The stepwise preparation of supramolecular structures offers the possibility to combine molecules, in a well-defined sequence, to fabricate molecular wires and molecular rectifiers for nanoelectronics applications.[1,2] However, the control of the growth process is needed, to ensure the formation of the intended structure. One of the most used techniques to control the molecular self-organization on a substrate is the scanning tunnelling microscopy (STM) at the liquid/solid interface.
We have been studying the preparation and characterisation of self-assembled molecular wires with zinc (II) octaethylporphyrin (ZnOEP) bridged by bipyridine (BP) on highly oriented pyrolitic graphite (HOPG).[3] We used STM at tetradecane/HOPG interface to control the ZnOEP adsorption and at the same time to obtain the corresponding I/V characteristics. The results showed that the molecular organization is independent of the MW length, aside defects whose presence increases with the number of growth steps.

References
[1] G. J. Ashwell, P. Wierzchowiec, L. J. Phillips, C. J. Collins, J. Gigon, B. J. Robinson, C. M. Finch, I. R. Grace,C. J. Lambert, P. D. Buckle, K. Ford, B. J. Wood, I. R. Gentle, Phys. Chem. Chem. Phys. 2008, 10, 1859–1866.
[2] S. H. Choi, B.-S. Kim, C. D. Frisbie, Science 2008, 320, 1482- 1486.
[3] Q. Ferreira, L. Alcácer, J. Morgado, “Stepwise Preparation and Characterization of Molecular Wires made of Zinc octaethylporphyrin complexes bridged by 4,4’-bipyridine on HOPG”, submitted for Nanotechnology.