Thermal and Microbial Evolution of Co(II), Ni(II), Cu(II) and Zn(II) Metal Complexes derived from thiazole Schiff base
S. R. Kelode
Department of Engg. Chemistry, Jagadambha College of Engineering and Technology, Yavatmal
*Corresponding Author E-mail: sandeep_kelode@yahoo.co.in
ABSTRACT:
A new series of Schiff base ligand was derived from the condensation of 2-hydroxy-5-chloro-3-nitro acetophenone and thiazole. The Schiff bases behaved as charge bidentade ligand. The ligand was characterized by elemental analysis and spectral methods. The coordinating ability of the ligand is investigated by preparing its metal complexes with Co(II), Ni(II), Cu(II) and Zn(II) have been prepared and characterized by elemental analysis, conductance measurements, molecular weight determinations, spectral and thermal studies. The Schiff base and their metal complexes have been evaluated for their antibacterial activities The synthesized products are coloured solids, soluble in DMF, DMSO and THF.
KEYWORDS: Schiff base, Magnetic susceptibility, Thermal.
INTRODUCTION:
Schiff’s bases, widely used as analytical reactants and have been studied for chemistry.1,2 Schiff bases metal complexes have many applications in different fields. The Schiff bases derived from thiazole and substituted acetophenone have been widely used as ligand for the synthesis of transition metal complexes. Thiazole Schiff base ligands and their metal complexes are biologically active3 and are known for their biological application4 i.e. one of the drug in cytotoxicity of anticancer5. Due to biological potency, pharmacological properties and synthetic flexibility of thiazole Schiff bases. The aim of present investigation is to synthesize various transition metal complexes of Schiff base derived from 2-hydroxy-5-chloro-3-nitro acetophenone and 2-amino-4-phenylthiazole.
EXPERIMENTAL:
All the chemicals were of A.R. grade and used as received. 2-hydroxy-5-chloro-3-nitro acetophenone (HCNA) and 2-amino-4-phenylthiazole was prepared by known methods6-9. The solvents were purified by standard methods10.
Synthesis of 2-amino-4-phenylthiazole:
Synthesis of 2-amino-4-phenylthiazole
The synthesis of 2-amino-4-phenylthiazole prepared by known method7-9. The product was filtered and crystallized from 70% ethanol, after several minutes the golden coloured product of 2-amino-4-phenylthiazole was separated out.
Yield: 9g (75%); m.p.: 148-1500C
IR Spectrum: υ, cm-1 3420, 3240(NH2, Two bands); 3170(CH of C3HNS); 3100 (CH of C6H5); 420, 1500, 1575 (C=C of C6H5); 1460(C=N)
Synthesis of 2-hydroxy-5-chloro-3-nitroacetophenone 4-phenyl-2 imino thiazole [HCNAT]:
A solution of 4-phenyl-2 imino thiazole (0.02M) in 25ml of ethanol was added to an ethanolic solution(25ml) of 2-hydroxy-5-chloro-3-nitro acetophenone (0.02M) and the reaction mixture was refluxed on a water bath for 4h. After cooling a pale yellow coloured crystalline solid was separated out. It was filtered and washed with ethanol, crystallized from DMF and dried under reduced pressure at ambient temperature. The purity of ligand was checked by elemental analysis and m.p. It was also characterized by IR and 1H NMR spectral studies. Yield:75%; m.p. 3050C
Table1. Analytical data of the Ligands.
|
Ligand |
Molecular Formula |
Formula Weight |
Color and nature |
Elemental Analysis |
|||
|
C% found (Cal.) |
H% Found (Cal.) |
Cl% Found (Cal.) |
S% Found (Cal.) |
||||
|
HCNAT |
C17H12N3O3SCl |
373.06 |
Yellow Crystalline |
52.35 (52.20) |
03.20 (03.34) |
9.22 (9.38) |
08.34 (08.46) |
Table 2. Analytical data and molar conductance of the compounds.
|
Ligand |
Formula weight g mole-1 |
Colour |
Elemental Analysis Found (Calcd.) |
µeff
B.M |
LM (Ω-1 cm2 mol-1) |
|||
|
M% |
C% |
H% |
Cl% |
|||||
|
[CoL2(H2O)2] H2O |
858.1 |
Brown |
6.20 |
44.80 |
3.30 |
7.60 |
4.2 |
6.4 |
|
|
|
|
(6.55) |
(45.67) |
(3.41) |
(7.85) |
|
|
|
[NiL2(H2O)2] H2O |
857.9 |
Green |
6.35 |
45.53 |
3.10 |
7.78 |
3.5 |
7.2 |
|
|
|
|
(6.63) |
(45.69) |
(3.30) |
(7.99) |
|
|
|
[CuL2(H2O)2] H2O |
862.7 |
Brown |
6.95 |
45.30 |
3.18 |
7.80 |
1.3 |
8.5 |
|
|
|
|
(7.12) |
(45.55) |
(3.40) |
(7.98) |
|
|
|
[ZnL2 (OH)2] 2H2O |
914.6 |
Yellow |
9.40 |
43.10 |
3.02 |
7.22 |
Dia |
14.4 |
|
|
|
|
(9.60) |
(43.35) |
(3.16) |
(7.50) |
|
|
Preparation of complexes:
All the metal complexes were prepared in a similar way by following method. To a hot solution of ligand HCNAT (0.02M) in 25ml of ethanol a suspension of respective metal salts was added drop wise with constant stirring. The reaction mixture was refluxed on a water bath for 3-5 h. The precipitated complexes were filtered, washed with ethanol followed by ether and dried over fused calcium chloride. Yield : 55-60%
The complexes are soluble in DMSO and DMF but insoluble in water and common organic solvents. The metal chloride content of complexes were analyzed by standard methods12 The 1H NMR spectra of ligand was recorded and obtained from RSIC Chandigarh. IR spectra of the compounds were recorded on Perkin Elmer 842 spectrophotometer in the region 400-4000cm-1, Carbon, Hydrogen and Nitrogen analysis were carried out at RSIC, Punjab University, Chandigarh. The molar conductance of the complexes at 10-3 M dilution in DMF were determined using equiptronic digital conductivity meter EQ-660 with a cell constant 1.00 cm-1 at room temperature. The magnetic moment measurement were made on a Gouy balance at room temperature using [HgCo(SCN)4] as the calibrant. The thermogravimetric analysis were performed on laboratory set up apparatus in air atmosphere at 100 C min-1 heating rate. The molecular weights of the complexes were determined by Rast method.
RESULT AND DISCUSSION:
The Schiff base HCNAT and its complexes have been characterized on the basis of 1H NMR, IR spectral data, elemental analysis, molar conductance, magnetic succeptibility measurements and thermogravimetric analysis data . All these values and analytical data is consistent with proposed molecular formula of ligand . All the compounds are coloured solid and stable in air. They are insoluble in water but soluble in coordinating solvents like DMF and DMSO. The molar conductance values in DMF(10-3 M) solution at room temperature (Table2 ) shows all the complexes are non electrolytes.
The 1H NMR spectra of ligand HCNAT shows signals at δ 12.14,(1H, s phenolic OH), δ 7.56, 7.54, 7.53 and 7.52 (4H, m, phenyl) δ 6.81, 6.80, and 6.78(3H, s Phenyl), 6.68 (1H s thiophene), and 2.56(3H, s, methyl) 11,13-15.
IR spectra of ligand and metal complexes shows n(C=N) peaks at 1622 cm-1 and absence of C=O peak at around 1700 – 1750 cm-1 indicates the Schiff base formation16-19.
Thermogravimetric studies:
Thermogravimetric study indicates all the complexes are stable up to 60-700C. All the complexes shows half decomposition temperature(Table-4). The Thermal activation energy was calculated by Freeman-Carroll,20 Horowitz-metzger21 and Broido22 method.
Table 3. IR spectra of ligand and metal complexes
|
Compound |
n (OH) hydrogen bonded |
n (C=N) imine |
n (CO) phenolic |
n (MO) |
n (MN) |
n (CS) |
|
HCNAT (LH) |
3080 |
1622 |
1516 |
-- |
-- |
1126 |
|
[CoL2(H2O)2] H2O |
-- |
1605 |
1502 |
471 |
430 |
1090 |
|
[NiL2(H2O)2] H2O |
-- |
1581 |
1465 |
464 |
421 |
1095 |
|
[CuL2(H2O)2] H2O |
-- |
1612 |
1501 |
501 |
418 |
1115 |
|
[ZnL2(OH)2] 2H2O |
-- |
1610 |
1492 |
442 |
412 |
1104 |
Table 4. Thermal decomposition data of HCNAT and its complexes.
|
Compounds |
Half Decomposition Temperature(oC) |
Activation Energy (kJ mole-1) |
Frequency Factor Z(sec-1) |
Entropy Change -∆S (J mol-1 K-1) |
Free Energy Change ∆F (kJ mol-1) |
||
|
B* |
H-M** |
F-C*** |
|||||
|
HCNAT (LH) |
265.50 |
3.24 |
4.45 |
4.32 |
87.20 |
210.55 |
115.75 |
|
[CoL2 (H2O)2] H2O |
400.20 |
5.20 |
8.67 |
6.94 |
138.87 |
210.62 |
148.73 |
|
[NiL2 (H2O)2] H2O |
389.16 |
6.71 |
8.39 |
6.71 |
134.27 |
210.76 |
146.26 |
|
[CuL2 (H2O)2] H2O |
428.51 |
6.59 |
8.48 |
7.53 |
150.68 |
210.29 |
155.05 |
|
[ZnL2 (OH)2] 2H2O |
710.42 |
11.11 |
18.51 |
11.11 |
222.32 |
209.86 |
217.58 |
Table 5. Antimicrobial activity23-25
|
Ligand and its Complexes |
Zone of inhibition (in mm) |
||||||
|
B.subtilis (mm) |
P.vulgaris (mm) |
S.aureus (mm) |
E.coli (mm) |
P.fluorescen (mm) |
A.aerogenes (mm) |
B.megatherium (mm) |
|
|
HCNAT Co- HCNAT Ni- HCNAT Cu- HCNAT Zn- HCNAT |
R S 11 R S 12 S 8 |
R R R S 11 R |
R R R S 12 S 13 |
S 12 S 11 S 13 S 13 S 10 |
R S 14 R S 12 S 11 |
S 8 R S 11 R S 8 |
R R S 11 S 12 R |
S-Sensitive (Bacteriocidal); R-Resistant (Bacteriostatic)
Antimicrobial activity
The inhibition effect of the ligand and its metal complexes on the growth of various bacteria is summarized in table 5. The compounds are found to show low bacteriociadal behavior against most of the bacterial culture and are resistance towards the other. In general the results reveal that the activity of the ligand was found to enhance on complexation with metal.
CONCLUSIONS:
In conclusion, we have synthesized new ligand 2-hydroxy-5-chloro-3-nitro acetophenone 4-phenyl-2 imino thiazole and their metal complexes. Ligand was found to bind the metal ion monobasic (ON) bidentate manner. The Schiff bases ligand and their metal complexes shows more activity towards E.coli and least activity towards P.vulgaris. The structural changes have marked effect on the sensitivity and sensitivity varies with organisms.
ACKNOWLEDGMENT:
The author is greatly thankful to RSIC., Chandigarh for recording the 1H-NMR and IR spectra. And greatly thankful to VNIT., Nagpur for recording TGA.
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Received on 10.07.2013 Modified on 12.07.2013
Accepted on 16.07.2013 © AJRC All right reserved
Asian J. Research Chem. 6(8): August 2013; Page 713-715