PREPARATION AND ESR STUDY OF THE COMPLEXES OF L-HISTIDINE WITH ZINC AND CADMIUM

The preparation of the complexes Zn(Mn) (L-His)2 and Cd(Mn) (L-HiS)2 are reported . The E.S.R. spectra, at both X- and Q-band of Mn(II) ions doped in these complexes and also those of M(L-His)2.2H2O (M = Zn and Cd) are reported, and the zero-field splitting parameters D and (lambda = E/D) are deduced. Considerably higher values of D and lambda observed for M(Mn) (L-His)2.2H2O (M = Zn and Cd) suggest quite appreciable deviation from regular symmetry as would be expected from their crystal structure studies [1-2]. The distinctly lower values of D and lambda observed for anhydrous complexes, M(Mn)(L-His)2 (M - Zn and Cd), suggest geometries tending, most probably, towards regular octahedral structures. The negative sip of D observed from the Q-band spectra of these complexes, suggests that the principal D-tensor axis lies along the line of two Cd-N bonds, and the coordinated oxygens from the carbonyl groups are in cis-positions.

MARGARET GOODGAME ,IZHAR HUSSAIN ,