Scanning Tunneling Microscopy of 8-Fluoroindolo[2,1-b]quinazolin-6,12-dione (8-Fluorotryptanthrin) at the Graphite-Solution Interface: Fully Resolved Molecular Orbitals

摘要

Scanning tunneling microscopy was used to observe 8-fluorotryptanthrin, an analogue of indolo[2,1-b]quinazolin-6,12-dione (tryptanthrin). Images were collected of molecules adsorbed at the solution—HOPG (highly oriented pyrolytic graphite) interface, displaying submolecular resolution. Measurements at negative bias are provided where individual molecular orbital lobes were observed, correlating directly to the density functional theory model of the highest occupied molecular orbital (HOMO). Molecules measured approximately 1.3 nm in length. Separate surface domains, displaying an offset of approximately 0.36 nm, were observed from parallel rows of molecules. Two-dimensional enantiomers were observed occupying the domain boundary. Raised features observed in the image suggest that molecules of 8-fluorotryptanthrin experience adsorption-induced stereoisomerization, similar to its parent compound.