  In this paper, we present a study of the electric transport properties of
small discrete rings with $3\leq N\leq 6$ sites and $N_{e}<2N$ electrons, which
can be seen as a simplified version of real aromatic molecules. In particular,
the ring with six sites and six electrons is our prototype of the benzene
molecule. It is already known that the Hubbard model itself cannot account for
the anisotropy of the diamagnetic susceptibility of the aromatic molecules,
which is observed when they are subjected to an external magnetic field
perpendicular to their basal plane. Therefore, we propose an extension of the
Hubbard model, with an ad hoc extra interaction term, with two adjustable
parameters. Our results show that this extension of the Hubbard model is able
to amplify the persistent currents established in the ground state of our rings
and, moreover, promotes an enhancement of the magnetic susceptibility
anisotropy depending on the tuning of the adjustable parameters. In particular,
for the prototype of the benzene molecule, we recover the order of magnitude of
the diamagnetic anisotropy measured for this molecule.
