Synthesis, structure and magnetic properties of oligonuclear polycyanometalates, encapsulated with transition metal bispidine complexes

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A series of mono-, bis- and tris-macrocyclic ligands, coordinated to copper(II) or nickel(II) have been prepared in metal-ion-directed template reactions. The tricopper(II) and trinickel(II) complexes, obtainable by simple reactions but in relatively low yield, exist primarily in two probably nearly degenerate conformations with low activation barriers for their interconversion. In their hemispherical syn,syn conformation two of the trinuclear complexes may combine to a capsule which has been shown to be an ideal host for corner-shared bis-octahedral complexes. The so far unknown [(CN)5Fe(CN)Fe(CN)5]7- anion has been assembled in presence of, and stabilized inside the cavity of the hexakis-copper(II) complex, based on two of the tris-macrocyclic ligand copper(II) cations; this Cu6Fe2 cluster is stable in solution and has been structurally analyzed. The project involves the synthesis of a variety of similar oligo-macrocycle-based host molecules, the preparation and characterization of a range of host-guest assemblies, primarily based on dinuclear cyano complexes, the investigation of the solution structures of the host complexes by molecular modeling and NMR (nickel(II)) or EPR spectroscopy (copper(II)), and the investigation of the magnetic properties of the stable host-guest complexes.