Design of nanoscale molecular wire based on 3, 6-Diphenyl-1, 2, 4, 5-Tetrazine and effect of external electric field on electron transfer in conjugated molecular wire

The electron transport characteristics of a 3, 6-Diphenyl-1, 2, 4, 5-Tetrazine (DPT) single molecular conductor are investigated via the density functional theory (DFT) method. The molecule sandwiched between two gold surfaces. Different linkers such as sulfur, nitrogen, oxygen, CS, CO, CN, NO and NN have been considered to study the role of linkage in the conduction properties of the molecular wire. The charge transfer across the metal–molecule and bonding nature at the interfacial contact were performed by means of the natural bond orbital (NBO) analysis. It is found that Au can covalently bond to DPT through nitrogen or sulfur linkages while its weak interaction through oxygen linkage has non-covalent character in nature. The dependence of the molecular electronic structure of the gold–molecule complexes on the external electric field (EF) has also been studied. It is found that the external EF modifies both the geometry and electronic structure of the molecular wires. The application of EF may increase the molecular conjugation and the induced dipole moment, while decreasing the HOMO–LUMO gap. It may also make the spatial distributions of the frontier molecular orbital's move from a fully delocalized form to a partially localized one depending on the EF strength.

Graphical abstractThe electron transport characteristics of a 3, 6-Diphenyl-1, 2, 4, 5-Tetrazine (DPT) single molecular conductor are investigated via the density functional theory (DFT) method.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The 3, 6-Diphenyl-1, 2, 4, 5-Tetrazine (DPT), acts as good “wire” for electron and charge transfer. ► Full geometry optimization, Au3–DPT–Au3 (M–L–DPT–L–M) complex is carried out within DFT, using the Gaussian 03 package. ► We compared the energies of HOMO, LUMO and the HOMO–LUMO gap levels for DPT with eight different linkages. ► The shift of HOMO and LUMO can be attributed to the variation of the electron density when the gold clusters and the molecule bond. ► The reported orbital energies show that when the gold cluster and the DPTs bond, the resulting complexes have lower HLG than the isolated DPTs.