Equilibrium studies on chromium(III) complexes of salicylic acid and salicylic acid derivatives in aqueous solution.
The complexes of chromium(III) ion formed by salicylic acid, SA(H(2)L), and its derivatives (H(2)L): 5-nitrosalicylic acid (5-NSA), 5-sulphosalicylic acid (5-SSA) were investigated by means of potentiometry and spectroscopy, at 25 degrees C and in ionic strength of 0.1 M KNO(3) and 0.1 M KCl, respectively. Over the acidic pH range, the coordination of Cr(III) ion to SA and its derivatives in 1 : 1 mole ratio occurs, CrL(+) type complex is formed. In the excess of ligand, the coordination of the second ligand molecule is somewhat hindered; as a result CrL(HL) type complex occurs. Their existences were verified and their formation constants were determined. At near neutral pH, CrL(OH) and CrL(HL)(OH)(-) type hydroxo complexes formed by hydrolytic equilibria and their formation constants were also defined. The stabilities of Cr(III) complexes of SA and its derivatives decrease in the following order: SA>5-SSA>5-NSA. The formation constants of Cr(III) complexes of SA and its derivatives are in comparable ranges with the corresponding complexes of the 2,x-dihydroxybenzoic acid (2,x-DHBA) of Cr(III) ion. The stabilities of SA complexes for V(IV), Cr(III) and Fe(III) ions that have similar ionic radii, increase in the order VOL<CrL(+)<FeL(+). It is worthwhile noting that the binding ability of Cr(III) to salicylate ion is four orders of magnitude higher than to transferin, which is a blood serum protein and is associated with insulin action.
Aksoy
Mehmet Suat
MS
Department of Chemistry, Faculty of Arts and Science, Uludag University, 16059-Bursa, Turkey. msaksoy@uludag.edu.tr
Ozer
Ulviye
U
D002857:Chromium / Q000032:analysis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012459:Salicylates / Q000032:analysis / Q000737:chemistry; D020156:Salicylic Acid / Q000032:analysis / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000032:analysis / Q000737:chemistry
D012459:Salicylates; D012996:Solutions; D014867:Water; D002857:Chromium; C071881:5-nitroso-salicylate; D020156:Salicylic Acid