Highly ordered self-assembled architectures of modified terpyridines on highly ordered pyrolitic graphite imaged by scanning tunneling microscopy

Scanning tunneling microscopy has been used to study the adsorbed phases of functionalized terpyridines at the solid-liquid interface of highly ordered pyrolitic graphite (HOPG). Terpyridines are well-known for their complexing behavior to transition metal ions, making them widely used ligands in organometallic and supramolecular chemistry. We found that solutions of 2,2:6,2-terpyridine-4-oxydodecane (tpy-O-C12) and 2,2:6,2-4-oxyoctadecane (tpy-O-C18) form highly ordered two- dimensional (2D) arrays on HOPG in phenyloctane. For both compounds, large, well-defined lamellar domains have been observed with domain sizes larger than 500 nm. Sequential scans of an area with two grain boundaries indicate that desorption-resorption is taking place along the domain edges. High-resolution images of the lamella have been obtained, and the 2D packing within the lamella was determined in detail. The terpyridines align in long uniform double rows with their alkyl chains packing in an alternating, zipper-like fashion. The terpyridines pack with the polar head-groups head to head, and the observed size and shape of the molecules fit exactly to their modeled geometries.