A NdIII enantiomeric pair: Synthesis, crystal structures and near-infrared luminescent properties

Based on enantiopure bis-bidentate N-donor ligands (-)/(+)-2,5-bis(4,5-pinene-2-pyridyl)pyrazine (L-R/L-s), a new pair of Nd-III enantiomers with the formula Nd(dbm)(3)L-R/s.2H(2)O (R-1 and S-1 being the isomers containing the L-R and L-s ligands, respectively, and dbm = dibenzoylmethanate) have been isolated and characterized by X-ray crystallography and spectroscopic methods. Notably, unlike our previously reported homodinuclear Eu-III and Dy-III complexes based on the identical ligands (L-R and L-s), the dinuclear Nd-III congener have not been obtained by controlling the ligand-to-metal ratio as expected, the reason of which was elucidated in this work. The crystal structure analyses of R-1 and S-1 reveal that they are mononuclear Nd-III complexes and crystallize in chiral space group P2(1)2(1)2(1) of the orthorhombic system. Circular dichroic (CD) spectra confirmed their chiroptical activities and enantiomeric nature. The photoluminescence investigations showed that they display characteristic near-infrared (NIR) emissions of the Nd-III ions with notable emitting lifetime value. (C) 2016 Elsevier B.V. All rights reserved.