Schiff base ligands HL 1 -HL 6 have been prepared from the reaction of 2,6-diformyl-4-t-butylphenol and 2,6-diformyl-4-methylphenol with various aromatic amines in ethanolic solution. The Schiff base ligands 2,2¢-dipyridine (dp) mixed-ligand Cu II complexes have been obtained. Mixed-ligand Cu II complexes containing the dp ligand have ionic nature and they conduct the electricity in solution media. The complexes have been obtained in two different forms: one of them is [Cu 2 (L n )Cl 3 ] (n: 1, 2, 3, 4, 5 and 6) and other complexes have the general formula [Cu 2 (L n )(dp) 2 ]3Cl. Ligands and their complexes have been characterized by elemental analyses, FT-IR, electronic spectra, molar conductance, 1 H( 13 C)-n.m.r. and mass spectral data. Their stoichiometric protonation constants have been determined potentiometrically in dioxan using a combined pH electrode at 25°C, under a nitrogen atmosphere. For the calculation of the protonation constants, PKAS computer programme has been used. The effects of the substituents on the protonation constants and the additivities of these effects are discussed. The antimicrobial activity studies of the ligands and their complexes have been studied against the Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcuc faecalis, bacteria and Saccoramyces cerevisia, yeast. The catalytic properties of the complexes have been studied on the ascorbic acid, catechol and 2,6-di-t-butylphenol substrates. Thermal behaviour of the complexes has been studied by thermal techniques.
In this study, we synthesized the amine compounds 2-{(E)-[(2-aminoethyl)imino]methyl}phenol (H3A) and 2-{(E)-[(3-aminopropyl)imino]methyl}-6-methoxyphenol (H3B) as the starting materials. From reactions of the starting materials with 2-hydroxy-5-methylisophthalaldehyde, phthalaldehyde, and 2-hydroxy-5-t-butylisophthalaldehyde, we prepared the new ligands H3L1–H3L3 and H2L. The Cu(II) and Cd(II) complexes of the ligands have been obtained. Microanalytical data, magnetic moment, 1H(13C) NMR, mass spectra, FT-IR, and conductivity measurements have been used to explain the structures of the ligands and their complexes. The protonation constants of the ligands H3L1–H3L3 have been studied in a 1:1 molar ratio (M:L). Protonation and stability constants of the Schiff bases and their Cu(II) and Cd(II) complexes have been determined by the potentiometric titration method in 50% dioxane–water media at 25.00 ± 0.02 °C under a nitrogen atmosphere and ionic strength of 0.1 M NaClO4. The ligands H3L1–H3L3 have seven protonation constants. In other words, the ligand H2L has six protonation constants. The variation of protonation constants of these compounds were interpreted on the basis of structural effects exposed by the substituents.
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