Obvious variation of rectification behaviors induced by isomeric anchoring groups for dipyrimidinyl-diphenyl molecular junctions

The rectifying properties modulated by isomeric anchoring groups of dipyrimidinyl-diphenyl co-oligomer diodes sandwiched between two gold electrodes are investigated using density functional theory combined with the nonequilibrium Greenʼs function method. Our results show that the rectifying behaviors of the co-oligomer diode are significantly modulated by isomeric substitution of anchoring groups. When the isomeride nitrile end group is replaced by the isocyanide one, for symmetric arrangement of electrodes, the rectifying direction shows obvious inversion for the isocyanide-diblock-thiol junction, and the rectification ratio is obviously enhanced for the thiol-diblock-isocyanide junction. The influence on rectification induced by asymmetric electrodes is also discussed. The analysis of the transmission spectra and the molecular projected self-consistent Hamiltonian under various external bias voltages gives inside mechanisms of the observed results.