Homodinuclear lanthanoid(III) dithiocarbamato complexes bridged by 2,2′-bipyrimidine: Syntheses, structures and spectroscopic properties

Four new homodinuclear lanthanoid(III) dithiocarbamato (RR′dtc⁻) complexes bridged by 2,2′-bipyrimidine (bpm) of the form [{Ln(RR′dtc)₃}₂(µ-bpm)] {Ln = Nd or Eu; RR′ = dimethyl- (Me₂) or pyrrolidine- (pyr)} were prepared and their crystal structures and spectroscopic properties were characterized. The crystallographic studies revealed that all of the complexes possess a similar structural motif with an 8:8-coordination geometry, in which the bpm ligand bridges two Ln^III centers in the κ²N^1,1′:κ²N^3,3′ mode and three RR′dtc⁻ ligands coordinate to each Ln^III center. The complexes exhibit weak but relatively sharp f–f transition bands in the absorption and magnetic circular dichroism (MCD) spectra recorded in the visible region. The MCD spectral studies demonstrated the magneto-optical behavior of the complexes. The spectral features of the dithiocarbamato complexes were distinctly different from those of their β-diketonato analogues, suggesting the coordination environment around the Ln^III center influences the electronic structure and spectroscopic symmetry of the complexes in solution.