Antiferromagnetic Exchange Interaction between Electrons on Degenerate LUMOs in Benzene Dianion

We discuss the ground state of Benzene dianion (Bz${}^{2-}$) on the basis of the numerical diagonalization method of an effective model of $\pi$ orbitals. It is found that the ground state can be the spin singlet state, and the exchange coupling between LUMOs can be antiferromagnetic.