1
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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.
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Affiliation(s)
- Charles L Perrin
- Department of Chemistry & Biochemistry University of California, La Jolla, San Diego, CA 92093, USA
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2
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Zhao Y, Wang H, Kang X, Zhang R, Feng N, Su Q. Controllable methylenation with ethylene glycol as the methylene source: bridging enaminones and synthesis of tetrahydropyrimidines. Org Chem Front 2022. [DOI: 10.1039/d2qo01187e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Controllable methylenation using renewable ethylene glycol as the methylene source has been developed for the introduction of one or two methylene building blocks.
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Affiliation(s)
- Yulei Zhao
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
| | - Huimin Wang
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
| | - Xin Kang
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
| | - Ruihua Zhang
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
| | - Nan Feng
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
| | - Qi Su
- Shandong Key Laboratory of Life-Organic Analysis, Key Laboratory of Pharmaceutical Intermediates and Analysis of Natural Medicine, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
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3
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Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene. Symmetry (Basel) 2020. [DOI: 10.3390/sym12111924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.
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4
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Bazargan G, Curtin E, Sohlberg K. Comparing statistical predictions of quantum particle transit times in molecular systems to experimental measurements. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2020. [DOI: 10.1142/s0219633619500391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The movement of quantum particles between distinct spatial regions is an essential feature of nanoscale devices. Consequently, theoretical methods for characterizing the transit time associated with this movement may aid in identifying and refining nanoscale systems with desirable transport properties. Herein, we explore the utility and range of validity of a recently reported probabilistic method for quantifying the timescale of quantum particle transit. The method is applied to intramolecular proton transfer in dicarbonyl compounds, and electron transfer in donor-bridge-acceptor molecules. Direct comparison is made between statistical predictions of proton and electron transfer times and corresponding transfer times deduced from the previously reported experimental observables. Insights provided by the method into the path of flow of probability density are discussed.
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Affiliation(s)
- Gloria Bazargan
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
| | - Evan Curtin
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
| | - Karl Sohlberg
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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5
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Affiliation(s)
- Charles L. Perrin
- Department of Chemistry and Biochemistry, University of California—San Diego, La Jolla, California 92093-0358, United States
| | - Yifan Wu
- Department of Chemistry and Biochemistry, University of California—San Diego, La Jolla, California 92093-0358, United States
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6
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Siskos MG, Choudhary MI, Gerothanassis IP. Refinement of labile hydrogen positions based on DFT calculations of 1H NMR chemical shifts: comparison with X-ray and neutron diffraction methods. Org Biomol Chem 2018; 15:4655-4666. [PMID: 28513720 DOI: 10.1039/c7ob01019b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Numerous gas phase electron diffraction, ultra-fast electron diffraction, X-ray and neutron diffraction experiments on β-dicarbonyl compounds exhibiting enol-enol tautomeric equilibrium, with emphasis on acetylacetone and dibenzoylmethane, have so far been reported with conflicting results on the structural details of the O-HO intramolecular hydrogen bond and resulted in alternative hypotheses on the intramolecular hydrogen bond potential function either a double minimum potential corresponding to two tautomeric forms in equilibrium or a single symmetrical one. We demonstrate herein, firstly, that the DFT calculated OH 1H NMR chemical shifts of acetylacetone and dibenzoylmethane exhibit a strong linear dependence on the computed OO hydrogen bond length of ∼-50 ppm Å-1 and as a function of the O-HO bond angle of ∼1 ppm per degree, upon the transfer of the hydrogen atom from the ground state toward the transition state. Secondly, the refinement of labile hydrogen atomic positions in intramolecular hydrogen bonds based on the root-mean-square deviation between experimentally determined and DFT calculated 1H NMR chemical shifts in solution can provide high resolution structures of O-H and O(H)O bond lengths and O-HO bond angles with an accuracy of ∼10-2 Å and ∼0.5°, respectively. Thirdly, the calculated 1H NMR chemical shifts in solution of the two ground state tautomers in equilibrium of acetylacetone and dibenzoylmethane are in excellent agreement with the experimental value, even for moderate basis sets for energy minimization. In contrast, the single symmetrical structure in a strongly delocalized system is a transition state with calculated 1H NMR chemical shifts which strongly deviate from the experimental value. Fourth, the DFT calculated ground state O-H bond lengths of acetylacetone and dibenzoylmethane are in quantitative agreement with the literature data which take into account the effect of quantum nuclear motion. The DFT structural results are critically discussed with respect to the state-of-the-art variable temperature X-ray and neutron diffraction methods.
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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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7
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Lin C, Kumar M, Finney BA, Francisco JS. Intramolecular hydrogen bonding in malonaldehyde and its radical analogues. J Chem Phys 2017; 147:124309. [PMID: 28964036 DOI: 10.1063/1.4996563] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High level Brueckner doubles with triples correction method-based ab initio calculations have been used to investigate the nature of intramolecular hydrogen bonding and intramolecular hydrogen atom transfer in cis-malonaldehyde (MA) and its radical analogues. The radicals considered here are the ones that correspond to the homolytic cleavage of C-H bonds in cis-MA. The results suggest that cis-MA and its radical analogues, cis-MARS, and cis-MARA, both exist in planar geometry. The calculated intramolecular O-H⋯O=C bond in cis-MA is shorter than that in the radical analogues. The intramolecular hydrogen bond in cis-MA is stronger than in its radicals by at least 3.0 kcal/mol. The stability of a cis-malonaldehyde radical correlates with the extent of electron spin delocalization; cis-MARA, in which the radical spin is more delocalized, is the most stable MA radical, whereas cis-MARS, in which the radical spin is strongly localized, is the least stable radical. The natural bond orbital analysis indicates that the intramolecular hydrogen bonding (O⋯H⋯O) in cis-malonaldehyde radicals is stabilized by the interaction between the lone pair orbitals of donor oxygen and the σ* orbital of acceptor O-H bond (n → σ*OH). The calculated barriers indicate that the intramolecular proton transfer in cis-MA involves 2.2 kcal/mol lower barrier than that in cis-MARS.
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Affiliation(s)
- Chen Lin
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393, USA
| | - Manoj Kumar
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0321, USA
| | - Brian A Finney
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393, USA
| | - Joseph S Francisco
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393, USA
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8
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Zuo A, Birney DM. A Computational Study on the Addition of HONO to Alkynes toward the Synthesis of Isoxazoles; a Bifurcation, Pseudopericyclic Pathways and a Barrierless Reaction on the Potential Energy Surface. J Org Chem 2017; 82:8873-8881. [PMID: 28726408 DOI: 10.1021/acs.joc.7b01152] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Homopropargyl alcohols react with t-BuONO to form acyloximes which can be oxidatively cyclized to yield ioxazoles. The mechanism for the initial reaction of HONO with alkynes to form acyloximes (e.g., 13c) has been explored at the B3LYP/6-31G(d,p) + ZPVE level of theory. The observed chemoselectivity and regioselectivity are explained via an acid-catalyzed mechanism. Furthermore, the potential energy surface revealed numerous surprising features. The addition of HONO (8) to protonated 1-phenylpropyne (18) is calculated to follow a reaction pathway involving sequential transition states (TS6 and TS8), for which reaction dynamics likely play a role. This reaction pathway can bypass the expected addition product 21 as well as transition state TS8, directly forming the rearranged product 23. Nevertheless, TS8 is key to understanding the potential energy surface; there is a low barrier for the pseudopericylic [1,3]-NO shift, calculated to be only 8.4 kcal/mol above 21. This places TS8 well below TS6, making the valley-ridge inflection point (VRI or bifurcation) and direct formation of 23 possible. The final tautomerization step to the acyloxime can be considered to be a [1,5]-proton shift. However, the rearrangement in the case of 17h to 13c is calculated to be barrierless, arguably because the pathway is pseudopericyclic and exothermic.
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Affiliation(s)
- Ang Zuo
- Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States
| | - David M Birney
- Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409-1061, United States
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9
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Changing pictures of molecular faces and depths of potential acting on an electron in molecule for intramolecular proton transfer reactions of formic acid and malonaldehyde. COMPUT THEOR CHEM 2017. [DOI: 10.1016/j.comptc.2017.05.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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10
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Affiliation(s)
- Charles L. Perrin
- Department of Chemistry & Biochemistry University of California, San Diego, La Jolla, California 92093-0358, United States
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11
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Romero-Fernández MP, Ávalos M, Babiano R, Cintas P, Jiménez JL, Palacios JC. A further look at π-delocalization and hydrogen bonding in 2-arylmalondialdehydes. Tetrahedron 2016. [DOI: 10.1016/j.tet.2015.11.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Bedin M, Karim A, Reitti M, Carlsson ACC, Topić F, Cetina M, Pan F, Havel V, Al-Ameri F, Sindelar V, Rissanen K, Gräfenstein J, Erdélyi M. Counterion influence on the N-I-N halogen bond. Chem Sci 2015; 6:3746-3756. [PMID: 29218144 PMCID: PMC5707496 DOI: 10.1039/c5sc01053e] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 04/20/2015] [Indexed: 12/13/2022] Open
Abstract
A detailed investigation of the influence of counterions on the [N-I-N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N-I-N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(i) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(i) complexes are converted into multi-coordinate geometries with strong Ag-O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N-I-N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.
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Affiliation(s)
- Michele Bedin
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Alavi Karim
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Marcus Reitti
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Anna-Carin C Carlsson
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Filip Topić
- University of Jyvaskyla , Department of Chemistry , Nanoscience Center , P.O. Box. 35, FI-40014 University of Jyvaskyla , Finland
| | - Mario Cetina
- University of Jyvaskyla , Department of Chemistry , Nanoscience Center , P.O. Box. 35, FI-40014 University of Jyvaskyla , Finland
- Department of Applied Chemistry , Faculty of Textile Technology , University of Zagreb , Prilaz baruna Filipovića 28a , HR-10000 Zagreb , Croatia
| | - Fangfang Pan
- University of Jyvaskyla , Department of Chemistry , Nanoscience Center , P.O. Box. 35, FI-40014 University of Jyvaskyla , Finland
| | - Vaclav Havel
- Department of Chemistry and RECETOX , Masaryk University , Kamenice 5 , 625 00 Brno , Czech Republic
| | - Fatima Al-Ameri
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Vladimir Sindelar
- Department of Chemistry and RECETOX , Masaryk University , Kamenice 5 , 625 00 Brno , Czech Republic
| | - Kari Rissanen
- University of Jyvaskyla , Department of Chemistry , Nanoscience Center , P.O. Box. 35, FI-40014 University of Jyvaskyla , Finland
| | - Jürgen Gräfenstein
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
| | - Máté Erdélyi
- Department of Chemistry and Molecular Biology , University of Gothenburg , SE-412 96 Gothenburg , Sweden . ; Tel: +46-31-786 9033
- The Swedish NMR Centre , Medicinaregatan 5 , SE-413 90 Gothenburg , Sweden
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13
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Jalali E, Nori-Shargh D. Symmetry breaking in the axial symmetrical configurations of enolic propanedial, propanedithial, and propanediselenal: pseudo Jahn–Teller effect versus the resonance-assisted hydrogen bond theory. CAN J CHEM 2015. [DOI: 10.1139/cjc-2015-0071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The origin of the symmetry breaking in the axial symmetrical configurations of enolic propanedial (1), propanedithial (2), and propanediselenal (3) have been investigated by means of time-dependence density functional theory and natural bond orbital interpretations. The results obtained at the quantum chemistry composite (G2MP2, CBS-QB3), ab initio molecular orbital (MP2/6-311++G**), and hybrid density functional theory (B3LYP/6-311++G**) levels of theory showed that the hydrogen-centered synchronous axial symmetrical (C2v) configurations of compounds 1–3 possessing the maximum π-electron delocalization within the M1=C2–C3=C4–M5–H6 keto-enol groups are less stable than their corresponding plane symmetrical (Cs) forms. Importantly, the symmetry breaking in the C2v configurations of the enol forms of compounds 1–3 to their corresponding plane symmetrical Cs configurations is due to the pseudo Jahn–Teller effect (PJTE) by mixing the ground A1 and excited B2 electronic states resulting in a PJT (A1 + B2) ⊗ b2 problem. We may expect that by the decrease of the energy gaps between reference states in the C2v forms that are involved in the PJTE decrease from compound 1 to compound 3, the PJT stabilization energy (PJTSE) may increase but the results obtained showed that the corresponding PJTSEs decrease. This fact can be justified by the increase of the electron delocalizations from the nonbonding orbitals of the C=M moieties to the antibonding orbitals of the H–M bonds, which leads to an increase of the π-electron delocalization within the M1=C2–C3=C4–M5–H6 keto-enol groups. In confrontation between the impacts of the resonance-assisted hydrogen bond and PJTE in the structural and configurational properties of compounds 1–3, PJTE has an overwhelming contribution and causes the symmetry breaking of the C2v configurations to their corresponding Cs forms. The correlations between the structural parameters, synchronicity indices, natural charges, PJTSEs, electron delocalizations, and the hardness of compounds 1–3 have been investigated.
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Affiliation(s)
- Elahe Jalali
- Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
- Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
| | - Davood Nori-Shargh
- Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
- Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
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14
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Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds. Molecules 2015; 20:2405-24. [PMID: 25647577 PMCID: PMC6272349 DOI: 10.3390/molecules20022405] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 12/17/2014] [Accepted: 01/05/2015] [Indexed: 11/16/2022] Open
Abstract
The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static” and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N−. The paper will be deal with both secondary and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles.
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16
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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.
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Affiliation(s)
- Charles L Perrin
- Department of Chemistry, University of California-San Diego , La Jolla, California 92093-0358, United States
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17
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Nadal-Ferret M, Gelabert R, Moreno M, Lluch JM. Are there really low-barrier hydrogen bonds in proteins? The case of photoactive yellow protein. J Am Chem Soc 2014; 136:3542-52. [PMID: 24548066 DOI: 10.1021/ja4116617] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
For a long time, low-barrier hydrogen bonds (LBHBs) have been proposed to exist in many enzymes and to play an important role in their catalytic function, but the proof of their existence has been elusive. The transient formation of an LBHB in a protein system has been detected for the first time using neutron diffraction techniques on a photoactive yellow protein (PYP) crystal in a study published in 2009 (Yamaguchi, S.; et al. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 440-444). However, very recent theoretical studies based on electronic structure calculations and NMR resonance experiments on PYP in solution (Saito, K.; et al. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 167-172) strongly indicate that there is not such an LBHB. By means of electronic structure calculations combined with the solution of the nuclear Schrödinger equation, we analyze here under which conditions an LBHB can exist in PYP, thus leading to a more reasonable and conciliating understanding of the above-mentioned studies.
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Affiliation(s)
- Marc Nadal-Ferret
- Departament de Química and ‡Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona , 08193 Bellaterra (Barcelona), Spain
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18
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Stable acyclic aliphatic solid enols: synthesis, characterization, X-ray structure analysis and calculations. Sci Rep 2013; 3:1058. [PMID: 23320139 PMCID: PMC3544012 DOI: 10.1038/srep01058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 12/17/2012] [Indexed: 11/25/2022] Open
Abstract
A synthetic approach to stable enols was introduced and series of acyclic aliphatic solid enols were obtained and characterized. Relationship between the structure and the stability of these enols was discussed. Gaussian 09 calculations had been carried out to rationalize the stability of the enols. These enol structures were confirmed by 1H NMR, 13C NMR, MS, IR, partly by single crystal X-ray structure analysis and the protons exchange experiments. This work showed that very stable acyclic aliphatic enols can be synthesized efficiently without any purification.
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19
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Terranova ZL, Corcelli SA. Monitoring Intramolecular Proton Transfer with Two-Dimensional Infrared Spectroscopy: A Computational Prediction. J Phys Chem Lett 2012; 3:1842-1846. [PMID: 26291870 DOI: 10.1021/jz300714t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Proton transfer processes are ubiquitous and play a vital role in a broad range of chemical and biochemical phenomena. The ability of two-dimensional infrared (2D IR) spectroscopy with a carbon-deuterium (C-D) reporter to monitor the kinetics of proton transfer in the model compound malonaldehyde was demonstrated computationally. One of the two carbonyl/enol carbon atoms in malonaldehyde was labeled with a C-D bond. The C-D stretch vibrational frequency provides ∼150 cm(-1) of sensitivity to the two tautomers of malonaldehyde. Mixed quantum mechanics/molecular mechanics simulations employing the self-consistent-charge density functional tight binding (SCC-DFTB) method were used to compute 2D IR line shapes for the C-D stretch of labeled malonaldehyde in aqueous solution. The 2D IR spectra reveal cross peaks from the chemical exchange of the proton. The kinetics for the growth of the cross-peaks (and the decay of the diagonal peaks) precisely match the proton transfer rate observed in the SCC-DFTB simulations.
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Affiliation(s)
- Z L Terranova
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - S A Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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20
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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
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21
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OH stretching frequencies in systems with intramolecular hydrogen bonds: Harmonic and anharmonic analyses. Chem Phys 2011. [DOI: 10.1016/j.chemphys.2011.09.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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22
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Prototropic processes in benzaurins. 19F and 1H NMR spectra of fluoro- and methylsubstituted 4-hydroxyphenyl-diphenylcarbinols, related fuchsones and benzaurins. OPEN CHEM 2011. [DOI: 10.2478/s11532-011-0003-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractTautomerism of benzaurins and hydration are studied. 1H and 19F chemical shifts have been determined for a number of substituted 4-hydroxyphenyl-diphenyl carbinols containing fluorine in a 3-, 3*- or 4*-position, and for similar compounds containing additional methyl groups in a position of 3, 3** or 4**. The same data have been obtained for the fuchsones prepared by dehydration of the above carbinols. On this basis chemical shifts of fluorine in different positions have been evaluated as a monitor of the transformation of 4-hydroxyphenyl group to the semiquinone moiety. The 19F NMR can be used to monitor the transformation of 4**-fluorobenzaurin and the related 3,3*-disubstituted and 3,3*,5,5*-tetramethylsubstituted compounds to the corresponding carbinols due to the addition of a water molecule and to study the tautomerism of the two latter benzaurins as well as that of 3,3*,4**trifluorobenzaurin. Furthermore, fluorine and methyl group chemical shifts are sensitive to syn-anti-isomerism in substituted fuchsones.The prototropic process of these compounds may be slow or fast on a 1H NMR time scale depending on the solvent and may be catalyzed by water or carbonic acids. On the basis of kinetic and thermodynamic data obtained by dynamic NMR studies, a mechanism for the process has been proposed.
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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."
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Affiliation(s)
- Charles L. Perrin
- Department of Chemistry & Biochemistry, University of California—San Diego, La Jolla, California 92093-0358, United States
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24
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Perrin CL. Secondary equilibrium isotope effects on acidity. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2010. [DOI: 10.1016/s0065-3160(08)44003-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Abstract
A classic question regarding hydrogen bonds (H-bonds) concerns their symmetry. Is the hydrogen centered or is it closer to one donor and jumping between them? These possibilities correspond to single- and double-well potentials, respectively. The NMR method of isotopic perturbation can answer this question. It is illustrated with 3-hydroxy-2-phenylpropenal and then applied to dicarboxylate monoanions. The 18O-induced 13C NMR splittings signify that their intramolecular H-bonds are asymmetric and that each species is a pair of tautomers, not a single symmetric structure, even though maleate and phthalate are symmetric in crystals. The asymmetry is seen across a wide range of solvents and a wide variety of monoanions, including 2,3-di-tert-butylsuccinate and zwitterionic phthalates. Asymmetry is also seen in monoprotonated 1,8-bis(dimethylamino)naphthalenediamines, N,N'-diaryl-6-aminofulvene-2-aldimines, and 6-hydroxy-2-formylfulvene. The asymmetry is attributed to the disorder of the local environment, establishing an equilibrium between solvatomers. The broader implications of these results regarding the role of solvation in breaking symmetry are discussed. It was prudent to confirm a secondary deuterium isotope effect (IE) on amine basicity by NMR titration of a mixture of PhCH2NH2 and PhCHDNH2. The IE is of stereoelectronic origin. It is proposed that symmetric H-bonds can be observed in crystals but not in solution because a disordered environment induces asymmetry, whereas a crystal can guarantee a symmetric environment. The implications for the controversial role of low-barrier H-bonds in enzyme-catalyzed reactions are discussed.
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Affiliation(s)
- Charles L. Perrin
- 1Department of Chemistry, University of California, San Diego, La Jolla, CA 92093-0358, USA
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27
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Sośnicki JG, Langaard M, Hansen PE. Long-range deuterium isotope effects on (13)C chemical shifts of intramolecularly hydrogen-bonded N-substituted 3-(cycloamine)thiopropionamides or amides: a case of electric field effects. J Org Chem 2007; 72:4108-16. [PMID: 17469874 DOI: 10.1021/jo070285z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of intramolecularly hydrogen-bonded N-substituted 3-(piperidine, morpholine, N-methylpiperazine)thiopropionamides and some corresponding amides have been studied with special emphasis on hydrogen bonding. The compounds have been selected in order to vary and to minimize the N...N distance. Geometries, charge distributions, and chemical shifts of these compounds are obtained from DFT-type BP3LYP calculations. 1H and 13C 1D and 2D NMR experiments were performed to obtain H,H coupling constants, 13C chemical shifts assignments, and deuterium isotope effects on13C chemical shifts. Variable-temperature NMR studies and 2D exchange NMR spectra have been used to describe the rather complicated conformational behavior mainly governed by the ring flipping of the piperidine (morpholine) rings and intramolecular hydrogen bonding. Unusual long-range deuterium isotope effects on 13C chemical shifts are observed over as far as eight bonds away from the site of deuteriation. The isotope effects are related to the N...N distances, thus being related to the hydrogen bonding and polarization of the N-H bond. Arguments are presented showing that the deuterium isotope effects on 13C chemical shifts originate in electric field effects.
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Affiliation(s)
- Jacek G Sośnicki
- Institute of Chemistry and Environmental Protection, Szczecin University of Technology, Aleja Piastów 42, 71065 Szczecin, Poland
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28
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Hansen PE, Kamounah FS, Hansen BKV, Spanget-Larsen J. Conformational and tautomeric eccentricities of 2-acetyl-1,8-dihydroxynaphthalenes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2007; 45:106-17. [PMID: 17154238 DOI: 10.1002/mrc.1925] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Tautomerism in aromatic systems with oxygen substitutents is rare. This is investigated in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (1) and in 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (2). The tautomeric nature of 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene is supported by long-range hydrogen-hydrogen coupling between the OH-1 and the OH-8 and by the isotope effects on 13C caused by deuteration at the CH3C==O methyl group. Compound 2 participates in a degenerate equilibrium between two equivalent nonsymmetrical rotamers (2A and 2B), each having two intramolecular O...HO hydrogen bonds: one involving an acetyl oxygen and the neighboring hydroxyl group, and the other between the oxygen centers at positions 1 and 8. In addition, each rotamer is involved in a tautomeric equilibrium, with a structure having an OH-substituted exocyclic double bond (2AT or 2BT).DFT calculations for a large set of compounds highlight the factors controlling the unusual rotational and tautomeric behaviors. A very important factor seems to be the repulsive interaction between the O-1 and O-8 centers, which is modulated by formation of an OH-1...O-8 or OH-8...O1 hydrogen bond. Steric interactions, mesomeric release of electrons from the oxygen at position 8, and a strong OH...O...C hydrogen bond are other factors.Solid-state 13C NMR spectra of 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene at different temperatures demonstrated no averaging in the solid, whereas partially deuterated 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene showed an isotope effect at C-1 of 1.5 ppm, indicating tautomerism in the solid state.
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Affiliation(s)
- Poul Erik Hansen
- Department of Science, Systems and Models, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark.
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29
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Hansen PE. Isotope effect on chemical shifts in hydrogen-bonded systems. J Labelled Comp Radiopharm 2007. [DOI: 10.1002/jlcr.1440] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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30
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Perrin CL, Lau JS. Hydrogen-Bond Symmetry in Zwitterionic Phthalate Anions: Symmetry Breaking by Solvation. J Am Chem Soc 2006; 128:11820-4. [PMID: 16953621 DOI: 10.1021/ja063797o] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cationic nitrogen of zwitterion 1 is located symmetrically with respect to its intramolecular OHO hydrogen bond. Incorporation of one (18)O allows investigation of the H-bond symmetry by the NMR method of isotopic perturbation. In both CD(3)OD and CD(2)Cl(2) equilibrium isotope shifts are detected at the carboxyl and ipso carbons. Therefore, 1 exists as a pair of interconverting tautomers, not as a single symmetric structure with its hydrogen centered between the two oxygens. The H-bond is instantaneously asymmetric, and there is an equilibrium between solvatomers (isomers or stereoisomers that differ in solvation). The broader implications of this result regarding the role of the local environment ("solvation") in breaking symmetry are discussed.
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Affiliation(s)
- Charles L Perrin
- Department of Chemistry, University of California-San Diego, La Jolla, California 92093-0506, USA.
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31
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Musin RN, Mariam YH. An integrated approach to the study of intramolecular hydrogen bonds in malonaldehyde enol derivatives and naphthazarin: trend in energetic versus geometrical consequences. J PHYS ORG CHEM 2006. [DOI: 10.1002/poc.1102] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Aschi M, D'Abramo M, Ramondo F, Daidone I, D'Alessandro M, Di Nola A, Amadei A. Theoretical modeling of chemical reactions in complex environments: the intramolecular proton transfer in aqueous malonaldehyde. J PHYS ORG CHEM 2006. [DOI: 10.1002/poc.1051] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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33
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Gilli P, Bertolasi V, Pretto L, Ferretti V, Gilli G. Covalent versus electrostatic nature of the strong hydrogen bond: discrimination among single, double, and asymmetric single-well hydrogen bonds by variable-temperature X-ray crystallographic methods in beta-diketone enol RAHB systems. J Am Chem Soc 2004; 126:3845-55. [PMID: 15038739 DOI: 10.1021/ja030213z] [Citation(s) in RCA: 198] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Beta-diketone enols are known to form intramolecular...O=C-C=C-OH... resonance-assisted hydrogen bonds (RAHBs) with O...O distances as short as 2.39-2.44 A. However, even the most accurate diffraction studies have not been able to assess with certainty whether these very strong hydrogen bonds (H-bonds) are to be described as proton-centered O...H...O bonds in a single-well (SW) potential or as the dynamic or static mixing of two O-H...O <= => O...H-O tautomers in a double-well (DW) one. This contribution reexamines the problem and shows that diffraction methods are fairly able to assess the SW or DW nature of the H-bond formed and, in the second case, its dynamic or static nature, provided a Bayesian approach is used which associates a number of experimental techniques (X-ray crystallography at variable temperature, difference Fourier maps, least-squares refinement of proton populations, Hirshfeld's rigid-bond test) with a reasonable prior, that is the full set of possible proton-transfer (PT) pathways for the O-H...O system derived from theoretical calculations. The method is first applied to three beta-diketone enols, whose crystal structures were determined in the interval of temperatures 100-295 K and then generalized to the interpretation of a much wider set of beta-diketone enol structures derived from the literature, making it possible to establish a general relationship between chemical structure (symmetric or dissymmetric substitution, steric compression or stretching, increased pi-bond delocalizability), H-bond strength, and the shape of the PT-barrier. Final results are interpreted in terms of simplified VB theory and state-correlation (or avoided-crossing) diagrams.
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Affiliation(s)
- Paola Gilli
- Centro di Strutturistica Diffrattometrica and Dipartimento di Chimica, Universitá di Ferrara, Via L. Borsari, 46, 44100 Ferrara, Italy
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WU CC, CHAUDHURI C, JIANG JC, LEE YT, CHANG HC. Hydration-induced conformational changes in protonated 2,4-pentanedione in the gas phase. Mol Phys 2003. [DOI: 10.1080/0026897021000054835] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Perrin CL, Ohta BK. Symmetry of O-H-O and N-H-N hydrogen bonds in 6-hydroxy-2-formylfulvene and 6-aminofulvene-2-aldimines. Bioorg Chem 2002; 30:3-15. [PMID: 11954999 DOI: 10.1006/bioo.2001.1222] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The symmetry of the hydrogen bonds in 6-hydroxy-2-formylfulvene and two N,N'-diaryl-6-aminofulvene-2-aldimines is probed by the NMR technique of isotopic perturbation. Observed deuterium-induced 13C NMR isotope shifts at several positions can be attributed to a combination of an intrinsic shift and the perturbation of a tautomeric equilibrium. The most dramatic are at the aldehydic or aldiminic carbon signals, where the observed isotope shift for the unlabeled carbon is +376 or +223 ppb. This large downfield shift is contrary to the small upfield shift expected for a four-bond intrinsic shift and can be attributed only to a perturbation shift. Therefore these intramolecular hydrogen bonds are asymmetric, the proton resides in a double-minimum potential surface, and each molecule exists as a pair of rapidly interconverting tautomers, regardless of solvent. The symmetry of the hydrogen bond is not governed only by the O-O or N-N distance. It is proposed that symmetric hydrogen bonds can be observed in crystalline phases but not as yet in solution because the disorder of the solvation environment induces an asymmetry of the hydrogen bond, whereas a crystal can guarantee a symmetric environment. These results provide no insight into the source of the stabilization attributed to low-barrier hydrogen bonds if they lack the special feature of symmetry.
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Affiliation(s)
- Charles L Perrin
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla 92093-0358, USA.
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37
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Perrin CL, Kim YJ, Kuperman J. Structures of 1,6-Dioxa-6aλ4-thiapentalene and of 1,6,6aλ4-Trithiapentalene: Cs or C2v Symmetry? J Phys Chem A 2001. [DOI: 10.1021/jp013660e] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Charles L. Perrin
- Department of Chemistry, University of CaliforniaSan Diego, La Jolla, California 92093-0358
| | - Yeong-Joon Kim
- Department of Chemistry, University of CaliforniaSan Diego, La Jolla, California 92093-0358
| | - Joshua Kuperman
- Department of Chemistry, University of CaliforniaSan Diego, La Jolla, California 92093-0358
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Mariam YH, Musin RN. A B3LYP study of intramolecular hydrogen bonding and proton transfer in naphthazarin: a model system for daunomycin/adriamycin. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0166-1280(01)00487-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Perrin CL, Kim YJ. Isotopic perturbation of resonance in a homologous series of metal complexes with allylic cation character. J PHYS ORG CHEM 2000. [DOI: 10.1002/1099-1395(200011)13:11<752::aid-poc320>3.0.co;2-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Is a metal chelate symmetric, with the motion of the metal described by a single-well potential, or is it asymmetric, in a double-well potential? For hydrogen, this is the familiar question of the symmetry of a hydrogen bond. The molecular symmetry of MLn complexes (M = Li, Na, K, Al, Pd, Rh, Si, Sn, Ge, Sb, etc.; L is the anion of 3-hydroxy-2-phenylpropenal) in solution is now probed with the method of isotopic perturbation of equilibrium. A statistical mixture of 3-hydroxy-2-phenylpropenal-d0, -1-d, and -1,3-d2 was synthesized and converted to various metal complexes. Some complexes show two aldehydic signals, which means that their ligands are monodentate. For LiL, NaL, and KL, the 13C NMR isotope shifts, delta CH(D) - delta CH(H), for the aldehydic CH groups are small and negative, consistent with L- being a resonance hybrid. They are small and positive for AlL3, PdL2, Rh(CO)2L, SiX3L, SiL3+X-, (CF3)3GeL, SbCl4L, (EtO)4TaL, and (EtO)4NbL. The positive isotope shifts are unusual, but since they are small and temperature independent, they are intrinsic and indicate that these metal chelates are symmetric, as expected. Large positive isotope shifts, up to 400 ppb, are observed for Ph3GeL, Me3GeL, Ph2GeL2, Bu3SnL, and Ph4SbL. However, it is likely that these are monodentate complexes undergoing rapid metal migration, as judged from the X-ray crystal structures of Ph3SnL and Ph4SbL. NMR experiments indicate an intermolecular mechanism for exchange, which may be a biomolecular double metal transfer. It is remarkable that the isotope shifts in these five complexes demonstrate that they are asymmetric structures, even though they appear from other NMR evidence to be symmetric chelates.
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Affiliation(s)
- C L Perrin
- Department of Chemistry, University of California-San Diego, La Jolla, California 92093-0358, USA
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42
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Garcia-Viloca M, González-Lafont À, Lluch JM. Asymmetry of the Hydrogen Bond of Hydrogen Phthalate Anion in Solution. A QM/MM Study. J Am Chem Soc 1999. [DOI: 10.1021/ja9918831] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mireia Garcia-Viloca
- Contribution from the Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
| | - Àngels González-Lafont
- Contribution from the Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
| | - José M. Lluch
- Contribution from the Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
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Rodríguez-Santiago L, Sodupe M, Oliva A, Bertran J. Hydrogen Atom or Proton Transfer in Neutral and Single Positive Ions of Salicylic Acid and Related Compounds. J Am Chem Soc 1999. [DOI: 10.1021/ja990919m] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- L. Rodríguez-Santiago
- Contribution from the Departament de Química, Facultat de Ciencies, Universitat Autònoma de Barcelona, Bellaterra 09193 Spain
| | - M. Sodupe
- Contribution from the Departament de Química, Facultat de Ciencies, Universitat Autònoma de Barcelona, Bellaterra 09193 Spain
| | - A. Oliva
- Contribution from the Departament de Química, Facultat de Ciencies, Universitat Autònoma de Barcelona, Bellaterra 09193 Spain
| | - J. Bertran
- Contribution from the Departament de Química, Facultat de Ciencies, Universitat Autònoma de Barcelona, Bellaterra 09193 Spain
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44
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Fillaux F, Leygue N, Tomkinson J, Cousson A, Paulus W. Structure and dynamics of the symmetric hydrogen bond in potassium hydrogen maleate: a neutron scattering study. Chem Phys 1999. [DOI: 10.1016/s0301-0104(99)00153-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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