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'-bi-
phenyldiisocyanide, 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 (GATR). Based on the position of the metal-coordinated isocyanide stretching band, the SAMs on gold were found to bind in the terminal geometry, while the SAMs on palladium prefer a different geometry which is possibly a triply bridging geometry.Aside-reaction of the unbound isocyanide in theSAMwas identified as oxidation to an isocyanate group.