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Lin C, O'Connor JP, Phelan BT, Young RM, Wasielewski MR. Ultrafast Charge Transfer Dynamics in a Slip-Stacked Donor-Acceptor-Acceptor System. J Phys Chem A 2024; 128:244-250. [PMID: 38153126 DOI: 10.1021/acs.jpca.3c07539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Photoexcitation of molecular electron donor and/or acceptor chromophore aggregates can greatly affect their charge-transfer dynamics. Excitonic coupling not only alters the energy landscape in the excited state but may also open new photophysical pathways, such as symmetry-breaking charge separation (SB-CS). Here, we investigate the impact of excitonic coupling on a covalent donor-acceptor-acceptor system comprising a perylene donor (Per) and two perylenediimide (PDI) acceptor chromophores in which the three components are π-stacked in a geometry that is slipped along their long axes (Per-PDI2). Following selective photoexcitation of PDI, femtosecond transient absorption data for Per-PDI2 is compared to that for the single-donor, single-acceptor Per-PDI system, and the PDI2 dimer, which both have the same interchromophore geometry as Per-PDI2. The data show that electron transfer from Per to the lower exciton state of the PDI dimer is slower than that of the single PDI acceptor system. This is due to the lower free energy of the reaction for charge separation because of the electronic stabilization afforded by the excitonic coupling between the PDIs. While PDI2 was shown previously to undergo ultrafast SB-CS, the strong π-π electronic interaction of Per with the adjacent PDI in Per-PDI2 breaks the electronic symmetry of the PDI dimer, resulting in the oxidation of Per rather than SB-CS. These results show that the electronic coupling between molecules designed to accept charges produced by SB-CS in molecular dimers and the chromophores comprising the dimer must be balanced to favor SB-CS.
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Affiliation(s)
- Chenjian Lin
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - James P O'Connor
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Brian T Phelan
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ryan M Young
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R Wasielewski
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
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Alzola JM, Tcyrulnikov NA, Brown PJ, Marks TJ, Wasielewski MR, Young RM. Symmetry-Breaking Charge Separation in Phenylene-Bridged Perylenediimide Dimers. J Phys Chem A 2021; 125:7633-7643. [PMID: 34431674 DOI: 10.1021/acs.jpca.1c05100] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Perylenediimides (PDIs) are important molecular building blocks that are being investigated for their applicability in optoelectronic technologies. Covalently linking multiple PDI acceptors at the 2,5,8,11 (headland) positions adjacent to the PDI carbonyl groups is reported to yield higher power conversion efficiencies in photovoltaic cells relative to PDI acceptors linked at the 1,6,7,12 (bay) positions. While the photophysical properties of PDIs linked via the bay positions have been investigated extensively, those linked at the headland positions have received far less attention. We showed previously that symmetry-breaking charge separation (SB-CS) in PDIs hold promise as a strategy for increasing photovoltaic efficiency. Here we use transient absorption and emission spectroscopies to investigate the competition between SB-CS, fluorescence, and internal conversion in three related PDI dimers linked at the headland positions with o-, m-, and p-phenylene moieties: o-PDI2, m-PDI2, and p-PDI2, respectively. It is found that o-PDI2 supports SB-CS yielding PDI•+-PDI•-, which is in equilibrium with the o-PDI2 first excited state in a polar solvent (CH2Cl2) while m-PDI2 and p-PDI2 exhibit accelerated internal conversion due to the motion of the linker along with subnanosecond intersystem crossing (ISC). Electronic coupling and structural dynamics are shown to play a significant role, with o-PDI2 being the only member of the series that exhibits significant through-bond interchromophore coupling. The pronounced o-PDI2 steric congestion prevents the free internal rotation that leads to rapid deactivation of the excited state in the other dimers.
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Affiliation(s)
- Joaquin M Alzola
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Nikolai A Tcyrulnikov
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Paige J Brown
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Tobin J Marks
- 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
| | - Ryan M Young
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
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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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Lee CH, Yun YJ, Guo J, Chen LX, Mandal BK. Synthesis of a new zinc phthalocyanine–benzoquinone rigid dyad. J PORPHYR PHTHALOCYA 2020. [DOI: 10.1142/s1088424620500510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A new zinc phthalocyanine–benzoquinone rigid dyad, QnZnPc–G[Formula: see text] was synthesized as a model compound to study photo-induced charge separation mimicking natural photosynthesis. Compared to its previously reported analog, this dyad has an additional fused benzene ring between the zinc phthalocyanine (ZnPc) (donor) and benzoquinone (acceptor) moieties. The rigid structure of QnZnPc–G[Formula: see text] ([Formula: see text] no rotamers) is designed to minimize the unusual electronic perturbation induced by the internal motions, which resulted in a significant increase in the lifetime of the charged separated state (from 40 ps to 252 ps). Physical and photochemical properties of this new dyad were examined and discussed in this paper.
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Affiliation(s)
- Chi-Hang Lee
- Department of Chemistry, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, Illinois 60616, USA
| | - Young Ju Yun
- Department of Chemistry, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, Illinois 60616, USA
| | - Jianchang Guo
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Lin X. Chen
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Braja. K. Mandal
- Department of Chemistry, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, Illinois 60616, USA
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