Supramolecular aspects of iron(II) crown-dipyridyl spin-crossover compounds

The synthesis, structures and magnetism of the complexes [FeII(3-bpp)2][bpmdcK](SeCN)1.7(ClO4)1.3·MeOH·H2O (1), [FeII(3-bpp)2]4[bpmdcH2(H2O)2](ClO4)10·7H2O·3MeOH (2) and cis-[FeII2(NCSe)2((3,5-Me2pz)3CH)2(μ-bpmdc)]·2MeCN (3) (where 3-bpp = 2,6-di(pyrazole-3yl)pyridine, bpmdc = N,N′-bis(4-pyridyl-methyl)diaza-18-crown-6) and (3,5-Me2pz)3CH = tris(3,5-dimethylpyrazole)methane, are presented. These compounds form a study of the supramolecular influence of host–guest/crown-ether interactions and cation-to-crown hydrogen-bonding effects upon d6 spin transitions, the latter occurring above, or near to, room temperature in 1 and 2. Desolvation effects also influence the T1/2 values. The dinuclear compound 3 contains covalent pyridyl (crown) N to Fe bridge bonding and remains high spin.

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► Iron(II) spin crossover compounds with functionalised crowns as bridges.
► Supramolecular aspects of crown bridging, including a potassium cation guest.
► Structure-magnetism correlations including solvate loss affecting spin transitions.