The synthesis, structures and magnetism of the complexes [FeII(3-bpp)2][bpmdcK](SeCN)1.7 (ClO4)1.3A?MeOHA?H2O (1), [FeII(3-bpp)2]4[bpmdcH2(H2O)2](ClO4)10A?7H2OA?3MeOH (2) and cis-[FeII 2(NCSe)2 ((3,5-Me2pz)3CH)2( -bpmdc)]A?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 hosta??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.