Synthesis and Characterization of Polydentate Schiff-Base Ligands and Their Complexes

Abstract

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.

Polymer-anchoring Schiff base ligands and their metal complexes: Investigation of their electrochemical, photoluminescence, thermal and catalytic properties

“…These bands are observed for the complexes at lower or higher wavenumbers by ca. 10-45 cm -1 relative to the free ligands suggesting involvement of the oxygen atom of the C-O moiety in coordination(Demirelli et al, 2006). In all of the present complexes, a medium and/or weakbands observed in the 548-535 and 453-438 cm -1 range can be attributed to the ν(M-O) and ν(M-N) (Tumer M., 2007) modes, respectively.…”

Crystal structure, spectroscopic and redox behaviour of novel imidazolidine ligand

“…This yield was a normal value for the Schiff base ligand. The low molar conductance value (experimental section) of 1 Â 10 À3 M solution in methanol showed to be nonelectrolytes [22]. From the methanol solution, we obtained suitable single crystals for X-ray diffraction analysis.…”

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

“…In the solid state, salicylaldimine Schiff bases tend to form (NAEAEAEH-O) or (N-HAEAEAEO) types of hydrogen bonding, respectively. In many cases in solution, both types of hydrogen bonds have been observed indicating phenol-imine, O-HAEAEAEN, keto-amine, OAEAEAEH-N tautomerism [18,19]. Knowing the structures of free Schiff bases in solution and in the solid state is important in view of the intramolecular hydrogen bonding and comparison with the struc- ture of Schiff base complexes.…”