1
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Bancroft L, Zhang J, Harvey SM, Krzyaniak MD, Zhang P, Schaller RD, Beratan DN, Young RM, Wasielewski MR. Charge Transfer and Spin Dynamics in a Zinc Porphyrin Donor Covalently Linked to One or Two Naphthalenediimide Acceptors. J Phys Chem A 2021; 125:825-834. [PMID: 33449684 DOI: 10.1021/acs.jpca.0c10471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Quantum coherence effects on charge transfer and spin dynamics in a system having two degenerate electron acceptors are studied using a zinc 5,10,15-tri(n-pentyl)-20-phenylporphyrin (ZnP) electron donor covalently linked to either one or two naphthalene-1,8:4,5-bis(dicarboximide) (NDI) electron acceptors using an anthracene (An) spacer, ZnP-An-NDI (1) and ZnP-An-NDI2 (2), respectively. Following photoexcitation of 1 and 2 in toluene at 295 K, femtosecond transient absorption spectroscopy shows that the electron transfer (ET) rate constant for 2 is about three times larger than that of 1, which can be accounted for by the statistical nature of incoherent ET as well as the electron couplings for the charge separation reactions. In contrast, the rate constant for charge recombination (CR) of 1 is about 25% faster than that of 2. Using femtosecond transient infrared spectroscopy and theoretical analysis, we find that the electron on NDI2•- in 2 localizes onto one of the two NDIs prior to CR, thus precluding electronically coherent CR from NDI2•-. Conversely, CR in both 1 and 2 is spin coherent as indicated by the observation of a resonance in the 3*ZnP yield following CR as a function of applied magnetic field, giving spin-spin exchange interaction energies of 2J = 210 and 236 mT, respectively, where the line width of the resonance for 2 is greater than 1. These data show that while CR is a spin-coherent process, incoherent hopping of the electron between the two NDIs in 2, consistent with the lack of delocalization noted above, results in greater spin decoherence in 2 relative to 1.
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Affiliation(s)
- Laura Bancroft
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Jinyuan Zhang
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Samantha M Harvey
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D Krzyaniak
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Peng Zhang
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Richard D Schaller
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States.,Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - David N Beratan
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States.,Departments of Biochemistry and Physics, Duke University, Durham, North Carolina 27708, United States
| | - Ryan M Young
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R Wasielewski
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
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2
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Hagi S, Kato K, Hinoshita M, Yoshino H, Shikoh E, Teki Y. Low-magnetic field effect and electrically detected magnetic resonance measurements of photocurrent in vacuum vapor deposition films of weak charge-transfer pyrene/dimethylpyromellitdiimide (Py/DMPI) complex. J Chem Phys 2019; 151:244704. [DOI: 10.1063/1.5129188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- Shogo Hagi
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Ken Kato
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Masumi Hinoshita
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Harukazu Yoshino
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Eiji Shikoh
- Department of Physical Electronics and Informatics, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Yoshio Teki
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
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3
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Fay TP, Lewis AM, Manolopoulos DE. Spin-dependent charge recombination along para-phenylene molecular wires. J Chem Phys 2017; 147:064107. [DOI: 10.1063/1.4997482] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Affiliation(s)
- Thomas P. Fay
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Alan M. Lewis
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - David E. Manolopoulos
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
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4
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Horwitz NE, Phelan BT, Nelson JN, Mauck CM, Krzyaniak MD, Wasielewski MR. Spin Polarization Transfer from a Photogenerated Radical Ion Pair to a Stable Radical Controlled by Charge Recombination. J Phys Chem A 2017; 121:4455-4463. [DOI: 10.1021/acs.jpca.7b03468] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Noah E. Horwitz
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Brian T. Phelan
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Jordan N. Nelson
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Catherine M. Mauck
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D. Krzyaniak
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department
of Chemistry, ‡Argonne−Northwestern Solar Energy Research
(ANSER) Center, and §Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
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5
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Klein JH, Schmidt D, Steiner UE, Lambert C. Complete Monitoring of Coherent and Incoherent Spin Flip Domains in the Recombination of Charge-Separated States of Donor-Iridium Complex-Acceptor Triads. J Am Chem Soc 2015; 137:11011-21. [DOI: 10.1021/jacs.5b04868] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Johannes H. Klein
- Wilhelm
Conrad Röntgen Research Center for Complex Material Systems,
Würzburg, Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - David Schmidt
- Wilhelm
Conrad Röntgen Research Center for Complex Material Systems,
Würzburg, Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | | | - Christoph Lambert
- Wilhelm
Conrad Röntgen Research Center for Complex Material Systems,
Würzburg, Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
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6
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Kirk ML, Shultz DA, Stasiw DE, Habel-Rodriguez D, Stein B, Boyle PD. Electronic and Exchange Coupling in a Cross-Conjugated D–B–A Biradical: Mechanistic Implications for Quantum Interference Effects. J Am Chem Soc 2013; 135:14713-25. [DOI: 10.1021/ja405354x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Martin L. Kirk
- Department of
Chemistry, The University of New Mexico, MSC03 2060, Albuquerque, New Mexico 87131-0001, United States
| | - David A. Shultz
- Department of
Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Daniel E. Stasiw
- Department of
Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Diana Habel-Rodriguez
- Department of
Chemistry, The University of New Mexico, MSC03 2060, Albuquerque, New Mexico 87131-0001, United States
| | - Benjamin Stein
- Department of
Chemistry, The University of New Mexico, MSC03 2060, Albuquerque, New Mexico 87131-0001, United States
| | - Paul D. Boyle
- Department of
Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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7
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8
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Kirk ML, Shultz DA, Depperman EC, Habel-Rodriguez D, Schmidt RD. Spectroscopic studies of bridge contributions to electronic coupling in a donor-bridge-acceptor biradical system. J Am Chem Soc 2012; 134:7812-9. [PMID: 22480156 PMCID: PMC3398980 DOI: 10.1021/ja300233a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Variable-temperature electronic absorption and resonance Raman spectroscopies are used to probe the excited state electronic structure of Tp(Cum,Me)Zn(SQ-Ph-NN) (1), a donor-bridge-acceptor (D-B-A) biradical complex and a ground state analogue of the charge-separated excited state formed in photoinduced electron transfer reactions. Strong electronic coupling mediated by the p-phenylene bridge stabilizes the triplet ground state of this molecule. Detailed spectroscopic and bonding calculations elucidate key bridge distortions that are involved in the SQ(π)(SOMO) → NN-Ph (π*)(LUMO) D → A charge transfer (CT) transition. We show that the primary excited state distortion that accompanies this CT is along a vibrational coordinate best described as a symmetric Ph(8a) + SQ(in-plane) linear combination and underscores the dominant role of the phenylene bridge fragment acting as an electron acceptor in the D-B-A charge transfer state. Our results show the importance of the phenylene bridge in promoting (1) electron transfer in D-Ph-A systems and (2) electron transport in biased electrode devices that employ a 1,4-phenylene linkage. We have also developed a relationship between the spin density on the acceptor, as measured via the isotropic NN nitrogen hyperfine interaction, and the strength of the D → A interaction given by the magnitude of the electronic coupling matrix element, H(ab).
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Affiliation(s)
- Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001
| | - David A. Shultz
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204
| | - Ezra C. Depperman
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001
| | - Diana Habel-Rodriguez
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001
| | - Robert D. Schmidt
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204
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9
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Collauto A, Mannini M, Sorace L, Barbon A, Brustolon M, Gatteschi D. A slow relaxing species for molecular spin devices: EPR characterization of static and dynamic magnetic properties of a nitronyl nitroxide radical. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm35076a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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10
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Scott AM, Wasielewski MR. Temperature Dependence of Spin-Selective Charge Transfer Pathways in Donor−Bridge−Acceptor Molecules with Oligomeric Fluorenone and p-Phenylethynylene Bridges. J Am Chem Soc 2011; 133:3005-13. [DOI: 10.1021/ja1095649] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Amy M. Scott
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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11
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Kirk ML, Shultz DA, Habel-Rodriguez D, Schmidt RD, Sullivan U. Hyperfine Interaction, Spin Polarization, and Spin Delocalization as Probes of Donor−Bridge−Acceptor Interactions in Exchange-Coupled Biradicals. J Phys Chem B 2010; 114:14712-6. [PMID: 20553027 DOI: 10.1021/jp102955j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
| | - David A. Shultz
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
| | - Diana Habel-Rodriguez
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
| | - Robert D. Schmidt
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
| | - Ubie Sullivan
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
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12
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Knowles KE, Tice DB, McArthur EA, Solomon GC, Weiss EA. Chemical Control of the Photoluminescence of CdSe Quantum Dot−Organic Complexes with a Series of Para-Substituted Aniline Ligands. J Am Chem Soc 2009; 132:1041-50. [DOI: 10.1021/ja907253s] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Kathryn E. Knowles
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113
| | - Daniel B. Tice
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113
| | - Eric A. McArthur
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113
| | - Gemma C. Solomon
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113
| | - Emily A. Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113
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13
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Mi Q, Ratner MA, Wasielewski MR. Time-Resolved EPR Spectra of Spin-Correlated Radical Pairs: Spectral and Kinetic Modulation Resulting from Electron−Nuclear Hyperfine Interactions. J Phys Chem A 2009; 114:162-71. [DOI: 10.1021/jp907476q] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qixi Mi
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Mark A. Ratner
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
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14
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Kirk ML, Shultz DA, Depperman EC, Brannen CL. Donor−Acceptor Biradicals as Ground State Analogues of Photoinduced Charge Separated States. J Am Chem Soc 2007; 129:1937-43. [PMID: 17263528 DOI: 10.1021/ja065384t] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A Valence Bond Configuration Interaction (VBCI) model is used to relate the intraligand magnetic exchange interaction (J) to the electronic coupling matrix element (HAB) in Tp(Cum,MeZn)(SQNN), a compound that possesses a Donor-Acceptor (D-A) SemiQuinone-NitronylNitroxide (SQNN) biradical ligand. Within this framework, an SQ --> NN charge transfer state mixes with the ground state and stabilizes the spin triplet (S = 1). This charge-transfer transition is observed spectroscopically and probed using resonance Raman spectroscopy. In addition, the temperature-dependent electronic absorption spectrum of the Ni(II) complex, Tp(Cum,MeNi)(SQNN), has been studied. Exchange coupling between the S = 1 Ni(II) ion and S = 1 SQNN provides a mechanism for observing the formally spin-forbidden, ligand-based 3GC --> 1CTC transition. This provides a means of determining U, the mean GC --> CTC energy, and a one-center exchange integral, K(0). The experimental determination of J, U, and K(0) permits facile calculation of HAB, and we show that this methodology can be extended to determine the electronic coupling matrix element in related SQ-Bridge-NN molecules. As magnetic susceptibility measurements are easily acquired in the solid state, H(AB) may be effectively determined for single molecules in a known geometry, provided a crystal structure exists for the biradical complex. Thus, SQ-Bridge-NN molecules possess considerable potential for probing both geometric and electronic structure contributions to the magnitude of the electronic coupling matrix element associated with a given bridge fragment.
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Affiliation(s)
- Martin L Kirk
- Department of Chemistry, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, USA.
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15
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Oseki Y, Fujitsuka M, Cho DW, Sugimoto A, Tojo S, Majima T. Ultrafast Photoinduced Intramolecular Charge Separation and Recombination Processes in the Oligothiophene-Substituted Benzene Dyads with an Amide Spacer. J Phys Chem B 2005; 109:19257-62. [PMID: 16853487 DOI: 10.1021/jp0534784] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Photoinduced intramolecular charge separation (CS) and recombination (CR) processes of the tetrathiophene-substituted benzene dyads with an amide spacer (4T-PhR, R = 4-H (1), 4-CN (2), 3,4-(CN)2 (3), 4-NO2 (4), 3,5-(NO2)2 (5)) in solvents of different polarities were investigated using various fast spectroscopies. It was revealed that the CS rates depend on the ability of the acceptor and solvent polarity. Ultrafast CS with the rate of 5 x 10(12) s(-1) was revealed for 5 in PhCN and MeCN. The ultrafast CS can be attributed to the large electronic coupling matrix element between the donor and the acceptor despite the relative long donor-acceptor distance. The existence of the state with large electron density on the spacer between 14T*-PhR and LUMO should facilitate the CS process in the present dyad system. It was also revealed that the CR rates in these dyads were rather fast because of the enhanced superexchange interaction through the amide spacer.
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Affiliation(s)
- Yosuke Oseki
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567- 0047, Japan
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16
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Weiss EA, Tauber MJ, Kelley RF, Ahrens MJ, Ratner MA, Wasielewski MR. Conformationally Gated Switching between Superexchange and Hopping within Oligo-p-phenylene-Based Molecular Wires. J Am Chem Soc 2005; 127:11842-50. [PMID: 16104763 DOI: 10.1021/ja052901j] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We observe well-defined regions of superexchange and thermally activated hopping in the temperature dependence of charge recombination (CR) in a series of donor-bridge-acceptor (D-B-A) systems, where D = phenothiazine (PTZ), B = p-phenylene (Ph(n)), n = 1-4, and A = perylene-3,4:9,10-bis(dicarboximide) (PDI). A fit to the thermally activated CR rates of the n = 3 and n = 4 compounds yields activation barriers of 1290 and 2030 cm(-1), respectively, which match closely with theoretically predicted and experimentally observed barriers for the planarization of terphenyl and quaterphenyl. Negative activation of CR in the temperature regions dominated by superexchange charge transport is the result of a fast conformational equilibrium that increasingly depopulates the reactive state for CR as temperature is increased. The temperature dependence of the effective donor-acceptor superexchange coupling, V(DA), measured using magnetic field effects on the efficiency of the charge recombination process, shows that CR occurs out of the conformation with lower V(DA) via the energetically favored triplet pathway.
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Affiliation(s)
- Emily A Weiss
- Center for Nanofabrication and Molecular Self-Assembly and Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA
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