INVESTIGATION OF CONFORMATIONAL AND VICINAL OPTICAL-ACTIVITY OF MONO(S-AMINOCARBOXYLATO)COBALT(III) COMPLEXES

Conformational and vicinal optical activities of four classes of mixed mono(S-aminocarboxylato)cobalt(III) complexes, lacking configurational dissymetry, were studied. The effect of conformational changes of aminocarboxylato chelate ligands containing various ring side alkyl groups, caused by the replacement of a relatively small ammine by a bulky nitro ligand, were followed. Solution CD spectra supported the earlier conclusion that the more axially oriented chelate ring side group of an S-aminocarboxylato ligand produces a larger negative dichroism in the region of the first, spin allowed, d-d electronic transition. Solid-state CD spectra enabled the application of the theoretically based sector rules for optical activity in cobalt(III) complexes to the four investigated complexes, for which crystal structures have been determined. It emerged that an axial orientation of the aminocarboxylato chelate ring side alkyl is very effective, not only due to the displacement of this alkyl from an equatorial position, nodal plane of the Sector rule, but also due to the proximity of the oriented group to the metal centre.