Synthesis, Structural and Biological Studies of Some Metal Complexes derived from Tridentate Pyrazole-based Ligand

 

Taghreed M. Musa, Zaizafoone N. Nasif, Mahmoud Najim Abid Al-jibouri

Mustansiriyah University, Department of Science, College of Chemistry, Baghdad.

 

ABSTRACT:

The new derivatives of heterocyclic resulting, studying spectral Cobalt(II), Nickel(II), Copper(II), and Cadmium (II) with new tridentate ligand namely [3-{1-acetyl-4-[4- (dimethylamino)phenyl]-1H-pyrazol-3-yl}-4-hydroxy-6-methyl-5,6-dihydro-2H-pyran-2-one] which was formed by the (E)-3-(3-(4-(dimethylamino) phenyl)acryloyl)-4-hydroxy-6-methyl- 2H-pyran-2-one with excess of hydrazine monohydrate in glacial acetic acid. NMR, FTIR, MS spectra as well as the elemental analyses, identified the new ligand and TLC was carried out to confirm their structures. The Cobalt (II), Nickel (II), Copper (II) and Cadmium (II) were precipitated by direct reactions of their chlorides with the solution of the ligand in 2:1 molar ratios. All complexes have been identified on the basis of the preliminary analysis, infrared, ultraviolet spectra of the visible moments of magnetic conductivity measurements were conducted for radiation conclude the octahedral geometry around Cobalt (II), Copper (II), and Nickel (II). The Cadmium (II) complex was investigated as tetrahedral in 1:1 ratio. The biological activity of the ligand and its metal complexes in DMSO against some bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and P. aeruginosa). Effected of the syntheses of HL ligand, [Co(L)₂] and [Cu(L)₂] complexes were studied on Acetylcholinesterase (AChE) in healthy human serum. Results indicated that all of the compounds displayed moderate and selective AChE inhibitory activity. The complexes of [Cu(L)₂] and [Co(L)₂] showed inhibition constant in the range (Ki: 8.333×10^-4, 3.159×10^-12, 2.5×10^-6, 3.333×10^-4 M respectively) higher than HL ligand (1.1×10^-4, 1.964×10^-12 respectively) M for AChE.

 

 

 

INTRODUCTION:

The chemistry of pyrazoline derivatives have been many interesting by researchers due to the novel applications in bioinorganic and photochemistry have described in a numeral of reviews in which the chief methodologies to the synthesis of revealed heterocyclic rings and their biological activity were investigated^1,2. The great applications of d-block complexes derived from polydentate pyrazoles have devoted the researchers to prepare novel ligands^3,4. The coordination chemistry of pyrazole ligands has attractive interests by the                    scientists⁵ pharmacological industry^5-8.

 

As well as, the anticancer drugs from (II), and (II) chelates with polydentate ligands of pyrazole have extensively spread out in bioinorganic chemistry^9,10. Pyrazole derivatives are also well recognized in the literature as significant biologically effective heterocyclic compounds. These derivatives are the topic of numerous studies due to their extensive potential pharmacological activities such as analgesic, antidepressant, antibacterial, research vegetable growth regulatory, reduce inflammation, anti-diabetic and activities^11,12.

 

MATERIAL AND METHODS:

Instrumentation:

The chemicals were used with high purity. Solvents such as DMF and ethyl alcohol, chloroform and DMSO were bought from Sigma Aldrich Company and used. Commercial methanol was purified by distillation and used. The starting materials like para-(dimethylamino) benzaldehyde, dehydroacatic acid, hydrazine hydrate 80%, glacial acetic acid, and hydrochloric acid were used as purchased from Sigma-Aldrich Company. Determination of melting points on the electro thermal capillary gadget. The FTIR measurements were registered on a Shimadzu model FTIR-8400S. Recording Mass spectra on a Shimadzu GCMS-QP2010 Ultra gadget. The NMR spectra were obtained using CDCl₃ as solvent and TMS as internal standard on Bruker 300MHz NMR spectrometer at Al-Bait university-Amman (Jordan). The elemental investigates were carried out using Carl – Erba CHN analyzer model 1108 model. The metal percentage analyses were conducted using FAAS on Shimadzu 670AA Flame atomic spectrometer at the University of Mustansiriyah via standard addition method¹². The Ultraviolet-visible spectra were registered using 0.001M solutions of ligands and complexes in ethyl alcohol and dimethylformamide. The IR of the compounds were registered. The mass spectra of the chalcone and 2-pyrazoline ligand were done with accelerating voltage, 10 kv MS spectra at chemistry department, college of science, Mustansiriyah University. The magnetic susceptibility of the solid complexes were done at 300 K on Sherewood Magnetic balance apparatus with calibration of CuCl₂.2H₂O at service laboratory of Chemistry Department, College of Science, Mustansiriyah University. The thermal analyses TG/DTG of the metal complexes were carried out at helium inert gas with Tonosi -Thermo with a heating rate of 10 C/min.at Ibn-Haithum College for pure science-Baghdad-University.

 

Preparation of chalcone derivative (A)

The chalcone derivative was prepared according to the procedure specified in the literature¹³. To a solution of 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one (1mmole) in ethanol (10mL), sodium hydroxide (40%, 1mL) was added and the mixture was stirred for 30 minutes. Then para-(dimethylamino) benzaldehyde (1mmole) was added and the reaction mixture was stirred overnight. It was allowed to the reaction mixture to stand at room temperature. The solid precipitates nomination and recrystallized from absolute ethanol, Scheme1.

 

Synthesis of 3-(1-acetyl-4-(4-(dimethylamino)phenyl)-1H-pyrazole-3-yl)-4-hydroxy-6-methyl-2H-pyran-2-one⁷

The solution of (2.299g, 0.01mol) of chalcone (A) was dissolved in (30mL) of acetic acid glacial then (0.15 mol) of hydrazinium hydroxide was added and refluxed the mixture at (6 hr), then decanted to ice water and a precipitate produced was filtered and washed with water and recrystallized with diethyl ether Scheme 2, Table1.

 

Synthesis of metal complexes:

Dissolve (0.171g, 1mmole) of  hydrated Copper (II) chloride in aqueous solution then add gradually to stirred warmed solution of (0.726g, 2mmol) of the HL in (25 mL) of ethyl alcohol then the mixture was refluxed at (2 hr) then a green crude was separated, filtered, washed several times with ethyl alcohol and diethyl ether. In addition to, the preparation of Cobalt ( II), Copper(II), Cadmium (II) and Nickel (II), complexes were completed in the comparable procedure by using metal chlorides and the periods of completion reactions at (2-3 hr),

 

Biological activity:

Antimicrobial activity:

The screening of biological; activity was determined by agar well diffusion method as reported elsewhere 12. For antibacterial test the organisms used were 10mL of bacterial suspension, Gram negative - Escherchia coli, Gram positive-Staphylococcus aureus on Mueller–Hinton agar on age 24 hrs pour into the plates.

 

2-Determination of AChE activity:

Human serum AChE activity was determined using method as follows¹⁴:

(50μL) of DTNB solution (0.001M) is added to (2.25 ml) of sodium phosphate buffer solution (pH=7.3, 0.2M), then added (10μL) of serum, mixed well and (2 ml) of the mixture is transferred to a measuring cell (1cm) after that. Then (34μL) of acetyl thiocholineiodide (ASChI 0.06M) is added. The changes in absorbency are measured before and after adding the substrate at (430 nm) for (3 min). The enzyme activity is calculated as concentration in μ mole of the substrate hydrolyzed to each (ml) of samples in (3min) and expressed as (μmole/3min/ml).

 

Determination of biological activity of prepared HL ligand, [Cu(L)₂] and [Co(L)₂] complexes:

A stock concentration solution (0.01M) concentration of each complex in Table (1) has been prepared and then different concentrations (10^-2, 10^-3, 10^-5, 10^-7, 10^-9 and 10^-11 M) of each complex were prepared by diluting it with dimethyl sulfoxide (DMSO) as solvent. ChE activity is measured in human serum as follows:

 

(50μL) of DTNB solution (0.001M) is added to (2.25 ml) of sodium phosphate buffer solution (pH= 7.3,0.2M), 0.25ml of inhibitor was mixed with 2ml of the same buffer, then (10μL) of serum is added, mixed well and (2ml) of the mixture is transferred to a measuring cell (1cm),then (34μl) of (AChI 0.06M) was added, the changes in absorbency is measured after adding the substrate at 430 nm for 3 min. The inhibition percentage was calculated by comparing the activity between with and without inhibitor under the same conditions according to the equation:

                                   The activity in the presence of inhibitor

% Inhibition = 100 - --------------------------------------------------- x 100

                                   The activity in the absence of inhibitor

 

Determination the type of inhibition ¹⁵:

A constant concentration of inhibitors (lower and higher) were being used with different concentrations of substrate (0.02, 0.04, 0.06, 0.08 M) to study the type of inhibition (10^-3 M was considered as maximum inhibition instead of 10^-2M which excluded due to it was very high colored and concentrated solution). These concentrations were prepared using the stock solution (0.1M) of AChI. The enzyme activity was determined with and without the inhibitors using the linewer-burk equation by plotting 1/V vs. 1/[s] following values were then calculated as follows*1) Ki, 2) Apparent Vmax (Vmapp), 3) Apparent Km (Kmapp), 4) type of inhibition.

 

RESULTS AND DISCUSSION:

The intermediate compound consists [A] through the condensation Claisen-Schmidt at room temperature. The succeeding reaction of the chalcone (A) with hydrazinium hydroxide produced hydrazine derivative which followed ring closure upon attacking of – NH- on HC=C- to formed in the glacial carboxylic acids as a solvent. The new ligand was identified with the help of mass spectra, FTIR, and NMR spectroscopy methods. The solid complexes of (cobalt, nickel, copper, and cadmium) (II) were isolated from their solutions reactions with the methanolic solution of (HL) ligand after adjusting the conditions involving the time of reaction, pH, and the molar ratios of (M:L) via Job-method ¹³. All complexes insoluble in organic solvents such as methyl and ethyl alcohol, methyl trichloride and sparingly soluble in acetonitrile, while it is soluble in DMSO and DMF were great, so were made molar conductivity measurements and electronic spectra in DMSO. The compositions of the synthesized compounds were powered by compared to their observed (carbon, hydrogen, and nitrogen) elemental analysis with the theoretical values, Table (1).

 

Table. 1. Some of the physical properties and elemental analysis of the ligand and its metal complexes.

Mass spectra:

The mass spectra of the chalcone (A) displayed a molecular ion m/e= 298 which is assigned to the expected molecular weight of the prepared chalcone with C₁₇H₁₇NO₄ formula, Figure (1). As well as, the MS spectrum of the ligand HL showed the apparent peak at m/e =353 that is suggested to the ring closure of chalcone (A) with hydrated hydrazine to afford the 2-pyrazoline-based ligand with proposed formula C₁₉H₁₉N₃O₄ formula, Figure (2).

 

NMR spectra:

The ¹HNMR (HL) showed a single peak at 1.88 ppm due to methyl protons, the reasons at 2.47 ppm assigned the chemical shift at the methyl group that bonding the pyrazole ring. The signal at 3.32 ppm was due to –N-CH₃. The two multiple signals appeared around (6.60-7.61) ppm may be associated with the aromatic protons Ar-H¹². As well as the singlet absorption at 8.72 ppm results from the nuclear spin of amide –NH proton^11,12. The disappearance of the peak in NMR for acidic proton –OH may be attributed to the H-exchange with the water present in chloroform solvent. For the same reason, the resonance of –OH with –CH=CH- in pyranone ring may lead to the overlapping of signals in the region 8.5-9.0 ppm, Figure (3).

 

FTIR spectra:

The FT-IR spectra of the chalcone derivative displayed strong absorptions at 1685, and 1612cm^-1 which are resulted from asymmetric vibrations of –C=O and –CH=CH- of the Alfa-metal-carbonyl compounds, Figure (4). The absence of the absorptions carbonyl moiety in the FT-IR spectra of the free ligand, Figure (5), confirmed the formation of ring closure to afford 2-pyrazoline ligand (L). As well as, the observation of new bands around (3433-3340), and (1627-1454) cm^-1 assigned to vibration modes of -OH, –NH and –C=N– of the pyrazoline ring respectively¹⁶. However, the FT-IR spectra of all metal complexes changes in the positions and intensities of the imine-C=N-, and –NH- groups which confirmed the participation of two nitrogen atoms of pyridine and 2-pyrazoline rings in coordination with the metal ions¹⁷. The appearance of strong absorptions in the regions (1610-1612) cm^-1, (1580-1577), and (1320-1280) cm^-1assigning to –C=N- and –C-N- moieties of pyrazoline and pyridine respectively, the five-member ring creation was then shown with ions nickel(II), cobalt(II), cadmium(II) and copper(II). The broad bands around (3500-3200) cm^-1 besides the bending of coordinated water molecules in the regions (1560-1550) cm^-1, and 845-822 cm^-1 supported the –OH coordinated by water in the inner sphere of metal complexes^18,19. Furthermore, the IR spectrum of the cadmium (II) complex showed weak to medium bands around 250-375 cm^-1 supporting Cd-Cl bonds, Figure (6). The lower frequency regions of IR spectra of all complexes recorded weak bands around 422-570 cm^-1 that are attributed to M-N bonds^18,19.

 

Electronic spectra and magnetic properties of the synthesized complexes:

The Ultraviolet-Visible spectra of the free HL in ethyl alcohol (0.001 M) recorded high-intensity peaks around 250, and 310 nm, Figure (7) which are resulted from π→π*and n—π* respectively^9,16. The green solution of Cobalt(II) in DMSO showed three spin-allowed transitions around 950, 600, and 345 nm that are assigned to ⁴T₁g→ ⁴T₂g(F),⁴T₁g→⁴A₂g(F) and ⁴T₁g → ⁴T₁g(P) respectively ¹⁷, thereby confirmed the octahedral environment around Cobalt(II) ion. By the same way, the complexes solution of Nickel(II) in DMSO displayed two weak absorptions in the regions 750-480 nm and other intense peaks at 375 nm which are ascribed from ³A₂g→ ³T₂g(F),³A₂g→³T₁g(F) and MLCT respectively. The agreement of the splitting energies for Cobalt (II) and Nickel (II) complexes in the range 667-160 KJ/mole indicates the high-spin octahedral geometry complexes about Cobalt (II) and Nickel (II) ions. Furthermore, the green solution of Copper (II) complex in DMSO exhibited a broad peak at 835 nm that is due to the resolution transitions of ²B₁g→²B₂g, and ²B₁g→²Eg thereby supports the distorted octahedral environment around Copper (II) ion ^20,22. The pale yellow color of Cadmium (II) in DMSO may have gave from LMCT in the region 275-336 nm, Figures (8) and (9). The magnetic moments of complexes Cobalt (II), Nickel (II), and Copper (II) complexes obtained from Faraday's method at 295 K were found to be 4.65, 2.88, and 1.80 BM respectively. These values correspond to the existence of three, two, and one unpaired electron in the d-shell of the metal ions respectively ^21,22. The increase in the magnetic susceptibility of Cobalt (II) complex may be caused by the orbital contribution of electron motion in the t₂g level, Table 2.

 

Table2. UV-Visible absorptions in DMSO, molar conductivity and magnetic moments of the prepared complexes.

Λ=molar conductance in DMSO solutions of 10^-3 M concentration.

 

Thermal analyses:

The TG-DSC diagram of Cobalt (II) complex, recorded loss weight around temperature range (50-594.4)°C is already indicated to one decomposition step. The TGA peak observed at 594.4°C indicated the loss (C₂₀H₂₆O₂) fragment (exp.=9.77mg. 83.0457%, calc.=9.93mg) The final residue of the ligand recorded above 600°C assigned to the (exp.=2.33mg, 16.95%, calc.=2.07mg) attributed to the [C₂N₂O]. The peak at 323.2°C indicate to exothermic decomposition procedures this peak may be related to the paralysis of the organic ligand in argon, Figure (4). The graph for [Co (L)₂] refers to Co(II). The TGA peak recorded at 293.18°C assigned to the loss of (C₂₃H₃₂O₂NS), (exp.= 3.97 mg, 30.67%, calc.=4.021 mg).

 

The thermogravimetric analysis of the Copper(II) complex, Figure (5) exhibited in argon gas, and are presented and showed in figures (8,9). The TG curve of Cobalt(II) complex show weight losses in two exothermic decomposition at 12.22% in the temperature ranges (210-240) and (350 – 430)°C respectively with endothermic processes of thermal decomposition thereby agree well with the thermograms of DSC which proves the constancy complex of Cobalt(II) ²³.

 

Anti-microbial studies:

This research depicted the In Vitro assay of HL and all the complexes synthesized against several microbial species. The In Vitro assay achieved by well diffusion method using two concentrations of compounds (10-100 mg/mL) in DMSO. The HL exhibited potent antimicrobial activities. The Copper (II) complex showed greater inhibition zones against all bacterial species as well as Candida albicans at 10 and 100 mg/mL, on the other hand, complexes also show excellent inhibition at 100 mg/mL, Figure (6) and Table 3. The comparison of inhibition zones (mm) among metal complexes investigated that the chelation theory proved that Copper (II) complex exhibited more toxicity rather than the free ligand due to the lipids structure or micelles on the surface of bacteria and fungi cells^24,25.

 

Table 3. Antibacterial activities of compounds.

Compounds	inhibition zone (mm) at 100 and 10* mg/mL
	Gram negative		Gram positive
	E. coli	P. aeruginosa	S. aureus	B. subitilis	S. pyogenes
HL	3	2	2	4	2
[Co(L)2]	9	8	8	7	6
[Ni(L)2]	-	3	4	5	3
[Cu(L)2]	4	4	-	5	4
[CdLCl]	2	3	3	3	2
Amoxicillin	10	17	16	17	12

 

Determination of AChE activity:

Before each set of inhibition experiments were conducted, the AChE activity was measured by using four different concentrations of acetyl thiocholineiodide (substrate) (0.02, 0.04, 0.06, 0.08) M as in Figure. (7). The effect of different concentrations of each inhibitor at acetylcholine concentrations on AChE activity is illustrated in figure. 8.

 

The complexes of [Cu(L)₂] and [Co(L)₂] had effective inhibitory activity of AChE as clear in they than corresponding free close ligand. The biochemical tests indicated that pyrazole complexes have caused noticed inhibitory effects on enzyme activity compared with the measured normal values of enzyme activity 2.06 μ_mol/2min/ml, Table (4).

 

Table 4. The effect of different concentrations of pyrazole complexes on the human serum AChE activity.

Samples	Inhibition con. (M)	AChE activity μmol/2min/ml	%Inhibition
control	zero	2.06	-
HL	10-2	0.025	98.78*
	10-3	0.65	68.44
	10-5	0.7	66.01
	10-7	0.925	55.09
	10-9	1.0125	50.87
	10-11	1.337	35.09
[Cu(L)2]	10-2	0.125	93.93*
	10-3	0.7	66.01
	10-5	0.825	59.95
	10-7	1.362	33.88
	10-9	1.377	33.49
	10-11	1.4	32.03
[Co(L)2]	10-2	0.162	92.13*
	10-3	1.162	43.59
	10-5	0.887	56.94
	10-7	0.987	52.08
	10-9	1.037	49.66
	10-11	1.15	44.17

*Maximum inhibition concentration in each complex, which excluded during kinetic study due to its very high colored and concentrated solutions.

 

Table 4 showed that the greater inhibition percent was found at concentrations (10^-2) M for each complex, these can be attributed to the presence of more than one nucleophile sides in two compounds (N-phynel, hydroxyl, carbonyl) groups which may led to good orient to active site gorge of enzyme which includes Tyr70, Asp72, Tyr121, Glu278, Trp279 and Tyr334 residues that are important for binding interactions of the inhibitors⁽²⁶⁾.

 

Study Type of Inhibition:

The second part of this study is to determine the type of inhibition and kinetic parameters (Km, Vmax, and Ki) at different concentrations of substrate and under the same conditions by using Lin weave-Burk equation as shown in Figure (7 – 9) and Table (5).

 

Table 5. The kinetic properties of AChE with and without HL ligand, [Cu(L)₂] and [Co(L)₂] complexes.

Sample	Inhibitor	Km (M)	Vmax (μmol/ml/min)	Ki (M)	Inhibition type
	Conc. (M)
Control	Zero	0.033	3.3	-	-
HL	10-3	0.333	3.3	1.1× 10-4	Competitive
	10-11	0.055	0.909	1.964× 10-12	Mixed
[Co(L)2]	10-5	0.0333	0.666	2.5× 10-6	Non competitive.
	10-3	0.0333	0.833	3.333× 10-4	Non competitive.
[Cu(L)2]	10-3	0.0333	1.515	8.333× 10-4	Non competitive.
	10-11	0.0833	2	3.159× 10-12	Mixed

 

From this presentation the study indicated that K_m was varied from higher or the same in the presence of pyrazole complexes compared with non- inhibiting system. A high Km means the lesser affinity of substrate toward  enzyme and the higher inhibitor affinity to fits very well into the active-site cleft of the enzyme which presence in both maximum and minimum inhibitor concentrations of close pyrazole complex at 10^-3, 10^-11 and of Cu(II) pyrazole complex at  10^-11 (mix inhibition, competitive inhibition) in other hand Cu(II) pyrazole complex at10^-3  and Co(II) pyrazole complex at  10^-5, 10^-3does not compute with substrate on the active site of enzyme (noncompetitive inhibition).

 

The affinity is obviously influenced by several factors, for example size, three-dimensional structure, presence of groups which easily bind non-covalently to groups in or close to the active site.

 

The coordination compounds Cu(II) and Co (II) show remarkable inhibition on AChE (Ki: 8.333×10^-4, 3.159×10^-12, 2.5×10^-6, 3.333×10^-4 respectively), having a higher inhibition as compared to close compound (1.1×10^-4, 1.964×10^-12 respectively), which is probably due to complexation of metal(II) ions to ligand^(30,31).

 

All compounds were bound primarily with the anionic subsite of catalytic active site. The ligands were affixed in the active site with pi-pi interactions. Remarkably, all AChE inhibitors were sandwiched between Trp84 and Phe330 by the contribution of aromatic rings. However, the experimental activity trend could be explained more or less by the number and the distance of pi-pi stacking interactions.

 

Phe330 is located in the hydrophobic pocket near the catalytic site of AChE (CAS) and it is known that several AChE inhibitors including tacrine have binding interactions with Phe330⁽³¹⁾. On the other hand, Tyr334 is located in the peripheral site (PAS) of the enzyme and it can be proposed that close compound can interact with the PAS site of AChE. We have already mentioned that the narrow conformation of the AChE enzyme gorge leads small molecules like tacrine and donepezil to fit into the active site easily so it can be speculated that as our compounds are small molecules, they possessed AChE inhibitory activity The high inhibitory potential of Cu and Co complex respectively can be attributed to one extra hydrogen bond formed between hydroxyl hydrogen of both compounds and Gly117.

 

The Vmax value for control sample (3.3 μ_mol/ml/min) was higher than in inhibited samples, so it is clear that the amount of active enzyme Vmax present in non -inhibited system. Another studies were in a good agreement with our results^(26-31) .

 

 

CONCLUSION:

According to the results obtained from elemental analyses, NMR, FTIR, Mass spectra and magnetic moments, the new derivative of 2-pyrazoline behaved as bidentate HL toward the cobalt (II), nickel (II), copper (II), and cadmium (II) ions. All compounds were isolated in the solid state after improving the conditions of the time and the ratio of acidity and molar. The active sites of the ligand in bonding with the metal ions are the two nitrogen atoms of N₂- of pyrazole ring and O- of carbonyl group which building with pyrazole ring and O-dihydroacetic acid group. The scheme (4), shows the octahedral symmetry of the synthesized complexes with the common formula, [M(L)₂] while a distorted tetrahedral geometry about cadmium (II). New preparations HL ligand, [Cu(L)₂] and [Co(L)₂] complexes in vitro screened against many bacterial types besides (Staphylococcus, aureus, Bacillus subtilis, Escherichia Coli and p. aeruginossa). That Table 5 indicates a noncompetitive rise of [Co(L)₂] complexes.

 

ACKNOWLEDGEMENT: 

We are thankful to the service laboratories at Chemistry department, college of science, Mustansiriyah University for measuring the mass spectra, magnetic susceptibility and the electronic spectra. University for analysis of NMR spectra and Ibn-Hithum College of education for pure sciences on analysis of thermograms of the solid complexes.

 

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

 

REFERENCES:

1.      C.-Y. Wu, Y. Chen, S.-Y. Jing, C.-S. Lee, J. Dinda and W.-S. J. P. Hwang, 2006, 25, 3053-3065.

2.      P. K. Sharma, S. Kumar, P. Kumar, P. Kaushik, D. Kaushik, Y. Dhingra and K. R. J. E. j. o. m. c. Aneja, 2010, 45, 2650-    2655.

3.      P. A. S. Oliveira, L. M. Sartori, N. A. Rey, H. F. Dos Santos, M. A. L. De Oliveira and L. A. S. J. J. o. t. B. C. S. Costa, Journal, 2013, 24, 1732-1738.

4.      J.  R. Cheeseman, G. W. Trucks, T. A. Keith and M. J. J. T. J. o. c. p. Frisch, 1996, 104, 5497-5509.

5.      B.  Kupcewicz, K. Sobiesiak, K. Malinowska, K. Koprowska, M. Czyz, B. Keppler and E. J. M. C. R. Budzisz, 2013, 22, 2395-2402.

6.      A. Özdemir, G. Turan-Zitouni, Z. Asım Kaplancıklı, G. Revial, F. Demirci, G. J. J. o. e. i. İşcan and m. chemistry, 2010, 25, 565-    571.

7.      E. Brantley, S. Antony, G. Kohlhagen, L. Meng, K. Agama, S. F. Stinson, E. A. Sausville, Y. J. C. c. Pommier and pharmacology, 2006, 58, 62-72.

8.      S. Wang, W. Shao, H. Li, C. Liu, K. Wang and J. J. E. j. o. m. c. Zhang, 2011, 46, 1914-1918.

9.      F. Kratz, B. Nuber, J. Weiss and B. J. P. Keppler, 1992, 11, 487-498.

10.    K. Sakai, Y. Tomita, T. Ue, K. Goshima, M. Ohminato, T. Tsubomura, K. Matsumoto, K. Ohmura and K. J. I. C. A. Kawakami, 2000, 297, 64-71.

11.    T.-H. Yang, A. R. Silva and F.-N. J. D. T. Shi, 2013, 42, 13997-14005.

12.    A. Maher F. and M. N. Abid, Malyasian J. Sci. 2019.38(3), 59_71.

13.    W. J. J. C. C. R. Geary, 1971, 7, 81-122.

14.    Ellman GL, Courtney KP, Andres V,Feather Stone RM. Biochem. Pharmacol.1961 ;( 7):88-95.

15.    N. J. I. J. o. B. R. Zaizafoon and Review, 2015, 7, 100-111.

16.    Ž. K. Jaćimović, V. Leovac, K. Mészáros Szécsényi, J. A. Howard and I. J. A. C. S. C. C. S. C. Radosavljević Evans, 2004, 60, m467-m470.

17.    S. C. Davies, M. C. Durrant, D. L. Hughes, A. Pezeshk and R. L. J. J. o. C. R. Richards, 2001, 2001, 100-103.

18.    K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds (Part A: Theory and Applications in  Inorganic Chemistry) (Volume 1A) (Part B: Applications in Coordination, Organometallic, and Bioinorganic Chemistry) (Volume 1B), NY, John Wiley & Sons, Incorporated, 1997.

19.    R. C. Maurya and D. D. J. T. M. C. Mishra, 1987, 12, 551-552.

20.    J. E. Huheey, E. A. Keiter, R. L. Keiter and O. K. Medhi, Inorganic chemistry: principles of structure and reactivity, Pearson Education India, 2006.

21.    Greenwood and A. Earnshaw Butterworth –Heinemann, Chemistry of the elements, Oxford, 1997.

22.    D. Sutton, Electronic spectra of transition metal complexes: an introductory text, McGraw-Hill, 1968.

23.    M. S Katlin, V. M. Leovac, R Petkovic, Z. K. Jacimovic and G. Pokol, Therm. Analys. Calorim.2007,3,899-902

24.    S. Konar, A. Jana, K. Das, S. Ray, S. Chatterjee, J. A. Golen, A. L. Rheingold and S. K. J. P. Kar, 2011, 30, 2801-2808.

25.    B. H. Pearce, H. F. Ogutu and R. C. J. E. J. o. I. C. Luckay, 2017, 2017, 1189-1201.

26.    M. F. J. J. o. O. P. Sugrue and Therapeutics, 1996, 12, 363-376.

27.    S. Sumalan, J. Casanova, G. Alzuet, J. Borras, A. Castineiras and C. J. J. o. i. b. Supuran, 1996, 62, 31-39.

28.    C. T. J. M.-b. d. Supuran, 1995, 2, 327-330.

29.    J. Borràs, T. Cristea and C. T. J. M. G. M. C. Supuran, 1996, 19, 339-346.

30.    G. Mincione, A. Scozzafava and C. T. J. M.-b. d. Supuran, 1997, 4, 27-34.

31.    N. Büyükkidan, B. Büyükkidan, M. Bülbül, R. Kasimoğullari, M. Serdar, S. J. J. o. P. Mert and Pharmacology, 2013, 65, 363-369.

 

 

 

Received on 17.08.2019         Modified on 06.11.2019

Accepted on 19.12.2019         © RJPT All right reserved