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Terry LM, Foreman MM, Weber JM. Effects of Anion Size, Shape, and Solvation in Binding of Nitrate to Octamethyl Calix[4]pyrrole. J Phys Chem Lett 2024:9481-9486. [PMID: 39254991 DOI: 10.1021/acs.jpclett.4c02347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
We present cryogenic ion vibrational spectroscopy of complexes of the anion receptor octamethyl calix[4]pyrrole (omC4P) with nitrate in vacuo. We compare the resulting vibrational spectrum with that in deuterated acetonitrile solution, and we interpret the results using density functional theory. Nitrate binds to omC4P through hydrogen bonds between the four NH groups of the receptor and a single NO group of the nitrate ion. The shape of the ion breaks the C4v symmetry of the receptor, and this symmetry lowering is encoded in the pattern of the NH stretching modes of omC4P. We compare the spectrum of nitrate-omC4P with that of chloride-omC4P to discuss effects of ion size, shape, and solvent interaction on the ion binding behavior.
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Affiliation(s)
- Lane M Terry
- JILA and Department of Chemistry, University of Colorado, 440 UCB, Boulder, Colorado 80309-0440, United States
| | - Madison M Foreman
- JILA and Department of Chemistry, University of Colorado, 440 UCB, Boulder, Colorado 80309-0440, United States
| | - J Mathias Weber
- JILA and Department of Chemistry, University of Colorado, 440 UCB, Boulder, Colorado 80309-0440, United States
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2
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Gorbachev V, Miloglyadova L, Chen P. An automatic variable laser power attenuator for continuous-wave quantum cascade lasers in cryogenic ion vibrational predissociation spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:093002. [PMID: 39240148 DOI: 10.1063/5.0189140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 08/13/2024] [Indexed: 09/07/2024]
Abstract
Cryogenic ion vibrational predissociation (CIVP) spectroscopy is an established and valuable technique for molecular elucidation in the gas phase. CIVP relies on tunable lasers, wherein among typical laser schemes, the application of mid-infrared continuous-wave quantum cascade laser (cw-QCL) is the most robust and elegant solution, as we have recently demonstrated. However, potential challenges arise from an inhomogeneous character across laser power tuning curves. A large laser power output could have undesired consequences, such as multiphoton absorption or saturation effects. Significant variations in laser power tuning curves could potentially alter the shape of the investigated band, particularly for diffuse bands. In this study, we have developed and introduced an automatic variable laser power attenuator designed to keep the laser power output uniform at a user-defined value across the entire available spectral range. We demonstrated the application of this attenuator in obtaining CIVP spectra of a model compound with a diffuse N-H-N band. This approach enhances the reliability of measuring diffuse bands and overall applicability of cw-QCL.
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Affiliation(s)
- Vladimir Gorbachev
- Laboratorium für Organische Chemie, Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
| | - Larisa Miloglyadova
- Laboratorium für Organische Chemie, Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
| | - Peter Chen
- Laboratorium für Organische Chemie, Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
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3
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Rummel L, Schreiner PR. Advances and Prospects in Understanding London Dispersion Interactions in Molecular Chemistry. Angew Chem Int Ed Engl 2024; 63:e202316364. [PMID: 38051426 DOI: 10.1002/anie.202316364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 12/03/2023] [Accepted: 12/05/2023] [Indexed: 12/07/2023]
Abstract
London dispersion (LD) interactions are the main contribution of the attractive part of the van der Waals potential. Even though LD effects are the driving force for molecular aggregation and recognition, the role of these omnipresent interactions in structure and reactivity had been largely underappreciated over decades. However, in the recent years considerable efforts have been made to thoroughly study LD interactions and their potential as a chemical design element for structures and catalysis. This was made possible through a fruitful interplay of theory and experiment. This review highlights recent results and advances in utilizing LD interactions as a structural motif to understand and utilize intra- and intermolecularly LD-stabilized systems. Additionally, we focus on the quantification of LD interactions and their fundamental role in chemical reactions.
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Affiliation(s)
- Lars Rummel
- Institute of Organic 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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4
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Tsybizova A, Fritsche L, Miloglyadova L, Kräutler B, Chen P. Cryogenic Ion Vibrational Predissociation (CIVP) Spectroscopy of Aryl Cobinamides in the Gas Phase: How Good Are the Calculations for Vitamin B 12 Derivatives? J Am Chem Soc 2023; 145:19561-19570. [PMID: 37656981 PMCID: PMC10510309 DOI: 10.1021/jacs.3c03001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Indexed: 09/03/2023]
Abstract
Aryl corrins represent a novel class of designed B12 derivatives with biological properties of "antivitamins B12". In our previous study, we experimentally determined bond strength in a series of aryl-corrins by the threshold collision-induced dissociation experiments (T-CID) and compared the measured bond dissociation energies (BDEs) with those calculated with density functional theory (DFT). We found that the BDEs are modulated by the side chains around the periphery of the corrin unit. Given that aryl cobinamides have many side chains that increase their conformational space and that the question of a specific structure, measured in the gas phase, was important for further evaluation of our T-CID experiment, we proceeded to analyze structural properties of aryl cobinamides using cryogenic ion vibrational predissociation (CIVP) spectroscopy, static DFT, and Born-Oppenheimer molecular dynamic (BOMD) simulations. We found that none of the examined DFT models could reproduce the CIVP spectra convincingly; both "static" DFT calculations and "dynamic" BOMD simulations provide a surprisingly poor representation of the vibrational spectra, specifically of the number, position, and intensity of bands assigned to hydrogen-bonded versus non-hydrogen-bonded NH and OH moieties. We conclude that, for a flexible molecule with ca. 150 atoms, more accurate approaches are needed before definitive conclusions about computed properties, specifically the structure of the ground-state conformer, may be made.
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Affiliation(s)
- Alexandra Tsybizova
- Laboratorium
für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Lukas Fritsche
- Laboratorium
für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Larisa Miloglyadova
- Laboratorium
für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Bernhard Kräutler
- Institute
of Organic Chemistry, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Peter Chen
- Laboratorium
für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
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5
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Gorbachev V, Nobile AG, Tsybizova A, Chen P. Probing Electronic Effects in Tridentate Copper(I) Complexes by CIVP Spectroscopy. Inorg Chem 2023; 62:14704-14714. [PMID: 37642404 DOI: 10.1021/acs.inorgchem.3c02065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Ligand electronic effects play an important role in catalysis, where small changes to ligand structure can bring about large changes in catalytic activity. Therefore, accurate experimental quantification of ligand electronic properties plays a crucial role in understanding and tuning chemical reactivity. In this work, we used cryogenic ion vibrational predissociation (CIVP) spectroscopy to experimentally quantify electronic effects in terpyridine ligands, as simple model systems, by measuring CIVP spectra of their copper complexes tagged by N2 molecules. We used the N2 stretching vibration as a reporter chromophore to probe electronic effects of the investigated ligands and employed quantum chemical calculations to better understand how different substituents influence the vibrational frequencies of the stretching vibration of the chromophore. Our data show that the electronic character, as well as position and number of substituents, can affect the N≡N vibrational frequency, and that the N≡N bond serves as a sensitive probe for electronic and steric effects.
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Affiliation(s)
| | | | | | - Peter Chen
- ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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6
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Quesada JV, Chmela J, Greisch JF, Klopper W, Harding ME. A litmus test for the balanced description of dispersion interactions and coordination chemistry of lanthanoids. Phys Chem Chem Phys 2022; 24:25106-25117. [PMID: 35920212 DOI: 10.1039/d2cp01414a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of long-range interactions on the structure of complexes of Eu(III) with four 9-hydroxy-phenalen-1-one ligands (HPLN) and one alkaline earth metal dication [Eu(PLN)4AE]+ (AE: Mg, Ca, Sr, and Ba) is analyzed. Through the [Eu(PLN)4Ca]+ complex, which is a charged complex with two metals-one of them a lanthanoid-and with four relatively fluxional π-ligands, the difficulties of describing such systems are identified. The inclusion of the D3(BJ) or D4 corrections to different density functionals introduces significant changes in the structure, which are shown to stem from the interaction between pairs of PLN ligands. This interaction is studied further with a variety of density functionals, wave-function based methods, and by means of the random phase approximation. By comparing the computed results with those from experimental evidence of gas-phase photoluminescence and ion mobility measurements it is concluded that the inclusion of dispersion corrections does not always yield structures that are in agreement with the experimental findings.
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Affiliation(s)
- Juana Vázquez Quesada
- Institut für Physikalische Chemie, Karlsruher Institut für Technologie (KIT), Campus Süd, Postfach 6980, D-76049 Karlsruhe, Germany.
| | - Jiří Chmela
- Institut für Physikalische Chemie, Karlsruher Institut für Technologie (KIT), Campus Süd, Postfach 6980, D-76049 Karlsruhe, Germany.
| | - Jean-François Greisch
- Institut für Nanotechnologie, Karlsruher Institut für Technologie (KIT), Campus Nord, Postfach 3640, D-76021 Karlsruhe, Germany.
| | - Wim Klopper
- Institut für Physikalische Chemie, Karlsruher Institut für Technologie (KIT), Campus Süd, Postfach 6980, D-76049 Karlsruhe, Germany. .,Institut für Nanotechnologie, Karlsruher Institut für Technologie (KIT), Campus Nord, Postfach 3640, D-76021 Karlsruhe, Germany.
| | - Michael E Harding
- Institut für Nanotechnologie, Karlsruher Institut für Technologie (KIT), Campus Nord, Postfach 3640, D-76021 Karlsruhe, Germany.
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7
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Gorbachev V, Tsybizova A, Miloglyadova L, Chen P. Increasing Complexity in a Conformer Space Step-by-Step: Weighing London Dispersion against Cation-π Interactions. J Am Chem Soc 2022; 144:9007-9022. [PMID: 35549249 DOI: 10.1021/jacs.2c01381] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We report an evaluation of the importance of London dispersion in moderately large (up to 36 heavy atoms) organic molecules by means of a molecular torsion balance whose conformations "weigh" one interaction against another in the absence of solvents. The experimental study, with gas-phase cryogenic ion vibrational predissociation (CIVP) spectroscopy, solid-state Fourier transfer infrared (FT-IR), and single-crystal X-ray crystallography, is accompanied by density functional theory calculations, including an extensive search and analysis of accessible conformations. We begin with the unsubstituted molecular torsion balance, and then step up the complexity systematically by adding alkyl groups incrementally as dispersion energy donors (DEDs) to achieve a degree of chemical complexity comparable to what is typically found in transition states for many regio- and stereoselective reactions in organic and organometallic chemistry. We find clear evidence for the small attractive contribution by DEDs, as had been reported in other studies, but we also find that small individual contributions by London dispersion, when they operate in opposition to other weak noncovalent interactions, produce composite effects on the structure that are difficult to predict intuitively, or by modern quantum chemical calculations. The experimentally observed structures, together with a reasonable value for a reference cation-π interaction, indicate that the pairwise interaction between two tert-butyl groups, in the best case, is modest. Moreover, the visualization of the conformational space, and comparison to spectroscopic indicators of the structure, as one steps up the complexity of the manifold of noncovalent interactions, makes clear that in silico predictive ability for the structure of moderately large, flexible, organic molecules falters sooner than one might have expected.
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Affiliation(s)
- Vladimir Gorbachev
- Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Alexandra Tsybizova
- Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Larisa Miloglyadova
- Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
| | - Peter Chen
- Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland
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8
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Gorbachev VM, Miloglyadova L, Tsybizova A, Chen P. Application of continuous wave quantum cascade laser in combination with CIVP spectroscopy for investigation of large organic and organometallic ions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:083002. [PMID: 34470415 DOI: 10.1063/5.0058625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 07/24/2021] [Indexed: 06/13/2023]
Abstract
Rapidly developing mid-infrared quantum cascade laser (QCL) technology gives easy access to broadly tunable mid-IR laser radiation at a modest cost. Despite several applications of QCL in the industry, its usage for spectroscopic investigation of synthetically relevant organic compounds has been limited. Here, we report the application of an external cavity, continuous wave, mid-IR QCL to cryogenic ion vibrational predissociation spectroscopy to analyze a set of large organic molecules, organometallic complexes, and isotopically labeled compounds. The obtained spectra of test molecules are characterized by a high signal-to-noise ratio and low full width at half-maximum-values, allowing the assignment of two compounds with just a few wavenumber difference. Data generated by cw-QCL and spectra produced by another standard Nd:YAG difference-frequency generation system are compared and discussed.
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Affiliation(s)
| | | | | | - Peter Chen
- Laboratorium für Organische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland
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Paenurk E, Chen P. Modeling Gas-Phase Unimolecular Dissociation for Bond Dissociation Energies: Comparison of Statistical Rate Models within RRKM Theory. J Phys Chem A 2021; 125:1927-1940. [PMID: 33635061 DOI: 10.1021/acs.jpca.1c00183] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Rice-Ramsperger-Kassel-Marcus (RRKM) theory provides a simple yet powerful rate theory for calculating microcanonical rate constants. In particular, it has found widespread use in combination with gas-phase kinetic experiments of unimolecular dissociations to extract experimental bond dissociation energies (BDEs). We have previously found several discrepancies between the computed BDE values and the respective experimental ones, obtained with our empirical rate model, named L-CID. To investigate the reliability of our rate model, we conducted a theoretical analysis and comparison of the performance of conventional rate models and L-CID within the RRKM framework. Using the previously published microcanonical rate data as well as reaction cross-section data, we show that the BDE values obtained with the L-CID model agree with the ones from the other rate models within the expected uncertainty bounds. Based on this agreement, we discuss the possible rationalization of the good performance of the L-CID model.
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Affiliation(s)
- Eno Paenurk
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
| | - Peter Chen
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland
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10
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Tsybizova A, Paenurk E, Gorbachev V, Chen P. Perturbation of Pyridinium CIVP Spectra by N 2 and H 2 Tags: An Experimental and BOMD Study. J Phys Chem A 2020; 124:8519-8528. [PMID: 32954731 DOI: 10.1021/acs.jpca.0c06752] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In cryogenic ion vibrational predissociation (CIVP) spectroscopy, the influence of the tag on the spectrum is an important consideration. Whereas for small ions several studies have shown that the tag effects can be significant, these effects are less understood for large ions or for large numbers of tags. Nevertheless, it is commonly assumed that if the investigated molecular ion is large enough, the perturbations arising from the tag are small and can therefore be neglected in the interpretation. In addition, it is generally assumed that the more weakly bound the tag is, the less it perturbs the CIVP spectrum. Under these assumptions, CIVP spectra are claimed to be effectively IR absorption spectra of the free molecular ion. Having observed unexpected splittings in otherwise unproblematic CIVP spectra of some tagged ions, we report Born-Oppenheimer molecular dynamics (BOMD) simulations that strongly indicate that mobility among the more weakly bound tags leads to the surprising splittings. We compared the behavior of two tags commonly used in CIVP spectroscopy (H2 and N2) with a large pyridinium cation. Our experimental results surprisingly show that under the appropriate circumstances, the more weakly bound tag can perturb the CIVP spectra more than the more strongly bound tag by not just shifting but also splitting the observed bands. The more weakly bound tag had significant residence times at several spectroscopically distinct sites on the molecular ion. This indicates that the weakly bound tag is likely to sample several binding sites in the experiment, some of which involve interaction with the reporter chromophore.
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Affiliation(s)
- Alexandra Tsybizova
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Eno Paenurk
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Vladimir Gorbachev
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Peter Chen
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
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11
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Bot M, Gorbachev V, Tsybizova A, Chen P. Bond Dissociation Energies in the Gas Phase for Large Molecular Ions by Threshold Collision-Induced Dissociation Experiments: Stretching the Limits. J Phys Chem A 2020; 124:8692-8707. [PMID: 32955888 DOI: 10.1021/acs.jpca.0c05712] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Accurate bond dissociation energies for large molecules are difficult to obtain by either experimental or computational methods. The former methods are hampered by a range of physical and practical limitations in gas-phase measurement techniques, while the latter require incorporation of multiple approximations whose impact on accuracy may not always be clear. When internal benchmarks are not available, one hopes that experiment and theory can mutually support each other. A recent report found, however, a large discrepancy between gas-phase bond dissociation energies, measured mass spectrometrically, and the corresponding quantities computed using density functional theory (DFT)-D3 and DLPNO-CCSD(T) methods. With the widespread application of these computational methods to large molecular systems, the discrepancy needs to be resolved. We report a series of experimental studies that validate the mass spectrometric methods from small to large ions and find that bond dissociation energies extracted from threshold collision-induced dissociation experiments on large ions do indeed behave correctly. The implications for the computational studies are discussed.
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Affiliation(s)
- Marek Bot
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Vladimir Gorbachev
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Alexandra Tsybizova
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Peter Chen
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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