Computational methods based on continuous transformation of the origin of current densities have been employed at the coupled Hartree-Fock level of accuracy to calculate magnetic susceptibility and carbon and hydrogen nuclear magnetic shielding in the naphthalene molecule. Different schemes based on formal annihilation of the conventional expressions for either diamagnetic or paramagnetic contributions to the current density have been tested. The first three-dimensional model for circulation of both sigma and pi electrons in naphthalene is presented via diagrams showing streamlines, stagnation lines and modulus of the current density induced by a magnetic field perpendicular to the molecular plane. The new topological model outlined in the present work provides a significant step forward with respect to previous findings, useful in rationalizing the magnetic properties of the naphthalene molecule. The theoretical values of proton magnetic shielding indicate that the chemical shift observed experimentally between magnetically non-equivalent hydrogens is entirely due to deshielding of the out-of-plane component of sigma(H).

Ring current model of the naphthalene molecule

ZANASI, Riccardo;
1997

Abstract

Computational methods based on continuous transformation of the origin of current densities have been employed at the coupled Hartree-Fock level of accuracy to calculate magnetic susceptibility and carbon and hydrogen nuclear magnetic shielding in the naphthalene molecule. Different schemes based on formal annihilation of the conventional expressions for either diamagnetic or paramagnetic contributions to the current density have been tested. The first three-dimensional model for circulation of both sigma and pi electrons in naphthalene is presented via diagrams showing streamlines, stagnation lines and modulus of the current density induced by a magnetic field perpendicular to the molecular plane. The new topological model outlined in the present work provides a significant step forward with respect to previous findings, useful in rationalizing the magnetic properties of the naphthalene molecule. The theoretical values of proton magnetic shielding indicate that the chemical shift observed experimentally between magnetically non-equivalent hydrogens is entirely due to deshielding of the out-of-plane component of sigma(H).
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/3133108
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