Synthesis, Spectroscopic Monitoring and Biological Activities of N₂O₄ Schiff base Ligand containing Metal Complexes of Cd(II), Pd(II), Hg(II) and Zr(IV)

Md. Anarul Islam¹, Roksana Khatun¹, Md. Monirul Islam¹ and Md. Kudrat-E-Zahan²*

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

²Associate Professor, Dept. of Chemistry, Faculty of Science, Rajshahi University, Rajshahi-6205, Bangladesh.

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

ABSTRACT:

Cd(II), Pd(II), Hg(II) and Zr(IV) complexes of bis(indoline-2-one)triethyelenetetramine which is made from isatin and triethylenetetramine were prepared and characterized by physical properties, spectral and magnetic methods. Based on the analytical results, electronic and infrared spectral data and magnetic susceptibility measurements, suitable structures have been proposed. The formation of the complexes were monitored by UV-Vis spectroscopy. The antimicrobial results indicate that the cadmium complex exhibit more activity than the palladium (II), mercury and zirconium (II) complexes.

KEY WORDS: Transition metal complex, spectra, Antimicrobial activity, Schiff base.

1. INTRODUCTION:

Isatin and its derivatives are special members in the Schiff base family. The simple isatin based Schiff base compounds having, acyl, aroyl and heteroacroyl Schiff bases have addi- tional donor sites >C=O, >C=N-, etc. These donor sites make them more flexible and versatile. This versatility has made them good chelating agents that can form a variety of complexes with various transition and inner transition metals and has attracted the attention of many researchers [1]. Moreover, Schiff bases are regarded as privileged ligands [2]. Due to their capability to form complexes with different transition metals can act as catalysts for many different reactions [3, 4].

Recently, complexes of type, [ML]Cl(2) [M=Co(II), Ni(II), Cu(II) and Zn(II)] were reported [5]. Where, the Schiff base ligand bis(indoline-2-one)triethylenetetramine (L) obtained from condensation of triethylenetetramine and isatin. Furthermore, Isatin based complexes show variety of biological activities such as potentiation of pentabarbitone induce nercosis [6], anti-inflammatory [7], anti-convulsant [8], analgesic [9], anti-bacterial [10], anti-fungal [11], and anti-depressant [12].

Earlier, we studied electronic properties of nickel(II) complexes in solution [13-15]. In this study, we are motivated to undertake a systematic study of preparation, characterization and spectroscopic monitoring of transition metal complexes formed with bis(indoline-2-one) triethyelenetetramine (L) and Cd(II), Pd(II), Hg(II) and Zr(IV) ions.

2. EXPERIMENTAL:

2.1 Measurements and materials

Electronic spectra were recorded on a Thermoelectron Nicolet evolution 300 UV-Vis spectrophotometer. All chemicals were commercial products and were used as supplied.

2.2 Synthesis of bis(indoline-2-one) triethylenetetramine

To a stirring solution of isatin (0.294g, 2 mmol) dissolved in 25ml of ethanol, a solution of triethylenetetramine (0.16ml,1mmol) in 10ml ethanol was added drop wise. This has resulted a dark orange solution, which was refluxed for 6h.The reaction mixture was cooled and kept for evaporation at room temperature leading to isolation of solid product. The product thus formed was filtered washed several times with ethanol and finally with diethyl ether. The product was found to be soluble in DMF and DMSO.

2.3 Preparation of Complexes

1 mmol solution of a metal chloride/ nitrate (where, M = Cd(II), Zr(II), Pd(II), and Hg(II) metal ions) dissolved in ethanol (15 ml) was taken in a two necked round bottom flask and kept on magnetic stirring. To this solutions of isatin (0.294 g, 2 mmol) dissolved in 25 ml of ethanol and triethylenetetramine (0.16 ml, 1 mmol) in ethanol (10 ml) were simultaneously added Drop wise followed by refluxing for about (6-10 h) leading to isolation of microcrystalline product. The complexes thus formed were filtered and washed several times with ethanol to remove any traces of unreacted starting materials and were further washed with diethyl ether and dried in vacuum over anhydrous CaCl₂. The complexes were soluble in DMF and DMSO.

3. RESULTS AND DISCUSSION:

During the course of the reactions Schiff base ligand bis(indoline-2-one)triethyelenetetramine were first formed which the coordinated with cadmium(II), palladium (II), murcurry(II) and zirconium (IV) metal ions. The reactions of metal complexes may be represented as follows:

MX₂ + L → [M(L)(X)₂]

Where, L = H₂₄C₂₂N₆O₂ [bis(indoline-2-one) triethyelenetriamine and X = Cl/(NO)₂

3.1 Physical properties of the complexes

Some physical properties of the complexes are shown in the (Table 1). The molar conductance values are in the region range 10 to 16 Ω^‑1_cm²_mol^-1_.These values are lower than expected for an electrolyte. So molar conductance values indicate that the complexes are non-electrolyte in nature. The melting point ranges from 180-232.

3.2 Magnetic moment

The observed values of effective moment (µ_eff) of the complexes at room temperature are given in (Table 1). All the complexes are paramagnetic except [ZrL] (NO₃)₂complex which is diamagnetic in nature.

3.3 Electronic spectral studies

The observed d-d transitions of the complexes are given in Table-2. In addition to d→d transitions, the complexes obtained charge transfer band. The result is consistent with the result of Al-Resayes et. al.[5].

3.4 Infrared spectra

IR spectral data are shown in (Table 3). The strong bands obtained at 3450, 1706 and 1620 cm^-1 due to ʋ(-NH), ʋ(C=O) and ʋ(C=N) respectively. The presence of metal ligand bonding is evident from the appearance of ʋ(M-O), ʋ(M-N) and ʋ(M-N)(-NH) at 700, 600 and 500 cm^-1 respectively in the spectra of the complexes.

Table 1: Physical properties of complexes

No.	Complexes	Molar conductance (ohm^-1cm²mol^-1)	Magnetic moment (B.M)	Melting point (±0.5°c)	Colour
1.	[CdL]Cl₂	10.64	8.24	232	Red
2.	[ZrL](NO₃)₂	12.46	dia	180	Red
3.	[PdL] (NO₃)₂	16.12	1.45	205	Black
4.	[HgL]Cl₂	10.60	1.29	220	Brown

Where, L=H₂₄C₂₂N₆O₂

Figure 1: Electronic spectral change for Cd complex formation (left) and time dependencies of the absorbance for the solution at 520 nm (o). Conditions: Measured for 5 hours at one hour interval.

Table 2: Major IR spectral data (cm^-1) with their assignment and electronic spectral data of the Schiff base complexes

No.	Complexes	ʋ(-NH) cm^-1	ʋ(C=O) cm^-1	ʋ(C=N) cm^-1	ʋ(M-O) cm^-1	ʋ(M-N)(-NH) cm^-1	ʋ(M-N) cm^-1	d→d (λ/nm)
1.	[CdL]Cl₂	3457	1708	1616	617	567	497	530
2.	[ZrL](NO₃)₂	3413	1706	1621	758	651	488	527
3.	[PdL] (NO₃)₂	3468	1706	1627	674	647	579	---
4.	[HgL]Cl₂	3435	1706	1631	685	541	494	401

Where, L=H₂₄C₂₂N₆O₂

Table 3: Antibacterial activity of complexes and standard Kanamycin

No.	Complexes	Zone of inhibition, diameter in mm
No.	Complexes	*Escherichia coli*	*Pseudomonas aeruginosa*	*Staphylococcus Aureus*	*Salmonella typhi*	*Salmonella choleresuls*
1	[CdL]Cl₂	0	0	21	11	0
2	[ZrL](NO₃)₂	0	0	0	0	0
3	[PdL] (NO₃)₂	13	11	0	14	0
4	[HgL]Cl₂	20	22	14	15	20
5	DMSO(control)	-	-	-	-	-
6	Kanamycine(30 µg)	20	22	21	21	20

Where, L=H₂₄C₂₂N₆O₂

3.5 Reaction of Cd(II) metal ion with Schiff base ligand bis(indoline-2-one)triethyelenetetramine monitored by electronic spectra

The reaction of Cd(II) with Schiff base ligand bis(indoline-2-one)triethyelenetetramine was monitored by electronic spectra as follows. An ethanol solution of Cd(II)chloride was taken in a two necked round bottom flask and kept on magnetic stirring. To this ethanol solutions of isatin (0.294 g, 2 mmol) and triethylenetetramine (0.16 ml, 1 mmol) were simultaneously added drop wise. The absorption spectra of the resulting solution were measured for 5 hours at 1h hours interval (Figure 1). A new absorption band formed at 520 nm which corresponds to formation of [CdL]Cl₂ complex.

4. ANTIBACTERIAL SCREENING:

As the test bacteria are pathogenic, all steps of the work were done with high precaution and aseptic conditions. This antibacterial activity test was carried out at microbiology laboratory, Pharmacy Department, Rajshahi University. The investigations of antibacterial activity were performed by disc diffusion method and isolated antibiotics were used for this purpose. The antibiotic was dissolved in DMSO and concentration (100 µ/disc) was used make a better correleation of the antibacterial activity. Kanamycin (30 µ/disc) was used as a standard. The antibacterial activity of the tested sample was determined by measuring the zone of inhibition in term of mm and was compared to that of the standard, kanamycin. The results are given in Table 3.

5. CYTOTOXICITY:

All the complexes did not showed any toxicity against A salina nauplii and T. castaneum. . So these complexes may be used as chelation therapy. Specially, these non toxic complexes will be a very interesting topics for further study.

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Received on 03.12.2013 Modified on 05.01.2014

Asian J. Research Chem. 7(2): February 2014; Page 163-165