Electronic Structure and Adsorption Stability of Ferrocene on Au (111) and Ag (111) Surfaces

The adsorption behavior and electronic structure of ferrocene (Fc) on Au(111) and Ag(111) surfaces were investigated using density functional theory (DFT). Two Fc conformers, eclipsed (E-Fc) and staggered (S-Fc), were studied in vertical (⏊) and parallel (||) orientations at three adsorption sites—top (T), hollow (H), and bridge (B). Fc preferentially adsorbs in a vertical configuration through the lower Cp ring on hollow sites, with adsorption energies of -0.87 eV (E-Fc) and -0.88 eV (S-Fc) on Au(111) and -0.79 eV for both conformers on Ag(111). These results confirm that Fc adsorptions are more stable on Au(111) than Ag(111), with negligible stability differences between the two conformers in vertical configurations. Parallel configurations are generally less stable; S-Fc cannot stably adsorb parallel on either surface, and E-Fc(||) exhibits significantly weaker adsorption energies (-0.82 eV on Au(111) and -0.62 eV on Ag(111)) than vertical configurations. Electronic structure analysis reveals that Fc acts predominantly as an electron donor on both metal surfaces. A distinctive region-specific charge transfer is observed in vertical configurations, where electrons flow from top-layer Au atoms to the Cp ring of Fc, forming an electron circuit that enhances adsorption strength. This feature is absent in parallel configurations, where charge transfer occurs uniformly from Fc to the surface, resulting in weaker adsorption. These findings underscore the impact of adsorption geometry and surface type on Fc’s stability and electronic interactions, offering valuable insights into its behavior on metallic surfaces. While results for Fc/Ag(111) are included in supplementary materials, the primary focus is on Fc/Au(111). This study provides a basis for exploring Fc-surface interactions in applications such as corrosion inhibition and catalysis.