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)(mu-bpm)] {Ln = Nd or Eu; RR' = dimethyl- (Me-2) 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 kappa N-2(1,1') : kappa N-2(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 beta-diketonato analogues, suggesting the coordination environment around the Ln(III) center influences the electronic structure and spectroscopic symmetry of the complexes in solution.