Metal Complexes of Amino Acids. I. The Circular Dichroism of Copper(II) Complexes with Optically Active Amino Acids

On the basis of the CD measurements of the complexes of the [Cu(l-am)2] type, four CD components have been observed in the region of the d→d absorption band, namely, (+), (+), (−) and (−), listing from longer to shorter wavelengths. The l-configuration of the amino acids determines the signs of these CD components. Judging from the CD curves of the copper-(II) complexes with l-threonine and with l-allothreonine, it has been suggested that the vicinal effect caused by the α-asymmetric carbon atom is stronger than that caused by the β-asymmetric one. It has also been suggested that, when l-proline or l-hydroxyproline is coordinated to copper, the nitrogen atoms of these ligands are activated by the configurational stereo specificity.