Dinuclear lanthanoid(III) dithiocarbamato complexes bridged by (E)-N-benzylidenepicolinohydrazonate: Syntheses, crystal structures and spectroscopic properties

(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.

© 2019 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 License.http://creativecommons.org/licenses/by-nc-nd/4.0/.This is the accepted manuscript version. The formal published version is available at https://doi.org/10.1016/j.ica.2019.119124