Quantum-chemical calculations of the tautomeric forms of azo derivatives of acetylacetone and determination of the stability constants of their complexes with rare-earth metals

Quantum-chemical calculations, tautomeric, thermodynamic, spectroscopic and X-ray studies of 3-(4-fluorophenylhydrazone)pentane-2,4-dione

“…Inspection of these values reveals that [38][39][40][41][42]: i The pL values decrease with increasing temperature revealing that its acidity increases with increasing temperature; ii A positive value of DH o indicates that its dissociation is accompanied by adsorption of heat and the process is endothermic; iii A large positive value of DG o indicates that the dissociation process is not spontaneous; iv A negative value of DS o is obtained due to increased order as a result of solvation processes.…”

Ion Pairs of 5,5-dimethyl-2-(2-hydroxy-3,5-disulfophenylhydrazo)cyclohexane-1,3-dione with Cationic Surface-Active Substances as Analytical Reagent for Determination of Copper(II)

“…The dissociation constants of the reagent were found to be pK 1 ¼ 5.90 AE 0.03 and pK 2 ¼ 9.67 AE 0.04. Earlier, it was assumed (Gadjieva, Pashaev et al 2007;Gadjieva et al 2008;Alieva et al 2009;Gadjieva, Mursalov, Mahmudov, Pashaev et al 2006) that ADB occurs in three tautomeric forms (enol-azo, keto-azo and hydrazo, Scheme 2), and, according to quantum chemical calculations performed on similar compounds, pK 1 characterizes the proton abstraction from the ÀOH group of the aromatic ring situated in the ortho position to the hydrazo group of the molecule, while pK 2 concerns the deprotonation of the hydrazone group (=NÀNHÀ) .…”

“…The ADB and their metal complexes are known to exist in different tautomeric forms, which can substantially complicate their study (Gadjieva, Pashaev et al 2007;Gadjieva et al 2008;Alieva et al 2009). In addition, since the tautomers of a compound usually differ in thermodynamic stability, the equilibrium constants of complexation should differ for different tautomers of a ligand Gadjieva, Mursalov, Mahmudov, Pashaev et al 2006).…”

Poly(vinyl) chloride membrane copper-selective electrode based on 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione

“…Previously, it was shown that azoderivatives of ␤-diketones (ADB) have a rich tautomeric potential (Scheme 1) and can be used for the classical spectrophotometric determination of copper(II) [65][66][67][68][69][70]. It was concluded that when azoderivatives of unsymmetric ␤-diketones are used, the number of ADB tautomers increases along with selectivity of copper analysis [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. For this reason, in this work we tested an unsymmetric ADB, i.e.…”