Chemical Reactions and Adsorption Geometries of Pyrrole on Ge(100)

Abstract

The adsorption structures of pyrrole (C(4)H(5)N) on a Ge(100) surface at various coverages have been investigated with both scanning tunneling microscopy (STM) and ab initio density-functional theory (DFT) calculations. Three distinct features are observed in the STM images at low coverages. The comparison of the STM images with the simulation reveals that the most dominant flowerlike feature with a dark side is that the adsorbed pyrrole molecules with H dissociated form bridges between two down Ge atoms of neighboring Ge dimer rows through N-Ge bonding and beta-carbon-Ge interaction. The flowerlike feature without a dark side is also observed as a minority, which is identified as nearly the same structure as the most dominant one where a dissociated H is out of the feature. The third feature showing bright protrusions may be due to a C- and N-end-on (CN) configuration, where the pyrrole molecule is located on one dimer row. At higher coverages, the number of localized configurations increases.

Effect of polar organic vapors on surface potential of Au nanoparticle aggregates probed by surface-enhanced Raman scattering of 2,6-dimethylphenylisocyanide

“…1a are due to the NC stretching and C-NC stretching vibration, respectively. 11 Ring associated bands are comparatively less intense than the NC associated bands, as can be evidenced from the peaks at 3046, 1593 and 995 cm À1 that can be assigned to the CH stretching, the ring CC stretching (n 8a ), and the in-plane ring breathing (n 12 ) modes of 2,6-DMPI, respectively. Fig.…”

“…The substantial blue-shift of the NC stretching mode can be understood by invoking the fact that the carbon lonepair electrons in the isocyanide group have an antibonding character. 11 The donation of these electrons to gold should increase the strength of the NC bond. The substantial band broadening is associated with the vibrational energy relaxation channel provided by the direct contact of the NC group with the gold substrate.…”

Surface characteristics of Ag‐doped Au nanoparticles probed by Raman scattering spectroscopy

“…This indicates that 2,6-DMPI should adsorb not only on Au but also on Ag via the isocyanide group. [28,43] A close examination of the N-C stretching peaks in Figs 3(a) and (b) reveals that the peak position is subtly dependent on the amount of Ag contained in the nanoparticle films. To clarify this point, in Fig 3(c), the N-C stretching peak positions are collectively plotted as a function of the mole fraction of Ag contained in the Au 1−x Ag x and Au 1−x @Ag x nanoparticles.…”

“…The ring-associated bands are barely disturbed after the adsorption of 2,6-DMPI on metallic substrates. [28,43] For example, the ring C-C stretching (ν 8a ) band appears at 1593 cm −1 in the NR spectrum but at ∼1590 cm −1 in all the SERS spectra. However, a considerable peakshift occurs for the N-C stretching mode.…”

Density Functional Theory Calculations of the Adsorption of Cytosine on Si(100)

“…Such interactions may occur between silicon atoms and the atoms of the cytosine ring or among adsorbed cytosine molecules. Interaction can involve a single dimer or may span multiple dimer rows when the cytosine ring is located between two nearby dimer rows, similarly to the interactions observed for pyrrole 19 and pyridine 10 adsorbed on Ge(100). The aromaticity of the cytosine ring, which contains two conjugated double bonds and an unshared electron pair with six π electrons, can also affect the reaction process and the thermodynamic stability of the adsorption products.…”