Single Ni Atoms Drive Carboxyl Deprotonation in Metal-Organic Chains

Understanding how charge transfer and ligand activation processes govern metal-organic coordination at surfaces is crucial for controlling on-surface synthesis and the formation of low-dimensional architectures. Here, we show that Ni promotes the deprotonation of the carboxyl groups of terephthalic acid (TPA) on Ag(100), leading to the formation of linear metal-organic coordination chains. Scanning tunneling microscopy reveals that these chains emerge from preassembled hydrogen-bonded TPA stripes. X-ray photoelectron spectroscopy identifies stabilization of the Ni centers in the Ni(I) oxidation state through a single-electron charge transfer process, accompanied by the formation of deprotonated carboxylate species. Valence band spectroscopy reveals a coordination-induced electronic reorganization between Ni and TPA through the emergence of hybrid states, in agreement with complementary theoretical modeling. Together, these findings identify charge-transfer-driven deprotonation as the central mechanism governing the formation of linear metal-organic chains.