Structures and XPS studies of several 3d-4f cyano-bridged Ln^III-Fe^III/Co^III heterometallic complexes

Characterization and crystal structure determination of 3d-4f cyano-bridged bimetallic assemblies, Ln(DMF)₄(H₂O)₃Co(CN)₆ · H₂O (DMF = N,N′-dimethylformamide, Ln = Tb, Dy, Ho and Er) have been newly carried out. We have observed their isostructural features and gradual decreasing cell constants and corresponding changes of local bond distances and angles around the cyano-bridges in accord with the ionic radii changes due to lanthanoid contraction. In order to elucidate the reasons that only Nd-Fe and Nd-Co complexes can exhibit photo-induced magnetic functions, we have also investigated the electronic properties for several analogous 3d-4f complexes, Ln(DMF)₄(H₂O)₃M(CN)₆ · H₂O (Ln = Ce, Nd, Sm, Gd, Tb, Dy, Ho and Er; M = Co and Fe), by means of X-ray photoelectron spectroscopy (XPS). We found that the characteristic bent features of Nd-N-C bond angles and the slight shift of binding energies of Ln 4d_3/2 peaks in the 3d-4f systems being closed to mixed-valence states might be the reasons for the novel functions.