Synthesis and Thermokinetic Studies of Co(II), Ni(II), Cu(II), Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) Complexes Derived from Bidentate Thiazole Schiff Base

 

S. R. Kelode1* and P. R. Mandlik2

1Department of Engg. Chemistry, Jagadambha College of Engineering and Tech. Yavatmal

2P. G. Department of Chemistry, Shri Shivaji Science College, Amravati

*Corresponding Author E-mail: sandeep_kelode@yahoo.co.in

 

 

ABSTRACT:

The new thiazole Schiff base have been synthesized by condensing 2-hydroxy-5-chloro acetophenone and 4-(p-hydroxyphenyl)-2-aminothiazole. The metal complexes were obtained as a result of interaction of Schiff base ligand and metal ions Co(II), Ni(II), Cu (II), Cr (III), Mn(III), Fe (III), VO (IV), Zr (IV) and UO2 (VI). The complexes have been characterized on the basis of elemental analysis, infrared, molar conductance, magnetic Susceptibilities, and theromogravimetric analysis. The kinetic analysis of the thermogravimetric data was performed by using Broido, Horowitz-Metzger and Freeman-Carroll method, which confirm first order kinetics and kinetic compensation effect.

 

KEY WORDS: Thiazole Schiff Base, Molar conductance, Thermal.

 


 

INTRODUCTION:

All type of Schiff base complexes have an important and popular area of research due to their simple synthesis, versality and diverse range of applications (Taylor and Relinski, 2004; Yamada, 1999). Schiff base and their metal complexes are becoming increasingly important in recent years due to their antiviral and biological activity1 The Schiff bases play a significant role in the area of coordination chemistry. The Schiff base prepared by using variety of aldehydes and amines possessed antitubercular, antitumer, anticancer, fungicidal medicinal and agrochemical activities2,3  Thermogravimetric in an easy, quick, precies measure method. The mathematical calculating thermogravimetric data, thermal decomposition activation parameters can be obtained4,5 This paper discusses the kinetic of the thermal decomposition and the accompanying compensation effect for Schiff base complexes of Co (II), Ni (II), Cu (II), Cr (III), Mn (III), Fe (III), VO (IV), Zr (IV) and UO2 (VI).

 

EXPERIMENTAL:

All the chemicals were of A.R. grade and used as received. 2-hydroxy-5-chloro acetophenone (HCA) and 4-(p-hydroxyphenyl)-2 amino thiazole was prepared by known methods6-9. The solvents were purified by standard methods10 Synthesis of 4-(p hydroxyphenyl)-2 amino thiazole

 

Synthesis of 2-hydroxy-5-chloro acetophenone 4-(p-hydroxyphenyl)-2 imino thiazole  [HCAT]:

A solution of 4-(p-hydroxyphenyl)-2 imino thiazole (0.02M) in 25ml of ethanol was added to an ethanolic solution(25ml) of 2-hydroxy-5-chloro 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 shown in Table 1. and m.p. It was also characterized by IR and 1H NMR spectral studies.

Yield:70%; m.p. 3100

 


 

Table1. Analytical data of the Ligands.

Ligand

Molecular Formula

Formula

Weight

Color and nature

Elemental Analysis

C% found (Cal.)

H% Found (Cal.)

N% Found (Cal.)

Cl% Found (Cal.)

S% Found (Cal.)

HCAT

C17H13N2O2SCl

344.6

Yellow

Crystalline

59.38

(59.19)

03.70

(03.77)

08.5

(08.12)

10.11

(10.30)

09.22 (09.31)

 

Table 2. Analytical data and molar conductance of the compounds.

Compounds

Colour

Mol.wt.

Analysis % Found  (calc.)

µeff

B.M.

LM (Ω-1 cm2mol-1)

M

C

H

N

Cl

[CoL2(H2O)2] H2O

Brown

800.1

7.25 (7.36)

50.86(50.99)

3.65 (3.74)

6.86

(6.99)

8.70(8.87)

4.48

6.9

[NiL2(H2O)2]

 H2O

Green

799.9

7.30 (7.33)

50.78(51.00)

3.68

(3.75)

6.95

(7.00)

8.72(8.87)

3.2

7.9

[CuL2(H2O)2] H2O

Brown

804.7

7.70 (7.89)

50.60(50.70)

3.65 (3.72)

6.82 (6.95)

8.72 (8.82)

1.70

8.3

[CrL2(H2O)Cl]H2O

Green

810.7

6.32 (6.41)

50.25(50.32)

3.36 (3.45)

6.81 (6.90)

13.08 (13.13)

3.96

18.9

[MnL2(OAc)] H2O

Brown

837.1

6.40(6.55)

51.51 51.60)

3.60 (3.70)

6.51

(6.68)

8.32 (8.48)

4.8

18.8

[FeL2(H2O)Cl] H2O

Black

814.6

6.72 (6.86)

50.01(50.08)

3.32 (3.43)

6.73

(6.87)

13.01 (13.07)

5.4

22.6

[VOL2]

Green

754.2

6.63 (6.76)

54.01(50.09)

3.05 (3.18)

7.33

(7.42)

9.32(9.41)

1.60

12.8

[ZrL2 (OH)2] 2H2O

Yellow

848.4

10.68(10.74)

47.93(48.09)

3.46(3.53)

6.52(6.60)

8.26(8.36)

Dia

11.7

[UO2L2]

Orange

957.3

24.73(24.87)

42.51(42.61)

2.41(2.50)

5.74(5.84)

7.32(7.41)

Dia

12.9

 


Preparation of complexes:

All the metal complexes were prepared in a similar way by following method. To a hot solution of ligand HCAT (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 4-6 h. The precipitated complexes were filtered, washed with ethanol followed by ether and dried over fused calcium chloride.

Yield : 45-50%

 

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 methods11

 

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  10-3M 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 100C min-1 heating rate. The molecular weights of the complexes were determined by Rast method are shown in Table 2.

 

RESULTS AND DISCUSSION:

The Schiff base ligand HCAT 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(10-3M) solution at room temperature (Table 2 ) shows all the complexes are non electrolytes11

 

The 1H NMR  spectra of ligand HCAT shows signals at δ 12.09, (1H, s phenolic OH ), δ 9.51 (1H, s, phenolic OH ), δ 7.55, 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)12-15 IR spectra of ligand and metal complexes  shows n(C=N) peaks at 1620cm- and absence of C=O peak at around 1700–1750 cm-1 indicates the Schiff base formation.16-19 IR spectra of complexes are shown in    Table 3.

 

Thermogravimetric studies:

An analysis of TG curves of HCAT and its metal complexes show that the Co(II), Ni(II), Cu(II), Cr(III), Mn(III), Fe(III) and Zr(IV) complexes decomposed in three stages, the ligand and UO2 (VI) complexes in two stages while VO(IV) complexes in one stage. The Co(II), Ni(II), Cu(II), Cr(III), Mn(III), Fe(III) and Zr(IV) complexes are stable upto 70oC Elimination of one water molecule from Co(II), Ni(II), Cu(II) Cr(III) and Fe(III) complexes upto 130oC have been observed (%wt loss obs./calcd. Co(II) : 2.44/2.24; Ni(II) : 2.56/2.25; Cu(II) : 2.46/2.23; Cr(III) : 2.32/2.22; Fe(III) : 4.58/4.30). The Mn(III) and Zr(IV) complexes shows percent loss corresponding to two water molecules (%wt loss obs./calcd. Mn(III) : 4.48/4.30; Zr(IV): 4.54/4.24) upto 150oC. In the Co(II), Ni(II) and Cu(II) complexes there is further loss in weight upto 220oC indicating the presence of two coordinated water molecule in each complex and in each Cr(III) and Fe(III) complexes further loss in weight upto 220oC indicating the presence of one coordinated water molecule (%wt loss obs./calcd. Co(II) : 4.57/4.49; Ni(II) : 4.59/4.50; Cu(II) : 4.58/4.47; Cr(III) : 2.38/2.22; Fe(III) : 2.47/2.33)20 There is no weight-loss upto 250oC in VO(IV) and UO2(IV) complexes indicating the absence of any water molecules (lattice or coordinated) in these complexes21 in all the complexes rapid weight-loss has been observed above 400oC, indicative of decomposition of  the free part of the coordinated ligand gradual weight-loss above 400oC corresponding to degradation of actual coordination part of the ligand. In the thermograms of ligand, Co(II), Ni(II), Cu(II), Fe(III) and VO(IV) complexes while in case of Mn(III), Zr(IV) and UO2(VI) complexes complete decomposition has not been observed upto 800°C. The half decomposition temperature and the basic parameter calculated for the compounds are tabulated in Table 4. The relative thermal stability on the basis of half decomposition temperature is found to be

UO2(VI)>Zr(IV)>Mn(III)>Cr(III)>Cu(II)>CO(II)>Fe(III)>VO(IV)>Ni(II)>HCAT

 

The Thermal activation energy (Table 4) was calculated by Freeman-Carroll,22 Horowitz-metzger23 and Broido24 method

 


 

Table 3. IR spectra of ligand and metal complexes.

Compound

n (OH) hydrogen bonded

n (C=N) imine

n (CO) phenolic

n (MO)

n (MN)

n (CS)

HCAT

3119

1620

1514

--

--

1122

[CoL2(H2O)2] H2O

--

1608

1504

470

430

1098

[NiL2(H2O)2] H2O

--

1585

1465

468

422

1090

[CuL2(H2O)2] H2O

--

1610

1504

509

410

1110

[CrL2(H2O)Cl] H2O

--

1590

1506

475

409

1115

[MnL2(OAc)] 2H2O

--

1562

1462

498

420

1090

[FeL2(H2O)Cl] H2O

--

1602

1504

512

440

1080

[VOL2]

--

1598

1506

514

445

1098

[ZrL2(OH)2] 2H2O

--

1600

1498

445

412

1108

[UO2L2]

--

1585

1440

550

480

1082

 

Table 4:  Thermal decomposition data of the complexes of HCAT

Compound

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***

HCAT (LH)

260.51

3.27

5.45

4.36

87.25

212.55

117.75

[CoL2 (H2O)2] H2O

433.50

5.73

9.55

9.55

191.11

208.24

156.67

[NiL2 (H2O)2] H2O

384.17

4.13

8.26

3.30

66.03

216.60

145.64

[CuL2 (H2O)2] H2O

494.86

11.28

11.28

10.16

203.31

208.54

170.28

[CrL2 (H2O)Cl] H2O

550.45

9.08

12.98

12.98

259.74

207.11

183.52

[MnL2 (OAc)] 2H2O

710.46

11.11

18.51

11.11

222.32

209.86

217.58

[FeL2 (H2O)Cl] H2O

429.25

3.77

9.44

8.49

169.89

209.30

155.47

[VOL2]

400.23

5.20

8.67

6.94

138.87

210.62

148.73

[ZrL2 (OH)2] 2H2O

711.17

7.41

18.54

11.12

222.52

209.77

217.65

[UO2L2]

800.00

19.85

22.06

17.65

353.20

206.79

239.62

* Broido, **Horowitz-Metzger and  ***Freemann-Carroll


 

CONCLUSION:

The thermal decomposition of the complexes is not simple and involves up to three stage decomposition. It is assumed that dehydration of the complexes containing water occurs within an active reaction interface. The compensation effect of thermal decomposition of the complexes indicating the change of sample mass on the estimated values of activation energy.

 

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Received on 16.09.2012        Modified on 03.10.2012

Accepted on 14.10.2012        © AJRC All right reserved

Asian J. Research Chem. 5(10): October, 2012; Page 1238-1241