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Doheny PW, Hua C, Chan B, Tuna F, Collison D, Kepert CJ, D'Alessandro DM. Substituent effects on through-space intervalence charge transfer in cofacial metal-organic frameworks. Faraday Discuss 2021; 231:152-167. [PMID: 34251000 DOI: 10.1039/d1fd00021g] [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
Electroactive metal-organic frameworks (MOFs) are an attractive class of materials owing to their multifunctional 3-dimensional structures, the properties of which can be modulated by changing the redox states of the components. In order to realise both fundamental and applied goals for these materials, a deeper understanding of the structure-function relationships that govern the charge transfer mechanisms is required. Chemical or electrochemical reduction of the framework [Zn(BPPFTzTz)(tdc)]·2DMF, hereafter denoted ZnFTzTz (where BPPFTzTz = 2,5-bis(3-fluoro-4-(pyridin-4-yl)phenyl)thiazolo[5,4-d]thiazole), generates mixed-valence states with optical signatures indicative of through-space intervalence charge transfer (IVCT) between the cofacially stacked ligands. Fluorination of the TzTz ligands influences the IVCT band parameters relative to the unsubstituted parent system, as revealed through Marcus-Hush theory analysis and single crystal UV-Vis spectroscopy. Using a combined experimental, theoretical and density functional theory (DFT) analysis, important insights into the effects of structural modifications, such as ligand substitution, on the degree of electronic coupling and rate of electron transfer have been obtained.
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Affiliation(s)
- Patrick W Doheny
- School of Chemistry, The University of Sydney, New South Wales, 2006 Australia.
| | - Carol Hua
- School of Chemistry, The University of Sydney, New South Wales, 2006 Australia. .,School of Chemistry, The University of Melbourne, Victoria, 3010 Australia
| | - Bun Chan
- Graduate School of Engineering, Nagasaki University, Nagasaki 852-8521, Japan
| | - Floriana Tuna
- Department of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK
| | - David Collison
- Department of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK
| | - Cameron J Kepert
- School of Chemistry, The University of Sydney, New South Wales, 2006 Australia.
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Timpmann K, Jalviste E, Chenchiliyan M, Kangur L, Jones MR, Freiberg A. High-pressure tuning of primary photochemistry in bacterial photosynthesis: membrane-bound versus detergent-isolated reaction centers. PHOTOSYNTHESIS RESEARCH 2020; 144:209-220. [PMID: 32095925 DOI: 10.1007/s11120-020-00724-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 02/11/2020] [Indexed: 06/10/2023]
Abstract
While photosynthesis thrives at close to normal pressures and temperatures, it is presently well known that life is similarly commonplace in the hostile environments of the deep seas as well as around hydrothermal vents. It is thus imperative to understand how key biological processes perform under extreme conditions of high pressures and temperatures. Herein, comparative steady-state and picosecond time-resolved spectroscopic studies were performed on membrane-bound and detergent-purified forms of a YM210W mutant reaction center (RC) from Rhodobacter sphaeroides under modulating conditions of high hydrostatic pressure applied at ambient temperature. A previously established breakage of the lone hydrogen bond formed between the RC primary donor and the protein scaffold was shown to take place in the membrane-bound RC at an almost 3 kbar higher pressure than in the purified RC, confirming the stabilizing role of the lipid environment for membrane proteins. The main change in the multi-exponential decay of excited primary donor emission across the experimental 10 kbar pressure range involved an over two-fold continuous acceleration, the kinetics becoming increasingly mono-exponential. The fastest component of the emission decay, thought to be largely governed by the rate of primary charge separation, was distinctly slower in the membrane-bound RC than in the purified RC. The change in character of the emission decay with pressure was explained by the contribution of charge recombination to emission decreasing with pressure as a result of an increasing free energy gap between the charge-separated and excited primary donor states. Finally, it was demonstrated that, in contrast to a long-term experimental paradigm, adding a combination of sodium ascorbate and phenazine methosulfate to the protein solution potentially distorts natural photochemistry in bacterial RCs.
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Affiliation(s)
- Kõu Timpmann
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu, 50411, Estonia
| | - Erko Jalviste
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu, 50411, Estonia
| | - Manoop Chenchiliyan
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu, 50411, Estonia
| | - Liina Kangur
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu, 50411, Estonia
| | - Michael R Jones
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu, 50411, Estonia.
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu, 51010, Estonia.
- Estonian Academy of Sciences, Kohtu 6, Tallinn, 10130, Estonia.
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Jalviste E, Timpmann K, Chenchiliyan M, Kangur L, Jones MR, Freiberg A. High-Pressure Modulation of Primary Photosynthetic Reactions. J Phys Chem B 2020; 124:718-726. [PMID: 31917566 DOI: 10.1021/acs.jpcb.9b09342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemical charge separation is key to biological solar energy conversion. Although many features of this highly quantum-efficient process have been described, others remain poorly understood. Herein, ultrafast fluorescence barospectroscopy is used for the first time to obtain insights into the mechanism of primary charge separation in a YM210W mutant bacterial reaction center under novel surrounding modulating conditions. Over a range of applied hydrostatic pressures reaching 10 kbar, the rate of primary charge separation monotonously increased and that of the electron transfer to secondary acceptor decreased. While the inferred free energy gap for charge separation generally narrowed with increasing pressure, a pressure-induced break of a protein-cofactor hydrogen bond observed at ∼2 kbar significantly (by 219 cm-1 or 27 meV) increased this gap, resulting in a drop in fluorescence. The findings strongly favor a model for primary charge separation that incorporates charge recombination and restoration of the excited primary pair state, over a purely sequential model. We show that the main reason for the almost threefold acceleration of the primary electron transfer rate is the pressure-induced increase of the electronic coupling energy, rather than a change of activation energy. We also conclude that across all applied pressures, the primary electron transfer in the mutant reaction center studied can be considered nonadiabatic, normal region, and thermally activated.
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Affiliation(s)
- Erko Jalviste
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Kõu Timpmann
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Manoop Chenchiliyan
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Liina Kangur
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Michael R Jones
- School of Biochemistry , University of Bristol , Biomedical Sciences Building, University Walk , Bristol BS8 1TD , U.K
| | - Arvi Freiberg
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia.,Institute of Molecular and Cell Biology , University of Tartu , Riia 23 , Tartu 51010 , Estonia.,Estonian Academy of Sciences , Kohtu 6 , 10130 Tallinn , Estonia
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Li X, Maindan K, Deria P. Metal-Organic Frameworks-Based Electrocatalysis: Insight and Future Perspectives. COMMENT INORG CHEM 2018. [DOI: 10.1080/02603594.2018.1545225] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Xinlin Li
- Department of Chemistry, Southern Illinois University, Carbondale, Illinois, USA
| | - Karan Maindan
- Department of Chemistry, Southern Illinois University, Carbondale, Illinois, USA
| | - Pravas Deria
- Department of Chemistry, Southern Illinois University, Carbondale, Illinois, USA
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Hua C, Doheny PW, Ding B, Chan B, Yu M, Kepert CJ, D'Alessandro DM. Through-Space Intervalence Charge Transfer as a Mechanism for Charge Delocalization in Metal-Organic Frameworks. J Am Chem Soc 2018; 140:6622-6630. [PMID: 29727176 DOI: 10.1021/jacs.8b02638] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the nature of charge transfer mechanisms in 3-dimensional metal-organic frameworks (MOFs) is an important goal owing to the possibility of harnessing this knowledge to design electroactive and conductive frameworks. These materials have been proposed as the basis for the next generation of technological devices for applications in energy storage and conversion, including electrochromic devices, electrocatalysts, and battery materials. After nearly two decades of intense research into MOFs, the mechanisms of charge transfer remain relatively poorly understood, and new strategies to achieve charge mobility remain elusive and challenging to experimentally explore, validate, and model. We now demonstrate that aromatic stacking interactions in Zn(II) frameworks containing cofacial thiazolo[5,4- d]thiazole (TzTz) units lead to a mixed-valence state upon electrochemical or chemical reduction. This through-space intervalence charge transfer (IVCT) phenomenon represents a new mechanism for charge transfer in MOFs. Computational modeling of the optical data combined with application of Marcus-Hush theory to the IVCT bands for the mixed-valence framework has enabled quantification of the degree of charge transfer using both in situ and ex situ electro- and spectro-electrochemical methods. A distance dependence for the through-space electron transfer has also been identified on the basis of experimental studies and computational calculations. This work provides a new window into electron transfer phenomena in 3-dimensional coordination space, of relevance to electroactive MOFs where new mechanisms for charge transfer are highly sought after, and to understanding biological light-harvesting systems where through-space mixed-valence interactions are operative.
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Affiliation(s)
- Carol Hua
- School of Chemistry , The University of Sydney , New South Wales 2006 , Australia
| | - Patrick W Doheny
- School of Chemistry , The University of Sydney , New South Wales 2006 , Australia
| | - Bowen Ding
- School of Chemistry , The University of Sydney , New South Wales 2006 , Australia
| | - Bun Chan
- Graduate School of Engineering , Nagasaki University , Nagasaki 852-8521 , Japan
| | - Michelle Yu
- School of Chemistry , The University of Sydney , New South Wales 2006 , Australia
| | - Cameron J Kepert
- School of Chemistry , The University of Sydney , New South Wales 2006 , Australia
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Kangur L, Jones MR, Freiberg A. Hydrogen bonds in the vicinity of the special pair of the bacterial reaction center probed by hydrostatic high-pressure absorption spectroscopy. Biophys Chem 2017; 231:27-33. [PMID: 28438349 DOI: 10.1016/j.bpc.2017.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 04/06/2017] [Accepted: 04/06/2017] [Indexed: 10/19/2022]
Abstract
Using the native bacteriochlorophyll a pigment cofactors as local probes, we investigated the response to external hydrostatic high pressure of reaction center membrane protein complexes from the photosynthetic bacterium Rhodobacter sphaeroides. Wild-type and engineered complexes were used with a varied number (0, 1 or 2) of hydrogen bonds that bind the reaction center primary donor bacteriochlorophyll cofactors to the surrounding protein scaffold. A pressure-induced breakage of hydrogen bonds was established for both detergent-purified and membrane-embedded reaction centers, but at rather different pressures: between 0.2 and 0.3GPa and at about 0.55GPa, respectively. The free energy change associated with the rupture of the single hydrogen bond present in wild-type reaction centers was estimated to be equal to 13-14kJ/mol. In the mutant with two symmetrical hydrogen bonds (FM197H) a single cooperative rupture of the two bonds was observed corresponding to an about twice stronger bond, rather than a sequential rupture of two individual bonds.
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Affiliation(s)
- Liina Kangur
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, United Kingdom
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia; Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia.
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Etinski M, Petković M, Ristić MM, Marian CM. Electron–Vibrational Coupling and Fluorescence Spectra of Tetra-, Penta-, and Hexacoordinated Chlorophylls c1 and c2. J Phys Chem B 2015; 119:10156-69. [DOI: 10.1021/acs.jpcb.5b05079] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mihajlo Etinski
- Faculty
of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Milena Petković
- Faculty
of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Miroslav M. Ristić
- Faculty
of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Christel M. Marian
- Institute
of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätsstrasse
1, D-40225 Düsseldorf, Germany
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Liu WL, Zheng ZR, Zhang JP, Wu WZ, Li AH, Zhang W, Huo MM, Liu ZG, Zhu RB, Zhao LC, Su WH. White-light continuum probed femtosecond time-resolved absorption spectroscopic measurement of β-carotene under high pressure. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.02.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Rätsep M, Cai ZL, Reimers JR, Freiberg A. Demonstration and interpretation of significant asymmetry in the low-resolution and high-resolution Qy fluorescence and absorption spectra of bacteriochlorophyll a. J Chem Phys 2011; 134:024506. [DOI: 10.1063/1.3518685] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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