Control of the Molecular Function through a Decoupling Unit

Our article is available to read at J. Phys. Chem. C.

In the present work, two viologen derivatives were synthesized and used in molecular junctions (MJs) to investigate the impact of a decoupling unit on the rectification behavior. Both bear an aniline terminal unit but one of the viologen derivative (named VIO-C₁) is terminated by a methyl group whereas the other (named VIO-C₆) bears a six-carbon (C₆H₁₃) terminal chain. Thin layers of each derivative were deposited on gold microelectrodes by the electroreduction of the corresponding diazonium reagents, and solid-state MJs were fabricated to study the electronic transport. JV curves of VIO-C₁ show a symmetric behavior, whereas the VIO-C₆ (with alkyl chain) JV curves show strong asymmetry in the transport. This behavior is attributed to the decrease of the electronic coupling at the top interface due to the alkyl chain and is confirmed by comparison with similar VIO-C₁ MJs in which a thin AlO_x layer is inserted on top of the VIO-C₁ layer. The impact of this decoupling unit on the rectification ratio is discussed.