Theoretical Study of Multidimensional Proton Tunnelling in Benzoic Acid Dimer

Wójcik, Marek J.; Szczeponek, Krzysztof; Boczar, Marek

doi:10.3390/i4070422

Cited by 15 publications

(16 citation statements)

References 36 publications

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“…As pointed out in previous work 10,25 and also supported by theoretical work, 23,26,37 the activation energy describing the high temperature regime, ⌬E act /k B , does not represent the barrier height, which is evaluated to lie in the range of 3300-4000 K. 23,26,35,37 Even at ambient temperature, the concerted two hydron transfer in BA dimers is dominated by tunneling, and the observed high temperature activation energies represent some average value over vibrational levels of modes, in which tunneling is increased. The activation energy describing the intermediate regime, ⌬E exc , can be associated with the lowest energy levels of vibrations promoting tunneling ͑interdimer stretch and rocking modes͒.…”

Section: ͑17͒mentioning

confidence: 84%

Isotope effects associated with tunneling and double proton transfer in the hydrogen bonds of benzoic acid

Xue

Horsewill²,

Johnson³

et al. 2004

The Journal of Chemical Physics

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The isotope effects associated with double proton transfer in the hydrogen bonds of benzoic acid (BA) dimers have been measured using field-cycling (1)H NMR relaxometry and quasielastic neutron scattering. By studying mixed isotope (hydrogen and deuterium) samples, the dynamics of three isotopologues, BA-HH, BA-HD, and BA-DD, have been investigated. Low temperature measurements provide accurate measurements of the incoherent tunneling rate, k(0). This parameter scales accurately with the mass number, m, according to the formula k(0)=(E/m)e(-Fm) providing conclusive evidence that the proton transfer process is a strongly correlated motion of two hydrons. Furthermore, we conclude that the tunneling pathway is the same for the three isotopologue species. Measurements at higher temperatures illuminate the through barrier processes that are mediated via intermediate or excited vibrational states. In parallel with the investigation of proton transfer dynamics, the theoretical and experimental aspects of studying spin-lattice relaxation in single crystals of mixed isotope samples are investigated in depth. Heteronuclear dipolar interactions between (1)H and (2)H isotopes contribute significantly to the overall proton spin-lattice relaxation and it is shown that these must be modeled correctly to obtain accurate values for the proton transfer rates. Since the sample used in the NMR measurements was a single crystal, full account of the orientation dependence of the spin-lattice relaxation with respect to the applied B field was incorporated into the data analysis.

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Section: ͑17͒mentioning

confidence: 84%

Isotope effects associated with tunneling and double proton transfer in the hydrogen bonds of benzoic acid

Xue

Horsewill²,

Johnson³

et al. 2004

The Journal of Chemical Physics

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“…However, without experimental data for this system it is difficult to choose appropriate values and it is instructive to carry out computations over a range of values. Fortunately, since the double hydrogen-bond in the A-T system shares its properties with that of a much simpler and better studied molecule, the benzoic acid dimer, [66][67][68] it was decided to use parameters from the latter (DV R = 44 cm À1 , ho p = 186 cm À1 ) 69 as a benchmark around which to explore.…”

Section: Resultsmentioning

confidence: 99%

Modelling proton tunnelling in the adenine–thymine base pair

Godbeer

Al-Khalili

Stevenson

2015

Phys. Chem. Chem. Phys.

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The energies of the canonical (standard, amino-keto) and tautomeric (non-standard, imino-enol) charge-neutral forms of the adenine-thymine base pair (A-T and A*-T*, respectively) are calculated using density functional theory. The reaction pathway is then computed using a transition state search to provide the asymmetric double-well potential minima along with the barrier height and shape, which are combined to create the potential energy surface using a polynomial fit. The influence of quantum tunnelling on proton transfer within a base pair H-bond (modelled as the DFT deduced double-well potential) is then investigated by solving the time-dependent master equation for the density matrix. The effect on a quantum system by its surrounding water molecules is explored via the inclusion of a dissipative Lindblad term in the master equation, in which the environment is modelled as a heat bath of harmonic oscillators. It is found that quantum tunnelling, due to transitions to higher energy eigenstates with significant amplitudes in the shallow (tautomeric) side of the potential, is unlikely to be a significant mechanism for the creation of adenine-thymine tautomers within DNA, with thermally assisted coupling of the environment only able to boost the tunnelling probability to a maximum of 2 × 10(-9). This is barely increased for different choices of the starting wave function or when the geometry of the potential energy surface is varied.

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“…The first papers about dimeric formation by carboxyl group were published by Pfeiffer et al in 1910 [ 42 , 43 , 44 ]. The carboxylic acid dimer units (2 × (COOH)) have still attracted attention for researchers involved in H-bonding studies [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. In References [ 56 , 57 , 58 ], authors show a strong effect of H-bonds on the conformational state of compounds.…”

Section: Introductionmentioning

confidence: 99%

Inter- vs. Intramolecular Hydrogen Bond Patterns and Proton Dynamics in Nitrophthalic Acid Associates

et al. 2020

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Noncovalent interactions are among the main tools of molecular engineering. Rational molecular design requires knowledge about a result of interplay between given structural moieties within a given phase state. We herein report a study of intra- and intermolecular interactions of 3-nitrophthalic and 4-nitrophthalic acids in the gas, liquid, and solid phases. A combination of the Infrared, Raman, Nuclear Magnetic Resonance, and Incoherent Inelastic Neutron Scattering spectroscopies and the Car–Parrinello Molecular Dynamics and Density Functional Theory calculations was used. This integrated approach made it possible to assess the balance of repulsive and attractive intramolecular interactions between adjacent carboxyl groups as well as to study the dependence of this balance on steric confinement and the effect of this balance on intermolecular interactions of the carboxyl groups.

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Theoretical Study of Multidimensional Proton Tunnelling in Benzoic Acid Dimer

Abstract: Depending of the sign of the coupling parameter out-of-plane modes can either suppress or promote the splittings.

Cited by 15 publications

References 36 publications

Isotope effects associated with tunneling and double proton transfer in the hydrogen bonds of benzoic acid

Isotope effects associated with tunneling and double proton transfer in the hydrogen bonds of benzoic acid

Modelling proton tunnelling in the adenine–thymine base pair

Inter- vs. Intramolecular Hydrogen Bond Patterns and Proton Dynamics in Nitrophthalic Acid Associates

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