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Trygve Helgaker - One of the best experts on this subject based on the ideXlab platform.

  • calculation of nmr spin spin Coupling constants in strychnine
    Journal of Organic Chemistry, 2016
    Co-Authors: Trygve Helgaker, Michal Jaszunski, Pawel świder
    Abstract:

    We compare the NMR indirect nuclear spin–spin Coupling constants in strychnine calculated using density functional theory (DFT) with the semiempirical relativistic force field (RFF) method of Kutateladze and Mukhina (KM) (J. Org. Chem. 2015, 80, 10838–10848). DFT values significantly more accurate than those obtained by KM for their comparison with RFF values can be obtained, at a lower cost, by an appropriate selection of basis set.

  • The NMR indirect nuclear spin–spin Coupling constant of the HD molecule
    Molecular Physics, 2012
    Co-Authors: Trygve Helgaker, Michał Jaszuński, Piotr Garbacz, Karol Jackowski
    Abstract:

    We present new calculated and experimental values of the NMR indirect nuclear spin–spin Coupling constant in HD. In the quantum-chemical ab initio calculations, the full configuration-interaction (FCI) method is used, yielding an equilibrium value of 41.22 Hz in the basis-set limit. Adding a calculated zero-point vibrational correction of 1.89 Hz and a temperature correction of 0.20 Hz at 300 K, we obtain a total calculated spin–spin Coupling constant of J FCI(HD) = 43.31(5) Hz at 300 K. This result is within the error bars of the experimental gas-phase NMR value, J exp(HD) = 43.26(6) Hz, obtained by extrapolating values measured in HD–He mixtures to zero density.

  • Spin–spin Coupling constants and triplet instabilities in Kohn–Sham theory
    Molecular Physics, 2010
    Co-Authors: Ola B. Lutnæs, Trygve Helgaker, Michał Jaszuński
    Abstract:

    Indirect nuclear spin–spin Coupling constants calculated using restricted Hartree–Fock theory are unreliable since the usually dominant Fermi-contact (FC) contribution arises from a triplet perturbation of the electronic system, poorly described in the Hartree–Fock theory – in particular, at geometries close to the onset of triplet instabilities. These problems are usually but not invariably overcome in Kohn–Sham theory, which typically provides good spin–spin Coupling constants. We here examine the sensitivity of spin–spin Coupling constants to triplet instabilities in Kohn–Sham and Hartree–Fock theories by correlating the quality of the spin–spin Coupling constants and the quality of the lowest triplet excitation energy for a number of small molecules. In general, the FC contributions are most stable in the local density approximation (LDA) and slightly less stable in the generalised gradient approximation (GGA); on the other hand, GGA Coupling constants are usually more accurate than LDA constants. Imp...

  • INVITED ARTICLE Spin-Spin Coupling constants and triplet instabilities in Kohn-Sham theory
    2010
    Co-Authors: Ola B. Lutnæs, Trygve Helgaker
    Abstract:

    Indirect nuclear spin‐spin Coupling constants calculated using restricted Hartree‐Fock theory are unreliable since the usually dominant Fermi-contact (FC) contribution arises from a triplet perturbation of the electronic system, poorly described in the Hartree‐Fock theory ‐ in particular, at geometries close to the onset of triplet instabilities. These problems are usually but not invariably overcome in Kohn‐Sham theory, which typically provides good spin‐spin Coupling constants. We here examine the sensitivity of spin‐spin Coupling constants to triplet instabilities in Kohn‐Sham and Hartree‐Fock theories by correlating the quality of the spin‐spin Coupling constants and the quality of the lowest triplet excitation energy for a number of small molecules. In general, the FC contributions are most stable in the local density approximation (LDA) and slightly less stable in the generalised gradient approximation (GGA); on the other hand, GGA Coupling constants are usually more accurate than LDA constants. Importantly, although hybrid theory often gives better results than the GGA theory, it is also more susceptible to triplet instabilities (inheriting some of the problems of the Hartree‐Fock theory) and therefore less reliable than the GGA theory for spin‐spin Coupling constants. For calculations of spin‐spin Coupling constants, we recommend the Perdew‐Burke‐Ernzerhof GGA exchange-correlation functional, which provides a good compromise of accuracy and robustness.

  • The calculation of indirect nuclear Spin-Spin Coupling constants in large molecules.
    Chemistry - A European Journal, 2004
    Co-Authors: Mark A. Watson, Michał Jaszuński, Paweł Sałek, Peter Macak, Trygve Helgaker
    Abstract:

    We present calculations of indirect nuclear Spin-Spin Coupling constants in large molecular systems, performed using density functional theory. Such calculations, which have become possible because of the use of linear-scaling techniques in the evaluation of the Coulomb and exchange-correlation contributions to the electronic energy, allow us to study indirect Spin-Spin Couplings in molecules of biological interest, without having to construct artificial model systems. In addition to presenting a statistical analysis of the large number of short-range Coupling constants in large molecular systems, we analyse the asymptotic dependence of the indirect nuclear Spin-Spin Coupling constants on the internuclear separation. In particular, we demonstrate that, in a sufficiently large one-electron basis set, the indirect Spin-Spin Coupling constants become proportional to the inverse cube of the internuclear separation, even though the diamagnetic and paramagnetic spin-orbit contributions to the Spin-Spin Coupling constants separately decay as the inverse square of this separation. By contrast, the triplet Fermi contact and spin-dipole contributions to the indirect Spin-Spin Coupling constants decay exponentially and as the inverse cube of the internuclear separation, respectively. Thus, whereas short-range indirect Spin-Spin Coupling constants are usually dominated by the Fermi contact contribution, long-range Coupling constants are always dominated by the negative diamagnetic spin-orbit contribution and by the positive paramagnetic spin-orbit contribution, with small spin-dipole and negligible Fermi contact contributions.

Michał Jaszuński - One of the best experts on this subject based on the ideXlab platform.

  • The NMR indirect nuclear spin–spin Coupling constant of the HD molecule
    Molecular Physics, 2012
    Co-Authors: Trygve Helgaker, Michał Jaszuński, Piotr Garbacz, Karol Jackowski
    Abstract:

    We present new calculated and experimental values of the NMR indirect nuclear spin–spin Coupling constant in HD. In the quantum-chemical ab initio calculations, the full configuration-interaction (FCI) method is used, yielding an equilibrium value of 41.22 Hz in the basis-set limit. Adding a calculated zero-point vibrational correction of 1.89 Hz and a temperature correction of 0.20 Hz at 300 K, we obtain a total calculated spin–spin Coupling constant of J FCI(HD) = 43.31(5) Hz at 300 K. This result is within the error bars of the experimental gas-phase NMR value, J exp(HD) = 43.26(6) Hz, obtained by extrapolating values measured in HD–He mixtures to zero density.

  • Spin–spin Coupling constants and triplet instabilities in Kohn–Sham theory
    Molecular Physics, 2010
    Co-Authors: Ola B. Lutnæs, Trygve Helgaker, Michał Jaszuński
    Abstract:

    Indirect nuclear spin–spin Coupling constants calculated using restricted Hartree–Fock theory are unreliable since the usually dominant Fermi-contact (FC) contribution arises from a triplet perturbation of the electronic system, poorly described in the Hartree–Fock theory – in particular, at geometries close to the onset of triplet instabilities. These problems are usually but not invariably overcome in Kohn–Sham theory, which typically provides good spin–spin Coupling constants. We here examine the sensitivity of spin–spin Coupling constants to triplet instabilities in Kohn–Sham and Hartree–Fock theories by correlating the quality of the spin–spin Coupling constants and the quality of the lowest triplet excitation energy for a number of small molecules. In general, the FC contributions are most stable in the local density approximation (LDA) and slightly less stable in the generalised gradient approximation (GGA); on the other hand, GGA Coupling constants are usually more accurate than LDA constants. Imp...

  • 19F spin–spin Coupling in peri-difluoronaphthalene
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: Michał Jaszuński, Juha Vaara
    Abstract:

    We report first-principles electronic structure calculations of the nuclear magnetic resonance (NMR) Spin-Spin Coupling tensors to the (19)F nucleus in peri-difluoronaphthalene. This system was recently subjected by Emsley and co-workers to an experimental liquid crystal NMR study, and the 4-bond (19)F(19)F Coupling was found to have a significant anisotropic contribution. We use density-functional theory (DFT) with different exchange-correlation functionals and the polarisation-consistent basis sets optimised for J-Coupling, as well as the second-order polarization propagator approximation, to calculate all the Coupling tensors involving the (19)F nuclei in this molecule. The tensor components, combined with the experimental orientation tensor, confirm the sign and order of magnitude of the anisotropic part of the Spin-Spin Coupling: the value derived experimentally is -31.6 Hz versus our different quantum chemical results at around -10 Hz. Besides the (4)J(FF) tensor, significant anisotropic contributions are found also for the long-range (13)C(19)F and (1)H(19)F Coupling tensors.

  • Temperature dependence of the 1J(11B19F) spin–spin Coupling in BF3 molecule
    Magnetic Resonance in Chemistry, 2009
    Co-Authors: Karol Jackowski, Włodzimierz Makulski, Anna Szyprowska, Andrej Antušek, Michał Jaszuński
    Abstract:

    The 1J(11B19F) spin–spin Coupling of gaseous BF3 was observed in 11B NMR spectra as a function of density in a wide range of temperatures. Following the extrapolation of the measured values to the zero-density limit, the Coupling constant free from intermolecular effects 1J0(11B19F) was obtained for each temperature. In contrast to previous investigations, the final results indicate a nonlinear dependence of 1J0(11B19F) on temperature. In the corresponding ab initio calculations of spin–spin Coupling constants performed at the coupled cluster singles and doubles (CCSD) level to obtain a reliable result for this Coupling constant we had to take into account large vibrational corrections. Copyright © 2009 John Wiley & Sons, Ltd.

  • The calculation of indirect nuclear Spin-Spin Coupling constants in large molecules.
    Chemistry - A European Journal, 2004
    Co-Authors: Mark A. Watson, Michał Jaszuński, Paweł Sałek, Peter Macak, Trygve Helgaker
    Abstract:

    We present calculations of indirect nuclear Spin-Spin Coupling constants in large molecular systems, performed using density functional theory. Such calculations, which have become possible because of the use of linear-scaling techniques in the evaluation of the Coulomb and exchange-correlation contributions to the electronic energy, allow us to study indirect Spin-Spin Couplings in molecules of biological interest, without having to construct artificial model systems. In addition to presenting a statistical analysis of the large number of short-range Coupling constants in large molecular systems, we analyse the asymptotic dependence of the indirect nuclear Spin-Spin Coupling constants on the internuclear separation. In particular, we demonstrate that, in a sufficiently large one-electron basis set, the indirect Spin-Spin Coupling constants become proportional to the inverse cube of the internuclear separation, even though the diamagnetic and paramagnetic spin-orbit contributions to the Spin-Spin Coupling constants separately decay as the inverse square of this separation. By contrast, the triplet Fermi contact and spin-dipole contributions to the indirect Spin-Spin Coupling constants decay exponentially and as the inverse cube of the internuclear separation, respectively. Thus, whereas short-range indirect Spin-Spin Coupling constants are usually dominated by the Fermi contact contribution, long-range Coupling constants are always dominated by the negative diamagnetic spin-orbit contribution and by the positive paramagnetic spin-orbit contribution, with small spin-dipole and negligible Fermi contact contributions.

Karol Jackowski - One of the best experts on this subject based on the ideXlab platform.

  • The NMR indirect nuclear spin–spin Coupling constant of the HD molecule
    Molecular Physics, 2012
    Co-Authors: Trygve Helgaker, Michał Jaszuński, Piotr Garbacz, Karol Jackowski
    Abstract:

    We present new calculated and experimental values of the NMR indirect nuclear spin–spin Coupling constant in HD. In the quantum-chemical ab initio calculations, the full configuration-interaction (FCI) method is used, yielding an equilibrium value of 41.22 Hz in the basis-set limit. Adding a calculated zero-point vibrational correction of 1.89 Hz and a temperature correction of 0.20 Hz at 300 K, we obtain a total calculated spin–spin Coupling constant of J FCI(HD) = 43.31(5) Hz at 300 K. This result is within the error bars of the experimental gas-phase NMR value, J exp(HD) = 43.26(6) Hz, obtained by extrapolating values measured in HD–He mixtures to zero density.

  • Temperature dependence of the 1J(11B19F) spin–spin Coupling in BF3 molecule
    Magnetic Resonance in Chemistry, 2009
    Co-Authors: Karol Jackowski, Włodzimierz Makulski, Anna Szyprowska, Andrej Antušek, Michał Jaszuński
    Abstract:

    The 1J(11B19F) spin–spin Coupling of gaseous BF3 was observed in 11B NMR spectra as a function of density in a wide range of temperatures. Following the extrapolation of the measured values to the zero-density limit, the Coupling constant free from intermolecular effects 1J0(11B19F) was obtained for each temperature. In contrast to previous investigations, the final results indicate a nonlinear dependence of 1J0(11B19F) on temperature. In the corresponding ab initio calculations of spin–spin Coupling constants performed at the coupled cluster singles and doubles (CCSD) level to obtain a reliable result for this Coupling constant we had to take into account large vibrational corrections. Copyright © 2009 John Wiley & Sons, Ltd.

  • 13c and 1h nuclear magnetic shielding and spin spin Coupling constants of 13c enriched bromomethane in the gas phase
    Chemical Physics Letters, 2007
    Co-Authors: Karol Jackowski, Marek Kubiszewski, Marcin Wilczek
    Abstract:

    Abstract 13 C and 1 H NMR spectral parameters are investigated for 13 CH 3 Br in gaseous matrices. It is found that both the 13 C and 1 H chemical shifts of 13 CH 3 Br are linearly dependent on solvent density. Similar dependence is also detected for one-bond spin–spin Coupling, 1 J (CH). For the first time the 13 C and 1 H magnetic shielding constants and 1 J (CH) spin–spin Coupling are obtained for an isolated 13 CH 3 Br molecule together with the coefficients responsible for solute–solvent molecular interactions in gaseous matrices. The present experimental results confirm the accuracy of some recent ab initio calculations of nuclear magnetic shielding performed for bromomethane.

  • 13C and 1H nuclear magnetic shielding and spin–spin Coupling constants of 13C-enriched bromomethane in the gas phase
    Chemical Physics Letters, 2007
    Co-Authors: Karol Jackowski, Marek Kubiszewski, Marcin Wilczek
    Abstract:

    Abstract 13 C and 1 H NMR spectral parameters are investigated for 13 CH 3 Br in gaseous matrices. It is found that both the 13 C and 1 H chemical shifts of 13 CH 3 Br are linearly dependent on solvent density. Similar dependence is also detected for one-bond spin–spin Coupling, 1 J (CH). For the first time the 13 C and 1 H magnetic shielding constants and 1 J (CH) spin–spin Coupling are obtained for an isolated 13 CH 3 Br molecule together with the coefficients responsible for solute–solvent molecular interactions in gaseous matrices. The present experimental results confirm the accuracy of some recent ab initio calculations of nuclear magnetic shielding performed for bromomethane.

  • Shielding and Spin-Spin Coupling constants from gas-phase NMR
    Applied Magnetic Resonance, 2003
    Co-Authors: Karol Jackowski
    Abstract:

    Intermolecular interactions modify nuclear magnetic resonance (NMR) chemical shifts and Spin-Spin Coupling constants. The intermolecular effects can be determined if the NMR parameters for an isolated molecule are known. Gas-phase NMR spectroscopy offers such methods which allow one to measure the shielding and Spin-Spin Coupling constants at the zero-density limit where the NMR parameters are free from intermolecular contributions. It is also shown that at present the multinuclear NMR spectra can easily be obtained for gaseous samples containing several micrograms of a solute compound.

Frank Jensen - One of the best experts on this subject based on the ideXlab platform.

  • development of polarization consistent basis sets for spin spin Coupling constant calculations for the atoms li be na and mg
    Journal of Chemical Physics, 2018
    Co-Authors: Patrick Alexander Aggelund, Stephan P A Sauer, Frank Jensen
    Abstract:

    The pcJ-n basis set, optimized for Spin-Spin Coupling constant calculations using density functional theory methods, are expanded to also include the s-block elements Li, Be, Na, and Mg, by studyin...

  • The optimum contraction of basis sets for calculating spin–spin Coupling constants
    Theoretical Chemistry Accounts, 2009
    Co-Authors: Frank Jensen
    Abstract:

    The previously proposed pcJ-n basis sets, optimized for calculating indirect nuclear spin–spin Coupling constants using density functional methods, are re-evaluated for finding the optimum contraction scheme as a compromise between computational efficiency and minimizing contraction errors. An exhaustive search is performed for the H2, F2 and P2 molecules, and candidates for optimum contraction schemes are evaluated for a larger test set of 21 molecules. Using the criterion that the contraction error should not exceed the basis set error relative to the basis set limit, the optimum contraction is defined for each basis set. The results show that it is difficult to contract basis sets for calculating spin–spin Coupling constants to any significant degree without losing the inherent accuracy. The work provides guidelines for searching for optimum contraction schemes for other properties and/or at theoretical levels where a systematic search is impractical.

  • Optimization of augmentation functions for correlated calculations of Spin-Spin Coupling constants and related properties
    The Journal of Chemical Physics, 2008
    Co-Authors: Udo Benedikt, Alexander A. Auer, Frank Jensen
    Abstract:

    A new hierarchy of augmented basis sets optimized for the calculation of molecular properties such as indirect Spin-Spin Coupling constants is presented. Based on the Dunning hierarchy of cc-pVXZ (X=D, T, Q, and 5) basis sets augmentation functions with tight exponents have been optimized for coupled-cluster calculations of indirect Spin-Spin Coupling constants. The optimal exponents for these tight functions have been obtained by optimizing the sum of the absolute values of all contributions to the Coupling constant. On the basis of a series of test cases (CO, HF, N2, F2, H2O, NH3, and CH4) we propose a set of tight s, p, and d functions to be added to the uncontracted Dunning basis sets, and, subsequently, to recontract. The resulting ccJ-pVXZ (X=D, T, Q, and 5) basis sets demonstrate excellent cost efficiency in benchmark calculations. These new basis sets should generally be applicable for the calculation of Spin-Spin Coupling constants and other properties that have a strong dependence on powers of 1...

  • Optimized Basis Sets for Calculating Spin‐Spin Coupling Constants
    AIP Conference Proceedings, 2008
    Co-Authors: Udo Benedikt, Alexander A. Auer, Frank Jensen
    Abstract:

    We propose a series of basis sets for systematically reducing the basis set error for calculating nuclear spin‐spin Coupling constants. At the density functional level, the basis sets are derived from the previously proposed polarization consistent basis sets by augmentation with tight s‐, p‐, d‐ and f‐functions. The optimum exponents for the tight functions can be derived by a variational procedure, and the optimum exponents are sufficiently regular that a standard set of tight functions can be derived. Preliminary results at the coupled cluster level suggest that a similar sequence of optimum basis sets can be derived from the correlation consistent basis sets by augmentation with tight functions.

  • The Basis Set Convergence of Spin-Spin Coupling Constants Calculated by Density Functional Methods.
    Journal of Chemical Theory and Computation, 2006
    Co-Authors: Frank Jensen
    Abstract:

    The previously proposed polarization-consistent basis sets, optimized for density functional calculations, are evaluated for calculating indirect nuclear Spin-Spin Coupling constants. The basis set limiting values can be obtained by performing a series of calculations with increasingly larger basis sets, but the convergence can be significantly improved by adding functions with large exponents. An accurate calculation of the Fermi-contact contribution requires the addition of tight s functions, while the paramagnetic spin-orbit contribution is sensitive to the presence of tight p functions. The spin-dipolar contribution requires the addition of p, d, and f functions. The optimal exponents for the tight functions can be obtained by optimizing the absolute sum of all contributions to the Spin-Spin Coupling constant. On the basis of a series of test cases, we propose a standard set of tight s, p, d, and f functions to be added to the polarization-consistent basis sets. The resulting pcJ-n basis sets should be suitable for calculating Spin-Spin Coupling constants with density functional methods.

Stephan P A Sauer - One of the best experts on this subject based on the ideXlab platform.

  • development of polarization consistent basis sets for spin spin Coupling constant calculations for the atoms li be na and mg
    Journal of Chemical Physics, 2018
    Co-Authors: Patrick Alexander Aggelund, Stephan P A Sauer, Frank Jensen
    Abstract:

    The pcJ-n basis set, optimized for Spin-Spin Coupling constant calculations using density functional theory methods, are expanded to also include the s-block elements Li, Be, Na, and Mg, by studyin...

  • First example of a high-level correlated calculation of the indirect spin–spin Coupling constants involving tellurium: tellurophene and divinyl telluride
    Physical Chemistry Chemical Physics, 2013
    Co-Authors: Yury Yu. Rusakov, Stephan P A Sauer, Leonid B. Krivdin, Freja From Østerstrøm, Vladimir A. Potapov, Svetlana V. Amosova
    Abstract:

    This paper documents the very first example of a high-level correlated calculation of spin–spin Coupling constants involving tellurium taking into account relativistic effects, vibrational corrections and solvent effects for medium sized organotellurium molecules. The 125Te–1H spin–spin Coupling constants of tellurophene and divinyl telluride were calculated at the SOPPA and DFT levels, in good agreement with experimental data. A new full-electron basis set, av3z-J, for tellurium derived from the “relativistic” Dyall's basis set, dyall.av3z, and specifically optimized for the correlated calculations of spin–spin Coupling constants involving tellurium was developed. The SOPPA method shows a much better performance compared to DFT, if relativistic effects calculated within the ZORA scheme are taken into account. Vibrational and solvent corrections are next to negligible, while conformational averaging is of prime importance in the calculation of 125Te–1H spin–spin Couplings. Based on the performed calculations at the SOPPA(CCSD) level, a marked stereospecificity of geminal and vicinal 125Te–1H spin–spin Coupling constants originating in the orientational lone pair effect of tellurium has been established, which opens a new guideline in organotellurium stereochemistry.

  • Electric field effects on nuclear spin–spin Coupling tensors and chiral discrimination via NMR spectroscopy
    Theoretical Chemistry Accounts, 2010
    Co-Authors: Gabriel I. Pagola, Paolo Lazzeretti, Marta B. Ferraro, Stefano Pelloni, Stephan P A Sauer
    Abstract:

    Nuclear magnetic resonance spectrometers presently available are unable to recognize the two mirror-image forms of a chiral molecule, because in the absence of a chiral solvent, the NMR spectral parameters (chemical shifts and spin–spin Coupling constants) are identical for the two enantiomers. This paper discusses how chirality may nevertheless, at least in theory, be recognized in liquid-state NMR spectroscopy by applying strong d.c. electric fields and measuring a pseudoscalar contribution to nuclear spin–spin Coupling polarizability. Calculations are reported for medium-size chiral molecules, (2R)-N-methyloxaziridine, (R a )-1,3-dimethylallene, and (2R)-2-methyloxirane. The very small contributions provided by the pseudoscalar of nuclear spin–spin Coupling polarizability seem rather difficult to detect via NMR experiments in disordered phase

  • Structural trends of 77Se-1H Spin-Spin Coupling constants and conformational behavior of 2-substituted selenophenes.
    Magnetic Resonance in Chemistry, 2009
    Co-Authors: Yury Yu. Rusakov, Stephan P A Sauer, Leonid B. Krivdin, E. P. Levanova, Galina G. Levkovskaya
    Abstract:

    Experimental measurements and second-order polarization propagator approach (SOPPA) calculations of (77)Se-(1)H Spin-Spin Coupling constants together with theoretical energy-based conformational analysis in the series of 2-substituted selenophenes have been carried out. A new basis set optimized for the calculation of (77)Se-(1)H Spin-Spin Coupling constants has been introduced by extending the aug-cc-pVTZ-J basis for selenium. Most of the Spin-Spin Coupling constants under study, especially vicinal (77)Se-(1)H Couplings, demonstrated a remarkable stereochemical behavior with respect to the internal rotation of the substituent in the 2-position of the selenophene ring, which is of major importance in the stereochemical studies of the related organoselenium compounds.

  • Prediction of Spin-Spin Coupling constants in solution based on combined density functional theory/molecular mechanics
    The Journal of Chemical Physics, 2009
    Co-Authors: Andreas Møgelhøj, Stephan P A Sauer, Kestutis Aidas, Kurt V. Mikkelsen, Jacob Kongsted
    Abstract:

    We present theory and implementation of calculation of Spin-Spin Coupling constants within combined quantum mechanics/molecular mechanics methods. Special attention is given to the role of explicit solvent polarization as well as the molecular consequences due to hydrogen bonding. The model is generally applicable but is here implemented for the case of density functional theory. First applications to liquid water and acetylene in aqueous solution are presented. Good agreement between theory and experiment is obtained in both cases, thereby showing the strength of our approach. Finally, Spin-Spin Coupling constants across hydrogen bonds are discussed considering for the first time the role of an explicit solvent on this class of Spin-Spin Couplings.