Orbital Views of the Electron Transport through Polycyclic Aromatic Hydrocarbons with Different Molecular Sizes and Edge Type Structures

In this work electron-transport properties of π-conjugated polycyclic aromatic hydrocarbons with different molecular sizes and edge type structures are investigated. The applicability of a derived concept for orbital control of electron transport (J. Am. Chem. Soc.2008, 130, 9406) is tested on larger hydrocarbons in order to estimate its predictive power for different types of compounds. Favorable connections for effective electron transport in π-conjugated systems with weak coupling between the molecules and electrodes are predicted on the basis of the orbital symmetry rule by looking at the phase and amplitude of the frontier orbitals. Qualitative predictions based on frontier orbital analysis are compared with density functional theory calculations for realistic molecular junctions with strong covalent bonds between a molecule and two gold electrodes. Obtained results are in good agreement with the orbital symmetry rule predictions, which makes the frontier orbitals’ analysis a powerful tool in electron transport studies in π-conjugated polycyclic aromatic hydrocarbons.