Theoretical approach to the structure and hyperfine coupling constants of nonrigid radicals: the case of dihydronitrosyl radical

Barone, Vincenzo; Grand, André; Minichino, Camilla; Subra, R.

doi:10.1021/j100126a008

Cited by 45 publications

(38 citation statements)

References 2 publications

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“…These values, however, were obtained in a xenon matrix at a much lower temperature ͑77 K͒ than used in our simulation, and a rather strong temperature dependence of the hfcc's for H 2 NO in vacuo was found in Ref. 19. We note that the B3LYP/polarizable continuum model ͑PCM͒ study in Ref.…”

Section: Statistical Analysis Of Cpmd and MC Snapshotsmentioning

confidence: 49%

“…Later, Barone et al studied environmental effects by combining static hybrid densityfunctional theory calculations of the hyperfine coupling constants with classical polarizable continuum solvent models. 19 Although the dependence of the hyperfine coupling constants on the angle was investigated in that study, the vibrational effect on the average ESR parameters is not explicitly given. It was, however, mentioned there that in a related study on H 2 NO in vacuo 19 the vibrational averaging effect for the outof-plane vibration on this radical was small.…”

Section: Introductionmentioning

confidence: 99%

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Modeling solvent effects on electron-spin-resonance hyperfine couplings by frozen-density embedding

Neugebauer

Louwerse

Belanzoni

et al. 2005

The Journal of Chemical Physics

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In this study, we investigate the performance of the frozen-density embedding scheme within density-functional theory ͓J. Phys. Chem. 97, 8050 ͑1993͔͒ to model the solvent effects on the electron-spin-resonance hyperfine coupling constants ͑hfcc's͒ of the H 2 NO molecule. The hfcc's for this molecule depend critically on the out-of-plane bending angle of the NO bond from the molecular plane. Therefore, solvent effects can have an influence on both the electronic structure for a given configuration of solute and solvent molecules and on the probability for different solute ͑plus solvent͒ structures compared to the gas phase. For an accurate modeling of dynamic effects in solution, we employ the Car-Parrinello molecular-dynamics ͑CPMD͒ approach. A first-principles-based Monte Carlo scheme is used for the gas-phase simulation, in order to avoid problems in the thermal equilibration for this small molecule. Calculations of small H 2 NO-water clusters show that microsolvation effects of water molecules due to hydrogen bonding can be reproduced by frozen-density embedding calculations. Even simple sum-of-molecular-densities approaches for the frozen density lead to good results. This allows us to include also bulk solvent effects by performing frozen-density calculations with many explicit water molecules for snapshots from the CPMD simulation. The electronic effect of the solvent at a given structure is reproduced by the frozen-density embedding. Dynamic structural effects in solution are found to be similar to the gas phase. But the small differences in the average structures still induce significant changes in the computed shifts due to the strong dependence of the hyperfine coupling constants on the out-of-plane bending angle.

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Section: Statistical Analysis Of Cpmd and MC Snapshotsmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Modeling solvent effects on electron-spin-resonance hyperfine couplings by frozen-density embedding

Neugebauer

Louwerse

Belanzoni

et al. 2005

The Journal of Chemical Physics

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“…However, sophisticated POSt-HF methods, needed (especially for u radicals) to obtain accurate spin-dependent properties, are so expensive that their extension to relatively large systems is questionable [ 6 , 7 ] . In such circumstances, alternative theoretical tools, like the density functional (DF) approach, could be more effective [8]. The interest in the DF approach originates from two factors: (a) It requires a smaller amount of external memory than does conventional post-HF methods and (b) a number of recent DF studies [9,10] …”

Section: Introductionmentioning

confidence: 99%

Density functional theory: An effective theoretical tool for the study of σ radicals

Barone

Adamo

Russo

1994

Int J of Quantum Chemistry

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The structures, harmonic force fields, and hyperfine coupling constants of a number of representative cr radicals have been investigated by the density functional approach including nonlocal corrections. Scaling of CH bond lengths and stretching constants leads to accurate structures and force fields. Hyperfine coupling constants reach, at least, the level of the most sophisticated conventional post-Hartree-Fock models. This suggests that the density functional approach is a promising theoretical tool for the study of relationships between structure and spectroscopic properties of large free radicals.

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“…According to Ref. [59], in 2,2,4,4-tetramethyl-substituted nitroxides this correction may be of a iso ( 14 N) vibr ≈ 1 G.…”

Section: Isotropic Hyperfine Splitting Constantmentioning

confidence: 99%

DFT study of nitroxide radicals: explicit modeling of solvent effects on the structural and electronic characteristics of 4‐amino‐2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl

Ikryannikova

Ustynyuk

Тихонов

2010

Magnetic Reson in Chemistry

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An explicit DFT modeling of water surroundings on the electron paramagnetic resonance properties of 4-amino-2,2,6,6-tetramethyl-piperidine-N-oxyl (TA) has been performed. A stepwise hydration of TA is accompanied with certain changes in geometrical parameters (bond lengths and angles) and redistribution of partial electric charges in TA. An aqueous cluster of 45 water molecules can be considered as an appropriate model for a complete aqueous shell around TA, although most of the structural and electronic characteristics of TA already converge at about 10 water molecules. Water surroundings induce an increase in electron spin density on the nitrogen atom of the nitroxide fragment due to stabilization of the polar resonance structure > N(+*)-O(-) at the expense of less polar structure > N-O*. The water-induced rise of the isotropic splitting constant a(iso), calculated from the contact term of the hyperfine interaction, comprises Deltaa(iso)(rho(N2)) = 2.2-2.5 G, which is typical of experimental value for TA. There are two contributions to the solvent effect on the a(iso)(rho(N2)) value: the redistribution of spin density in the nitroxide fragment (polarity effect) and water-induced distortions of TA geometry. Microscopic variations in a hydrogen-bonded water network cause noticeable fluctuations of the splitting constant a(iso)(rho(N2)). Calculations of the atomic spin density (sigma(N2)) allowed us to compute the splitting constant from the relationship a(iso)(sigma(N2)) = Qsigma(N2), where Q = 36.2 G. A practical advantage of using this relationship is that it gives 'smoothed' values of the splitting constant, which are sensitive to the environment polarity but remain tolerant to microscopic fluctuations of the hydrogen-bonded water network around a spin-label molecule.

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Theoretical approach to the structure and hyperfine coupling constants of nonrigid radicals: the case of dihydronitrosyl radical

Cited by 45 publications

References 2 publications

Modeling solvent effects on electron-spin-resonance hyperfine couplings by frozen-density embedding

Modeling solvent effects on electron-spin-resonance hyperfine couplings by frozen-density embedding

Density functional theory: An effective theoretical tool for the study of σ radicals

DFT study of nitroxide radicals: explicit modeling of solvent effects on the structural and electronic characteristics of 4‐amino‐2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl

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