Theoretical Investigation of the Dependence of Exchange Interaction on Dihedral Angle between Two Aromatic Rings in a Wire Unit

Abstract

Abstract The dependence of intramolecular exchange interaction on dihedral angle between two aromatic rings in a wire unit was investigated by using broken-symmetry UDFT (BS-UDFT) calculation. Biphenyl rings and 2,2′-bithiophene rings were used for molecular rods and nitronyl nitroxide and verdazyl were chosen as organic radical species. The exchange interaction was proportional to cos2 θ where θ is the dihedral angle between two aromatic rings. This result shows good agreement with the dependence of conductance on dihedral angle between two phenyl rings. Our calculation strongly suggests the similarity of molecular conductance and intramolecular exchange interaction and reinforced the existence of an electron-tunneling mechanism underlying two physical properties.