Chemistry

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Browsing Chemistry by Subject "antibacterial activity"

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    Synthesis, characterization and antibacterial activity Of selected schiff base ligands and their copper Complexes
    (Chuka University, 2025) Tonui , Fredrich Kibet
    Resistant strains of bacteria have emerged because of improper use of antibiotics and insufficient infection management, posing a serious danger to both public health and the global economy. Therefore, it has become essential to produce a new generation of antimicrobials to slow the spread of antibiotic resistance. This is by advancement of antimicrobial drugs that can specifically interact with a target site of a particular pathogen. The work described in this paper entails the synthesis, characterization and antibacterial evaluation of schiff base ligands and their Cu (II) complexes. The ligands, Ligand 1 ((E)-N,N-dimethyl1-4-((p-tolyimino)methyl)aniline) and Ligand 2 ((E)4(((2,4-dinitrophenyl)imino)methyl)-n-n-dimethylaniline), were obtained by microwave assisted condensation and then refluxed for 3 hours, the solid was filtered and rinsed with ethanol and left to dry. The copper complexes were prepared by treating a hot (40°C) solution of the ligands dissolved in ethanol with an aqueous solution of Cu (II) chloride followed by refluxing for 3 hours. Ultraviolet Visible spectroscopy and Fourier Transform Infrared Spectroscopy characterized each of the synthesized compounds. The percentage yield was at 78% for ligand 1, 62% for ligand 2, 76% for complex 1 and 81% for complex 2. The UV-Visible spectra showed two major absorption bands for the ligands, which shifted to higher and lower wavelengths for the complexes. The FTIR spectra show that the azomethine (-C=N-) stretch shifts from 1640.0 cm ¹ in the ligands to 1635.64 cm ¹ in complex 1 and 1614.42 cm ¹ in complex 2. Similarly, the carbonyl (-C-O-) stretch shifts from 1238.00 cm ¹ (Ligand 1) and 1160.00 cm¹ (Ligand 2) to lower values in complex 1 (1027.00 cm¹) and complex 2 (1141.00 cm¹), confirming metal-ligand interaction. The antibacterial sensitivity levels of the synthesized Schiff bases and the Cu (II) complexes was evaluated using disk diffusion method. The bacterial strains employed included; GramPositive staphylococcus aureus and Gram-negative Escherichia coli. The filter paper discs were deepen into concentration ranging from 10ug/ml-40ug/ml for every compound synthesized and then laid onto the surface of the discs. The average inhibition zone for the ligands was at 7.0 mm (ligand 1) and 6 mm (ligand 2) for gram negative bacteria and 10.5 mm (ligand 1) and 10.75 (ligand 2) for Gram positive bacteria. For the complexes 6.0 mm (complex 1) and 6.75 mm (complex 2) for gram negative bacteria and 9.5mm (Complex 1) and 8.75 mm (complex 2) for gram positive bacteria relative to standard gentamycin which showed activity at 24 mm for gram negative and 26 mm for gram positive bacteria. These results were relative to the literature work done, however the zones were slightly lower. From these results, it is concluded that the ligands and complexes were successfully synthesized and all these compounds showed promising activity against bacteria. To explore further potential of these compounds, further studies on other antimicrobial properties as antiviral, antifungal among others should be performed to evaluate similar performance.
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    Synthesis, characterization and antibacterial activity of Ruthenium (II) complexes of Bidentate Schiff base ligands
    (Chuka University, 2024) Nyang’ate Shem Ongechi
    Increased bacterial resistance to available antibiotics remains a concern globally; therefore, there is a need for novel antibiotics with unique mechanisms of action to combat multidrug-resistant organisms. This is important in ensuring that both the human and animal health is well protected. Schiff bases containing pyridine imine pharmacophore possess significant antibacterial activity. The objectives of this study were to; – Prepare ruthenium (II) complexes of bidentate Schiff base ligands – Investigate the complex formed – Perform bioassay of the prepared complexes on some selected bacterial strains. The Schiff base ligands were synthesized by reacting 4-bromoaniline, 4-aminophenol, and aniline with 2-pyridine carboxaldehyde in a 1:1 ratio, while refluxing the mixture for 3-4 hours. To obtain the respective ruthenium (II) metal and ruthenium cymene complexes, hydrated ruthenium (II) chloride and ruthenium p-cymene were combined with the Schiff base ligands in a 2:1 ratio, followed by heating for 3 hours under reflux. The characterization process of the complexes involved proton nuclear magnetic resonance spectroscopy, melting point determination, UV/VIS spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). In the FT-IR spectra, the peaks related to C=N symmetrical vibration appeared in the range of 1600 cm ¹–1620 cm ¹, which shifted as compared to the free pyridine-imine ligands (1632–1625 cm ¹), confirming the intended complex formation. The UV-vis spectra of the ligands exhibited the absorption bands in the ranges of 275-337 nm which correspond to the transition of non-bonding electrons of azomethine nitrogen. After the complexation process, it was observed that the bands corresponding to the n→π* transition for the azomethine present in the bidentate ligand shifted to the lower frequencies indicating the interaction of imine nitrogen atoms with the metal ion. The synthesized ligands and their metal complexes were evaluated for antibacterial activity against two bacterial strains: Staphylococcus aureus which is Gram-positive and Escherichia coli which is Gram-negative, by disc diffusion method with four concentrations. The zones of inhibition were between 8 - 17 millimeters, therefore did not surpass the inhibition zones of gentamicin which was used as the positive control. Statistical analysis using two-way ANOVA highlighted that there was a difference (p ≤ 0.05) in the means of the different values to some extent, suggesting that the hydroxyl and bromo groups, as well as the ability of ligands to coordinate with ruthenium (II), were responsible for mediating antibacterial activities. It was also observed that, Ruthenium (II) complexes were more active against the bacterial strains than the free Schiff base ligands. Also, complexes formed with substituted Schiff base ligands, 4-aminophenol and 4-bromoaniline exhibited higher antibacterial activity compared to complexes formed with unsubstituted Schiff base ligands. Based on these results, it can be suggested that the synthesized compounds possess potential antibacterial activity.
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    Synthesis, characterization and antibacterial Properties of copper (II) complexes of schiff bases derived from benzophenone derivatives and selected anilines
    (Chuka University, 2024) Kosgei Festus Kimutai
    In every region of the world, antibiotic resistance is increasing to dangerously high levels. The emergence and global dissemination of new bacterial resistance threaten human beings' capacity to cure widespread infectious diseases. As antibiotics lose their effectiveness, many infections, including blood poisoning, pneumonia, and tuberculosis, become difficult to cure and occasionally incurable. Therefore, there is a pressing need to develop new antibacterial agents to address this resistance. Thus, this study entailed synthesizing, characterizing, and determining the antibacterial activities of the Schiff base and its copper (II) complexes. The Schiff base ligands were synthesized by mixing 2-hydroxy-4-methoxybenzophenone with selected anilines in a 1:1 ratio, followed by refluxing for 3-4 hours. The precipitate obtained was filtered and dried at room temperature. The Cu (II) complexes were prepared in a 2:1 ratio by treating a hot solution of Schiff base ligands dissolved ethanol with an aqueous Cu (II) chloride under 4 hours of refluxing. The synthesized compounds melted at a constant temperature, confirming that they were pure. The Schiff base ligands and their Cu (II) complexes were characterized using various analytical techniques such as Fourier Transform-Infrared (FT-IR), Ultra Violet-Visible (UV-VIS) and Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy and molar conductance measurements. The FT-IR data of the Schiff base ligands displayed the absence of NH2 and C=O, confirming the formation of azomethine group (-HC=N-) at region 1610-1631.78cm1 which shifted to lower wavelengths upon complexation with Cu (II) ions. The peak due to OH appeared at 3420-3450 cm-1 but later disappeared due to formation Cu (II) complex. The appearance of two new peaks 475.46-480.28 and 523.68581.55cm-1 in the Cu (II) complex spectra attributed to Cu-O and Cu-N, respectively. UV-vis spectra of the free ligands appeared at 40322.58-41580cm-1 due to the transition of non-bonding electrons of azomethine nitrogen. Molar conductance measurements of Cu (II) complexes range from 13.34-22.208(Scm2mol-1), while that of free ligands range from 4.86-12.58 (Scm2mol-1), confirming they were nonionic. 1H NMR analysis of free ligands in deuterated DMSO-d6 revealed the presence of the presence of OH group at δ 11.81-12.65 ppm, which disappear upon complexing with Cu (II) ions. The antibacterial sensitivity levels of the Schiff base ligands and their Cu (II) complexes were determined using the disk diffusion method. The synthesized compounds tested for antibacterial bioassay against two gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli and one gram-positive bacterium, Staphylococcus aureus, at 4 different concentrations. All synthesized compounds show antibacterial activities against all bacteria strains. The zones of inhibition ranged from 6.00- 21.00 mm. However, no test compound showed higher inhibition zones than gentamycin and amoxiclav (positive controls). Data was analyzed using Two-Way ANOVA. The results showed a significant difference (p ≤ 0.05) between the means, indicating that methyl, nitro and carboxyl groups and coordination of the ligands to Cu (II) affected antibacterial activity. Cu (II) complexes displayed higher antibacterial activity than their free ligands. It was concluded that the substituted ligands with methyl, carboxyl and nitro groups and Cu (II) complexes have promising antibacterial activity. The results suggest potential applications of Schiff base ligands obtained from benzophenone derivatives and their Cu (II) complexes as antibacterial agents.