Preserving the spin transition properties of iron-triazole coordination polymers within silica-based nanocomposites

One dimensional iron(II) coordination polymers formed from 1,2,4-triazole bridging ligands are a unique class of spin-crossover materials (SCO). The integration of those coordination polymers into devices for practical applications remains a major challenge. Using a nanocomposite approach based on the control of coordination polymer interactions with chemically engineered silica particles, we show that we can achieve in situ gelation, while preserving the SCO properties of the solid state. Tuning the interface between the two phases of a composite provides a unique way to synergistically adjust the material's structure and the cooperativity associated with its transition properties. The strategy described here should allow for bridging the gap between soft and crystalline functional inorganic materials.