Infrared Absorption Spectra and Normal Coordinate Analysis of Metal-Dl-Tyrosine Chelates

Abstract The infrared absorption spectra of Dl-tyrosine and six metal Dl-tyrosine chelates have been investigated from 4000 to 300 cm−1. A detailed normal coordinate analysis was performed for the metal chelates as a 39-body problem and an approximate description of the vibrational modes has been assigned to the observed frequencies. Dl-Tyrosine chelates are found to be coordinated with the metal through nitrogen and oxygen and to have a trans configuration; the same is true for other aliphatic amino acid chelates. The bond-stretching force constants for the metal-nitrogen bonds have been found to decrease in the order Pd(II)>Cu(II)>Zn(II)>Cd(II)>Ni(II)>Co(II). The calculated frequencies, which were obtained using the same force constants as in other aliphatic amino acid chelates, were in good agreement with the observed frequencies.