Molecules offer exceptional capabilities for the design of organic electronic components, as well as integrated elements of CMOS based technologies, due to the ability to readily tune their electronic states through designed synthetic modifications. Among the many challenges in implementing molecular/organic electronic devices, perhaps the most significant is understanding the correlation between chemical structure and the resulting conductive characteristics of a molecule assembled on a surface. Recently we have explored how nearest-neighbor interactions can be used to afford charge delocalization in supramolecular assemblies to shift transport out of the tunneling regime into the more chemically tunable charge-hopping regime. Here, the transport properties of a series of free-base and zinc coordinated tri-pyridyl and tri-phenyl porphyrin thiols inserted into a dodecanethiol matrix on Au(111) were studied using scanning tunneling microscopy (STM). For single molecules, the tunneling efficiency and I-V behavior was found to be dominated by through bond tunneling. However, when these same molecules were driven to assemble into islands of ~ 10 nm in dimension (e.g. through pi-stacking), distinct changes in their charge transport properties were observed, whereby a reduction in the charge confinement energy facilitated the transition from a purely tunneling mechanism to a charge-hopping mechanism. Directing such assemblies into pre-designed architectures however, still represents a significant challenge, and to address this we have explored the use of click-chemistry have been employed to enable the construction of better controlled supramolecular structures. The fabrication and assembly process, and is impact on the electronic properties of the materials will be discussed.

Tuning charge transport in supramolecular assemblies of porphyrins on Au

253rd National Meeting (2017)

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