title: Cyanophenyl vs. pyridine substituent: impact on the adlayer structure and formation on HOPG and Au(111).
abstract: A new cyano substituted bis(terpyridine) derivative CN-BTP was synthesized and its adsorption on highly oriented pyrolytic graphite (HOPG) and Au(111) was investigated. CN-BTP is closely related to the previously investigated 2,4'-BTP, where the cyanophenyl groups are replaced by pyridine moieties. The scanning tunneling microscopy (STM) investigation of CN-BTP at the liquid|HOPG interface shows a highly ordered herringbone structure that is stabilized by double weak intermolecular C-HN hydrogen bonds, partially through the -CN substituents, which is different from the most stable square structure of 2,4'-BTP. The adsorption processes were investigated using cyclic voltammetry (CV) on Au(111) in a neutral phosphate buffer. A fast and full adlayer formation could be observed with CN-BTP, whereas an extremely slow process with 2,4'-BTP under the same conditions was found. Our data show that the CN substituents on BTP not only change the structure of the monolayer at the liquid|HOPG interface, but also accelerate the phase transition process in the electrolyte dramatically. This could be explained by the adlayer-substrate interactions, which is supported by DFT calculations. Our findings might be extended more generally to further pyridine comprising self-assembling molecules to fine-tune the adlayer structure and phase transition/adsorption kinetics by replacing pyridine by cyanophenyl moieties.
authors.affiliation: Institut für Organische Chemie III, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany. ulrich.ziener@uni-ulm.de.
authors.forename: Y
authors.initials: Y
authors.lastname: Dai
authors.forename: B
authors.initials: B
authors.lastname: Eggers
authors.forename: M
authors.initials: M
authors.lastname: Metzler
authors.forename: D
authors.initials: D
authors.lastname: Künzel
authors.forename: A
authors.initials: A
authors.lastname: Groß
authors.forename: T
authors.initials: T
authors.lastname: Jacob
authors.forename: U
authors.initials: U
authors.lastname: Ziener