Synthesis, Characterization and Antimicrobial Activity of 2-[1-(2,4-Dihydroxyphenyl)Ethylene]Hydrazine Carboxamide and its Zn(II) Metal Complex

The synthesis of 2-[1-(2,4-dihydroxyphenyl)ethylene]hydrazinecarboxamide and its Zn(II) metal complex was achieved. 2, 4 dihydroxy acetophenone is synthesized by resorcinol with glacial acetic acid. This further treated with semicarbazide hydrochloride to form its semicarbazone. Zn(II) metal complex was prepared by dissolving equimolar quantities of metal salt and Schiff base ligand in ethanol. All the target compounds were characterized by M.P, TLC and UV-visible and IR spectral data. Antimicrobial activities of these synthesized compounds were studied in sterile saline by Agar well diffusion method against M. luteus, B. subtilis, S. aureus, E. coli, P. aeruginosa bacteria. All the synthesized compounds have shown good to moderate antimicrobial activity. Introduction Hydroxy acetophenones and its derivatives were used as starting material for the synthesis of chalcones [1], flavones [2] and Schiff bases [3, 4] etc. Hydroxy acetophenone semicarbazone have wide spectrum of biological activities. Schiff bases and their co-ordination compounds have great importance as they are useful in biochemical [5], anticancer [6], anti-inflammatory [7] and antipyretic [8]. A Schiff base of hydroxyl acetophenone and its complexes has variety of applications in biological, clinical, analytical and pharmaceutical area [9, 10]. Metal ions are the factors in the structural organization of biochemical molecules and the functional processes operating in the genetic and metabolic systems [11]. Transition metal ions and their complexes are the essential components found in all living organisms [12]. The interaction of transition metal ions with biologically active ligands is a subject of interest. Studying the biological activities of metal complexes is interesting. Thus the aim of the present work is to synthesize some new hydroxyacetophenones, its derivatives, Zn metal complex and to study their antimicrobial activities [13-18]. Their structures were elucidated on the basis of MP, TLC, elemental analysis, UV-visible and IR spectral data. All the synthesized compounds have been screened for their biological activity by Agar well diffusion method. Materials and Methods The chemicals used in the present work were dry resorcinol, glacial acetic acid, powdered Zinc chloride, semicarbazide hydrochloride, anhydrous sodium acetate, ethanol etc. all these chemicals were purchased from Zen Scientific, Mumbai and were of AR grade. All these chemicals were used for synthesis. Test Microorganism: The microorganism used in the present study were M. luteus, B. subtilis, S. aureus, E. coli, P. aeruginosa.. Microorganisms were maintained at 4C on nutrient agar slants. The reagent 2-[1-(2,4-dihydroxyphenyl)ethylene]hydrazinecarboxamide and its Zn(II) metal complex was prepared as reported in the literature. The structure of the Schiff base is confirmed by using physical methods like melting point, TLC, elemental analysis, UV-visible and IR spectra. The newly synthesized Zn complex was characterized on the basis of microanalysis data, elemental analysis, UV-visible and IR. International Letters of Chemistry, Physics and Astronomy Submitted: 2018-04-12 ISSN: 2299-3843, Vol. 79, pp 9-16 Revised: 2018-06-21 doi:10.18052/www.scipress.com/ILCPA.79.9 Accepted: 2018-08-09 2018 SciPress Ltd., Switzerland Online: 2018-08-29 SciPress applies the CC-BY 4.0 license to works we publish: https://creativecommons.org/licenses/by/4.0/ Synthesis of 2,4-dihydroxyacetophenone Briefly, the synthesis was carried out by dissolving freshly fused and powdered zinc chloride (0.24 mole) in 32 ml of glacial acetic acid by heating on sand bath. Dry resorcinol (0.2 mole) was added with stirring at 140C. The solution was heated until it just begins to boil and kept for 20 minutes at 150C. Dilute HCl (1:1) was added to the mixture and the solution was cooled to 5C. The separated product was filtered and washed with dilute HCl. The product was recrystallized from hot water. The reaction Scheme is given in Fig. 1.


Introduction
Hydroxy acetophenones and its derivatives were used as starting material for the synthesis of chalcones [1], flavones [2] and Schiff bases [3,4] etc. Hydroxy acetophenone semicarbazone have wide spectrum of biological activities. Schiff bases and their co-ordination compounds have great importance as they are useful in biochemical [5], anticancer [6], anti-inflammatory [7] and antipyretic [8]. A Schiff base of hydroxyl acetophenone and its complexes has variety of applications in biological, clinical, analytical and pharmaceutical area [9,10]. Metal ions are the factors in the structural organization of biochemical molecules and the functional processes operating in the genetic and metabolic systems [11]. Transition metal ions and their complexes are the essential components found in all living organisms [12]. The interaction of transition metal ions with biologically active ligands is a subject of interest. Studying the biological activities of metal complexes is interesting. Thus the aim of the present work is to synthesize some new hydroxyacetophenones, its derivatives, Zn metal complex and to study their antimicrobial activities [13][14][15][16][17][18]. Their structures were elucidated on the basis of MP, TLC, elemental analysis, UV-visible and IR spectral data. All the synthesized compounds have been screened for their biological activity by Agar well diffusion method.

Materials and Methods
The chemicals used in the present work were dry resorcinol, glacial acetic acid, powdered Zinc chloride, semicarbazide hydrochloride, anhydrous sodium acetate, ethanol etc. all these chemicals were purchased from Zen Scientific, Mumbai and were of AR grade. All these chemicals were used for synthesis.
Test Microorganism: The microorganism used in the present study were M. luteus, B. subtilis, S. aureus, E. coli, P. aeruginosa.. Microorganisms were maintained at 4 o C on nutrient agar slants.
The reagent 2-[1-(2,4-dihydroxyphenyl)ethylene]hydrazinecarboxamide and its Zn(II) metal complex was prepared as reported in the literature. The structure of the Schiff base is confirmed by using physical methods like melting point, TLC, elemental analysis, UV-visible and IR spectra. The newly synthesized Zn complex was characterized on the basis of microanalysis data, elemental analysis, UV-visible and IR.

Synthesis of 2,4-dihydroxyacetophenone
Briefly, the synthesis was carried out by dissolving freshly fused and powdered zinc chloride (0.24 mole) in 32 ml of glacial acetic acid by heating on sand bath. Dry resorcinol (0.2 mole) was added with stirring at 140 o C. The solution was heated until it just begins to boil and kept for 20 minutes at 150 0 C. Dilute HCl (1:1) was added to the mixture and the solution was cooled to 5 0 C. The separated product was filtered and washed with dilute HCl. The product was recrystallized from hot water. The reaction Scheme is given in Fig. 1  1 gram of powdered semicarbazide hydrochloride was added 0.9 gram of anhydrous sodium acetate to 5ml of water and was warmed gently until a clear solution is appeared. A solution of 1gm of 2, 4 dihydroxyacetophenone in 5ml of ethanol was added. The mixture was warmed gently in a water bath for 15 mins. The semicarbazone rapidly crystallizes. Finally, cool filter off the 2,4 dihydroxyacetophenone Semicarbazone, washed thoroughly with water and was drained. Recrystallised from ethanol. Melting point is 201 o C. The reaction Scheme is given in Fig. 2

Synthesis of Zn(II) Compex:
The ligand (Schiff base) (0.1mm) was taken in hot ethanol (40mL) and treated with a hot ethanolic solution of ZnCl 2 (0.1mm) the light yellow transparent solution of ligand changed to colourless after mixing the solution. This reaction mixture was refluxed for 8 hrs and mixture of solution was cooled, left to stand overnight, filtered by under suction. Crystalline solid was separated out and recrystallized from ethanol. The yield 70% and melting point 345 0 C. The reaction Scheme is given in Fig. 3.  Preparation of test compounds: The solutions were prepared at a concentration of 1mg/µl for all the compounds.

Preparation of Plates and Microbiological assay:
The antimicrobial evaluation was done by Agar well diffusion method [19,20]  petri dishes and allowed to solidify. After solidification of the media, 0.85 cm ditch was made in the plates using a sterile cork borer and these were completely filled with the test solution. The plates were incubated for 36 hrs. at 37 o C. The mean value obtained for the three wells was used to calculate the zone of growth inhibition of each sample. The inhibition zone formed by these compounds against the particular test bacterial strain determined the antibacterial activities of these synthesized compounds.

Results
2,4-dihydroxyacetophenone, its semicarbazone derivative and its Zn(II) metal complex are synthesized. The synthesized compounds were purified by recrystallization method. The purity of the compounds was checked by TLC using appropriate solvent systems. The physical and analytical parameters were checked. (Table1) The structure of all the synthesized compounds was confirmed by UV-visible and IR spectroscopic technique.

Antimicrobial Activity
Microbial assay was carried out by agar well diffusion method. The bacterial strains were activated by inoculating loop full of strain in 20 cm3 of nutrient agar and the same was incubated for 36 hrs. in an incubator at 37 o C. The zone of inhibition in different bacterial strains i.e. M. luteus, B. subtilis, S. aureus, E. coli, P. aeruginosa against synthesized compounds shown in Table 3. Among the various bacterial strains maximum zone of inhibition was recorded in S. aureus and minimum zone of inhibition was observed in M. luteus and P. aeruginosa.