Preparation, spectral, X-ray powder diffraction and computational studies and genotoxic properties of new azo–azomethine metal chelates
Abstract
A new tridentate azo–azomethine ligand, N′-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, (sbH·H2O) (1), is prepared by condensation of benzohydrazide and 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde (a) with treatment of a solution of diazonium salt of p-nitroaniline and 2-hydroxybenzaldehyde in EtOH. The five coordination compounds, [Co(sb)2]·4H2O (2), [Ni(sb)2]·H2O (3), [Cu(sb)2]·4H2O (4), [Zn(sb)2]·H2O (5) and [Cd(sb)2]·H2O (6) are prepared by reacting the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with the ligand. The structures of the compounds are elucidated from the elemental analyses data and spectroscopic studies. It is found the ligand acts as a tridentate bending through phenolic and carbonyl oxygens and nitrogen atom of the C
N
group similar to the most of salicylaldimines. Comparison of the infrared spectra of the ligand and its metal complexes confirm that azo-Schiff base behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor sequence. Upon complexation with the ligand, the Cd(II), and Zn(II) ions form monoclinic structures, while Co(II), Cu(II) and Ni(II) ions form orthorhombic structures. Quantum chemical calculations are performed on tautomers and its metal chelates by using DFT/B3LYP method. Most stable tautomer is determined as tautomer (1a). The geometrical parameters of its metal chelates are obtained as theoretically. The NLO properties of tautomer (1a) and its metal complexes are investigated. Finally, the ligand and its metal complexes are assessed for their genotoxicity.
Graphical abstract
Introduction
Azo-Schiff bases play an important role in inorganic chemistry as they easily form stable complexes with most transition metal ions such as cobalt(II), nickel(II) and copper(II). The development of the field of bioinorganic chemistry has increased the interest in Schiff base complexes, since it has been recognized that many of these complexes may serve as models for biologically important species [1], [2], [3]. Schiff base ligands are well known for their wide range of applications in pharmaceutical and industrial fields [4], [5], [6]. Transition metal complexes of polydentate Schiff base ligand have great applicabilities in catalysis and material chemistry [7]. Moreover, the hydrazone group plays an important role for the antimicrobial activity and possesses interesting antibacterial, antifungal [8], [9], anti-tuberculosis activities [10], [11]. These groups of compounds are important class of ligands which present in numerous physiological and biological applications as antitumour agents, insecticides, anticoagulants, anticonvulsant, anti-inflammatory, analgesic, antioxidants, antiplatelet and plant growth regulators [12], [13], [14], [15], [16]. These properties of the hydrazones are attributed to the formation of stable metal complexes with some metals which catalyze physiological processes. Their metal complexes, have also found applications in various chemical processes like nonlinear optics, sensors, medicine [17].
Recently, azo-Schiff bases and their metal complexes were reported by our group [18], [19], [20]. In view of the versatile importance of azo–azomethines, hydrazones and their metal complexes, we herein describe the preparation and identification of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal complexes of N’-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, sbH. The chemical equations concerning the formation of the sbH ligand represented as Scheme 1. The newly synthesized azo–azomethine ligand and its metal chelates were characterized by their IR, electronic, and elemental analyses data. Finally, the ligand sbH and its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal complexes were tested for their genotoxic properties.
Section snippets
Reagents
All reagents and solvents used were supplied by Merck chemical company and were used without further purification.
Physical measurements
1H NMR spectrum of the ligand was obtained in deuterated DMSO as solvent on a Bruker FT-NMR AC-400 (300 MHz) spectrometer. All chemical shifts are reported in δ (ppm) relative to the tetramethylsilane as internal standard. Carbon, hydrogen and nitrogen elemental analyses were performed with a model LECO CHNS 932 elemental analyzer. IR spectra were obtained using KBr discs (4000–400 cm
Synthesis
The results of the elemental analyses of the ligand and its complexes are in agreement with the chemical formulae. The azo-Schiff base ligand N’-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, sbH·H2O was synthesized in good yields in EtOH. The ligand is stable at room temperature and soluble in common organic solvents such as DMSO, DMF, EtOH and MeOH. The complexes are also stable at room temperature. Based on the elemental analyses, spectroscopic
Conclusion
In this work, azo (NN) and nitro (NO2) chromophore groups containing azo–azomethine ligand, N’-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl} methylidene]benzohydrazidemonohydrate, (sbH·H2O) derived from 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde with benzohydrazide in EtOH and its some transition metal chelates have been synthesized. The analytical data and the spectroscopic studies suggested that the complexes had general formula of [M(sb)2]⋅nH2O, where M is cobalt(II), nickel(II),
Acknowledgement
This work was financially supported by the Unit of Coordination of Scientific Research Projects, Kahramanmaraş Sütçü Imam University, Kahramanmaraş, Turkey (Project no: 2010/2-15YLS). Also, the authors wish to thank Prof. Dr. Vickie McKee, Department of Chemistry at Lougbrough University, Leichester, UK for 1H NMR measurements.
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