Electronic Studies of Copper(II) Complexes of Amino Acids. III. EPR Spectra of Some Vitamin B6 Schiff Base Analogs

Schiff base coordination compounds of amino acids are good models to study the transamination reaction^2,3 of vitamin B₆. Several studies^4-6 have focused on the preparation, characterization and spectra study of these Schiff base coordination compounds, represented schematically in Figure 1, where R has been varied. In our continued studies of Cu(II) coordination compounds of amino acids, we have prepared a series of compounds with alanine (R=CH₃) and either a 4 or 5 substituent on the ring (X=H, OH, NO₂, Cl). In order to obtain as many of the EPR magnetic parameters as possible⁷, we prepared solid solutions in Zn(II) matrices with a Zn(II) to Cu(II) ratio of about 95:5. In this fashion we were able to reduce the dipole coupling and to calculate the [sgrave] molecular orbital coefficients for this important new series of compounds.