Non-covalent Interactions in Metal Complexes. II. Induction of Asymmetry in Cobalt(III) Complexes with Amino Acid–Schiff Bases. Importance of CH···π-Interaction in Determining Configuration of Complexes

Abstract

Abstract Cobalt(III) complexes, [Co(l-mop=aa)2]− and [Co(cop=aa)2]− (aa=ala−, val−, leu−, phe−), where H2(l-mop=aa) and H2(cop=aa) denote amino acid-Schiff bases of l-menthyl 3-(o-hydroxybenzoyl)propionate and cholesteryl 3-(o-hydroxybenzoyl)propionate, respectively, were prepared in solution. The intensity of the CD peak induced at 520 nm changes with the solvent used for preparation of the complex, decreasing in the order: ethanol, methanol, dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile. Since the order corresponds to the increasing order of the CH···π-interaction between the solvent and benzene, it seems that the CH···π-interaction between the chiral group and the aromatic nucleus in the ligand plays an important role in determining the configuration of the complexes.