Tetradentate schiff base ligands of 3,4- diaminobenzophenone: Synthesis, characterization and thermodynamics of complex formation with Ni(II), Cu(II) and Zn(II) metal ions

Abstract

Some new symmetrical diimino tetradentate Schiff base ligands were synthesized by the reaction of 3,4-diaminobenzophenone with salicylaldehyde derivatives, such as [3,4-bis(((2-hydroxy-4-methoxyphenyl)methylene)amino)phenyl]phenylmethanone (L 1 ), [3,4-bis(((2-hydroxy-5-methoxyphenyl)methylene)amino)phenyl]phenylmethanone (L 2 ), [3,4-bis(((5-bromo-2-hydroxyphenyl)methylene)amino)phenyl]phenylmethanone (L 3 ) and [3,4-bis(((2-hydroxy--5-nitrophenyl)methylene)amino)phenyl]phenylmethanone (L 4 ). Additionally, a tetradentate Schiff base ligand [3,4-bis(((2-hydroxy-3-methoxyphenyl)methylene)amino)phenyl]phenylmethanone (L 5 ) was synthesized. All the Schiff bases and their Ni(II), Cu(II) and Zn(II) complexes were characterized using elemental analysis and infrared, electronic, mass and 1 H-NMR spectroscopy. The formation constants of the complexes were measured using UV-Vis spectroscopic titration at constant ionic strength 0.10 M (NaClO 4 ), at 25 °C in dimethylformamide (DMF) as solvent. 64ASADI, SEPEHRPOUR and MOHAMMADI veral metal chelates of the ONNO donor class of Schiff bases were studied as oxygen carrier and they were found to be useful models for bioinorganic processes. 6,7 Schiff bases are effective inhibitors and could be adsorbed on the surface of metals. 8 Symmetric tetradentate Schiff base complexes have been extensively used as macrocycle models. 9 These compounds have received considerable attention because of their potential use as catalysts, 10-14 and their antibacterial, 5,15,16 antifungal, 17 antitumour 18,19 and herbicidal activities. 20 The main goals of this study were the synthesis and characterization of some new tetradentate Schiff bases and their complexation with Ni(II), Cu(II) and Zn(II) metals. These compounds were characterized by elemental analysis, and FT-IR, 1 H-NMR, mass and UV-Vis techniques. In addition, the formation constants, K f , were determined spectrophotometrically and the free energy changes, ΔG , at 25 °C, were calculated for the complexes. The effects of the electronic and steric nature of substituents on the Schiff base type ligands on the formation constants and free energy changes resulting from complex formation were studied.

Symmetrical and Unsymmetrical Schiff Bases Derived from 3,4-Diaminobenzophenone: Synthesis and Thermodynamics of Five Coordinated Tertiaryphosphine Cobalt(III) Complexes

“…[20,22,23,25,26] For our unsymmetrical Schiff bases, the O-H protons of the phenolic groups appear at different chemical shifts. The azomethine protons of the Schiff bases and their complexes almost appear at same place.…”

“…By comparing the FTIR spectra of symmetrical and unsymmetrical Schiff base ligands and their complexes, it is noted that there is not noticeable difference between FTIR spectra of the symmetrical and unsymmetrical compounds. [20,22,23,25,26] The Electronic Spectra All the cobalt(III) complexes show two bands in the range of 370-500 nm, which are attributed to d  π* transition. The band at lower energy is attributable to d  π* transition associated with azomethine chromophore and the band at higher energy arised from d  π* transition within the phenyl rings.…”

“…[22,23] The cobalt(III) Schiff base complexes shown in Scheme 1, were prepared by the methods described in the literature. [24] To a refluxing solution of the tetradentate ligands (1 mmol), in 25 mL mixed solvent methanol / chloroform (15 / 10) under N2 atmosphere, was added a solution of Co(OAc)2 × 4H2O (0.25 g, 1 mmol) in methanol (5 mL).…”

Synthesis and Antibacterial Activity of Isatin Schiff Base Derivative with 3-Aminoacetophenone and its Ni(II), Co(II) Transition Metals Complexes

“…The chemistry of Schiff base ligands species has been gaining considerable interest primarily because of their fascinating structural diversities (Asadi, et al, 2011;Monfared, et al, 2011;Chamayou, et al, 2011). The electrophilic carbon atoms of aldehydes and ketones can be targets of nucleophilic attack by amines.…”

Synthesis, characterization, electrical and catalytic studies of some coordination compounds derived from unsymmetrical Schiff base ligand

“…During the past decades, considerable attention has been paid to the chemistry of the metal complexes of with symmetrical Schiff base ligands containing N and other donors atoms. However, very little information is available for metal complexes of unsymmetrical Schiff base ligands [6][7][8][9]. Unsymmetrical Schiff base ligands derived from substituted carbohydrazide have played an important part in revealing the preferred coordination geometries of metal complexes and have valuable importance in the coordination chemistry due to their preparative accessibility and structural variability.…”