Structural regulation of three Fe–Co cyanometallate complexes: reactant ratio issue.

Structural regulation of crystal structures to achieve specific structural architectures and/or desired functionalities is one of the main focuses in the field of molecular magnetism. The reaction of a trigonal tetradentate ligand, [TpFeIII(CN)3]− bridging unit and cobalt metal centres by the altering change of chemical stoichiometry afforded three different structures [{TpFe(CN)3}2Co(PyPz3)]·4MeOH·5H2O (1), [{TpFe(CN)3}Co(PyPz3)]2(ClO4)2·2MeCN·2H2O (2) and {(Tp)Fe(CN)3Co(PyPz3)}n(BF4)n·2nMeOH (3) (PyPz3 = 2-(di(1H-pyrazol-1-yl)methyl)-6-(1H-pyrazol-1-yl)pyridine and [TpFeIII(CN)3]− = tri(pyrazolyl)boratetricyanoiron(III)). Detailed structural studies reveal a gradual transformation among the complexes, from a trinuclear structure in 1, to a tetranuclear geometry in 2, and finally to a one-dimensional chain in 3. Magnetic susceptibility measurements revealed that all three complexes exhibit ferromagnetic interactions between the cyanide bridged FeIII and CoII centres, with exchange coupling constants of +7.89, +4.37, and +5.92 cm−1, respectively. Our result demonstrates an effective strategy for targeted assembly of architectures by introducing coordinatively unsaturated ligands, complemented by the cyanide-bridged linkers [TpRFeIII(CN)3]−. [ABSTRACT FROM AUTHOR]