Synthesis , Spectral and Magnetic Studies of Newly Mixed-Ligand Complexes of 4-Formyl-Acetanilide Thiosemicarbazone and 3 , 4-Dihydrocinnamic Acid with Some Metal Ions

New complexes with thiosemicarbazone derivative and 3, 4dihydrocinnamic acid were prepared and characterized by elemental analysis, determination of metal, IR, H NMR, electronic spectroscopy and magnetic measurements. The thiosemicarbazone derivative forms bidentate ligand complexes of the general formula, [M(Thz)(Caf)] where Thz = 4-formylacetanilide thiosemicarbazone, Caf = 3,4-dihydrocinnamic acid and M=Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb. The IR and H 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 Mn, Fe, Co, Ni, Zn, Cd and irregular tetrahedral geometry around Pb ion while the Cu complex has squar planer geometry.


Introduction
Thiosemicarbazone is an important class of compound containing both hard (N) and soft (S) donors ligands 1,2 .The ligand and most of their complexes were found to remarkably exhibit activity against some plant pathogenic fungi 3 .Moreover, it shows marked and selective antitumor, antiviral, antimalarial activities 4,5 .Thus, thiosemicarbazone derivatives and their metal complexes have shown significant anticancer activity 2,6 .Furthermore, there are many examples of biological importance of thiosemicarbazone derivatives such as thiacetazone which is used in the clinical treatment of tuberculosis 7 .This ligand has also potential biological activity and has been shown to display radiation protective and bacteriostatic activities 8 .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 isoniazid 9 .As part of ongoing study of thiosemicarbazone derivatives, it is reported herein the synthesis and characterization of some mixed ligand of Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ 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 (MnCl 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. 1 H NMR spectra were recorded using the JEOL JNM-ECP 400 Spectrometer in DMSO-d 6 , relative to the internal standard tetramethylsilane (TMS).Conductivity measurements were carried out at 25 o C 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 o C.

Results and Discussion
The reaction of metal salts with the Thz and caf gave complexes of the general formula [M(Thz)(Caf)] where M = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ , Thz = 4formyl-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 Cu 2+ complex because the molar conductivity is high 1,10 .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 agents 10,11 .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 atoms [12][13][14][15] .All the characteristic vibrations and assignments of the free ligands and their complexes are listed in Table 2.

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 Mn 2+ d 5 complex indicates that it has tetrahedral geometry.The 6 A 1 → 4 E (D) and 6 A 1 → 4 T 2(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 value 16,17 .The spectrum of the dark green of Fe 2+ complex exhibited absorption band in the visible region at 528 nm due to the electronic transition of 5 E (D) → 5 T 2(D) .The value of µ eff Fe 2+ d 6 complex was 4.320 BM which was in agreement with the expected spin value.All these values confirm that the Fe 2+ complex has tetrahedral geometry 16,18 .The [Co(Thz)(Caf)] complex adopts a distorted tetrahedral structure with the three bands which were assigned to 4 A 2(F) → 4 T 1(P) , 4 A 2(F) → 4 T 1(F) and 4 A 2(F) → 4 T 2(F) as it was observed at 350,462 and 888 nm respectively.Furthermore, the magnetic moment for the complex Co 2+ d 7 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 3 T 1(F) → 3 A 2(F) , 3 T 1(F) → 3 T 1(P) and 3 T 1(F) → 3 T 2(F) respectively.Thus, the higher value of the magnetic moment for Ni 2+ d 8 complex was 3.4 BM which was probably due to the orbital contribution.All these values support the tetrahedral geometry for the Ni(II) complex 21,22 .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 1 A 1 g→ 1 B 1 g, 1 A 1 g→ 1 A 2 g and 1 A 1 g→Eg respectively.Nevertheless, these bands were hidden by a strong CT transition.Therefore, all these rules are accepted for Square planer geometry 20 .Finally, the diamagnetic of Zn 2+ , Cd 2+ and Pb 2+ 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 transition 16,23,24 .All the data and remarks are found in Table 3.

H NMR spectra studies
The 1 H 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 Zn 2+ , Cd 2+ and Pb 2+ complexes.This indicates both of the nitrogen of NH acetamide and NH hydrazine are not involved to coordinate with the metal ions.Moreover, the NH 2 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 CH 3 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 form 25,26 .All the 1 H NMR chemical shifts (δ, ppm) of free ligand Thz and their complexes are listed in Table 4.The spectrum of the ligand Caf in DMSO-d 6 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 Zn 2+ , Cd 2+ and Pb 2+ 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 ethylene 27 .
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 Zn 2+ , Cd 2+ and Pb 2+ through the two O atoms 28 .The 1 H NMR chemical shift values of free ligand Caf and their complexes are reported in Table 5.

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 Cu 2+ 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 Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Zn 2+ and Cd 2+ complexes have tetrahedral geometry as can be seen in Figure 1.The Cu 2+ complex has square planer geometry.The Pb 2+ complex has irregular tetrahedral can be seen in Figure 2.

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

Table 2 .
The IR spectral bands (cm -1 ) of the free ligands and their complexes

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

Table 4 .
1H NMR signals of the free ligand and its complexes in DMSO-d 6

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