Synthesis Characterization and Biological Application of 2,3,4-Trimethoxy Benzaldehyde Semicarbazone Co(II) Metal Ions

Co(L4)2Cl2] were prepared by reacting 2,3,4-trimethoxy benzaldehyde semi carbazone ligands with CoCl2.6H2O. The IR, UV, Mass and 1H NMR spectra of the complexes have been assigned. Thermo gravimetric analysis were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding ligands. Complexes were screened for antimicrobial activities by the disc diffusion technique using DMSO as solvent. The activity data show that the semi carbazone metal complexes are more potent antimicrobials metal complexes. *Corresponding author: Vidhya RS, Faculty at ST Hindu College, Nagercoil, Tamil Nadu, India, Tel: +914652225940; E-mail: vvidhya276@gmail.com Received November 13, 2017; Accepted November 20, 2017; Published November 23, 2017 Citation: Vidhya RS, Rathika Nath G (2017) Synthesis Characterization and Biological Application of 2,3,4-Trimethoxy Benzaldehyde Semicarbazone Co(II) Metal Ions. Chem Sci J 8: 176. doi: 10.4172/2150-3494.1000176 Copyright: © 2017 Vidhya RS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Introduction
Stereochemistry of coordination compounds plays a major role in their activities. The existence of electronegative nitrogen, oxygen or sulfur atoms on the ligand structure is seen to improve the coordination potential of ligands. The expansion of instrumental techniques provides way of investigating thermal, spectral and magnetic properties of metal complexes. Metal complex preparation from Schiff base ligands [1] which is a large area studied both in solution as well as in the solid state, have attained significant consequence due to their obvious biological activity. The effects of azomethine ylide with alkenes have been investigated from a speculative point of view in order to recognize the reaction path, selectivity on the effect [2]. Typically, semicarbazone derivatives are prepared through the reaction of aldehydes or ketones [3] with semicarbazide in presence of an acid or a base, as catalyst. A variety of semicarbazone [4] derivatives could be prepared in quantitative yields, by mixing stoichiometric amounts of suitable aldehydes with respective semicarbazides. Ketones usually need elevated temperatures than aldehydes for whole conversion. Schiff base ligands for the preparation of metal complexes of semi carbazones have been receiving considerable attention, largely because of their peculiar properties. Schiff bases play a vital role in inorganic chemistry as they easily form stable complexes with most transition metal ions in the periodic table [5][6][7].

Materials and Methods
All chemicals used were of analytical reagent grade (AR) and procured from Sigma-Aldrich and Flock and the metal salts were purchased from E. Merck and used as received.

Synthesis of ligand
0.01 mole of the corresponding aldehyde in ethanol (2,3,4-trimethoxy benzaldehyde) in cold ethanol was added to a 250 ml RB flask containing 0.01 mole of semicarbazide in hot water. The mixture was refluxed for about 4 to 5 hours at 80°C, with continuous stirring, and then allowed to cool overnight at room temperature. The isolated yellow colored precipitate was filtered, washed with cold ethanol and dried under vacuum ( Figure 1).

Synthesis of metal complexes
Aqueous solution of the corresponding metal salt (0.01 mole), (Cobalt Chloride hexahydrate) was individually mixed with hot ethanolic solution of the corresponding ligand (0.02 mole). The mixture was refluxed for 4-5 hours at 70-80°C with continuous stirring, allowed to cool overnight at room temperature to yield brown colored metal complexes. The products were filtered, washed with 50% ethanol, and dried under vacuum ( Figure 2).

Physical parameters of ligand and their metal complexes
Schiff bases were prepared in 1:1 ratio and the Schiff base metal complexes prepared by 1:2 ratio. All the metal complexes were found to be soluble in DMSO. Physical parameters of the resulting complexes are summarized below Table 1.

Elemental analysis
Elemental analysis of ligand L 4 (C 11

Spectral and thermal characterization data
IR spectral analysis L 4 and its metal complexes: The IR spectra of L 4 and its metal complexes are provided below (Figures 3 and 4). IR absorption band in the region 1707.00 cm -1 can be attributed to the C=O stretching vibration of L 4 , while its transition metal show absorption shifted to values 1706.93 cm -1 , in CoCl 2 respectively. 1593.20 cm -1 in the spectrum assigned to the azomethine (C=N) vibration. This is seen to suffer lower shift to values around 1591.27 cm -1 in the complexes of CoCl 2 (Table 3). In the case of metal complexes, the appearance of bands (M-N) in the region of 520.78 cm -1 in CoCl 2 and (M-O) show an absorption band at 420.48 cm -1 in CoCl 2 .

UV spectral analysis
The bands in the range 200-700 nm can be assigned to π-π* and/ or n-π* transitions. Absorption bands at around 250 nm was assigned to 3T1 g(P) ← 3A2 g(F) transition, in the electronic spectra of the 2,3,4-trimethoxy benzaldehyde semicarbazone Co(II) complex in DMSO ( Figure 5). 1 H NMR Spectra of L 4 : The 1H NMR spectrum of L 4 in DMSO is shown in Figure 5 and peak assignments are given in the Table 4. Chemical Shifts of methoxy protons were observed as a single peak at δ 3.923 (ppm). Chemical shift of aromatic proton was observed as a multiple at δ 7.375 ppm ( Figure 6). The azomethine proton appeared at δ 6.526 (ppm). The signals of the N-NH proton were observed as singlet at δ 8.401 (ppm) and -NH 2 proton signals observed as singlet at δ 7.617 (ppm) ( Table 4).

C NMR Spectra of L 4 :
The 13 C NMR spectrum of 2,3,4-trimethoxy benzaldehyde semicarbazone compounds (L 4 ) in DMSO is shown in Figure 6 and peak assignment are given in Table 5. The spectrum showed a signal at 82.850-83.824 ppm which was assigned to methoxy carbon. The presence of carbonyl (ketone group) was found at around           (Figure 7). The azomethine carbon atom exhibited a peak at 162.530 ppm. The peak observed at 45.050-43.483 ppm may be due to methylene carbon (benzyl group) ( Table 5).

Mass spectral analysis
The Electron impact mass spectrum of the ligand (L 4 ), Figure 7 shows a molecular ion (M + ) peak at m/z=253.29 amu corresponding to species C 11 H 15 N 3 O 4 (Figure 8).
The intensities of the peaks give the idea of the strength of the fragments (Figure 9). The mass spectrum of the Co (II) complex showed a molecular ion peak at m/z=565.51 which was found to coincide with that of the molecular weight of the complex (Table 6).

TG analysis
Thermogram of the solid ligand shows that there is no weight loss up to 310°C (Figures 9 and 10). The horizontal portion of the curve indicate there is no change in weight (0-200°C and 310-360°C) and the vertical potion indicate that there is weight change (200-310°C).
Thermogram of the solid complexes shows that there is no weight loss up to 340°C signifying the lack of lattice as well as coordinated water molecule in complexes (Figures 10 and 11).
Thermogram indicates incomplete decay of ligand moiety. The    Table 7 and a graphical representation of the same is presented in Figures 12 and 13.  Table 6: Molecular weights of L 4 and its metal complexes (by Rast's method).

Magnetic moment
The magnetic moment of the complexes was determined using Guoy balance. Magnetic moment values for Cobalt complexes were found to be around 4.10 BM.
Proposed structure of metal complexes: From the above characterization details, the following structures are proposed for the complexes (Figure 12).

Anti-bacterial activity
The antibacterial activities of ligand and its metal complexes were

Anti-oxidant activity
The antioxidant assay study was carried out using different concentrations of the Schiff base and Co(II), metal complexes.

Catalase assay
The antioxidant activity using catalase assay were tested using ligand L 4 and its metal complexes. They were found to have different    OD values at different time intervals (30 sec, 60 secs and 90 sec). The antioxidant activities of Schiff base (L 4 ) and their Co(II) metal complexes were assessed in Tables 9 and 10 ( Figure 15).
Catalase activity of Schiff base metal complexes was found significantly higher than that of free ligands (L 4 ), indicating that this complex is a much better catalase and antioxidant than the ligands. Antioxidant ability of Schiff base increased significantly after chelation of transition metal ions. The Co(II) complexes possess higher antioxidant potential than ligand.

Peroxides assay
In the present work the antioxidant activity using peroxides assay were also tested using the ligands (L 4 ), and their metal complexes. They were found to have different OD values at different time intervals (30 sec, 60 secs, 90 secs, and 120 sec). The activity of Schiff bases and the metal complexes were presented in Table 10 ( Figure 16).

Results and Discussion
In the present work, semicarbazone [8] derivatives of isomeric trimethoxy benzaldehydes were synthesized. complexes of them with metal Co(II) [9] were also synthesized. Characterization was done by the aid of IR, UV, Magnetic moment studies, Mass, and NMR studies. Structures of the complexes were proposed using available resources. Cobalt complexes were assigned tetrahedral geometries [10,11]. The thermal stability of the complexes was checked using thermo-gravimetric technique. The ligands and their metal complexes were analyzed for their biological activity against various bacteria and fungi. The Co(II) complex was found to exhibit good antibacterial and antifungal activity than 2,3,4-trimethoxybenzaldehyde semicarbazone.     Thus, is a good candidate for use in further clinical trials. The compounds were also checked for antioxidant activity and Co(II) metal complexes were found to have better activity compared to ligand. The subtle changes in biological activities may be due to the fact that in most biological activity mechanism, a lock and key mode is seen.

Conclusions
The mode of anti-bacterial and anti-fungicidal action may involve the formation of hydrogen bond through the azomethine nitrogen atom with the active Centre's of the cell constituents, resulting in the interference with the normal cell process.