Spin-Modulated O₂ Adsorption on Surface-Constructed Metal-Organic Chains

O₂ adsorption is pivotal in O₂-involved catalytic processes, where catalysts' spin properties play crucial roles, yet the microscopic mechanisms remain elusive. Here, scanning tunneling microscopy/spectroscopy and atomic force microscopy characterizations enable direct comparison of O₂ affinity between the high-spin (Ni^H) and low-spin (Ni^L) Ni centers alternately embedded in the coordination chains on Au(111) at the atomic scale, revealing preferred O₂ adsorption at Ni^H. Density functional theory studies demonstrate that this selectivity arises from the distinct d-electron configurations of Ni^H and Ni^L, which significantly affect the O₂-Ni hybridization. The stronger O₂ adsorption at Ni^H than at Ni^L drives a spin transition of Ni^L upon O₂ adsorption, which could be kinetically unfavorable and thus further contribute to the observed selective O₂-Ni^H binding. These findings offer microscopic insights into the spin-modulated O₂ adsorption.