NEW AZO-SCHIFF BASE DERIVED WITH Ni(II), Co(II), Cu(II), Pd(II) AND Pt(II) COMPLEXES: PREPARATION, SPECTROSCOPIC INVESTIGATION, STRUCTURAL STUDIES AND BIOLOGICAL ACTIVITY

 

ABBAS ALI SALIH AL-HAMDANI^1,*, ABDEL MAJID BALKHI², AHMAD FALAH², SHAYMA A. SHAKER^3,*

¹Department of Chemistry, College of Science for Women, University of Baghdad, Iraq
²Department of Chemistry, Faculty of Science, University of Damascus, Syria
³Departament of enviromental engineering, komar University of Science and technology, Sulaymani, Kurdistan, Region, Iraq
e-mail: abbas_alhamadani@yahoo.co.uk

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ABSTRACT

The coordination ability of the azo-Schiff base 2-[1,5-Dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid has been proven in complexation reactions with Co(II), Ni(II), Cu(II), Pd(II) and Pt(II) ions. The free ligand (LH) and its complexes were characterized using elemental analysis, determination of metal concentration, magnetic susceptibility, molar conductivity, FTIR, Uv-Vis, (1H, 13C) NMR spectra, mass spectra and thermal analysis (TGA). The results confirmed the coordination of the ligand through the nitrogen of the azomethine, Azo group (Azo) and the carboxylate ion with the metal ions. The activation thermodynamic parameters, such as ΔE*, ΔH*, ΔS*, ΔG*and K are calculated from the TGA curves using Coats-Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in the gas phase. The synthesized ligands and their metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aereuguinosa).

Keywords: Azo- Schiff base ligand, Kinetics, Thermodynamic parameters, Antibacterial activity, Spectroscopic investigation

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1. INTRODUCTION

Schiff base derivatives attract significant interest and occupy an important role in the development of coordination chemistry. Moreover, Schiff base complexes containing transition metals have been studied in several research areas such as structural chemistry¹. Azo compounds with two phenyl rings separated by an azo bond are very important in fundamental research area and applications². In addition, azo-Schiff base derivatives are known to be important in several classes of medicinal and pharmaceutical fields. Furthermore, some of them show biological activities such as antibacterial, antifungal, anticancer and herbicidal activities^3-12. However, the light induced interconversion allows systems incorporating azo group to be used as reversible control over a variety of chemical, electronic and mechanical applications^{2, 13, 14}. Azo compounds metal complexes have also been attracting much attention because of their applications in dyes, pigment, functional materials and optical computing¹⁵. As part of our research in the study of coordinating capabilities of Azo-schiff base derivatives and their coordination compounds¹⁶, we report herein the synthesis and spectroscopic studies as well as the thermal investigation of a novel Azo-schiff base derivative Ligand (LH) (L= 2-[1,5-Dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid with some transition metals such as Ni^II, Co^II, Cu^II, Pd^II and Pt^II complexes. (¹H, ¹³C) NMR spectra were obtained to determine the structure of the ligand.

2. EXPERIMENTAL

2.1. Materials and measurements

All reagents were commercially available and used without further purification. Solvents were distilled from appropriate drying agents immediately prior to use.

Elemental analyses (C, H and N) were carried out on a Heraeus instrument (Vario EL). Melting points were obtained on a Buchi SMP-20 capillary melting point apparatus. IR spectra were recorded as KBr discs using a Shimadzu 8300 FTIR spectrophotometer in the range (4000-400) cm^-1. Electronic spectra were measured in the region (200-1100) nm using 10^-3 M solutions in DMF at 25°C with a Shimadzu 160 spectrophotometer. NMR spectra (¹H-, ¹³C-NMR) were recorded in DMSO-d₆ solution using Brucker AMX400 MHz spectrometer with tetramethylsilane (TMS) as an internal standard for ¹H NMR analysis. Metals were determined using a Shimadzu (A.A) 680 G atomic absorption spectrophotometer. Chloride was determined using a potentiometric titration method on a 686-Titro processor- 665Dosimat-Metrohm Swiss. Conductivity measurements were made with DMF solutions using a Jenway 4071 digital conductivity meter at room temperature. Electron impact mass spectra (70 eV) were recorded on a Finnegan-MAT model 8430 GC MS-DS spectrometer. Magnetic moments were obtained using a magnetic susceptibility balance (Johnson Mattey Catalytic System Division). Thermal analysis studies of the ligand and complexes were performed on a Perkin-Elmer Pyris Diamond DTA/ TG Thermal System under nitrogen atmosphere with a heating rate of 10°C/ min from 30-700°C.

2.2. Synthesis of the compound 1,5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethylimino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylamine (A)

An ethanolic solution (15 ml) of 5-methyltryptamine hydrochloride (1.036 g, 0.00492 mol) was added to a mixture containing an ethanolic solution (25 ml) of 4-amino-1,5-dimethyl-2-phanyl-3-pyrazol-5-one (1 g, 0.00492 mol). The reaction mixture was heated in a water bath at 40-50 °C for 14 h, in presence of K₂CO₃ after the addition of excess of ethanol (50 ml). The resulting mixture was refluxed under N₂. A white solid was formed, and then recrystallized from a water: ethanol (1:1) solvent mixture. The product was dried over anhydrous CaCl₂ under vacuum. Yield: 53.76 %(0.95 g); MP: 177 °C; ¹H NMR (DMSO-d₆, ppm): δ 1.89 (s, =CCH₃), 2.10 (s, arom-CH₃), 3.43 (s, NCH₃), 3.30 (t, NCH₂), 2.74 (t, CCH₂), 7.64-8.08 (m, arom), 12.11 (s, NH), 4.10(s, NH₂). ¹³C-NMR (100.622 MHz, DMSO-d₆): δ 16.39(C₂₀), 18.87(C₃), 38.79(C₁₃), 45.6(C₁₂), 58(C₁), 98(C₁₇), 100(C_7,11,14), 110(C₁₈), 111(C_15,21), 118(C₄) 123.77(C₉), 127(C₂₂), 129(C₁₉), 130(C_8,10), 140(C₆), 146(C₂), 151(C₅); MS, m/z 360, 164, 201.

2.3. Synthesis of the ligand (LH) 2-[1,5-Dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid

A solution of H₂SO₄ (18 M, 2 mL), ethanol (10 mL) and distilled water (10 ml), was used to dissolve (0.5 g, of (A) (1.39 mmol). An aqueous solution (2 mL) of NaNO₂ (0.0144 g, 1mmol) was added dropwise, while the temperature of the mixture was maintained between 0 and 5°C. After that, the diazonium chloride was added with constant stirring to a cold ethanolic solution of m-hydroxybenzoic acid (0.192 g, 1.39 mol), and then a solution of 1 M NaOH (25 ml) was added to the dark colored mixture. The mixture was stirred for 1 h at 0 °C and acidified with 1 mL of conc. HCl. The brown product formed was filtered off and recrystallized from an ethanol-water (1:1) solution and then dried. Yield: 62.2 % (0.44 g), mp 390°C as shown in Scheme 1.

 

Scheme 1. Synthesis of 2-[1, 5-dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-
phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid (LH)

 

¹H NMR (DMSO-d₆, ppm): 1.89 (s,C-CH₃), 2.10 (s,arom-CH₃), 3.43 (s, NCH₃), 3.30 (t, NCH₂), 2.74 (t, CCH₂), 4.49(s,O-H phenol), 7(d,C₂₅-H), 7.23(s,C₁₅-H), 7.36(m,C_7,11-H), 7.44(m,C_9,18,21-H), 7.85(d,C₂₄-H) 7.90(m,C_8,10-H), 8.08(d,C₁₇-H), 12.11(d,N-H), 13 (s,O-H carboxylic).¹³C-NMR (100.622 MHz, DMSO-d₆) δ 16.39(C₂₀), 18.87(C₃), 38.79(C₁₃), 45.6(C₁₂), 58(C₁), 98(C₁₇), 100(C_7,11,14), 106(C₂₅), 110(C₁₈), 111(C₂₃), 111(C_15,21), 118(C₄), 123.77(C₉), 127(C₂₄), 128(C₂₆), 129(C₁₉), 130(C_8,10), 140(C₆), 144(C₂₇), 146(C₂₂), 146(C₂), 151(C₅), 152(C₂₉), 182(C₂₈), (MS) m/z 508 (C₂₉H₂₈N₆O₃), 345 (C₁₈H₁₅N₅O₃)^2-, 159 (C₁₁H₁₃N).

2.4. Syntheses of metal complexes

Ni^II, Co^II, Cu^II, Pd^II and Pt^II complexes were prepared by adding 10 mL of an ethanolic metal salt (4 mmol) to an ethanol/chloroform (1:1 v/v) solution containing 8 mmol of the ligand (LH) and the mixture was refluxed for 6 h. The obtained solution was left at room temperature and the resulting precipitates were filtered off, washed with ethanol and then recrystallized from an ethanol/ chloroform (1:3 v/v) solvent mixture.

2.5. Microbiological investigations

The filter paper disc method was applied according to Gupta et al.¹⁷. The test bacteria were seeded in tubes with nutrient broth (NB). The seeded NB (1 mL) was homogenized at 45°C in the tubes with 9 mL of melted nutrient agar (NA) and the homogeneous suspensions were poured into Petri dishes. The discs of filter paper (diameter 4 mm) were ranged on the cooled medium. After cooling the formed solid medium of the investigated compounds were applied using a micropipette. After incubation for 24 h in a thermostat at 25-27 °C, the inhibition (sterile) zone diameters of the discs were measured and expressed in mm. An inhibition zone diameter over 7 mm indicates that the tested compound is active against the bacteria under investigation. The antibacterial activities of the investigated compounds were tested against Escherichia coli and Pseudomonas aeruginosa as Gram negative, Bacillus subtilis and Staphylococcus aureus as Gram positive. The concentration of each solution was 10^-3 M, commercial DMSO was employed to dissolve the tested samples.

2.6. Programs used in theoretical calculation

Hyper Chem-8 program is a sophisticated molecular modeler, editor and powerful computational package that are known for its quality, flexibility and ease of use, uniting 2D visualization and animation with quantum chemical calculations, molecular mechanics and dynamic. PM3 is more popular than other semi-empirical methods due to the availability of algorithms and more accurate than with other methods. PM3/TM is an extension of the PM3 method to include orbital's for use with transition metals. It has parameterized primarily for organic molecules and selected transition metals. In the present work, parameterization method 3 (PM3) was used for the calculation of heat of formation and binding energy for all metal complexes.

3. RESULTS AND DISCUSSION

All the prepared complexes in this paper were insoluble in water but soluble in dimethyl formamide. The range of conductance values in DMF which are listed in table 1 indicates that all the metal complexes have a non-electrolyte nature. Thus, the molar conductance value indicate that the Cl anion is in the first coordination sphere of the metal^{15, 17, 18}. The physical properties and elemental analysis data are listed in Table 1.

 

Table 1. Physical properties, conductivity and analytical data of the free ligands and its complexes

d= decomposes

 

3.1. Electronic spectra and magnetic moments

The electronic spectrum of the free ligand (LH) shows two bands at 275 nm and 300 nm which are attributed to π® π* and n® π* transitions respectively. The electronic spectrum of the Co^II complex exhibits three absorption band at 400, 500 and 648 nm which were attributed to ⁴T₁g_(F) ® ⁴A₂g_(F), ⁴T₁g_(F) ® ⁴T₁g_(P) and ⁴T₁g_(F) ® ⁴T₂g_(F) respectively. Furthermore, the magnetic moment of the Co^II (d⁷) complex was found to be 5.01 B.M., which is higher than the spin only calculated value, difference that can be attributed to the orbital contribution. All the above mentioned data correspond to an octahedral geometry^19-22.

The electronic spectrum of the yellow-green Ni^II complex shows bands in the visible region at 394, 490 and 650 nm, which are assigned to the d-d electronic transitions ³A_2g(F) ® ³T_1g(p), ³A₂g_(F) ® ³T₂g_(F) and ³A₂g_(F) ® ³T₁g_(F) respectively. The value of μ_eff of the Ni^II complex d⁸ is 2.82 B.M; this value is in agreement with the spin-only value. All these results for the Ni^II complex confirm an octahedral geometry²⁰.

The copper complex exhibits absorption bands at 289 and 385 nm which are assigned to charge transfer transition (M® L). Besides, the complex shows a band in the visible region at 590 nm which can be assigned to 2Eg® ²T₂g_(D). The μ_eff of the Cu^II complex d⁹ was found to be 1.82 B. M within the expected value for one electron²³.

The diamagnetic Pd^II d⁸ low spin complex exhibits absorption bands at 410 and 492 nm which assigned to ¹A₁g ® ¹A₂g and another band at 790 nm which can be assigned to ¹A₁g ® ¹B₁g. These assignments correspond to a square planar Pd^II complex^{20, 24}.

Finally, the spectrum of brown Pt^II complex show electronic transitions of ¹A₁g ® ¹T₂g and ¹A₁g ®¹T₁g at 495 and 792 nm respectively. Table 2 gives the electronic spectral bands and the magnetic moments of the ligand and its complexes.

 

Table 2. Magnetic susceptibility and electronic specta of the ligand and the reported complexes

 

3.2. Infrared spectra studies

The main vibrational bands of the FTIR spectrum were assigned to the functional groups of the Azo-Schiff base ligand LH. The spectrum of the ligand shows strong bands at 3699, 3429, 3234, 1728, 1601, 1444, 1342 and 1288 cm^-1 that are assigned to the v(OH) carboxyl, v(OH) phenolic, v(NH), v(C=N), v(COO) asymmetrical, v(N=N), v(COO) symmetrical and v(CO) phenolic respectively^25-27. On complex formation the bands of v(C=N), v(N=N) and v(COO) are shifted to lower frequencies by (39 to 44 ), (8 to 18 ) and ( 3 to 8 ) cm^-1 respectively; these shifts confirm the coordination of the ligand through the nitrogen of the azomethine group, and the azo group and the carboxylate ion with the metal ions. Moreover, the spectra of the complexes exhibited weak bands between (534-553) cm^-1 and (437-454) cm^-1 which are attributed to v(M-N) and v(M-O) respectively. This indicates that the ligand is coordinated to the metal ions through the N and O atoms. Besides, the spectra of the complexes present weak bands between 407-412 cm^-1 which can be assigned to v(M-Cl)²⁸. Characteristic vibrations and assignments of free the ligand and its complexes are reported in Table 3.

 

Table 3. The IR spectra bands (cm^-1) of the free ligand and its complexes

Ph=phenolic, ca=carboxylic, as=asymmetric, s=symmetric

 

3.3. Thermal analysis TGA

To understand the thermal decomposition processes of the studied compounds, the azo-Schiff base ligand and its metal complexes were examined by thermo gravimetric analysis in the temperature range of 30-700 °C. The obtained results from the TG curves for all these compounds are given in Table 4. The decomposition was complete at 693 °C for all the complexes.. The comparison of the thermograms of the ligand and the complexes shows that the complexes are more thermally stable than the Azo-Schiff base (10- 35 °C). The final decomposition products were metal Pd complex in (600°C), metal oxide CoO in the 696 °C, NiO 698 °C and PtO 598 °C) and metal mixture formed above 600 °C for the Cu complex.

 

Table 4. Thermal analysis data of the metal complexes derived from L.

 

The thermal data have been analyzed for thermodynamic parameters by using Coats- Redfern method. From the half decomposition temperature, the relative thermal stability of the compounds is: NiL > CoL >PdL >CuL> PtL > L

(L)=C₂₉H₂₈N₆O₃ [101.131% Found (99.999% Cal) (158-348°C) →C₂₃H₂₃N₅O₃ [82.648%Found (82.085% Cal)] (348-598 °C) → C₆H₅N^-[18.483% Found (17.914%Cal); C₂₉H₃₁N₆O₅ClCu (642.59) (35-142°C) →2H₂O [4.931% Found (5.607%Cal)]; C₂₉H₂₇N₆O₃ClCu (606.59) (142-435°C) → C₉H₁₁N [22.003% Found (20.716% Cal)]; C₂₀H₁₆N₅O₃ClCu (473.59) (435-600°C) → C₁₃H₁₂N₃Cl [38.174% found (38.239% Cal); C₇H₄CuN₂O₃ [35.438% Found (35.358% Cal)].

Total wt. loos= 65.003% Found (64.562% Cal) and final residue: 34.997% Found (35.438% Cal)

C₂₉H₂₇N₆O₃ClPd (649.44) (35-412°C) → C₁₈H₁₇N₃ [42.814% Found (42.344 %Cal)];C₁₁H₁₀N₃O₄ClPd (390.44) (412-600°C) → C₁₁H₁₀N₃O₂Cl [44.124% Found (41.19 %Cal)]; Pd [13.062% Found (16.387%Cal)]

Total wt. loos= 86.938% Found (83.534% Cal) and final residue: 13.062 % Found (16.466 % Cal)

C₂₉H₃₁N₆O₅ClNi (637.74) (45-170°C) → 2H₂O +CH₇ClO [16.823% Found (16.707%Cal)]; C₂₈H₁₈N₆O₂Ni (567.24) (170-355°C) → C₇H₁₀N₂ [20.175% Found (19.156% Cal)]; C₂₁H₈N₄O₂ (348) (355-698°C) → C₂₁H₈N₄O [52.903% Found (54.004% Cal); NiO [10.099% Found (11.712% Cal)]

Total wt. loos= 89.901% Found (89.867% Cal) and final residue: 10.099% Found (10.133% Cal)

C₂₉H₃₁N₆O₅ClCo (637.98) (45-150°C) → 2H₂O +C [7.647% Found (7.528%Cal)]; C₂₈H₂₇N₆O₃CoCl (589.95) (150-430°C) → C₇H₁₀N₂ClO₂ [31.601% Found (29.725% Cal)]; C₂₁H₁₇N₄O (341) (430-696°C) → C₂₁H₁₇N₄ [52.310% Found (50.942% Cal); CoO [8.442% Found (9.237% Cal)]

Total wt. loos= 91.558% Found (88.195% Cal) and final residue: 8.442% Found (11.745% Cal)

1-C₂₉H₂₇N₆O₃Cl₃Pt (809) (45-145°C) → C₃ H₆ [4.931% Found (50191%Cal)]; C₂₆H₂₁N₆O₃Cl₃Pt (767) (145-445°C) → C₈H₁₀Cl₂ [22.003% Found (21867%Cal)]; C₁₈H₁₁N₆O₃ Cl Pt (590.096) (445-598°C) → C₂₂H₁₇N₅ [47.166% Found (47.213%Cal)]; ptO [25.906% Found (25.729%Cal)]; Total wt. loos= 74.094% Found (74.271% Cal) and final residue: 25.906% Found (25.729% Cal)

3.4. Kinetic study

Coats-Red fern is the method mentioned in the literature related to decomposition kinetics studies; this method is applied in this study²⁹. From the TG curves, the activation energy, E, preexponential factor, A, entropies, ΔS, enthalpy, AH, and Gibbs free energy, AG, were calculated by Coats-Redfern method; where:

ΔH = E - RT and ΔG = ΔH - TΔS

The linearization curves of Coats-Red fern method. Kinetic parameters are calculated by employing the Coats- Red fern equations, are summarized in Table 5. The Coats-Red fern equation²⁹ may be written in the form:

 

Table 5. Thermodynamic parameters of the ligand and metal complexes.

 

where α is the mass loss at the completion of the reaction, R the gas constant, Ea the activation energy in J mol^-1 and q is the heating rate. Since 1-2 RT/Ea≈ = 1, a plot of the left-hand side of the above equation against and ΔE* was calculated from the slope and A (Arrhenius constant) was found from the intercept. The activation entropy ΔS^*, the activation enthalpy ΔH^* and the free energy of activation ΔG* were calculated using the following equations:

S* = 2:303 (log Ah/ KT) R; H* = E*- RT; G* = H*- T_SS*

Where K and h are the Boltzmann's and Plank's constants, respectively. The calculated values of ΔE^*, ΔS^*, ΔH^* and ΔG^* for the dehydration and the decomposition steps are given in Table 5. The activation energies of the decomposition were found to be in the range 134-208 J mol^-1.According to the kinetic data obtained from TGA curves, the negative values of activation entropies ΔS^* indicate a more ordered activated complexes than the reactants and/or the reactions are slow³⁰.

3.5. Microbiological Investigation 

The biological activity of ligand L and its complexes were tested against bacteria, we used more than one test organism to increase the chance of detecting antibiotic principles in tested materials. The organisms used in the present investigation included two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aereuguinosa). The results of the bactericidal screening of the synthesized compounds are recorded in Table 6. An influence of the  central ion of the complexes in the antibacterial activity against the tested  Gram positive and Gram negative organisms show that the complexes have an  enhanced activity compared to the ligands itself.

 

Table 6. Antibacterial activity data of ligands and its complexes inhibition zone (mm).

Key to interpretation: less than 10 mm=inactive, 10-15 mm= weakly active,
15-20 mm=moderately active, more than 20 mm=highly active.

 

3.6. Theoretical study

The vibration spectra of the A and Azo -Schiff base L was calculated by using a semi-empirical (PM3) method. The results obtained for wave numbers are presented in Table 7, and the comparisons with the experimental values indicate some deviations. These deviations may be due to the harmonic oscillator approximation and lack of electron correlation. It was reported Chamberlain, et al. that frequencies coupled with Hartree- Fock Theory (HFT) approximation and quantum harmonic oscillator approximations tend to be 10% too high^31,32.

 

Table 7. Conformation energetic in (K J.Mol^-1) for the starting material (A) ,L and metal complexes.

 

3.6.1. Optimized Geometries Energy of metal complexes for A and Azo-Schiff base

Theoretically probable structures of metal complexes with (A) and Azo-Schiff base were calculated to search for the most probable model building stable structure, these shapes, show the calculated optima geometries for L and their metal complexes as shown in Figs. 1 and 2. The results of PM3 method of calculation in gas phase for the binding energies and heat of formation of Co(II),Ni(II),Cu(II) and Pd(II) complexes, are described in Table 7 and 8.

 

Fig.1. Conformational Structure of A, ligand and their Complexes

 

Fig. 2. The calculated vibrational frequencies of starting material A(a) and ligand L (b)

 

Table 8. Comparison of experimental and theoretical vibration frequencies for ligands

*: Experimental frequency,**:Theoretical frequency, ***:Error % due to main difference in
the experimental measurements and theoretical treatments of vibration spectrum.

 

3.6.2. Electrostatic Potential (E.P)

Electron distribution governs the electrostic potential of molecules and describes the interaction of energy of the molecular system with a positive point charge, so it is useful for finding sites of reaction in a molecular positive charged species tend to attack a molecule where the E.P. is strongly negative electrophilic attach³¹. The E.P of free ligand was calculated and plotted as 2D contour to investigate the reactive sites of the molecules, and one can interpret the stereochemistry and rates of many reactions involving soft electrophiles and nucleophiles in terms of the properties of frontier orbitals (HOMO and LUMO). Overlap between the HOMO and LUMO values were plotted as 2D contour to get more information about these molecules. The results of calculation showed that the LUMO of transition metal ion prefers to react with the HOMO of nitrogen atoms of Azo- Schiff base ligand as shown in Fig. 3.

 

Fig. 3. HOMO and Electrostatic Potential as for starting material and L

 

4. CONCLUSION

New Co^II, Ni^II, Cu^II, Pd^II and Pt^II metal complexes with Azo-Schiff base derived L₁ from reaction m-hydroxy benzoic acid with 1,5-Dimethyl-3-[2-(5-methyl-1 H-indol-3-yl)-ethylimino]-2-phenyl-2,3-dihydro-1 H-pyrazol-4-ylamine have been synthesized. All the complexes are insoluble in water but soluble in DMF, as well as all of them are non-electrolyte. The structure of the complexes based on Uv-Vis, IR, mass spectroscopy were proposed that the Azo-Schiff base Ligand L behave as tridentate which coordinated with the metal ions through N, N, O atoms. It can be suggested that the geometry of the Co(II), Ni(II) and Cu(II) have octahedral geometry as shown in Fig. 4, Pd(II) and Pt(II) complexes have square planer geometry as shown in Fig. 5 (a and b).Hyper Chem-8 program was used to predict structural geometries of compounds in gas phase. The heat of formation (ΔHf°) and binding energy (ΔEb) at 298°K for the free ligands and its vanadyl complexes was calculated by PM3 method. The synthesized ligands and its metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aereuguinos).

 

Fig.4. Structure of octahedral complexes

 

Fig.5. (a) Structure of the [PtLCl₃] complex and (b) Structure of the [PdLCl] complex

 

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