Improved Cooperativity Of Spin-labile Iron(iii) Centers By Self-assembly Inrnsolution

摘要

We report on the markedly increased spin crossover activity of materials when self-assembled in solution. Spin crossover is directly related to long-range elastic interactions, typically observed in the solid state, and the transition may be gradual over a large temperature range. Effects such as solvent cocrystallization often modify the transition in an unpredictable way. This is predominantly because spin transitions are crucially affected by intermolecular interactions beyond crystal packing effects, such as elastic strain. Such intermolecular interactions are the classical domain to be engineered by supramolecular chemistry. Specifically, the promotion of close metal-metal interactions may stimulate cooperative behavior, which is expected to result in more abrupt spin transitions. This concept has been implemented for engineering of spin crossover active materials in the solid state and recently also in soluble nanoparticles. Here, we have used a hydrophilicAipophilic bias6 for inducing a favorable arrangement of potentially spin-labile iron(III) centers. Supramolecular organization in solution leads, most remarkably, to a new type of magnetically active material for liquid-phase processing.