Speciation of complexes of Co (II), Ni (II) and Cu (II) with L-histidine in dioxan-water mixtures

Abstract

L-Histidine complexes of Co (II), Ni (II) and Cu (II) metal ions were studied pH-metrically in 0 -60% vyv dioxan -water mixtures at a temperature of 303 K and at an ionic strength of 0.16 mol L À 1 . Exhaustive modeling was performed to identify the species present in the present systems. The models contain MLH, ML 2 H 4 , ML 2 H 2 , ML 2 H and ML 2 for Co (II), ML 2 H 4 , ML 2 H 2 , ML 2 H and ML 2 for Ni (II), and MLH, ML 2 H 2 , ML 2 H and ML 2 for Cu (II). The appropriate experimental conditions were verified by introducing errors intentionally in the concentrations of ingredients. The trend in the variation of stability constants with the dielectric constants of dioxan is explained on the basis of electrostatic and non-electrostatic forces. The bioavailability of metals and their transportation are explained based on the distribution diagrams.

Electrometric Investigation of the Nature and Stability of Mixed Ligand Complexes of L-Ornithine and 1,10-Phenanthroline With Some Essential Metal Ions in Aqua-TBAB or PEG-400 Surfactant

“…The additions of PEG-400 and TBAB lowered the dielectric constant [6, 41,42] of the aqueous medium, thereby decreasing log β values.…”

Mononuclear Binary Complex Formation Equilibria of L-Ornithine with Biologically Essential Metals in TBAB Micellar Media

“…L-Ornithine (L-Orn) is a non-protein 2,5-diaminopentanoic acid whose metal complexes are insoluble in water and soluble in most organic solvents [9]. It is a tridentate ligand [10,11] and known to form several stable metal ion complexes in a variety of solvents differing in the degree of solubility: with Co(II), Ni(II) and Cu(II) [12][13][14][15][16][17][18][19][20][21][22]; Cd(II), Sn(IV), Ce(IV) and Pd(II) in different solvents [23][24][25][26][27]. L-Ornithine complexes of bio-essential metals play an important role in chemotherapeutic applications [28,29].…”