title: Spectrometric study of tautomeric and protonation equilibria of o-vanillin Schiff base derivatives and their complexes with Cu(II).
abstract: Electronic absorption and emission properties of a series of Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde and 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, or 3-aminomethylpyridine were studied in solvents of different polarities. The interconversion of the enolimine to the ketoamine tautomeric form was observed for compound 1, 6-methoxy-2-(3-pyridylmethyliminomethyl)phenol, and the corresponding equilibrium constant was estimated in several solvents. Protonation constants of all the investigated compounds were determined spectrophotometrically in the methanol/water 1/4 system. The effect of copper(II) ions on absorption and on the emission spectra of these ligands was examined in the buffered dioxane/water 1/1 system (pH 5.8). Strong complexation of Cu(II) and formation of a 1:1 complex were observed for the bis-Schiff base derived from 2,3-diaminopyridine. The complex of copper(II) with compound 1 was isolated and characterized by elemental analysis, magnetic susceptibility measurement, UV-vis and IR spectrometry.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia. ngalic@chem.pmf.hr
authors.forename: Nives
authors.initials: N
authors.lastname: Galić
authors.forename: Zvjezdana
authors.initials: Z
authors.lastname: Cimerman
authors.forename: Vladislav
authors.initials: V
authors.lastname: Tomisić
mesh_terms: D001547:Benzaldehydes / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000379:methods; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D019800:Phenol / Q000737:chemistry; D011522:Protons; D012545:Schiff Bases / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D001547:Benzaldehydes; D007477:Ions; D011522:Protons; D012545:Schiff Bases; D012997:Solvents; D014867:Water; D019800:Phenol; D003300:Copper; C100058:vanillin; D000432:Methanol