Effect of pressure and light on spin crossover and molecular magnetic interactions

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One the main goals of this proposal is the study of the cooperative interactions in newly synthesized iron(II) spin crossover complexes with triazole and tetrazole ligands and 1-D, 2-D, and 3-D lattice structures brought about by hydrogen bonding and/or p-p-stacking. For a quantitative interpretation, the so-called "Mainz model" of elastic interactions will be tested on metal-diluted mixed crystal series and under the influence of pressure. This model has been developed and successfully tested for mononuclear (i.e. zero-dimensional) iron(II) spin crossover compounds. LIESST effect studies will be performed in order to learn whether the relaxation kinetics correlates with the lattice dimensionality. - Another goal is the investigation of the effect of pressure on selected molecular systems with magnetic exchange interactions. One class to be studied are the Prussian Blue type compounds. Preliminary experiments show that applying pressure induces electron transfer before the spin state switching occurs. Another class of systems to be studied under pressure are di-, tri- and oligonuclear iron(II) compounds regarding the interplay of antiferromagnetic coupling and thermal and pressure-induced spin crossover. A method for direct monitoring the spin state in metal-pair formations will be employed.The results are expected to lend support for the existence of correlations and short range interactions.