Self-assembled monolayers on gold of thiols incorporating conjugated terminal groups

Thiols 3, 6, and 14 incorporating omega-attached conjugated aromatic groups form self-assembled monolayers (SAMs) on polycrystalline gold. The thickne sses of the films as measured by optical ellipsometry correspond well to th e expected thickness of monolayer films in which the components are oriente d roughly perpendicular to the Au surface. Cyclic voltammetry measurements of K4Fe(CN)(6) in aqueous KCl solution on a SAM modified gold electrode sho w that these monolayers are densely packed and attenuate electron transfer between the gold and the solution electrophore. Glazing angle reflectance-F ourier transform infrared spectroscopy (GAR-FTIR) shows that the conjugated arenes of 3, 6, and 14, as well as the Cg chains of thiols 6 and 14, are r oughly perpendicular to the plane of the Au surface. Fluorescence spectrosc opy indicates that the terminal arenes in SAMs of 6 and of 11 interact, cau sing red-shifted, structured emission in the SAM relative to that observed for the same species in dilute homogeneous solution.