Spin Manipulation of Single Nitroxide Radical on Au(111) by Selective Coordination

Organic radicals are promising candidates for constructing molecule-based magnetic materials. Despite the achievements of various radical ligand-containing complex materials, tuning the spin state of organic radicals at the single-molecule level on surfaces remains a challenge. In this study, the spin state of the DPBIN molecule, a derivative of 1,4-di(pyridine-3-yl)benzene bearing two imino-nitroxide radicals in para positions, is tuned by selective coordination with Au, Ni, and Fe centers on the Au(111) surface. The DPBIN molecules provide nitroxide oxygen atoms as ligand atoms in the Au and Fe coordination structures, where the spin of the DPBIN molecules is quenched. By contrast, the nitroxide oxygen atoms are not involved in coordination with Ni atoms; thus, the spin is preserved in this structure. Scanning tunneling microscopy (STM) and spectroscopy (STS) are employed to characterize the geometric structures and spin states of these coordination structures at the atomic level. Interestingly, this spin-manipulation method demonstrates a broader applicability to other metal coordination systems. This research deepens our understanding of the effect of selective coordination on radical spins.