Xiaoshuai Fu+, Li Huang+,*, Linlu Wu+, Yubin Fu+, Xiao Chang, Xiaoxiao Pei, Chuqi Zhang, Chen Liu, Fupin Liu, Zhihai Cheng, Ji Ma, Xiao Lin, Wei Ji*, Xinliang Feng*, Hong-Jun Gao
Abstract:
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 synthesis of negatively charged metal atoms remains a significant challenge. Here, we report negatively-charged Ag dimer (Ag_2^(δ-)) arrays assembled on Ag(100) surface through coordination with a polycyclic aromatic hydrocarbon, 8,9-diaza-8a-borabenzo[fg]tetracene (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 non-contact atomic force microscopy, Kelvin probe force microscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. Neutral dimers Ag_2^0 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 (Ag_2^(δ-)). 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.
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