cis- 2, 2’-bipyrimidine bridged polynuclear complex: a stairway-like mixed valent {Fe4} cluster

PABLO ALBORÉS; EVA RENTSCHLER

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2010 p. 8953 - 8961

0020-1669

We are reporting the first example of a polynuclear discrete coordination compound exhibiting only bpym bridges and containing a first row d transition metal.A smooth self-assembly one pot synthetic route, starting from simply FeCl2 and FeCl3 hydrates, allowed us to prepare a tetranuclear Fe4 cluster with a stairway-like structure and the formula cis-{[(H2O)ClFeIII-mu(bpym)FeIICl}2-mu(bpym). All spectroscopic data suggest that complex 1 is a valence-localized mixed valent Fe(II)-Fe(III) cluster with typical Mössbauer lines for both sites which do not change with temperature. Reflectance spectroscopy did not allow distinguishing an IVCT band. However TD-DFT calculations predict a weak high-energy Fe(II)--> Fe(III) transition. Regarding the magnetic properties, the high spin Fe(II) and Fe(III) ions interact in a weakly anti-ferromagnetic way with isotropic J constants of only a few wavenumbers as derived from DC susceptibility and magnetization data. Broken-symmetry DFT calculations support these observations.