Synthesis, characterization and antimicrobial studies on transition ...

Research article 

Int J Pharm Biomed Sci 2011, 2(4), 108-113 

ISSN No: 0976-5263 

Research Drops 

PharmaInterScience Publishers 

<strong>Synthesis</strong>, <strong>characterization</strong> <strong>and</strong> <strong>antimicrobial</strong> <strong>studies</strong> on transition 

metal complexes of n-[phenyl(methylphenyl-5-pyrazolyl)methylidene] 

aniline 

S. Sunitha 1 *, 

K.K. Aravindakshan 2 

1 Department of Chemistry, National 

College (Autonomous), Tiruchirappalli, 

Tamil Nadu-620 001, India 

2 Department of Chemistry, University of 

Calicut, Kerala-673 635, India 

*Correspondence: 

Dr. S. Sunitha 

Tel: 0431 3202971 

Fax: 0431 2481997 

E-mail: sunitha.sree47@gmail.com 

The novel Schiff base N-phenyl(methylphenyl-5-pyrazolyl)methylidene]aniline 

was synthesised in three stages. Ethylacetoacetate <strong>and</strong> phenylhydrazine were 

allowed to react together to form 3-methyl-1-phenyl-5-pyrazolone. This was 

benzoylated at the 4- position to get 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone. 

This was condensed with aniline to get the novel Schiff base. Though there are four 

potential ligating sites, only two of the ligating sites are involved in coordination. 

The lig<strong>and</strong> was characterised by IR <strong>and</strong> 1 H NMR spectra. Co(II), Ni(II) <strong>and</strong> Cu(II) 

complexes of the neutral bidentate chelating Schiff base lig<strong>and</strong> were synthesized 

using acetates, chlorides <strong>and</strong> nitrates of the metals. They were characterised by 

elemental analysis, conductance <strong>and</strong> magnetic susceptibility measurements, UV- 

VIS <strong>and</strong> IR spectra. The lig<strong>and</strong> exhibited tautomerism <strong>and</strong> the complexes were 

found to have octahedral geometry. The in vitro antibacterial activity against 

Escherichia coli <strong>and</strong> in vitro antifungal activity against Aspergillus niger of the 

lig<strong>and</strong> <strong>and</strong> the complexes were investigated using nutrient agar medium. 

Key words: Schiff base, Aspergillus niger, Metal complexes, IR spectral analysis, 

Antimicrobial activity 

Received: 17 Nov 2011 / Revised: 04 Dec 2011 / Accepted: 06 Dec 2011 / Online publication: 28 Dec 2011 

1. INTRODUCTION 

Pyrazole-5-one <strong>and</strong> its derivatives are not only 

biologically active but also find applications in photography 

<strong>and</strong> dye industry [1]. 4-acyl-3-methyl-1-phenyl-5-pyrazolone 

has been used to extract Mn(II)[2]. 5-pyrazolones possess 

various biological activities. In view of ligational behaviour 

<strong>and</strong> biological importance [3,4] of 5-pyrazolones <strong>and</strong> its 

derivatives the chelating Schiff base lig<strong>and</strong> derived from 4- 

benzoyl-3-methyl-1-phenyl-5-pyrazolone <strong>and</strong> aniline has 

been synthesized <strong>and</strong> characterised. A perusal of the 

literature revealed that no work has been done on the 

transition metal complexes of the Schiff base derived from 

aniline <strong>and</strong> 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone. The 

Co(II), Ni(II) <strong>and</strong> Cu(II) complexes of this lig<strong>and</strong> using 

acetates, chlorides <strong>and</strong> nitrates of the metals were synthesized 

<strong>and</strong> characterized. The lig<strong>and</strong> N-phenyl(methylphenyl-5- 

pyrazolyl)methylidene]aniline (L) (Fig.1) has three donor 

sites, azomethine nitrogen, the pyrazolone ring oxygen <strong>and</strong> 

the pyrazolone ring nitrogen atoms. It is capable of exhibiting 

tautomerism (Fig.2). 

O 

CH 3 

N 

N 

O 

N 

Fig.1. N-phenyl(methylphenyl-5-pyrazolyl)methylidene]aniline (L) 

CH 3 

CH 3 

CH 3 

NH 

N 

N 

N 

HO N 

H O N 

Fig.2. Tautomerism in the lig<strong>and</strong> 

©2011 PharmaInterScience Publishers. All rights reserved. www.pharmainterscience.com

S. Sunitha <strong>and</strong> K.K. Aravindakshan, Int J Pharm Biomed Sci 2011, 2(4), 103-113 

109 

2. MATERIALS AND METHODS 

All chemicals used in the present work viz.,aniline, 

benzoylchloride, ethylacetoacetate, phenylhydrazine, 

isoniazid, metal salts, solvents etc., were of AR grade. (BDH, 

Sarabhai, Qualigens, E. Merck, Loba Chemie or Glaxo). 

Carbon, hydrogen <strong>and</strong> nitrogen analyses were carried out 

by using VarioEL III CHNS analyser at SAIF, CUSAT, 

Kochi. The anions present in the complexes were estimated 

by st<strong>and</strong>ard methods. The 1 H NMR spectrum of the lig<strong>and</strong> 

was recorded on Advance III 500 MHz Bruker spectrometer 

using DMSO-d 6 as solvent. Infrared spectra were measured in 

the range 4000-400 cm -1 as KBr pellets on a Perkin-Elmer 

spectrophotometer. The solid-state electronic spectra of the 

complexes were recorded on a JASCO UV-Visible 

spectrophotometer. The magnetic measurements were made 

at room temperature by Evans method using Hg[Co(CNS) 4 ] 

as calibrant. 

2.1 <strong>Synthesis</strong> of the compounds 

The synthesis of the lig<strong>and</strong> consisted of three stages. The 

first stage which involves the preparation of 3-methyl-1- 

phenyl-5-pyrazolone[5] <strong>and</strong> the second stage which involves 

the benzoylation of the above to 4-benzoyl-3-methyl-1- 

phenyl-5-pyrazolone were carried out using Jensen’s 

procedure [6]. The third stage involved the condensation of 

4-benzoyl-3-methyl-1-phenyl-5-pyrazolone with distilled 

aniline to prepare the Schiff base lig<strong>and</strong>. Added an ethanolic 

solution of aniline (0.0109 mol, 1mL) to a hot refluxing 

solution of 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone(0.01 

mol, 2.7840 g) in ethanol <strong>and</strong> refluxed for 3 h .The lemon 

yellow coloured crystals obtained on cooling were filtered at 

the pump, washed with ethanol <strong>and</strong> dried (yield= 65.8%). 

Complexes of Co(II) with this lig<strong>and</strong> were synthesized 

using iodide <strong>and</strong> nitrate salts of the metal. Complexes of 

Ni(II) with this lig<strong>and</strong> were synthesized using acetate salt of 

the metal. Complexes of Cu(II) of this lig<strong>and</strong> were 

synthesized using acetate, chloride, nitrate <strong>and</strong> sulphate salts 

of the metal. Solutions of the lig<strong>and</strong> <strong>and</strong> iodide <strong>and</strong> nitrate 

salts of Co(II) salts in methanol (2:1 molar ratio) were 

refluxed for 0.5h. Acetate of Ni(II)salt, nitrate <strong>and</strong> sulphate 

salts of Cu(II) were dissolved in water <strong>and</strong> added to the 

refluxing solution of the lig<strong>and</strong> in methanol (1:2 molar ratio) 

<strong>and</strong> refluxed for 2h. Acetate of Cu(II) was dissolved in 

ethanol <strong>and</strong> added to a refluxing solution of methanol(1:2 

molar ratio) <strong>and</strong> refluxed for 15 min. The chloride of Cu(II) 

was dissolved in methanol <strong>and</strong> added to refluxing solution of 

the lig<strong>and</strong> in methanol (1:2 molar ratio) <strong>and</strong> refluxed for 7.5h. 

The complexes formed on cooling were filtered off, washed 

with the respective solvents <strong>and</strong> dried except the complex 

synthesized using the chloride of Cu(II) in which case the 

volume was reduced to half by evaporating off the solvent. 

The solid which separated was filtered off, washed with the 

solvent <strong>and</strong> dried. 

3. RESULTS AND DISCUSSION 

3.1 Characterization of the lig<strong>and</strong> 

The lig<strong>and</strong> was characterized by m.p., elemental 

analysis, 1 H NMR <strong>and</strong> IR spectral data. The 1 H NMR 

spectrum of the lig<strong>and</strong> was recorded in DMSO-d 6 <strong>and</strong> it 

showed a number of characteristic signals of the compound 

[7,8]. The singlet observed at 1.4 ∂ was assigned to the 

methyl group at 3 position of the pyrazolone ring. The 

multiplet observed in the range 7.0-7.5 ∂ was assigned to the 

aromatic protons. The singlet at 8.0 ∂ was assigned to the 

proton at 4 position of the pyrazolone ring. Singlets at 2.4 ∂ 

<strong>and</strong> 3.4 ∂ are due to DMSO-d 6 <strong>and</strong> H 2 O. The IR spectrum of 

the lig<strong>and</strong> showed a number of absorption b<strong>and</strong>s which were 

characteristic of the different groups present in it [7,8]. The 

b<strong>and</strong>s present at 1628 cm -1 <strong>and</strong> at 1226 cm -1 have been 

assigned to >C=N <strong>and</strong> C-N stretching vibrations, 

respectively. The characteristic frequency due to the 

stretching of the aromatic keto group, at 1650 cm -1 was not 

present in the spectrum, which indicated that condensation 

between 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone <strong>and</strong> 

aniline was complete. The b<strong>and</strong> at 1500 cm -1 has been 

assigned to >C=O group of the pyrazolone ring. The b<strong>and</strong>s 

due to the in plane bending of the aromatic C-H stretching 

are usually found in the range 1250-950 cm -1 . The b<strong>and</strong>s at 

1138 cm -1 , 1007 cm -1 <strong>and</strong> 906 cm -1 have been assigned to 

these modes of vibrations. The most characteristic 

frequencies of aromatic groups were found below 900 cm -1 , 

usually in the range 600-900cm -1 , due to the out-of-plane 

bending vibration of the aromatic C-H. The b<strong>and</strong>s at 770cm -1 , 

760 cm -1 <strong>and</strong> 698 cm -1 have been assigned to these modes of 

vibrations. The elemental analysis <strong>and</strong> spectral data for L are 

consistent with the formula C 23 H 19 N 3 O. 

3.2 Formulae <strong>and</strong> general properties of complexes 

The reaction of the lig<strong>and</strong> (L) with different salts of 

Co(II), Ni(II) <strong>and</strong> Cu(II) ions in 2:1 molar ratios gave metal 

complexes of the given formulae, as evidenced by the microanalytical 

<strong>and</strong> spectral data. 

1. [ML 2 X 2 ]where M=Co(II), Ni(II) or Cu(II) <strong>and</strong> 

X=CH 3 COO - , I - or NO 3 

- 

2. [Cu(L) 2 SO 4 ] 

Suggested structure for [ML 2 X 2 ] <strong>and</strong> [Cu(L) 2 SO 4 ] are 

shown in Fig.3 <strong>and</strong> Fig.4, respectively. The colours, magnetic 

susceptibilities, molar conductivities <strong>and</strong> melting points <strong>and</strong> 

the micro-analytical data of the complexes are listed in 

Table 1. These air-stable metal complexes were nonhygroscopic, 

partially soluble in most of the organic solvents 

but freely soluble in DMF <strong>and</strong> DMSO. The molar 

conductivities in DMF/DMSO (10 -3 M) showed that all the 

complexes behaved as non-electrolytes, indicating the 

coordinated nature of the anions. 



110 

Table 1 

Formulae, general properties <strong>and</strong> micro analytical data of lig<strong>and</strong> <strong>and</strong> complexes 

Sl. No. Compound Colour Yield % MP (°C) µ eff (B.M.) Ω m 

Microanalytical data found (calculated) % 

(ohm -1 cm 2 mol -1 ) Metal C H N Anion 

1 C23H19N3O(L) Lemon yellow 66 162 - 77.01 

(78.19) 

2 [Co(L) 2 I 2 ] Brown 42 >300 4.84 10.75 5.65 55.26 

(5.78) (54.17) 

3 [Co(L) 2 (NO 3 ) 2 ] Brown 42 >300 3.10 0.0 6.60 64.09 

(6.63) (62.10) 

4 [Ni(L) 2 (CH 3 COO) 2 ] Pale green 40 >300 3.14 10.75 6.60 66.74 

(6.65) (67.97) 

5 [Ni(L) 2 (CH 3 COO) 2 ] Black 53 >300 1.96 0 7.10 68.14 

(7.16) (67.60) 

6 [Cu(L) 2 Cl 2 ] Green 52 >300 2.02 30.23 7.49 66.74 

(7.56) (65.67) 

7 [Cu(L) 2 (NO 3 ) 2 ] Green 51 >300 2.27 0.0 7.05 62.12 

(7.11) (61.78) 

8 [Cu(L) 2 SO 4 ] Green 50 >300 1.51 10.75 7.29 65.16 

(7.34) (63.77) 

5.25 

(5.38) 

3.70 

(3.73) 

4.25 

(4.27) 

4.30 

(4.98) 

4.98 

(4.96) 

4.99 

(4.52) 

4.20 

(4.25) 

5.11 

(4.39) 

11.80 

(11.89) 

8.21 

(8.24) 

14.38 

(14.40) 

9.95 

(9.52) 

9.48 

(9.46) 

10.25 

(9.99) 

12.57 

(12.53) 

10.07 

(9.70) 

- 

- 

- 

- 

- 

8.50 

(8.45) 

- 

- 

N 

C H 3 

N 

O 

N 

X 

M 

X 

N 

O 

N 

N 

CH 3 

Fig.3 Suggested structure for [ML 2 X 2 ], where M=Co(II), Ni(II) or Cu(II) 

<strong>and</strong> X=CH 3 COO - , I - or NO 3 

- 

C H 3 

N 

N 

O 

N 

O 

O 

S 

Cu 

O 

O 

O 

N 

N 

N 

CH 3 

1560-1531 cm -1 <strong>and</strong> were assigned to the coordinated 

azomethine groups present in them. 

In addition to these, new b<strong>and</strong>s were present in the lower 

frequency region of the spectra of all these complexes. These 

b<strong>and</strong>s appeared in the range 665-650 <strong>and</strong> at 585 cm -1 in the 

spectra of the Co(II) complex, at 685 <strong>and</strong> 585 cm -1 in the 

spectrum of the Ni(II) complex <strong>and</strong> in the ranges 685-679 

<strong>and</strong> 607-580 cm -1 in the Cu(II) complexes. The first one was 

assigned to the stretching vibrations of the M-N bonds <strong>and</strong> 

the second one to that of the M-O bonds formed during 

complexation. The M-O bond is due to coordinated nitrate or 

acetate anion or due to coordinated oxygen atom of the 5- 

pyrazolone ring of the lig<strong>and</strong>. 

The absence of sharp b<strong>and</strong>s in the region 3441-3060 cm -1 

in the spectra of all the complexes <strong>and</strong> the lig<strong>and</strong> indicates 

that N-H group is not present in the lig<strong>and</strong> <strong>and</strong> in the 

complexes. The absence of a broad b<strong>and</strong> in this region is an 

indication of the absence of coordinated water as well. 

Elemental analyses also corresponded to the absence of 

coordinated water in the complexes. 

3.4 Coordination of anions 

Fig.4. Suggested structure for [Cu(L) 2 SO 4 ] 

3.3 IR spectra of complexes 

Table 2 lists the most important IR spectral b<strong>and</strong>s of the 

lig<strong>and</strong> <strong>and</strong> metal complexes. All the complexes showed 

downshift in the characteristic absorption frequency of the 

azomethine group thus indicating that the nitrogen atom of 

the azomethine group is coordinated to the metal. The b<strong>and</strong> at 

1628 cm -1 observed in the spectrum of the lig<strong>and</strong> was absent 

in all the complexes. Instead, b<strong>and</strong>s appeared in the ranges of 

Two strong b<strong>and</strong>s at 1632 <strong>and</strong> 1376 cm -1 observed in the 

IR spectra of the acetato complex of Ni(II) <strong>and</strong> two strong 

b<strong>and</strong>s at 1640 <strong>and</strong> 1360 cm -1 in the spectra of the acetato 

Cu(II) complex were assigned to υ(C=O) <strong>and</strong> υ(C—O), 

respectively. Since the separation between the two υ(CO) is 

much larger than that in the free ion, we conclude that the 

acetate ion coordinates to the nickel(II) ion <strong>and</strong> copper(II) in 

an unidentate fashion [9]. 

The absence of b<strong>and</strong>s at 2700-2500 cm -1 indicates that the 

complex is an O- isomer. This is also confirmed by the 

presence of M-O bond[10]. Microanalytical data <strong>and</strong> the nonconducting 

nature of these complexes supported this. A b<strong>and</strong> 

of medium intensity was observed at 330 cm -1 in the spectra 



111 

Table 2 

Significant IR spectral b<strong>and</strong>s of lig<strong>and</strong> <strong>and</strong> Co(II), Ni(II) <strong>and</strong> Cu(II) complexes 

Compounds Assignments <strong>and</strong> b<strong>and</strong> frequencies (cm -1 ) 

υ C=N υ C =O υ COO - asy υ COO-sym 

2- 

υ SO 4 

coordinated 

υ M-N υ M-O υ M-X 

-- 

υ NO 3 

coordinated 

BMPPA (L) - - - 

[Co(L) 2 I 2 ] 1570 m a ,sh b 1460 s c - - - 650 m,sh 585 w,sh 330 m,sh - 

[Co(L) 2 (NO 3 ) 2 ] 1570 m,sh 1460 s,sh - - - 665 m,sh 585 w d ,sh - 1460 s,sh 

1360 s,sh 

1010 w,sh 

[Ni(L) 2 (CH 3 COO) 2 ] 1531 s,sh 1460 s,sh 1632 sh 1376 m,sh - 685 m,sh 585 w,sh - - 

[Cu(L) 2 (CH 3 COO) 2 ] 1550 s,sh 1460 s,sh 1640 s 1360 m,sh - 680 m,sh 590 w - - 

[Cu(L) 2 Cl 2 ] 1580 s,sh 1460 s,sh - - - 680 m,sh 580 m 366 m,sh - 

[Cu(L) 2 (NO 3 ) 2 ] 1550 s,sh 1460 s,sh - - - 685 m,sh 580 w - 1450 s,sh 

1360 s,sh 

1010 w,sh 

[Cu(L)2SO4] 1610 s,sh 1432 s,sh - - 1210s,sh 679 s,sh 607 m,sh - 

1142 s,sh 

1008 s,sh 

a = medium; b = sharp; c = strong d = weak 

Table 3 

Electronic spectral b<strong>and</strong>s of complexes <strong>and</strong> their assignments 

No. Compound B<strong>and</strong>s(nm) Assignment Geometry 

1 [Co(L) 2 I 2 ] 694 

4 T 1g (F)→ 4 T 2g (F) 

Distorted octahedral 

593 

525 

4 T 1g (F)→ 4 A 2g 

T 1g (F)→ 4 T 1g (P) 

2 [Co(L) 2 (NO 3 ) 2 ] 820 

690 

530 

4 T 1g (F)→ 4 T 2g (F) 

T 1g (F)→ 4 A 2g (F) 

T 1g (F)→ 4 T 1g (P) 

Octahedral 

3 [Ni(L) 2 (CH 3 COO) 2 ] 770 

740 

440 

4 [Cu(L) 2 (CH 3 COO) 2 ] 680 

398 

5 [Cu(L) 2 Cl 2 ] 548 

493 

6 [Cu(L) 2 (NO 3 ) 2 ] 686 

306 

7 [Cu(L)2SO4] 650 

525 

3 A 2g → 3 T 2g 

3 A 2g → 3 T 1g (F) 

3 A 2g → 3 T 1g (P) 

Octahedral 

2 E g → 2 E g Distorted octahedral 

2 E g → 2 T 2g 

Charge transfer 

2 E g → 2 E g 


2Eg→2Eg 





Table 4 

Antimicrobial activity study on E. Coli 

Compound Zone of inhibition (mm) at 

different concentrations (μg/L) 

Minimum inhibition 

concentration (μg/L) 

0.5 1.0 1.5 2.0 

L NI a NI NI NI NI 

[Ni(L) 2 (CH 3 COO) 2 ] NI 0.7 0.7 0.8 1.0 

[Cu(L 1 ) 2 Cl 2 ] 1.7 1.9 2.3 2.4 0.5 

[Cu(L1)2SO4] 1.2 1.7 1.9 2.0 0.5 

a = no inhibition 

Table 5 

Antifungal activity study on Aspergillus niger 

Compound 

Zone of inhibition (mm) 

L 11 

[Co(L) 2 I 2 ] 14 

[Ni(L) 2 (CH 3 COO) 2 ] 10 

[Cu(L) 2 CH 3 COO) 2 ] 15 

[Cu(L) 2 Cl 2 ] 13 

[Cu(L)2(NO3)2 13 

of the iodo complex of cobalt (II) indicating the presence of 

M-I bond [11-13]. The non-conducting nature of the 

complexes showed that the iodide ions were coordinated to 

the Co (II) ion. The b<strong>and</strong> at 366 cm -1 is assigned to Cu-Cl 

bond. 

Three strong b<strong>and</strong>s at 1460, 1360 <strong>and</strong> 1010 cm -1 were 

observed in the spectra of nitrato complex of Co (II) <strong>and</strong> at 

1450, 1360 <strong>and</strong> 1010cm -1 in the spectra of nitrato complex of 

Cu (II). These were assigned to υ a (NO 2 ), υ s (NO 2 ) <strong>and</strong> υ(NO) 

vibrations, respectively indicating that unidentate 

coordination of the nitrate ion to the Co (II) <strong>and</strong> Cu (II) ions 

has taken place [14]. The separation of the two highest 

frequency b<strong>and</strong>s was 100 <strong>and</strong> 90 cm -1 in the Co (II) <strong>and</strong> Cu 

(II) complexes, respectively. Moreover, the absence of any 

b<strong>and</strong> at 1290 cm -1 due to υ a (NO 2 ) indicated that bidentate 

coordination has not taken place. 

Two medium intensity b<strong>and</strong>s at 906 <strong>and</strong> 547 cm -1 have 

been observed in the sulphato complex. Three b<strong>and</strong>s in the 

region 1210, 1142 <strong>and</strong> 1008 cm -1 have also been observed. 



112 

A 

C 

B 

D 

magnetic moment of 3.14 B.M. suggesting an octahedral 

geometry. 

3.5.3 Cu(II) complexes 

The spectra of all the Cu(II) complexes showed broad 

b<strong>and</strong>s in the range 686-548 nm <strong>and</strong> 525-306 nm. They have 

been assigned to the 2 E g → 2 T 2g <strong>and</strong> charge-transfer transitions, 

respectively, in an approximately octahedral lig<strong>and</strong> field. The 

nature of the spectral b<strong>and</strong>s <strong>and</strong> the paramagnetic behaviour 

of the copper(II) complexes indicate a distorted octahedral 

configuration around copper(II) ion[19]. The acetato, chloro, 

nitrato <strong>and</strong> sulphato complexes showed magnetic moments of 

1.96, 2.02, 2.27 <strong>and</strong> 1.51 B.M., respectively confirming that 

they have distorted octahedral geometries. 

A 

B 

Fig.5. Antibacterial activity of A) the lig<strong>and</strong> L 1 B) [Cu(L 1 ) 2 Cl 2 ] C) 

[Cu(L 1 ) 2 SO 4 ] D) [Ni(L 1 ) 2 (CH 3 COO) 2 ] on E. Coli 

Thus the sulphato group in this complex is concluded to be a 

chelating bidentate lig<strong>and</strong> [15,16]. This is also confirmed by 

analytical data. 

ZI=11mm 

ZI=14mm 

3.5 Magnetic <strong>and</strong> electronic spectral <strong>studies</strong> 

C 

D 

Table 3 lists the important electronic spectral b<strong>and</strong>s of 

the complexes <strong>and</strong> their assignments. 

3.5.1 Co(II) complexes 

The spectra of the iodo <strong>and</strong> nitrato complexes of Co(II) 

showed transitions in the ranges 820-694, 690-593 <strong>and</strong> 530- 

25 nm <strong>and</strong> were assigned to the 4 T 1g (F)→ 4 T 2g (F), 4 T 1g (F) 

→ 4 A 2g (F) <strong>and</strong> 4 T 1g (F) → 4 T 1g (P) transitions [17], respectively. 

This indicates octahedral geometry around Co(II) ion. The 

broad b<strong>and</strong> in the region 525 -694 nm has been assigned to 

the transition 

4 T 1g (F) → 4 T 1g (P) in an approximately 

octahedral field. The iodo-<strong>and</strong> the nitrato complexes showed 

a magnetic moment of 4.84 <strong>and</strong> 3.10 B.M. respectively, 

which corresponded to high spin octahedral geometry. 

E 

ZI=10mm 

F 

ZI=15mm 

3.5.2 Ni(II) complexes 

ZI=13mm 

ZI=13mm 

Three b<strong>and</strong>s at 770, 740 <strong>and</strong> 440 nm have been observed 

for the acetato complex of nickel (II). These have been 

assigned to the transitions, 3 A 2g → 3 T 2g , 3 A 2g → 3 T 1g (F) <strong>and</strong> 

3 A 2g → 3 T 1g (P), respectively, in an octahedral symmetry. The 

maxima of the absorption b<strong>and</strong>s for these complexes are 

within the region usually found for paramagnetic pseudooctahedral 

nickel(II) complexes [18]. The complex showed a 

Fig.6. Zone of inhibition observed in the antifungal activity of A) lig<strong>and</strong> L 1 

B) [Co(L 1 ) 2 I 2 ] C) [NI(L 1 ) 2 (CH 3 COO) 2 ] D) [Cu(L 1 ) 2 (CH 3 COO) 2 ] E) 

[Cu(L 1 ) 2 Cl 2 ] F) [Cu(L 1 ) 2 (NO 3 ) 2 ] on A. niger 

3.6 Antimicrobial activity 

The biological activity of the lig<strong>and</strong> <strong>and</strong> three of its 

complexes was investigated. The lig<strong>and</strong> <strong>and</strong> the acetato 

complex of Ni(II) <strong>and</strong> the chloro <strong>and</strong> sulphato complexes of 



113 

Cu(II) were evaluated for in vitro antibacterial activity 

against Escherichia coli <strong>and</strong> in vitro antifungal activity 

against Aspergizlus niger. Nutrient Agar 1.5% [20] <strong>and</strong> 

potato agar medium [21] were employed for the bacterial <strong>and</strong> 

fungal growth respectively. The zones of inhibition <strong>and</strong> the 

minimum inhibitory concentrations were determined <strong>and</strong> 

presented in Table 4 <strong>and</strong> Fig.5(A-D). The lig<strong>and</strong> did not 

show any antibacterial activity but the complexes showed 

antibacterial activity. 

The lig<strong>and</strong> <strong>and</strong> five of the complexes were investigated 

for antifungal activity. The lig<strong>and</strong>, the iodo complex of 

Co(II), acetato complex of Ni(II), acetato, chloro <strong>and</strong> nitrato 

complexes of Cu(II) were tested against Aspergillus niger. 

The zones of inhibition have been tabulated in Table 5 <strong>and</strong> 

Fig.6(A-F). It has been observed that the lig<strong>and</strong> <strong>and</strong> all the 

tested complexes showed antifungal activity against 

Aspergillus niger. Except the acetato complex of Ni(II), all 

the complexes showed more antifungal activity than the 

lig<strong>and</strong>. 

4. CONCLUSIONS 

A total of seven complexes of N-phenyl(methylphenyl-5- 

pyrazolyl)methylidene]aniline were synthesized <strong>and</strong> 

characterised. The physico-chemical properties of all the 

complexes were studied <strong>and</strong> they were found to have the 

general formulae [ML 2 X 2 ]. The structures suggested for these 

compounds are given in Figs.3& 4. The lig<strong>and</strong> <strong>and</strong> the 

complexes were screened for their antibacterial activity 

against Escherichia coli <strong>and</strong> for their antifungal activity 

against Aspergillus niger. 

The lig<strong>and</strong> <strong>and</strong> the complexes were screened for their 

antibacterial activity against Escherichia coli. The zones of 

inhibition were determined. They were also screened for their 

antifungal activity against Aspergillus niger. The minimum 

inhibitory concentration was determined. The lig<strong>and</strong> did not 

exhibit any antibacterial activity but the complexes showed 

activity against E. coli. The lig<strong>and</strong> <strong>and</strong> the complexes showed 

antifungal activity. 

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