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Kirchberg H, Thorwart M, Nitzan A. Charge Transfer through Redox Molecular Junctions in Nonequilibrated Solvents. J Phys Chem Lett 2020; 11:1729-1737. [PMID: 32046482 DOI: 10.1021/acs.jpclett.0c00118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Molecular conduction operating in dielectric solvent environments is often described using kinetic rates based on the Marcus theory of electron transfer at a molecule-metal electrode interface. However, the successive nature of charge transfer in such a system implies that the solvent does not necessarily reach equilibrium in such processes. Here we generalize the theory to account for solvent nonequilibrium and consider a molecular junction consisting of an electronic donor-acceptor system coupled to two metallic electrodes and placed in a polarizable solvent. We determine the nonequilbrium distribution of the solvent by solving diffusion equations in the strong- and weak-friction limits and calculate the charge current and its fluctuating behavior. In extreme limits, the absence of the solvent or fast solvent relaxation, the charge-transfer statistics is Poissonian, while it becomes correlated by the dynamic solvent between these limits. A Kramers-like turnover of the nonequilibrium current as a function of the solvent damping is found. Finally, we propose a way to tune the solvent-induced damping using geometrical control of the solvent dielectric response in nanostructured solvent channels.
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Affiliation(s)
- Henning Kirchberg
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany
| | - Michael Thorwart
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States of America
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Kim K, Singstock NR, Childress KK, Sinha J, Salazar AM, Whitfield SN, Holder AM, Stansbury JW, Musgrave CB. Rational Design of Efficient Amine Reductant Initiators for Amine-Peroxide Redox Polymerization. J Am Chem Soc 2019; 141:6279-6291. [PMID: 30915845 DOI: 10.1021/jacs.8b13679] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amine-peroxide redox polymerization (APRP) has been highly prevalent in industrial and medical applications since the 1950s, yet the initiation mechanism of this radical polymerization process is poorly understood so that innovations in the field are largely empirically driven and incremental. Through a combination of computational prediction and experimental analysis, we elucidate the mechanism of this important redox reaction between amines and benzoyl peroxide for the ambient production of initiating radicals. Our calculations show that APRP proceeds through SN2 attack by the amine on the peroxide but that homolysis of the resulting intermediate is the rate-determining step. We demonstrate a correlation between the computationally predicted initiating rate and the experimentally measured polymerization rate with an R2 = 0.80. The new mechanistic understanding was then applied to computationally predict amine reductant initiators with faster initiating kinetics. This led to our discovery of N-(4-methoxyphenyl)pyrrolidine (MPP) as amine reductant, which we confirmed significantly outperforms current state-of-the-art tertiary aromatic amines by ∼20-fold, making it the most efficient amine-peroxide redox initiator to date. The application of amines with superior kinetics such as MPP in APRP could greatly accelerate existing industrial processes, facilitate new industrial manufacturing methods, and improve biocompatibility in biomedical applications conducted with reduced initiator concentrations yet higher overall efficiency.
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Affiliation(s)
| | | | | | | | | | | | - Aaron M Holder
- National Renewable Energy Laboratory, Golden , Colorado 80401 , United States
| | - Jeffrey W Stansbury
- School of Dental Medicine, Craniofacial Biology , University of Colorado Denver , Aurora , Colorado 80045 , United States
| | - Charles B Musgrave
- National Renewable Energy Laboratory, Golden , Colorado 80401 , United States
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Kurzynski M, Chelminiak P. Temperature and detection-wavelength dependence of the electron transfer rates in initial stages of photosynthesis. J Phys Chem B 2013; 117:12339-46. [PMID: 24000808 DOI: 10.1021/jp402344j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Unusual temperature behavior, observed in the initial electron transfer stages in the photosynthetic reaction centers of the purple bacteria, and a strong probing pulse wavelength dependence of transfer rates, determined in transient absorption spectroscopy, can easily be explained on assuming that the transfer takes place from dynamically unrelaxed states of protein environment. The transitions from the primary special pair (P) to a single bacteriochlorophyll (B) and next to a bacteriopheophytin (H) are controlled by diffusion down the energy value of underdamped vibrational modes of frequency 200 K, probably determining distances between the succeeding cofactors. The subsequent transition to the quinone A (Q) is controlled by diffusion in the position value of an overdamped conformational mode, probably corresponding to the local polarization. From the fit of available experimental data to simple theoretical formulas, the important physical conclusion arises that the very electronic transitions are fast as compared to the relaxation processes and, in the first approximation, only the latter contribute to the overall times of the initial electron transfer stages in photosynthesis.
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Affiliation(s)
- Michal Kurzynski
- Faculty of Physics, Adam Mickiewicz University , Umultowska 85, 61-614 Poznan, Poland
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Kundu P, Dua A. Protein dynamics modulated electron transfer kinetics in early stage photosynthesis. J Chem Phys 2013; 138:045104. [DOI: 10.1063/1.4789346] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Chakrabarti S, Liu M, Waldeck DH, Oliver AM, Paddon-Row MN. Solvent Dynamical Effects on Electron Transfer in U-Shaped Donor-Bridge-Acceptor Molecules. J Phys Chem A 2009; 113:1040-8. [DOI: 10.1021/jp807412c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Subhasis Chakrabarti
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Min Liu
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - David H. Waldeck
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Anna M. Oliver
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
| | - Michael N. Paddon-Row
- Chemistry Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA, and School of Chemistry, University of New South Wales, Sydney NSW 2052 Australia
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Mechanism of Charge Separation in Purple Bacterial Reaction Centers. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_19] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Wang H, Lin S, Katilius E, Laser C, Allen JP, Williams JC, Woodbury NW. Unusual Temperature Dependence of Photosynthetic Electron Transfer due to Protein Dynamics. J Phys Chem B 2008; 113:818-24. [DOI: 10.1021/jp807468c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Haiyu Wang
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - Su Lin
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - Evaldas Katilius
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - Christa Laser
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - James P. Allen
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - JoAnn C. Williams
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - Neal W. Woodbury
- The Biodesign Institute at Arizona State University, 1001 South McAllister Avenue, Tempe, Arizona 85287-5201, and The Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
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Chaudhury S, Cherayil BJ. Modulation of electron transfer kinetics by protein conformational fluctuations during early-stage photosynthesis. J Chem Phys 2007; 127:145103. [DOI: 10.1063/1.2783845] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Parra-Barraza H, Burboa MG, Sánchez-Vázquez M, Juárez J, Goycoolea FM, Valdez MA. Chitosan−Cholesterol and Chitosan−Stearic Acid Interactions at the Air−Water Interface. Biomacromolecules 2005; 6:2416-26. [PMID: 16153076 DOI: 10.1021/bm050106s] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report in this work the isotherms of cholesterol and stearic acid at the air-water interface modified by different chitosans (chitosan chloride, hydrophobic modified chitosan, and medium and high molecular weight chitosans) in the aqueous subphase. The Langmuir-Blodgett films of the complexes cholesterol-chitosan and stearic acid-chitosan are analyzed by atomic force microscopy (AFM), and a molecular simulation was performed to visualize the chitosan-lipid interactions. Strong modifications are obtained in the isotherms as a result of the chitosan interactions with cholesterol and stearic acid at the air-water interface. These modifications were dependent on the type and concentration of chitosan. Severe modifications of all phases were noticed with larger molecular areas, and the observed changes in the compressional modulus were dependent on the type of chitosan used. The complexes of chitosan-stearic acid were more flexible than the ones of chitosan-cholesterol. The AFM images demonstrated that chitosan was disaggregated by the cholesterol and stearic acid interactions producing more homogeneous surfaces in some cases. The hydrophobic chitosan showed more affinity with stearic acid, while both medium and high molecular weight chitosans produced homogeneous surfaces with cholesterol. The simulated chitosan chains interacting with cholesterol and stearic acid demonstrated the possibility of specific sites of electrostatic bonds between these molecules. Adsorption of cholesterol on the different powdered chitosans, performed by HPLC, showed that the medium and high molecular weight chitosans could retain higher proportions of cholesterol compared with the other analyzed samples.
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Affiliation(s)
- Hilda Parra-Barraza
- Departamento de Investigación en Materiales, Universidad de Sonora, Rosales y transversal, C. P. 83000 Hermosillo, Sonora, México
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