The circular dichroism
spectra of a series of optically active (α-aminocarboxylato)tetraamminecobalt(111) complexes have been measured in
aqueous solution, and in the presence of salts of polarizable
anions. The observed spectra in the visible region have been analysed to
determine the signs of the Cotton effects of the three components of the 1A1g ↔ 1T1g
cobalt(111) transition. For L-amino acids, the transition with A2g(D4h)
parentage is negative, and the two transitions with Eg(D4h) parentage have opposite
signs. Published circular dichroism spectra of complexes of the type [Co(en)2(L-am)]2+
were similarly interpreted in terms of a perturbed tetragonal chromophore, and
it was shown that the vicinal effect of the L-amino acids imposed the same
signs onto the component transitions as for the tetraammines
and for a similar series of pentaamminecobalt(111) complexes.