Influence of Substrate Electronic Properties on the Integrity and Functionality of an Adsorbed Fe(II) Spin-Crossover Compound

The bistability of spin-crossover complexes on surfaces is of great interest for potential applications. Using X-ray absorption spectroscopy, we investigated the properties of Fe(pypyr(CF3)2)2(phen) (pypyr = 2-(2′-pyridyl)pyrrolide, phen = 1,10-phenanthroline), a vacuum-evaporable Fe(II) complex, in direct contact to a set of substrates. The electronic properties of these substrates range from metallic to semiconducting. While dissociation is observed on metal surfaces, efficient light-induced switching is realized on semimetallic and semiconducting surfaces. This indicates that the density of states of the substrate at the Fermi level plays a role for the integrity and functionality of the adsorbed compound. In an intermediate case, namely, Fe(pypyr(CF3)2)2(phen) on graphene/Ni(111), functional and dissociated species are found to coexist. This result indicates that some previous studies may deserve to be reconsidered because the possibility of coexisting intact and fragmented spin-crossover complexes was neglected.