Interaction of aromatic amino acids with metal hexacyanochromate(III) complexes: A possible role in chemical evolution

Metal cyanogen complexes have been proposed to be efficient prebiotic catalysts. Insoluble metal cyanogen complexes are thought to have concentrated biomonomers from dilute prebiotic soup which facilitated a class of prebiotic reactions. Thus, large biopolymers were able to form during the course of chemical evolution and the origin of life. Based on this hypothesis, the interaction of two naturally occurring alpha-aromatic amino acids, tryptophan and phenylalanine, with cobalt(II), copper(II), and cadmium(II) hexacyanochromate(III) has been studied, and the interaction was found to be strongest at neutral pH (approximate to 7.0). Cobalt(II) hexacyanochromate(III) adsorbed the largest amount of both amino acids while tryptophan had a stronger affinity than phenylalanine. Infrared spectral studies of the metal hexacyanochromate(III) complexes, amino acids and metal hexacyanochromate(III)-amino acid adducts indicated the involvement of NH2 as well as COO- groups of amino acids and surface metal ions present in the lattice of the metal hexacyanochromate(III) complexes.