Potentiometric Study of Binary and Mixed Complexes of Imidazole, Histamine, Histidine and Diacetyl Monooxime with Some Transition Metal Ions in Aqueous Solution

The complexation reactions between diacetyl monooxime (Damo), imidazole (Him), histamine (Hist) and histidine (His) with Co2+, Ni2+ and Cu2+ were studied potentiometrically in aqueous solution at 25 °C and m= 0.5 M KNO3. The overall stability constants log b's of species were obtained by computer refinement of pH-volume data using BEST computer program. Several models were tested and, based on the lowest sFIT , the best one is accepted. The main species in binary complexes are MAH, MA2, MA2H, MA2H2, (in MA3 and MA4 A=Him), and for ternary complexes are MAB, MA2B, MAB2 and MABH. The D log KMAB and log XMAB were calculated for MAB mixed complexes. The order found for the resulting stability constants vary as Co2+ < Ni2+ < Cu2+.