Lattice-solvent controlled spin transitions in iron(II) complexes.

A series of spin transition (ST) iron(II) compounds of the type [FeII2](X)2.{S}2 (where is 4'-(4'''-cyanophenyl)-1,2':6'1''-bispyrazolylpyridine, X=ClO4- or BF4-, and S is acetonitrile) was synthesized and magnetically investigated. The effects of the removal of the lattice-solvent molecules and of their different positions relative to the iron(II) cations on the ST process were investigated.

Above room temperature spin transition in a metallo-supramolecular coordination oligomer/polymer.

By use of a metallo-supramolecular concept, a linear iron(ii) coordination chain [Fe(II)(L)](n)(BF(4))(2n) (L = 1,4-bis(1,2':6',1''-bispyrazolylpyridin-4'-yl)benzene) was rationally designed and synthesized. The molecular chain shows a reversible spin transition at 323 K with a ca. 10 K wide hysteresis loop.