The ordering of small molecules, programmed with functional groups for specific non-covalent interactions, can lead to robust, dynamic, and functional monolayers or thin films. Our group studies these assemblies under well-controlled environments by atomic-resolution scanning tunneling microscopy (structural characterization) and X-ray photoelectron spectroscopy (chemical characterization). These studies allow new insights in the roles of electrostatic, transition metal coordination, and van der Waals interactions in two-dimensional assembly, as well as in the formation of crystalline organic thin films. Three new results will be highlighted in this presentation to illustrate these ideas around the theme of designing the molecular building blocks for efficient self-assembly into well-defined systems with potentially transformative electronic or chemical function. Recent results from our lab demonstrate the on-surface redox assembly of platinum with a dipyridyl tetrazine ligand on a single crystal gold surface into 1D chains of interest for the single site Pt(II) centers as catalyst sites. We have designed molecules with intramolecular charge separation for parallel, offset stacking to produce crystalline organic films. We have also demonstrated triggered switching of surface architectures in a dynamic solution-solid interface environment. These studies open new opportunities in designing organic materials for organic semiconductors, sensors, catalysts and photovoltaics.
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