Three-State Switching of an Fe Spin Crossover Complex

• Published in: Journal of physical chemistry. C Vol. 126; no. 16; pp. 7238 - 7244
• Main Authors: Johannsen, Sven, Schüddekopf, Sascha, Ossinger, Sascha, Grunwald, Jan, Tuczek, Felix, Gruber, Manuel, Berndt, Richard
• Format: Journal Article
• Language: English
• Published: American Chemical Society 28.04.2022
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.2c00473

Isolated tetramers of the spin crossover compound Fe­(H2B­(pyrazole)­(pyridylpyrazole))2 were investigated on Ag(111) at cryogenic temperature (5 K) with a scanning tunneling microscope (STM) in ultrahigh vacuum. In addition to spin states obtained by electron-induced spin crossover, a third state of the complexes is discovered with different current–voltage characteristics and intramolecular image contrast. It is stable over a limited range of voltages beyond which it decays into the low- and high-spin states of the Fe complex. The state may be prepared in a deterministic manner that enables measurements of its decay dynamics at various currents and voltages. We interpret this state as being due to a negatively charged Fe complex in its high-spin state, which is isoelectronic to the analogous Co compound.