The Effect of Metal Ion Chelation on the Acid Dissociation of the Ligand 4-(2-Pyridylazo)-resorcinol

1963 ◽  
Vol 2 (1) ◽  
pp. 224-226 ◽  
Author(s):  
Alfio Corsini ◽  
Quintus Fernando ◽  
Henry Freiser
Keyword(s):  
Metal Ion ◽  
Acid Dissociation ◽  
Metal Ion Chelation

Tripodal trisamides based on nicotinic and picolinic acid derivatives

1998 ◽  
Vol 76 (4) ◽  
pp. 414-425 ◽  
Author(s):  
H R Hoveyda ◽  
Veranja Karunaratne ◽  
Christopher J Nichols ◽  
Steven J Rettig ◽  
Ashley KW Stephens ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Metal Ion ◽  
Dissociation Constants ◽  
Picolinic Acid ◽  
Direct Methods ◽  
Acid Dissociation ◽  
Coupling Reagent ◽  
Picolinic Acids ◽  
Metal Ion Chelation ◽  
Derivatives Of

A number of polydentate arylamide ligands have been prepared by coupling various acyclic tripodal or linear polyamines with derivatives of nicotinic and picolinic acids. Two synthetic procedures were utilized; tris{[(2-hydroxynicotinyl)carbonyl]-2-aminoethyl}amine (H3NICTREN) was prepared by Method A, the HOSu/DCC method, and the other arylamides in this study were prepared by Method B, the CDI method. Method A involved the reaction of N-hydroxysuccinimide with 2-hydroxynicotinic acid (in the presence of dicyclohexylcarbodiimide (DCC) as a dehydrative coupling reagent) to form the succinimide ester, followed by reaction with TREN to yield H3NICTREN. Method B involved reaction of a carboxylic acid (2-hydroxynicotinic, 3-hydroxypicolinic, nicotinic, or picolinic acids) with carbonyldiimidazole (CDI) to form the N-acylimidazolide, followed by reaction with the amine (TREN, TAME, spermidine, or TRPN) to yield the desired arylamide. The X-ray structure of 1,1,1-tris{[(3-hydroxypicolinyl)carbonyl]-2-aminomethyl}ethane (H3PICTAME) was determined; crystals of H3PICTAME are monoclinic, a = 10.257(2), b = 15.572(3), c = 15.208(2) Å, β = 96.124(15)°, Z = 4, space group P21/a. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R = 0.041 and Rw = 0.038 for 2506 reflections with I >= 3 sigma (I). In the solid state, H3PICTAME contains an extensive hydrogen-bonding network, with eight intra- and one intermolecular H-bonds per molecule; the ligand is partially preorganized for metal ion chelation. The acid dissociation constants of H3NICTREN and those of 1,1,1-tris{[(2-hydroxynicotinyl)carbonyl]-2- aminomethyl}ethane (H3NICTAME) have been determined; pKa1 = 11.2 (10.68), pKa2 = 10.7 (10.58), pKa3 = 10.0 (9.71), and pKa4 = 6.25 for H3NICTREN (H3NICTAME); the high phenolic pKa's are consistent with the hydrogen bonding observed in the solid state.Key words: arylamide, hydrogen bonding, preorganization.

Marine Metabolites and Metal Ion Chelation

2012 ◽  
pp. 861-892 ◽  
Author(s):  
Stephen H. Wright ◽  
Andrea Raab ◽  
Jörg Feldmann ◽  
Eva Krupp ◽  
Marcel Jaspars
Keyword(s):  
Metal Ion ◽  
Marine Metabolites ◽  
Metal Ion Chelation

Structural diversity in metal ion chelation, and the structure of uro'gen III synthase

2002 ◽  
Vol 30 (3) ◽  
pp. A48-A48
Author(s):  
H. L. Schubert ◽  
E. Raux ◽  
M. A. A. Mathews ◽  
J. D. Phillips ◽  
K. S. Wilson ◽  
...  
Keyword(s):  
Metal Ion ◽  
Structural Diversity ◽  
Metal Ion Chelation

scholarly journals Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives

2021 ◽  
Author(s):  
Ransel Barzaga ◽  
Lucia Lestón-Sánchez ◽  
Fernando Aguilar-Galindo ◽  
Osvaldo Estévez-Hernández ◽  
Sergio Díaz-Tendero
Keyword(s):  
Heavy Metal ◽  
Metal Ion ◽  
Heavy Metal Ion ◽  
Thiourea Derivatives ◽  
Synergy Effects ◽  
Metal Ion Chelation

Electronic Effects on the Bergman Cyclisation of Enediynes. A Review

2004 ◽  
Vol 69 (5) ◽  
pp. 945-965 ◽  
Author(s):  
Michael Klein ◽  
Thomas Walenzyk ◽  
Burkhard König
Keyword(s):  
Experimental Data ◽  
Metal Ion ◽  
Substituent Effects ◽  
Terminal Alkyne ◽  
Electronic Effects ◽  
Ring Strain ◽  
Clear Cut ◽  
Theoretical Predictions ◽  
Metal Ion Chelation

The thermal cyclisation of enediynes to benzene-1,4-diyl diradicals (Bergman cyclisation) is affected by geometrical and electronic conditions. While the effect of ring strain or conformational constrains on the cyclisation temperature has been investigated in detail, electronic contributions have been less studied. Often geometrical and electronic contributions cannot be clearly distinguished. In most cases metal ion chelation does involve both. In this review we have summarised clear-cut observations of electronic substituents effects on the thermal enediyne reactivity. The effects of substituents in the vinylic and terminal alkyne position, the influence of benzo-fusion and hetarene fusion, as well as the changes induced by heteroatoms in the enediyne skeleton, are within the scope of this review. With the exception of more complex heterocyclic hetarene-fused enediynes the experimental data of electronic substituent effects on the thermal Bergman cyclisation of enediynes follow theoretical predictions. A review with 57 references.

Kinetics and Equilibrium of Binding of Fe3+ by a Fulvic Acid: A Study by Stopped Flow Methods

1975 ◽  
Vol 53 (20) ◽  
pp. 2979-2984 ◽  
Author(s):  
Cooper H. Langford ◽  
Tahir R. Khan
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Fulvic Acid ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Solution Ph ◽  
Sulfosalicylic Acid ◽  
Flow Measurements

The first report of a rate of binding of a metal ion (Fe3+) by a soluble fulvic acid is derived from stopped flow measurements. The rate of complex formation is normal in Wilkins' sense and similar to that for sulfosalicylic acid. Dissociation is slow (t1/2 > 10 s). The binding of Fe3+ by the fulvic acid in acid solution, pH = 1–2.5, was investigated by kinetic analysis in which the reaction of free Fe3+ with sulfosalicylic acid was followed by stopped flow spectrophotometry on a time scale short compared to release of Fe3+ by fulvic acid. Conditional equilibrium constants found were 1.5 ± 0.3 × 104 at pH = 1.5 and 2.5, and 2.8 ± 0.3 × 103 at pH = 1.0 at 25 °C (ionic strength 0.1).

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