The 2D structures of a variety of n-alkyl-substituted perylene diimides adsorbed onto HOPG and MoS2 surfaces from phenyloctane solutions were studied using scanning tunneling microscopy (STM). Both rectangular, or herringbone-like, structures and row structures were observed. Surprisingly, the lattice constants, and thus the area per molecule of the rectangular structures, did not increase as expected when the alkyl chain length was increased. Protrusion of the alkyl tails into the solvent above the 2D layer is proposed to account for this behavior. Row structures, where the alkyl tails lie flat on the substrate surface, were also observed wherein the area per molecule increases as expected for the increase in the length of the alkyl tail. The formation of domains with a particular orientation with respect to the underlying lattice was observed for many of the 2D structures. The alignment of the molecular layers with the substrate could be explained with a point-on-line coincidence model. Formation and filling of missing molecule defects within the oriented domains was observed during continuous scanning of the STM.

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The HAM/3 method was used to provide a better assignment of the valence X-ray photoelectron spectra of 16 polymers involving nitrogen, oxygen, fluorine, a glucose unit, and a benzene nucleus using the monomer, dimer or trimer model molecules without consideration of the contraction factor of the energy scale. The calculated Al Kα photoelectron spectra were obtained using Gaussian functions of a fixed approximate linewidth, 0.10 Ik and Ik = I′k − WD, where I′k is the vertical ionization potential of each MO and WD is an approximate shift to account for the work function of the sample and other energy (polarization energy and so on) effects. We assumed that WD corresponds to the shift that we must apply before we can compare the calculated spectrum for the single model molecule with the observed spectrum for the solid. The approximate linewidth corresponds to the experimental result that the inner valence spectra are broader. The theoretical spectra showed good agreement with the spectra of the polymers observed between 0—40 eV.