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Preparation and Characterization of Some Transition Metal Complexes with New Schiff Base Ligand Derived from

Benzophenone.

Abid Allah Mohamad Ali, Methak Saeed Mohamad, Muna Abass Hadi Chemistry Department/ College of Education for Women / University of Kufa

الخلاصة

ت ات الكوبل ة لایون دات الكلابی ض المعق ، (II)، النحاس(II)، النیكل(II)تضمن البحث تحضیر وتشخیص بعدة (II)والزئبق (II)، الكادمیوم(II)الخارصین داي - 4،4̀داي ھایدروكسي –2،٢̀ مع لیكاند قاعدة شف الجدی

دات وقد تم الحص. BPHTSCمیثوكسي بنزو فنیدین ثایوسیماكاربازون ول على التراكیب البینیة لھذه المعقت عة تح اف الاش ة واطی یلیة المولاری یة والتوص زوم المغناطیس ر والع دقیق للعناص ل ال ات التحلی ن قیاس م

وع . الحمراء والفوق البنفسجیة ن ن دات ھي م رح . ML2كما بینت الدراسة ان الصیغ التركیبیة للمعق د اقت وقع الم طوح لجمی اني الس كل ثم یة الش جیة والحساس وق البنفس عة الف ف الاش ائج طی ن نت لبة م دات الص عق

د ع BPHTSCالمغناطیسیة كما تبین أن اللیكان رتبط م ب ت ة المخل البة ثلاثی ة الشحنة الس د احادی تسلك كلیكان . الایونات الفلزیة من خلال ذرات النایتروجین والاوكسجین والكبریت

Abstract The preparation and characterization of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) chelate complexes of new Schiff base 2,2̀-dihydroxy-4,4̀-dimethoxy benzopheneden thiosemicarbazone BPHTSC are reported. Structural features were obtained from their elemental analysis, magnetic moment, molar conductance and spectral Uv.Vis and IR measurements. The data show that these complexes have composition of [ML2] type. The Uv-Vis and magnetic susceptibility data of the complexes suggest octahedral geometry of all complexes and the ligand BPHTSC behaves as mono basic tridentate ligand, by coordination through the nitrogen and sulfur/oxygen atoms. Key Words: Schiff Base, Metal Chelate Complexes, Characterization

Introduction Avery large number of metal complexes involving benzophenone derivatives as ligand have been prepared and studied. The complexes of VO(IV), Ni(II) and Cu(II) ions with a Schiff base derived from 2-hydroxy-4-methoxy benzophenone and benzoyl acetone have been prepared and investigated using different chemical techniques, such as; elemental analysis, conductance, magnetic, infrared and electronic spectral measurements(1). Biological activity of Schiff bases derived from benzophenone has been widely studied such as cytotoxic activities against human oral squarnous carcinoma cells HSC-2 and normal human gingival fibroblasts (HGF), antibiotic activities against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Emeterococcus faecium and protein kinase C inhibitor(2).

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Here we present the synthesis and characterization of a new Schiff base ligand derived from benzophenone and its chelate complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) metal ions. Experimental Materials and measurements All reagents and solvents were obtained from BDH, Aldrich and used with out further purification. The electro thermal malting point model 9300 was used to measure the melting points of the ligand and its complexes. The elemental analyses were carried out by means of micro analytical unit of 1108 C.H.N elemental analyzer Babylon university. The IR spectra of the compounds were recorded using KBr discs 4000-400 cm-1 on FT-IR Testscan shimadza model 8000. The Uv-Vis spectra were recorded in ethanol on shimadzu modal 1700 Uv-Vis spectrophotometer. Magnetic susceptibilities were measured as powder samples using Faraday method, Balance Magnetic MSB-MKI was employed for this purpose. The diamagnetic corrections were calculated using pascal,s constant(3). Electrical conductivity was measured by using alpha Digital conductivity meter with solute concentration of 10-3M in DMSO. Physical characterization of the ligand and its metal complexes are listed in table1. Preparation of the ligand BPHTSC The ligand BPHTSC was prepared by condensation of 2,2̀-dihydroxy-4,4̀-dimethoxy benzophenone and thiosemicarbazide in equimolar 1:1 ratio, in absolute alcohol. Few drops of glacial acetic acid were added to the reaction mixture and refluxed for 3 hrs. The product was recrystallized from ethanol, and dried over anhydrous CaCl2 . The reaction mixture gives single product according to the following reaction . Scheme 1.

O

OH

OH

MeO

MeO

NH2 NH NH2

SETOH,HOAC

reflux ( 3hr ) NNH NH2

SOH

OH

MeO

MeO

thiosemicarbazide2, 2-َdihydroxy - 4, 4-َdimethoxy benzophenone 2, 2-َdihydroxy - 4, 4-َdimethoxy benzophenone thiosemicarbazone

+

Scheme 1: preparation of the BPHTSC ligand

Preparation of complexes [ML2] complexes were prepared by addition of metal salts 0.001mol in 30ml ethanol to a hot ethanolic solution of the ligand 0.002mol in 30ml to metal chloride

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this solution in 1:2 molar ratio. The reaction mixture was heated under refluxed for 1hr. On cooling the complexes separated out, which were filtered and washed several times with alcohol and dried over anhydrous CaCl2. Results and Discussion In the systems ML2 where M = Cu, Co, Ni, Zn, Cd, Hg and L = 2,2̀- dihydroxy-4,4̀- dimethoxy benzophenden thiosemicarbazone, the preparation have been developed in the molar ratio 1:2. The metal chloride interacts with the ligand, being vary colored crystals from the reaction , these chelates are stable towards air and moisture, insoluble in water, but soluble in most common organic solvents. The conductivity values 4.61-7.34 S. cm2. mol-1 indicate that the complexes are non- electrolytes in solution. Infrared Spectra The important infrared spectral bands for the synthesized ligand and its chelate complexes are given in table2. The ligand contains three potential donor sites which are the hydroxylic oxygen, azomethine nitrogen and thione sulfur. The absorption band which appeared at 3442 cm-1 in the spectrum of ligand was attributed to υ(O-H)(4). In the spectra of complexes this band was not observed, suggesting deprotonation of the hydroxyl group and formation of M-O bands(5,6). The weak band in the spectrum of free ligand observed at 3320 cm-1 due to υ(NH2) remained unaffected after complexation(7). The spectrum of the free ligand exhibited abroad band at 3419 cm-1 assignable to the υ(N-H) group(8,9). No change was observed for this band in the spectra of complexes. The band observed at 1640 cm-1 assigned to υ(C=N) vibration of azomethine group was shifted to lower wave number in all metal complexes due to the coordination of the nitrogen atom of the azomethine group(10). On the other hand, the υ(C=S) band at 1176cm-1in the free ligand was moved to alower frequency by 10cm-1 after complexation, which means that the shifts are due to coordination of ligand to metal atom by the thione sulfur group(11,12). Some other new bands appeared in the region of 550-410 cm-1 in the complexes spectra, which are not present in the spectrum of the ligand may be attributed to the υ (M-N), υ (M-S) and υ (M-O) band(13,14).

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Figure 1: IR Spectra of; a : The ligand (BPHTSC) & b: [CuL2]

Electronic spectra and magnetic moments The magnetic moment values measured at room temperature and electronic spectra bands of the complexes which were studied are given in table 3. The magnetic moment of Co(II) complex 4.21B.M suggest ahigh-spin octahedral configuration(15). The high values of (µeff) may be due to orbital contribution. The electronic spectrum of this complex shows three absorption bands at 14800, 16556 and 23823 cm-1, there are assigned to 4T1g(F)→ 4T2g(F) (υ1) 4T1g(F)→ 4A2g(F) (υ2) and 4T1g(F)→ 4T1g(p) (υ3) transition respectively, which are characteristic of octahedral stereo geometry(16). The Ni(II) complex gave a magnetic moment value of 3.18 B.M, and d-d spectrum of this complex show bands at 15384 and 24150 cm-1, which are suggesting the existence of 3A2g→3T1g(F) (υ2) and 3A2g→ 3T1g (P) (υ3) transition, this suggests that the complex octahedral(15). The magnetic moment value of the copper(II) complex 1.78 B.M which may suggest an octahedral structure. Its electronic spectrum shows band centered at 16597 cm-1 which may assigned to 2Eg→ 2T2g transition in octahedral environment(17). The complexes of Zn(II), Cd(II) and Hg(II) were diamagnetic and did not show d-d transition. The electronic spectra of the Schiff base and the copper(II) complex are shown in Figure 2. Molar conductance Measurements All chelate complexes prepared in this work showed conductivity values ranged between (4.61-7.34) S.mol-1.cm2 in DMSO at room temperature these values indicate that no conductive species exist(18). According to these results the structural formula of the metal complexes may be proposed as in Figure 3.

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Figure 2: Electronic spectrum of ; a: [CuL2] & b: the ligand BPHTSC

Table 1: Physical data and analysis of ligand and its complexes No. Compound Color M.P

ºC Yield

% Formula Found,(calc.)%

C H N M 1 L=(BPHTSC) Yellow 131 72 [C16H17N3O4S] 54.95

(55.33) 4.54

(4.89) 12.20

(12.10) ----

2 [CoL2] Green 165 66.23 [C32H32N6O8S2Co] 25.21 (25.56)

2.30 (2.13)

5.33 (5.59)

7.55 (7.84)

3 [NiL2] Green 155 ٧٢.43 [C32H32N6O8S2Ni] 25.56 (25.5)

2.23 (2.13)

5.67 (5.59)

7.43 (7.83)

4 [CuL2] Green 180 75.12 [C32H32N6O8S2Cu] 24.99 (25.41)

2.37 (2.11)

5.34 (5.55)

8.12 (8.40)

5 [ZnL2] Yellow 167

78.65 [C32H32N6O8S2Zn] 25.66 (25.34)

2.07 (2.11)

5.22 (5.54)

7.87 (8.63)

6 [CdL2] Yellow 188 d

70.11 [C32H32N6O8S2Cd] 24.23 (23.86)

1.78 (1.98)

6.02 (5.22)

13.47 (13.97)

7 [HgL2] Yellow 202 d

68.88 [C32H32N6O8S2Hg] 21.64 (21.51)

1.58 (1.79)

4.88 (4.70)

21.85 (22.46)

L = Ligand, d= complex metal with decomposition

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Table 2 : IR spectra frequencies for the ligand and its metal complexes in cm-1

units

L= ligand, s = strong, w = weak, m = medium, br = broad

Table 3 : Electronic spectra, conductivity and magnetic moment of complexes Conclusion

The symmetric Schiff base ligand coordinates to the Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) ions in tridentate manner using the azomethine N, sulfur S and enol O atoms. The assignment of a 6-coordinate a octahedral stereochemistry are stable and nonionic to all the reportedcomplexes compounds Figure 3.

Compound υ (OH)

Υ(NH2) Υ(N-H) υ(C=N) υ(C=S) υ(NH-C=S)

υ (M-O)

Υ(M-N)

Υ(M-S=C)

L=(BPHTSC) 3442w 3320 w 3419 w 1640s 1176 s 870 w ---- ---- ----- [CoL2] 3400w 3322 w 3400wbr 1595m 1166 m 866 w 549w 474

w 457 w

[NiL2] 3345w 3320 m 3410w 1600s 1160 w 860 w 540w 466 w

447 w

[CuL2] 3336m 3320 w 3413w 1605m 1162 s 872 w 547w 470w 440w [ZnL2] 3403w 3322 w 3400w 1610m 1165 w 870 w 544w 477

w 443w

[CdL2] 3315w 3320w 3410wbr 1600m 1160 w 865 w 545w 465 w

445 w

[HgL2] 3350m 3319 w 3412w 1595s 1165 m 868 w 543w 466 w

442w

Complexes Absorption Bonds(cm-1)

Transition Conductivity S.mol-1. cm2

µeff(B.M)

[CoL2] 14800 16556 23823

4T1g(F)→4T2g(F) 4T1g(F)→4A2g(F) 4T1g(F) →4T1g(P)

5.42 4.21

[NiL2] 15384 24150

3A2g→3T1g(F) 3A2g→3T1g(P)

4.61 3.18

[CuL2] 16597 2Eg→2T2g 5.87 1.78 [ZnL2] ---- ---- 6.89 Dia [CdL2] ---- ---- 7.34 Dia [HgL2] ---- ---- 6.95 Dia

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S

NH

NH2

O

M

N

OHOMe

OMeS

NH

NH2

O

N

OHMeO

MeO

M= Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II)

Figure 3: The proposed structural formula of the metal chelate complexes

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