Evidence for surface effects on the intermolecular interactions in Fe(ii) spin crossover coordination polymers

From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), it is evident that the spin state transition behavior of Fe(ii) spin crossover coordination polymer crystallites at the surface differs from the bulk. A comparison of four different coordination polymers reveals that the observed surface properties may differ from bulk for a variety of reasons. There are Fe(ii) spin crossover coordination polymers with either almost complete switching of the spin state at the surface or no switching at all. Oxidation, differences in surface packing, and changes in coordination could all contribute to making the surface very different from the bulk. Some Fe(ii) spin crossover coordination polymers may be sufficiently photoactive so that X-ray spectroscopies cannot discern the spin state transition.