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Synthesis, Characterization, Anti microbial and DNA

Cleavage Studies of some Schiff’s Base Metal Complexes

Derived from Sulphapyridine and 4-Isopropyl

benzaldehyde P. Jona1, Dr. V Gnana Glory Kanmoni2 and Dr. C. Isac Sobana Raj3

1Research Scholar, Reg. No. 18133282032015, Department of Chemistry, Women’s Christian College, Nagercoil. 2Department of Chemistry, Women’s Christian College, Nagercoil.

3Department of Chemistry, Nasamony Memorial Christian College, Marthandam. (Affiliated to Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli – 629012, Tamil Nadu, India)

1E-mail: [email protected] 2E-mail: [email protected]

3E-mail: [email protected]

Abstract: Novel solid transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with a Schiff base ligand derived from

sulpha pyridine and 4-Isopropyl benzal-dehyde were successfully synthesized. The complexes have been characterized by elemental

analysis, IR, 1HNMR, UV-vis, spectral data, magnetic, conductivity and thermal studies. The molar conductance data reveal that all

the metal chelates were non-electrolytes. Magnetic susceptibility data helps to assign the geometry of the synthesized metal (II)

complexes. Anti microbial activity of the ligand and its metal complexes were studied. It has been found that all the complexes are

antimicrobially active show higher activity than ligand. The nuclease activity of the above metal complexes were assessed by gel

electrophoresis assay and the results show that the metal complexes cleave PUC18 DNA in presence of hydrogen peroxide compared

to the ligand.

Key words: Schiff base, Sulpha pyridine, 4-Isopropyl benzaldehyde, Anti microbial, DNA cleavage.

1. INTRODUCTION

Schiff bases and its complexes have been employed to many reactions in synthetic, pharmaceutical and

biochemical industries [1] sulphonamides and their Schiff base – derived compounds are extensively used

for anti-microbial, antitumour, diuretic, anti-thyroid, antioxidant, anti inflammatory and protease inhibitor

activities [2,3]. Many drugs possess modified pharmacological and toxicological potentials when

administered in the form of their metal complexes [4,5]. In this study sulphapyridine, a sulphonamide

sulphadrug is used to prepare Schiff base ligand and its metal complexes. Sulphapyridine (IUPAC-Name:

4-amino-N-pyridin-2-ylbenzene sulphonmamide) belongs to one of the first generation of sulphonamide

antibiotics. It was used to treat infections like pneumonia or IgA disease. It is a good antibacterial drug [6].

When sulphapyridine is incorporated with transition metal, its biological activities increases. The central

metal ions in these complexes act as active sites for pharmacological agent. This feature is employed for

modeling active sites in biological systems. Therefore, in view of our interest in synthesis of new Schiff

base complexes which might find application in pharmacological industries. We have synthesized and

characterized new transition metal complexes of Schiff base formed by the condensation of sulphapyridine

and 4-Isopropyl benzaldehyde.

2. MATERIALS AND METHODS

2.1 Materials

All the chemicals and solvents used in the present work were of analytical grade. Sulpha-pyridine was

purchased from high media. 4-Isopropyl benzaldehyde was purchased from Sigma Aldrich. Metal Nitrates

and the solvents were purchased from merck.

2.2 Methods of Synthesis

2.2.1 Synthesis of Schiff base ligand

The ligand is prepared by taking equimolar ratio of 4-Isopropyl benzaldehyde and sulphapyridine, which

are dissolved in ethanol. It is then refluxed for two hour and reaction product is poured into ice. Yellow

precipitate is filtered and washed with water [7].

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2.2.2 Synthesis of Schiff base metal complexes

The metal complexes were prepared by adding aqueous solution of Transitions metal (II) Nitrate to the

ligand in ethanol in 1:2 molar ratios and refluxed for about twelve hours at 60-70C. The precipitated

solids were washed with ethanol, and hot water and finally dried under at 90C [8].

2.3 Instruments

Elemental analysis were carried out at SAIF, STIC, Kochi, Kerala. IR spectra were recorded as KBr

pellets with a JASCOFTIR 4100 spectro photo meter in the 4000-400 cm-1 range. 1H NMR spectra were

recorded in CDCL3 on a Bruker AVAVCE 111 400 MHz-NMR spectrometer using TMS as the internal

standard at SAIF, STIC, Kochi, Kerala, UV-Visible spectra were obtained in a Jasco V 570 UV-Vis

spectro polar meter in the wavelength range 200-900 nm. Magnetic susceptibility measurements were

carried out at Nasamony Memorial Christian College Marthandam, India. Conductance measurements

were studied using systronic conductivity bridge type 305. Melting points were determined by using Elico

melting point apparatus. Thermo gravimetric analysis is carried out using Perkin Elmer pyres Diamond

TG/DTA analyzer at SAIF, STIC, Kochi, Kerala. In vitro anti microbial screening and DNA cleavage

studies were carried out at inbiotics, Nagercoil.

3. RESULTS AND DISCUSSION

The structure of the synthesized ligand was established with the help of IR, NMR, UV-Visible spectra

data and micro analytical data. The complexes are microcrystalline, coloured powders having melling

points higher than the ligand. They are stable in air and non-hygroscopic in nature. All complexes gave

satisfactory elemental analysis suggesting 1:2 (M:L) stoichiometry.

3.1 Characterization

3.1.1 Element Analysis

Table (1) shows the list of the elemental analysis of the synthesized Schiff base ligand and their

transition metal (II) complexes which are in good agreement with the calculated values.

TABLE 1

ELEMENTAL ANALYSIS OF THE LIGAND AND THEIR TRANSITION METAL (II) SCHIFF BASE COMPLEXES

Compound Molecular formula Molecular

Weight

Elemental Analysis calculated (Experimental ) %

C H N S O M (Mn, Co, Ni,

Cu, Zn)

L2 C21H21N3O2S 379 66.49

(65.96)

5.54

(6.02)

11.08

(10.98)

8.44

(8.92)

8.44

(8.12) -

Mn(L2)2(NO3)2 C42H42MnN8O10S2 936.94 53.79

(52.28)

4.48

(5.12)

11.95

(12.15)

17.08

(17.91)

6.83

(7.41)

5.86

(5.12)

Co C42H42CoN8O10S2 940.94 53.56

(54.05)

4.46

(3.93)

11.90

(12.52)

17.00

(16.94)

6.80

(6.59)

6.26

(5.94)

Ni C42H42NiN8O10S2 940.69 53.58

(53.97)

4.46

(3.97)

11.91

(12.32)

17.01

(16.47)

6.80

(7.08)

6.24

(6.58)

Cu C42H42CuN8O10S2 945.55 53.30

(54.12)

4.44

(3.91)

11.84

(12.08)

16.92

(17.12)

6.77

(6.32)

6.72

(6.41)

Zn C42H42NiN8O10S2 947.38 53.20

(52.66)

4.43

(5.02)

11.82

(11.32)

16.89

(17.08)

6.76

(7.05)

6.90

(7.02)

3.1.2 Molar Conductance

The molar conductivity data for all the transition metal (II) complexes prepared from ligand (L2) in

ethanol solution at room temperature are observed are tabulated in table 5.2. The molar conductance values

fell with in the range 9.48-25.12 ohm-1 cm2 mol-1 for all completes showing the non-electrolytic nature.

This suggested that nitrate ions are coordinated with the metal ions. [9].

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TABLE 2 MOLAR CONDUCTANCE OF THE LIGAND (L2) AND THEIR METAL COMPLEXES

S. No Compound Conductance ohm-1 cm2 mol-1

1 C21H21N3O2S(L2) -

2 Mn(L2)2(NO3)2 21.16

3 Co(L2)2(NO3)2 9.48

4 Ni(L2)2(NO3)2 11.19

5 Cu(L2)2(NO3)2 25.12

6 Zn(L2)2(NO3)2 19.87

3.1.3 Infrared spectra

The relevant FT-IR data of the ligand and the metal complexes are presented in table 5.3. and the spectra

presented in Figure 5.1 to 5.6. The IR band at 1635.64 cm-1 of the free Schiff base ligand is due to the azo-

methine group. (>C=N) [10]. The azomethine peak in ligand is shifted to lower region around 1610 cm-1 in

metal complexes suggesting the coordination through >C = N-group (table 3). Further evidence for the

coordination of the N atom of the Schiff base with metal atom was shown by the appearance of a new

weak band in the region 516-521 cm-1. [11]. The absorption band ranges from 1326 cm-1 to 1345 cm-1 is

attributed to coordinated nitrates with central metal atom. Comparision of the bands in the infrared spectra

of the ligand with the metal complexes support the mode of coordination of the ligand with metal ions.

The band due the Hetero cyclic ring nitrogen present in pyridine moiety is almost unaffected in the spectra

of the metal complexes confirming that the Nitrogen atom of the pyridine moiety is not coordinated to the

metal ion [12]. The band due to S=0, >N-H of the Sulphonamide moiety remains unchanged in the spectra

of the metal complexes indicating the non-involvement of the N and O atoms in bond formation [13].

TABLE 3 INFRARED SPECTRAL DATA FOR LIGAND (L2) AND THEIR METAL (II) COMPLEXES

Ligand/

complexes C=N C=C

C-H

aromatic S=0 N-H

Hetero cyclic ring

nitrogen C-N NO3 M-N

C21H21N3O2S (L2) 1635.64 1504.48 3240.41 1365.60 3417.86 1450.47 - -

Mn(L2)2(NO3)2 1610.14 1492.35 3249.78 1366.25 3418.14 1452.85 1327.03 516.92

Co(L2)2(NO3)2 1611.78 1496.78 323.941 1365.61 3417.86 1451.82 1345.02 516.81

Ni(L2)2(NO3)2 1609.68 1497.82 3245.53 1373.32 3419.85 1448.34 1332.07 514.12

Cu(L2)2(NO3)2 1609.14 1480.77 3270.58 1367.82 3416.15 1450.49 1325.12 520.78

Zn(L2)2(NO3)2 1608.98 1478.53 3281.14 1373.32 3417.13 1450.48 1326.13 521.20

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Fig. 1: IR spectrum of the shiff base ligand (L2)

Fig. 2: IR spectrum of [Mn(L2)2(NO3)2] complex

Fig. 3: IR spectrum of [Co(L2)2(NO3)2] complex

Fig. 4: IR spectrum of [Ni(L2)2(NO3)2] complex

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Fig. 5: IR spectrum of [Cu(L2)2(NO3)2] complex

Fig. 6: IR spectrum of [Zn(L2)2(NO3)2] complex

3.1.4 Electronic absorption spectra

The electronic absorption spectrum of ligand exhibits high intense absorption peaks at 256 nm and

342 nm. Which have been assigned to -* and n-* transition respectively.

The UV-Vis spectra of [Mn(L2)2(NO3)2] complex at 248 nm and 315 nm are assigned as -* transition

and n-* transition respectively. Mn(II) complex exhibit sharp band at Visible region is displayed at 329

nm, 398 nm. Which is assigned to the ligand field and charge transfer transitions. This complex also

exhibited d-d transition in the visible region of their spectra. The band at 468nm is assigned to (d-d)

transition of type 6A1 4T2 [14]. [Co(L2)2(NO3)2] complex shows two well resolved peaks at 689 nm

assigned to the 4A2(F) 4T1(P) transition and at 602 nm for 4A2 – 4T1(F) transition along with broad bond

at 242 nm and 337 nm attributed to the -* and n-* transitions respectively of the azomethane (C=N)

group. [15]. The spectrum of Ni(II) complex [Ni(L2)2(NO3)2] shows an absorption band at 628 nm along

with peak for electronic transitions. This peak corresponds to the transition 3T1(F) 3T1(P) which

indicates the telra hedral environment of the ligand surrounding Ni(II) complexes [15]. The spectrum of

Cu(II) complex [Cu(L2)2(NO3)2] shows as band at 642 nm along with the band for electronic transitions

such as -* and n-*. This band is attributed to 2B1g 2A1g transition. In general, due to Jahn-Teller

distortion, square planar Cu(II) complexes give a broad absorption band between 600 and 700nm. This

Suggest that the [Cu(L2)2(NO3)2] complex have square planar geometry [16].

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The [Zn(L2)2(NO3)2] complex shows an absorption band at 438 nm along with electronic transition

bands. This is attributed to the Ligand metal charge transfer transition. Which is compatible with this

complex having a tetrahedral geometry [17].

TABLE 4 UV-VIS SPECTRAL DATA MAX(NM) FOR THE SCHIFF BASE LIGAND (L2) AND ITS METAL COMPLEXES

S. No Compounds max [nm] Electronic

Transition Charge transfer Geometry

1 C21H21N3O2S (L2) 256

342

-*

n-* - -

2 Mn(L2)2(NO3)2

248,315

329,398

468

-*

-*

Charge transfer (CT)

Charge transfer (CT)

A1 4T2

Tetra hedral

3 Co(L2)2(NO3)2 242, 1337

602, 689

-*

n-*

T1(P) 4A2(F) 4A24T1(F)

Tetra hedral

4 Ni(L2)2(NO3)2 216, 321

628

-*

n-* 3T1(F)3T1(P) Tetra hedral

5 Cu(L2)2(NO3)2 239, 231

642

-*

n-* 2B1g2A1g Square planar

6 Zn(L2)2(NO3)2 226, 338

438

-*

n-* LM(CT) Tetra hedral

3.1.5. Magnetic susceptibility measurement

Magnetic susceptibility measurements of the powdered metal (II) complexes were carried out by

employing the Gouy’s method at room temperature. The observed and calculated magnetic moment values

are listed in the table 5.4. The observed magnetic moment values of [Mn(L2)2(NO3)2] complex is 6.25BM.

The assigned spectrum transition and magnetic moment value indicate the tetrahedral structure of

[Mn(L2)2(NO3)2] complex. [Co(L2)2(NO3)2] metal complex shows 4.61 BM of observed magnetic moment.

This value is with in the expected range of octahedral Co(II) complexes [18 - 20]. In general square planar

Ni(II) complexes are diamagnetic while tetrahedral complexes have magnetic moments in the range 3.2-

4.1 BM. The [Ni(L2)2(NO3)2] complex has a magnetic moment value of 3.94 BM. Which is with in the

normal range observed for tetrahedral Ni(II) complex. The magnetic moment value of the [Cu(L2)2(NO3)2

complex was observed to be 1.93 BM. Which indicates that the complex is monomeric and paramagnetic.

Zn(II) complex with d10 configuration. Which indicate that the [Zn((L2)2(NO3)2] complex is diamagnetic in

nature. From the Electronic spectrum and magnetic moment value of the complexes shows that Mn(II),

Co(II), Ni(II) and Zn(II) complexes were in tetrahedral geometry where as the Cu(II) complex is in square

planar geometry [21].

TABLE 5 MAGNETIC SUSCEPTIBILITY DATA OF THE COMPLEXES

Complexes eff (BM) calculated eff (BM) observed

Mn(L2)2(NO3)2 5.91 6.25

Co(L2)2(NO3)2 4.2-4.88 4.61

Ni(L2)2(NO3)2 3.2-4.1 3.94

Cu(L2)2(NO3)2 1.73 1.93

Zn(L2)2(NO3)2 Diamagnetic Diamagnetic

3.1.6 Thermal Studies

Thermogravimetric and differential thermogravimetric analysis were carried out for [Co(L2)2(NO3)2]

metal complex one among the five transition metal (II) complexes prepared from ligand (L2) The TGA-

DTG curves of [Co(L2)(NO3)2] complex was recorded in the temperature ranges from 40-860Cat

20.00C/min is as shown in Fig. 7 under Nitrogen flow. The correlation between the different

decomposition steps of [Co(L2)2(NO3)2] complex with corresponding weight losses are discussed in terms

of proposed formula of the metal (II) complexes. The TGA results showed that the Co(II) complex is

thermally stable in temperature range,40-319.80C. The decomposition starts at 319.80C and gets

completed at 399.28C with first decomposition step. From the literature it is come to know that the TGA

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curves indicate in the temperature range 230-400C the compounds start to loss nitrate ion and 400-800C

the Schiff base molecule is lost from the first step of decomposition. From this it is confirmed the nitrate

coordination with Co(II) complex. Second step of decomposition started at 399.28C with the weight loss

of 6.748% per minutes corresponds to loss of organic moiety (Schiff base molecule) [M. Sekerai et al.,

2004]. Third step of decomposition started at 642.83C with the weight loss of 7.855%/min corresponds to

loss of Schiff base molecule. Finally it forms metal oxide CoO [22].

The stages of thermal decomposition of the [Co(L2)2(NO3)2] complex can be written as under [23] [24].

Fig. 7: TGA and DTA curves of [Co(L2)2No3)2] complex

3.1.7 H1 NMR Spectra

1H NMR spectra of free Schiff base ligand (L2) and its metal complexes was recorded in chloroform

(CDCl3) solution using tetra-methyl silane (TMS) as internal standard. In the 1H NMR spectrum of Ligand

(L2) and their metal complex Co(L2)2(NO3)2 were shown in fig. 8 and 9. The ligand showed peak at

= 8.921 ppm, suggests the presence of –CH=N- linkage. The strong signal which appeared in the region

between (3-4 ppm, 2H) is due to unreacted sulphonamide moiety during ligand synthesis [25].

The 1H NMR spectra of complex [Co (L2)2(NO3)2] was recorded and examined by compared with those

of ligand which shows that the azomethine (-N=CH-1) proton signal in the spectrum of metal complex is

shifted down field [ = 7.950 ppm] compared to free ligand, assuming de shielding of azomethine group is

due to coordination with metal ion.

It was found that, as like ligand (L2) signals for aromatic H-were observed at (=7.939 ppm-6.405 ppm).

Signal for phenyl amine (=3-3.5 ppm) and signal for methyl group (2.2 ppm) were recorded for metal

complex [26].

399.28C (-6.748%/min)

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Fig. 8: NMR spectrum of Schiff base ligand (L2)

Fig. 9: NMR spectrum of [Co(L2)2(No3)2] complex

From the above data the, suggested structure of the coordination compounds prepared from Ligand (L2)

is shown in figure.

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(a) (b)

Fig. 10: Proposed structure of Schiff base metal complexes (a) tetrahedral geometry for Mn(II), Co(II), Ni(II) and Zn(II) complexes

and (b) square planar geometry for Cu(II) complexes

3.1.8 XRD Analysis

The powder XRD spectrum of Schiff base ligand (L2) was compared with the spectrum of the

[Cu(L2)2(NO3)2] Complex. It was interpreted in table 6 and 7. The diffractogram for the ligand and

(Cu(L2)2(NO3)2] complex are given in figure (11-12). Few new peaks appear in the spectrum of complex

compared to the spectrum of the ligand which indicates the formation of metal chelates. The grain size

(dXRD) of the Schiff base and complex are calculated with the help of XRD pattern using Scherrer’s

formulat [27]

DXRD = 0.9x/cos

Where ‘’ is wavelength, ‘’ is the full width at half maximum and ‘’ is the peak angle.

From the observed XRD pattern the average crystalline size of the Ligand (L1) and [Cu(L2)2(NO3)2]

complex are found to be 3.38 nm, 3.775 nm respectively. This suggested that the Ligand (L2) and

[Cu(L2)2(NO3)2] complex are in microcrystalline nature [28], [29].

TABLE 6 XRD DATA OF LIGAND (L1)

Pos. [2 Th] Height [cm] FWHM [2 Th] d-spacing (A) Rel. Intensity (%)

13.8861 155.59 0.0502 6.37755 42.25

15.0984 47.96 0.1338 5.86809 13.03

15.8215 77.29 0.1004 5.60151 20.99

16.2186 169.70 0.0836 5.46524 46.09

19.7514 38.23 0.2007 4.49496 10.38

20.5847 27.13 0.2007 4.31485 7.37

22.2277 367.19 0.1338 3.99948 99.72

23.3395 368.22 0.1506 3.81141 100.00

24.1259 48.81 0.2007 3.68893 13.26

24.9440 70.34 0.1338 3.56978 19.10

27.9494 149.87 0.2007 3.19237 40.70

31.0598 38.06 0.1338 2.87941 10.34

32.8336 85.90 0.1673 2.72780 23.33

35.9368 27.98 0.2007 2.49904 7.60

36.8214 18.40 0.4015 2.44101 5.00

38.6560 28.25 0.2007 2.32929 7.67

44.9638 19.68 0.5353 2.01609 5.34

53.0503 16.81 0.4015 1.72627 4.57

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TABLE 7 XRD DATA OF CU(L2)2(NO3)2 COMPLEX

Pos. [2 Th] Height [cm] FWHM [2 Th] d-spacing (A) Relation Intensity (%)

12.0779 143.54 0.1673 7.32797 13.69

12.8617 146.23 0.1338 6.88309 13.95

15.3066 126.39 0.1673 5.78874 12.06

15.8665 203.98 0.1673 5.58571 19.46

16.2621 130.09 0.0836 5.45071 12.41

17.5873 101.61 0.1673 5.04287 9.69

19.3224 1048.32 0.2342 4.59378 100.00

19.7817 350.44 0.0502 4.48815 33.43

20.0647 635.99 0.1004 4.42549 60.67

23.1205 195.59 0.1673 3.84703 18.66

24.1690 258.92 0.1673 3.68245 24.70

25.1070 620.78 0.0836 3.54696 59.22

26.2009 95.82 0.3346 3.40131 9.14

27.6033 56.86 0.2676 3.23161 5.42

28.3464 202.84 0.2007 3.14856 19.35

29.3475 110.07 0.1673 3.04339 10.50

30.1942 156.84 0.2342 2.95996 14.96

32.4032 47.77 0.2007 2.76304 4.56

32.8092 64.84 0.1004 2.72977 6.18

34.2562 43.42 0.2007 2.61770 4.14

38.2575 37.56 0.4684 2.35263 3.58

40.1204 40.64 0.2007 2.24758 3.88

43.2996 41.29 0.2676 2.08964 3.94

44.6138 28.28 0.5353 2.03110 2.70

Fig. 11: Diffractogram of Schiff base ligand (L2)

Fig. 12: Diffractogram of [Cu(L2)2 (No3)2] complex

Position [°2Theta] (Copper (Cu))

20 30 40 50 60 70

Counts

0

100

200

300

400

Jona - JBCo

Position [°2Theta] (Copper (Cu))

20 30 40 50 60 70

Counts

0

500

1000

Jona - JBL

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3.1.9 SEM Analysis

The SEM micrographs of the ligand (L2) and [Cu(L2)2(NO3)2] complex are shown in fig. 13, 14

respectively. It is seen from the figure that the complex shows platelet like structure. While the ligand (L2)

exhibit ice-cube like structure. The particle size of Ligand (L2) and the complex are in the diameter range

of few microns. However, particle with size less than 100 nm were also observed which groups to form

agglomerates of larger size. The average crystalline size obtained from XRD also shows that the particles

were agglomerated that these complexes have polycrystalline with nanosized grains.

Fig. 13: SEM pattern of Schiff base ligand (L2)

Fig. 14: SEM patter of [Cu(L2)2 (No3)2] complex

3.2 Biological Applications

3.2.1 Antibacterial studies

The free Schiff base ligand (L2) and its respective metal chelates were tested for their vitro antibacterial

activity against two gram-positive bacteria such as Bacillus subtilis and Staphylococcus aureus and three

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gram-negative bacteria such as Pseudomonas aeruginosa, Enterobacter aerogenes and Escherichia coli.

The inhibition zone diameter (mm/mg sample) values of the investigated compounds were summarized in

Table 8. A comparative study of inhibition zone diameter (mm/mg sample) values of the Schiff base

ligand (L2) and their metal (II) complexes were shown in fig. 15 indicates that the metal complexes exhibit

higher antibacterial activity than the free Schiff base ligand (L2). Such increased activity of the complexes

can be explained on the basis of Tweedy’s chelation theory [30], [31] chelation reduces the polarity of the

metal ion significantly because of the partial sharing of its positive charge with the donor group and also

due to pi-electron delocalization on the whole chelate ring. The lipids and polysaccharides are some

important constituents of the cell wall and membranes which are preferred for metal ion interaction. Apart

from this, the cell walls also contain many phosphates, carbonyl and cysteinyl ligands which maintain the

integrity of the membrane by acting as a diffusion barrier and also provide suitable sites for binding.

Moreover the decrease in polarity increases the lipophilic nature of the chealates and an interaction

between the metal ion and the lipid is favoured.

This may lead to the breakdown of the permeability barrier of the cell ensuing in interference with the

normal cell processes. The Schiff base ligand has moderate inhibitory property on the growth of the tested

micro organisms. This is due to the presence of azo-methine group which have chelating properties. These

properties may used in metal transport across the bacterial membranes or attach to the bacterial cells at a

specific site from which it can interfere with their growth. The antibacterial activity of the metal (II)

complexes ligand (L2) follows the order. Co(II) > Mn(II) > Ni(II) Cu(II) > Zn(II). This indicates that the

incorporation of metal ions in chelation can improve the biological activity of the parent organic

compounds.

TABLE 8: ANTI BACTERIAL ACTIVITY OF SCHIFF BASE LIGAND (L2) AND THEIR METAL COMPLEXES

Ligand / complexes

Zone of inhibition (mm)

Bacillus

subtiles

Staphylococus

aureus

Pseudomonas

aeruginosa

Enterobacter

aerogenes E.Coli

Ligand (L2) 12 11 - 10 12

Mn(L2)2(NO3)2 23 21 23 27 22

Co(L2)2(NO3)2 25 27 24 28 25

Ni(L2)2(NO3)2 22 20 21 23 20

Cu(L2)2(NO3)2 24 19 20 20 19

Zn(L2)2(NO3)2 - 16 18 - -

Standard Gentamyain 26 28 25 29 28

Fig. 15: Percentage inhibition of Schiff base ligand (L2) and their metal complexes

0

5

10

15

20

25

30

Bacillus subtiles Staphylococus aureus Pseudomonas aeruginosa

Enterobacter aerogenes E.Coli

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3.2.2 Antifungal studies

Antifungal activity of shicff base ligand (L2) and its metal complexes were studied against three fungal

cultures such as Pencillium Notatum, Aspergillus Niger and Rhizopus by disc diffusion method. Nystatin

was used as standard drug. The results are listed in table 9.

From the data given from the table a comparative analysis was carried out which is shown in fig. 16.

From the analysis we found that the metal complexes shows good antifungal activity than Schiff base

ligand (L2). All the metal complexes shows good antifungal activity against Rhizopus and Pencillium

Notatum. Metal complexes shows poor antifungal activity against Aspergillus Niger [Ni(L2)2(NO)2] and

[Cu(L2)2(NO3)2] complexes shows good antifungal activity against all the fungal strains. This increased

activity of Schiff base metal complexes can be explained by overtone’s concept and Tweedy’s chelation

theory [32].

TABLE 9 ANTIFUNGAL ACTIVITY OF SCHIFF BASE LIGAND (L2) AND THEIR METAL COMPLEXES

Ligand / metal complexes Zone of inhibition (mm)

Pencillium Notatum Aspergillus niger Rhizopus

C21H21N3O2S (L2) 7 - 9

Mn(L2)2(NO3)2 12 1 13

Co(L2)2(NO3)2 11 - 17

Ni(L2)2(NO3)2 10 6 15

Cu(L2)2(NO3)2 14 12 20

Zn(L2)2(NO3)2 - 14 18

Standard/Nystatin 16 18 19

Fig. 16: Percentage inhibition of Schiff base ligand (L2) and their metal complexes

3.2.3 DNA cleavage studies

The chemical nuclease efficiency of Ligand (L2) and its transition metal (II) complexes has been studied

by gel electrophoresis by using supercoiled PUC18 DNA to its nickel circular form was used as the

sample. [PUC18 is a plasmid DNA of 2686 base pairs].

Figure 5.20 exhibit the cleavage patterns of synthesized ligand (L2) and its metal complexes in the

photolytic method. Control (Lane I) do not show any cleavage of plasmid DNA where as Ligand (L2)(Lane

2) and their metal (II) complexes show good DNA cleavage activity and is evident by complete

degradation of DNA resulting in the disappearance of bands on gel [33]. The supercoiled plasmid DNA

was completely degraded resulting in the disappearance of bands on agarose gel. Further the presence of a

smear and decreased intensity of bands in the gel diagram indicates the presence of radical cleavage [34].

0

2

4

6

8

10

12

14

16

18

20

Pencillium Notatum Aspergillus niger Rhizopus

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Fig. 17:Gel electrophoresis diagram of the Schiff base Ligand (L2) and their metal complexes

Lane 1: Control (Plasmid DNA)

Lane 2: Plasmid DNA + L2- Completely Cleaved the Plasmid DNA Lane 3: Plasmid DNA + Mn(L2)2 (No3)2 Completely Cleaved the Plasmid DNA

Lane 4: Plasmid DNA + Co(L2)2 (No3)2 Completely Cleaved the Plasmid DNA

Lane 5: Plasmid DNA + Ni(L2)2 (No3)2 - Completely Cleaved the Plasmid DNA Lane 6: Plasmid DNA + Cu(L2)2 (No3)2 - Completely Cleaved the Plasmid DNA

Lane 7: Plasmid DNA + Zn(L2)2 (No3)2 - Completely Cleaved the Plasmid DNA

4. CONCLUSION

In this paper the preparation and characterization of a new Schiff base derived from sulphapyridine and

4-Isopropyl benzaldehyde has been reported. From the satisfactory micro analytical and various spectral

data, it is concluded that ligand acts as monodentate coordinating through azomethine nitrogen and nitrate

(NO3) nitrogen atoms. Magnetic and electronic spectral data reveal tetrahedral geometry for Mn(II),

Co(II), Ni(II) and Zn(II) complexes while Cu(II) complex possess square planar geometry. XRD and SEM

analysis suggests the crystalline and morphological structural studies of the complexes. The antimicrobial

and DNA cleavage activities indicate that the complexes show higher activity than the ligand.

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