Metal Complexes of Amino Acids. II. The Absorption Spectra of Geometrical Isomers of Copper(II) Complexes

The geometrical structures of bis(α-amino-acidato)copper(II) complexes have been determined from the data of diffuse reflectance spectra (α-amino-acid = glycine, l- and Dl-α-alanine, l- and Dl-valine, l- and Dl-threonine, l- and Dl-isoleucine and α-aminoisobutyric acid). It has been shown that pairs of cis(N) and trans(N) isomers exist in glycinato and valinato complexes. It has been clarified that the other amino-acidato complexes studied exist either only in the cis(N) form or only in the trans(N) form; that is, the needle and the scaly complexes of Dl-alanine, the complexes of Dl- and l-threonine, and the complex of α-aminoisobutyric acid exist only in the trans(N) form, while the complexes of l- and Dl-isoleucine exist only in the cis(N) form.