A comparison of the acidity and the complexing ability of (o-hydroxyphenyl) bis- and (o-hydroxyphenyl) mono-methylenephosphonic acids towards lanthanide(III) ions

Abstract

The characterization of the acid-base properties of a family of three phenoldimethylenephosphonic acids differently substituted by auxo-or chromophoric groups was studied. These ligands may be considered as pentaacids. Their pK a were determined in aqueous solution at 25°C and constant ionic strength 0.1 mol dm − 3 by potentiometry and UV-visible spectrophotometry. Eventually, the complexing power of these molecules with lanthanide cations, Ce 3 + , Pr 3 + , Nd 3 + , Sm 3 + and Eu 3 + , was studied keeping in view the possible application to the treatment of radioactive liquid waste. The number, the nature of the species in solution, their stability constants and their individual electronic spectra as restored by computation have been determined. In all cases, complexes of 1:1 stoichiometry accompanied by hydroxy and protonated species are postulated. The comparison of tri-and pentaacids confirms that the acids having the methyl group at the para position with respect to the phenolic OH, have the highest complexing power.

Novel polydentate phosphonic acids: Protonation and stability constants of complexes with Fe(III) and Cu(II) in aqueous medium

“…In all cases, the values of log β 11z diminish when passing from log β 111 to log β 115 . This fact was already observed and explained on the basis of charge effect [29,36]. The hydrolysis constants log β 11−1 for Fe(III) complexes are −0.53, −0.50, and −0.85 for L1, L2, and L3, respectively.…”

“…More recently, the study of intramolecular stacking interactions in ternary Cu(II) complexes formed with an heteroaromatic amine and 9-[2-(2-phosphonoethoxy)ethyl]adenine was published [24]. Chafaa et al [25,26] have reported the acidbase properties of a series of (o-hydroxyphenyl) methylenephosphonic acids synthesized by Vogt et al The stability constants of the complexes obtained from these ligands and bivalent transition metals cations [27,28] and a wide variety of lanthanide(III) cations and thorium(IV) were determined [29][30][31].…”

Physicochemical study of the hydrolysis of Rare-Earth elements (III) and thorium (IV)

“…This is necessary in order to determine the hydrolysis constants that are to be injected as fixed values for the calculation of the stability constants of the complexes of lanthanides (III) and of thorium (IV) cations with (phenolic) monoand dimethylenephosphonic acids [17,18] synthesised by Böhmer et al [19]. The treatment by Sirko-P [20] and Superquad [21] of the different titration curves corresponding to different lanthanides permitted the interpretation of this increase of H + ions concentration by the following hydrolysis equilibriums:…”

“…The titrating agent NaOH (1 or 0.1 mol dm -3 ) used was stored in a polyethylene container equipped with a CO 2 trap. All experiments were performed according to the method previously described [18].…”

Synthesis of New Benzylic Di-, Tri-, and Tetraphosphonic Acids as Potential Chelating Agents

“…15 Organo-phosphonic acids have been used as complexing agents due to their strong binding ability and the stability of the complexed species. [15][16][17][18][19][20][21][22] Recently calix [4]resorcinolarenes with phosphinoylalkyl substituents with acidic phosphonate fragments were shown to be efficient extracting agents of the metal ions of the lanthanum group from acidic solutions. 23,24 Structurally related derivatives, calix [4]arene methylenebisphosphonic acids, also displayed strong inhibition of calf intestine alkaline phosphatase.…”