only the noninterlocked equivalent of the pentadentate rotaxane CuII complex could be formed selectively, and this exhibited compromised redox stability compared to its interlocked counterpart. Frozen-solution EPR data demonstrate the formation of an interesting biomimetic state for the tetradentate CuII rotaxane, as well as the formation of stable NiI species and the unusual coexistence of high- and low-spin CoII in the pentadentate framework. Our results demonstrate that readily available mechanically chelating rotaxanes give rise to complexes the noninterlocked equivalent of which are inaccessible, and that the mechanical bond augments the redox behavior of the bound metal ion in a manner analogous to the carefully tuned amino acid framework in metalloproteins.

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MS Cirulli metal complexes (final) - Accepted Manuscript
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Accepted/In Press date: 18 December 2018
e-pub ahead of print date: 18 December 2018
Published date: 16 January 2019

Identifiers

Local EPrints ID: 427330
URI: http://eprints.soton.ac.uk/id/eprint/427330
ISSN: 0002-7863
PURE UUID: 644e78aa-9728-4b99-a6b5-b6170693eddb
ORCID for Jonathan A. Kitchen: ORCID iD orcid.org/0000-0002-7139-5666
ORCID for Stephen M. Goldup: ORCID iD orcid.org/0000-0003-3781-0464

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Date deposited: 14 Jan 2019 17:30
Last modified: 15 Sep 2021 04:34

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Contributors

Author: Martina Cirulli
Author: Amanpreet Kaur
Author: James E.M. Lewis
Author: Zhihui Zhang
Author: Jonathan A. Kitchen ORCID iD
Author: Maxie M. Roessler

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