Spectroscopic characterization of the bonding, orientation, and coverage of copper tetraazaphthalocyanine monolayer films on SiO2 surfaces

Self-assembled monolayer films of a metallotetraazaphthalocyanine were prep ared using two different reaction conditions. The films were characterized by ellipsometry, AFM, electronic absorption spectroscopy, semiempirical MO calculations, core-level XPS, and projection of a calculated structure of t he chromophore onto a surface to obtain its silhouette area for comparison with surface concentration from absorption spectroscopy. A denser packing o f the chromophores is found in the SAM film prepared with bromonaphthalene at 250 degreesC as compared with the film from the more polar solvent DMF a t 120 degreesC. Data is consistent with an almost vertical orientation of t he chromophores in the former film. A different number of bonds connecting the chromophore with the coupling molecule is suggested as an explanation t o differences in the absorption bands for the two films.