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Kopp SM, Redman AJ, Rončević I, Schröder L, Bogani L, Anderson HL, Timmel CR. Charge and Spin Transfer Dynamics in a Weakly Coupled Porphyrin Dimer. J Am Chem Soc 2024; 146:21476-21489. [PMID: 39042706 PMCID: PMC11311228 DOI: 10.1021/jacs.4c04186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
The dynamics of electron and spin transfer in the radical cation and photogenerated triplet states of a tetramethylbiphenyl-linked zinc-porphyrin dimer were investigated, so as to test the relevant parameters for the design of a single-molecule spin valve and the creation of a novel platform for the photogeneration of high-multiplicity spin states. We used a combination of multiple techniques, including variable-temperature continuous wave EPR, pulsed proton electron-nuclear double resonance (ENDOR), transient EPR, and optical spectroscopy. The conclusions are further supported by density functional theory (DFT) calculations and comparison to reference compounds. The low-temperature cw-EPR and room-temperature near-IR spectra of the dimer monocation demonstrate that the radical cation is spatially localized on one side of the dimer at any point in time, not coherently delocalized over both porphyrin units. The EPR spectra at 298 K reveal rapid hopping of the radical spin density between both sites of the dimer via reversible intramolecular electron transfer. The hyperfine interactions are modulated by electron transfer and can be quantified using ENDOR spectroscopy. This allowed simulation of the variable-temperature cw-EPR spectra with a two-site exchange model and provided information on the temperature-dependence of the electron transfer rate. The electron transfer rates range from about 10.0 MHz at 200 K to about 53.9 MHz at 298 K. The activation enthalpies Δ‡H of the electron transfer were determined as Δ‡H = 9.55 kJ mol-1 and Δ‡H = 5.67 kJ mol-1 in a 1:1:1 solvent mixture of CD2Cl2/toluene-d8/THF-d8 and in 2-methyltetrahydrofuran, respectively, consistent with a Robin-Day class II mixed valence compound. These results indicate that the interporphyrin electronic coupling in a tetramethylbiphenyl-linked porphyrin dimer is suitable for the backbone of a single-molecule spin valve. Investigation of the spin density distribution of the photogenerated triplet state of the Zn-porphyrin dimer reveals localization of the triplet spin density on a nanosecond time scale on one-half of the dimer at 20 K in 2-methyltetrahydrofuran and at 250 K in a polyvinylcarbazole film. This establishes the porphyrin dimer as a molecular platform for the formation of a localized, photogenerated triplet state on one porphyrin unit that is coupled to a second redox-active, ground-state porphyrin unit, which can be explored for the formation of high-multiplicity spin states.
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Affiliation(s)
- Sebastian M Kopp
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Oxford, OX1 3QR, U.K
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, U.K
| | - Ashley J Redman
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Oxford, OX1 3QR, U.K
| | - Igor Rončević
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, U.K
| | - Lisa Schröder
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, U.K
| | - Lapo Bogani
- Department of Materials, University of Oxford, Oxford, OX1 3PH, U.K
| | - Harry L Anderson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, U.K
| | - Christiane R Timmel
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Oxford, OX1 3QR, U.K
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Naghibi S, Sangtarash S, Kumar VJ, Wu J, Judd MM, Qiao X, Gorenskaia E, Higgins SJ, Cox N, Nichols RJ, Sadeghi H, Low PJ, Vezzoli A. Redox-Addressable Single-Molecule Junctions Incorporating a Persistent Organic Radical. Angew Chem Int Ed Engl 2022; 61:e202116985. [PMID: 35289977 PMCID: PMC9322687 DOI: 10.1002/anie.202116985] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Indexed: 12/14/2022]
Abstract
Integrating radical (open-shell) species into non-cryogenic nanodevices is key to unlocking the potential of molecular electronics. While many efforts have been devoted to this issue, in the absence of a chemical/electrochemical potential the open-shell character is generally lost in contact with the metallic electrodes. Herein, single-molecule devices incorporating a 6-oxo-verdazyl persistent radical have been fabricated using break-junction techniques. The open-shell character is retained at room temperature, and electrochemical gating permits in situ reduction to a closed-shell anionic state in a single-molecule transistor configuration. Furthermore, electronically driven rectification arises from bias-dependent alignment of the open-shell resonances. The integration of radical character, transistor-like switching, and rectification in a single molecular component paves the way to further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.
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Affiliation(s)
- Saman Naghibi
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | | | - Varshini J. Kumar
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Jian‐Zhong Wu
- School of ChemistrySouth China Normal UniversityGuangzhou510006P.R. China
| | - Martyna M. Judd
- Research School of ChemistryAustralian National UniversityCanberraATC 2601Australia
| | - Xiaohang Qiao
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Elena Gorenskaia
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Simon J. Higgins
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Nicholas Cox
- Research School of ChemistryAustralian National UniversityCanberraATC 2601Australia
| | - Richard J. Nichols
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
| | - Hatef Sadeghi
- School of EngineeringUniversity of WarwickCoventryCV4 7ALUK
| | - Paul J. Low
- School of Molecular SciencesUniversity of Western AustraliaCrawleyWestern Australia6009Australia
| | - Andrea Vezzoli
- Department of ChemistryUniversity of LiverpoolCrown StreetLiverpoolL69 7ZDUK
- Stephenson Institute for Renewable EnergyUniversity of LiverpoolPeach StreetLiverpoolL69 7ZFUK
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Phenylene-linked tetrapyrrole arrays containing free base and diverse metal chelate forms – Versatile synthetic architectures for catalysis and artificial photosynthesis. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214278] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Gao D, Aly SM, Karsenti PL, Brisard G, Harvey PD. Increasing the lifetimes of charge separated states in porphyrin-fullerene polyads. Phys Chem Chem Phys 2018; 19:24018-24028. [PMID: 28832037 DOI: 10.1039/c7cp04193d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two linear polyads were designed using zinc(ii)porphyrin, [ZnP], and N-methyl-2-phenyl-3,4-fullero-pyrrolidine (C60) where C60 is dangling either at the terminal position of [ZnP]-C6H4-[triple bond, length as m-dash]-C6H4-[ZnP]-C60 (1) or at the central position of [ZnP]-C6H4-[triple bond, length as m-dash]-C6H4-[ZnP(C60)]-C6H4-[triple bond, length as m-dash]-C6H4-[ZnP] (2) in order to test whether the fact of having one or two side electron donors influences the rate of electron transfer, ket. These polyads were studied using cyclic voltammograms, DFT computations, steady state and time-resolved fluorescence spectroscopy, and femtosecond transient absorption spectroscopy (fs-TAS). Photo-induced electron transfer confirmed by the detection of the charge separated state [ZnP˙+]/C60˙- from fs-TAS occurs with rates (ket) of 3-4 × 1010 s-1 whereas the charge recombinations (CRs) are found to produce the [ZnP] ground state via two pathways (central [ZnP˙+]/C60˙- (ps) and terminal central [ZnP˙+]/C60˙- (ns) producing [1ZnP] (ground state) and [3ZnP*]). The formation of the T1 species is more predominant for 2.
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Affiliation(s)
- Di Gao
- Departement de Chimie, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada.
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Hondros CJ, Aravindu K, Diers JR, Holten D, Lindsey JS, Bocian DF. Effects of Linker Torsional Constraints on the Rate of Ground-State Hole Transfer in Porphyrin Dyads. Inorg Chem 2012; 51:11076-86. [DOI: 10.1021/ic301613k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Christopher J. Hondros
- Department of Chemistry, University of California Riverside, Riverside, California
92521-0403, United States
| | - Kunche Aravindu
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina
27695-8204, United States
| | - James R. Diers
- Department of Chemistry, University of California Riverside, Riverside, California
92521-0403, United States
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, Missouri 63130-4889,
United States
| | - Jonathan S. Lindsey
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina
27695-8204, United States
| | - David F. Bocian
- Department of Chemistry, University of California Riverside, Riverside, California
92521-0403, United States
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Tsuchiya T, Jakubikova E. Role of Noncoplanar Conformation in Facilitating Ground State Hole Transfer in Oxidized Porphyrin Dyads. J Phys Chem A 2012; 116:10107-14. [DOI: 10.1021/jp307285z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Takashi Tsuchiya
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United
States
| | - Elena Jakubikova
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United
States
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Liu Y, Lin H, Li J, Dy JT, Tamaki K, Nakazaki J, Nakayama D, Nishiyama C, Uchida S, Kubo T, Segawa H. Ethynyl-linked push–pull porphyrin hetero-dimers for near-IR dye-sensitized solar cells: photovoltaic performances versus excited-state dynamics. Phys Chem Chem Phys 2012; 14:16703-12. [DOI: 10.1039/c2cp43165c] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Thulstrup PW, Hoffmann SV, Hansen BKV, Spanget-Larsen J. Unique interplay between electronic states and dihedral angle for the molecular rotor diphenyldiacetylene. Phys Chem Chem Phys 2011; 13:16168-74. [DOI: 10.1039/c0cp02914a] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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