First-principles calculations of electron transport through azulene

Electron transport through azulene, a nonalternant hydrocarbon, has been investigated using nonequilibrium Green's function approach combined with density functional theory. I-V characteristics of azulene wired from different positions between two gold electrodes have been calculated. The results indicated that current strength correlates with orbitals amplitudes. Out of nine investigated azulene dithiolates, four molecular junctions (1,3-, 1,5-, 2,6-, and 4,7-connections) show high current compared with only one position from naphthalene dithiolate (1,4-). A current rectification ratio of ca. 4 was found in case of 2,7-azulene dithiolate. The remaining connections give low to moderate current. Aromaticity and ability of different connections to form quinonoid structure were used to explain electrical conductivity of the studied molecular junctions. The data were interpreted in terms of transmission spectra and molecular projected self-Hamiltonian eigenstates. Orbital symmetry rule and quantum interference have also been discussed.