title: Complexation models of N-(2-carboxyethyl)chitosans with copper(II) ions.
abstract: The copper(II) complex formation equilibria of N-(2-carboxyethyl)chitosans with three different degrees of substitution (DS = 0.42, 0.92, and 1.61) were studied in aqueous solution by pH-potentiometric and UV-spectrophotometric techniques. It was demonstrated that the complexation model of CE-chitosans depends on DS: the [Cu(Glc-NR(2))(2)] complexes are predominant for two lower substituted samples ("bridge model", log beta(12) = 10.06 and 11.6, respectively), whereas the increase of DS leads to formation mainly of the [Cu(Glc-NR(2))] complexes ("pendant model", log beta(11) = 6.41). As a model for copper complexation with a disubstituted residue of CE-chitosan, the complex of N-methyliminodipropionate [CuMidp(H(2)O)].(H(2)O) was synthesized and structurally characterized by XRD. The unit cell consists of two crystallographically nonequivalent Cu atoms having slightly distorted square pyramidal coordination; Midp constitutes the basal plane of the pyramid and acts as a tetradentate NO(3) chelate-bridging ligand by the formation of two six-membered chelate rings (average Cu-O 1.99 A, Cu-N 2.04 A) and a bridge via carbonyl O atom (average Cu-O 1.99 A), an apical position is occupied by a water molecule (average Cu-Ow 2.30 A).
authors.affiliation: LAQUIPAI, Departamento de Química, Faculdade de Ciêncas, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal. yury_skorik@mail.ru
authors.forename: Yury A
authors.initials: YA
authors.lastname: Skorik
authors.forename: Carlos A R
authors.initials: CA
authors.lastname: Gomes
authors.forename: Nina V
authors.initials: NV
authors.lastname: Podberezskaya
authors.forename: Galina V
authors.initials: GV
authors.lastname: Romanenko
authors.forename: Luiz F
authors.initials: LF
authors.lastname: Pinto
authors.forename: Yury G
authors.initials: YG
authors.lastname: Yatluk
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D048271:Chitosan / Q000031:analogs & derivatives* / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009942:Organometallic Compounds / Q000737:chemistry*; D011199:Potentiometry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D009942:Organometallic Compounds; D003300:Copper; D048271:Chitosan