Self-Stabilized Charge States in a Double-Decker Molecular Magnet on Pb(111)

Electron charging plays a key role in physicochemical processes, whose intrinsic stabilization in single molecules is desirable for tailoring molecular functionality and developing molecular devices, but remains elusive on surfaces. Here, we show that molecular charge states can be self-stabilized via intramolecular distortion in single bis(phthalocyaninato)terbium(III) (TbPc₂) double-decker molecules, which were grown on the Pb(111) substrate. Using scanning tunneling microscopy and spectroscopy, we identify fractions of TbPc₂ molecules that reduce to 2-fold symmetry, exhibiting energy-split molecular orbitals and two types of different spin states. Our first-principles calculations unveil that the symmetry reduction is induced by charging-triggered Jahn-Teller distortions, which lift the degenerate orbitals into two 2-fold symmetric orbitals. Single or double occupancy of the lower-energy orbital results in different molecular spin states. Such intramolecular distortion traps the excess electrons stably without explicit involvement of the substrate, in contrast to previously observed molecular charge states. These charged single molecules can be manipulated with the tip individually. This study offers a new avenue for tailoring the charge and spin states of molecules.