Effect of Applied Voltage on the Geometrical and Electronic Structures of Dipyrimidinyl−Diphenyl Diblock as a Molecular Diode: A DFT Study

Abstract

The effect of an external electric field on the geometrical and electronic structures of the nonsymmetrical dipyrimidinyl−diphenyl (DPDPh) molecule has been investigated using B3LYP density functional theory (DFT) in the absence and presence of an electric field in an attempt to rationalize its rectifying behavior. A detailed comparison with the isoelectronic symmetrical tetraphenyl analogue was used to justify the rectification ability of DPDPh. The calculations showed that the insertion of nitrogen atoms in the conjugated backbone modifies the electronic structure of DPDPh compared to its parent hydrocarbon and then affects its electrical properties. Consequently, the HOMO level of DPDPh under positive voltage became closer to the Fermi level of the electrode than it does under negative bias giving rise to a rectifying character.