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Bürgin T, Ogawa T, Wenger OS. Better Covalent Connection in a Molecular Triad Enables More Efficient Photochemical Energy Storage. Inorg Chem 2023; 62:13597-13607. [PMID: 37562775 PMCID: PMC10445269 DOI: 10.1021/acs.inorgchem.3c02008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Indexed: 08/12/2023]
Abstract
Numerous studies have explored the kinetics of light-induced charge separation and thermal charge recombination in donor-acceptor compounds, but quantum efficiencies have rarely been investigated. Here, we report on two essentially isomeric molecular triads, both comprising a π-extended tetrathiafulvalene (ExTTF) donor, a ruthenium(II)-based photosensitizer, and a naphthalene diimide (NDI) acceptor. The key difference between the two triads is how the NDI acceptor is connected. Linkage at the NDI core provides stronger electronic coupling to the other molecular components than connection via the nitrogen atoms of NDI. This change in molecular connectivity is expected to accelerate both energy-storing charge separation and energy-wasting charge recombination processes, but it is not a priori clear how this will affect the triad's ability to store photochemical energy; any gain resulting from faster charge separation could potentially be (over)compensated by losses through accelerated charge recombination. The new key insight emerging from our study is that the quantum yield for the formation of a long-lived charge-separated state increases by a factor of 5 when going from nitrogen- to core-connected NDI, providing the important proof of concept that better molecular connectivity indeed enables more efficient photochemical energy storage. The physical origin of this behavior seems to root in different orbital connectivity pathways for charge separation and charge recombination, as well as in differences in the relevant orbital interactions depending on NDI connection. Our work provides guidelines for how to discriminate between energy-storing and energy-wasting electron transfer reactions in order to improve the quantum yields for photochemical energy storage and solar energy conversion.
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Affiliation(s)
- Tobias
H. Bürgin
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
| | - Tomohiro Ogawa
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
- Graduate
School of Science and Engineering, University
of Toyama, Toyama 930-8555, Japan
| | - Oliver S. Wenger
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, Basel 4056, Switzerland
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2
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Islam MF, Sindt AJ, Hossain MS, Ayare PJ, Smith MD, Vannucci AK, Garashchuk S, Shimizu LS. Assembled triphenylamine bis-urea macrocycles: exploring photodriven electron transfer from host to guests. Phys Chem Chem Phys 2021; 23:23953-23960. [PMID: 34661219 DOI: 10.1039/d1cp03000k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Absorption of electronic acceptors in the accessible channels of an assembled triphenylamine (TPA) bis-urea macrocycle 1 enabled the study of electron transfer from the walls of the TPA framework to the encapsulated guests. The TPA host is isoskeletal in all host-guest structures analyzed with guests 2,1,3-benzothiadiazole, 2,5-dichlorobenzoquinone and I2 loading in single-crystal-to-single-crystal transformations. Analysis of the crystal structures highlights how the spatial proximity and orientation of the TPA host and the entrapped guests influence their resulting photophysical properties and allow direct comparison of the different donor-acceptor complexes. Diffuse reflectance spectroscopy shows that upon complex formation 1·2,5-dichlorobenzoquinone exhibits a charge transfer (CT) transition. Whereas, the 1·2,1,3-benzothiadiazole complex undergoes a photoinduced electron transfer (PET) upon irradiation with 365 nm LEDs. The CT absorptions were also identified with the aid of time dependent density functional theory (TD-DFT) calculations. Cyclic voltammetry experiments show that 2,1,3-benzothiadiazole undergoes reversible reduction within the host-guest complex. Moreover, the optical band gaps of the host 1·2,5-dichlorobenzoquinone (1.66 eV), and host 1·2,1,3-benzothiadiazole (2.15 eV) complexes are significantly smaller as compared to the free host 1 material (3.19 eV). Overall, understanding this supramolecular electron transfer strategy should pave the way towards designing lower band gap inclusion complexes.
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Affiliation(s)
- Md Faizul Islam
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Ammon J Sindt
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Muhammad Saddam Hossain
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Pooja J Ayare
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Mark D Smith
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Aaron K Vannucci
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Sophya Garashchuk
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
| | - Linda S Shimizu
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia South Carolina 29208, USA.
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Larsen CB, Farrow GA, Smith LD, Appleby MV, Chekulaev D, Weinstein JA, Wenger OS. Solvent-Mediated Activation/Deactivation of Photoinduced Electron-Transfer in a Molecular Dyad. Inorg Chem 2020; 59:10430-10438. [DOI: 10.1021/acs.inorgchem.0c00679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher B. Larsen
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, Basel CH-4056, Switzerland
| | - George A. Farrow
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Liam D. Smith
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Martin V. Appleby
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Dimitri Chekulaev
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Julia A. Weinstein
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Oliver S. Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, Basel CH-4056, Switzerland
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Castrogiovanni A, Herr P, Larsen CB, Guo X, Sparr C, Wenger OS. Shortcuts for Electron-Transfer through the Secondary Structure of Helical Oligo-1,2-Naphthylenes. Chemistry 2019; 25:16748-16754. [PMID: 31674695 DOI: 10.1002/chem.201904771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 10/30/2019] [Indexed: 01/24/2023]
Abstract
Atropisomeric 1,2-naphthylene scaffolds provide access to donor-acceptor compounds with helical oligomer-based bridges, and transient absorption studies revealed a highly unusual dependence of the electron-transfer rate on oligomer length, which is due to their well-defined secondary structure. Close noncovalent intramolecular contacts enable shortcuts for electron transfer that would otherwise have to occur over longer distances along covalent pathways, reminiscent of the behavior seen for certain proteins. The simplistic picture of tube-like electron transfer can describe this superposition of different pathways including both the covalent helical backbone, as well as noncovalent contacts, contrasting the wire-like behavior reported many times before for more conventional molecular bridges. The exquisite control over the molecular architecture, achievable with the configurationally stable and topologically defined 1,2-naphthylene-based scaffolds, is of key importance for the tube-like electron transfer behavior. Our insights are relevant for the emerging field of multidimensional electron transfer and for possible future applications in molecular electronics.
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Affiliation(s)
| | - Patrick Herr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christopher B Larsen
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Xingwei Guo
- Current address: Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing, 100084, P.R. China
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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Neumann S, Kerzig C, Wenger OS. Quantitative insights into charge-separated states from one- and two-pulse laser experiments relevant for artificial photosynthesis. Chem Sci 2019; 10:5624-5633. [PMID: 31293747 PMCID: PMC6553010 DOI: 10.1039/c9sc01381d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/01/2019] [Indexed: 01/25/2023] Open
Abstract
Charge-separated states (CSSs) are key intermediates in photosynthesis and solar energy conversion. However, the factors governing the formation efficiencies of CSSs are still poorly understood, and light-induced electron-hole recombinations as deactivation pathways competing with desired charge accumulations are largely unexplored. This greatly limits the possibility to perform efficient multi-electron transfer, which is essential for artificial photosynthesis. We present a systematic investigation of two donor-sensitizer-acceptor triads (with different donor-acceptor distances) capable of storing as much as 2.0 eV in their CSSs upon the absorption of a visible photon. Using quantitative one- and two-pulse laser flash photolysis, we provide deep insights into both the CSS formation quantum yield, which can reach up to 80%, and the fate of the CSS upon further (secondary) excitation with green photons. The triad with shorter intramolecular distances shows a remarkable excitation wavelength dependence of the CSS formation quantum yield, and the CSS of this triad undergoes more efficient light-induced charge recombination than the longer equivalent by about one order of magnitude, whilst thermal charge recombination shows the exact opposite behavior. The unexpected results of our detailed photophysical study can be rationalized by detrimental singlet charge transfer states or structural considerations, and could significantly contribute to the future design of CSS precursors for accumulative multi-electron transfer and artificial photosynthesis.
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Affiliation(s)
- Svenja Neumann
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland . ;
| | - Christoph Kerzig
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland . ;
| | - Oliver S Wenger
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland . ;
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Malzkuhn S, Guo X, Häussinger D, Wenger OS. Electron Transfer across o-Phenylene Wires. J Phys Chem A 2018; 123:96-102. [PMID: 30592217 DOI: 10.1021/acs.jpca.8b11236] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photoinduced electron transfer across rigid rod-like oligo- p-phenylenes has been thoroughly investigated in the past, but their o-connected counterparts are yet entirely unexplored in this regard. We report on three molecular dyads comprised of a triarylamine donor and a Ru(bpy)32+ (bpy =2,2'-bipyridine) acceptor connected covalently by 2 to 6 o-phenylene units. Pulsed excitation of the Ru(II) sensitizer at 532 nm leads to the rapid formation of oxidized triarylamine and reduced ruthenium complex via intramolecular electron transfer. The subsequent thermal reverse charge-shift reaction to reinstate the electronic ground-state occurs on a time scale of 120-220 ns in deaerated CH3CN at 25 °C. The conformational flexibility of the o-phenylene bridges causes multiexponential transient absorption kinetics for the photoinduced forward process, but the thermal reverse reaction produces single-exponential transient absorption decays. The key finding is that the flexible o-phenylene bridges permit rapid formation of photoproducts storing ca. 1.7 eV of energy with lifetimes on the order of hundreds of nanoseconds, similar to what is possible with rigid rod-like donor-acceptor compounds. Thus, the conformational flexibility of the o-phenylenes represents no disadvantage with regard to the photoproduct lifetimes, and this is relevant in the greater context of light-to-chemical energy conversion.
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Affiliation(s)
- Sabine Malzkuhn
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Xingwei Guo
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Daniel Häussinger
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Oliver S Wenger
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
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Schmidt HC, Larsen CB, Wenger OS. Electron Transfer around a Molecular Corner. Angew Chem Int Ed Engl 2018; 57:6696-6700. [DOI: 10.1002/anie.201800396] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 02/02/2018] [Indexed: 11/11/2022]
Affiliation(s)
- Hauke C. Schmidt
- Department of ChemistryUniversity of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christopher B. Larsen
- Department of ChemistryUniversity of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Oliver S. Wenger
- Department of ChemistryUniversity of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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8
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Affiliation(s)
- Hauke C. Schmidt
- Departement ChemieUniversität Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | | | - Oliver S. Wenger
- Departement ChemieUniversität Basel St. Johanns-Ring 19 4056 Basel Schweiz
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