Abstract
Objective: The study was focused on the synthesis and spectroscopic studies of metal acetylacetonates and their complexes using bidentate Schiff-base ligands (NO), evaluation of their in-vitro antibacterial potentials against pathogenic microorganism.Methods: Acetylacetonate salts of Cobalt(II), Manganese(II) and Magnesium(II) were prepared by reacting their metal hydroxides with acetylacetone. The metal complexes of N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-nitrobenzohydrazide (HL1), N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-methoxybenzohydrazide (HL2) obtained from the condensation reaction of 4-(diethylamino)-2-hydroxybenzaldehyde and 4-nitrobenzohydrazide/ or 4-methoxybenzohydrazide. The synthesized compounds were characterized by fourier transform infrared spectroscopy (FT-IR), proton and carbon-13 nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA). The compounds were screened for their antimicrobial properties against a list of Gram-positive bacterial strains.Results: The FT-IR spectra revealed that the Schiff bases acts as bidentate chelating ligand via nitrogen of the azomethine and phenolic oxygen atoms. NMR reveal the presence of azomethine (HC=N) and aromatic hydrogens at expected chemical shifts confirming the formation of the Schiff base ligands. Thermal decomposition behaviour was studied by thermogravimetry revealing stability up to 260 °C. The compounds were evaluated for their antibacterial potentials against Staphylococcus aureus and Enterococcus faecalis. The manganese acetylacetonato(N'-{(E)-[4-(diethylamino)-2-hydroxyphenyl]methylidene}-4-methoxybenzohydrazide: Mn(acac)(L2) exhibited antimicrobial activities against both Enterococcus faecalis and Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 398.0 μg/mL.Conclusion: The prepared compounds showed no inhibition against the selected pathogenic microorganisms except for Mn(acac)(L2) Standard antibacterial compounds: ampicillin and ciprofloxacin were used as positive control. The antibacterial activity of the compound depends on the kind of substituent on the benzo hydrazide rings at the para position, thereby suggesting the compound as promising chemotherapeutic agents for further structural optimization.
Highlights
Infectious diseases which are directly related to bacteria exhibiting multiple resistance to antibiotics have increased the world’s mortality rate, resulting in about 17 million deaths globally per year in children and the elderly [1]
We describe the synthesis of two hydrazides Schiff base ligands: 4-(diethylamino)-2-hydroxybenzaldehyde with 4-nitrobenzohydrazide or 4-methoxybenzohydrazide and their Mn2, Co(acetylacetonate)2, Mg(acetylacetonate)2 complexes by reflux methods as chemotherapeutic agents with interesting biological properties such as antimicrobial activity
The Schiff base metal complexes synthesized via metal acetylacetonates with the Schiff base ligands reaction were characterized
Summary
Infectious diseases which are directly related to bacteria exhibiting multiple resistance to antibiotics have increased the world’s mortality rate, resulting in about 17 million deaths globally per year in children and the elderly [1]. Schiff base ligands bearing azomethine (>C=N–) functional group, possessing N, O, and S-donor atoms have been established as versatile pharmacophores for design and development of various biologically active compounds [3]. They are used in wide variety of applications such as anti-cancer, anti-corrosion, anti-HIV, anti-radical, anti-bacterial and anti-fungal material and DNA cleavage [2, 4]. Hydrazide derivatives have been reported to possess a broad spectrum of antibacterial activities They act as a good potential for oral drugs used for the treatment of genetic disorders like thalassemia [7,8]
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