Mixed ligand complexes involved in the system pyridoxamine-glycylglycine-imidazole copper(II)

Complexes of Vitamin B6. 23. Interaction of Some Tertiary Ligating Amino Acids with the Binary Complexes of Ni(II) or Cu(II) and Pyridoxamine

“…Table lists the values of log K 1 and log K 2 whenever enough information about the pertinent binary formation constants is available. Statistically, log K 1 should be greater than −0.6 and log K 2 should be greater than +0.6 for ternary complex enhancement . The values shown in Table mostly abide with this argument except for those for a few monoprotonated and unprotonated species.…”

“…The stock solution concentrations (0.10 M) of CuCl 2 (BDH) and NiCl 2 (BDH) were standardized by complexometric EDTA titration, as previously reported. 6 Different ratios of the metals to the ligands were used in the potentiometric study (Table 1).…”

“…Aspartic (Asp) and glutamic (Glu) acids (Figure ), amino acids of possibly tridentate coordination nature, were selected to study their reaction with PM binary metal complexes …”

“…1,2 The binary PM-metal ion complexes have been shown to react with other mono-and bidentate ligands in solution to form ternary as well as quaternary complexes. 1,[3][4][5][6][7] In most cases protonated species have been shown to exist in a wide pH range. However, the reaction of tridentate ligands has not been studied with the binary complexes of pyridoxamine.…”

“…Aspartic (Asp) and glutamic (Glu) acids (Figure 1), amino acids of possibly tridentate coordination nature, were selected to study their reaction with PM binary metal complexes. 6 The importance of such studies lies in the fact that Asp and Glu are widely distributed in many biological systems, for example, in protein 8 and plasma, 9 and may compete for metal ions with other ligands, such as vitamin B 6 compounds, especially pyridoxamine. Besides, any experimental approach to answer questions concerning the biological action of chemical species depends on the accurate measurement of their concentrations in complex matrixes.…”