Coordination complexes of amino acids: Preparation and properties of some Amino-acidatobis(acetylacetonato)cobalt(III) and Bis(amino-acidato)(acetylacetonato)cobalt(III) complexes

Abstract

Complexes of the type [Co(acac)₂(aa)] have been synthesized, in which the amino acid is DL- and L-phenylalanine, L-valine, L-leucine, L-proline, DL-, L-,and D-alanine, and glycine. The complexes were characterized by means of analyses, molecular weights, and their infrared, visible, and ultraviolet absorption spectra. During the syntheses several of the bis(amino-acidato) complexes, [Co(acac)(aa)₂], were also formed; the L-phenylalanine and glycine complexes were isolated and characterized. The complexes prepared from the optically active amino acids exhibited Cotton effects in the region of the visible absorption band (^lA_1g, + ¹T_1g). These effects have been attributed to induced asymmetry rather than stereoselectivity. Amino acids of the same configuration gave rise to Cotton effects of the same sign, ie. (-)₅₉₀-[Co(acac)₂(L-aa)], (-)6₅₉₀-[Co(acac)(L-aa)₂], and (+)₅₉₀-[Co(acac),(D-aa)].