1
|
Perrin CL. Symmetry of Hydrogen Bonds: Application of NMR Method of Isotopic Perturbation and Relevance of Solvatomers. Molecules 2023; 28:molecules28114462. [PMID: 37298938 DOI: 10.3390/molecules28114462] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 05/25/2023] [Accepted: 05/27/2023] [Indexed: 06/12/2023] Open
Abstract
Short, strong, symmetric, low-barrier hydrogen bonds (H-bonds) are thought to be of special significance. We have been searching for symmetric H-bonds by using the NMR technique of isotopic perturbation. Various dicarboxylate monoanions, aldehyde enols, diamines, enamines, acid-base complexes, and two sterically encumbered enols have been investigated. Among all of these, we have found only one example of a symmetric H-bond, in nitromalonamide enol, and all of the others are equilibrating mixtures of tautomers. The nearly universal lack of symmetry is attributed to the presence of these H-bonded species as a mixture of solvatomers, meaning isomers (or stereoisomers or tautomers) that differ in their solvation environment. The disorder of solvation renders the two donor atoms instantaneously inequivalent, whereupon the hydrogen attaches to the less well solvated donor. We therefore conclude that there is no special significance to short, strong, symmetric, low-barrier H-bonds. Moreover, they have no heightened stability or else they would have been more prevalent.
Collapse
Affiliation(s)
- Charles L Perrin
- Department of Chemistry & Biochemistry University of California, La Jolla, San Diego, CA 92093, USA
| |
Collapse
|
2
|
Perrin CL, Shrinidhi A, Burke KD. Isotopic-Perturbation NMR Study of Hydrogen-Bond Symmetry in Solution: Temperature Dependence and Comparison of OHO and ODO Hydrogen Bonds. J Am Chem Soc 2019; 141:17278-17286. [PMID: 31590490 DOI: 10.1021/jacs.9b08492] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Is a hydrogen bond symmetric, with the hydrogen centered between two donor atoms, or is it asymmetric, with the hydrogen closer to one but jumping to the other? The NMR method of isotopic perturbation has been used to distinguish these. Previous evidence from isotope shifts implies that a wide variety of dicarboxylate monanions are asymmetric, present as a rapidly equilibrating mixture of tautomers. However, calculations of hydrogen trajectories across an anharmonic potential-energy surface could reproduce the observed isotope shifts in a phthalate monoanion. Therefore, it was concluded that those isotope shifts are instead consistent with isotope-induced desymmetrization on a symmetric potential-energy surface. To distinguish between these two interpretations, the 18O-induced isotope effects on the 13C NMR chemical shifts of cyclohexene-1,2-dicarboxylate monoanion in chloroform-d and on the 19F NMR chemical shifts of difluoromaleate monoanion in D2O have been investigated. In both cases the isotope effects are larger at lower temperature and also with deuterium in the hydrogen bond. It is concluded that these behaviors are consistent with the perturbation of an equilibrium between asymmetric tautomers and inconsistent with isotope-induced desymmetrization on a symmetric potential-energy surface.
Collapse
Affiliation(s)
- Charles L Perrin
- Department of Chemistry and Biochemistry , University of California-San Diego , La Jolla , California 92093-0358 , United States
| | - Annadka Shrinidhi
- Department of Chemistry and Biochemistry , University of California-San Diego , La Jolla , California 92093-0358 , United States
| | - Kathryn D Burke
- Department of Chemistry and Biochemistry , University of California-San Diego , La Jolla , California 92093-0358 , United States
| |
Collapse
|
3
|
Shenderovich IG. Simplified calculation approaches designed to reproduce the geometry of hydrogen bonds in molecular complexes in aprotic solvents. J Chem Phys 2018; 148:124313. [PMID: 29604820 DOI: 10.1063/1.5011163] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The impact of the environment onto the geometry of hydrogen bonds can be critically important for the properties of the questioned molecular system. The paper reports on the design of calculation approaches capable to simulate the effect of aprotic polar solvents on the geometric and NMR parameters of intermolecular hydrogen bonds. A hydrogen fluoride and pyridine complex has been used as the main model system because the experimental estimates of these parameters are available for it. Specifically, F-H, F⋯N, and H-N distances, the values of 15N NMR shift, and spin-spin coupling constants 1J(19F1H), 1hJ(1H15N), and 2hJ(19F15N) have been analyzed. Calculation approaches based on the gas-phase and the Polarizable Continuum Model (PCM) approximations and their combinations with geometric constraints and additional noncovalent interactions have been probed. The main result of this work is that the effect of an aprotic polar solvent on the geometry of a proton-donor⋯H⋯proton-acceptor complex cannot be reproduced under the PCM approximation if no correction for solvent-solute interactions is made. These interactions can be implicitly accounted for using a simple computational protocol.
Collapse
Affiliation(s)
- Ilya G Shenderovich
- Institute of Organic Chemistry, University of Regensburg, Universitaetstrasse 31, 93053 Regensburg, Germany
| |
Collapse
|
4
|
Gurinov AA, Denisov GS, Borissova AO, Goloveshkin AS, Greindl J, Limbach HH, Shenderovich IG. NMR Study of Solvation Effect on the Geometry of Proton-Bound Homodimers of Increasing Size. J Phys Chem A 2017; 121:8697-8705. [PMID: 29064692 DOI: 10.1021/acs.jpca.7b09285] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydrogen bond geometries in the proton-bound homodimers of quinoline and acridine derivatives in an aprotic polar solution have been experimentally studied using 1H NMR at 120 K. The reported results show that an increase of the dielectric permittivity of the medium results in contraction of the N···N distance. The degree of contraction depends on the homodimer's size and its substituent-specific solvation features. Neither of these effects can be reproduced using conventional implicit solvent models employed in computational studies. In general, the N···N distance in the homodimers of pyridine, quinoline, and acridine derivatives decreases in the sequence gas phase > solid state > polar solvent.
Collapse
Affiliation(s)
- Andrei A Gurinov
- Institute of Chemistry and Biochemistry, Free University Berlin , Takustrasse 3, 14195 Berlin, Germany.,The Imaging and Characterization Core Lab, King Abdullah University of Science and Technology , Al-Khawarizimi Building 01, Thuwal 23955-6900, Saudi Arabia
| | - Gleb S Denisov
- Institute of Physics, St. Petersburg State University , Ulyanovskaya str. 1, 198504 St. Petersburg, Russian Federation
| | - Alexandra O Borissova
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , 119991, Vavilov Str., 28, Moscow, Russia
| | - Alexander S Goloveshkin
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , 119991, Vavilov Str., 28, Moscow, Russia
| | - Julian Greindl
- Institute of Organic Chemistry, University of Regensburg , Universitaetstrasse 31, 93053 Regensburg, Germany
| | - Hans-Heinrich Limbach
- Institute of Chemistry and Biochemistry, Free University Berlin , Takustrasse 3, 14195 Berlin, Germany
| | - Ilya G Shenderovich
- Institute of Chemistry and Biochemistry, Free University Berlin , Takustrasse 3, 14195 Berlin, Germany.,Institute of Organic Chemistry, University of Regensburg , Universitaetstrasse 31, 93053 Regensburg, Germany
| |
Collapse
|
5
|
Varadwaj A, Varadwaj PR, Yamashita K. Hybrid organic-inorganic CH3NH3PbI3perovskite building blocks: Revealing ultra-strong hydrogen bonding and mulliken inner complexes and their implications in materials design. J Comput Chem 2017; 38:2802-2818. [DOI: 10.1002/jcc.25073] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/21/2017] [Accepted: 08/31/2017] [Indexed: 01/11/2023]
Affiliation(s)
- Arpita Varadwaj
- Department of Chemical System Engineering, School of Engineering; The University of Tokyo 7-3-1; Hongo Bunkyo-ku 113-8656 Japan
- CREST-JST, 7 Gobancho; Chiyoda-ku Tokyo 102-0076 Japan
| | - Pradeep R. Varadwaj
- Department of Chemical System Engineering, School of Engineering; The University of Tokyo 7-3-1; Hongo Bunkyo-ku 113-8656 Japan
- CREST-JST, 7 Gobancho; Chiyoda-ku Tokyo 102-0076 Japan
| | - Koichi Yamashita
- Department of Chemical System Engineering, School of Engineering; The University of Tokyo 7-3-1; Hongo Bunkyo-ku 113-8656 Japan
- CREST-JST, 7 Gobancho; Chiyoda-ku Tokyo 102-0076 Japan
| |
Collapse
|
6
|
Gurinov AA, Lesnichin SB, Limbach HH, Shenderovich IG. How short is the strongest hydrogen bond in the proton-bound homodimers of pyridine derivatives? J Phys Chem A 2014; 118:10804-12. [PMID: 25327551 DOI: 10.1021/jp5082033] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydrogen bond geometries in the proton-bound homodimers of ortho-unsubstituted and ortho-methylsubstituted pyridine derivatives in aprotic polar solution were estimated using experimental NMR data. Within the series of homodimers studied the hydrogen bond lengths depend on the proton affinity of pyridines and--at least for the ortho-methylsubstituted pyridines--on the pKa of the conjugate acids in an approximately quadratic manner. The shortest possible hydrogen bond in the homodimers of ortho-unsubstituted pyridines is characterized by the N···N distance of 2.613 Å. Steric repulsion between the methyl groups of the ortho-methylsubstituted pyridines becomes operative at an N···N distance of ∼2.7 Å and limits the closest approach to 2.665 Å.
Collapse
Affiliation(s)
- Andrey A Gurinov
- Institute of Chemistry and Biochemistry, Free University Berlin , Takustrasse 3, 14195 Berlin, Germany
| | | | | | | |
Collapse
|
7
|
|
8
|
Perrin CL, Burke KD. Variable-temperature study of hydrogen-bond symmetry in cyclohexene-1,2-dicarboxylate monoanion in chloroform-d. J Am Chem Soc 2014; 136:4355-62. [PMID: 24527684 DOI: 10.1021/ja500174y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The symmetry of the hydrogen bond in hydrogen cyclohexene-1,2-dicarboxylate monoanion was determined in chloroform using the NMR method of isotopic perturbation. As the temperature decreases, the (18)O-induced (13)C chemical-shift separations increase not only at carboxyl carbons but also at ipso (alkene) carbons. The magnitude of the ipso increase is consistent with an (18)O isotope effect on carboxylic acid acidity. Therefore it is concluded that this monoanion is a mixture of tautomers in rapid equilibrium, rather than a single symmetric structure in which a chemical-shift separation arises from coupling between a desymmetrizing vibration and anharmonic isotope-dependent vibrations, which is expected to show the opposite temperature dependence.
Collapse
Affiliation(s)
- Charles L Perrin
- Department of Chemistry, University of California-San Diego , La Jolla, California 92093-0358, United States
| | | |
Collapse
|
9
|
Ip BCK, Shenderovich IG, Tolstoy PM, Frydel J, Denisov GS, Buntkowsky G, Limbach HH. NMR Studies of Solid Pentachlorophenol-4-Methylpyridine Complexes Exhibiting Strong OHN Hydrogen Bonds: Geometric H/D Isotope Effects and Hydrogen Bond Coupling Cause Isotopic Polymorphism. J Phys Chem A 2012; 116:11370-87. [DOI: 10.1021/jp305863n] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Brenda C. K. Ip
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin,
Germany
| | - Ilya G. Shenderovich
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin,
Germany
- St. Petersburg State University, 198504 St. Petersburg, Russian Federation
| | - Peter M. Tolstoy
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin,
Germany
- St. Petersburg State University, 198504 St. Petersburg, Russian Federation
| | - Jaroslaw Frydel
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin,
Germany
| | - Gleb S. Denisov
- St. Petersburg State University, 198504 St. Petersburg, Russian Federation
| | - Gerd Buntkowsky
- Eduard-Zintl-Institut für
Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 20, D-64287 Darmstadt, Germany
| | - Hans-Heinrich Limbach
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin,
Germany
| |
Collapse
|
10
|
Perrin CL, Karri P, Moore C, Rheingold AL. Hydrogen-bond symmetry in difluoromaleate monoanion. J Am Chem Soc 2012; 134:7766-72. [PMID: 22519701 DOI: 10.1021/ja2117848] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The symmetry of the hydrogen bond in hydrogen difluoromaleate monoanion is probed by X-ray crystallography and by the NMR method of isotopic perturbation in water, in two aprotic organic solvents, and in an isotropic liquid crystal. The X-ray crystal structure of potassium hydrogen difluoromaleate shows a remarkably short O-O distance of 2.41 Å and equal O-H distances of 1.206 Å, consistent with a strong and symmetric hydrogen bond. Incorporation of (18)O into one carboxyl group allows investigation of the symmetry of the H-bond in solution by the method of isotopic perturbation. The (19)F NMR spectra of the mono-(18)O-substituted monoanion in water, CD(2)Cl(2), and CD(3)CN show an AB spin system, corresponding to fluorines in different environments. The difference is attributed to the perturbation of the acidity of a carboxylic acid by (18)O, not to the mere presence of the (18)O, because the mono-(18)O dianion shows equivalent fluorines. Therefore, it is concluded that the monoanion exists as an equilibrating pair of interconverting tautomers and not as a single symmetric structure not only in water but also in organic solvents. However, in the isotropic liquid crystal phase of 4-cyanophenyl 4-heptylbenzoate, tetrabutylammonium hydrogen difluoromaleate-(18)O shows equivalent fluorines, consistent with a single symmetric structure. These results support earlier studies, which suggested that the symmetry of hydrogen bonds can be determined by the local environment.
Collapse
Affiliation(s)
- Charles L Perrin
- Department of Chemistry, University of California-San Diego, La Jolla, California 92093-0358, USA.
| | | | | | | |
Collapse
|
11
|
Carlsson ACC, Gräfenstein J, Budnjo A, Laurila JL, Bergquist J, Karim A, Kleinmaier R, Brath U, Erdélyi M. Symmetric Halogen Bonding Is Preferred in Solution. J Am Chem Soc 2012; 134:5706-15. [DOI: 10.1021/ja301341h] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Anna-Carin C. Carlsson
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Jürgen Gräfenstein
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Adnan Budnjo
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Jesse L. Laurila
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Jonas Bergquist
- Analytical Chemistry, Department
of Chemistry - Biomedical Center, Uppsala University, SE-751 24, Uppsala, Sweden
| | - Alavi Karim
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Roland Kleinmaier
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Ulrika Brath
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
| | - Máté Erdélyi
- Department
of Chemistry and
Molecular Biology, University of Gothenburg, SE-412 96 Gothenburg, Sweden
- The Swedish NMR Centre, Medicinaregatan
5c, SE-413 90 Gothenburg, Sweden
| |
Collapse
|
12
|
Carlsson ACC, Gräfenstein J, Laurila JL, Bergquist J, Erdélyi M. Symmetry of [N–X–N]+halogen bonds in solution. Chem Commun (Camb) 2012; 48:1458-60. [DOI: 10.1039/c1cc15839b] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
|
13
|
Dopieralski P, Perrin CL, Latajka Z. On the Intramolecular Hydrogen Bond in Solution: Car-Parrinello and Path Integral Molecular Dynamics Perspective. J Chem Theory Comput 2011; 7:3505-13. [PMID: 26598249 DOI: 10.1021/ct200580c] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The issue of the symmetry of short, low-barrier hydrogen bonds in solution is addressed here with advanced ab initio simulations of a hydrogen maleate anion in different environments, starting with the isolated anion, going through two crystal structures (sodium and potassium salts), then to an aqueous solution, and finally in the presence of counterions. By Car-Parrinello and path integral molecular dynamics simulations, it is demonstrated that the position of the proton in the intramolecular hydrogen bond of an aqueous hydrogen maleate anion is entirely related to the solvation pattern around the oxygen atoms of the intramolecular hydrogen bond. In particular, this anion has an asymmetric hydrogen bond, with the proton always located on the oxygen atom that is less solvated, owing to the instantaneous solvation environment. Simulations of water solutions of hydrogen maleate ion with two different counterions, K(+) and Na(+), surprisingly show that the intramolecular hydrogen-bond potential in the case of the Na(+) salt is always asymmetric, regardless of the hydrogen bonds to water, whereas for the K(+) salt, the potential for H motion depends on the location of the K(+). It is proposed that repulsion by the larger and more hydrated K(+) is weaker than that by Na(+) and competitive with solvation by water.
Collapse
Affiliation(s)
| | - Charles L Perrin
- Department of Chemistry and Biochemistry, University of California at San Diego , La Jolla, California 92093-0358, United States
| | - Zdzislaw Latajka
- Faculty of Chemistry, University of Wroclaw , Joliot-Curie 14, 50-383 Wroclaw, Poland
| |
Collapse
|
14
|
Kong S, Borissova AO, Lesnichin SB, Hartl M, Daemen LL, Eckert J, Antipin MY, Shenderovich IG. Geometry and spectral properties of the protonated homodimer of pyridine in the liquid and solid states. A combined NMR, X-ray diffraction and inelastic neutron scattering study. J Phys Chem A 2011; 115:8041-8. [PMID: 21644583 DOI: 10.1021/jp203543g] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structure and spectral signatures of the protonated homodimer of pyridine in its complex with a poorly coordinating anion have been studied in solution in CDF(3)/CDClF(2) down to 120 K and in a single crystal. In both phases, the hydrogen bond is asymmetric. In the solution, the proton is involved in a fast reversible transfer that determines the multiplicity of NMR signals and the sign of the primary H/D isotope effect of --0.95 ppm. The proton resonates at 21.73 ppm that is above any value reported in the past and is indicative of a very short hydrogen bond. By combining X-ray diffraction analysis with model computations, the position of the proton in the crystal has been defined as d(N-H) = 1.123 Å and d(H···N) = 1.532 Å. The same distances have been estimated using a (15)N NMR correlation. The frequency of the protonic out-of-plane bending mode is 822 cm(-1) in agreement with Novak's correlation.
Collapse
Affiliation(s)
- S Kong
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
In a symmetric hydrogen bond (H-bond), the hydrogen atom is perfectly centered between the two donor atoms. The energy diagram for hydrogen motion is thus a single-well potential, rather than the double-well potential of a more typical H-bond, in which the hydrogen is covalently bonded to one atom and H-bonded to the other. Examples of symmetric H-bonds are often found in crystal structures, and they exhibit the distinctive feature of unusually short length: for example, the O-O distance in symmetric OHO H-bonds is found to be less than 2.5 Å. In comparison, the O-O distance in a typical asymmetric H-bond, such as ROH···OR(2), ranges from about 2.7 to 3.0 Å. In this Account, we briefly review and update our use of the method of isotopic perturbation to search for a symmetric, centered, or single-well-potential H-bond in solution. Such low-barrier H-bonds are thought to be unusually strong, owing perhaps to the resonance stabilization of two identical resonance forms [A-H···B ↔ A···H-B]. This presumptive bond strength has been invoked to explain some enzyme-catalyzed reactions. Yet in solution, a wide variety of OHO, OHN, and NHN H-bonds have all been found to be asymmetric, in double-well potentials. Examples include the monoanion of (±)-2,3-di-tert-butylsuccinic acid and a protonated tetramethylnaphthalenediamine, even though these two ions are often considered prototypes of species with strong H-bonds. In fact, all of the purported examples of strong, symmetric H-bonds have been found to exist in solution as pairs of asymmetric tautomers, in contrast to their symmetry in some crystals. The asymmetry can be attributed to the disorder of the local solvation environment, which leads to an equilibrium among solvatomers (that is, isomers that differ in solvation). If the disorder of the local environment is sufficient to break symmetry, then symmetry itself is not sufficient to stabilize the H-bond, and symmetric H-bonds do not have an enhanced stability or an unusual strength. Nor are short H-bonds unusually strong. We discuss previous evidence for "short, strong, low-barrier" H-bonds and show it to be based on ambiguous comparisons. The role of such H-bonds in enzyme-catalyzed reactions is then ascribed not to any unusual strength of the H-bond itself but to relief of "strain."
Collapse
Affiliation(s)
- Charles L. Perrin
- Department of Chemistry & Biochemistry, University of California—San Diego, La Jolla, California 92093-0358, United States
| |
Collapse
|
16
|
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
| |
Collapse
|
17
|
Lesnichin SB, Tolstoy PM, Limbach HH, Shenderovich IG. Counteranion-dependent mechanisms of intramolecular proton transfer in aprotic solution. Phys Chem Chem Phys 2010; 12:10373-9. [PMID: 20582365 DOI: 10.1039/c004499g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using the freon mixture CDF(3)/CDClF(2) as solvent we have been able to measure the (1)H and (15)N NMR spectra of the doubly (15)N labeled 2,2'-bipyridinium cation (BpyH(+)) at temperatures down to 115 K. The obtained NMR parameters strongly depend on the type of counteranions indicating the formation of ion pairs. In the case of the bulky poorly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]-borate as the counteranion a strong intramolecular NHN hydrogen bond was observed in BpyH(+) exhibiting a degenerate intramolecular proton transfer which is of the order of 10(6) s(-1) even at 120 K. By contrast, the weak hydrogen bond acceptor tetrafluoroborate favors a weak intermolecular FHN interaction and quenches the intramolecular proton transfer. The intramolecular proton transfer requires in this case a dissociation of the ion pair which is hindered by the Coulomb interaction. A slow intramolecular proton transfer was observed in the case of dichloroacetate which forms a strong intermolecular OHN hydrogen bond to BpyH(+). The mechanism of this transfer presumably involves a preliminary intermolecular proton transfer from nitrogen towards oxygen followed by a hydrogen bond switch to the neighboring nitrogen to which the proton is then transferred.
Collapse
Affiliation(s)
- Stepan B Lesnichin
- Institut für Chemie und Biochemie der Freien Universiät Berlin, Takustrasse 3, D-14195, Berlin, Germany
| | | | | | | |
Collapse
|