Abstract: Theoretical investigations of conducting molecular wire of oligo-polyphenylene molecules under external electronic field were carried out using ab initio Hartree-Fock method with 6-31G* basis set. The electric field dependence of the molecular geometry, electronic structure, the spatial distribution, and the energy level of the frontier orbitals of the molecular wire was revealed. The torsion angle deviation was a function of square of electric field. When the external electric field increased, the torsion angles became smaller, the single bonds became shorter, and the molecular configuration tended to be more planar. All these features made the molecular wire more conjugated. The molecular electronic structure was sensitive to the electric field as well. With increasing electric field, the HOMO-LUMO gap decreased. Moreover, the spatial distribution of LUMO moved to the high potential end, whereas HOMO to the low potential end. Furthermore, the polyphenylene (PP) molecule with sulfur atoms bridged between two gold electrodes was studied by non-equilibrium Green's function formalism to further understand the electron transport of molecular wire under external electric field.

Key words:

Polyphenylene, Molecular wire, Molecular conformation, Molecular orbitals, Ab initio method