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Rummel L, Domanski MHJ, Hausmann H, Becker J, Schreiner PR. London Dispersion Favors Sterically Hindered Diarylthiourea Conformers in Solution. Angew Chem Int Ed Engl 2022; 61:e202204393. [PMID: 35544611 PMCID: PMC9401023 DOI: 10.1002/anie.202204393] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Indexed: 12/12/2022]
Abstract
We present an experimental and computational study on the conformers of N,N'-diphenylthiourea substituted with different dispersion energy donor (DED) groups. While the unfolded anti-anti conformer is the most relevant for thiourea catalysis, intramolecular noncovalent interactions counterintuitively favor the folded syn-syn conformer, as evident from a combination of low-temperature nuclear magnetic resonance measurements and computations. In order to quantify the noncovalent interactions, we utilized local energy decomposition analysis and symmetry-adapted perturbation theory at the DLPNO-CCSD(T)/def2-TZVPP and sSAPT0/6-311G(d,p) levels of theory. Additionally, we applied a double-mutant cycle to experimentally study the effects of bulky substituents on the equilibria. We determined London dispersion as the key interaction that shifts the equilibria towards the syn-syn conformers. This preference is likely a factor why such thiourea derivatives can be poor catalysts.
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Affiliation(s)
- Lars Rummel
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Marvin H J Domanski
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Heike Hausmann
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Jonathan Becker
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Peter R Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
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2
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El Khoury Y, Van Wilderen LJGW, Bredenbeck J. Ultrafast 2D-IR spectroelectrochemistry of flavin mononucleotide. J Chem Phys 2016; 142:212416. [PMID: 26049436 DOI: 10.1063/1.4916916] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We demonstrate the coupling of ultrafast two-dimensional infrared (2D-IR) spectroscopy to electrochemistry in solution and apply it to flavin mononucleotide, an important cofactor of redox proteins. For this purpose, we designed a spectroelectrochemical cell optimized for 2D-IR measurements in reflection and measured the time-dependent 2D-IR spectra of the oxidized and reduced forms of flavin mononucleotide. The data show anharmonic coupling and vibrational energy transfer between different vibrational modes in the two redox species. Such information is inaccessible with redox-controlled steady-state FTIR spectroscopy. The wide range of applications offered by 2D-IR spectroscopy, such as sub-picosecond structure determination, IR band assignment via energy transfer, disentangling reaction mixtures through band connectivity in the 2D spectra, and the measurement of solvation dynamics and chemical exchange can now be explored under controlled redox potential. The development of this technique furthermore opens new horizons for studying the dynamics of redox proteins.
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Affiliation(s)
- Youssef El Khoury
- Institut für Biophysik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Luuk J G W Van Wilderen
- Institut für Biophysik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Jens Bredenbeck
- Institut für Biophysik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
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Alachraf MW, Wende RC, Schuler SMM, Schreiner PR, Schrader W. Functionality, Effectiveness, and Mechanistic Evaluation of a Multicatalyst‐Promoted Reaction Sequence by Electrospray Ionization Mass Spectrometry. Chemistry 2015; 21:16203-8. [DOI: 10.1002/chem.201502640] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 12/24/2022]
Affiliation(s)
- M. Wasim Alachraf
- Max‐Planck Institut für Kohlenforschung, Kaiser Wilhelm Platz 1, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208‐306‐2982
| | - Raffael C. Wende
- Institute of Organic Chemistry, Justus‐Liebig University Giessen, Heinrich‐Buff‐Ring 17, 35392 Giessen (Germany)
| | - Sören M. M. Schuler
- Institute of Organic Chemistry, Justus‐Liebig University Giessen, Heinrich‐Buff‐Ring 17, 35392 Giessen (Germany)
| | - Peter R. Schreiner
- Institute of Organic Chemistry, Justus‐Liebig University Giessen, Heinrich‐Buff‐Ring 17, 35392 Giessen (Germany)
| | - Wolfgang Schrader
- Max‐Planck Institut für Kohlenforschung, Kaiser Wilhelm Platz 1, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208‐306‐2982
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van Wilderen LJGW, Bredenbeck J. Von ultraschnellen Strukturbestimmungen bis zum Steuern von Reaktionen: mehrdimensionale gemischte IR/nicht-IR-Schwingungsspektroskopie. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201503155] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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van Wilderen LJGW, Bredenbeck J. From Ultrafast Structure Determination to Steering Reactions: Mixed IR/Non-IR Multidimensional Vibrational Spectroscopies. Angew Chem Int Ed Engl 2015; 54:11624-40. [PMID: 26394274 DOI: 10.1002/anie.201503155] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Indexed: 12/27/2022]
Abstract
Ultrafast multidimensional infrared spectroscopy is a powerful method for resolving features of molecular structure and dynamics that are difficult or impossible to address with linear spectroscopy. Augmenting the IR pulse sequences by resonant or nonresonant UV, Vis, or NIR pulses considerably extends the range of application and creates techniques with possibilities far beyond a pure multidimensional IR experiment. These include surface-specific 2D-IR spectroscopy with sub-monolayer sensitivity, ultrafast structure determination in non-equilibrium systems, triggered exchange spectroscopy to correlate reactant and product bands, exploring the interplay of electronic and nuclear degrees of freedom, investigation of interactions between Raman- and IR-active modes, imaging with chemical contrast, sub-ensemble-selective photochemistry, and even steering a reaction by selective IR excitation. We give an overview of useful mixed IR/non-IR pulse sequences, discuss their differences, and illustrate their application potential.
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Affiliation(s)
| | - Jens Bredenbeck
- Institute of Biophysics, Johann Wolfgang Goethe-University, Frankfurt am Main (Germany).
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Kiefer LM, King JT, Kubarych KJ. Dynamics of rhenium photocatalysts revealed through ultrafast multidimensional spectroscopy. Acc Chem Res 2015; 48:1123-30. [PMID: 25839193 DOI: 10.1021/ar500402r] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Rhenium catalysts have shown promise to promote carbon neutrality by reducing a prominent greenhouse gas, CO2, to CO and other starting materials. Much research has focused on identifying intermediates in the photocatalysis mechanism as well as time scales of relevant ultrafast processes. Recent studies have implemented multidimensional spectroscopies to characterize the catalyst's ultrafast dynamics as it undergoes the many steps of its photocycle. Two-dimensional infrared (2D-IR) spectroscopy is a powerful method to obtain molecular structure information while extracting time scales of dynamical processes with ultrafast resolution. Many observables result from 2D-IR experiments including vibrational lifetimes, intramolecular redistribution time scales, and, unique to 2D-IR, spectral diffusion, which is highly sensitive to solute-solvent interactions and motional dynamics. Spectral diffusion, a measure of how long a vibrational mode takes to sample its frequency space due to multiple solvent configurations, has various contributing factors. Properties of the solvent, the solute's structural flexibility, and electronic properties, as well as interactions between the solvent and solute, complicate identifying the origin of the spectral diffusion. With carefully chosen experiments, however, the source of the spectral diffusion can be unveiled. Within the context of a considerable body of previous work, here we discuss the spectral diffusion of several rhenium catalysts at multiple stages in the catalysis. These studies were performed in multiple polar liquids to aid in discovering the contributions of the solvent. We also performed electronic ground state 2D-IR and electronic excited state transient-2D-IR experiments to observe how spectral diffusion changes upon electronic excitation. Our results indicate that with the original Lehn catalyst in THF, relative to the ground state, the spectral diffusion slows by a factor of 3 in the equilibrated triplet metal-to-ligand charge transfer state. We attribute this slowdown to a decrease in dielectric friction as well as an increase in molecular flexibility. It is possible to partially simulate the charge transfer by altering the electron density moderately by adding electron donating or withdrawing substituents symmetrically to the bipyridine ligand. We find that unlike the significant electronic structure change induced by MLCT, such small substituent effects do not influence the spectral diffusion. A solvent study in THF, DMSO, and CH3CN found there to be an explicit solvent dependence that we can correlate to the solvent donicity, which is a measure of its nucleophilicity. Future studies focused on the solvent effects on spectral diffusion in the crucial photoinitiated state can illuminate the role the solvent plays in the catalysis.
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Affiliation(s)
- Laura M. Kiefer
- Department of Chemistry, University of Michigan, 930 N. University
Ave., Ann Arbor, Michigan 48109, United States
| | - John T. King
- Department of Chemistry, University of Michigan, 930 N. University
Ave., Ann Arbor, Michigan 48109, United States
| | - Kevin J. Kubarych
- Department of Chemistry, University of Michigan, 930 N. University
Ave., Ann Arbor, Michigan 48109, United States
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Georgieva MK, Santos AG. A computational study on Lewis acid-catalyzed diastereoselective acyclic radical allylation reactions with unusual selectivity dependence on temperature and epimer precursor. J Org Chem 2014; 79:11483-95. [PMID: 25375894 DOI: 10.1021/jo502102s] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In stereoselective radical reactions, it is accepted that the configuration of the radical precursor has no impact on the levels of stereoinduction, as a prochiral radical intermediate is planar, with two identical faces, independently of its origin. However, Sibi and Rheault (J. Am. Chem. Soc. 2000, 122, 8873-8879) remarkably obtained different selectivities in the trapping of radicals originated from two epimeric bromides, catalyzed by chelating Lewis acids. The selectivity rationalization was made on the basis of different conformational properties of each epimer. However, in this paper we show that the two epimers have similar conformational properties, which implies that the literature proposal is unable to explain the experimental results. We propose an alternative mechanism, in which the final selectivity is dependent on different reaction rates for radical formation from each epimer. By introducing a different perspective of the reaction mechanism, our model also allows the rationalization of different chemical yields obtained from each epimer, a result not rationalized by the previous model. Adaptation to other radical systems, under different reaction conditions, is also possible.
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Affiliation(s)
- Miglena K Georgieva
- REQUIMTE, CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova Lisboa , 2829-516 Caparica, Portugal
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Panman MR, Vos J, Bocokić V, Bellini R, de Bruin B, Reek JHN, Woutersen S. Exchanging conformations of a hydroformylation catalyst structurally characterized using two-dimensional vibrational spectroscopy. Inorg Chem 2013; 52:14294-8. [PMID: 24256078 DOI: 10.1021/ic402254q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Catalytic transition-metal complexes often occur in several conformations that exchange rapidly (<ms) in solution so that their spatial structures are difficult to characterize with conventional methods. Here, we determine specific bond angles in the two rapidly exchanging solution conformations of the hydroformylation catalyst (xantphos)Rh(CO)2H using two-dimensional vibrational spectroscopy, a method that can be applied to any catalyst provided that the exchange between its conformers occurs on a time scale of a few picoseconds or slower. We find that, in one of the conformations, the OC-Rh-CO angle deviates significantly from the canonical value in a trigonal-bipyramidal structure. On the basis of complementary density functional calculations, we ascribe this effect to attractive van der Waals interaction between the CO and the xantphos ligand.
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Affiliation(s)
- Matthijs R Panman
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
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Messmer AT, Lippert KM, Schreiner PR, Bredenbeck J. Structure analysis of substrate catalyst complexes in mixtures with ultrafast two-dimensional infrared spectroscopy. Phys Chem Chem Phys 2013; 15:1509-17. [PMID: 23238288 DOI: 10.1039/c2cp42863f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The understanding of reaction mechanisms requires structure elucidation of short-lived intermediates, even in the presence of other, similar structures. Here we show that polarization dependent two-dimensional infrared spectroscopy is a powerful method to determine the structure of molecules that participate in fast equilibria, in a regime where standard techniques such as nuclear magnetic resonance spectroscopy are beyond their limits. Using catalyst-substrate complexes in a Lewis acid catalyzed enantioselective Diels-Alder reaction as an example we present two methods that allow the resolution of molecular structure in mixtures even when the spectroscopic signals partially overlap. The structures of N-crotonyloxazolidin-2-one, a reactant carrying the Evans auxiliary, and its complex with the Lewis acid SnCl(4) were determined in a mixture as used under the typical reaction conditions. In addition to the chelate that mainly forms, three additional substrate-catalyst complexes were detected and could be tentatively assigned. Observation of minor complex conformers suggests a rationale for the observed diastereoselectivity of the reaction using SnCl(4) as compared to other Lewis acids. Knowledge about additional species may lead to a better understanding of the different selectivities for various Lewis acids and allow reaction optimization.
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Affiliation(s)
- Andreas T Messmer
- Institute of Biophysics, Johann Wolfgang Goethe-University, Max-von-Laue-Str. 1, 60438 Frankfurt, Germany
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Messmer AT, Steinwand S, Lippert KM, Schreiner PR, Bredenbeck J. Ultrafast Two-Dimensional Infrared Spectroscopy Resolves the Conformational Change of an Evans Auxiliary Induced by Mg(ClO4)2. J Org Chem 2012. [DOI: 10.1021/jo302160s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andreas T. Messmer
- Institute of Biophysics, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse
1, 60438 Frankfurt, Germany
| | - Sabrina Steinwand
- Institute of Biophysics, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse
1, 60438 Frankfurt, Germany
| | - Katharina M. Lippert
- Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392
Giessen, Germany
| | - Peter R. Schreiner
- Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392
Giessen, Germany
| | - Jens Bredenbeck
- Institute of Biophysics, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse
1, 60438 Frankfurt, Germany
- CEF-MC, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse 9, 60438
Frankfurt, Germany
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