Using Molecular Gears to Frustrate Ostwald: The Nanoscale Properties of Cruciform π-System Molecules on Metal Surfaces
Gina Florio, Department of Chemistry, St. John’s College of Liberal Arts and Sciences
Abstract
This study details a scanning tunneling microscopy investigation into the mechanism of chiral grain growth in highly-ordered, self-assembled monolayer films composed of cruciform π-system molecules. While the molecules themselves are achiral, when they adsorb from solution onto graphite they adopt a gear-like conformation that, by virtue of the surface, is chiral. These handed subunits spontaneously arrange into enantiomeric two-dimensional domains. The unique finding from this study is that Ostwald ripening is frustrated between domain boundaries that are of opposite chirality because the molecules are strongly physisorbed to the substrate and direct interconversion requires concerted motion of large blocks of molecules. These results will be discussed in the context of thin film growth for applications of relevance to molecular/organic electronic devices. Future studies will focus on deciphering the electronic properties of the cruciform π-system molecules when bound to metal surfaces or in metal-molecule-metal junctions.