Crystal structures and circular dichroism of {2,2′-[(1<i>S</i>,2<i>S</i>)-1,2-diphenylethane-1,2-diylbis(nitrilophenylmethanylylidene)]diphenolato}nickel(II) and its ethanol solvate

The title compound, [Ni(C₄₀H₃₀N₂O₂)] (<b>1</b>), with an optically active Schiff base ligand derived from 2-hy-droxy-benzo-phenone and (1<i>S</i>,2<i>S</i>)-1,2-di-phenyl-ethyl-enedi-amine, was crystallized as the solvent-free and ethanol solvate forms (<b>1</b> and <b>1</b>·2C₂H₅OH). In both structures, the two phenyl groups on the stereogenic centers of the <i>O</i>,<i>N</i>,<i>N</i>,<i>O</i>-tetra-dentate ligand are axially oriented, and the conformation of the central di-amine chelate ring is λ. The circular dichroism (CD) spectra of <b>1</b> and the analogous nickel(II) complex [Ni(C₃₀H₂₆N₂O₂)] (<b>2</b>) in solution show partially similar patterns in the 350-450 nm range, but are mirror images in the longer wavelength region (450-650 nm). In the latter region, the sign of CD for these complexes is sensitive to the substituents on the C=N carbon atoms (phenyl for <b>1</b> and methyl for <b>2</b>) rather than the di-amine chelate ring conformation.