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Complex formation of copper(II), nickel(II) and zinc(II) with ethyl phosphonohydroxamic acid: solution speciation, synthesis and structural characterization

Abstract

The first example of Cu(II) 12-MC-4 hydroxamic metallacrown, containing an ethylphosphonate group as an additional donor function in the β-position with respect to the hydroxamic group, is described. The solution equilibria of ethylphosphonoacetohydroxamic acid (PAHEt) with Cu(II) was investigated in aqueous solution by a combination of potentiometry, UV-Vis and EPR spectroscopies, mass spectrometry and isothermal titration calorimetry. The model containing mononuclear, [CuL], [CuL2]2- and [CuL(LH-1)]3- and pentanuclear, [Cu5(LH-1)4]2- species is proposed. The compound corresponding to the pentameric metallacrown complex was isolated in the solid state, as {Na4(H2O)6(Ac)[Cu5(PAHEt-3H)4(Ac)]}2·3H2O (1), whose crystal structure was determined by X-Ray analysis. The centrosymmetric decanuclear complex anion of (1) consists of two pentanuclear 12-MC-4 fragments formed by five Cu(II) ions and four triply deprotonated residues of the phosphonohydroxamate ligand, and is associated with eight sodium cations, two acetate anions and twelve water molecules taking part in sodium cations coordination, as well as solvate water molecules. Stability of MCs under conditions of competitive complex formation as well as their reactivity with respect to strong chelating agents – dipy was examined, and as a result mixed-ligand mononuclear unit {[Cu(dipy)(PAHEt–2H)]}n·2nH2O (2) was formed. In addition the chelating capacity of this ligand toward Ni(II) and Zn(II) ions was studied in solution.

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Publication details

The article was received on 06 Mar 2019, accepted on 14 May 2019 and first published on 14 May 2019


Article type: Paper
DOI: 10.1039/C9NJ01175G
New J. Chem., 2019, Accepted Manuscript

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    Complex formation of copper(II), nickel(II) and zinc(II) with ethyl phosphonohydroxamic acid: solution speciation, synthesis and structural characterization

    M. Ostrowska, I. A. Golenya, M. Haukka, I. Fritsky and E. Gumienna-Kontecka, New J. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C9NJ01175G

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