The charge states of metal adatoms on surfaces play a crucial role in controlling adsorption and interaction behaviors that underpin surface chemistry and catalysis, yet the atomically precise synthesis of negatively charged metal atoms remains a significant challenge. Here, we report negatively charged Ag dimer (Ag2δ−) arrays assembled on Ag(100) surface through coordination with a polycyclic aromatic hydrocarbon, 8,9-diaza-8a-borabenzofgtetracene (DBT), featuring a doping moiety with N–B–N bonds at zigzag edge. The Ag dimers are stabilized by two DBT monomers through N–Ag–N coordination bonding. In contrast to surface Ag atoms, the coordinated dimers display anionic character, as demonstrated by noncontact atomic force microscopy, Kelvin probe force microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. Neutral dimers Ag20 can be converted from the coordinated complex by tip-induced detachment of one DBT monomer and showed markedly higher affinity for CO adsorption, a process that is suppressed on Ag2δ−. These findings establish an atomically defined platform for stabilizing and controlling anionic metal centers on metallic surfaces, providing a model system for exploring charge-state effects in surface chemistry.
Fu et al. (Thu,) studied this question.