Erratum: “An advanced dielectric continuum approach for treating solvation effects: Time correlation functions. I. Local treatment” [J. Chem. Phys. 108, 1103 (1998)]

A local continuum solvation theory, exactly treating electrostatic matching conditions on the boundary of a cavity occupied by a solute particle, is extended to cover time-dependent solvation phenomena. The corresponding integral equation is solved with a complex-valued frequency-dependent dielectric function ε(ω), resulting in a complex-valued ω-dependent reaction field. The inverse Fourier transform then produces the real-valued solvation energy, presented in the form of a time correlation function (TCF). We applied this technique to describe the solvation TCF for a benzophenone anion in Debye (acetonitrile) and two-mode Debye (dimethylformamide) solvents. For the Debye solvent the TCF is described by two exponential components, for the two-mode Debye solvent, by three. The overall dynamics in each case is longer than that given by the simple continuum model. We also consider a steady-state kinetic regime and the corresponding rate constant for adiabatic electron-transferreactions. Here the boundary effect introduced within a frequency-dependent theory generates only a small effect in comparison with calculations made within the static continuum model

Model study of the primary H/D isotope effects on the NMR chemical shift in strong hydrogen-bonded systems

The model of the OHO (ODO) quasisymmetric fragment potential energy surface suggested earlier is used for calculation of the H/D substitution effect on the chemical shift (δH or δD) of the bridged nucleus as function of the O-O equilibrium distance RH e (2.40 ≤ RH e ≤ 2.60 Å) for systems with a strong H bond. The theoretical curves are compared with the experimental data. The non-monotonous ΔδH/D=δH-δD dependence on RH e and on δH as well as the negative and large positive (0.2 ppm) ΔδH/D values are interpreted. © 1992

Advanced continuum approaches for treating time correlation functions. The role of solute shape and solvent structure

Time correlation functions describing the solvent relaxation around a molecule of coumarin-153 and a benzophenone anion in acetonitrile are calculated using dynamical continuum theories of solvation with an experimental dielectric function ε(ω) including the resonance absorption region of the solvent. Apart from the local model with a single molecular-shaped solute cavity of the solute studied previously, a new dynamic local model with a double molecular-shaped cavity and a dynamic nonlocal theory with a spherical cavity are presented, both of which introduce elements of solvent structure. It is shown that both local models, one- and two-cavity, exhibit experimentally unobserved oscillations in the shorter time region t 1 ps for coumarin is obtained. The dynamics of the two-cavity model are not seen to differ from those of the one-cavity model. The nonlocal dynamic theory is shown to be able to suppress these oscillations, but the long-time asymptote differs markedly from that of the local theories. The nature of this asymptote is studied analytically

Proton tunnelling assisted by the intermolecular vibration excitation in solid state

The two-dimensional potential energy surface (PES) of the quasi-symmetric OHO fragment suggested earlier is used for treatment of proton transfer dynamics. The PES describes semi-quantitatively the main experimental regularities for a strong hydrogen bond. Strong coupling of modes (proton movement and O⋯O vibration) and dynamic asymmetry of the PES are taken into account. The respective wave equation was solved numerically with adiabatic separation of the "fast" (proton) and "slow" (O⋯O vibration) subsystems. Quantum jumps between vibrational levels of both subsystems under the random force action of the environment are assumed to realize the proton transfer from one well into another. The tunnel transitions between the "slow" subsystem levels. Corresponding to the proton localization in different wells, are most important, their probabilities depending strongly on the O⋯O equilibrium separation. At large O⋯O distances (≈2.64 Å) the total tunnel transition probability from definite O⋯O vibrational levels (m) of one well into all possible levels of the other well is shown to increase with m. Such a promotion of the proton tunnelling was observed by several authors at the laser selective vibrational excitation of the "slow" subsystem. For smaller O⋯O separation (≈2.52 Å) no vibrational assistance of the proton tunnelling occurs. The microscopic mechanism of the process for these two cases is interpreted in terms of the respective matrix elements. © 1992

Tentative study of the strong hydrogen bond dynamics. Part I. Geometric isotope effects

A qualitative interpretation is given to some dynamic effects of strong symmetric H bonds in terms of a new approximate potential energy surface model for the aha (ada) fragment. This surface is assumed to be common for different compounds containing the fragment aha (ada) with the same A atom. The proton potential is constructed from three parts joined together. The central part is the barrier separating two minima and the two side parts describe the proton repulsion from each A atom, the barrier width and height being dependent on the equilibrium A⋯A distance (Re). The proton (deuteron) energy terms are computed for three variants of such a potential energy surface using the adiabatic separation on the "fast" (proton, deuteron) and "slow" (A atoms) subsystems. This approximation enabled the geometric isotope effects to be computed for various compounds and Ichikawa's findings for these effects to be interpreted. © 1988

Tentative study of strong hydrogen bond dynamics. Part II. Vibrational frequency considerations

Experimental data on the O⋯O equilibrium distances Re (2.40 ≤ Re ≤ 2.69 Å) and the proton and deuteron stretching vibrational frequencies (vH and vD) for compounds with short hydrogen bonds OHO and ODO are tabulated. Data is included for compounds in which the proton (deuteron) moves in a potential having a symmetry centre. For compounds with 2.60 {less-than or approximate} Re ≤ 2.69 Å both symmetric and asymmetric hydrogen bonds are included. The earlier suggested (but slightly modified) mathematical model of the OHO (ODO) fragment potential-energy surface with a new set of fitting parameters was used for calculations of the proton and deuteron adiabatic terms EHυ and EDυ, as well as the Franck-Condon transition frequencies vH and vD as functions of Re. Simultaneously, the isotopic frequency ratio γ=vH/vD was calculated depending on vH. These dependencies are compared with respective distributions of the ca. 100 experimental points in order to assign the observed frequencies to respective transitions. The non-monotonic γ dependence on vH, as well as the low ({less-than or approximate}1) and high ( > 1.37) γ values are also interpreted. The same model was used to compute the following quantities as functions of Re: (a) the O⋯O equilibrium distance change on isotopic substitution ΔRRDe - RHe; (b) the δH distance between two points of maximum proton density in the double-well OHO potential: and (c) the isotopic difference ΔδδD-δH. A qualitative and in some cases semi-quantitative agreement with experiment was obtained. © 1990

Tentative study of strong hydrogen bond dynamics. Part II. Vibrational frequency considerations

Experimental data on the O⋯O equilibrium distances Re (2.40 ≤ Re ≤ 2.69 Å) and the proton and deuteron stretching vibrational frequencies (vH and vD) for compounds with short hydrogen bonds OHO and ODO are tabulated. Data is included for compounds in which the proton (deuteron) moves in a potential having a symmetry centre. For compounds with 2.60 {less-than or approximate} Re ≤ 2.69 Å both symmetric and asymmetric hydrogen bonds are included. The earlier suggested (but slightly modified) mathematical model of the OHO (ODO) fragment potential-energy surface with a new set of fitting parameters was used for calculations of the proton and deuteron adiabatic terms EHυ and EDυ, as well as the Franck-Condon transition frequencies vH and vD as functions of Re. Simultaneously, the isotopic frequency ratio γ=vH/vD was calculated depending on vH. These dependencies are compared with respective distributions of the ca. 100 experimental points in order to assign the observed frequencies to respective transitions. The non-monotonic γ dependence on vH, as well as the low ({less-than or approximate}1) and high ( > 1.37) γ values are also interpreted. The same model was used to compute the following quantities as functions of Re: (a) the O⋯O equilibrium distance change on isotopic substitution ΔRRDe - RHe; (b) the δH distance between two points of maximum proton density in the double-well OHO potential: and (c) the isotopic difference ΔδδD-δH. A qualitative and in some cases semi-quantitative agreement with experiment was obtained. © 1990

Tentative study of the strong hydrogen bond dynamics. Part I. Geometric isotope effects

A qualitative interpretation is given to some dynamic effects of strong symmetric H bonds in terms of a new approximate potential energy surface model for the aha (ada) fragment. This surface is assumed to be common for different compounds containing the fragment aha (ada) with the same A atom. The proton potential is constructed from three parts joined together. The central part is the barrier separating two minima and the two side parts describe the proton repulsion from each A atom, the barrier width and height being dependent on the equilibrium A⋯A distance (Re). The proton (deuteron) energy terms are computed for three variants of such a potential energy surface using the adiabatic separation on the "fast" (proton, deuteron) and "slow" (A atoms) subsystems. This approximation enabled the geometric isotope effects to be computed for various compounds and Ichikawa's findings for these effects to be interpreted. © 1988