Antioxidant, Antimicrobial Study of Synthesized and Characterized metal Complexes of Mn(II),Fe(III),Co(II) and XRD, Thermal Study

 

Shyam R. Annapure¹*, Rahul A. Waghmare¹, Shantilal D. Rathod¹, Narayan P. Adlinge²

¹P.G. Department of Chemistry, Milind College of Science, Aurangabad -431002Maharashtra,India.

²Department of Chemistry, Vidnyan Mahavidyalaya, Sangola, Solapur-413307 Maharashtra, India.

*Corresponding Author E-mail: srannapure@gmail.com

Solid asymmetrical complexes ofMn(II),Fe(III), and Co(II)of Schiff bases are synthesized from 3, 4-diamino toluene,3-Acetyl-6-methyl-pyran-2,4-dione (DHA)and5-bromo Salicylaldehyde. The structures of ligands and complexes were characterized by thermal analysis, X-ray diffraction,¹H-NMR, mass, IR,UV-visible spectra, elemental analysis, magnetic susceptibility, and conductometry. Thermal study carried out to calculate kinetic parameter through TGA/DSC. The ligand field parameters have been characterized for Mn(II), Fe(III), Co(II)complexes, which recommend high spineoctahedral geometry. The x-ray diffraction data proposes monoclinic crystal system for all three complexes. Antioxidant property is investigated by DPPH, among three, Fe (III) complex is found more potent. The ligand and their metal complexes were subjected for fungicidal activity against Trichoderma and Aspergillus niger and antibacterial activity against Escherichia coli and Staphylococcus aureus.

 

 

 

INTRODUCTION:

Transition metal complexes play a key role in important chemical processes. Hemoglobin the Oxygen carrier of blood is aniron complex of a protein. Hemocyanin, which transports oxygen in invertebrate animal blood, is a copper chelate. Vitamin B₁₂ is cobalt chelate. The importance and role of coordination compounds in living system is well established. So, chemists infatuated to use it as anti-bacterial, antitumor, anti-oxidant, oxidative cleavage, DNA-cleavage.^1-5DHA appeared as striking ligand to synthesize tetradentate Schiff bases. In continuation of our earlier work ⁶. In present study we synthesized solid complexes of various color, of Mn (II), Fe (III), and Co (II) with tetradentate ligands formed by the reaction of DHA, 3, 4-diamino toluene, and 5-bromo Salicylaldehyde [Fig.1(a)],and characterized by different spectral methods, evaluated for antioxidant and microbial activity.

 

 

 

MATERIAL AND METHOD:

Reagents and solvents used as it is obtained from Merck. DHA, 3, 4-diamino toluene, and 5-bromo Salicylaldehyde of AR grade were used for synthesis of ligand. AR grade metal chlorides were also used for the formation of the complexes. DPPH is purchased from sigma Aldrich.

 

Instrumentation:

The CHN analysis was carried out on Thermo Scientific (FLASH 2000) CHN elemental analyzer. All electronic absorption spectra of the complexes and ligand were chronicled on Shimadzu 1800 spectrometer.¹H-NMR spectra of ligand were recorded on FT NMR spectrometer (400 MH_Z) model Advance-II (Bruuker) in CDCl₃ as a solvent using tetramethylsilane as internal standard. IR study has been carried out on Perkin Elmer-Spectrum RX-I FTIR spectrometer using KBr pellets. The TGA/DSC and XRD were recorded on TA Inc. SDT-2790 and Pananalytical X’Pert Pro respectively at USIC Kolhapur, SAIF Chandigarh.

 

Synthesis of ligand:

It’s a two-stepsynthesis; in the first step mono-Schiff base compound was prepared by refluxing 50 ml solution of (10mmol) of DHA and (10mmol)3, 4-diamino toluene in absolute ethanol for about 4 hr. The progress of reaction was monitored via thin layer chromatography. The resulting mono-Schiff base thus formed was then refluxed with 10mmol of5-bromo Salicylaldehyde to synthesis final product. Product was then cooled at room temperature and collected by filtration, followed by recrystallization in super dry ethanol. (Yield: 87%).

 

Synthesis of metal complexes:

Metal complexes were prepared by mixing a stoichiometric ratio (1:1) by dissolving in methanol. The ligand (0.01 mol) and metal chloride (0.01 mol) are mixed in hot condition with continuous stirring.The mixture was heated at reflux for about 3-4 h. On cooling,the volume of reaction mixture is reduced to half, then colored solid metal complex is appeared. Thus, obtained solid metal complex was purified by petroleum ether and dried over vacuum desiccator (yield: 85%).

 

RESULTS AND DISCUSSION:

CHN analysis, MP, Color, Mol. Wt, and molar conductance data of ligand and metal complexes is portrayed in Table1.The data shows equimolarstoichiometry (metal: ligand) and satisfying general formula [ML(H₂O)₂] [where M=Mn (II), Fe(III) Co(II)].

 

¹H-NMR spectra of ligand:

The ¹H NMR spectra of free ligand in CDCl₃ at room temperature shows the following signals. 2.09 δ (s, 3H, C₆-CH₃), 2.11 δ (s, 3H, N=C-CH₃),2.25 δ (s,3H,C₄-CH₃hydrogen of phenyl ring), 5.77 δ (s, 1H, C₅-H), 6.73-7.03 δ (m, aromatic protons), 8.88 δ (s, 1H, N=C-H), 9.76 (phenolic (-OH) hydrogen of phenyl ring) and 15.88 δ (s, 1H, enolic OH of DHA moiety)⁷.

 

IR spectra:

The IR data of ligand (H₂L) and its metal complexes are recorded in (Table 2).It show prominent bands at 3427, 1693, 1660, 1360 and 1212 cm^-1 assignable to υ OH, υ C=O (lactone carbonyl), υ C=N (azomethine), υ C-N (aryl azomethine) and υ C-O (phenolic) stretching modes respectively.The presence of a strong broad band in the 3427 cm^-1region, in the spectra of the ligand, which is not observed in complexes interprets coordination of phenolic oxygen to the metal ion by deprotonation. Chelation by nitrogen of azomethine (C=N) is confirmed by observing band at 1660 cm^-1in the spectra of ligand, which treasure at lower frequency 1634-1636 cm^-1whencomplex formed.This change can be supported by transfer of electrons from nitrogen to the vacant d-orbitals of the metal.Finding new bands in the 565-680 and 439-637cm^-1 regions confirms the M-O and M-N bonding respectively. No any change in skeletal vibrations (C=C) upon complexation. The presence of coordinated water is established by the appearance of strong band in the 3288-3318 cm^-1 region in case of Mn(II), Fe(III) and Co(II),which is also supported by advent of non-ligand band in 825-846 cm^-1 region, quoted for rocking mode of water ⁸.

 

Magnetic susceptibility and electronic absorption spectra:

The electronic absorption spectrum of Mn (II) complex contains three bands at 671,401,382 nm assignable to the transitions 6A1g → 4T1g, 6A1g → 4T2g and charge transfer respectively. Magnetic moment value 5.76 BM matches with standard value (5.92 BM) corresponds octahedral geometry for Mn (II) complex. The electronic absorption spectra of Fe(III) complex show three strong bands at 782,533,328 nm, which may be assigned to the transitions 6A1g → 4T1g(4D), 6A1g → 4T1g and charge transfer respectively.

 

Electronic transitions together with magnetic moment value 5.79 BM indicates high spin octahedral geometry for Fe (III) complex. Co(II) complex show three bands at 993, 522, 366 nm which may be attributed to the transitions 4T1g → T2g(F), 4T1g → 4A2g(F) and charge transfer respectively. Electronic transitions along with magnetic moment value 4.79 B.M. suggest high spin octahedral geometry for Co(II) complex⁹.The octahedral geometry is further reinforced by ratio υ₂/ υ₁ = 1.750 which is close to the value expected for octahedral geometry.

 

Table-1 Physical characterization, analytical and molar conductance data of compounds

Compound Molecular formula	Mol.Wt.	M.P/DecompTemp. 0C	Color	Molar conductance Mhocm2 mol-1	Found (calculated)
					C	H	N	M
(H2L)C22H19N2O4Br	454.30	173	Dark Yellow	----	58.10 (58.04)	4.25 (4.21)	6.13 (6.15)	-----
[LMn(H2O)2]	510.24	268	Faint Brown	19.54	51.72 (51.79)	2.75 (2.80)	5.36 (5.49)	10.68 (10.77)
[LFe(H2O)2]	511.15	290	Reddish Brown	43.53	51.63 (51.69)	2.85 (2.90)	5.45 (5.48)	10.89 (10.93)
[LCO(H2O)2]	514.23	232	Faint Red	19.21	51.33 (51.38)	3.70 (3.72)	5.42 (5.45)	11.44 (11.46)

 

 

Table-2 IR data of ligand and metal complexes

 

 

 

Powder x-ray diffraction:

Scanning of x-ray diffractogram of Mn(II), Fe(III),Co(II) metal complexes of L is done at wavelength 1.543 Å in the range 5-100°.The x-ray diffraction pattern of these complexes compared with major peaks of relative intensity greater than 10% has been indexed to their hkl value by using computer program. The diffractogram of Mn(II) complex of L had ten reflections with maxima at 2θ = 9.425° corresponding to d value 11.89874Å.The unit cell of Mn(II) complex of L yielded values of lattice constants, a=15.79586 Å, b= 6.122250 Å, c = 14.87546 Å β=97.49° and unit cell volume V=895.56423 ų. The diffractogram of Fe (III) complex of L shows fourteen reflections with maxima at 2θ= 26.098° corresponding to d value 3.41254 Å. The unit cell of Fe (II) complex of L yielded values of lattice constants, a=17.06095 Å, b=7.407466 Å, c = 6.644435 Å, β=121.91°and unit cell volume V=712.24 ų.The diffractogram of CO (II) complex of L had twelve reflections with maxima at 2θ = 6.854° corresponding to d value 15.88564 Å. The unit cell parameters of Co (II) complex of L yielded values of lattice constants, a=16.90569Å, b=8.24567 Å, c = 9.456982 Å β=124.23° and unit cell volume V=789.65234 ų.In respect of these cell parameters, the condition such as a ≠ b ≠ c and α = γ = 90° ≠ β required for sample to be monoclinic were tested and found to be satisfactory. Hence it can be concluded that Mn (II), Fe (III), Co (II), complex of L has monoclinic crystal system.

 

Thermal analysis:

The TG/DSCanalysis of all Mn(II), Fe (III), and Co(II)complexes was done from ambient temperature to 1000°C in nitrogen atmosphere using α-Al₂O₃ as reference.

 

The thermal profile of Mn (II) complex shows mass loss 6.5% (calcd.6.3%) in the range 170-240°C and an endothermic peak in this region ∆Tmin = 225°C indicates loss of two coordinated water molecules. The anhydrous complex first show slow decomposition from 240-660°C with mass 28.65% (calcd.29.64%) loss and a broad exotherm ∆Tmax = 435°C in DSC may be attributed to removal of non-coordinated part of ligand. The second step decomposition is sharp from 660 to 760°C with mass loss of 15.50% (calcd. 15.56%) a sharp endotherm in DTA at 745°C is observed for this step. The third step decomposition is from 760 to 940°C with 15% mass loss.The mass of the final residue 5.2% does not corresponds to any stoichiometry of end product. The TG curve of Fe(II) complex show first mass loss 8.931% (calcd.8.23%) in the range 200-270°C and an endothermic peak in this region ∆Tmin. = 217.13°C, indicate removal of two coordinated water molecules. The second step slow decomposition from 270-650 °C with 32.66% mass loss.This can be further confirmed by observing broad exotherm in DSCwith ∆Tmax. = 360.27°C indicates removal of non-coordinated part. In third step from 650-900 °C sudden weight loss 19.38 %, confirmed by endotherm ∆Tmin. = 667.97°C indicate loss of coordinated part.Thethermogram of Co(II) complex show continuous stepwise mass loss.First 8.214% (calcd.8.8%) in the range 160-260°C and an endothermic peak in this region ∆Tmin. = 240°C, indicates loss of two coordinated water molecules. The anhydrous complex first show stepwise decomposition in 260-440°C range with 13% mass loss (calcd.13.24%) and a broad endotherm ∆Tmin. = 425°c in DSC may be attributed to removal of non-coordinated part of ligand. Thesecond step decomposition at 440-800°C, with mass loss of 19.30% (calcd.19.89%) corresponds to decomposition of coordinated part of ligand. A broad endotherm at ∆Tmin. = 750°c DSC is observed for this step.

 

Kinetic calculations:

The kinetic and thermodynamic parameters viz ∆G (free energy change), ∆S (entropy of activation, z (pre-exponential factor),E_a(energy of activation) and n (order of reaction), together with correlation coefficient (r) for non-isothermal decomposition of metal complexes have been determined by Horowitz-Metzer (HM) approximation method and Coats-Redfern integral method¹⁰. The data is arranged in (Table 3). The results show that the values obtained by two methods are analogous.

 

 

 

Table-3.The kinetic parameter of metal complexes calculated by the methods Horowitz-Metzger (HM) and Coats-Redfern (CR)

Ea in kJ mol^-1, Z in S^-1, ΔS in JK^-1mol^-1and ΔG in kJ mol^-1

 

 

 

Antioxidant Activity:

25,50,100,200μg /ml concentration of ligand, three complexes and ascorbic acid (standard) were prepared in methanol. 2 ml of 1, 1-Diphenyl-2-picrylhydrazyl solution (0.002%) was mixed with 2ml of all compounds separately in clean test tubes. After incubation for 30 min. in dark at room temperature optical density was measured at 517 nm using Shimadzu 1800 spectrometer. The scavenging activity was calculated by formula:

 

Scavenging Activity (%) = [(A_DPPH – A _Sample)/ A_DPPH] ×100

 

Where A_DPPH – Absorbance of DPPH with ascorbic acid, A_Sample - Absorbance of DPPH with sample solution.

 

As DPPH is a good scavenger free radical, reduction capacity of all samples is estimated by degree of decolourisation, to convert it into1,1-Diphenyl-2-picrylhydrazine¹¹. L-Fe complex is found to be more potent along with other complexes. (Table 4)

 

 

 

 

Antimicrobial activity:

Ligand and metal complexes are subjected for antifungal activity; by using Mycelia dry weight method compounds were tested against Trichoderma and Aspergillus niger. The activity is tested at 250 and 500 ppm in DMF and depicted in (Table-5) by comparison with standard. Compounds were tested for antimicrobial activity against bacteria such as Escherichia coli and Staphylococcus aureus by paper disc plate method¹².The compounds were tested at the concentration 500ppm and 1000ppm in DMF, considering Ciprofloxacin as standard (Table-6).Perceiving the values of Table-5 and 6,inference made that the inhibition by metal complexes is more than a ligand.

 

Table 5 Yield of Mycelial dry weight in mg (% inhibition)

 

Table 6 Antibacterial activity of compounds

 

Figure 1 (a)proposed structure of the complexes. Where M=Mn(II),Fe(III),CO(II).

 

CONCLUSION:

In present research we report synthesis of a ligand and its transition metal complexes. Spectral study suggests that azomethine nitrogen and phenolic oxygen are involved in the co-ordination with metal ions (fig.1 (a)). Proposing octahedral geometry for Mn(II), Fe(III) and Co(II), complexes. It is concluded that the ligand is dibasic in nature and N₂O₂tetradentate metal complexes are antioxidant, among three metal, Fe(III) complex is found good hydrogen donor.  Biological activity shows enhanced antimicrobial activities compared to its free ligand. The XRD reveals monoclinic crystal system for Mn(II), Fe (III), and Co(II)complexes. Thermal study predicts thermal behavior of complexes.

 

ACKNOWLEDGEMENTS:

The Authors are thankful to SAIF Punjab University, Chandigarh for providing CHN, IR,¹ HNMR, Mass and XRD facility. Also grateful to USIC, Shivaji University, Kolhapur for providing TGA-DSC facility.

 

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

 

REFERENCES:

1.     Wenling Qin, Sha Long, et al, Schiff Bases: A Short Survey on an Evergreen Chemistry Tool, Molecules, 2013;18, 12264-12289.

2.     Reda F. M. Elshaarawy, et al, Pharmacological performance of novel poly-(ionic liquid)-graftedchitosan-N-salicylideneand their complexes, Carbohydrate Polymers, 2016; 146,376-387.

3.     Qi-Meige Hasi, et al, Synthesis, characterization, antioxidant and antimicrobial activities of a bidentate schiff base ligand and its metal complexes,Polyhedron,2016;109,75-85

4.     Saikat Sarkar, Kamalendu Dey, Synthesis and spectroscopic Characterization of some transition metal complexes of a new hexadentate N₂S₂O₂ Schiff base ligand, Spectrochimica Acta Part A,2005; 62,383-393.

5.     R. Pal, V. Kumar, et al, Synthesis, Characterization, and DNA cleavage study of Dehydroacetic acid based tridentate Schiff base and its metal complexes of first transition series. Med Chem Res, 2014;23,4060-4069.

6.     Shyam R Annapure, Achut S Munde and Shantilal D Rathod, Spectral, thermal, X-ray and antimicrobial studies of newer tetra dentate N₂O₂ Schiff Base complexes of first transition series,Der Chemica Sinica,2016;7(4),47-54.

7.     A.S. Munde, et al, Synthesis and Characterization of some transition metal complexes of unsymmetrical tetra dentate Schiff Base ligand, Journal of the Korean Chemical Society; 2009, 53(4) 407-414.

8.     Shyam R Annapure, Shantilal D Rathod, Synthesis and Characterization of Dehydroacetic acid based new Mn(II),Fe(III),Co(II),metal complexes of asymmetrical ligand, International Journal of Chem Tech Research,2017;10(3),333-338

9.     Sarika M. Jadhav and et al, Synthesis, Spectral, thermal potentiometric and antimicrobial studies of transition metal complexes of tridentate ligand, Journal of Saudi Chemical Society,2014;18,27-34.

10.   V. M. Naik and et al, Synthesis spectroscopic and thermal studies of bivalent transition metal complexes with the hydrazone derived from 2-benzimidazolyl mercaptoaceto hydrazide and o-hydroxy aromatic aldehyde, Indian Journal of Chemistry,2008;47, A,1793-1797.

11.   NoureddineCharef et al, Synthesis, Characterization, X-ray structures’, and biological activity of some metal complexes of the Schiff Base 2,2’-(((azaanediylbis(propane-3,1-diyl))bis(azaneylylidene))bis(methanylylidene)) diphenol, Polyhedron, 2015;85,450-456.

12.   Cruickshank R, Duguid J P, Marion B P, Swain R H A, Twelfthed. Medicinal Microbiology, vol. II Churchill Livingstone, London, 1975, 196-202.

 

 

 

 

Received on 23.05.2017         Modified on 18.06.2017

Accepted on 20.07.2017         © AJRC All right reserved