Synthesis, Spectral and Magnetic Studies of Newly Mixed...

ISSN: 0973-4945; CODEN ECJHAO

E-Journal of Chemistry

http://www.e-journals.net 2010, 7(S1), S594-S600

Synthesis, Spectral and Magnetic

Studies of Newly Mixed-Ligand Complexes

of 4-Formyl-Acetanilide Thiosemicarbazone and

3,4-Dihydrocinnamic Acid with Some Metal Ions

SHAYMA A. SHAKER

Department of Engineering Sciences and Mathematics

College of Engineering, Universiti Tenaga Nasional

43009 Kajang, Selangor, Malaysia

[email protected]

Received 30 March 2010; Accepted 25 May 2010

Abstract: New complexes with thiosemicarbazone derivative and 3, 4-

dihydrocinnamic acid were prepared and characterized by elemental analysis,

determination of metal, IR, 1H NMR, electronic spectroscopy and magnetic

measurements. The thiosemicarbazone derivative forms bidentate ligand

complexes of the general formula, [M(Thz)(Caf)] where Thz = 4-formyl-

acetanilide thiosemicarbazone, Caf = 3,4-dihydrocinnamic acid and M=Mn2+,

Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+. The IR and 1H NMR spectra

indicates that the (Thz) was coordinated with the metal ions through the N and S

atoms and the (Caf) was negatively charged bidentat ligand and was coordinated

with the metal ions through the two O atoms. Electronic spectra and magnetic

susceptibility measurements of the solid complexes indicates the tetrahedral

geometry around the Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+ and irregular tetrahedral

geometry around Pb2+ ion while the Cu2+ complex has squar planer geometry.

Keywords: 4-Formyl-acetanilide thiosemicarbazone complexes, Mixed-ligand complexes,

3,4-Dihydrocinnamic acid complexes, Caffeic acid complexes.

Introduction

Thiosemicarbazone is an important class of compound containing both hard (N) and soft (S)

donors ligands1,2

. The ligand and most of their complexes were found to remarkably exhibit

activity against some plant pathogenic fungi3. Moreover, it shows marked and selective

antitumor, antiviral, antimalarial activities4,5

. Thus, thiosemicarbazone derivatives and their

metal complexes have shown significant anticancer activity2,6

.

Synthesis, Spectral and Magnetic Studies S595

Furthermore, there are many examples of biological importance of thiosemicarbazone

derivatives such as thiacetazone which is used in the clinical treatment of tuberculosis7.

This ligand has also potential biological activity and has been shown to display

radiation protective and bacteriostatic activities8. Thiacetazone was shown

magnificently antimicrobial and used for treatment of tuberculosis. This ligand was used

as a drug against mycobacterium tuberculosis and found to be very useful in

combination with isoniazid9. As part of ongoing study of thiosemicarbazone derivatives,

it is reported herein the synthesis and characterization of some mixed ligand of Mn2+

,

Fe2+

, Co2+

, Ni2+

, Cu2+

, Zn2+

, Cd2+

and Pb2+

complexes with two different donor ligands

and shed some lights on the coordination properties of both of the 4-formyl- acetanilide

thiosemicarbazone and 3,4-dihydrocinnamic acid complexes with metal ions.

Experimental

All chemicals were obtained from commercial sources and were used without further

purifications (MnCl2.2H2O, FeCl2.4H2O, CoCl2.6H2O, NiCl2.6H2O, CuCl2.2H2O, ZnCl2,

CdCl2. H2O, Pb(NO3)2 and KOH) from Merck. 4-Formyl-acetanilide thiosemicarbazone and

3,4-dihydrocinnamic acid were obtained from Sigma. methanol, ethanol, DMSO and

DMSO-d6 were provided by BDH.

UV-Visible spectra were measured in dimethylsulfoxide (DMSO) using a Shimadzu

UV-2450 UV-Vis spectrophotometer. The IR spectra in the range of 4000-200 cm-1

were recorded as CsI disc on a Shimadzu FTIR-8300 Fourier Transform infrared

spectrophotometer. Determinations for metals were carried out using atomic absorption

spectrometer A-Analysis 800 Perkin Elmer. Elemental analysis (C, H, N, S) was

performed on a Perkin Elmer B-240 Elemental Analyzer. 1H NMR spectra were

recorded using the JEOL JNM-ECP 400 Spectrometer in DMSO-d6, relative to the

internal standard tetramethylsilane (TMS). Conductivity measurements were carried out

at 25 oC in DMSO using a Philips Pw-9526 digital conductivity meter. Melting points

were determined using a Digital Melting Point Apparatus. The magnetic susceptibility

measurements were eventually obtained using a Magnetic Susceptibility Balance, Model

MsB-MK1.

Synthesis of metal complexes

All the complexes were prepared by the same general method, an ethanolic solution 13 mL

of 4-formyl-acetanilide thiosemicarbazone (Thz) (0.178-0.433 g) and an KOH ethanolic

solution 15 mL of 3,4-dihydrocinnamic acid (Caf) (0.135-0.330 g) were added subsequently

to an aqueous solution of metal salts. The mixture was heated on water bath for 15 minutes

with constant stirring and then the formed products were filtered off, washed and

recrystallized with mixture of (1:3) water: ethanol and dried at 60 oC.

Results and Discussion

The reaction of metal salts with the Thz and caf gave complexes of the general formula

[M(Thz)(Caf)] where M = Mn2+

, Fe2+

, Co2+

, Ni2+

, Cu2+

, Zn2+

, Cd2+

and Pb2+

, Thz = 4-

formyl-acetanilide thiosemicarbazone and Caf=3,4-dihydrocinnamic acid. Table 1

shows the colors, elemental analysis and molar conductivity for these complexes. The

complexes have melting point above 215 o

C and these complexes are generally soluble

in DMSO. The molar conductance values are very low, therefore all the complexes are

considered to be non-electrolyte except the Cu2+

complex because the molar

conductivity is high1,10

.

S596 SHAYMA A. SHAKER

Table 1. Elemental analysis and some physical properties of the prepared complexes

Elemental analysis calc, (found )% Compound Color

M.P. oC C H N S M

Molar

conductivity

Ohm-1

cm2mol

-1

[Mn(Thz)(Caf)] Brown

yellow

254-

256 48.616

(48.02)

3.861

(3.251)

11.936

(10.303)

6.831

(5.421)

11.70

(11)

3.4

[Fe(Thz)(Caf)] Dark

green >300

48.522

(47.115)

3.854

(3.953)

11.913

(11.522)

6.818

(6.345)

11.87

(10.9)

3.6

[Co(Thz)(Caf)] Green-

yellow

253-

255

48.206

(47.96)

3.829

(3.521)

11.835

(10.303)

6.773

(6.391)

12.44

(11.51)

3.2

[Ni(Thz)(Caf)] Dark

green

244-

245

48.230

(48.641)

3.831

(3.20)

11.841

(10.641)

6.777

(5.401)

12.40

(12.19)

4

[Cu(Thz)(Caf)]Cl Dark

green

215-

217

47.741

(47.60)

3.792

(2.11)

11.721

(11.261)

6.708

(5.101)

13.29

(12.89)

23.2

[Zn(Thz)(Caf)] White 250-

252

47.558

(46.122)

3.777

(2.641)

11.676

(10.532)

6.682

(6.456)

13.62

(13.40)

3

[Cd(Thz)(Caf)] White 250-

251

43.313

(42.20)

3.440

(3.313)

10.633

(9.512)

6.086

(5.90)

21.33

(20)

7.4

[Pb(Thz)(Caf)] White 288-

290

36.708

(35.60)

2.915

(2.10)

9.012

(8.103)

5.158

(4.123)

33.33

(32.91)

5.25

The infrared spectra studies

The infrared spectrum of Thz shows strong band at 3160 cm-1

which is attributed to ν(NH).

The possibility of thion-thiol tautomerism (H-N-C=S) (C=N-SH) in this ligand has been

ruled out because there are no bands around 2500-2700 cm-1

. Moreover, the ligand has very

strong bands in 1668 cm-1

and 1606 cm-1

which are due to the ν(C=O) and ν(C=C)

respectively. Furthermore, the ν(C=N) band of thiosemicarbazone was observed at 1583 cm-1

and this band was shifted to lower frequencies by 63-16 cm-1

in the spectra of the complexes,

this is indicating the coordination of the imine N1. Thus, the spectrum of the ligand shows

ν(CS) in 830 cm-1

, so this band was shifted to the lower frequencies by 30-5 cm-1

on

coordination of the complexes. Moreover, the spectrum of the complexes showed weak

bands in the region of 418-459 cm-1

and 384-434 cm-1

which are attributed to ν(M-N) and

ν(M-S) respectively and this is supporting the coordination of the ligand as bidentate NS

cleating agents10,11

.

The spectrum of the free ligand Caf shows strong band at 1620 cm-1

which is assigned to

ν(COOH), this band appeared in complexes without any shifted. This indicates that the

carboxylate group remains without coordination with the metal ions. Furthermore, the

spectrum also shows very strong band at 3435 cm-1

which is due to ν(OH), this band

disappeared in complexes. Thus, the band at 1218 cm-1

which is attributed to the ν(C-O) was

shifted to the lower frequencies by 98-42 cm-1

in complexation. Moreover, the complexes

exhibited weak bands between 524-585 cm-1

which are due to ν(M-O). This indicates that

the 3,4-dihydrocinnamic acid which is coordinated with the metal ions through the two of

the O atoms12-15

. All the characteristic vibrations and assignments of the free ligands and

their complexes are listed in Table 2.


Table 2. The IR spectral bands (cm-1

) of the free ligands and their complexes

Compound ν(OH) ν(NH

)

ν(C=O

) ν(C=N) ν(C-O) ν(CS) ν(M-O) ν(M-N) ν (M-S)

Thz - 3160 1668 1583 - 830 - - -

Caf 3435 - - - 1218 - - - -

[Mn(Thz)(Caf)] - 3160 1667 1580 1173 810 583, 523 453,434 396

[Fe(Thz)(Caf)] - 3165 1665 1520 1120 817 525 450 400

[Co(Thz)(Caf)] - 3161 1666 1523 1174 810 583,524 453,418 396

[Ni(Thz)(Caf)] - 3162 1665 1523 1175 810 583,524 434,452 394

[Cu(Thz)(Caf)]Cl - 3165 1665 1529 1176 800 582 525 418

[Zn(Thz)(Caf)] - 3160 1668 1542 1173 810 583,524 453 434

[Cd(Thz)(Caf)] - 3157 1671 1567 1175 825 585,520 459 395,384

[Pb(Thz)(Caf)] - 3161 1668 1520 1174 810 583,524 453 434

Electronic spectral studies and magnetic measurements

The UV-Vis spectra of the Thz and Caf have shown that the absorption bands occured at

273,277 nm and 315,300 nm which are attributed to π→π* and n→π* respectively. The

spectrum of Mn2+

d5 complex indicates that it has tetrahedral geometry. The

6A1→

4E(D)

and 6A1→

4T2(D) can be seen at 314 and 330 nm respectively. Moreover, the magnetic

moment of the complex was 4.810 BM which was within the expected spin-only

value16,17

. The spectrum of the dark green of Fe2+

complex exhibited absorption band in

the visible region at 528 nm due to the electronic transition of 5E(D) →

5T2(D). The value

of µeff Fe2+

d6 complex was 4.320 BM which was in agreement with the expected spin

value. All these values confirm that the Fe2+

complex has tetrahedral geometry16,18

. The

[Co(Thz)(Caf)] complex adopts a distorted tetrahedral structure with the three bands

which were assigned to 4A2(F) →

4T1(P),

4A2(F) →

4T1(F) and

4A2(F) →

4T2(F) as it was

observed at 350,462 and 888 nm respectively. Furthermore, the magnetic moment for

the complex Co2+

d7 was found to be 3.401 BM

16,19,20. The spectrum of the dark green of

the Ni(II) complex exhibited absorption bands at 286,508 and 853 nm which were

attributed to the 3T1(F) →

3A2(F),

3T1(F) →

3T1(P) and

3T1(F) →

3T2(F) respectively. Thus, the

higher value of the magnetic moment for Ni2+

d8 complex was 3.4 BM which was

probably due to the orbital contribution. All these values support the tetrahedral

geometry for the Ni(II) complex21,22

. The [Cu(Thz)(Caf)]Cl complex exhibited

absorption band at 288 nm which is expected to be the LMCT S→d and the other bands

at 337, 368 and 386 nm which are assigned to 1A1g→

1B1g,

1A1g→

1A2g and

1A1g→Eg

respectively. Nevertheless, these bands were hidden by a strong CT transition.

Therefore, all these rules are accepted for Square planer geometry20

. Finally, the

diamagnetic of Zn2+

, Cd2+

and Pb2+

complexes have absorption bands at 335,336 and

345 nm respectively which are due to the charge transfer M→L. This is because of the

electronic configuration of these complexes which confirmed the absence of any d-d

electronic transition16,23,24

. All the data and remarks are found in Table 3.

1H NMR spectra studies

The 1H NMR spectrum of the Thz shows signal protons at 10 and 11.28 ppm which are

attributed to the NH acetamide and NH hydrazine respectively. The chemical shifts due to

those signal protons remained unchanged in the spectra of Zn2+

, Cd2+

and Pb2+

complexes.

This indicates both of the nitrogen of NH acetamide and NH hydrazine are not involved to


coordinate with the metal ions. Moreover, the NH2 group due to carbothioamide exhibited

signal proton was splitted to the 7.93 and 7.90 ppm. This signal was appeared at 7.96 and 7.97

ppm on the complexes. Furthermore, the ligand Thz showed signal protons at 8.09 and 2.01

ppm which are attributed to CH of methylene group and CH3 of acetamide group. Thus, the

chemical shifts of the CH aromatic were observed at 7.70, 7.66, 7.60 and 7.52 ppm. The absence of

the signal proton of SH group at 12.10 ppm is further supported the presence of the thione

form of the Thz in the complexes instead of thiole form25,26

. All the 1H NMR chemical shifts

(δ, ppm) of free ligand Thz and their complexes are listed in Table 4.

Table 3. The UV-Vis spectra and magnetic moment values of the free ligand and their

complexes

Compound λmax

nm

Wave

number cm-1

εmax

Lmol-1

cm-1

Assignment

µeff Calc.(found)

BM

Thz 273 36630 746 π→π*

315 31746 4027 n→π*

-

Caf 277 36101 685 π→π*

300 33333 1904 n→π*

-

[Mn(Thz)(Caf)] 294 34013 3960 Charge transfer (C.T)

314 31847 4027 6A1→

4E(D)

330 30303 4327 6A1→

4T2(D)

5.916

(4.810)

[Fe(Thz)(Caf)] 355 28169 4327 C.T

528 18939 129 5E(D) →

5T2(D)

4.898

(4.320)

[Co(Thz)(Caf)] 350 28571 3960 4A2(F) →

4T1(P)

462 21645 44 4A2(F) →

4T1(F)

3.872

(3.401)

888 11261 13 4A2(F) →

4T2(F)

[Ni(Thz)(Caf)] 286 34965 4106 3T1(F) →

3A2(F)

508 19685 13 3T1(F) →

3T1(P)

2.828

(3.4)

853 11723 24 3T1(F) →

3T2(F)

[Cu(Thz)(Caf)]Cl 288 34722 3960 LMCT S→d diamagnetic

337 29673 1236 1A1g→

1B1g

368 27173 3630 1A1g→

1A2g

386 25906 3852 1A1g→

1Eg

[Zn(Thz)(Caf)] 335 29850 1269 CT M→L diamagnetic

[Cd(Thz)(Caf)] 336 29761 1158 CT M→L diamagnetic

[Pb(Thz)(Caf)] 345 28985 1210 CT M→L diamagnetic

Table 4. 1H NMR signals of the free ligand and its complexes in DMSO-d6

Compound NHace NHhyd NH2 car CHme CHaro CH3 ace

Thz 10.00 11.28 7.93, 7.90 8.09 7.70,7.66,7.60,7.52 2.01

[Zn(Thz)(Caf)] 10.15 11.31 7.96 8.06 7.71,7.69,7.60,7.58 2.04

[Cd(Thz)(Caf)] 10.12 11.30 7.97 8.04 7.68,7.65,7.58,7.56 2.03

[Pb(Thz)(Caf)] 10.14 11.30 7.97 8.05 7.71,7.68,7.60,7.58 2.03

ace=acetamide, hyd=hydrazine, car=carbothioamide, me=methylene and aro=aromatic

The spectrum of the ligand Caf in DMSO-d6 shows five signal protons of hydrogen at: δ

6.93(H1), 6.87(H2), 6.60(H3), 7.12(H4) and 6.15(H5). When Caf was complexed with Zn2+

, Cd2+

and Pb2+

all these signal protons were desheilded downfield for aromatic protons H2, H3 and H4,

which are highly hydrophobic and corresponding to the benzene ring and portion of ethylene27

.


Furthermore, the spectrum of Caf exhibited two signal protons at 8.40 and 8.19 ppm which are

attributed to two groups of OH. These signal protons were disappeared in complexes which may

indicate that the Caf was coordinated with the Zn2+

, Cd2+

and Pb2+

through the two O atoms28

. The 1H NMR chemical shift values of free ligand Caf and their complexes are reported in Table 5.

Table 5. 1H NMR chemical shifts (δ, ppm) of the free ligand and its complexes

Compound H1 H2 H3 H4 H5

Caf 6.93 6.87 6.60 7.12 6.15

[Zn(Thz)(Caf)] 6.97 6.88 6.73 7.15 6.22

[Cd(Thz)(Caf)] 6.95 6.86 6.71 7.15 6.18

[Pb(Thz)(Caf)] 6.97 6.88 6.73 7.14 6.22

Conclusion

A newly synthesized mixed ligand complexes of 4-formyl-acetanilide thiosemicarbazone and

3,4-dihydrocinnamic acid with some metal ions is presented in this article. All the complexes

were non-electrolyte in DMSO except the Cu2+

complex was electrolyte because of its high

molar conductivity. The Thz and Caf behave as a bidentate ligand with the metal ions. The IR

spectra suggested that the Thz was coordinated with the metal ions through the N and S atoms

and the Caf ligand was coordinated with the metal ions through the two O atoms. The electronic

spectra and magnetic moments have suggested that the Mn2+

, Fe2+

, Co2+

, Ni2+

, Zn2+

and Cd2+

complexes have tetrahedral geometry as can be seen in Figure 1. The Cu2+

complex has square

planer geometry. The Pb2+

complex has irregular tetrahedral can be seen in Figure 2.

CH3 N

H

C

N

H

N

C

H

NH2

SO

M

O

O

O

HO

M=Mn+2, Fe+2, Co+2, Ni+2, Zn+2 and Cd+2

3

4

12

4

5

1

32

Figure 1. Suggested structure of [M(Thz)(Caf)] complexes

CH3 N

H

C

N

H

N

C

H

NH2

SO

O

O

O

OH

Pb

1

4

5

23

2

4

3

1

Figure 2. Suggested structure of [Pb(Thz)(Caf)] complex

M = Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+


Acknowledgment

The author would sincerely like to thank the Chemistry Department of College of Science, Al-Mousel University, Iraq for their technical assistance. Additional thanks are also due to Dr. Hussein A. Mohammed for his kind assistance.

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