Density functional theory study of the conductivity of the biphenalenyl radical dimer

Abstract

We present ab initio molecular calculations at different levels of density functional theory (DFT) for the spiro-biphenalenyl neurtral radical in its singlet and triplet states. We performed calculations on the dimer to study its conductivity by investigating the ground state energy, HOMO-LUMO gap, charge localization, and reorganization energies, as these are the main contributing factors to crystal conduction. We find that there is only a slight difference between the singlet state and triplet state HOMO-LUMO gaps. In addition, the negative charge spreads throughout both the interior and exterior units of the molecule in both the singlet state and the triplet state, this is in disagreement with the original argument that the conducting diamagnetic state is a result of the migration of the unpaired electrons to the interior units of the molecule. Finally, we find that the triplet state has higher reorganization energy than that of the singlet. Thus, if conduction were assumed to proceed via a hopping mechanism, the experimental observations would be explained.