  Starting from the structure of the (TTM-TTP)I_3 molecular-based material, we
examine the characteristics of frontier molecular orbitals using ab initio
(CASSCF/CASPT2) configurations interaction calculations. It is shown that the
singly-occupied and second-highest-occupied molecular orbitals are close to
each other, i.e., this compound should be regarded as a two-orbital system. By
dividing virtually the [TTM-TTP] molecule into three fragments, an effective
model is constructed to rationalize the origin of this picture. In order to
investigate the low-temperature symmetry breaking experimentally observed in
the crystal, the electronic distribution in a pair of [TTM-TTP] molecules is
analyzed from CASPT2 calculations. Our inspection supports and explains the
speculated intramolecular charge ordering which is likely to give rise to
low-energy magnetic properties.
