Quantum chemical study on spin-polarized molecular wire using elongation method

Recently, spin-polarized molecular wire has created considerable interest for their potential application to a useful quantum device. The unique property of spin-polarized donor (1-pyrrolylphenyl nitronyl nitroxide) that NHOMO(β) is higher than SOMO(α) can be explained by the strong interaction between HOMO(β) of donor part and NHOMO(β) of radical part. Elongation method can be a powerful tool to calculate efficiently the electronic structure of huge systems with good accuracy. We applied this treatment to calculate the electronic structure of spin-polarized molecular wire under an applied electric field. It was found that the pyrrole ring in "donor part" causes the delocalization of electrons over the molecular wire. Radical part (nitronyl nitroxide) shows two important properties. One is to change the spin-distribution from same ratio of α and β-spins to dominant β-spin. Another one is to shift the distribution of electrons to the same direction as the applied electric field.