Self-assembled diisocyanide monolayer films on gold and palladium

Self-assembled monolayers (SAMs) of the aromatic diisocyanides, 1,4-phenylenediisocyanide, 2,3,5,6-tetramethyl-1,4-phenylenediisocyanide, 4,4′-biphenyldiisocyanide, 3,3′,5,5′-tetramethyl-4,4′- biphenyldi-isocyanide, and 4,4″-p-terphenyldiisocyanide, were prepared on gold and palladium surfaces. The SAMs were characterized by ellipsometry, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and grazing-angle attenuated total reflectance infrared spectroscopy (GATE). Based on the position of the metal-coordinated isocyanide stretching band, the SAMs on gold were found to bind in the terminal (η 1) geometry, while the SAMs on palladium prefer a different geometry which is possibly a triply bridging (μ 3-η 1) geometry. A side-reaction of the unbound isocyanide in the SAM was identified as oxidation to an isocyanate group. © 2005 American Chemical Society.