INTERNATIONAL JOURNAL OF PHARMACEUTICAL … 865.pdf · · 2014-10-26was studied using Kirby Bauer method using 24 commonly used antibiotics in case ... The metal complexes were

Research Article CODEN: IJPRNK IMPACT FACTOR: 4.278 ISSN: 2277-8713 Bootwala S, IJPRBS, 2014; Volume 3(5): 222-236 IJPRBS

Available Online at www.ijprbs.com 222

CADMIUM AND MERCURY COMPLEXES OF A SCHIFF BASE LIGAND: SYNTHESIS,

SPECTRAL CHARACTERIZATION, THERMAL AND ANTIMICROBIAL PROPERTIES

ARUNA K1, TARIQ M1, BOOTWALA S2, MORE G2

1. Department of Microbiology, Wilson College, Mumbai-400007, India 2. Department of Chemistry, Wilson College, Mumbai-400007, India

Accepted Date: 24/09/2014; Published Date: 27/10/2014

Abstract: Some new cadmium (II) and mercury (II) chloride complexes of the Schiff base ligand 2-amino-N'-[(1E,2Z)-2-(hydroxyimino)-1-phenylethylidene]-4,5,6,7-tetrahydro-1-benzothiophene-3-carbohydrazide were synthesized, and characterized by physical and spectral study such as elemental analysis, molar conductance, UV–visible spectra, FT-IR spectra and, 1H NMR spectra. All complexes were stable in DMF solvent and the low molar conductivity confirms their non-electrolytic nature. The micro analytical and physico-chemical data suggested the stiochiometry of the 1:1 (metal: ligand) complexes and geometry of these complexes were tetrahedral. The thermal behavior (TGA/DTA) of the complexes was studied and kinetic parameters were determined by Coats-Redfern method. The antimicrobial activity of these Schiff based metal complexes were also determined against Drug resistant Extended Spectrum β-Lactamase and Metallo β-Lactamase producing pathogens. Significant zones of inhibition of 11-16 mm were observed against the test pathogens indicating its possible use in cases of drug resistant infections.

Keywords: Cadmium, Mercury, Schiff base, Drug resistant

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INTRODUCTION

Schiff base and its complex derivatives, especially heterocyclic amine family, have been an

important field in drug research and development due to their broad bioactivities such as

antitumor, antibacterial, and antiviral activities [1,2]. These complexes also have applications in

clinical, analytical and industrial fields, in addition to their important roles in reversibly binding

oxygen in epoxidation reactions [3], biological properties [4] catalytic role in hydrogenation of

olefins [5], photochromic properties [6], analytical determination [7] and organic synthesis [8].

Recently group XII metal complexes, which contain a stable d10 electronic configuration, have

received a lot of attention in the fields of inorganic chemistry, biochemistry and environmental

chemistry [9,10]. Also d10 complexes with polydentate ligands have been considerably

investigated as potential luminescent materials [11]. There is substantial interest in the

coordination chemistry of cadmium and mercury because of the toxic environmental effect

caused by them. Therefore mobilization and immobilization of these chemicals in the

environment, in organisms, and in some chemical processes have been found to depend

significantly on the complexation of these metal ions by coordination with nitrogen donor

ligands [12].

There have also been reports on the antibacterial properties of mercury as well as cadmium

and it is also used in medical fields [13,14].

In continuation of our research [15], the aim of this work, is to prepare and investigate the

complexes of Cd(II) and Hg(II) with Schiff base ligand 2-amino-N'-[(1E,2E)-2-(hydroxyimino)-1-

phenylethylidene]-4,5,6,7-tetrahydro-1-benzothiophene-3-carbohydrazide and to screen the

metal complexes for its antibacterial activity. The general formula of these complexes are CdLCl

and HgLCl2, L=Schiff base ligand. The complexes were characterized by physical and spectral

data including microanalysis, FT-IR, UV-visible, 1H NMR and conductivity measurements. We

attempted to investigate the effect of these complexes against Extended Spectrum β-

Lactamase (ESBL) and Metallo β-Lactamase (MBL) producing pathogens. ESBLs and MBLs are

enzymes produced by pathogenic bacteria that are capable of hydrolyzing broad spectrum β-

lactam as well as 3rd generation cephalosporin antibiotics [16].

MATERIALS AND METHODS

All chemical used in the project work were of AR grade and was recrystallised while the solvent

were purified and double distilled before use. Metal content was determined by the standard

methods [17]. Molar conductance was measured in DMF (10-3 M solution) on an ELICO Digital

Conductivity meter Model CM-180. The IR spectra were recorded in KBr disc on a Perkin Elmer

Model 1600 FTIR Spectrophotometer. The electronic spectra of the complex in DMF were

recorded on UV-Systronic spectrophotometer. The 1H-NMR Spectra was recorded in DMSO on a

VXR-300S Varian Supercon NMR Spectrometer using TMS as the internal reference. Thermo



gravimetric studies of the complex were done on Netzch-429 Thermo-analyzer recording at a

rate of 10 oC min-1.

Preparation of ligand 2-amino-N'-[(1E,2Z)-2-(hydroxyimino)-1-phenylethylidene]-4,5,6,7-

tetrahydro-1-benzothiophene-3-carbohydrazide:2-amino-4,5,6,7-tetrahydro-1-

benzothiophene -3-carbohydrazide and (2Z)-2-(Hydroximino) 1-phenyl ethanone was prepared

according to a reported method[18,19]respectively. To a solution of this thiophenecarbohydrazide

derivatives (0.01mol) in ethanol (20ml) was added to a solution of (2Z)-2-(hydroxyimino)-1-

phenylethanone (0.01mol) dissolved in ethanol (20ml) in small portion with constant stirring.

The resulting solution was refluxed on a water bath for about four hours. On cooling the

solution, the hydrazone crystallized. It was then filtered, washed and sucked dry. Further

purification was done by crystallization from ethanol (MP 114oC).

Preparation of metal complexes: The metal complexes were prepared by the following general

procedure. To a magnetically stirred and warmed ethanolic solution (20ml) of the ligand

(0.01mol) added an ethanolic solution of metal (II) chloride in appropriate ratios dissolved in

ethanol (10ml) in small parts. After complete additions of the metal salt solution, the pH was

adjusted to 7.5 by adding ethanolic ammonia .It was then refluxed for about six hours in a

water bath and the resulting solution was reduced to half the initial volume and allow standing

overnight. The complex formed was filtered, washed successively with aqueous ethanol and

ether. Finally the complex was dried in vacuum over P4O10.

Test organisms used in the study: 10 MDR (Multi-Drug Resistant) gram negative uropathogens

were used in the study. This included 5 ESBL and 5 MBL producing strains of Escherichia coli,

Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Citrobacter diversus

which were characterized in a previous study [16].

Antimicrobial susceptibility of uropathogens: Antibiotic sensitivity profile of the pathogens

was studied using Kirby Bauer method using 24 commonly used antibiotics in case of infectious

diseases [16].

Antibacterial activity: Antibacterial activity of the metal complexes was determined by Agar

diffusion method. The metal complexes were dissolved in HPLC grade ethanol to obtain final

concentration of 100μg/μl and 200μg/μl. A loopful of the test isolates were inoculated in 10 ml

of Brain Heart infusion (BHI) broth and incubated at 37°C for 24 h in order to obtain actively

growing log phase isolates. Sterile 20 ml of Luria Bertani agar was melted cooled to around 40°C

and 0.4 ml test strain (0.1 O.D. at 530nm) was seeded and poured into a 9cm diameter aneubra

Petri plates.

Using a sterile cork borer (8 mm in diameter), wells was punched in each plate after

solidification of the medium. 50μl of the test sample (metal complex) was then added to the

wells and incubated at 37°C for 24 h to observe the zones of inhibition against palladium and



platinum complexes. Control wells were also set up using 50 μl of ethanol (solvent) for each

isolate. The mean value obtained for three individual replicates was used to calculate the zone

of inhibition for each isolate [20].

RESULTS AND DISCUSSION

Analytical data indicated that (2Z)-2-(Hydroximino) 1-phenyl ethanone condensed with 2-

amino-4,5,6,7-tetrahydro-1-benzothiophene -3-carbohydrazide in 1:1 molar ratio and the

product formed well defined complexes with the metal salts. Formation of the complexes can

be symbolized as follows:

CdCl2 + HL → [Cd(L)Cl] + HCl

HgCl2 + HL → [Hg(HL)Cl2]

L= 2-amino-N'-[(1E,2Z)-2-(hydroxyimino)-1-phenylethylidene]-4,5,6,7-tetrahydro-1-

benzothiophene-3-carbohydrazide

Formulation of the complexes has been based on their elemental analytical data. Complexes

are light yellow coloured, non hygroscopic and decomposed above 170oC. The molar

conductance values support the non-electrolyte nature of the complexes [21].

TABLE -1

PHYSICO-CHEMICAL CHARACTERISTIC OF SCHIFF BASE LIGAND AND ITS METAL COMPLEXES

Compound Colour F.Wt Elemental analysis (%)

Found(calcd)

Molar Cond.

(Ω-1cm2mol1)

C N S Cl M

L yellow 342.41 58.23

(59.63)

16.93

(16.36)

9.85

(9.36)

- - -

[Cd(L)Cl]

yellow 489.27 40.56

(41.73)

10.85

(11.45)

7.27

(6.55)

8.13

(7.25)

21.95

(22.98)

12.25

[Hg(HL)Cl2]

yellow 613.91 34.05

(33.26)

10.12

(9.13)

6.05

(5.22)

10.18

(11.55)

31.15

(32.67)

10.18

The spectral data of the compounds and their tentative assignments are shown in Table (II). It

can be seen that the characteristic absorption peak present in IR spectra of complexes are

similar to the ligand which indicate that the complexes have similar arrangement of ligand atom

around metal ions. The bonding of the ligand to the metal ions is investigated by comparing the

IR spectra of the free ligand with its metal complexes. In the region 3200-3400cm-1 the infrared

spectra of ligand and complex exhibit two sharp and intense band at 3275cm-1 and 3169cm-1

these two band assigned to the primary amine υ(NH2) of substituted thiophene which



indicates non-involvement of NH2 group in metal –ligand bonding. An intense broad band at

3300cm-1 tentatively assigned to the υ(NOH) vibration which is present in the spectrum of

Hg(II) complex indicates that non involvement of oximino OH group in the coordination to

metal ions where as this broad band is absent in the spectrum of Cd(II) complex indicates

deprotonation of oximo group took place in Cd(II) complex. A sharp band of medium intensity

around 3421cm-1 is due to υ(NH) is shifted to lower frequency by 11-30cm-1 in the complexes.

The IR spectra of the complex show that the ט(C=0) band at 1709 cm-1 in the spectra of the

ligand made a distinct shift towards lower frequency by 50-60 cm-1. This suggests that the

bonding of the ligand through the carbonyl oxygen in the keto form hydrazones group [22]. The

IR spectra of all complexes indicates that ט(C=N) band at 1658 cm-1 in the spectra of the ligand,

due to the azomethine linkage were shifted towards lower frequency by 50-60 cm-1 indicating

that the ligand coordination to the metal ions have azomethine nitrogen [23] on the other hand

,the characteristic ט(N-N) band was found to be shifted from 946 cm-1 in the spectrum of ligand

to 976-980cm-1 in the spectra of complexes confirming that the azomethine nitrogen atom

participated in coordination with the metal ions [24]. On the other hand, the bands present in

the 510-520cm-1 and 430-460cm-1 range may be taken as an indication to the coordination

between the metal ions with oxygen and nitrogen atoms respectively [25-27]. The band around

395cm-1 which was recorded on Plytec 30 spectrometer using CsI disc can be assigned to the

presence of υ(M-Cl) in complexes [28].

TABLE -2

IMPORTANT IR SPECTRAL BANDS OF SCHIFF BASE AND ITS METAL COMPLEXES

L [Cd(L)Cl] [Hg(HL)Cl2] Tentative assignment

3330br -------- 3332br υ(N-O-H)

3410s 3385s 3372s υ(NH)

3275s 3265s 3269s υ(NH2)asym

3169s 3170m 3168s υ(NH2)sym

1707s 1646s 1647s υ(C=O)

1658s 1595s 1594s υ(C=N)azomethine

946m 975m 970m υ(N-N)

608s 608m 609s υ(C=S)

--- 510m 512m υ(M←O)

--- 450m 445m υ(M←N)

--- 393m 389m υ(M-Cl)



The 1H-NMR spectrum of the ligand with its complexes recorded in DMSO- d6 solution with TMS

as a standard. A following structural inference has been taken by comparison of the 1H-NMR

spectrum of the ligand with their metal complexes. The (N-OH) oxime OH signal observed in the

spectrum of the ligand and Hg(II) complex at 11.8 δ is rapidly exchanged with D2O.The presence

of the signal due to (NOH) in this complex indicates that no deprotonation and coordination of

ligand with metal ion through oxygen or nitrogen atom of NOH group took place. The absence

of this signal in Cd(II) complex indicates deprotanation took place and in Cd(II) complex ligand

behave as a tridentate monobasic compound. Two multiplets centered at 2.6-2.7 δ and

doublet at 1.2 δ in the ligand and metal complexes are due to different hydrogen atom of the

tetrahydro-benzothiophene ring. A signal at 7.96 δ due to NH2 proton is unaltered on

complexes and thus clearly indicates the non involvement of the NH2 group in complex

formation. Phenyl group of phenylethylidene is seen as complex multiplets between 7.8-8.0 δ.

A singlet at 9.95 δ is attributed to NH proton which is unaffected in the metal ions complexes.

The electronic absorption spectrum of the ligand in DMSO showed three bands at 270nm,

320nm and 340nm. The first one may be assigned to intra-ligand π→π* transition which is

nearly unchanged on complexation, where as the second and third band may be assigned to the

n→π* and charge transfer transition of the azomethine and carbonyl group [29, 30].It is found

that these band were shifted to lower energy on complexation, indicating participation of these

group in coordination with the metal ions. The electronic spectra of d10 elements generally

consists ligand to metal charge transfer (MLCT) and this is not observed in our complexes

probably due to its overlap with electronic transition of the ligand [31]. The suggested structure

of d10-four coordinated complexes based our evidences and with considering our previous

report on this type of ligands [32] is pseudo-tetrahedral as drawn in Figure-1 and 2.

CdSO

NH

N

NO

ClNH2

Fig. 1. Structure of [Cd(L)Cl] complex



Hg

S

O

NH

NN

OH

Cl

NH2

Cl

Fig. 2. Structure of [Hg(HL)Cl2] complex

Thermal decomposition of the complexes was studied by TG technique in nitrogen atmosphere.

There is no weight loss up to 180oC and this ruled out the presence of any water molecule in

the complexes. The thermogram of Cd(II) complex indicated that it was stable up to 190oC

Thermal decomposition took place in the temperature range of 190-460oC. First TG loss was

observed in 190-330oC with the loss of C8H10S N and C6H5 (theo. 46.46%. exp., 45.82%) followed

by an exotherm at 256oC. Second TG loss was in the temperature range of 350-460oC with a loss

of remaining ligand fragments CONH, C2N2H(O), (Cl) (theo. 27.29%.exp., 26.46%) followed by

an exotherm at 382oC. The residue left was of weight correspond to CdO. (theo. 26.24%. exp.

27.72%). The thermogram of Hg (II) complex indicated that it was stable up to 180oC. Thermal

decomposition took place in the temperature range of 180-510oC. First TG loss was observed in

180-375oC with the loss of C8H10S N and C6H5 (theo. 46.32%.exp. 47.62%) followed by an

exotherm at 294oC. Second TG loss was in the temperature range of 400-510oC with a loss of

remaining ligand fragments CONH, C2N2H, (O) and 2Cl (theo.18.40.%.exp., 18.40%) followed by

an exotherm at 450 oC. The residue left was of weight correspond to HgO. (theo. 35.18%. exp.,

33.98%). The TGA/DTA data of complexes are given in Table-3.

TABLE -3

THERMOGRAVIMETRIC AND DIFFERENTIAL THERMAL ANALYSIS (TGA/DTA) OF COMPLEXES

Complexes Temperature

Range(oC)

Weight loss (%)

Exp.(Theo)

Decomposition Product DTA peak

(oC)

[Cd(L)Cl] 190-330

350-460

>460 (Residue)

45.82(46.46)

26.46(27.29)

27.72(26.24)

C8H10S N+ C6H5

CONH+C2N2H+(O)+Cl

CdO

256(exo)

382(exo)

[Hg(HL)Cl2]

180-375

400-510

>510(Residue)

47.62(46.32)

18.4 (18.40)

33.98(35.18)

C8H10S N + C6H5

CONH+C2N2H+(O)+2Cl

HgO

294(exo)

450(exo)



The kinetic parameters such as activation energies (E*), enthalpy (ΔH*), entropy (ΔS*) and free

energy change of decomposition (ΔG*) were evaluated graphically by employing the Coats-

Redfern relation [33].

(1)

Where Wf is the mass loss at the completion of the reaction, W is the mass loss up to the

temperature T, R is the gas constant, E* is the activation energy in kJmol-1, θ is the heating rate

and (1-(2RT/E*)) ≈ 1. A plot of the left-hand side of Eq. (1) against 1/T gives a slope from which

E* was calculated and A (Arrhenius constant) was determined from the intercept. The entropy

of activation (ΔS*), enthalpy of activation (ΔH*) and the free energy of activation (ΔG*) were

calculated using the following equation:

ΔS*= 2.303 R log (A h/ k T ) (2)

ΔH* =E*- RT (3)

ΔG*= ΔH*- TΔS* (4)

Where k and h are the Boltzmann and Plank constants respectively. The calculated values E*,A,

ΔS*,ΔH*and ΔG* for the decomposition steps are given in Table-4.

TABLE -4

KINETIC DATA ON COMPLEXES

Complexes Temp

Range

(K)

E*

(kJmol-1)

A(s-1) ΔS*

(JK-1mol-1)

ΔH*

(kJmol-1)

ΔG*

(kJmol-1)

r

[Cd(L)Cl] 473-593

633-723

9.85 х101

1.17 х102

4.95х108

1.70х108

-8.32 х101

-9.39 х101

9.42 х101

1.11 х102

1.38 х102

1.73 х102

0.945

0.968

[Hg(HL)Cl2] 463-643

673-793

6.13x102

8.34 х102

2.14х1010

1.809х1013

-5.25 х101

1.52 х100

6.06 х102

8.28 х102

6.38 х102

8.27 х102

0.959

0.910

The correlation coefficient of the Arrhenius plots of the thermal decomposition steps were

found to lie in the range 0.91-0.97, showing a good fit with the linear function. In the present

studies, the numerical values of activation energy, frequency factor and entropy of activation

indicates about smoothness of the feasibility and reaction rate of the initial reactants and



intermolecular stage compounds. The calculated values of the activation energy of the

complexes are relatively low indicating autocatalytic effect of the metal ions on the thermal

decomposition of the complexes[34]. The negative values for entropy of activated complexes

have more ordered or more rigid structure than the reactants or intermediate and the reaction

are slower than normal[34]. These values are comparable with other observation[35]. The order

of stability of complexes on the basis of activation energy is [Hg(HL)Cl2] > [Cd(L)Cl] on the basis

of first and second decomposition stage.

Antimicrobial susceptibility test showed a very high degree of resistance towards the commonly

used antibiotics. The pathogens were found to be Multiple Drug Resistant (Resistant to more

than 3 antibiotics) including 3rd generation Cephalosporins (Ceftazidime, Cefotaxime and

Ceftriaxone). Few MBL producers showed complete resistance to all the tested antibiotics. The

antibiotic resistance profile of the test organism is indicated in Table 5.

TABLE-5

ANTIBIOTIC RESISTANCE PROFILE OF THE TEST ORGANISMS

Organisms Sensitive

Intermediate Resistant

ESBL Producers

Escherichia coli AK, GF

AS, BA, CF, PC, CH,RC, CI, TE, ZN, GM,TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Klebsiella pneumoniae BA, GF

AS, CF, PC, CH,RC, CI, TE, ZN, GM, AK, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Proteus mirabilis AS, CH, AK, GF

PB, ZN BA, CF, PC, RC, CI, TE, GM, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG

Psedomonas aeruginosa CH, AK, GF

AS, BA, CF, PC, RC, CI, TE, ZN, GM, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Citrobacter diversus OX, BA, CH, GM

TE, AK, GF AS, CF, PC, CH,RC, CI, ZN, GM, TT, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

MBL Producers

Escherichia coli CH AK AS, BA, CF, PC, RC, CI, TE, ZN, GM, GF, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB



Klebsiella pneumoniae CH AK AS, BA, CF, PC, CH,RC, CI, TE, ZN, GM, AK, GF, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Proteus mirabilis AS, BA, CF, PC, CH,RC, CI, TE, ZN, GM, AK, GF, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Psedomonas aeruginosa AS, BA, CF, PC, CH,RC, CI, TE, ZN, GM, AK, GF, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Citrobacter diversus PB, CL, TE AS, BA, CF, PC, CH, CI, TE, ZN, GM, AK, GF, TT, OX, RP, ZX, CB, NA, NX, AG, CU, CP, FG, PB

Key:

TT -Ticarcillin/clavulanic acid, OX- Oxytetracycline, RP – Ceftriaxone, ZX – Cefepime,

CB – Cefuroxime, NA - Naladixic acid, NX- Norfloxacin, AG - Amoxycillin/clavulanic acid,

CU – Cefadroxil,CP - Cefoperazone, FG- Ceftazidime, PB - Polymixin B, AS – Ampicillin,

BA - Co-trimaxazole, CF – Cefotaxime, PC- Pipperacillin, CH – Chloramphenicol,

RC – Ciprofloxacin, CI – Ceftizoxime, TE – Tetracycline, ZN – Ofloxacin, GM – Gentamicin, AK –

Amikacin, GF – Gatifoxacin

The effect of metal complexes on these test isolates are shown in Table 6 (Figure 3) and 7

(Figure 4) below. Control well having ethanol (solvent) did not show any zone of inhibition

against the test organisms. However metal complexes showed considerable zones of inhibition

in its complex form as compared to ligand. Comparatively Cadmium complexes showed a better

activity than Mercury complexes. Similar results has been observed in another studies carried

out using other complexes of mercury and cadmium [14,36]. The antibacterial activity of these

complexes can be attributed to its lipophilic nature which may allow easy binding and

penetration of the complex in the cellular membrane of the pathogens which is made up of

lipopolysachharides. Also, as the positive charges of the metal are partially shared with the

donor atoms present in the ligands and there is possible π-electron delocalization over the

metal complex formed. This increases the lipophilic character of the metal chelate and favors

its permeation more efficiently through the lipid bi-layer of the microorganism, thus destroying

them more forcefully. The other factors like solubility and bond length between the metal and

ligand may also increase the activity [37].



TABLE 6

EFFECT OF METAL COMPLEXES ON ESBL PRODUCERS

ESBL producers Cadmium Mercury

100µg/µl 200µg/µl 100µg/µl 200µg/µl

E.coli 13 16 11 12

K.pneumoniae 12 16 11 12

P.mirabilis 13 17 - 11

P.aeruginosa 13 16 - 12

C.diversus 12 15 11 12

Fig. 3. EFFECT OF METAL COMPLEXES ON ESBL PRODUCERS

TABLE 7

EFFECT OF METAL COMPLEXES ON MBL PRODUCERS

MBL producers Cadmium Mercury

100µg/µl 200µg/µl 100µg/µl 200µg/µl

E.coli 12 15 - 10

K.pneumoniae 15 16 - 11

P.mirabilis 11 13 - 11

P.aeruginosa 13 15 - 11

C.diversus 12 15 11 12

0 2 4 6 8

10 12 14 16 18

Cadmium 100µg/µl

Cadmium 200µg/µl

Mercury 100µg/µl

Mercury 200µg/µl



Fig. 4. EFFECT OF METAL COMPLEXES ON MBL PRODUCERS

CONCLUSION:

From the present investigation it has been observed that a ligand = 2-amino-N'-[(1E,2Z)-2-

(hydroxyimino)-1-phenylethylidene]-4,5,6,7-tetrahydro-1-benzothiophene-3-carbohydrazide

form a complex with metal ions like Cd(II) and Hg(II). The data suggested that the ligand

behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor

atom sequentially with Cd(II) ion where as with Hg(II) ion behaves as bidentate ligand. The

physico-chemical data suggested tetrahedral geometry of complexes. The thermal investigation

(studied by TG/DTG techniques) shows that obtained complex decomposes progressively, and

the final product of the thermal decomposition is metal oxides, which through its percentage

confirms the empirical formulae of the new complexes prepared. The metal complexes were

also proved to exhibit antibacterial activity against drug resistant pathogens.

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INTERNATIONAL JOURNAL OF PHARMACEUTICAL … 865.pdf · · 2014-10-26was studied using Kirby Bauer method using 24 commonly used antibiotics in case ... The metal complexes were

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