Synthesis and characterization of new thiourea complexes

Four Complexes of thiourea derivative (4-methoxy- N-(phenylcarbamothioyl) benzamide) have been prepared by the reaction of 4-methoxybenzoyl isothiocyanate with aniline,then the ligand obtained reacted with (Mn II ,Co II ,Cu II ,Ni II ) the resulting complexes were characterized by elemental analysis , FTIR , UV-Vis spectra and melting point. General formula that obtained is [L 2 MCl 2 ] for all complexes with octahedral geometry, where(L)=(4-methoxy-N(phenylcarbamothioyl)benza-mide) and M= (Mn II ,Co II ,Cu II ,Ni II ) .

Thiourea, CSN2H4 is basically occurs in two tautomeric forms and has three functional groups which are very important for the structural modifications to synthesize new derivatives.Thiourea and its derivatives display a broad spectrum of applications in industries, chemistry, medicine and others.In these present years, a lot of thiourea derivatives have been synthesized and their antimicrobial properties were widely explored [1][2][3][4][5].Industrial production and the use of Fe, Co, Cu, Ni, Zn, Cd, and Pb elements can cause environmental pollution.On the other hand, some of these metals are present in trace amounts as essential elements for biological systems and these metal ions also play an important role in bioinorganic chemistry.In order to understand the role of these metal ions in biological systems, structural studies of the biological compounds and their metal complexes are extremely important [17][18][19][20][21][22][23][24].and used as supplied.The FTIR spectra in the range (4000-200) cm-1were recorded as cesium iodide disc on FTIR 8300 Shimadzu Spectrophotometer.The UV-Visible spectra were measured by using Shimadzu UV-Vis.160 A spectrophotometer in the range (200 -1000) nm.Elemental microanalysis was carried out using CHNOS elemental analyzer model 5500 Carlo-Erba instruments.Gallen Kamp M.F.B.600.010F melting point apparatus were used to measure the melting point of all the prepared compounds.

2-Synthesis of ligand
Solution of 4-methoxy benzoyl chloride (0.005 mole) in absolute ethanol (25 mL) was added dropwise to potassium thiocyanate (0.005 mole) in absolute ethanol (25 mL).The reaction mixture was heated (50 °C) under reflux for 1 h , and then cooled to room temperature then (0.005 mole) of aniline in 20ml absolute ethanol was added and the resulting mixture was stirred for 2 h.The solid product was washed with water and purified by washing with ethanol absolute [1,8].

3-Synthesis of complexes
A solution of the metallic chlorides (0.01mole) in ethanol (30 mL) was added dropwise to a solution of the ligand in a 1:2 ratio for all metal with a small excess of ligand in ethanol (30 mL) at room temperature and the resulting mixture was refluxed for 2 hr.The solid complexes were filtered and washed with ethanol [1,8].

1-Synthesis of ligand ( L)
The syntheses (Scheme 1) involve the reaction of a 4-methoxybenzoyl chloride with potassium thiocyanate in absolute thanol, followed by condensation of the resulting 4-methoxybenzoyl isothiocyanate with aniline The ligands were purified by washing with absolute ethanol .Infrared spectra of ligand [25] The infrared of the ligand show the appearance of 3140 cm -1 of N-H and disappearance of NH 2 double band of the primary amine and show disappear of C=N at 1600cm -1 of the isothiocyanate derivative and shifting of C=O band from 1650 cm -1 to 1610cm -1 because of formation of amide group (NH-C=O) .The ligand also showed shifting of C=S from 1320cm -1 to 1230cm -1 because of formation of thiourea derivative (NH-C=S) .and showed S-H band from the totumaresim of thiourea (NH-C=S N=C-SH) S-H shown at 2644cm-1 C=N show at 1553cm-1 .[25] Complexes spectra showed distinct deference comparing with the spectrum of the ligand.They showed shifting of C=S from 1230 cm-1 to 1124cm-1 because of the coordination bond formed between S and metal (S-M) and shifting of C=O from 1610 to 1580 cm -1 because of the formation of coordination bond between O and metal (O-M) .the presence of M-S & M-O where confirmed the IR by the presence these bands between( 546-522 ) cm -1 and (462-410) cm -1 respectively Table 2

Electronic spectra of ligand
the ligand exhibited absorption band in UV region at wave number (32245)cm -1 which maybe attributed to( π π * ) transition another band of low intensity appears at (27723) cm-1 maybe refer to (n π * ) [26 ].

Conclusions
it may be concluded that ligand coordinate through one of the sulfer atom and oxygen.In the present investigations, all the complexes are found to be mononuclear, based on the FT-IR spectral data.The coordination number six is attained by coordination with the two bidentate ligand molecules and to two chloride atoms.Based on the physicochemical and the spectral studies the tentative structures proposed for the complexes are shown in Figure 1.

Figure 1 .
Figure 1.Proposed structure for the complexes

of new thiourea complexes …………………
The complexes were synthesized by the reaction of the ligand with the metal ions in 1:2 molar ratios in ethanolic medium.The ligand behaves as bidentate coordinate through oxygen and sulpher donor atoms.The analytical data of these complexes are presented in Table1.All the complexes are stable and can be stored at room temperature.

Table 1 .
Physical data of complexes.

Table 3 .
and actual values) are in accordance with the formula ML 2 Cl 2 indicating that the This can be explained by the absence of any deprotonating agent during the synthesis.The complexes are generally soluble in common organic solvents.Chemical analysis data of the complexes.
The C, H, N and M contents (both theoretically calculated values of new thiourea complexes ………………….