title: Pentacopper(II) 12-metallacrown-4 complexes with alpha- and beta-aminohydroxamic acids in aqueous solution: a reinvestigation.
abstract: A reinvestigation of the equilibria of (S)-alpha-alaninehydroxamic acid (alpha-Alaha) and (R)-aspartic-beta-hydroxamic acid (Asp-beta-ha) with copper(II) was performed in aqueous solution in order to clarify some contradictory literature reports regarding the stoichiometry of the polynuclear complexes formed. beta-Alaninehydroxamic acid (beta-Alaha, HL), for which the formation of a planar 12-metallacrown-4, [Cu(5)L(4)H(-4)](2+), was already reported, was also re-examined for comparison. Among the different techniques used (potentiometry, absorption spectrophotometry, spectropolarimetry and electrospray ionization mass spectrometry), ES data allowed to define unambiguously that all these three ligands form the same pentanuclear species. Therefore it can be concluded that in aqueous solution the hydroxamates of both alpha- and beta-amino acids form 12-metallacrown-4 complexes, and that the formers are less stable.
authors.affiliation: Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università di Parma, Parco Area delle Scienze 17A, I-43100 Parma, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Careri
authors.forename: Francesco
authors.initials: F
authors.lastname: Dallavalle
authors.forename: Matteo
authors.initials: M
authors.lastname: Tegoni
authors.forename: Ingrid
authors.initials: I
authors.lastname: Zagnoni
mesh_terms: D000409:Alanine / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry; D000998:Antiviral Agents / Q000737:chemistry; D001216:Asparagine / Q000031:analogs & derivatives* / Q000737:chemistry; D001665:Binding Sites; D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry; D006877:Hydroxamic Acids / Q000737:chemistry*; D015394:Molecular Structure; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization; D013057:Spectrum Analysis
chemical_list: D000970:Antineoplastic Agents; D000998:Antiviral Agents; D006877:Hydroxamic Acids; D012996:Solutions; C024848:beta-aspartylhydroxamic acid; D001216:Asparagine; D003300:Copper; D000409:Alanine