Effect of Water And Ethyl Alcohol Mixed Solvent System on the Stability of Beta-Hydroxy Ketone And Benzotriazole Ligands Metal Complexes (original) (raw)
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The stabilities of ternary complexes of metal ions (copper, nickel, zinc and cobalt) with beta-hydroxy ketone(BHK) derivatives and benzotriazole(BTAZ) derivatives in various mixed solvent systems (Water+Dioxane) medium in 0.1 M KNO3 ionic strength at 25 0 C using pH metric titration method have been established. The data reveal that the copper forms more stable complexes, which is followed by zinc and Ni complexes with these ligands. Cobalt form less stable complexes with these ligands. The stabilities of these complexes are further quantified with Δ log K values, intra-molecular equilibrium constants and percentage of stacking interaction in the ternary systems. The observed positive Δ log K values suggest that the flexible side chain alkyl moiety (ethyl group, butyl group) or aromatic moiety (phenyl group) in BHK ligand overlaps with the fixed aromatic moiety of BTAZ ligand in the ternary complex, which results in the enhanced stabilities for the (BHK-Alk)-Metal(II)-BTAZ and (BHK-Ph)-Metal(II)-BTAZ systems. Interestingly, the positive Δ log K values for both BHK-Alk and BHK-Ph ligands in their corresponding ternary complexes are about the same. This suggests the flexible Alkyl or phenyl side chain of BHK is overlapping with the triazole ring, but not the phenoxy ring of the BTAZ ligand.
The metal mediated intramolecular interactions and their stabilities have been established for the ternary complexes of metal ions (copper, nickel, zinc and cobalt) with beta-hydroxy ketone (BHK) derivatives (O-O donor atoms) and benzotriazole (BTAZ) derivatives (N-N and N-O donor atoms) in 50% water + 50% dioxane medium in 0.1 M KNO3 ionic strength at 25 o C using potentiometric pH titrations. The intramolecular interactions and the stabilities of these complexes are quantified in terms of Δ log K values, intra-molecular equilibrium constants and percentage of stacking interaction in the ternary systems. The observed positive Δ log K values suggest that the flexible side chain in BHK ligand having butyl and phenyl ring overlaps with the fixed aromatic moiety of BTAZ ligand in the ternary complex, which results in the enhanced stabilities for the ternary complexes. Based on the experimental data we conclude that, (i) the flexible side chains of BHK ligand having butyl and phenyl ring interacts with the heterocyclic ring of BTAZ ligand in the ternary metal-ligand complex, but not with aniline ring, (ii) ternary complexes with BTAZ having N-N donor atoms form more stable complexes over the BTAZ having N-O donor atoms and (iii) ternary complexes with copper forms more stable complexes, which is followed by zinc ion complexes with the ligands, and both nickel and cobalt form complexes with similar stabilities.
The stabilities of ternary complexes of metal ions (copper, nickel, zinc and cobalt) with beta-hydroxy ketone (BHK) derivatives and benzotriazole (BTAZ) derivatives in 50% water + 50% dioxane medium in 0.1 M KNO3 ionic strength at 25 o C using potentiometric pH titrations have been established. The data reveal that the copper forms more stable complexes, which is followed by zinc ion complexes with these ligands. Both nickel and cobalt form complexes with similar stabilities. The stabilities of these complexes are further quantified with Δ log K values, intra-molecular equilibrium constants and percentage of stacking interaction in the ternary systems. The observed positive Δ log K values suggest that the flexible side chain alkyl moiety (butyl group) or aromatic moiety (phenyl group) in BHK ligand overlaps with the fixed aromatic moiety of BTAZ ligand in the ternary complex, which results in the enhanced stabilities for the (BHK-Bu)-Metal(II)-BTAZ and (BHK-Ph)-Metal(II)-BTAZ systems. Interestingly, the positive Δ log K values for both BHK-Bu and BHK-Ph ligands in their corresponding ternary complexes are about the same. This suggests the flexible butyl or phenyl sidechain of BHK is overlapping with the triazole ring, but not the phenoxy ring of the BTAZ ligand.
American Journal of Analytical Chemistry, 2012
In this work, the synthesis and complexation properties of a new compound, 1,3-bis[5-(2-hydroxyphenyl)-4-phenyl-1,2,4-triazole-3-yl-thio]propane (BTP), towards certain transition metal ions, (M(II) where M = Zn, Cu, Ni) in acetonitrile is reported. A hard-modeling strategy was applied to UV-Visible spectroscopy data obtained from monitoring the reaction between BTP and the selected metal ions to determine the concentration profiles of each species and the corresponding stability constant(s) of the complex(es). The stability constants of complexes are always defined in terms of their free metal, free ligand and complexed forms. These constants are influenced by parameters such as the type of metal, ligand, counterion or solvent. In this study, the formation constants of the complexes were determined for the synthesized ligand with several metallic cations in acetonitrile solvent by UV-Vis spectrophotometry.
Pakistan journal of analytical & environmental chemistry, 2013
Interaction of 4-(2-hydroxy-1-naphthylmethylamino)-3-methyl-5-(4-tolyl)-4H-1,2,4-triazole with heavy metal cations such as Cu 2+ , Co 2+ , Cd 2+ , Ni 2+ and Pb 2+ was investigated by using UVvisible spectrophotometric technique. The complex stability constants (Log β) were determined in aqueous as well as in methanol: water (1:1) system at 25 ± 0.1°C by Buschmann's method and Valeur's methods, respectively. The ligand showed good sensitivity for Co 2+ with a linear range of 210-6 M to 310-5 M.
Assiut University Journal of Multidisciplinary Scientific Research, 2015
The complex-formation of the copper(II), rhenium(V) and nickel(II) metal ions with 2mercaptobenzothiazole (MBT) have been investigated in 1 M hydrochloric acid. The compositions of complexes were determined, and their stepwise stability constants were calculated at 298, 308 and 318 K. The thermodynamic parameters such as, Gibb's free energy change (∆G), entropy change (∆S) and enthalpy change (∆H) associated with the complexation reactions were calculated and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the metal complexes has been found to be endothermic and entropically favourable.
Korean Journal of Chemical Engineering, 2013
Solution equilibria of the binary and ternary complex systems of the divalent transition metal ions Cu 2+ , Ni 2+ , Zn 2+ , and Co 2+ with 1,2,4-triazole (TRZ), 3-mercapto-1,2,4-triazole (TRZSH), and 3-amino-1,2,4-triazole (TRZAM) and aromatic carboxylic acids (phthalic, anthranilic, salicylic, and 5-sulfosalicylic acid) have been studied pH-metrically at (25.0±0.1) o C, and a constant ionic strength I=1×10 −1 mol L −1 NaNO 3 in an aqueous medium. The potentiometric titration curves show that binary and ternary complexes of these ligands are formed in solution. The stability constants of the different binary and ternary complexes formed were calculated on the basis of computer analysis of the titration data. The relative stability of the different ternary complex species is expressed in terms of ∆ log K values, log X and R. S.% parameters. The effect of temperature of the medium on both the proton-ligand equilibria for TRZAM and phthalic acid and their metal-ligand equilibria with Cu 2+ , Ni 2+ , and Co 2+ has been studied along with the corresponding thermodynamic parameters. The complexation behavior of ternary complexes is ascertained using conductivity measurements. In addition, the formation of ternary complexes in solution has been confirmed by using UV-visible spectrophotometry.
The chelation abilities of 2-aminophenol and 3,4-dihydroxybenzoic acid with divalent metal ions (Cu 2+ , Be 2+ , Zn 2+ , Ni 2+ , Co 2+ and Mn 2+ ) in binary and ternary systems at 37 ± 0.1°C and an ionic strength of 0.15 mol dm À3 NaCl were systematically investigated by using the potentiometric titration method. The chelating abilities of these complexes were obtained by processing the titration data using the Hyperquad2008 program and the results are presented as stability constants. In a binary system, it was shown that metal complexation involving 3,4-dihydroxybenzoic acid (ligand D) is more stable than the one with 2-aminophenol (ligand A). The stability of the formed metal complexes, both in binary and ternary systems, decreases in the following order: Cu 2+ > Be 2+ > Zn 2+ > Ni 2+ > Co 2+ > Mn 2+ . The tendency of these metals and ligands to form binary or ternary complexes was also evaluated and discussed by calculating their Dlog K M and log X values. In addition, the distribution of complex species in these systems was graphically presented using the HySS2009 program. UV-Vis spectrophotometry was also performed to qualitatively verify the protonation of these ligands and to confirm the model of the complex formed.
Journal of Coordination Chemistry, 2012
Potentiometric equilibrium measurements have been performed at 25 AE 0.1 C and I ¼ 0.10 mol dm À3 NaNO 3 for the interaction of 1,2,4-triazole and M(II) [Cu, Co, Ni, and Zn] with some biologically important ligands (glycine, -alanine, DL-valine, n-valine, DL-leucine, serine, aspartic acid, histidine, and asparagine). Ternary complexes are formed by a stepwise mechanism. The relative stabilities of the ternary complexes are compared with those of the corresponding binary complexes in terms of Dlog K, log X, and % R.S values. The concentration distribution curves of the various binary and ternary species in a solution were evaluated as a function of pH.