title: Understanding the ring current effects on magnetic shielding of hydrogen and carbon nuclei in naphthalene and anthracene.
abstract: The local response to an external magnetic field normal to the molecular plane of naphthalene and anthracene was investigated via current density and magnetic shielding density maps. The Biot-Savart law shows that the deshielding caused by pi-ring currents in naphthalene is stronger for alpha- than for beta-protons due to geometrical factors. The shielding tensor of the carbon nuclei in both molecules is strongly anisotropic and its out-of-plane component determines the up-field chemical shift of (13)C in nuclear magnetic resonance spectra. The pi-ring currents flowing beyond the C-skeleton in front of a probe carbon nucleus, and on remote parts of the molecular perimeter, yield positive contributions to the out-of-plane component of carbon shielding as big as approximately 10-15% of the total values. Near Hartree-Fock estimates of magnetizability and magnetic shielding at the nuclei fully consistent with the current model are reported.
authors: Institut de Ciència Molecular, Universitat de València, P.O. Box 22085, E-46071 València, Spain.
authors: Inmaculada Garíca
authors: IG
authors: Cuesta
authors: Alfredo Sánchez
authors: AS
authors: De Merás
authors: Stefano
authors: S
authors: Pelloni
authors: Paolo
authors: P
authors: Lazzeretti