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Crum VF, Kubarych KJ. Nanoclustering in non-ideal ethanol/heptane solutions alters solvation dynamics. J Chem Phys 2024; 161:044507. [PMID: 39056386 DOI: 10.1063/5.0216746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Accepted: 07/02/2024] [Indexed: 07/28/2024] Open
Abstract
Alcohol/alkane solutions widely used in chemical synthesis and as transportation fuels are highly non-ideal due to the nanoscale clustering of the amphiphilic alcohol molecules within the nonpolar alkanes. Besides impacting reactivity, such as combustion, non-ideal solutions are likely to exhibit unusual solvation dynamics on ultrafast time scales arising from the structurally heterogeneous nature of molecular-scale association. Using a convenient transition metal carbonyl vibrational probe [(C5H5)Mn(CO)3, CMT], linear absorption and nonlinear two-dimensional infrared (2D-IR) spectroscopy reveal composition-dependent solvation dynamics as reported by the frequency fluctuation correlation function in a series of ethanol/heptane solutions. Slow spectral diffusion with dilute ethanol indicates preferential solvation of the polar solute by the alcohol with a mechanism largely dominated by solvent exchange. Comparison with an ethanol/acetonitrile solution series yields no substantial preferential solvation or solvent exchange signatures in the linear or 2D-IR spectra. In ethanol/heptane solutions, increasing the ethanol concentration speeds up the solvation dynamics, which is largely consistent with a model that includes solvent exchange and single-solvent spectral diffusion. Detailed analysis of the deviation from the experimental time constants from the model's optimal parameters yields a remarkable resemblance of the concentration-weighted Kirkwood-Buff integrals for ethanol/heptane solutions. This trend indicates that solution non-ideality alters the spectral diffusion dynamics of the probe solute. Given that nanoscale clustering drives the non-ideality, these experiments reveal a dynamical consequence of nanoscale heterogeneity on the ultrafast dynamics of the solution. Refined understanding of the structural and dynamical aspects of mixed solvents will be necessary for predictive solution strategies in chemistry.
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Affiliation(s)
- Vivian F Crum
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, USA
| | - Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, USA
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Hill TD, Basnet S, Lepird HH, Rightnowar BW, Moran SD. Anisotropic dynamics of an interfacial enzyme active site observed using tethered substrate analogs and ultrafast 2D IR spectroscopy. J Chem Phys 2023; 159:165101. [PMID: 37870142 PMCID: PMC10597647 DOI: 10.1063/5.0167991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Accepted: 09/29/2023] [Indexed: 10/24/2023] Open
Abstract
Enzymes accelerate the rates of biomolecular reactions by many orders of magnitude compared to bulk solution, and it is widely understood that this catalytic effect arises from a combination of polar pre-organization and electrostatic transition state stabilization. A number of recent reports have also implicated ultrafast (femtosecond-picosecond) timescale motions in enzymatic activity. However, complications arising from spatially-distributed disorder, the occurrence of multiple substrate binding modes, and the influence of hydration dynamics on solvent-exposed active sites still confound many experimental studies. Here we use ultrafast two-dimensional infrared (2D IR) spectroscopy and covalently-tethered substrate analogs to examine dynamical properties of the promiscuous Pyrococcus horikoshii ene-reductase (PhENR) active site in two binding configurations mimicking proposed "inactive" and "reactive" Michaelis complexes. Spectral diffusion measurements of aryl-nitrile substrate analogs reveal an end-to-end tradeoff between fast (sub-ps) and slow (>5 ps) motions. Fermi resonant aryl-azide analogs that sense interactions of coupled oscillators are described. Lineshape and quantum beat analyses of these probes reveal characteristics that correlate with aryl-nitrile frequency fluctuation correlation functions parameters, demonstrating that this anisotropy is an intrinsic property of the water-exposed active site, where countervailing gradients of fast dynamics and disorder in the reactant ground state are maintained near the hydration interface. Our results suggest several plausible factors leading to state-selective rate enhancement and promiscuity in PhENR. This study also highlights a strategy to detect perturbations to vibrational modes outside the transparent window of the mid-IR spectrum, which may be extended to other macromolecular systems.
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Affiliation(s)
| | - Sunil Basnet
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, Illinois 62901, USA
| | - Hannah H. Lepird
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, Illinois 62901, USA
| | - Blaze W. Rightnowar
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, Illinois 62901, USA
| | - Sean D. Moran
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, Illinois 62901, USA
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Nimmrich A, Panman MR, Berntsson O, Biasin E, Niebling S, Petersson J, Hoernke M, Björling A, Gustavsson E, van Driel TB, Dohn AO, Laursen M, Zederkof DB, Tono K, Katayama T, Owada S, Nielsen MM, Davidsson J, Uhlig J, Hub JS, Haldrup K, Westenhoff S. Solvent-Dependent Structural Dynamics in the Ultrafast Photodissociation Reaction of Triiodide Observed with Time-Resolved X-ray Solution Scattering. J Am Chem Soc 2023. [PMID: 37163700 PMCID: PMC10375522 DOI: 10.1021/jacs.3c00484] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Resolving the structural dynamics of bond breaking, bond formation, and solvation is required for a deeper understanding of solution-phase chemical reactions. In this work, we investigate the photodissociation of triiodide in four solvents using femtosecond time-resolved X-ray solution scattering following 400 nm photoexcitation. Structural analysis of the scattering data resolves the solvent-dependent structural evolution during the bond cleavage, internal rearrangements, solvent-cage escape, and bond reformation in real time. The nature and structure of the reaction intermediates during the recombination are determined, elucidating the full mechanism of photodissociation and recombination on ultrafast time scales. We resolve the structure of the precursor state for recombination as a geminate pair. Further, we determine the size of the solvent cages from the refined structures of the radical pair. The observed structural dynamics present a comprehensive picture of the solvent influence on structure and dynamics of dissociation reactions.
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Affiliation(s)
- Amke Nimmrich
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Matthijs R Panman
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Oskar Berntsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Elisa Biasin
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Stephan Niebling
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Jonas Petersson
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, 75120 Uppsala, Sweden
| | - Maria Hoernke
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Alexander Björling
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Emil Gustavsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Tim B van Driel
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Asmus O Dohn
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
- Faculty of Physical Sciences, University of Iceland, VR-III, 107 Reykjavík, Iceland
| | - Mads Laursen
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Diana B Zederkof
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Tetsuo Katayama
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Shigeki Owada
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Martin M Nielsen
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Jan Davidsson
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, 75120 Uppsala, Sweden
| | - Jens Uhlig
- Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden
| | - Jochen S Hub
- Georg-August-Universität Göttingen, Institute for Microbiology and Genetics, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Kristoffer Haldrup
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Sebastian Westenhoff
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
- Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden
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Kubarych KJ, Thielges MC, Tahara T, Elsaesser T. Special issue on time-resolved vibrational spectroscopy. J Chem Phys 2023; 158:2887209. [PMID: 37114706 DOI: 10.1063/5.0147807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 03/01/2023] [Indexed: 04/29/2023] Open
Affiliation(s)
- Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Abor, Michigan 48109, USA
| | - Megan C Thielges
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, Indiana 47405, USA
| | - Tahei Tahara
- RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Leong TX, Collins BK, Dey Baksi S, Mackin RT, Sribnyi A, Burin AL, Gladysz JA, Rubtsov IV. Tracking Energy Transfer across a Platinum Center. J Phys Chem A 2022; 126:4915-4930. [PMID: 35881911 PMCID: PMC9358659 DOI: 10.1021/acs.jpca.2c02017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
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Rigid, conjugated alkyne bridges serve as important components
in various transition-metal complexes used for energy conversion,
charge separation, sensing, and molecular electronics. Alkyne stretching
modes have potential for modulating charge separation in donor–bridge–acceptor
compounds. Understanding the rules of energy relaxation and energy
transfer across the metal center in such compounds can help optimize
their electron transfer switching properties. We used relaxation-assisted
two-dimensional infrared spectroscopy to track energy transfer across
metal centers in platinum complexes featuring a triazole-terminated
alkyne ligand of two or six carbons, a perfluorophenyl ligand, and
two tri(p-tolyl)phosphine ligands. Comprehensive
analyses of waiting-time dynamics for numerous cross and diagonal
peaks were performed, focusing on coherent oscillation, energy transfer,
and cooling parameters. These observables augmented with density functional
theory computations of vibrational frequencies and anharmonic force
constants enabled identification of different functional groups of
the compounds. Computations of vibrational relaxation pathways and
mode couplings were performed, and two regimes of intramolecular energy
redistribution are described. One involves energy transfer between
ligands via high-frequency modes; the transfer is efficient only if
the modes involved are delocalized over both ligands. The energy transport
pathways between the ligands are identified. Another regime involves
redistribution via low-frequency delocalized modes, which does not
lead to interligand energy transport.
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Affiliation(s)
- Tammy X Leong
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Brenna K Collins
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Sourajit Dey Baksi
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Robert T Mackin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Artem Sribnyi
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - John A Gladysz
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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