SYNTHESIS AND STRUCTURAL CORRELATION TWO COPPER(II)COMPLEXES

SYNTHESIS AND STRUCTURAL CORRELATION TWO

COPPER(II)COMPLEXES

Jeeva, J.* and Ramachandramoorthy, T.

PG and Research Department of Chemistry, Bishop Heber College (Autonomous),

Tiruchirappalli-620 017, Tamil nadu, India.

ABSTRACT

Copper(II) complexes with 4- hydroxypyridine and cyanate ion /

thiocyanate ion were synthesised in microwave field using a

microwave oven. They were characterized and these two complexes

were compared for their structural and biological activities.

KEY WORDS: far Copper(II)Complex, 4 Hydroxypyridine, Thermogram, Antimicrobial.

INTRODUCTION

Many branches of science and technology have close association with

the development of chemistry and particularly coordination chemistry

[1]

With the development in progress many compounds were synthesized and studied for their

properties. Copper complex are few such compound prepared due to its involvement in all

fields of chemistry. One such compound 1-hydorxyethylienediphosphoric acid (HEDP) has

been known for the past many years by Chemists[2-4]. Other compounds such as cytochrome

oxidase consisting of heme and copper in the ratio of 1:1 and tryrosinases were first such

enzymes in which copper was detected to be its essential constituent. Another important

haemocyanin is a cupro protein found in mammals and functions as oxygen carrier.

MATERIALS AND METHODS

Copper nitrate used was of AnalaR grade. The solvents used viz., DMSO, acetonitrile, DMF, methanol, ethanol were also of AnalarR grade and used as such.

4-hydroxypyridine was purchased from Alfa Aesar company.

Article Received on 05 July 2014,

Revised on 29 July 2014, Accepted on 24 August 2014

*Correspondence for Author Dr. Jeeva, J

PG and Research Department of

Chemistry, Bishop Heber College

(Autonomous),

Tiruchirappalli-620 017, Tamil nadu, India.

INSTRUMENTAL ANALYSES

The following instrumental analysis were carried out for the complexes. Elemental analysis

was done using elementar Vario EL III. Metal estimation for copper was done

volumetrically. Electrical conductivity measurements were carried out in acetonitrile

medium (10-3M) at 300C using a digital conductivity bridge (Equiptronics, EQ660). The

magnetic susceptibility measurements were done by Lakeshore VSM-7410. Electronic

spectra were recorded by solid state diffused reflectance method. IR spectra were recorded

using Perkin Elmer Spectrum RXI spectrometer in 4000-400 cm-1 range with KBr pellet

technique. Far – IR spectra were recorded using Bruker 3000 Hyperion spectrometer. The

cyclic voltammetric measurement were done by Princeton Applied Research, model-versa

stat mc. Thermal analysis were done in Perkin Elmer, Diamond TGA/DTA instrument. EPR

spectra were taken using Miniscope EPR Spectrometer. Antimicrobial activities were done

using agar well diffusion method. Antioxidantal measurements were carried out by DPPH

radical scavenging method.

SYNTHESIS OF COMPLEXES

To a solution of copper nitrate 1.00 g each (4.2 mmol and 4.2 mmol respectively) in

methanol, 0.79g(8.32mmol) of 4-hydroxypyridine in methanol was added in drops with

constant stirring. The mixture was irradiated in a microwave oven (IFB – 25PG IS) at

900 W for about 10 seconds. Then sodium cyanate 0.54g and 0.83g (8.4 mol each)

respectively in ethanol was added and the mixture was irradiated for about 10 seconds in

microwave oven. The preceipitated green and yellowish green coloured complexes were

filtred, washed with ethonal, driedand kept in air - tight glass containers.

RESULTS AND DISCUSSION

On the basis of elemental analysis, the composition of metal complexes were arrived at

percentage of various elements helps to formulate the complexes. Low molar conductane

values indicate the complexes are non electrolytes[5]. The values are given in Table 1.

Table 1 Analytical Data of Complexes S.

No. Complex Colour

Yield %

Elemental Analysis

 (ohm-1 Cm2 mol-1)

C% H% N% S% Metal%

1 [Cu(OCN)2 (4-HP)2] Green 58.6

42.65 (42.67)

2.96 (2.98)

16.56

(16.58) -

17.15

(17.17) 70.2

2 [Cu(SCN)2 (4-HP)2] Yellowi

sh green 48.7

38.94 (38.96) 2.70 (2.72) 15.12 (15.14) 17.31 (17.33) 18.80

Theoritical values are given in paranthesis

Magnetic Susceptibility

The observed magnetic moments of these two copper(II)complexes agree with the presence

of one unpaired electron, with the value of 1.76 BM[6]. The value for cyanate complex is

1.81 BM and for thiocyanate complex is 1.83 BM.

Electronic Spectra

The absorption band at 234 nm and 239nm in both the complexes indicate the charge transfer

spectral frequencies[7]. Strong absorption bands at 528 nm and 504nm for cyanate and

thiocyanate complexes is due to transitions 2Eg  2B1g, 2B1g  2B1g, 2 A1g  2 B1g which

gives an indication of the structure as tetragonally distorted octahedral for these two

complexes (7) Table 2.

Fig. 1: UV – Visible Spectrum of [Cu(OCN)2 (4-HP)2]

Table 2: UV – Visible Spectral Data of Complexes

S.No. Complex  max(nm) Assignment Probable

geometry

1 [Cu(OCN)2 (4-HP)2]

234

528

Charge Transfer 2_{Eg } 2

B1g 2

B2g 2B1g 2

A1g  2B1g

Tetragonally distorted octahedral

2 [Cu(SCN)2 (4-HP)2]

239

504

Charge Transfer 2_{Eg } 2

B1g 2_{B2g } 2

B1g 2_{A1g } 2

B1g

Cyclic Voltammetric Study

This study is done to monitor spectral and structural changes accompanying electron transfer

[9]

. The reduction of copper(II) is reversible. Ipa / Ipa is equal to unity indicates the

chemical reversibility of the redox change and the value is also an indication of the

reversibility of the reaction[10] Table 3.

Fig. 2 Cyclic Voltammogram of [Cu(OCN)2 (4-HP)2)]

Table 3 Cyclic Voltammetric Values Of Complexes

Sl. No. Complex Epc1(Epc2), Epc2 (Epc2) Ep1a Ep26 Epal(Epa/2)

1 [Cu(OCN)2 (4-HP)2)] -0.76(0.69), -1.57(-1-49) -0.09 -0.14 -0.59(-0.67)

2 [Cu(SCN)(4-Hp)2] -0.87(-0.76) -0.09 - -0.62(-0.75)

INFRARED SPECTRA

In the infrared spectra of the ligand 4-HP a characteristic band is observed at 3400 cm-1 for

phonetic –OH, 2430 cm-1 for aromatic C-H and 1377cm-1 for C=N [11]. The displacements

of the band by 10-30cm-1 towards lower region in complexes has been attributed to the

formation of co-ordination bond between 4-HP pyridine ring nitrogen and metal ion[12].

Such observations have also been made in case of cyanate ion complex and thiocyanate ion

Fig. 3 IR Spectrum of [Cu(OCN)2(4-HP)2]

Table 4 Infrared Spectral Data of The Complexes Cm-1 S.

No. Compound -OH

C-H Aromatic

ring

C=N

OCN Symmetric

Stretching

OCN Asymmetric

Stretching

SCN Symmetric Stretching

SCN Assymmetric

stretching

1 4-HP 3400 2930 1377 - - - -

2 [Cu (OCN)2(4-HP)2] 3376 2998 1411 1251 2110 - -

3 [Cu (SCN)2(4-HP)2] 3407 2971 1375 - - 1217 2153

FAR INFRARED SPECTRA

In complex [Cu(OCN)2(4-HP)2] the ligating N atom of metal nitrogen bond frequency

(M-NCO) values are at 375cm-1 and 523cm-1. In [Cu(SCN)2 (4-HP)2] the ligating N atom of

(M-NCO) values are at 488cm-1. This is well agreed with the reported value [13]. Thus the

ligating atom is confirmed Table 5.

Table 5 Far Infrared Spectra Data Of Complexes Cm-1 S.

No. Complex

Metal Nitrogen

Metal –Nitrogen Stretching

frequency

Metal – 4 HP Nitrogen Stretching

frequency

1 [Cu(OCN)2 (4-HP)2] 375 - 240

2 [Cu(SCN)2 (4-HP)2] - 488 238

Epr Sprectra

The EPR spectra of samples in DMSO at liquid nitrogen temperature could provide values

of g, gII and gav. It has been suggested that the value other than an isotropic g-values from

the powdered spectrum can be assigned. From the spectrum considerable interaction between

the copper(II)centres can be interpreted and also that it is anti ferromagnetic[14]. The g, gII

tetragonally distorted octahedral. The deviation from the free – spin value may be due to

covalent bonding. Same result occurs for thiocyanate complex also. Table 6.

Fig. 4 EPR Spectrum of [Cu(OCN)2 (4-HP)2]

Table 6 EPR Spectral Data of Complexes At LNT

S. No. Complex A11 x 10-4 cm-1 gII g gav 2

1 [Cu(OCN)2 (4-HP)2] 185.88 2.1493 2.6620 2.1880 0.8164

2 [Cu(SCN)2 (4-HP)2] 186.92 2.1534 2.6810 2.2131 0.9985

THERMAL ANALYSIS

The thermogram of cyanate complex shows gradual release of CO2 with time and at 2360C to

2580C with a weight loss of 5% two molecules of 4-HP is released. This suggest the

structural make up of the complex. Similar observations are seen in the themogram of

thiocyanate complex[15].

Table 7 Thermal Analysis Value For Complexes. S.

No. Complex

Type of Degradation

Temperature %

Degradation

Possible Species Evolved

Start 0C End0C

1 [Cu(OCN)2 (4-HP)2] Endothermic 236 258 5% Two moles of 4-HP

2 [Cu(SCN)2 (4-HP)2] Endothermic

167

369

203

384

12%

9%

Two moles of SCN Two moles of 4-HP

Antimictrobial Activities

The results show antimicrobial activity depends on central metal ion and coordination

number when compared to the ligand. Two bacteria staphylococcus aures and Bacillus subtilis were taken with one fungus Aspergillus flavus [16]. The thiocyanate complex shows moderate activity against these two bacterial growth. The cyanate complex is not active

against these two bacteria. The cyanate complex is less active against the fungus when

compared to the thiocyanate complex [17]. Table 8.

Fig. 6 Zone Of Inhibition of [Cu(OCN)2 (4-HP)2]

Table -8 Antimicrobial Activities Of Complexes (Mm) S.

No. Complex

Zone of inhibition in mm Staphylococous

Aureus

Bacillus Subtilis

Aspergillus flavus

1 [Cu(OCN)2 (4-HP)2] - - 10

2 [Cu(SCN)2 (4-HP)2] 10 8 -

3 Ampicillin - 15 -

4 Fluconozole - - 20

Antioxidant Properties

For [Cu(OCN)2(4-HP)2] the IC50 value is above 1000 g/ml which shows the low

antioxidant property. For [Cu(SCN)2(4-HP)2] the IC50 value is above thousand at 1260.13

µg/ml which also show low antioxidant property. Similar result, above 1000 μg/ml results

for 4-HP, these values were compared with the standard vitamin C which have 136 μg/ml [18].

Fig. 7 DPPH Free Radical Scavenging Activity of [Cu(OCN)2(4-HP)2]

Table 9 IC50 Values For Complexes (Μg/Ml)

Sr.No. Complex IC50 Values in µg/ml

1 Vitamin C 136

2 [Cu(OCN)2(4-HP)2] Above 1000

3 [Cu(SCN)2(4-HP)2] 1260.13

4 4-HP Above 1000

CONCLUSION

Both the copper complexes with 4- hydroxypyridine were synthesized by similar method.

From the physical, spectral, electrochemical, thermal, and biological activities these two

complexes have the molecular formulae [Cu(OCN)2(4-HP)2] and [Cu(SCN)2(4-HP)2] These

complexes have tetragonally distorted octahedral geometry. Low antimicrobial activities

were observed for 4-HP and the complexes. Also the complexes have very low antioxidantal

property were recorded.

ACKNOWLEDGEMENT

The authors thank the Principal and Management of Bishop Heber College (Autonomous),

Tiruchirappalli. For providing laboratory facilities for the research work. The also thanks

SJC(ACIC)- Trichy, SAIF – Chennai, SAIF – Mumbai, STIC – Cochin and Gowri Bio tech

– Thanjavur for providing the required data.

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