Crystal structures and circular dichroism of {2,2'-[(1S,2S)-1,2-di-phenyl-ethane-1,2-diylbis(nitrilophenyl-methanylyl-idene)]diphenolato}nickel(II) and its ethanol solvate.

The title compound, [Ni(C(40)H(30)N(2)O(2))] (1), with an optically active Schiff base ligand derived from 2-hy-droxy-benzo-phenone and (1S,2S)-1,2-di-phenyl-ethyl-enedi-amine, was crystallized as the solvent-free and ethanol solvate forms (1 and 1·2C(2)H(5)OH). In both structures, the two phenyl groups on the stereogenic centers of the O,N,N,O-tetra-dentate ligand are axially oriented, and the conformation of the central di-amine chelate ring is λ. The circular dichroism (CD) spectra of 1 and the analogous nickel(II) complex [Ni(C(30)H(26)N(2)O(2))] (2) 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 1 and methyl for 2) rather than the di-amine chelate ring conformation.