Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor

Jiawang Zhou; Yilei Wu; Indranil Roy; Avik Samanta; J. Fraser Stoddart; Ryan M. Young; Michael R Wasielewski

doi:10.1039/C8SC05514A

Choosing sides

unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor

Jiawang Zhou, Yilei Wu, Indranil Roy, Avik Samanta, J. Fraser Stoddart, Ryan M. Young, Michael R Wasielewski

Northwestern University

Research output: Contribution to journal › Article

2 Citations (Scopus)

Abstract

Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor-bridge-acceptor (D-B-A) systems as well as competitive reaction pathways in acceptor-donor-acceptor (A-D-A) and acceptor-donor-acceptor′ (A-D-A′) systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV ²⁺ ) and dipyridylthiazolothiazole (TTz ²⁺ ) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox ⁴⁺ ), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox ⁴⁺ ) to establish an A-D-A′ system, in which the ExV ²⁺ and TTz ²⁺ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz ⁺ -Per ⁺ -ExV ²⁺ and TTz ²⁺ -Per ⁺ -ExV ⁺ in <1 ps, while back electron transfer in TTz ²⁺ -Per ⁺ -ExV ⁺ proceeds via the unusual sequence TTz ²⁺ -Per ⁺ -ExV ⁺ → TTz ⁺ -Per ⁺ -ExV ²⁺ → TTz ²⁺ -Per-ExV ²⁺ . In addition, selective chemical reduction of TTz ²⁺ gives Per ⊂ TTzExVBox ³⁺ turning the complex into a D-B-A system in which photoexcitation of TTz ⁺ results in the reaction sequence ² *TTz ⁺ -Per-ExV ²⁺ → TTz ²⁺ -Per-ExV ⁺ → TTz ⁺ -Per-ExV ²⁺ . Both reactions TTz ²⁺ -Per ⁺ -ExV ⁺ → TTz ⁺ -Per ⁺ -ExV ²⁺ and TTz ²⁺ -Per-ExV ⁺ → TTz ⁺ -Per-ExV ²⁺ occur with a (16 ± 1 ps) ⁻¹ rate constant irrespective of whether the bridge molecule is Per ⁺ or Per. These results are explained using the superexchange mechanism in which the ionic states of the perylene guest serve as virtual states in each case and demonstrate a novel supramolecular platform for studying the effects of bridge energetics within D-B-A systems.

Original language	English
Pages (from-to)	4282-4292
Number of pages	11
Journal	Chemical Science
Volume	10
Issue number	15
DOIs	https://doi.org/10.1039/C8SC05514A
Publication status	Published - Jan 1 2019

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Perylene

Charge transfer

Electrons

Photoexcitation

Viologens

ASJC Scopus subject areas

Chemistry(all)

Cite this

Zhou, J., Wu, Y., Roy, I., Samanta, A., Stoddart, J. F., Young, R. M., & Wasielewski, M. R. (2019). Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. Chemical Science, 10(15), 4282-4292. https://doi.org/10.1039/C8SC05514A

Choosing sides : unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. / Zhou, Jiawang; Wu, Yilei; Roy, Indranil; Samanta, Avik; Stoddart, J. Fraser; Young, Ryan M.; Wasielewski, Michael R.

In: Chemical Science, Vol. 10, No. 15, 01.01.2019, p. 4282-4292.

Research output: Contribution to journal › Article

Zhou, J, Wu, Y, Roy, I, Samanta, A, Stoddart, JF, Young, RM & Wasielewski, MR 2019, 'Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor', Chemical Science, vol. 10, no. 15, pp. 4282-4292. https://doi.org/10.1039/C8SC05514A

Zhou J, Wu Y, Roy I, Samanta A, Stoddart JF, Young RM et al. Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. Chemical Science. 2019 Jan 1;10(15):4282-4292. https://doi.org/10.1039/C8SC05514A

Zhou, Jiawang ; Wu, Yilei ; Roy, Indranil ; Samanta, Avik ; Stoddart, J. Fraser ; Young, Ryan M. ; Wasielewski, Michael R. / Choosing sides : unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. In: Chemical Science. 2019 ; Vol. 10, No. 15. pp. 4282-4292.

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abstract = "Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor-bridge-acceptor (D-B-A) systems as well as competitive reaction pathways in acceptor-donor-acceptor (A-D-A) and acceptor-donor-acceptor′ (A-D-A′) systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV 2+ ) and dipyridylthiazolothiazole (TTz 2+ ) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox 4+ ), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox 4+ ) to establish an A-D-A′ system, in which the ExV 2+ and TTz 2+ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz + -Per + -ExV 2+ and TTz 2+ -Per + -ExV + in <1 ps, while back electron transfer in TTz 2+ -Per + -ExV + proceeds via the unusual sequence TTz 2+ -Per + -ExV + → TTz + -Per + -ExV 2+ → TTz 2+ -Per-ExV 2+ . In addition, selective chemical reduction of TTz 2+ gives Per ⊂ TTzExVBox 3+ turning the complex into a D-B-A system in which photoexcitation of TTz + results in the reaction sequence 2 *TTz + -Per-ExV 2+ → TTz 2+ -Per-ExV + → TTz + -Per-ExV 2+ . Both reactions TTz 2+ -Per + -ExV + → TTz + -Per + -ExV 2+ and TTz 2+ -Per-ExV + → TTz + -Per-ExV 2+ occur with a (16 ± 1 ps) −1 rate constant irrespective of whether the bridge molecule is Per + or Per. These results are explained using the superexchange mechanism in which the ionic states of the perylene guest serve as virtual states in each case and demonstrate a novel supramolecular platform for studying the effects of bridge energetics within D-B-A systems.",

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10.1039/C8SC05514A