Spectroscopic and Biological Studies on Newly Synthesized Cobalt (II) and Nickel (II) Complexes with 2-Acetyl Coumarone Semicarbazone and 2-Acetyl Coumarone Thiosemicarbazone

Co(II) and Ni(II) complexes of general composition ML2X2 (M = Co(II), Ni(II); X = Cl , NO3 ) were synthesized by the condensation of metal salts with semicarbazone/thiosemicarbazone derived from 2-acetyl coumarone. e ligands and metal complexes were characterized by NMR, elemental analysis, molar conductance, magnetic susceptibility measurements, IR, and atomic absorption spectral studies. On the basis of electronic, molar conductance and infrared spectral studies, the complexes were found to have square planar geometry.e Schiff bases and theirmetal complexes were tested for their antibacterial and antioxidant activities.


Introduction
Research on the coordination chemistry, analytical applications, and biological activities of Schiff base complexes has increased steadily for many years.A large number of Schiff bases and their complexes have been studied for their interesting and important biological properties, for example, antimicrobial (El-Wahab et al. [1]), antiviral (Kolocouris et al. [2]), antifungal (Rodríguez-Argüelles et al. [3]), antitumour (Ainscough et al. [4]), and other biological activities (Bharamagouclar et al. [5]; Zhu et al. [6]; Shalin et al. [7]; Kothari and Sharma [8]) particularly with �rst row of transition metal complexes.e formation of variety of metal complexes with Schiff base ligands as mentioned in our earlier studies (Chandra and Kumar [9]; Chandra and Kumar [10]; Chandra and Gupta [11]) indicates the spectacular progress in coordination and bioinorganic chemistry.It has been demonstrated through several studies that the biological activity of Schiff 's bases is enhanced on chelation with a metal ion (Sengupta et al. [12]).In the view of the facts that the metal complexes are better therapeutic agents (Chandra et al. [13]; Kumar and Chandra [14]) as compared to the Schiff bases, the aim of this study is to synthesize the new class of metal complexes with newly synthesized Schiff base ligands and different metal salts, to �nd their biological activity such as antioxidant and antibacterial activities and to observe the impact of complexation on their therapeutic values.

Experimental
All the chemicals used in the present work were of high purity, Anala R grade, and procured from Sigma-Aldrich.Metal salts were purchased from E. Merck and used as received.e solvents used were either spectroscopic pure from SRL/BDH or puri�ed by the recommended methods (Vogel [15]).

Synthesis of 2-Acetyl Coumarone Semicarbazone (SCL).
An aqueous solution of semicarbazide HCl (1.11 g, 0.01 mol) was added to an ethanolic solution of 2-acetyl coumarone (1.60 g, 0.01 mol) in the presence of sodium acetate (0.82 g, 0.01 mol).e reaction mixture was stirred vigorously for 2 h.e completion of the reaction was con�rmed by the �LC.e yellow product formed was collected by �ltration which was washed several times with hot water and dried in vacuum IR spectra (KBr) were recorded on a FTIR spectrum BX-II spectrophotometer.e electronic spectra were recorded in DMSO on a Shimadzu UV mini-1240 spectrophotometer.e 1 H NMR spectrums were recorded on a Jeol FT-NMR Spectrometer using DMSO as a solvent.ermogravimetry (TG) and Differential ermogravimetric (DTA) analysis for the metal complexes were carried out on a Perkin Elmer (Diamond) TG-DTA spectrometer for the determination of complex entrapped water.

Ligands/complexes
Percent of control SCL 98 analyzed by the Elemental Analyzer and are tabulated in Table 1.e molar conductance measurements (Table 1) of the complexes in DMSO correspond to 1 : 2 electrolytic nature (Shakir et al. [16]).On the basis of elemental analysis data and molar conductance of the complexes, the metal complexes may be formulated as [ML 2 ]X 2 (where M = Co(II), Ni(II); X = Cl − , NO 3 − ).

Magnetic Moment and Electronic Spectral Data of Metal
Complexes.At room temperature Ni(II) complexes show diamagnetic character and Co(II) complexes show magnetic moment in the range 1.85-2.04B.M. (Table 2) corresponding to one unpaired electron.ese values correspond to low spin con�gurations of the metal complexes.e electronic spectrum of chloride and nitrate complexes shows electronic spectral bands in the range 17100-17900 cm −1 and 22400-22800 cm −1 corresponding to the following transitions:  1 : 2 B 1g → 2 A 1g ,  2 : 2 B 1g → 2 E g which indicates the square planar geometry of the complexes.
3.9.TG-DTA Data of Metal Complexes.All the metal complexes show major weight loss above 175 ∘ C which shows that they are free of any entrapped water.e peaks due to melting of complexes in TG-DTA curve agree well with the melting point of the complexes as determined by the MP apparatus (Make: BUCHI, Model: M-560).

Antioxidant Activity
4.1.Assay of Initiation of Lipid Peroxidation.e details of the assay procedure are described in the earlier communication (Raj et al. [17]).e reaction mixture in a �nal volume of 2 mL consisted of 0.025 M Tris-HCI (pH 7.5), microsomes (1 mg protein) which were taken from the laboratory of Prof. H. G. Raj, Department of Biochemistry, VP Chest Institute and were prepared by adopting the method of Ernster and Nordenbrand [18] (protein was assayed by the method of Lowry et al. [19]), 3 mM ADP, and 0.15 mM FeCl 3 .e tubes were preincubated for 10 min at 37 ∘ C followed by the addition of the test compounds added at a concentration of 100 M in 0.2 mL of DMSO and then again incubated for 10 min at 37 ∘ C. e reaction was started by the addition of 0.5 mM NADPH for initiation of enzymatic lipid peroxidation and incubated for different intervals.e reaction was terminated by the addition of 0.2 mL of 50% TCA followed by addition of 0.2 mL of 5 N HCI and 1.6 mL of 30% TBA.e tubes were heated in an oil bath at 95 ∘ C for 30 min, cooled, and centrifuged at 3000 rpm.e intensity of the colour of the thiobarbituric acid reactive substance (TBRS) formed was read at 535 nm.e lipid peroxidation was found to be linear up to 15 min under the conditions described here.e results (Table 3) illustrate the in�uence of ligands and metal complexes on the initiation of lipid peroxidation enzymatically.ese results clearly indicate that metal complexes have higher antioxidant activities as compared to the schiff 's base ligands.iosemicarbazone metal complexes show higher antioxidant activities than semicarbazone metal complexes.Moreover, nickel metal complexes show higher antioxidant activities than cobalt metal complexes.

Antibacterial Activity
e antibacterial activities of the metal complexes were determined at different concentrations (30 g/disc) against different pathogenic bacteria (Table 4) by using disc diffusion technique and the results were compared with standard antibiotic, Kanamycin (30 g/disc).It was found that the metal complexes were active against all of the test bacteria but the metal complexes [Co(TSCL) 2 ](NO 3 ) 2 and [Ni(TSCL) 2 ](NO 3 ) 2 were most effective against all pathogenic bacteria as shown in Table 4. e zones of inhibition of the complexes were, however, lesser as compared to standard Kanamycin.e metal complexes have higher antibacterial activities as compared to the Schiff 's base ligands.iosemicarbazone metal complexes show higher activities than semicarbazone metal complexes.

Conclusions
e present work describes the facile synthesis of metal complexes with newly synthesized Schiff base ligands and their biological activity.On the basis of elemental analysis data, molar conductance, magnetic susceptibility measurements, IR, and atomic absorption spectral studies, the resulting metal complexes may have square planar geometry and may be formulated as [ML 2 ]X 2 (where M = Co(II), Ni(II); X = Cl − , NO 3 − ).e metal complexes show higher antioxidant and antibacterial activities as compared to the ligands.e nickel complexes derived from 2-acetyl coumarone thiosemicarbazone show remarkable antioxidant and antibacterial activities.

F 1 :
IR spectra of SCL.
T 1: Molar conductance and elemental analysis data.
, was mixed with hot ethanolic solution of the corresponding ligand (2 mmol), for example, SCL (0.434 g) or TSCL (0.466 g).e mixture was re�uxed for 4-5 hours at 70-80 ∘ C. On cooling the contents, the complex separated out in each case.It was �ltered, washed with 50% ethanol, and dried under vacuum over P 4 O 10 .echaracterizationdetailsaretabulated in Table1.2.4.PhysicalMeasurements.e C, H, and N were analyzed on a Carlo-Erba 1106 elemental analyzer.Metal contents were determined by Atomic Absorption studies.Molar conductance was measured on an ELICO (CM82T) conductivity bridge.Magnetic susceptibilities were measured at room temperature on a Gouy balance using CuSO 4 ⋅5H 2 O as calibrant.