Self-Assembled Monolayers of a Bis(pyrazol-1-yl)pyridine-Substituted Thiol on Au(111)

Self-assembled monolayers (SAMs) of a bis(pyrazol-1-yl)pyridine-substituted thiol (bpp-SH) on Au (111)/mica were studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Using substrates precoated with perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA), preparation at elevated temperatures yields highly ordered layers whose structure is described by a rectangular (5 x root 3) unit cell containing one molecule. The bis(pyrazol-1-yl)pyridine (bpp) units exhibit pi-stacking along the < 11 (2) over bar > direction, and they are tilted significantly. We conclude the three imine nitrogen atoms in the bpp headgroup adopt a trans,trans arrangement.