Adsorption Configuration Change of Pyridine on Ge(100): Dependence on Exposure Amount

Abstract

The variations of adsorption configurations of pyridine on Ge(100) as a function of exposure amount have been studied using high-resolution photoelectron spectroscopy (HRPES). At low exposure the C 1s and N 1s core levels show a single adsorption state of pyridine with N 1s binding energy at 400.85 eV and C 1s binding energies at 286.7 and 285.9 eV, respectively. Those are attributable to Ge-N dative bonding of pyridine through the lone pair electrons of its N atom, which is consistent with previous STM and theoretical studies. As the molecular exposure increases the N 1s core level reveals not only the dative-bonding state of pyridine but also the appearance of a new chemical state at 398.80 eV, corresponding to the sigma bonding of Ge-N. Such a change of adsorption configuration agrees well with new C 1s features at the low binding energy side, which accounts for the evolution of cycloaddition products with Ge-C bonds. Consequently, di-sigma-bonded cycloadducts coexist with Ge-N dative-bonding products for the final configuration with high density of pyridine on the Ge(100).

Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

“…We expect these bondings to be formed from the metastable dative bonded adsorption state before the dative bonded molecules undergo N-H dissociation. This conclusion agrees well to recently published observations by Bae et al 41 who investigated pyridine molecules adsorbed on Ge(100) surfaces and found a dative N-Ge bonding which is followed by C-Ge bondings.…”

“…Those molecules that do not experience N-H dissociation can additionally form covalent bonds from the C atoms to the As and/or Ga atoms to the surface as similarly reported by Bae et al for the adsorption of pyridine on the Ge(100)-(2 × 1) surface. 41 As described above, the GaAs surface reconstructions differ in terms of the occupation of the respective dangling bonds as a consequence of their different stoichiometries. At the As-rich phase, the GaAs(001) surface provides only filled dangling bonds which are to be regarded as nucleophilic sites.…”

Thermodynamic factors limiting the preservation of aromaticity of adsorbed organic compounds on Si(100): Example of the pyridine

“…11 Dative-bonded adducts are frequently observed only at low gas exposure and at low temperatures. It is generally believed that the adsorption occurs in a first step through a dative bond followed by the apparition of other structures 8,10,12,13 leading to the vanishing of dative bonds. It is not clear if this transformation is due to a thermodynamic constraint or to a kinetic mechanism.…”

The Active Center of Co–N–C Electrocatalysts for the Selective Reduction of CO2 to CO Using a Nafion-H Electrolyte in the Gas Phase

“…As similar structures to a Co–N center, N1s binding energies of Ge–N coordination by pyridine and protonated pyridine were reported to be 400.85 and 401.2 eV, respectively. 37 , 40 The previous reports suggested that the coordination of other elements to pyridine resulted in the positive shift of N1s binding energy to compare with a 398.9 eV of pyridine, which suggested the assignment of the 400.3 eV peak to Co–N bonds.…”