Theoretical Studies on the Benzene Molecule: Magnetic Susceptibility and Nuclear Shielding Constants

Coupled Hartree–Fock perturbation theory is employed to evaluate the magnetic susceptibility, proton and carbon shielding constants, and their gauge dependence in benzene within the framework of an LCAO approach retaining 198 CGTO's as the basis set. The magnetic properties are rationalized by analyzing the orbital contributions: the theoretical results indicate that an important role is played by pi electrons, which largely contribute to the determination of the bulk of magnetic susceptibility and shieldings. The basic soundness of the ring current model for benzene seems to have been confirmed, but our findings demonstrate that also local electron circulations provide significant deshielding effects on the proton chemical shift and a relevant contribution to the in-plane susceptibility.