Three-State Switching of an Fe Spin Crossover Complex
Sven Johannsen, Sascha Schüddekopf, Sascha Ossinger, Jan Grunwald, Felix Tuczek, Manuel Gruber, Richard Berndt
Abstract
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.