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Herold D, Brauser M, Kind J, Thiele CM. Evolution of a Combined UV/Vis and NMR Setup with Fixed Pathlengths for Mass-limited Samples. Chemistry 2024; 30:e202304016. [PMID: 38360972 DOI: 10.1002/chem.202304016] [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: 12/01/2023] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 02/17/2024]
Abstract
The investigation of reaction mechanisms is a complex task that usually requires the use of several techniques. To obtain as much information as possible on the reaction and any intermediates - possibly invisible to one technique - the combination of techniques is a solution. In this work we present a new setup for combined UV/Vis and NMR spectroscopy and compare it to an established alternative. The presented approach allows a versatile usage of different commercially-available components like mirrors and fiber bundles as well as different fixed pathlengths according to double transmission or single transmission measurements. While a previous approach is based on a dip-probe setup for conventional NMR probes, the new one is based on a micro-Helmholtz coil array (LiquidVoxel™). This makes the use of rectangular cuvettes possible, which ensure well-defined pathlengths allowing for quantification of species. Additionally, very low quantities of compound can be analyzed due to the microfabrication and small cuvette size used. As proof-of-principle this new setup for combined UV/Vis and NMR spectroscopy is used to examine a well-studied photochromic system of the dithienylethene compound class. A thorough comparison of the pros and cons of the two setups for combined UV/Vis and NMR measurements is performed.
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Affiliation(s)
- Dominik Herold
- Technische Universität Darmstadt/Technical University of Darmstadt, Clemens-Schöpf-Institut für Organische Chemie und Biochemie/Clemens Schöpf Institute of Organic Chemistry and Biochemistry, Darmstadt, D-64289, Germany
| | - Matthias Brauser
- Technische Universität Darmstadt/Technical University of Darmstadt, Clemens-Schöpf-Institut für Organische Chemie und Biochemie/Clemens Schöpf Institute of Organic Chemistry and Biochemistry, Darmstadt, D-64289, Germany
| | - Jonas Kind
- Technische Universität Darmstadt/Technical University of Darmstadt, Clemens-Schöpf-Institut für Organische Chemie und Biochemie/Clemens Schöpf Institute of Organic Chemistry and Biochemistry, Darmstadt, D-64289, Germany
| | - Christina M Thiele
- Technische Universität Darmstadt/Technical University of Darmstadt, Clemens-Schöpf-Institut für Organische Chemie und Biochemie/Clemens Schöpf Institute of Organic Chemistry and Biochemistry, Darmstadt, D-64289, Germany
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2
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Chen Y, Yang W, Liu J, Wang Y, Luo Y. The characteristics and mechanism of hydrogen bonding assembly in linear polyurethane with multiple pendant 2‐ureido‐4[1
H
]‐pyrimidone units. J Appl Polym Sci 2022. [DOI: 10.1002/app.53520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Yimei Chen
- Lab for Smart & Bioinspired Materials, College of Bioengineering Chongqing University Chongqing China
- Key Lab of Biorheological Science and Technology Ministry of Education Chongqing China
| | - Wei Yang
- Lab for Smart & Bioinspired Materials, College of Bioengineering Chongqing University Chongqing China
- Key Lab of Biorheological Science and Technology Ministry of Education Chongqing China
| | - Juan Liu
- Lab for Smart & Bioinspired Materials, College of Bioengineering Chongqing University Chongqing China
- Key Lab of Biorheological Science and Technology Ministry of Education Chongqing China
| | - Yuanliang Wang
- Lab for Smart & Bioinspired Materials, College of Bioengineering Chongqing University Chongqing China
- Key Lab of Biorheological Science and Technology Ministry of Education Chongqing China
| | - Yanfeng Luo
- Lab for Smart & Bioinspired Materials, College of Bioengineering Chongqing University Chongqing China
- Key Lab of Biorheological Science and Technology Ministry of Education Chongqing China
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3
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Fatima S, Varras PC, Atia-Tul-Wahab, Choudhary MI, Siskos MG, Gerothanassis IP. On the molecular basis of H 2O/DMSO eutectic mixtures by using phenol compounds as molecular sensors: a combined NMR and DFT study. Phys Chem Chem Phys 2021; 23:15645-15658. [PMID: 34268541 DOI: 10.1039/d0cp05861k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
NMR and DFT studies of phenol compounds as molecular sensors were carried out to investigate H2O/DMSO eutectic mixtures at a molecular level. The experimental 1H NMR chemical shifts of the OH groups, δexp(OH), of phenol, paracoumaric acid, and vanillic acid show maximum deshielding and, thus, hydrogen bond interactions in the range of mole fractions 0.20 < χ(DMSO) < 0.33. In the mole fractions χ(DMSO) < 0.2, a progressive decrease in δexp(OH) was observed which demonstrates a decrease in hydrogen bond interactions at infinite dilution in H2O, despite the increase in the number of available hydrogen bond acceptor and donor sites. DFT calculated δcalc(OH) of minimum energy solvation clusters were shown to be in reasonable agreement with the pattern in experimental δexp(OH) data. The chemical shift deshielding and, thus, increased hydrogen bond interactions in the natural product + DMSO + nH2O (n = 2, 3) solvation clusters, relative to complexes in DMSO or H2O solutions, cannot be attributed to a single structural parameter of the cooperative interactions between H2O and DMSO molecules with the phenol OH groups of the natural products. The minimum energy conformers of phenol compounds + 2H2O + DMSO complexes are in excellent agreement with a recent low temperature neutron diffraction experiment of 3D2O + DMSO and demonstrate a general structural motif of solvation complexes. The combined use of 1H NMR and DFT studies with emphasis on δ(OH) of phenol compounds, as molecular sensors, can provide an effective method for the study of solute-solvent interactions at the atomic level.
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Affiliation(s)
- Sana Fatima
- H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
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4
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Koeppe B, Tolstoy PM, Guo J, Denisov GS, Limbach HH. Combined NMR and UV-Vis Spectroscopic Studies of Models for the Hydrogen Bond System in the Active Site of Photoactive Yellow Protein: H-Bond Cooperativity and Medium Effects. J Phys Chem B 2021; 125:5874-5884. [PMID: 34060830 DOI: 10.1021/acs.jpcb.0c09923] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intramolecular hydrogen bonds in aprotic media were studied by combined (simultaneous) NMR and UV-vis spectroscopy. The species under investigation were anionic and featured single or coupled H-bonds between, for example, carboxylic groups and phenolic oxygen atoms (COO···H···OC)-, among phenolic oxygen atoms (CO···H···OC)-, and hydrogen bond chains between a carboxylic group and two phenolic oxygen atoms (COO···H···(OC)···H···OC)-. The last anion may be regarded as a small molecule model for the hydrogen bond system in the active site of wild-type photoactive yellow protein (PYP) while the others mimic the corresponding H-bonds in site-selective mutants. Proton positions in isolated hydrogen bonds and hydrogen bond chains were assessed by calculations for vacuum conditions and spectroscopically for the two media, CD2Cl2 and the liquefied gas mixture CDClF2/CDF3 at low temperatures. NMR parameters allow for the estimation of time-averaged H-bond geometries, and optical spectra give additional information about geometry distributions. Comparison of the results from the various systems revealed the effects of the formation of hydrogen bond chains and changes of medium conditions on the geometry of individual H-bonds. In particular, the proton in a hydrogen bond to a carboxylic group shifts from the phenolic oxygen atom in the system COO-···H-OC to the carboxylic group in COO-H···(OC)-···H-OC as a result of hydrogen bond formation to the additional phenolic donor. Increase in medium polarity may, however, induce the conversion of a structure of a type COO-H···(OC)-···H-OC to the type COO-···H-(OC)···H-OC. Application of these results obtained from the model systems to PYP suggests that both cooperative effects within the hydrogen bond chain and a low-polarity protein environment are prerequisites for the stabilization of negative charge on the cofactor and hence for the spectral tuning of the photoreceptor.
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Affiliation(s)
- Benjamin Koeppe
- J. Heyrovský Institute of Physical Chemistry, Dolejškova 2155/3, 182 23 Prague 8, Czech Republic
| | - Peter M Tolstoy
- Institute of Chemistry, St. Petersburg State University, Universitetskij pr. 26, 198504 St. Petersburg, Russia
| | - Jing Guo
- Department of Radiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Gleb S Denisov
- Department of Physics, St. Petersburg State University, 198504 St. Petersburg, Russian Federation
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5
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The Structure of the "Vibration Hole" around an Isotopic Substitution-Implications for the Calculation of Nuclear Magnetic Resonance (NMR) Isotopic Shifts. Molecules 2020; 25:molecules25122915. [PMID: 32599937 PMCID: PMC7355873 DOI: 10.3390/molecules25122915] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/22/2020] [Accepted: 06/22/2020] [Indexed: 11/17/2022] Open
Abstract
Calculations of nuclear magnetic resonance (NMR) isotopic shifts often rest on the unverified assumption that the “vibration hole”, that is, the change of the vibration motif upon an isotopic substitution, is strongly localized around the substitution site. Using our recently developed difference-dedicated (DD) second-order vibrational perturbation theory (VPT2) method, we test this assumption for a variety of molecules. The vibration hole turns out to be well localized in many cases but not in the interesting case where the H/D substitution site is involved in an intra-molecular hydrogen bond. For a series of salicylaldehyde derivatives recently studied by Hansen and co-workers (Molecules2019, 24, 4533), the vibrational hole was found to stretch over the whole hydrogen-bond moiety, including the bonds to the neighbouring C atoms, and to be sensitive to substituent effects. We discuss consequences of this finding for the accurate calculation of NMR isotopic shifts and point out directions for the further improvement of our DD-VPT2 method.
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6
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Gräfenstein J. Efficient calculation of NMR isotopic shifts: Difference-dedicated vibrational perturbation theory. J Chem Phys 2019; 151:244120. [PMID: 31893883 DOI: 10.1063/1.5134538] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We present difference-dedicated second-order vibrational perturbation theory (VPT2) as an efficient method for the computation of nuclear magnetic resonance (NMR) isotopic shifts, which reflect the geometry dependence of the NMR property in combination with different vibration patterns of two isotopologues. Conventional calculations of isotopic shifts, e.g., by standard VPT2, require scanning the geometry dependence over the whole molecule, which becomes expensive rapidly as the molecule size increases. In DD-VPT2, this scan can be restricted to a small region around the substitution site. At the heart of DD-VPT2 is a set of localized vibration modes common to the two isotopologues and designed such that the difference between the vibration patterns is caught by a small subset of them (usually fewer than 10). We tested the DD-VPT2 method for a series of molecules with increasing size and found that this method provides results with the same quality as VPT2 and in good agreement with the experiment, with computational savings up to 95% and less numerical instabilities. The method is easy to automatize and straightforward to generalize to other molecular properties.
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Affiliation(s)
- Jürgen Gräfenstein
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96 Göteborg, Sweden
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7
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Nitschke P, Lokesh N, Gschwind RM. Combination of illumination and high resolution NMR spectroscopy: Key features and practical aspects, photochemical applications, and new concepts. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:86-134. [PMID: 31779887 DOI: 10.1016/j.pnmrs.2019.06.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 06/04/2019] [Accepted: 06/04/2019] [Indexed: 06/10/2023]
Abstract
In the last decade, photochemical and photocatalytic applications have developed into one of the dominant research fields in chemistry. However, mechanistic investigations to sustain this enormous progress are still relatively sparse and in high demand by the photochemistry community. UV/Vis spectroscopy and EPR spectroscopy have been the main spectroscopic tools to study the mechanisms of photoreactions due to their higher time resolution and sensitivity. On the other hand, application of NMR in photosystems has been mainly restricted to photo-CIDNP, since the initial photoexcitation was thought to be the single key to understand photoinduced reactions. In 2015 the Gschwind group showcased the possibility that different reaction pathways could occur from the same photoexcited state depending on the reaction conditions by using in situ LED illumination NMR. This was the starting point to push the active participation of NMR in photosystems to its full potential, including reaction profiling, structure determination of intermediates, downstream mechanistic studies, dark pathways, intermediate sequencing with CEST etc. Following this, multiple studies using in situ illumination NMR have been reported focusing on mechanistic investigations in photocatalysis, photoswitches, and polymerizations. The recent increased popularity of this technique can be attributed to the simplicity of the experimental setup and the availability of low cost, high power LEDs. Here, we review the development of experimental design, applications and new concepts of illuminated NMR. In the first part, we describe the development of different designs of NMR illumination apparatus, illuminating from the bottom/side/top/inside, and discuss their pros and cons for specific applications. Furthermore, we address LASERs and LEDs as different light sources as well as special cases such as UVNMR(-illumination), FlowNMR, NMR on a Chip etc. To complete the discussion on experimental apparatus, the advantages and disadvantages of in situ LED illumination NMR versus ex situ illumination NMR are described. The second part of this review discusses different facets of applications of inside illumination experiments. It highlights newly revealed mechanistic and structural information and ideas in the fields of photocatalyis, photoswitches and photopolymerization. Finally, we present new concepts and methods based on the combination of NMR and illumination such as sensitivity enhancement, chemical pump probes, experimental access to transition state combinations and NMR actinometry. Overall this review presents NMR spectroscopy as a complementary tool to UV/Vis spectroscopy in mechanistic and structural investigations of photochemical processes. The review is presented in a way that is intended to assist the photochemistry and photocatalysis community in adopting and understanding this astonishingly powerful in situ LED illumination NMR method for their investigations on a daily basis.
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Affiliation(s)
- Philipp Nitschke
- Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | | | - Ruth M Gschwind
- Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany.
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8
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Ji Y, DiRocco DA, Kind J, Thiele CM, Gschwind RM, Reibarkh M. LED‐Illuminated NMR Spectroscopy: A Practical Tool for Mechanistic Studies of Photochemical Reactions. CHEMPHOTOCHEM 2019. [DOI: 10.1002/cptc.201900109] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yining Ji
- Process Research & DevelopmentMerck & Co., Inc. Rahway New Jersey 07065 USA
| | - Daniel A. DiRocco
- Process Research & DevelopmentMerck & Co., Inc. Rahway New Jersey 07065 USA
| | - Jonas Kind
- Clemens-Schöpf-Institut für Organische Chemie und BiochemieTechnische Universität Darmstadt Alarich-Weiss-Str. 16 64287 Darmstadt Germany
| | - Christina M. Thiele
- Clemens-Schöpf-Institut für Organische Chemie und BiochemieTechnische Universität Darmstadt Alarich-Weiss-Str. 16 64287 Darmstadt Germany
| | - Ruth M. Gschwind
- Institute of Organic ChemistryUniversity of Regensburg Universitätsstrasse 31 93053 Regensburg Germany
| | - Mikhail Reibarkh
- Process Research & DevelopmentMerck & Co., Inc. Rahway New Jersey 07065 USA
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9
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Mari SH, Varras PC, Atia-tul-Wahab, Choudhary IM, Siskos MG, Gerothanassis IP. Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts. Molecules 2019; 24:E2290. [PMID: 31226776 PMCID: PMC6631582 DOI: 10.3390/molecules24122290] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/13/2019] [Accepted: 06/18/2019] [Indexed: 01/09/2023] Open
Abstract
Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)-OH and C(8)-OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of -5.3 to -19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)-OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O-H and C-H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of -OH, -CH3, and -OCH3 substituents.
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Affiliation(s)
- Saima H. Mari
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
| | - Panayiotis C. Varras
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Atia-tul-Wahab
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Iqbal M. Choudhary
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Michael G. Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Ioannis P. Gerothanassis
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
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10
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Wild U, Hübner O, Greb L, Enders M, Kaifer E, Himmel HJ. Twofold Oxidized and Twofold Protonated Redox-Active Guanidine: An Ultimate Intermediate in Proton-Coupled Electron-Transfer Reactions. European J Org Chem 2018. [DOI: 10.1002/ejoc.201801378] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Ute Wild
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Olaf Hübner
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Lutz Greb
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Markus Enders
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hans-Jörg Himmel
- Anorganisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Im Neuenheimer Feld 270 69120 Heidelberg Germany
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11
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Seegerer A, Nitschke P, Gschwind RM. Combined In Situ Illumination-NMR-UV/Vis Spectroscopy: A New Mechanistic Tool in Photochemistry. Angew Chem Int Ed Engl 2018; 57:7493-7497. [PMID: 29573313 PMCID: PMC6033024 DOI: 10.1002/anie.201801250] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Indexed: 12/22/2022]
Abstract
Synthetic applications in photochemistry are booming. Despite great progress in the development of new reactions, mechanistic investigations are still challenging. Therefore, we present a fully automated in situ combination of NMR spectroscopy, UV/Vis spectroscopy, and illumination to allow simultaneous and time-resolved detection of paramagnetic and diamagnetic species. This optical fiber-based setup enables the first acquisition of combined UV/Vis and NMR spectra in photocatalysis, as demonstrated on a conPET process. Furthermore, the broad applicability of combined UVNMR spectroscopy for light-induced processes is demonstrated on a structural and quantitative analysis of a photoswitch, including rate modulation and stabilization of transient species by temperature variation. Owing to the flexibility regarding the NMR hardware, temperature, and light sources, we expect wide-ranging applications of this setup in various research fields.
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Affiliation(s)
- Andreas Seegerer
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
| | - Philipp Nitschke
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
| | - Ruth M. Gschwind
- Institute of Organic ChemistryUniversity of RegensburgUniversitätsstrasse 3193053RegensburgGermany
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12
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Čechová L, Kind J, Dračínský M, Filo J, Janeba Z, Thiele CM, Cigáň M, Procházková E. Photoswitching Behavior of 5-Phenylazopyrimidines: In Situ Irradiation NMR and Optical Spectroscopy Combined with Theoretical Methods. J Org Chem 2018; 83:5986-5998. [DOI: 10.1021/acs.joc.8b00569] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Lucie Čechová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, Prague 16610, Czech Republic
| | - Jonas Kind
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 16, Darmstadt 64287, Germany
| | - Martin Dračínský
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, Prague 16610, Czech Republic
| | - Juraj Filo
- Institute of Chemistry, Comenius University, Ilkovičova 6, Bratislava 84215, Slovakia
| | - Zlatko Janeba
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, Prague 16610, Czech Republic
| | - Christina M. Thiele
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 16, Darmstadt 64287, Germany
| | - Marek Cigáň
- Institute of Chemistry, Comenius University, Ilkovičova 6, Bratislava 84215, Slovakia
| | - Eliška Procházková
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, Prague 16610, Czech Republic
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13
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Seegerer A, Nitschke P, Gschwind RM. Combined In Situ Illumination-NMR-UV/Vis Spectroscopy: A New Mechanistic Tool in Photochemistry. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801250] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Andreas Seegerer
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
| | - Philipp Nitschke
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
| | - Ruth M. Gschwind
- Institute of Organic Chemistry; University of Regensburg; Universitätsstrasse 31 93053 Regensburg Germany
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14
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Koeppe B, Pylaeva SA, Allolio C, Sebastiani D, Nibbering ETJ, Denisov GS, Limbach HH, Tolstoy PM. Polar solvent fluctuations drive proton transfer in hydrogen bonded complexes of carboxylic acid with pyridines: NMR, IR and ab initio MD study. Phys Chem Chem Phys 2018; 19:1010-1028. [PMID: 27942642 DOI: 10.1039/c6cp06677a] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We study a series of intermolecular hydrogen-bonded 1 : 1 complexes formed by chloroacetic acid with 19 substituted pyridines and one aliphatic amine dissolved in CD2Cl2 at low temperature by 1H and 13C NMR and FTIR spectroscopy. The hydrogen bond geometries in these complexes vary from molecular (O-HN) to zwitterionic (O-H-N+) ones, while NMR spectra show the formation of short strong hydrogen bonds in intermediate cases. Analysis of C[double bond, length as m-dash]O stretching and asymmetric CO2- stretching bands in FTIR spectra reveal the presence of proton tautomerism. On the basis of these data, we construct the overall proton transfer pathway. In addition to that, we also study by use of ab initio molecular dynamics the complex formed by chloroacetic acid with 2-methylpyridine, surrounded by 71 CD2Cl2 molecules, revealing a dual-maximum distribution of hydrogen bond geometries in solution. The analysis of the calculated trajectory shows that the proton jumps between molecular and zwitterionic forms are indeed driven by dipole-dipole solvent-solute interactions, but the primary cause of the jumps is the formation/breaking of weak CHO bonds from solvent molecules to oxygen atoms of the carboxylate group.
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Affiliation(s)
- B Koeppe
- Department of Chemistry, Humboldt-Universität zu Berlin, Germany
| | - S A Pylaeva
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg, Germany.
| | - C Allolio
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg, Germany.
| | - D Sebastiani
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg, Germany.
| | - E T J Nibbering
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin, Germany.
| | - G S Denisov
- Department of Physics, St.Petersburg State University, Russia
| | - H-H Limbach
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - P M Tolstoy
- Center for Magnetic Resonance, St. Petersburg State University, Russia.
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15
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Malm C, Kim H, Wagner M, Hunger J. Complexity in Acid-Base Titrations: Multimer Formation Between Phosphoric Acids and Imines. Chemistry 2017; 23:10853-10860. [PMID: 28597513 PMCID: PMC5582606 DOI: 10.1002/chem.201701576] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Indexed: 11/08/2022]
Abstract
Solutions of Brønsted acids with bases in aprotic solvents are not only common model systems to study the fundamentals of proton transfer pathways but are also highly relevant to Brønsted acid catalysis. Despite their importance the light nature of the proton makes characterization of acid-base aggregates challenging. Here, we track such acid-base interactions over a broad range of relative compositions between diphenyl phosphoric acid and the base quinaldine in dichloromethane, by using a combination of dielectric relaxation and NMR spectroscopy. In contrast to what one would expect for an acid-base titration, we find strong deviations from quantitative proton transfer from the acid to the base. Even for an excess of the base, multimers consisting of one base and at least two acid molecules are formed, in addition to the occurrence of proton transfer from the acid to the base and simultaneous formation of ion pairs. For equimolar mixtures such multimers constitute about one third of all intermolecular aggregates. Quantitative analysis of our results shows that the acid-base association constant is only around six times larger than that for the acid binding to an acid-base dimer, that is, to an already protonated base. Our findings have implications for the interpretation of previous studies of reactive intermediates in organocatalysis and provide a rationale for previously observed nonlinear effects in phosphoric acid catalysis.
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Affiliation(s)
- Christian Malm
- Department of Molecular SpectroscopyMax Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Heejae Kim
- Department of Molecular SpectroscopyMax Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Manfred Wagner
- Department of Molecular SpectroscopyMax Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Johannes Hunger
- Department of Molecular SpectroscopyMax Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
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16
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Kozlovskaya V, Liu F, Xue B, Ahmad F, Alford A, Saeed M, Kharlampieva E. Polyphenolic Polymersomes of Temperature-Sensitive Poly(N-vinylcaprolactam)-block-Poly(N-vinylpyrrolidone) for Anticancer Therapy. Biomacromolecules 2017; 18:2552-2563. [PMID: 28700211 DOI: 10.1021/acs.biomac.7b00687] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We report a versatile synthesis for polyphenolic polymersomes of controlled submicron (<500 nm) size for intracellular delivery of high and low molecular weight compounds. The nanoparticles are synthesized by stabilizing the vesicular morphology of thermally responsive poly(N-vinylcaprolactam)n-b-poly(N-vinylpyrrolidone)m (PVCLn-PVPONm) diblock copolymers with tannic acid (TA), a hydrolyzable polyphenol, via hydrogen bonding at a temperature above the copolymer's lower critical solution temperature (LCST). The PVCL179-PVPONm diblock copolymers are produced by controlled reversible addition-fragmentation chain transfer (RAFT) polymerization of PVPON using PVCL as a macro-chain transfer agent. The size of the TA-locked (PVCL179-PVPONm) polymersomes at room temperature and upon temperature variations are controlled by the PVPON chain length and TA:PVPON molar unit ratio. The particle diameter decreases from 1000 to 950, 770, and 250 nm with increasing PVPON chain length (m = 107, 166, 205, 234), and it further decreases to 710, 460, 290, and 190 nm, respectively, upon hydrogen bonding with TA at 50 °C. Lowering the solution temperature to 25 °C results in a slight size increase for vesicles with longer PVPON. We also show that TA-locked polymersomes can encapsulate and store the anticancer drug doxorubicin (DOX) and higher molecular weight fluorescein isothiocyanate (FITC)-dextran in a physiologically relevant pH and temperature range. Encapsulated DOX is released in the nuclei of human alveolar adenocarcinoma tumor cells after 6 h incubation via biodegradation of the TA shell with the cytotoxicity of DOX-loaded polymersomes being concentration-dependent. Our approach offers biocompatible and intracellular degradable nanovesicles of controllable size for delivery of a variety of encapsulated materials. Considering the particle monodispersity, high loading capacity, and a facile two-step aqueous assembly based on the reversible temperature-responsiveness of PVCL, these polymeric vesicles have significant potential as novel drug nanocarriers and provide a new perspective for fundamental studies on thermo-triggered polymer assemblies in solutions.
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Affiliation(s)
- Veronika Kozlovskaya
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
| | - Fei Liu
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
| | - Bing Xue
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
| | - Fahim Ahmad
- Department of Infectious Disease, Drug Discovery Division, Southern Research , Birmingham, Alabama 35205, United States
| | - Aaron Alford
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
| | - Mohammad Saeed
- Department of Infectious Disease, Drug Discovery Division, Southern Research , Birmingham, Alabama 35205, United States
| | - Eugenia Kharlampieva
- Department of Chemistry, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States.,Center for Nanoscale Materials and Biointegration, University of Alabama at Birmingham , Birmingham, Alabama 35294, United States
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17
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The More, The Better: Simultaneous In Situ Reaction Monitoring Provides Rapid Mechanistic and Kinetic Insight. Top Catal 2017. [DOI: 10.1007/s11244-017-0737-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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18
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Siskos MG, Choudhary MI, Gerothanassis IP. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods. Molecules 2017; 22:E415. [PMID: 28272366 PMCID: PMC6155303 DOI: 10.3390/molecules22030415] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/27/2017] [Accepted: 03/03/2017] [Indexed: 12/21/2022] Open
Abstract
The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.
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Affiliation(s)
- Michael G Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - M Iqbal Choudhary
- H.E.J. Research Institute of Chemistry, International Center for Biological and Chemical Sciences, University of Karachi, Karachi 75270, Pakistan.
| | - Ioannis P Gerothanassis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
- H.E.J. Research Institute of Chemistry, International Center for Biological and Chemical Sciences, University of Karachi, Karachi 75270, Pakistan.
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19
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Pylaeva SA, Elgabarty H, Sebastiani D, Tolstoy PM. Symmetry and dynamics of FHF− anion in vacuum, in CD2Cl2 and in CCl4. Ab initio MD study of fluctuating solvent–solute hydrogen and halogen bonds. Phys Chem Chem Phys 2017; 19:26107-26120. [DOI: 10.1039/c7cp04493c] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Asymmetric solvation of FHF− by halogen- and hydrogen-bonding solvents breaks the symmetry of the anion.
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Affiliation(s)
- S. A. Pylaeva
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg
- Germany
| | - H. Elgabarty
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg
- Germany
| | - D. Sebastiani
- Institute of Chemistry, Martin-Luther Universität Halle-Wittenberg
- Germany
| | - P. M. Tolstoy
- Center for Magnetic Resonance, St. Petersburg State University
- Russia
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20
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Stadler E, Eibel A, Neshchadin D, Gescheidt G. Toward Matching Optically and NMR Active Volumes for Optimizing the Observation of Photo-Induced Reactions by NMR. ACTA ACUST UNITED AC 2016. [DOI: 10.1515/zpch-2016-0854] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
In the recent years photo-induced reactions are becoming increasingly popular in many fields of chemistry comprising biological conversions, material/environmental science and synthesis. NMR monitoring of such reactions has been shown being advantageous and several strategies of providing an efficient irradiation of the NMR sample have been developed and reported. Here we show that adjusting the optical properties of the investigated solution to the active volume detected by the NMR experiment is valuable. This is shown with the help of three examples comprising photo-isomerization, photo-induced polymerization and CIDNP-detected bond cleavage. Adjusting the photo-active volume to the NMR-detectable portion of the sample provides a substantially more realistic kinetic information, background suppression and reduction of thermal and diffusional effects.
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Affiliation(s)
- Eduard Stadler
- Institute of Physical and Theoretical Chemistry, TU Graz, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria
| | - Anna Eibel
- Institute of Physical and Theoretical Chemistry, TU Graz, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria
| | - Dmytro Neshchadin
- Institute of Physical and Theoretical Chemistry, TU Graz, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria
| | - Georg Gescheidt
- Institute of Physical and Theoretical Chemistry, TU Graz, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria
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21
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Bengiat R, Gil M, Klein A, Bogoslavsky B, Cohen S, Dubnikova F, Yardeni G, Zilbermann I, Almog J. Selective recognition of fluoride salts by vasarenes: a key role of a self-assembled in situ dimeric entity via an exceptionally short [O-H-O](-) H-bond. Dalton Trans 2016; 45:8734-9. [PMID: 26804131 DOI: 10.1039/c5dt04171f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A self-assembled supramolecular dimeric entity via an exceptionally short (2.404 Å) and strong (22.9 kcal mol(-1)) [O-H-O](-) hydrogen bond is the key to the special reactivity of vasarenes with fluoride salts. Vasarene is a self-assembled, vase-shaped compound, obtained by the reaction between ninhydrin and phloroglucinol. Analogous compounds are prepared by replacing the phloroglucinol with other polyhydroxy aromatics. Vasarenes show special affinity towards compounds of the type M(+)F(-), where M being a large monovalent cation, producing ion-pair-vasarene adducts. The first step in the proposed mechanism is the dissociation of the M(+)F(-) salt releasing F(-) to the solution, which may provide an explanation as to why only MF salts, which include large monovalent cations, undergo this reaction. From a practical point of view, the ease of their preparation and their special affinity towards fluoride salts make vasarenes potential means for salt separation. The readily formed dimeric structure with the very short [O-H-O](-) negative charge-assisted H-bond (-CAHB) can also be further used as a model in theoretical studies of such systems and understanding their role in biological processes.
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Affiliation(s)
- R Bengiat
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
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22
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Neidlinger A, Förster C, Heinze K. How Hydrogen Bonds Affect Reactivity and Intervalence Charge Transfer in Ferrocenium-Phenolate Radicals. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201501471] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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23
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Siskos MG, Tzakos AG, Gerothanassis IP. Accurate ab initio calculations of O-HO and O-H(-)O proton chemical shifts: towards elucidation of the nature of the hydrogen bond and prediction of hydrogen bond distances. Org Biomol Chem 2015. [PMID: 26196256 DOI: 10.1039/c5ob00920k] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The inability to determine precisely the location of labile protons in X-ray molecular structures has been a key barrier to progress in many areas of molecular sciences. We report an approach for predicting hydrogen bond distances beyond the limits of X-ray crystallography based on accurate ab initio calculations of O-HO proton chemical shifts, using a combination of DFT and contactor-like polarizable continuum model (PCM). Very good linear correlation between experimental and computed (at the GIAO/B3LYP/6-311++G(2d,p) level of theory) chemical shifts were obtained with a large set of 43 compounds in CHCl3 exhibiting intramolecular O-HO and intermolecular and intramolecular ionic O-H(-)O hydrogen bonds. The calculated OH chemical shifts exhibit a strong linear dependence on the computed (O)HO hydrogen bond length, in the region of 1.24 to 1.85 Å, of -19.8 ppm Å(-1) and -20.49 ppm Å(-1) with optimization of the structures at the M06-2X/6-31+G(d) and B3LYP/6-31+G(d) level of theory, respectively. A Natural Bond Orbitals (NBO) analysis demonstrates a very good linear correlation between the calculated (1)H chemical shifts and (i) the second-order perturbation stabilization energies, corresponding to charge transfer between the oxygen lone pairs and σ antibonding orbital and (ii) Wiberg bond order of the O-HO and O-H(-)O hydrogen bond. Accurate ab initio calculations of O-HO and O-H(-)O (1)H chemical shifts can provide improved structural and electronic description of hydrogen bonding and a highly accurate measure of distances of short and strong hydrogen bonds.
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Affiliation(s)
- Michael G Siskos
- Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina, GR 45110, Greece.
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24
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Pylaeva S, Allolio C, Koeppe B, Denisov GS, Limbach HH, Sebastiani D, Tolstoy PM. Proton transfer in a short hydrogen bond caused by solvation shell fluctuations: an ab initio MD and NMR/UV study of an (OHO)(-) bonded system. Phys Chem Chem Phys 2015; 17:4634-44. [PMID: 25586486 DOI: 10.1039/c4cp04727c] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We present a joint experimental and quantum chemical study on the influence of solvent dynamics on the protonation equilibrium in a strongly hydrogen bonded phenol-acetate complex in CD2Cl2. Particular attention is given to the correlation of the proton position distribution with the internal conformation of the complex itself and with fluctuations of the aprotic solvent. Specifically, we have focused on a complex formed by 4-nitrophenol and tetraalkylammonium-acetate in CD2Cl2. Experimentally we have used combined low-temperature (1)H and (13)C NMR and UV-vis spectroscopy and showed that a very strong OHO hydrogen bond is formed with proton tautomerism (PhOH···(-)OAc and PhO(-)···HOAc forms, both strongly hydrogen bonded). Computationally, we have employed ab initio molecular dynamics (70 and 71 solvent molecules, with and without the presence of a counter-cation, respectively). We demonstrate that the relative motion of the counter-cation and the "free" carbonyl group of the acid plays the major role in the OHO bond geometry and causes proton "jumps", i.e. interconversion of PhOH···(-)OAc and PhO(-)···HOAc tautomers. Weak H-bonds between CH(CD) groups of the solvent and the oxygen atom of carbonyl stabilize the PhOH···(-)OAc type of structures. Breaking of CH···O bonds shifts the equilibrium towards PhO(-)···HOAc form.
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Affiliation(s)
- Svetlana Pylaeva
- Department of Physics, St. Petersburg State University, Ulianovskaya st. 3, 198504 St. Petersburg, Russia.
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25
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Liu F, Kozlovskaya V, Zavgorodnya O, Martinez-Lopez C, Catledge S, Kharlampieva E. Encapsulation of anticancer drug by hydrogen-bonded multilayers of tannic acid. SOFT MATTER 2014; 10:9237-47. [PMID: 25284271 DOI: 10.1039/c4sm01813c] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Tannic acid (TA)-based multilayer assemblies have attracted increasing interest for biomedical applications. Here we explore properties of TA-poly(N-vinylpyrrolidone) (TA-PVPON) hydrogen-bonded multilayers for drug encapsulation and long-term storage. We demonstrate that the small molecular weight anticancer drug, doxorubicin (DOX), can be successfully loaded into (TA-PVPON) capsules with high encapsulation efficiency. We have also found that the encapsulated DOX can be efficiently stored inside the capsules for the pH range from pH = 7.4 to pH = 5. We show that the chemical and functional stability of TA at neutral and basic pH values is achieved through complexation with PVPON. The UV-vis spectrophotometry and in situ ellipsometry analyses of the hydrogen bonding interactions between TA and PVPON at different pH values reveal pH-dependent behavior of TA-PVPON capsules for the pH range from pH = 7.4 to pH = 5. Increasing deposition pH value from pH = 5 to pH = 7.4 leads to a 2-fold decrease in capsule thickness. However, this trend is reversed when salt concentration of the deposition solutions is increased from 0.01 M to 0.1 M NaCl. We have also demonstrated that the permeability of (TA-PVPON) capsules prepared using low salt deposition conditions and pH = 7.4 can be increased 2-fold by exposure of the capsules to 0.1 M NaCl salt solutions at the same pH. Our work opens new perspectives for design of novel polymer carriers for controlled drug delivery in cancer therapy.
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Affiliation(s)
- Fei Liu
- Department of Chemistry, University of Alabama at Birmingham, 901 14th St South, CHEM294, Birmingham, AL 35294, USA.
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26
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Charisiadis P, Kontogianni VG, Tsiafoulis CG, Tzakos AG, Siskos M, Gerothanassis IP. 1H-NMR as a structural and analytical tool of intra- and intermolecular hydrogen bonds of phenol-containing natural products and model compounds. Molecules 2014; 19:13643-82. [PMID: 25185070 PMCID: PMC6271058 DOI: 10.3390/molecules190913643] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 11/23/2022] Open
Abstract
Experimental parameters that influence the resolution of 1H-NMR phenol OH signals are critically evaluated with emphasis on the effects of pH, temperature and nature of the solvents. Extremely sharp peaks (Δν1/2≤2 Hz) can be obtained under optimized experimental conditions which allow the application of 1H-13C HMBC-NMR experiments to reveal long range coupling constants of hydroxyl protons and, thus, to provide unequivocal assignment of the OH signals even in cases of complex polyphenol natural products. Intramolecular and intermolecular hydrogen bonds have a very significant effect on 1H OH chemical shifts which cover a region from 4.5 up to 19 ppm. Solvent effects on -OH proton chemical shifts, temperature coefficients (Δδ/ΔT), OH diffusion coefficients, and nJ(13C, O1H) coupling constants are evaluated as indicators of hydrogen bonding and solvation state of phenol -OH groups. Accurate 1H chemical shifts of the OH groups can be calculated using a combination of DFT and discrete solute-solvent hydrogen bond interaction at relatively inexpensive levels of theory, namely, DFT/B3LYP/6-311++G (2d,p). Excellent correlations between experimental 1H chemical shifts and those calculated at the ab initio level can provide a method of primary interest in order to obtain structural and conformational description of solute-solvent interactions at a molecular level. The use of the high resolution phenol hydroxyl group 1H-NMR spectral region provides a general method for the analysis of complex plant extracts without the need for the isolation of the individual components.
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Affiliation(s)
- Pantelis Charisiadis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Vassiliki G Kontogianni
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | | | - Andreas G Tzakos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Michael Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Ioannis P Gerothanassis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
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27
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Grabow K, Bentrup U. Homogeneous Catalytic Processes Monitored by Combined in Situ ATR-IR, UV–Vis, and Raman Spectroscopy. ACS Catal 2014. [DOI: 10.1021/cs500363n] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Kathleen Grabow
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock (LIKAT), Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Ursula Bentrup
- Leibniz-Institut für Katalyse e.V. an der Universität Rostock (LIKAT), Albert-Einstein-Str. 29a, 18059 Rostock, Germany
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28
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Camp JCJ, Mantle MD, York APE, McGregor J. A new combined nuclear magnetic resonance and Raman spectroscopic probe applied to in situ investigations of catalysts and catalytic processes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:063111. [PMID: 24985803 DOI: 10.1063/1.4882317] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Both Raman and nuclear magnetic resonance (NMR) spectroscopies are valuable analytical techniques capable of providing mechanistic information and thereby providing insights into chemical processes, including catalytic reactions. Since both techniques are chemically sensitive, they yield not only structural information but also quantitative analysis. In this work, for the first time, the combination of the two techniques in a single experimental apparatus is reported. This entailed the design of a new experimental probe capable of recording simultaneous measurements on the same sample and/or system of interest. The individual datasets acquired by each spectroscopic method are compared to their unmodified, stand-alone equivalents on a single sample as a means to benchmark this novel piece of equipment. The application towards monitoring reaction progress is demonstrated through the evolution of the homogeneous catalysed metathesis of 1‑hexene, with both experimental techniques able to detect reactant consumption and product evolution. This is extended by inclusion of magic angle spinning (MAS) NMR capabilities with a custom made MAS 7 mm rotor capable of spinning speeds up to 1600 Hz, quantified by analysis of the spinning sidebands of a sample of KBr. The value of this is demonstrated through an application involving heterogeneous catalysis, namely the metathesis of 2-pentene and ethene. This provides the added benefit of being able to monitor both the reaction progress (by NMR spectroscopy) and also the structure of the catalyst (by Raman spectroscopy) on the very same sample, facilitating the development of structure-performance relationships.
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Affiliation(s)
- Jules C J Camp
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - Michael D Mantle
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - Andrew P E York
- Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, United Kingdom
| | - James McGregor
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom
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29
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Sigalov MV, Kalish N, Carmeli B, Pines D, Pines E. Probing Small Protonated Water Clusters in Acetonitrile Solutions by 1H NMR. ACTA ACUST UNITED AC 2013. [DOI: 10.1524/zpch.2013.0399] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Abstract
In a previous publication by Kalish et al. (J. Phys. Chem. A 115 (2011) 4063) the existence of well defined small protonated water clusters in acetonitrile has been established by IR spectroscopy. Here we report on a 1H NMR study of triflic acid, CF3SO3H, in acetonitrile-water solutions. Using NMR we are able to corroborate the general solvation scheme we have proposed for the hydrated proton in acetonitrile as a function of the molar ratio between the strong mineral acid and water, n = [H2O]/[acid]. According to this scheme, backed now by both IR absorption spectroscopy and NMR measurements, the very strong triflic acid completely dissociates in acetonitrile/water solutions to yield the aqueous proton and the triflate anion when n > 1. Furthermore, increasing n results in the proton solvated in increasingly larger water clusters formed within the acetonitrile solution.
Clearly distinguishable by NMR are the smallest protonated water clusters, the protonated water monomer, H3
+O, and the protonated water dimer, H5
+O2, which dominate the solution for n = 1,2,3. For larger n the NMR study indicates the gradual increase of the average protonated water cluster size as a function of n while the proton inner solvation core more closely retaining the characteristics of a deformed protonated water dimer, (H2O-H+⋯OH2)
s
than that of the protonated water monomer (H3
+O)
s
.
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Affiliation(s)
- Mark V. Sigalov
- Ben-Gurion University of the Negev, Department of Chemistry, Beer-Sheva 84125, Israel
| | - Noah Kalish
- Ben-Gurion University of the Negev, Department of Chemistry, Beer-Sheva 84125, Israel
| | - Benny Carmeli
- Ben-Gurion University of the Negev, Department of Chemistry, Beer-Sheva 84125, Israel
| | - Dina Pines
- Ben-Gurion University of the Negev, Department of Chemistry, Beer-Sheva 84125, Israel
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30
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Abstract
Abstract
Fluorescence and absorption spectral parameters of acridine have been studied in solution at room temperature in the presence of different proton donors aiming to inspect whether or not acridine can be used as a spectroscopic probe suitable to measure the geometry of hydrogen bonds under different conditions. It has been shown that the most appropriate spectral parameter is the position of fluorescence maximum that changes heavily upon a contraction of the N···H distance. Presumably, also the intensity of the maximum strongly depends on the hydrogen bond geometry. These two parameters can be used to establish two independent, mutually complementary correlations connecting the spectral manifestations and the geometry of hydrogen bond.
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31
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Koeppe B, Guo J, Tolstoy PM, Denisov GS, Limbach HH. Solvent and H/D isotope effects on the proton transfer pathways in heteroconjugated hydrogen-bonded phenol-carboxylic acid anions observed by combined UV-vis and NMR spectroscopy. J Am Chem Soc 2013; 135:7553-66. [PMID: 23607931 DOI: 10.1021/ja400611x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Heteroconjugated hydrogen-bonded anions A···H···X(-) of phenols (AH) and carboxylic/inorganic acids (HX) dissolved in CD2Cl2 and CDF3/CDF2Cl have been studied by combined low-temperature UV-vis and (1)H/(13)C NMR spectroscopy (UVNMR). The systems constitute small molecular models of hydrogen-bonded cofactors in proteins such as the photoactive yellow protein (PYP). Thus, the phenols studied include the PYP cofactor 4-hydroxycinnamic acid methyl thioester, and the more acidic 4-nitrophenol and 2-chloro-4-nitrophenol which mimic electronically excited cofactor states. It is shown that the (13)C chemical shifts of the phenolic residues of A···H···X(-), referenced to the corresponding values of A···H···A(-), constitute excellent probes for the average proton positions. These shifts correlate with those of the H-bonded protons, as well as with the H/D isotope effects on the (13)C chemical shifts. A combined analysis of UV-vis and NMR data was employed to elucidate the proton transfer pathways in a qualitative way. Dual absorption bands of the phenolic moiety indicate a double-well situation for the shortest OHO hydrogen bonds studied. Surprisingly, when the solvent polarity is low the carboxylates are protonated whereas the proton shifts toward the phenolic oxygens when the polarity is increased. This finding indicates that because of stronger ion-dipole interactions small anions are stabilized at high solvent polarity and large anions exhibiting delocalized charges at low solvent polarities. It also explains the large acidity difference of phenols and carboxylic acids in water, and the observation that this difference is strongly reduced in the interior of proteins when both partners form mutual hydrogen bonds.
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Affiliation(s)
- Benjamin Koeppe
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
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Guo J, Tolstoy PM, Koeppe B, Golubev NS, Denisov GS, Smirnov SN, Limbach HH. Hydrogen Bond Geometries and Proton Tautomerism of Homoconjugated Anions of Carboxylic Acids Studied via H/D Isotope Effects on 13C NMR Chemical Shifts. J Phys Chem A 2012; 116:11180-8. [DOI: 10.1021/jp304943h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jing Guo
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
| | - Peter M. Tolstoy
- Department of Chemistry, St. Petersburg State University, Universitetsky Pr.
26, 198504, St. Petersburg, Russia
| | - Benjamin Koeppe
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, D-12489 Berlin, Germany
| | - Nikolai S. Golubev
- Department of Physics, St. Petersburg State University, Uljanovskaja 1, 198504,
St. Petersburg, Russia
| | - Gleb S. Denisov
- Department of Physics, St. Petersburg State University, Uljanovskaja 1, 198504,
St. Petersburg, Russia
| | - Sergei N. Smirnov
- Department of Chemistry, St. Petersburg State University, Universitetsky Pr.
26, 198504, St. Petersburg, Russia
| | - Hans-Heinrich Limbach
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
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Navarro AM, García B, Hoyuelos FJ, Peñacoba IA, Leal JM. Preferential Solvation in Alkan-1-ol/Alkylbenzoate Binary Mixtures by Solvatochromic Probes. J Phys Chem B 2011; 115:10259-69. [DOI: 10.1021/jp202019x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ana M. Navarro
- Departamento de Química, Universidad de Burgos, 09001 Burgos, Spain
| | - Begoña García
- Departamento de Química, Universidad de Burgos, 09001 Burgos, Spain
| | | | | | - José M. Leal
- Departamento de Química, Universidad de Burgos, 09001 Burgos, Spain
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Knöpke LR, Reimann S, Spannenberg A, Langer P, Brückner A, Bentrup U. Elucidating the Directing Effect of Lewis Acids on the Reaction Pathway in Formal [3+3] Cyclocondensation Reactions: A Comprehensive In Situ Spectroscopic Study. ChemCatChem 2011. [DOI: 10.1002/cctc.201100150] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Koeppe B, Tolstoy PM, Limbach HH. Reaction pathways of proton transfer in hydrogen-bonded phenol-carboxylate complexes explored by combined UV-vis and NMR spectroscopy. J Am Chem Soc 2011; 133:7897-908. [PMID: 21534587 DOI: 10.1021/ja201113a] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Combined low-temperature NMR/UV-vis spectroscopy (UVNMR), where optical and NMR spectra are measured in the NMR spectrometer under the same conditions, has been set up and applied to the study of H-bonded anions A··H··X(-) (AH = 1-(13)C-2-chloro-4-nitrophenol, X(-) = 15 carboxylic acid anions, 5 phenolates, Cl(-), Br(-), I(-), and BF(4)(-)). In this series, H is shifted from A to X, modeling the proton-transfer pathway. The (1)H and (13)C chemical shifts and the H/D isotope effects on the latter provide information about averaged H-bond geometries. At the same time, red shifts of the π-π* UV-vis absorption bands are observed which correlate with the averaged H-bond geometries. However, on the UV-vis time scale, different tautomeric states and solvent configurations are in slow exchange. The combined data sets indicate that the proton transfer starts with a H-bond compression and a displacement of the proton toward the H-bond center, involving single-well configurations A-H···X(-). In the strong H-bond regime, coexisting tautomers A··H···X(-) and A(-)···H··X are observed by UV. Their geometries and statistical weights change continuously when the basicity of X(-) is increased. Finally, again a series of single-well structures of the type A(-)···H-X is observed. Interestingly, the UV-vis absorption bands are broadened inhomogeneously because of a distribution of H-bond geometries arising from different solvent configurations.
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Affiliation(s)
- Benjamin Koeppe
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
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Tolstoy PM, Guo J, Koeppe B, Golubev NS, Denisov GS, Smirnov SN, Limbach HH. Geometries and Tautomerism of OHN Hydrogen Bonds in Aprotic Solution Probed by H/D Isotope Effects on 13C NMR Chemical Shifts. J Phys Chem A 2010; 114:10775-82. [DOI: 10.1021/jp1027146] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peter M. Tolstoy
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Jing Guo
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Benjamin Koeppe
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Nikolai S. Golubev
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Gleb S. Denisov
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Sergei N. Smirnov
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
| | - Hans-Heinrich Limbach
- Institute of Chemistry and Biochemistry, Free University of Berlin, Germany, and V. A. Fock Institute of Physics, St. Petersburg State University, Russia
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Yoo J, Na SJ, Park HC, Cyriac A, Lee BY. Anion variation on a cobalt(iii) complex of salen-type ligand tethered by four quaternary ammonium salts for CO2/epoxide copolymerization. Dalton Trans 2010; 39:2622-30. [DOI: 10.1039/b920992a] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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