title: The complexation of AlIII, PbII, and CuII metal ions by esculetin: a spectroscopic and theoretical approach.
abstract: UV-visible absorption spectroscopy combined with quantum chemical calculations and, notably, Time-Dependent Density Functional Theory were used to probe the structure of metal complexes with esculetin in dilute aqueous solution, at pH = 5. For the 1:1 complex formation, the studied metal ions can be classified according to their complexing power: aluminum(III) > copper(II) > lead(II). For the three complexes, a chelate is formed with the fully deprotonated catechol moiety and an absorption band is observed at the same wavelength. In all cases, a pronounced ionic character is calculated for metal-ligand bonds. However, the complexes differ in their coordination sphere. Copper and lead are bound to two water molecules leading to a square plane geometry and a hemidirected complex, respectively, whereas aluminum atom has an octahedral environment involving three water molecules and a hydroxide ion. For Al(III) only, a 2:1 complex is observed, and the involvement of an aluminum dimer was evidenced.
authors.affiliation: LASIR, CNRS UMR8516, Université Lille 1 Sciences et Technologies , Bât C5 - 59 655 Villeneuve d'Ascq Cedex - France.
authors.forename: Annaïg
authors.initials: A
authors.lastname: Le Person
authors.forename: Aurélien
authors.initials: A
authors.lastname: Moncomble
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Cornard
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007854:Lead / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D014468:Umbelliferones / Q000737:chemistry*
chemical_list: D007477:Ions; D009942:Organometallic Compounds; D014468:Umbelliferones; D007854:Lead; D003300:Copper; D000535:Aluminum; C007628:esculetin