Potentiometric and thermodynamic studies of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)-sulfamoyl]phenylazo}-2-pyrazolin-5-one and its metal complexes

2006 ◽  
Vol 60 (1) ◽  
Author(s):  
A. Fouda ◽  
A. Al-Sarawy ◽  
E. El-Katori
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Stability Constants ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Effect Of Temperature ◽  
Water Mixture ◽  
Dissociation Process ◽  
The Stability ◽  
Metal Ligand

AbstractThe dissociation constants of 3-methyl-1-phenyl-{p-[N-(pyrimidin-2-yl)sulfamoyl]phenylazo}-2-pyrazolin-5-one and metal-ligand stability constants of its complexes with some transition metal ions have been determined potentiometrically in 0.1 M-KCl and ethanol—water mixture (30 vol. %). The order of the stability constants of the formed complexes increases in the sequence Mn2+, Co2+, Ni2+, Cu2+, La3+, Hf3+, UO22+, Zr4+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes was found to be spontaneous, exothermic, and entropically favourable.

Thermodynamics of substituted pyrazolone. V: Potentiometric and conductometric studies of complexes of some transition metals with 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one

1999 ◽  
Vol 77 (7) ◽  
pp. 1305-1309 ◽  
Author(s):  
Ashraf A El-Bindary ◽  
Adel Z El-Sonbati ◽  
Hanan M Kera
Keyword(s):  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Water Mixture ◽  
Dissociation Process ◽  
Different Temperatures ◽  
The Stability ◽  
Dissociation And Stability Constants ◽  
Key Words 4

Proton-ligand dissociation constants of 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one (AHMP) and metal-ligand stability constants of its complexes with some transition metal ions were calculated potentiometrically in 0.1 M KCl and 50% (v/v) ethanol-water mixture. The order of stability constants was found to be Th4+ > UO22+ > Ce3+ > La3+ > Mn2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The dissociation constant, pK1H, of AHMP and the stability constants, log K, of their complexes were determined at different temperatures (298, 308, and 318 K). The corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic, and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, exothermic, or endothermic (depending the metal), and entropically favourable. The stoichiometries of these complexes were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. Key words: 4-(4-acetophenyl)hydrazono-3-methyl-2-pyrazolin-5-one, dissociation and stability constants, thermodynamic parameters, stoichiometries.

Metal Complexes of 6-Hydroxymethylpyridine-2-carboxylic Acid

1962 ◽  
Vol 15 (4) ◽  
pp. 786 ◽  
Author(s):  
RW Green ◽  
GKS Ooi
Keyword(s):  
Carboxylic Acid ◽  
Transition Metal ◽  
Metal Ions ◽  
Metal Complexes ◽  
Stability Constants ◽  
Steric Hindrance ◽  
Transition Metal Ions ◽  
Complexing Agent ◽  
Ph Titration ◽  
The Stability

Spectrophotometric and pH-titration methods have been used to determine the stability constants at 25 �C of complexes between transition metal ions and the anion of 6-hydroxymethylpyridine-2-carboxylic acid. This anion is found to be a weaker base and a weaker complexing agent than the pyridine-2-carboxylate ion. There is some evidence for steric hindrance of tris complexes.

scholarly journals Potentiometric and spectrophotometric studies of the complexation of Schiff-base hydrazones containing the pyrimidine moiety

2003 ◽  
Vol 68 (10) ◽  
pp. 729-749 ◽  
Author(s):  
H.S. Seleem ◽  
B.A. El-Shetary ◽  
S.M.E. Khalil ◽  
M. Shebl
Keyword(s):  
Schiff Base ◽  
Ionic Strength ◽  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Elemental Analysis ◽  
Mass Spectra ◽  
Dissociation Constants ◽  
The Stability ◽  
Pyrimidine Moiety ◽  
Metal Ligand

Three Schiff-base hydrazones (ONN ? donors) were prepared by condensation of 2-amino-4-hydrazino-6-methylpyrimidine with 2-hydroxyacetophenone 2-methoxybenzaldehyde and diacetyl to yield 2-OHAHP, 2-OMeBHPand DHP respectively. The structures of these ligands were elucidated by elemental analysis, UV, IR, 1H-NMR and mass spectra. The metal?ligand stability constants of Mn2+, Fe3+,Co2+,Ni2+,Cu2+, Zn2+,Cd2+,UO22+ and Th4+ chelates were determined potentiometrically in two different media (75%(v/v) dioxane?water and ethanol?water) at 283, 293, 303 and 313 K at an ionic strength of 0.05 M (KNO3). The thermodynamic parameters of the 1:1 and 1:2 complexes were evaluated and are discussed. The dissociation constants of 2-OHAHP, 2-OMeBHP and DHPligands and the stability constants of Co2+, Ni2 and Cu2+ with 2-OHAHP were determined spectrophotometrically in 75 % (v/v) dioxane?water.

Chelating Tendencies of Some N-(2-Acetyl-1,3-Indandione) Trialkyl Ammonium Iodides with Transition Metal Ions

1973 ◽  
Vol 28 (5-6) ◽  
pp. 317-318 ◽  
Author(s):  
M. K. Bachlaus ◽  
K. L. Menaria ◽  
P. Nath
Keyword(s):  
Free Energy ◽  
Complex Formation ◽  
Transition Metal ◽  
Copper Complex ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Iron Complex ◽  
Potentiometric Studies ◽  
Kcal Mole ◽  
The Stability

The ligands T.P.A.I.* and T.B.A.I.** have been synthesised and their dissociation constants are 1.738 · 10-10 and 1.412 · 10-8 respectively. The potentiometric studies show that these reagents form 1 : 1 complex with copper(II) and iron(II). The stability constants of copper complex and iron complex with T.P.A.I. are 6.43 and 6.51 respectively and for T.B.A.I. 4.36 and 4.24 respectively. The free energy of complex formation at 25°C are 8.76 Kcal/mole and 8.87 Kcal/mole for Cu (II)-T.P.A.I. and Fe (II)-T.P.A.I. respectively, whereas the free energy of the Cu (II)-T.B.A.I. and Fe(II)-T.B.A.I. are 5.94 Kcal/mole and 5.78 Kcal/mole respectively.

Selenosemicarbazone Metal Complexes as Potential Metal-based Drugs

2021 ◽  
Vol 29 ◽  
Author(s):  
Santiago Rostán ◽  
Graciela Mahler ◽  
Lucía Otero
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Biological Activities ◽  
Inorganic Compounds ◽  
Transition Metal Ions ◽  
The Other ◽  
Drug Synergism ◽  
Multiple Mechanism ◽  
Bioactive Ligands ◽  
The Stability

Abstract: The discovery of the anticancer activity of cisplatin has marked the emergence of modern Inorganic Medicinal Chemistry. This field of research is concerned with the application of inorganic compounds to therapy or diagnosis of disease. In particular, metal coordination of bioactive ligands has gained recognition in drug design. The interaction between transition metal ions and the organic drugs could enhance their diagnostic and therapeutic potentials by improving the stability and/or bioavailability or by achieving a metal-drug synergism through a dual or multiple mechanism of action. The isosteric replacement of sulfur by selenium in thiosemicarbazones leads to selenosemicarbazones. This class of compounds exhibit numerous biological activities like antitumor, antimicrobial, antiviral etc. and, in most cases, they were more pronounced in comparison to the sulfur analogues. On the other hand, while the effect of transition metal complexation on the biological activity of thiosemicarbazones has been widely studied, the pharmacological activity of the corresponding metal-selenosemicarbazone compounds has been less explored. In this work, the most relevant results related to the selenosemicarbazone metal complexes as potential metal-based drugs have been reviewed.

Using Linear Free Energy Relationship to Predict the Stability Constants of Aqueous Complexes of Metal-Organic Ligands

2004 ◽  
Vol 824 ◽  
Author(s):  
Huifang Xu ◽  
Yifeng Wang
Keyword(s):  
Free Energy ◽  
Metal Complexes ◽  
Stability Constants ◽  
Metal Cation ◽  
Dissociation Constants ◽  
Natural Environments ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Linear Free Energy ◽  
The Stability

AbstractThe Sverjensky-Molling linear free energy relationship was originally developed to correlate the Gibbs free energies of formation of an isostrutural family of solid phases to the thermodynamic properties of aqueous cations. In this paper, we demonstrate that the similar relationship also exists between metal complexes and simple metal cations in aqueous solutions. We extend the Sverjensky-Molling relationship to predict the Gibbs free energies of formation or dissociation constants for a family of metal complexes with a given complexing ligand. The discrepancies between the predicted and experimental data are generally less than 1.5 kcal/mol (or one log unit for stability constants). The use of this linear free energy correlation can significantly enhance our ability to predict the speciation, mobility, and toxicity of heavy metals in natural environments. According the obtained results, Gibbs free energies of formation of cations (δG0f, Mn+) can be used as an indicator for the hardness/softness of a metal cation (acid). The higher negative value of a metal cation, the harder acid it will be. It is logical to postulate that the coefficient a*ML characterizes the softness of a complexing ligand (base).

Study of the properties of pyridine-2-azo-p-phenyltetramethylguanidine as a metal ion complexing agent

1991 ◽  
Vol 69 (8) ◽  
pp. 1238-1244 ◽  
Author(s):  
Kenneth T. Leffek ◽  
Arnold Jarczewski
Keyword(s):  
Complex Formation ◽  
Stability Constants ◽  
Metal Ion ◽  
Nmr Spectra ◽  
Dissociation Constants ◽  
Activation Parameters ◽  
Complexing Agent ◽  
The Stability ◽  
Metal Ligand ◽  
C Nmr

Pyridine-2-azo-p-phenyltetramethylguanidine (PAPT) was synthesized and the properties of this compound examined. The dissociation constants of the conjugate acids in H2O are [Formula: see text] and [Formula: see text] at 25 °C at I = 0.1, and in acetonitrile are [Formula: see text] and [Formula: see text]. The properties of metal–ligand chelates in acetonitrile have been examined and the stability constants for Ni2+, Co2+, and Zn2+ complexes measured. The rates of reaction of PAPT with Ni2+, Co2+, and Zn2+ in acetonitrile have been determined and the activation parameters measured for the complex formation of LNi2+. The stability constants for both complexing centres of PAPT have been calculated. The 13C NMR spectra for PAPT and LNi2+ are quoted. The expected enhancement of the metal ion complexing ability of PAPT due to the strongly electron-releasing nature of the tetramethylguanidinyl group was not found. Key words: metal ion complexes, pyridine-2-azo-p-phenyltetramethylguanidine, stability constants, pKa.

Composition and stability of some bivalent transition metal complexes of 3,5-dinitrosalicylic acid

1970 ◽  
Vol 48 (6) ◽  
pp. 1007-1010 ◽  
Author(s):  
S. S. Dube ◽  
S. S. Dhindsa
Keyword(s):  
Transition Metal ◽  
Comparative Study ◽  
Metal Ions ◽  
Metal Complexes ◽  
Stability Constants ◽  
Transition Metal Complexes ◽  
Bivalent Metal ◽  
Bivalent Metal Ions ◽  
The Stability ◽  
Bivalent Transition Metal

The interaction of Zn2+, Mn2+, Hg2+, and Cd2+ ions with 3,5-dinitrosalicylic acid was investigated by potentiometric titrations in aqueous 0.1 M KNO3 medium. In all cases the formation of 1:1 complex was indicated. The stability constants in the pH ranges 4.5–8.0, 4.5–8.0, 5.0–8.0, and 5.5–8.0 were determined by applying the Calvin and Melchior's extension of Bjerrum's method and the log K values were found to be 3.70, 2.95, 3.20, and 2.85, respectively. A comparative study of the complexes of 3,5-dinitrosalicylic acid with other bivalent metal ions has also been incorporated. The stability constants of the transition metal complexes obey the order Cu > Ni > Co > Zn > Mn, in agreement with Irving and William's rule.

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