Binary and ternary nickel (II) complexes with 2-methylquinoline-8-carboxylic acid and some amino acids

In this work, the ligand 2-methylquinoline-8-carboxylic acid (HL) was prepared using a modification of a previous protocol, and its protonation constants were studied. The stability constants of the binary nickel (II) - ligand L- and the ternary nickel (II) - ligand L- - amino acids (B-) systems were investigated. The amino acids selected for this study were glycine (Gly), alpha-alanine (alpha Ala), beta-alanine (beta Ala), proline (Pro), serine (Ser), methionine (Met), threonine (Thr), phenylalanine (Phe), aspartic acid (Asp), glutamic acid (Glu), histidine (His) and cysteine (Cys). The stability constants were pH-metrically measured in 1.0 mol dm(-3) NaCl at 25 degrees C. The least squares program LETAGROP was used for the analysis of the potentiometric data. Species distribution diagrams as a function of pH are briefly discussed.

Automated summary

This study involves the synthesis of ligand HL and the investigation of its protonation constants, as well as the investigation of stability constants of binary and ternary nickel-ligand systems. Experimental measurements of stability constants were conducted with various amino acids under different pH conditions, and species distribution diagrams were briefly discussed.