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Zhou J, Wu Y, Roy I, Samanta A, Stoddart JF, Young RM, Wasielewski MR. Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. Chem Sci 2019; 10:4282-4292. [PMID: 31057755 PMCID: PMC6471873 DOI: 10.1039/c8sc05514a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/06/2019] [Indexed: 12/20/2022] Open
Abstract
Photo-driven electron transfer is faster from an electron donor guest to the harder to reduce acceptor in an asymmetric cyclophane host.
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 (ExV2+) and dipyridylthiazolothiazole (TTz2+) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox4+), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox4+) to establish an A–D–A′ system, in which the ExV2+ and TTz2+ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz+˙–Per+˙–ExV2+ and TTz2+–Per+˙–ExV+˙ in <1 ps, while back electron transfer in TTz2+–Per+˙–ExV+˙ proceeds via the unusual sequence TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ → TTz2+–Per–ExV2+. In addition, selective chemical reduction of TTz2+ gives Per ⊂ TTzExVBox3+˙, turning the complex into a D–B–A system in which photoexcitation of TTz+˙ results in the reaction sequence 2*TTz+˙–Per–ExV2+ → TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+. Both reactions TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ and TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+ 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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Affiliation(s)
- Jiawang Zhou
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Yilei Wu
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Indranil Roy
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ;
| | - Avik Samanta
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ;
| | - J Fraser Stoddart
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Molecular Design and Synthesis , Tianjin University , Tianjin 300072 , China.,School of Chemistry , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Ryan M Young
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Michael R Wasielewski
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
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Chakrabarti S, Parker MFL, Morgan CW, Schafmeister CE, Waldeck DH. Experimental evidence for water mediated electron transfer through bis-amino acid donor-bridge-acceptor oligomers. J Am Chem Soc 2009; 131:2044-5. [PMID: 19173584 DOI: 10.1021/ja8079324] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
This work compares the photoinduced unimolecular electron transfer rate constants for two different solute molecules (D-SSS-A and D-SRR-A) in water and DMSO solvents. The D-SSS-A solute has a cleft between the electron donor and acceptor units, which is able to contain a water molecule but is too small for DMSO. The rate constant for D-SSS-A in water is significantly higher than that for D-SRR-A, which lacks a cleft, and significantly higher for either solute in DMSO. The enhancement of the rate constant is explained by an electron tunneling pathway that involves water molecule(s).
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Affiliation(s)
- Subhasis Chakrabarti
- University of Pittsburgh, Department of Chemistry, Pittsburgh, Pennsylvania 15260, USA
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Chakrabarti S, Liu M, Waldeck DH, Oliver AM, Paddon-Row MN. Solvent Dynamical Effects on Electron Transfer in U-Shaped Donor-Bridge-Acceptor Molecules. J Phys Chem A 2009; 113:1040-8. [DOI: 10.1021/jp807412c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Subhasis Chakrabarti
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Min Liu
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - David H. Waldeck
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Anna M. Oliver
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Michael N. Paddon-Row
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
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Chakrabarti S, Liu M, Waldeck DH, Oliver AM, Paddon-Row MN. Competing Electron-Transfer Pathways in Hydrocarbon Frameworks: Short-Circuiting Through-Bond Coupling by Nonbonded Contacts in Rigid U-Shaped Norbornylogous Systems Containing a Cavity-Bound Aromatic Pendant Group. J Am Chem Soc 2007; 129:3247-56. [PMID: 17315995 DOI: 10.1021/ja067266b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This work explores electron transfer through nonbonded contacts in two U-shaped DBA molecules 1DBA and 2DBA by measuring electron-transfer rates in organic solvents of different polarities. These molecules have identical U-shaped norbornylogous frameworks, 12 bonds in length and with diphenyldimethoxynaphthalene (DPMN) donor and dicyanovinyl (DCV) acceptor groups fused at the ends. The U-shaped cavity of each molecule contains an aromatic pendant group of different electronic character, namely p-ethylphenyl, in 1DBA, and p-methoxyphenyl, in 2DBA. Electronic coupling matrix elements, Gibbs free energy, and reorganization energy were calculated from experimental photophysical data for these compounds, and the experimental results were compared with computational values. The magnitude of the electronic coupling for photoinduced charge separation, /V(CS)/, in 1DBA and 2DBA were found to be 147 and 274 cm(-1), respectively, and suggests that the origin of this difference lies in the electronic nature of the pendant aromatic group and charge separation occurs by tunneling through the pendant group, rather than through the bridge. 2DBA, but not 1DBA, displayed charge transfer (CT) fluorescence in nonpolar and weakly polar solvents, and this observation enabled the electronic coupling for charge recombination, /V(CR)/, in 2DBA to be made, the magnitude of which is approximately 500 cm(-1), significantly larger than that for charge separation. This difference is explained by changes in the geometry of the molecule in the relevant states; because of electrostatic effects, the donor and acceptor chromophores are about 1 A closer to the pendant group in the charge-separated state than in the locally excited state. Consequently the through-pendant-group electronic coupling is stronger in the charge-separated state--which controls the CT fluorescence process--than in the locally excited state--which controls the charge separation process. The magnitude of /V(CR)/ for 2DBA is almost 2 orders of magnitude greater than that in DMN-12-DCV, having the same length bridge as for the former molecule, but lacking a pendant group. This result unequivocally demonstrates the operation of the through-pendant-group mechanism of electron transfer in the pendant-containing U-shaped systems of the type 1DBA and 2DBA.
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Affiliation(s)
- Subhasis Chakrabarti
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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Bell TDM, Stefan A, Lemaur V, Bernhardt S, Müllen K, Cornil J, Beljonne D, Hofkens J, Van der Auweraer M, De Schryver FC. Non-conjugated, phenyl assisted coupling in through bond electron transfer in a perylenemonoimide–triphenylamine system. Photochem Photobiol Sci 2007; 6:406-15. [PMID: 17404635 DOI: 10.1039/b617913d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two donor-bridge-acceptor compounds containing triphenylamine (TPA) donors and perylenemonoimide (PMI) acceptors have been studied by spectroscopic techniques and quantum chemical computation. Both systems have been observed to emit prompt and delayed fluorescence under certain conditions indicating that forward and reverse electron transfer (ET) processes can occur between the locally excited and the charge separated states. The experimental and computational results show that the TPA and PMI chromophores are better coupled by almost 50% in the meta isomers which undergo ET more readily than the para isomers. Quantum chemical calculations indicate that this unexpected situation is the result of a phenyl group on the side of the bridge being advantageously positioned in the meta isomers. This leads to more extensive delocalisation of the TPA HOMO into the bridge enhancing the total through bond electronic coupling between the TPA and PMI chromophores. The calculations also indicate a strong angle dependence of the total coupling in both isomers. The experimental results are discussed in the context of the high temperature limit of Marcus's theory of non-adiabatic ET.
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Affiliation(s)
- Toby D M Bell
- Department of Chemistry, Katholieke Universiteit Leuven, Insitute for Nanoscale Physics and Chemistry, Celestijnenlaan 200F, 3001, Heverlee, Belgium
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