available online through research articlezn(ii) complexes in the range of 12.56 – 14.89 ohm –1...

P. Subramanian* et al. /International Journal Of Pharmacy&Technology

IJPT | Oct-2012 | Vol. 4 | Issue No.3 | 4630-4644 Page 4630

ISSN: 0975-766X CODEN: IJPTFI

Available Online through Research Article www.ijptonline.com

SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL STUDI ES OF Cu(II), Ni(II), Mn(II) and Zn(II) SCHIFF BASE COMPLEXES DERIVED FRO M 2-HYDROXY

NAPHTHALDEHYDE AND 1,8-DIAMINONAPHTHALENE 1M. Sakunthala and 2P. Subramanian*

1 Department of Chemistry, Government Arts College for Women, Salem-8, Tamil Nadu. 2 Department of Chemistry, Government Arts College, Salem-7, Tamil Nadu.

Email: [email protected] Received on 18-07-2012 Accepted on 31-07-2012

Abstract

The symmetrical tetra-dentate Schiff base complexes were prepared by the reaction of 2-hydroxy

naphthaldehyde and 1,8-diaminonaphthalene in 2:1 molar ratio. The ligand and its complexes with Cu(II), Ni(II),

Mn(II) and Zn(II) ions were characterized by elemental analysis, molar conductance, infrared, electronic spectra, cyclic

voltammetry, thermal, Magnetic and EPR studies. Furthermore, antibacterial activity of representative complexes was

also investigated. The molar conductance value of all metal complexes in DMF solvent indicates the non-electrolytic

nature. In IR spectra, the comparison of shift in frequency of the complexes with the ligand reveals the coordination of

donor atom to the metal atom. The electronic, magnetic and EPR spectra of the metal complexes provides information

about the geometry of the complexes and are in good agreement for the proposed square planar geometry for Cu(II),

Ni(II), Mn(II) and Zn(II) complexes. The free ligands and their metal complexes were screened for their antimicrobial

activities against pathogenic bacteria like staphylococcus aureus, Escherichia coli and Klebsilla pneumonia. The

activity data show that the Cu(II), Ni(II), Mn(II) and Zn(II) complexes are more potent antimicrobials than the parent

Schiff base ligands against microorganisms.

Keywords: Schiff base, 1,8-diaminonaphthalene, 2-hydroxy1-naphthaldehyde, Antimicrobial activity.

1. Introduction

Schiff bases complexes have remained an important and popular area of research due to their simple synthesis,

versatility, and diverse range of applications [1,2]. Thus, Schiff bases have played a marvelous role in the development



of coordination chemistry. Schiff base metal complexes had been a widely studied subject due to their industrial and

biological applications [3]. Because of new interesting applications found in the field of pesticides and medicine, the

metal complexes with tetra-dentate N2O2 types had attracted the attention of chemists [4, 5].

The Cu(II) and Ni(II) complexes are well known to accelerate drug action and the efficiency of a therapeutic

agent can often be enhanced upon coordination with a metal ion. The pharmacological activity has been found to be

highly dependent on the nature of the metal ion and the donor sequence of the ligands, with different ligands showing

widely dissimilar biological properties. The copper (II) complexes have aroused extensive interest due to their

importance in biological processes and in inorganic material science [6]. The coordination geometry around the Cu(II)

ion plays a major role as well in the redox-mediated formation of reactive oxygen species. The activation of molecular

oxygen by a mononuclear Cu(II) complex in the presence of DNA is expected to lead to the abstraction of a

proton/hydrogen from the sugar backbone or from the bulk solvent. The coordination chemistry of manganese in the

+2, +3 and +4 oxidation states is receiving considerable attention due to the biological importance of these ions [7].

The synthesis and characterization of manganese coordination complexes to model the structure, reactivity and

spectroscopy of manganese in its various oxidation states, with various ligand types and nuclearities, has contributed

substantially to our understanding of the role and mechanism of manganese enzyme.

This study presents the synthesis and characterization of some new Cu(II), Ni(II), Mn(II) & Zn(II) complexes

with tetra-dentate Schiff bases derived from 2-hydroxy naphthaldehyde and 1,8-diaminonaphthalene. The synthesised

complexes have been characterized by elemental analysis, molar conductance, infrared, electronic spectra, cyclic

voltammetry, thermal, Magnetic and EPR studies.

2. Experimental

Materials and physical measurements

Metal salts, 2-hydroxy naphthaldehyde and 1, 8-diaminonaphthalene were purchased from Aldrich. Ethanol,

DMSO and DMF were used as solvents purchased from Loba chemicals. The solvents and reagents with analytical

grade were obtained commercially and used without further purification. The Elemental analysis was performed using

Carlo-Eraba 1106 instrument. Molar conductances of the complexes in DMF solution were measured with ELICO CM

185 conductivity Bridge. The Infrared spectra were recorded on the SHIMADZU model spectrometer using KBr disc.



Electronic absorption spectra in the UV-Visible range were recorded on Perkin Elmer Lambda-25 between 200-800 nm

by using DMF as the solvent. ESR spectra were recorded on a Varian JEOL-JES-TE100 ESR spectrophotometer at X-

band microwave frequencies for powdered samples at room temperature. Magnetic susceptibility data were collected

on powdered sample of the compounds at room temperature with PAR155 vibrating sample magnetometer. Thermal

studies were carried out in the 100–900°C range using an SDT Q600 V20.9 Build 20 model thermal analyzer.

Synthesis of Ligand

The symmetrical tetra-dentate Schiff base ligand was prepared according to the literature method. To an ethanolic

solution of 2-hydroxy naphthaldehyde and ethanolic solution of 1,8-diaminonaphthalene was added in dropwise. The

reaction mixture was kept on water bath for refluxtion. It was refluxed for 2 hours. Yellowish brown colour solid was

separated and was filtered off, washed with 5 ml of cold ethanol and then dried in air.

Synthesis of Metal Complexes

All the new Schiff base complexes were prepared by the same general procedure with stoichiometric amount of

ligand and metal salts in a 1:1 mole ratio. To an ethanolic solution of Schiff base ligand metal salt was added. The

reaction mixture was refluxed for about 2 hrs on hot water bath. The reaction mixture was cooled, filtered and left in a

petridish to allow the solvent to evaporate slowly. The complex was separated out.

Cyclic voltammetry

All voltammetric experiments were performed with a CHI 760 electrochemical analyzer, in single compartmental

cells using tetrabutylammonium perchlorate as a supporting electrolyte. The redox behavior of the complexes has been

examined in a scan rate of 0.1 Vs−1 in the potential range +1.2 to –2.0 V. A three-electrode configuration was used,

comprising a glassy carbon electrode as the working electrode, a Pt-wire as the auxiliary electrode, and an calomel

electrode as the reference electrode. The electrochemical data such as cathodic peak potential (Epc) and anodic peak

potential (Epa) were measured.

Antimicrobial activity

The antibacterial activity of the complexes of Cu(II), Ni(II), Mn(II) and Zn(II) were checked by the disc diffusion

technique [8]. This was done on Gram negative bacteria like Klebsiella pneumoniae, Escherichia coli and Gram


IJPT | Oct-2012 | Vol. 4 | Issue No.3 | 4630-4644 633

positive bacteria Staphylococcus aureus at 37°C. The disc of Whatmann no.4 filter paper having the diameter 8.00 mm

were soaked in the solution of compounds in DMSO (1.0 mg cm-1). After drying it was placed on nutrient agar plates.

The inhibition areas were observed after 36 hours. DMSO was used as a control and Streptomycin as a standard.

3. Result and discussion

Elemental composition

The elemental analysis data were compared with that of the formulation, which gives good agreement with the

proposed formula. The elemental analysis data of the complexes were produced by Table 1.

Table-1: Analytical and physical data of the Schiff base metal complexes.

Compounds

Calculated (Found) (%) ΛM (Ohm–1 cm2

mol–1) C H N Metal

(C32H22N2O2) 82.40 (82.35)

4.72 (4.70)

6.00 (5.54)

-- --

[Cu(C32H20N2O2)] 72.72

(72.78)

3.78

(3.75)

5.30

(5.32)

12.12

(12.13)

13.54

[Ni(C32H20N2O2)] 73.56

(73.53)

3.83

(3.80)

5.36

(5.32)

11.11

(11.14)

14.32

[Mn(C32H20N2O2)] 74.13

(74.11)

3.86

(3.82)

5.40

(5.41)

10.42

(10.40)

14.89

[Zn(C32H20N2O2)] 72.58

(72.51)

3.78

(3.74)

5.29

(5.27)

12.28

(12.26)

12.56

Conductivity studies

The molar conductance of the complexes was an aid for proposing their formulas. Conductivity measurements

were carried out in 10−3 mol dm−3, DMF at 30˚C. The molar conductance values of the Cu(II), Ni(II) and Mn(II) and



Zn(II) complexes in the range of 12.56 – 14.89 Ohm–1 cm2 mol–1 (Table 2) which indicates the non-ionic nature of

these complexes and they are considered as non-electrolytes [9].

Table-1: Infrared spectral data for Schiff base metal complexes.

Compounds (C=N)

(cm−1)

C=C

(cm−1)

(M−N)

(cm−1)

(M−O)

(cm−1)

(C32H22N2O2) 1622 1517 -- --

[Cu(C32H20N2O2)] 1600 1460 468 526

[Ni(C32H20N2O2)] 1600 1519 480 511

[Mn(C32H20N2O2)] 1590 1500 468 511

[Zn(C32H20N2O2)] 1608 1537 455 520

IR spectra

A strong band is observed in the free ligands around 1622 cm-1, characteristic of azomethine (C=N) group [10].

Coordination of the Schiff base to the metal through azomethine nitrogen atom is expected to reduce the electron

density in the azomethine link and lower the (C=N) absorption frequency. In the spectra of all new complexes, the band

due to (C=N) showed a negative shift to 1590–1608 cm−1, indicating coordination of the azomethine nitrogen to metal

atom [11]. Another medium intensity band around 3385 cm−1 cm in the free ligands due to the (OH) was absent in the

complexes, indicating deprotonation of the Schiff bases prior to the coordination. The various absorption bands in the

region 1460-1537 cm−1 may be assigned due to υ(C=C) aromatic stretching vibrations of the 2-hydroxynaphthaldehyde

and 1, 8-diaminonaphthalene ring.

The infrared spectra show bands in the region 450-500 cm−1 corresponding to υ(M-N) vibrations [12]. The

presence of bands in all the complexes in the region 455-480 cm−1 orginates from the (M-N) azomethine vibration



modes and identifies coordination of azomethine nitrogen and also presence of bands at 511-526 cm−1 indicates that

υ(M-O) vibrations.

Electronic spectra

The geometry of the metal complexes has been deduced from the electronic spectra of the complexes. Electronic

spectra of all the complexes were recorded in DMF medium in Table 3. The peaks obtained in the range of 255-277 nm

was assigned to the intra ligand charge transfer transition (π→ π*). An intense peak in the range of 310-350 nm was

due to ligand-to-metal charge transfer transitions. The bands are indicative of benzene and other chromophore moieties

present in the complexes.

Table-3: UV–Visible data of Schiff base metal complexes.

Complexes

Absorption nm (cm-1)

π→ π* n→ π* L→ M CT

d-d

(C32H22N2O2) 256 310 -- --

[Cu(C32H20N2O2)] 262

324

416

550

[Ni(C32H20N2O2)] 277

350

421

536, 644

[Mn(C32H20N2O2)] 260

317

434

519, 626, 691

[Zn(C32H20N2O2)] 255 318 425 --

The copper(II) complex shows a broad absorption peak at 550 nm arises due to the d-d transition 2B1g → 2A1g

suggest that the copper ion exhibits a square planar geometry [13]. According to the literature data, the principal

feature of square planar nickel(II) complexes is the presence of three well-defined bands [14]. We have also observed

two weak intensity bands of the mononuclear Ni(II) complex at 536, 644 nm corresponding to 1A1g → 1A2g, 1A1g →



1B1g transitions, respectively. The electronic spectra of mononuclear Mn(II) complexes exhibit three weak intensity

absorption bands at 519, 626, 691 nm. These bands may be assigned to the transitions 6A1g → 4T1g (4G), 6A1g → 4Eg

(4G), 6A1g → 4Eg (4D). Which may be expected to arise from the Mn(II) ions [15] in Square planar geometry.

No transitions were observed in the visible region for the Zn(II) complex consistent with the d10 configuration of

the Zn2+ ion. This complex is also found to be diamagnetic as expected for the d10 configuration.

Cyclic Voltammetry

The electrochemical behaviour was studied by cyclic voltammetry in DMSO containing 10−1 M tetra(n-butyl)

ammonium perchlorate over the range of 1.2 to −2.0 V. The electrochemical data of the complexes are summarized in

Tables 4. (reduction) and 5(oxidation).

[Cu(C32H20N2O2)] complex shows quasireversible reduction waves. Controlled potential electrolysis was carried

out at 100 mVs−1 and the experiment reports that each couple correspond to one electron transfer process. So, the

processes are assigned as follows.

CuII→CuI

The [Cu(C32H20N2O2)] complex show a quasireversible oxidation waves, which is assigned as a Cu(III)/Cu(II) couple. The

∆Ep values are suggest the each couple was quasireversible. The E1/2 values indicate that each couple corresponds to one

electron transfer process.

A typical cyclic voltammograms of the complex [Ni(C32H20N2O2)] shows quasireversible reduction waves. The ∆Ep

values suggest the existence of a quasireversible couple. The E1/2 values indicate that each couple corresponds to one electron

transfer process. Tables 4 and 5 represent the electrochemical data of [Ni(C32H20N2O2)] complex in cathodic and anodic

potential, respectively. Controlled potential electrolysis was also carried out and the experimental reports that each couple

correspond to one electron transfer process, as follows:

NiII→Ni I

The cyclic voltammograms of nickel (II) complexes obtained at positive potential region show one electron

transfer waves. The oxidation process is also quasireversible in nature. The oxidation process can be assigned as

follows:



Ni II →Ni III

The [Mn(C32H20N2O2)] complex shows reduction waves. The ∆Ep values suggest the existence of a

quasireversible couple. The E1/2 values indicate that each couple corresponds to one electron transfer process.

Controlled potential electrolysis was also carried out and the experimental reports that each couple correspond to one

electron transfer process, as follows:

MnIII →MnII

The obtained oxidation peak at the positive potential side indicated that the processes take place on the metal

center of the complex Mn(II). This peak describes a one-electron oxidation of Mn(II)/Mn(III).

Table-4: Thermoanalytical data of the Schiff base metal complexes.

Com

plex

es

TG

ran

g

(o C)

Estimated

(Calculated) (%)

Assignment

Metallic residue Mass

loss

Total mass

loss

L

141-206

206-275

44.00

(43.28)

56.00

(55.78)

90.00

(99.06)

Loss of naphthalene groups

Loss of aromatic ligand groups. --

1

200-700

47.12

(47.15)

--

Loss of naphthalene groups and

aromatic ligand groups.

Decomposition is

in progress

2

225-450

53.74

(52.98)

--



Decomposition is

in progress

3

150-775

65.13

(65.70)

--



MnO residue

4

150-525 45.26

(45.55)



Decomposition is

in progress



Table-5: Electrochemical data Schiff base metal complexes in DMF medium (reduction).

Complexes Epc (V) Epa (V) E1/2 (V) ∆E (mV)

[Cu(C32H20N2O2)] −1.42 −0.63 −1.02 790

[Ni(C32H20N2O2)] −0.90 −0.67 −0.78 230

[Mn(C32H20N2O2)] −1.05 −0.52 −0.78 530

[Zn(C32H20N2O2)] −0.95 −0.40 −0.67 550

Thermal analysis

The thermogram of ligand with the molecular formula (C32H22N2O2) shows two decomposition steps within the

temperature range from 141-275°C. The first step occurs within the temperature range 141–206°C with an estimated

mass loss 44.00% (calculated mass loss = 43.28) which is reasonably accounted for the loss of naphthalene groups. The

second step occurs within the temperature range 206–275°C with an estimated mass loss of 56.00% (calculated mass

loss = 55.72%), which is reasonably accounted for the loss of aromatic ligand groups.

The TG curves of the copper(II) complex with the molecular formula [Cu(C32H20N2O2)] is thermally

decomposed in single step in the temperature range from 200-700°C with an estimated mass loss 47.12% (calculated

mass loss = 47.15%), which is attributed to the loss of naphthalene groups and aromatic ligand groups. The last step

did not finish completely. Therefore, last decomposition residue was not determined.

The TG curves of the nickel(II) complex with the molecular formula [Ni(C32H20N2O2)] is thermally

decomposed in single step in the temperature range from 225-450°C with an estimated mass loss 53.94% (calculated

mass loss = 52.78%), which is attributed to the loss of naphthalene groups and aromatic ligand groups. The last step

did not finish completely. Therefore, last decomposition residue was not determined.

The TG curves of the manganese(II) complex with the molecular formula [Mn(C32H20N2O2)] is

thermally decomposed in single step in the temperature range from 150-775°C with an estimated mass loss 65.13%

(calculated mass loss = 65.70%), which is attributed to the loss of naphthalene groups and aromatic ligand groups. The

last step is MnO residue.



The TG curves of the Zinc(II) complex with the molecular formula [Zn(C32H20N2O2)] is thermally decomposed

in single step in the temperature range from 150-525°C with an estimated mass loss 45.26% (calculated mass loss =

45.55%), which is attributed to the loss of naphthalene groups and aromatic ligand groups. The last step did not finish

completely. Therefore, last decomposition residue was not determined.

Magnetic moment studies

The magnetic susceptibility measurements provide information regarding the structure of the metal complexes.

Magnetic susceptibility was determined using a magnetic susceptibility balance. The magnetic moment data of the

solid-state complexes were recorded at room temperature. The magnetic susceptibility measurements show that the

complexes are paramagnetic at ambient temperature. The magnetic moment values of copper(II) complex is 1.70 B.M.

indicates square planar geomentry and Manganese(II) complex is 5.87 indicates square planar geometry [16].

EPR spectra

The EPR spectra of complexes provide information of importance in studying the metal ion environment. The

EPR spectra of the [Cu(C32H20N2O2)] and [Mn(C32H20N2O2)] Schiff base complexes recorded on powder samples with

room temperature, on X-band at frequency 9.3 GHz under the magnetic field strength 4000G.

The EPR spectrum of the [Cu(C32H20N2O2)] complex shows a broad signal with giso at 1.9998, which is

consistent with an square planar geometry. The broadening of this signal might be due to dipolar interactions,

indicating lowered site symmetry suggesting that the unpaired electron resides mainly in the dx2-dy2 orbital. This

indicates a considerable exchange interaction in the complex [17].

In a similar fashion, a single unresolved signal observed in the [Mn(C32H20N2O2)]. In the present case, the giso

value is found to be 2.0002, which can be corroborated with a square planar environment.

Antimicrobial activity

The synthesized schiff base ligand and its metal complexes were tested against the bacteria species like Klebsiella

pneumoniae, Escherichia coli, Staphylococcus aureus. The comparison of biological activities of the ligand is

complexes show the following results. The free ligand having some biological activity because of nitrogen present in

the ligand molecule. The free ligand and metal complexes show moderate activity because of chelation [18]. The



minimum inhibitory concentration (MIC) values of the investigated compounds are summarized in tables 7. The values

indicate that most complexes have higher antimicrobial activity than the free ligand. Such increased activity of the

metal chelates can be explained on the basis of chelation theory. On chelation, the polarity of the metal ion will be

reduced to a greater extent due to the overlap of the ligand orbital and partial sharing of the positive charge of the metal

ion with donor groups. Further, it increases the delocalization of π-electrons over the whole chelate ring and enhances

the penetration of the complexes into lipid membranes and blocking of the metal binding sites in the enzymes of

microorganisms. These complexes also disturb the respiration process of the cell and thus block the synthesis of

proteins, which restricts further growth of the organism [19].

Table-6: Electrochemical data of Schiff base metal complexes in DMF medium (oxidation).

Complexes Epc (V) Epa (V) E1/2 (V) ∆E (mV)

[Cu(C32H20N2O2)] 0.35 0.60 0.47 250

[Ni(C32H20N2O2)] 0.17 0.40 0.28 230

[Mn(C32H20N2O2)] 0.69 0.95 0.82 260

[Zn(C32H20N2O2)] 0.58 0.79 0.68 210

Table-7: Antibacterial activity of the Schiff base metal complexes.



Figure-1: Synthesis of Schiff base ligand.

Figure-2: Synthesis of Schiff base metal complexes.

IJPT | Oct-2012 | Vol. 4 | Issue No.3 | 4630-

Figure 3: The EPR spectrum of the [Cu(C

Figure 4: The EPR spectrum of the [Mn(C

0

5

10

15

20

1 2

Zo

ne

of

Inh

ibit

ion

(m

m)

Klebsiella pneumoniae


-4644

[Cu(C32H20N2O2)] complex at room temperature, Frequency = 9.41266 GHz.

[Mn(C 32H20N2O2)] complex at room temperature, Frequency = 9.41266 GHz.

25 μl

75 μl

23

45

Compounds

Klebsiella pneumoniae

25 μl

50 μl

75 μl

100 μl

et al. /International Journal Of Pharmacy&Technology

Page 4642

complex at room temperature, Frequency = 9.41266 GHz.

at room temperature, Frequency = 9.41266 GHz.

25 μl

50 μl

75 μl

100 μl

IJPT | Oct-2012 | Vol. 4 | Issue No.3 | 4630-

Figure 5: Difference between the antimicrobial activities of the trinuclear

[Cu(C32H20N2O2)], 3. [Ni(C32H20N2O2)], 4. [Mn

Conclusion

In this report, coordination chemistry of a Schiff

naphthaldehyde and 1, 8-diaminonaphthalene

synthesized using the Schiff base ligand and characterized by spectral and analytical

square–planar geometry has been assigned to the complexes

than the ligand.

0

5

10

15

20

1 2

Zo

ne

of

Inh

ibit

ion

(m

m)

0

5

10

15

20

1 2

Zo

ne

of

Inh

ibit

ion

(m

m)

Staphylococcus aureus


-4644

Difference between the antimicrobial activities of the trinuclear Schiff base metal complexes

[Mn(C32H20N2O2)], 5. [Zn(C32H20N2O2)].

In this report, coordination chemistry of a Schiff base ligand, obtained from the reaction of

diaminonaphthalene is described. Cu(II), Ni(II), Mn(II) and Zn(II)

base ligand and characterized by spectral and analytical data. Based on these data, a

has been assigned to the complexes. The metal complexes have higher antimicrobial

25 μl

75 μl

2 34

5

Compounds

Escherichia coli

25 μl

50 μl

75 μl

100 μl

25 μl

75 μl

2 34

5

Compounds

Staphylococcus aureus

25 μl

50 μl

75 μl

100 μl

et al. /International Journal Of Pharmacy&Technology

Page 4643

metal complexes.1. Ligand, 2.

he reaction of 2-hydroxy1-

Mn(II) and Zn(II) complexes have been

data. Based on these data, a

The metal complexes have higher antimicrobial activity

100 μl



References

1. M.K. Taylor, J. Reglinski, D. Wallace, Polyheron 23 (2004) 3201.

2. S. Yamada, Coordin. Chem. Rev. 192 (1999) 537.

3. Z. M. Zaki, S. S. Haggag and A. A. Soayed, Spectroscopy Letters, 31 (1998) 757.

4. C. K. Bhaskare and P. P. Hankare, J. Ind. Chem. Soc., 72 (1995) 585.

5. W. S. Sawodny and M. Riederer, Angew. Chem., Int. Edn. Engl., 16 (1977) 859.

6. E. L. Hegg, S. H. Mortimore, C. L. Cheung, J. E. Huyett, D. R. Powell and J. N. Burstyn, Inorg. Chem., 38 (1999)

2961.

7. V. L. Pecoraro, M. J. Baldwin and A. Gelaso, Chem. Rev. 94 (1994) 807.

8. S. Chandra, L.K. Gupta, Spectrochim. Acta Part A, 2004, Vol 60, pp1563-1571.

9. G. G. Mohamed, M. M. Omar, A. A. Ibrahim, Spectrochim. Acta Part A., 75, 678 (2010).

10. R . Ramesh, K. Natarajan, Synth. React. Inorg. Met-Org. Chem. 26(1996) 47.

11. R . Ramesh, N. Dharmaraj, R. Karvembu, K. Natarajan, Ind. J.Chem. 39A (2000) 1079.

12. S. Chandra, R. Kumar, Transition. Met. Chem., 29, 269 (2004).

13. F. Akagi, Y. Michihiro, Y. Nakao, K. Matsumoto, T. Sato, W. Mori, Inorg. Chim. Acta., 357, 684 (2004).

14. L. V. Ababei, A. Kriza, A. M. Musuc, C. Andronescu, E. A. Rogozea, J. Therm. Anal. Calorim, doi.

10.1007/s10973-009-0560-z (2009).

15. S. Chandra, S. D. Sharma, Transition. Met. Chem., 27, 732 (2002).

16. S. Djebbar-Sid, O. Benali-Baitich, J. P. Deloume, Transition. Met. Chem., 23, 443 (1998).

17. S. Khan, S. A. A. Nami and K. S. Siddiqi, Spectrochim. Acta A., 68 (2007) 269.

18. N. Raman, J. Dhaveethu Raja and A. Sakthivel, J. Chem. Sci., 119 (2007) 303.

19. N. Dharmaraj, P. Viswanathamurthi, K. Natarajan, Trans. Met. Chem., 26 (2001) 105.

Corresponding Author:

P. Subramanian*

Email: [email protected]

available online through research articlezn(ii) complexes in the range of 12.56 – 14.89 ohm –1...

Documents