S YNTHESIS , C HARACTERIZATION AND B ACTERIAL ACTIVITY OF SOME METAL COMPLEXES OF N-PHENYL-Ń-( 3-CARBOXYPHENOL ) THIOUREA

A thiourea ligand; N-phenylŃ-(3carboxyphenol) thiourea (PCTH) is synthesized from the reaction of phenyl isothiocyanate with 3-aminobenzoic acid. Treatment of the ligand (PCTH) with metal salts MCl2, where M = Cu(II), Zn(II), Pb(II) and Co(II) gave metallic complexes of the types: 1[M(PCTH)2Cl2] where M=Cu(II) and Co(II) and 2[M(PCT)2] where M=Zn(II) and Pb(II). The ligand (PCTH) behaves as a bidentate and coordinated to the metal ion centers either through sulfur atom of its thioamide group and through nitrogen atom of the amine group or through oxygen atom of the carboxylic group. All the synthesized ligand metal complexes are characterized by micro-elemental analysis, IR spectroscopy and UV-Vis. spectroscopy, 1 H.NMR, 13 C.NMR, conductivity and magnetic susceptibility measurements. Finally, bacterial activity of the ligand (PTCH) and its metal complexes are tested against Klebsiella pneumonia and Escherichia coli and gram-positive bacteria Staphylococcus aurous. Using well-diffusion method and the results are discussed.


INTRODUCTION
Thiourea and its derivatives are important ligands for transition metals [1], which able to coordinate to a range of metal centers as ligands either from oxygen, nitrogen and sulfur donor atoms of thiourea derivatives [2]. Thiourea ligands and their metal complexes exhibit a wide range of biological activity including anticancer, fungicides, antimicrobial and show a broad spectrum of biological activities as anti-HIV [3].
In this study, we report herein the synthesis, characterization and antibacterial studies of

Syntheses of the ligand
Phenylisothiocyanate (2.70 gr 0.02 mmol) was added to a solution of 3-amino benzoic acid (2.74 gr 0.02 mmol) in ethanol (25 cm 3 ). The solution mixture was refluxed for 10 hours to give a white precipitate. Then the solution left to cool in ice-bath to give a white precipitate, which was filtered washed with ethanol and diethyl ether, dried and recrystallized from hot ethanol [4].

General procedure for preparation of metal complexes
The warm ethanolic solution of the ligand and metal salts solution were mix in the stoichiometric proportions ( 1 : 2 ), ( metal: ligand ) ratio for all divalent metal ions the resultant mixture was stirred and refluxed for (2 -6 ) hours. The precipitate was formed, and then the solution mixture was cooled in ice -bath for complete precipitation. The product was filtered off, washed with ethanol and diethyl ether, and dried under vacuum.

Bacterial activity:
The bacterial activity of the ligand (PCTH) and its metal complexes was measured using well-diffusion method [5] .

Physical measurements:
Melting points were measured using Stuart Digital Melting point apparatus. Electronic spectra of the ligand and the complexes were carried out for (1 * 10 -3 M) solution in DMSO using a T60 UV/Vis spectrophotometer. The Infrared spectra of the ligands and complexes were recorded on a (Shimadzu) infrared spectrophotometer in the (250-4000) cm -1 range using CsI disk. Elemental analysis was carried out on Perkin Elmer-2400 CHNS analyzer.
The conductivities of the complexes were carried out for (1 * 10 -3 M) solution in DMSO using Conductometer type (Cond. 720) conductivity meter. Magnetic measurements were recorded on an auto Magnetic Susceptibility balance Guoy method.

Elemental analysis
Elemental analysis data for the synthesized ligand and its metal complexes are shown in Table (1). They are consistent with the suggested stoichiometries. The color and melting points of the synthesized ligand and its metal complexes are also shown in Table (1).

Molar conductivities
Molar conductivities of all synthesized complexes are listed in Table (1). These measured values are compared with known molar conductivities [6], which indicates that they are non-electrolyte and consistent with the proposed formula for them.

Electronic spectra
The UV spectral diagrams of the free ligand ( PCTH ) show band at about 37313 cm -1 is assigned to (n  * ) absorption for ligand [11]. The electronic spectrum of Cu(II) complex shows tow bands at 43478 and 22727 cm -1 , Table (2), which are denoted to Cu-ligand charge transfer transition [12], and ( 2 B 1 g → 2 B 2 g) transition [13] respectively, suggesting a octahedral structure for the Cu(II) complexes.

Magnetic susceptibility
The magnetic susceptibility of Cu(II) complex is 2.01 B.M. Table (2), which confirms a octahedral geometry around Cu(II) . The magnetic susceptibility of Zn(II) and Pb(II) complex are zero which denote to that they are diamagnetic and have tetrahedral arrangements around metal centers [16]. While the magnetic susceptibility of Co(II) complex, is (4.95) B.M. this values of magnetic moment is higher than the spin-only value (3.87 B.M) for their unpaired electrons and may be ascribe to substantial orbital contribution to the moment which is applicable of which suggests an octahedral geometry around the metal [17].

Table (2) :
The electronic data for thiourea derivative(PCTH) and its metal complexes.

Infra-Red Spectroscopy
The ligand N-phenyl-Ñ-(3-carboxyphenol) thiourea (PCTH) was synthesized by reaction of equimolar amounts of Phenylisothiocyanate and 3-amino benzoic acid in ethanol. It is a white solid, soluble in methanol, ethanol, acetone and dichloromethane, but it is insoluble in water. respectively [18], [19].  [20]. υ(N-H) in the complexes, it is found in the 3225-3174 cm -1 region suggesting the bonding through nitrogen atom in complex (2). υ(C=O) observed at 1724 -1615 cm -1 in indicating that the (C=O)group coordinate with metals in complex (1 and 4) . υ(C=S) observed at 1350 -1255cm -1 in indicating that the (C=S)group coordinate with all metal complexes [21]. New bond formed between metal and N, O, Sand Cl [22] listed in Table (3) .

Table (3):
Selected IR bands of the Thiourea and its metal complexes (cm -1 ).

Bacterial activity of the ligand (PCTH) and its metal complexes
In vitro antibacterial screening was performed by the agar disc diffusion method. The bacterial species used in the screening were gram-negative bacteria Klebsiella pneumonia and Escherichia coli and gram-positive bacteria Staphylococcus aurous.
The measured biological activities of the ligand (PCTH) and its metal complexes are arranged in Table (

CONCLUSIONS
A novel ligand (PCTH) and its Cu(II), Zn(II), Pb(II) and Co(II) complexes were synthesized and fully characterized by various spectroscopic techniques and the bacterial activity was tested against different bacteria and the result show different activity of the free ligand and metal complexes.
According to elemental analysis, IR and uv-visible spectroscopy, conductivity and magnetic susceptibility data the following structures are proposed for the synthesized metal complexes as shown in Fig. (3).