Synthesis and Characterization with Antimicrobial activity of Cu(II), Ni(II) and Zn(II) metal complexes of Schiff base derived from o-aminophenol/ethylenediamine and Cinnamaldehyde

Rakesh Chandra Ray², Md. Kudrat-E-Zahan¹*, M.M. Haque¹, Md. Abdul Alim³,

Md. Moffaserul Alam², Md. Sher Ali², M.A. Mannan¹ and Md. Akhter Farooque¹

¹Department of Chemistry, Faculty of Science, University of Rajshahi, Rajshahi-6205, Bangladesh.

²Inorganic Research Laboratory, Department of Chemistry, University of Rajshahi, Rajshahi-6205, Bangladesh.

³Department of Analytical and Environmental Chemistry, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh.

*Corresponding Author E-mail: kudrat.chem@ru.ac.bd

ABSTRACT:

Transition metal complexes of Co(II), Cu(II), Ni(II) and Zn(II) Containing Bidentate Schiff base, derived from the condensation of ethylenediamine/o-aminophenol and cinnamaldehyde were synthesized and characterized by IR, UV- Vis., and some physical measurements. IR spectral studies show the binding sites of the Schiff base ligand with the metal ion. Molar conductance data and magnetic susceptibility measurements give evidence for monomeric and electrolytic nature of the complexes. The complexes have been found to have moderate antimicrobial activity against the tested bacteria.

KEYWORDS: Transition metal complex, Antimicrobial activity, Schiff base

INTRODUCTION:

Schiff bases are condensation products of primary amines with carbonyl compounds and they were first reported by Hugo Schiff in 1864. These compounds containing a general formula RHC=N-R’ where R and R’ are alkyl, aryl, cyclo alkyl or heterocyclic groups are also known as anils, imines or azomethines [1]. Several studies showed that the presence of a lone pair of electrons in sp² hybridized orbital of nitrogen atom of the azomethine group is of considerable chemical and biological importance. Because of the relative easiness of preparation, synthetic flexibility, and the special property of C=N group, Schiff bases are generally excellent chelating agents, especially when a functional group like –OH or –SH is present close to the azomethine group so as to form a five or six membered ring with the metal ion [2,3].

Schiff bases are well known for their biological applications as antibacterial, antifungal, anticancer and antiviral agents [4, 5]. Also, Schiff base metal complexes have been widely studied because they have industrial, antifungal, antibacterial, anticancer herbicidal applications, [6] antitubercular activities [7] and chelating abilities which give it attracted remarkable attention.[8].

Recently, we studied few mixed ligand complexes containing heterocyclic amine as secondary ligands and few Schiff base containing complexes [9-18]. In the present work, transition metal complexes of Cu(II), Ni(II) and Zn(II) containing bidentate Schiff base, derived from the condensation of ethylenediamine/o-aminophenol and cinnamaldehyde were synthesized, characterized and also studied their antibacterial properties.

2. EXPERIMENTAL:

2.1 Reagents and Chemicals

All the reagents used were of analar or chemically pure grade. Solvents were purified and dried according to standard procedures.

2.2 Physical Measurements

The melting or decomposition temperatures of all the prepared metal complexes were observed in an electro thermal melting point apparatus model No.AZ6512. The SHERWOOD SCIENTIFIC Magnetic Susceptibility Balance was used for the present investigation. Infrared spectra as KBr disc were recorded in a SIMADZU FTIR-8400 (Japan) infrared spectrophotometer, from 4000-400 cm^-1. The absorbances of the complexes were recorded on SHIMUDZU Spectrophotometer.

3. General method for the preparation of the complexes

Preparation of [Cu(C₁₁H₁₄N₂) (C₁₅H₁₂NO)]NO₃: 0.120g (2 mmol) of ethylenediamine, 0.218g (2 mmol) o-aminophenol and 0.529 g (4 mmol) of cinamaldehyde were dissolved in 10 mL of ethanol separately. The solution of ethylenediamine, o-aminophenol and cinamaldehyde were mixed. Then the mixed solution was poured in the canonical flask containing 0.483 g (2 mmol) of Cu(NO₃)₂.3H₂O ethanol solution and stirred for 4 hours at ambient temperature and allowed to stand for half an hour. A brown precipitate was filtrate off and dried in a vacuum desiccator over anhydrous CaCl₂. Ni(II) and Zn(II) metal complexes were prepared following the same procedure as stated above.

4. RESULTS AND DISCUSSION:

4.1. Physical Properties

The conductance values of the complexes are shown in the Table-1. All three complexes are electrolytic in nature. The structural assignment of the complexes were based on the elemental analysis which are in good agreement with the proposed structures (Figure 1).

4.2. IR spectra

Selected Infrared spectral data of the complexes are shown in the Table-2. The spectral data of the complexes showed a strong absorption band at (1580-1620) cm^-1 due to ν (C=N) stretching. Band at (3045-3065) cm^-1 is due to aromatic ν(C-H) stretching. The band at (740-800) cm^-1 is due to ν (M-N) stretching which indicated the coordination through N atom to the metal. Band at (460-500) cm^-1 is due to ν (M-O) stretching, which indicated the formations of complexes have taken place to the metal through the deprotonated O atom of OH moiety. A band at (3300-3500) cm^-1 is due to ν (N-H) stretching of ν (NH₂) modes.

4.3. Magnetic moment and electronic spectra.

Significant UV-visible spectral bands of the complexes in dimethyl sulfoxide (DMSO) have presented in the Table-1. The observed absorption bands in the region 200-400 nm are due to the charge transfer. The observed magnetic moment of the complexes at room temperature is also given in Table -1. The magnetic moment values of the complexes indicated that these complexes are paramagnetic except Zn(II) metal complex which is diamagnetic. It appears from the magnetic moment data that all synthesized complexes are of high spin (except Zn(II) metal complex which is in low spin) with tetrahedral geometry.

Figure-1. Tetrahedral structure of complexes. Here, M = Cu(II), Ni(II) and Zn(II)

Therefore, on the basis of the elemental analysis, magnetic moment, conductance measurements, IR spectra, UV-visible spectra and other physical properties, the suggested structures of the complexes are tetrahedral as shown in Figure-1.

Table-1: Physical properties of the complexes.

Complexes	Colour	Melting point (±5°C)	% Yield	Molar conductance (ohm^-2cm²mol^-1)	µ_eff (B.M)
[Cu(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	Brown	204 (d)	65	46	2.00
[Zn(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	Yellow	220 (d)	66	79	dia
[Ni(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	Greenish Yellow	300 (above)	63	70	2.93

Table-2: Selected infrared spectral bands of the complexes.

Complexes	ν(C=N) (cm^-1)	ν(C-H) aromatic (cm^-1)	ν (NH₂) (cm^-1)	ν (M-O) (cm^-1)	ν (M-N) (cm^-1)
[Cu(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	1617	3051	3437	485	742
[Zn(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	1620	3057	3444	480	742
[Ni(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃	1618	3059	3441	460	743

Table-3: antibacterial activity of the complexes.

Bacteria	Gram Staining	Diameter of zone inhibition (in mm)
Bacteria	Gram Staining	[Cu(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO_{3 (}mg/disc)	[Zn(C₁₁H₁₄N₂)₂(C₁₅H₁₂NO]NO₃ mg/disc	K- 30 mg/disc
Bacillus subtilis	Positive	09	10	28
Staptococcus aureus	Positive	10	08	31
Streptococcus -b-haemolyticus	Positive	11	10	25
Escherichia coli	Negative	12	12	29
Shigella dysenteriae	Negative	12	13	31
Shigella sonnei	Negative	10	10	28

5. Antibacterial Activity of the Metal Complexes

The microorganisms adsorb metal ions on their cell walls and as a result respiration processes of cells are disturbed and protein synthesis is blocked which is the requirement for further growth of organisms. The growth inhibition effects of metal ions are considerable. The susceptibility of microorganism to antimicrobial agents can be determined in vitro by a number of methods. The disc diffusion technique is widely acceptable for preliminary investigations of compounds, which are suspected to possess antimicrobial properties. Antimicrobial activities of the test samples are expressed by measuring the zone of inhibition observed around the area.

The present results revealed that the complexes are more microbial toxic than the free metal ions or ligands. The Schiff base complexes (Table 3) showed moderate activity against both Gram positive and Gram negative bacteria compared to standard Kanamycine.

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Received on 07.06.2015 Modified on 17.06.2015

Asian J. Research Chem. 8(9): September 2015; Page 571-573

DOI: 10.5958/0974-4150.2015.00091.7