Pergamon-Elsevier Science Acta Medica Okayama 0277-5387 171 2019 Homodinuclear lanthanoid(III) dithiocarbamato complexes bridged by 2,2′-bipyrimidine: Syntheses, structures and spectroscopic properties 515 522 EN Abdallah Yakubu Graduate School of Natural Science and Technology, Okayama University Takayoshi Suzuki Research Institute for Interdisciplinary Science, Okayama University Masakazu Kita Faculty of Education, Okayama University 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. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 00201693 498 2019 Dinuclear lanthanoid(III) dithiocarbamato complexes bridged by (E)-N-benzylidenepicolinohydrazonate: Syntheses, crystal structures and spectroscopic properties 119124 EN Abdallah Yakubu Graduate School of Natural Science and Technology, Okayama University Takayoshi Suzuki Research Institute for Interdisciplinary Science, Okayama University Masakazu Kita Faculty of Education, Okayama University (E)-N-Benzylidenepicolinohydrazide (Hbphz) was used to synthesize a series of hydrazonato-bridged homodinuclear Ln(2)(III) dithiocarbamato (RR'dtc(-)) complexes of the form [{Ln(RR' dtc)(2)}(2)(mu-bphz)(2)] {Ln= La, Pr, Nd, Sm or Eu; RR'= dimethyl-(Me-2) or pyrrolidine-(pyr)}. X-ray crystallographic studies revealed that these complexes possessed a common head-to-tail type dinuclear structural motif in which two hydrazonato ligands bridged two Ln(III) centers in the mu- 1 kappa N-2(py),O:2 kappa O-2,N(imine) mode and two RR'dtc ligands coordinated to each Ln(III) center. Interestingly, while the Sm-III and Eu-III complexes crystallized as simple 8:8-coordinate dinuclear molecules, the lighter Ln(III) (i.e. La-III, Pr-III and Nd-III) complexes afforded in some cases 9:9-coordinate molecules, where the ninth coordination site was occupied by a solvent ethanol or methanol molecule. Even for the lighter Ln(III) complexes, the complexes were solved in dichloromethane or chloroform as the 8:8-coordinate dimer, as revealed by H-1 NMR spectroscopy. In the UV-visible absorption and magnetic circular dichroism (MCD) spectra of the complexes, similar spectral patterns for ligand-centered and Laporte forbidden f-f transitions were observed. The MCD spectral studies demonstrated the characteristic magneto-optical behavior of the complexes. No potential conflict of interest relevant to this article was reported.