PHOTOSENSITIVE SELF-ASSEMBLED MONOLAYERS ON GOLD - PHOTOCHEMISTRY OF SURFACE-CONFINED ARYL AZIDE AND CYCLOPENTADIENYLMANGANESE TRICARBONYL

Photosensitive self-assembled monolayers (SAMs) are prepared by the sp ontaneous reaction of di-11-(4-azidobenzoate)-1-undecyl disulfide, I, or 11-mercaptoundecylcyclopentadienylmanganese tricarbonyl, II, with p olycrystalline Au. SAMs of I are photosensitive by virtue of a pendant aryl azide moiety (lambda(max) = 270 nm, log epsilon = 4.2) which und ergoes photoreaction with secondary amines to form Au-confined derivat ives of 3-H azepine and hydrazine, while Au-II SAMs undergo photosubst itution of phosphine for CO. Au-I SAMs irradiated in the presence of v arious secondary amines were characterized by reflection absorption in frared spectroscopy (RAIRS), XPS, and cyclic voltammetry, and showed p ersistent attachment of approximately one monolayer of amine. Infrared spectroscopy was used to establish that primary photoproducts obtaine d upon irradiation of Au-I SAMs in diethylamine are nearly identical t o primary photoproducts obtained upon irradiating an analog of I, meth yl 4-azidobenzoate, in diethylamine solution. XPS analysis of Au-I SAM s before and after irradiation in the presence of secondary amines con firms loss of Nz from the Au-I SAM and incorporation of one nitrogen a tom per surface-confined molecule. Most definitively, cyclic voltammet ry of Au-I after irradiation in the presence of 2-ferrocenylethyl-2',2 ',2'-trifluoroethylamine III, showed 3.3 X 10(-10) mol cm(-2) of surfa ce-confined ferrocene. Positive ion SIMS spectra of Au-II irradiated i n the presence of PPh(2)Et, PPh(2)(n-Pr), PPh(2)(CH2)(11)Fc, X, Fc = f errocenyl, or PPh(2)(CH2)2(CF2)(5)CF3, XI, show that introduction of t he phosphine onto the surface occurs upon near-UV irradiation. Importa ntly, the surface photochemistry of I and II allows the high lateral r esolution patterning of Au surfaces and Au microstructures with a vari ety of molecular reagents. SIMS maps for vinyl ferrocenium (m/z 212) o r F- (m/z 19) of flat Au-II substrates irradiated through a Cr-on-glas s mask in the presence of X or XI demonstrate photochemical patterning at a lateral resolution of <2 mu m. SEM confirms the resolution of 2 am features in the irradiated monolayer. Cyclic voltammetry and SIMS w ere used to demonstrate that Au microstructures derivatized with I can be patterned with molecular reagents, also at a lateral resolution of <2 mu m by UV irradiation through a mask and a thin film of the desir ed amine. A condensation figure was used to demonstrate photopatternin g of a flat Au-I substrate irradiated through a mask and a thin film o f (C2H5OH)(2)NH.