title: Atomic-Resolution Kinked Structure of an Alkylporphyrin on Highly Ordered Pyrolytic Graphite.
abstract: The atomic structure of the chains of an alkyl porphyrin (5,10,15,20-tetranonadecylporphyrin) self-assembled monolayer (SAM) at the solid/liquid interface of highly ordered pyrolytic graphite (HOPG) and 1-phenyloctane is resolved using calibrated scanning tunneling microscopy (STM), density functional theory (DFT) image simulations, and ONIOM-based geometry optimizations. While atomic structures are often readily determined for porphyrin SAMs, the determination of the structure of alkyl-chain connections has not previously been possible. A graphical calibration procedure is introduced, allowing accurate observation of SAM lattice parameters, and, of the many possible atomic structures modeled, only the lowest-energy structure obtained was found to predict the observed lattice parameters and image topography. Hydrogen atoms are shown to provide the conduit for the tunneling current through the alkyl chains.
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Yiing
authors: Y
authors: Chin
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Dwi
authors: D
authors: Panduwinata
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Maxine
authors: M
authors: Sintic
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Tze Jing
authors: TJ
authors: Sum
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.|‡School of Biomolecular Sciences, The University of Sydney, NSW 2006, Australia.
authors: Noel S
authors: NS
authors: Hush
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Maxwell J
authors: MJ
authors: Crossley
authors: †School of Chemistry, The University of Sydney, NSW 2006, Australia.
authors: Jeffrey R
authors: JR
authors: Reimers
keywords: STM image simulation; atomic structure; density-functional theory; highly ordered pyrolytic graphite; internal calibration; scanning tunneling microscopy