Abstract A pyrimidine-based ligand, 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione (L), has been sy... more Abstract A pyrimidine-based ligand, 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione (L), has been synthesized by the reaction of 2-aminopyrimidine with 2-hydroxy-1,4-napthoquinone. Reaction of the ligand with Ni(II), Co(II), Mn(II) and Zn(II) acetate gave the corresponding metal complexes which were characterized by spectroscopic techniques, (infrared, electronic), elemental analysis, room-temperature magnetometry, conductance measurements and thermogravimetry-differential scanning calorimetry (TG-DSC) analyses. The room-temperature magnetic data and electronic spectral measurements of the complexes gave evidence of 4-coordinate square planar/tetrahedral geometry. The thermal analyses values obtained indicated the monohydrate complexes. The antimicrobial screening of the compounds showed mild to very good results. The Mn(II) complex showed the best result within in the range of 11.5–29 mm. The electronic, structural and spectroscopic properties of the complexes were further discussed using density functional theory. Molecular docking studies showed significant binding affinity with the drug targets and the metal complexes have potentials to be used as drugs.
Abstract Organotin(IV) complexes represented as R2SnL2 (where R = Cl, CH3, C4H9, C6H5; L = N,N-di... more Abstract Organotin(IV) complexes represented as R2SnL2 (where R = Cl, CH3, C4H9, C6H5; L = N,N-diallyldithiocarbamate) have been synthesized and characterized by elemental analysis, 1H, 13C, 119Sn NMR and FTIR spectroscopic analyses. The structures of [(CH3)2SnL2] and [(C4H9)2SnL2] were further determined using single crystal X-ray crystallography. These complexes crystallized in a triclinic crystal system with P-1(2) space group. Two N,N-diallyldithiocarbamato ligands bond to the tin(IV) ion in an anisobidentate fashion resulting in a highly distorted six coordinate geometry, best described as skew trapezoidal-bipyramidal geometry. Results obtained for the antimicrobial study showed a varied activity against some Gram (+) and (−) bacterial and fungi species. This activity generally ranged from moderate to good in which complex [(C6H5)2SnL2] and [(C4H9)2SnL2] exhibited the best antimicrobial properties. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability and reducing power studies showed that complex [(CH3)SnL2] displayed the highest antioxidant activities compared to the other compounds but a little less than the standard, gallic acid. Furthermore, the cytotoxicity study against the human tumour cell line (HeLa) showed a varied activity due to lipophilicity and selectivity of the cell line towards the complexes. This observed activity compared favourably with the standard drug (5-FU) used in which complex [(C6H5)2SnL2] was found to show a better cytotoxic activity than the standard drug.
In the present paper, the inhibition effect of some Schiff base compounds on the corrosion of alu... more In the present paper, the inhibition effect of some Schiff base compounds on the corrosion of aluminum in a composite phase change materials of Na2HPO412H2O - Na2SO410H2O has been studied by Potentiodynamic polarization and Electrochemical impedance spectroscopy measurements. The Schiff base compounds are, (E)-3-(1-(2-(benzo[d]thiazol-2-yl) hydrazono)ethyl)-2, 6-dimethyl-2H-pyran-4-ol, (E)-N'-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)benzohydrazide, (E)-3-hydroxy-N'-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)-2-naphthohydrazide, and (E)-N'-(1-(4-hydroxy-2, 6-dimethyl-2H-pyran-3-yl)ethylidene) furan-2-carboximidhydrazide, which is represented as T33, T45, T46 and T49. This kind of compounds possess a common backbone of (E)-3-(1-hydrazonoethyl) -4-hydroxy-6-methyl-2H-pyran-2-one. The results showed that all the Schiff base compounds were able to inhibit the corrosion of Aluminum in composite phase change material Na2HPO412H2O - Na2SO410H2O. The inhibition efficiency followed the order T46 > T49 > T45 > T33 at the maximum inhibitor concentration of 0.009 M. The strongest inhibition effect of T46 is ascribed to its structure, which contains a hydroxyl group (-OH) in addition to the strong polarization property of the (E)-3-(1-hydrazonoethyl)-4-hydroxy-6-methyl-2H-pyran-2-one backbone.
Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)<sub>2</sub>] (<b>1</b&g... more Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)<sub>2</sub>] (<b>1</b>), [Ni(buphdtc)(PPh<sub>3</sub>)(NCS)] (<b>2</b>) and [Ni(buphdtc)(PPh<sub>3</sub>)(NC)] (<b>3</b>) (where bu = butyl and ph = phenyl), were synthesized and characterized by elemental analysis, UVvis, and FTIR spectroscopies. Complexes <b>1</b> and <b>2</b> were further characterized by single-crystal X-ray structural analysis. The single-crystal X-ray structural analysis indicates a slightly distorted square planar geometry. In <b>2</b> and <b>3</b>, the influences of the auxiliary ligands (PPh<sub>3</sub>, NCS, and NC) on their steric and electronic properties were observed. Thermal studies of the complexes showed decomposition starting at 250–300 °C, leading to formation of nickel sulfide phases around 400 °C. The complexes were screened against some bacteria strains, <i>Staphylococcus aureus</i>, <i>S</i><i>treptococcus pneumoniae</i>, <i>Bacillus subtilis</i>, <i>Escherichia coli</i>, <i>K</i><i>lebsiella oxytoca</i> and <i>P</i><i>seudomonas aeruginosa</i>, and two fungi species, <i>A</i><i>spergillus niger</i> and <i>F</i><i>usarium oxysporum</i>. The complexes showed moderate-to-strong antimicrobial potentials, with [Ni(buphdtc)<sub>2</sub>] (<b>1</b>) displaying the best antimicrobial activity. Fluconazole and streptomycin were used as reference drugs for antifungal and antibacterial assays, respectively.
Abstract Organotin(IV) dithiocarbamate complexes have shown a large spectrum of biological activi... more Abstract Organotin(IV) dithiocarbamate complexes have shown a large spectrum of biological activities, which includes antioxidants, anti-inflammatory, antimicrobial, antituberculosis, anticancer and antiviral. In this report, organotin(IV) dithiocarbamate complexes derived from N-methyl-N-phenyldithiocarbamate (L) and organotin have been synthesized. The complexes which were represented as C4H9(Cl)SnL2 (1), C6H5(Cl)SnL2 (2), (CH3)2SnL2 (3), (C4H9)2SnL2 (4) and (C6H5)2SnL2 (5), were characterized by spectroscopic techniques (FTIR, 1H, 13C and 119Sn NMR), elemental and thermal analyses (TGA and DTG). The structures of complexes (3) and (4) were further established by X-ray single crystal diffraction. The structures, in both complexes, gave a distorted octahedral geometry around the tin center. This is due to the longer bond length of one of the Sn S bonds within the complexes compared to others, and also the electronic and steric demands caused by the alkyl substituents on the tin atom. The complexes exhibited varied antimicrobial activity against S. Aureus, B. cerues, K. pneumonia, P. aeruginosa, E. coli, C. albican and A. flavus. Complex 5 displayed the best antimicrobial activities compared to the other organotin complexes, and this could be attributed to the planar phenyl group attached to the tin center causing an increase in the lipophilicity of the complex through the lipid bilayer of the bacteria organisms.
The work reported the synthesis and characterisation of Fe2+, Co2+, and Ni2+ complexes of 2-(4,6-... more The work reported the synthesis and characterisation of Fe2+, Co2+, and Ni2+ complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione (HL). The spectroscopic and elemental analysis results obtained were consistent with the adoption of the formulas, [ML2] (M = Fe and Co) and [ML2(H2O)] (M = Ni) for the metal complexes. Electronic spectra and magnetic moments of the metal complexes corroborated octahedral geometry for Ni(II) complex and tetrahedral geometry for Fe(II) and Co(II) complexes. However, quantum-chemical calculations using density functional theory predicted trigonal bipyramidal geometry for Ni(II) complex and provided corroborative explanations for the structures of the other complexes. Conductance measurements in dimethylsulfoxide indicate that the complexes are non-electrolytes. The antimicrobial potential of the compounds was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus, Proteus mirabilis, Klebsiella oxytoca, Aspergillus niger, A. flavus, and Rhizopus stolonifer. The compounds gave moderate to good antimicrobial activity. However, the bacterial and fungal organisms were more susceptible to the cobalt complex and ligand respectively than the other compounds at concentration of 10 mg/mL. The compounds were also assessed for their antioxidant potential using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The compounds displayed good DPPH radical scavenging activities. The nickel complex exhibited the best DPPH radical scavenging activity compared to the other compounds.
The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanopar... more The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanoparticles (AgNPs) is presented. The plant extract was obtained by boiling dried leaves and using the obtained filtrate for the synthesis of AgNPs. The study was conducted to investigate an ecofriendly approach to metal nanoparticle synthesis and to evaluate the antimicrobial potential of both the aqueous plant extract and resulting silver nanoparticles against different microbes using the disc diffusion method. The synthesis of silver nanoparticles was monitored using ultraviolet–visible (UV–v is) spectroscopy, which showed a localized surface plasmon resonance band at 411 nm and a shift of the band to higher wavenumber of 422 nm after 90 min of reaction. Powder X-ray diffraction analysis and transmission electron microscopy of the obtained AgNPs revealed their crystalline nature, with average size of 12.6 nm. Presence of elemental silver was further confirmed by energy-dispersive X-ray spectroscopy. Fourier-transform infrared spectroscopy confirmed presence of phytochemicals from Lavandula × intermedia leaf extract on the AgNPs. The AgNPs showed good antimicrobial activity with inhibition zone ranging from 10 to 23 mm; the largest inhibition zone (23 mm) occurred against Escherichia coli. Generally, the AgNPs displayed more antimicrobial activity against all investigated pathogens compared with Lavandula × intermedia leaf extract, and were also more active than streptomycin against Klebsiella oxytoca and E. coli at the same concentration. The silver nanoparticles showed prominent antimicrobial activity with a lowest minimum inhibitory concentration (MIC) value of 15 μg/mL against E. coli, K. oxytoca, and Candida albicans.
Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (H... more Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL1) and 2‐[(5‐methyl‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL2), and their Pd(II), Ni(II) and Co(II) complexes were prepared and characterized using 1H NMR, 13C NMR, infrared and UV–visible spectroscopic techniques, elemental analysis, magnetic susceptibility, thermogravimetry and molar conductance measurements. The infrared spectral data showed that the chelation behaviours of the ligands towards the transition metal ions were through one of the carbonyl oxygen and deprotonated nitrogen atom of the secondary amine group. Molar conductance results confirmed that the complexes are non‐electrolytes in dimethylsulfoxide. The geometries of the complexes were deduced from magnetic susceptibility and UV–visible spectroscopic results. Second‐order perturbation analysis using density functional theory calculation revealed a stronger intermolecular charge transfer between ligand and metal ion in [NiL1(H2O)2(CH3COO‐)] and CoL1 compared to the other complexes. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities. [NiL1(H2O)2(CH3COO‐)] exhibited the best antibacterial results with a minimum inhibitory concentration of 50 μg mL−1. The molecular interactions of the compounds with various drug targets of some bacterial organisms were established in a bid to predict the possible mode of antibacterial action of the compounds. The ferrous ion chelating ability of the ligands indicated that HL1 is a better Fe2+ ion chelator, with an IC50 of 29.79 μg mL−1, compared to HL2 which had an IC50 of 98.26 μg mL−1.
Abstract In this study, adducts of Zn(II) dithiocarbamates containing different N-donor ligands (... more Abstract In this study, adducts of Zn(II) dithiocarbamates containing different N-donor ligands (pyridine, 2,2′-bipyridine and 1,10-phenanthroline) have been synthesized. The parent dithiocarbamate complex comprise N-methyl-N-phenyl dithiocarbamate (L1) and N-ethyl-N-phenyl dithiocarbamate (L2), and the adducts are represented as [ZnL1L2py], [ZnL1L2bpy], and [ZnL1L2phen] (where py = pyridine, bpy = 2,2′-bipyridine, and phen = 1,10-phenanthroline). All the compounds have been characterized by elemental analysis and spectroscopic techniques (IR and NMR). In addition, the crystal structure of [ZnL1L2bpy] complex is also reported. The structure indicates that the two dithiocarbamate ligands are disordered in 0.67:0.33 ratio and alternatively bond as monodentate and bidentate ligands. The bipyridine acts as a bidentate ligand, and gives the structure around the Zn atom a distorted square pyramidal geometry. In order to evaluate their antimicrobial properties, the precursor complex and the adducts were screened against six pathogenic bacteria strains and two fungi organisms. The antimicrobial activities of the complexes were in the order [ZnL1L2] > [ZnL1L2py] > [ZnL1L2bpy] > [ZnL1L2phen]. The precursor complex, ZnL1L2, showed the lowest MIC and is considered as the complex with most antimicrobial activity against the selected microorganisms.
Abstract The use of plants in nanosynthesis has potentiated the application of most greeneries in... more Abstract The use of plants in nanosynthesis has potentiated the application of most greeneries in this field of study. The aqueous extract of Umbrella plant and different concentrations (1 mM, 2 mM and 5 mM) of AgNO3 were utilized in the preparation of silver nanoparticles (AgNPs). Two volume ratios, 1:5 and 1:10, of the substrate to the precursor were used, and the rate of formation of the AgNPs was monitored using UV-vis spectroscopy. The nanoparticles were characterized using infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and powder X-ray diffraction (pXRD) techniques. The particle sizes of the nanoparticles were below 20 nm, with the 1:10 ratio of all the concentrations giving the lowest size. The photocatalytic abilities of the AgNPs in the degradation of methyl red were studied. The antimicrobial properties of the nanoparticles against common microbes such as Staphylococcus auerus, Bacillus cereus, Klebsiella pneumoniae and Escherichia coli showed interesting results.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Benzothiazole moiety has gained a lot of attention because of its importance as essential pharmac... more Benzothiazole moiety has gained a lot of attention because of its importance as essential pharmacophore in the development of metal based drugs. Nickel(II) and copper(II) complexes of a benzothiazole based ligand, 2,2’‐bibenzo[d]thiazole (L1), synthesized by the reaction of benzothiazole‐2‐carbonylchloride and o‐aminothiophenol, is reported. The compounds were characterised by elemental and percentage metal analyses, spectroscopic (FTIR and UV–vis), 1H and 13C NMR, Mass spectra, thermal, magnetic moment and molar conductance analyses. The mass spectra, elemental and percentage metal composition of the metal complexes gave a 2:1 ligand to metal stoichiometric mole ratio. The spectral data showed that the ligand was coordinated to the metal ions through the nitrogen atoms of the benzothiazole moiety. The electronic spectra and magnetic susceptibility measurements showed that the nickel and copper complexes adopted square planar geometries. The ligand and its metal(II) complexes were s...
A simple and cost-effective material composed of polyacrylonitrile nanofibers containing differen... more A simple and cost-effective material composed of polyacrylonitrile nanofibers containing different concentrations of moringa (MR) leaf extracts was fabricated for antimicrobial properties and wound dressing. The fabricated materials were characterized by scanning electron microscopy, thermal gravimetric analysis, and Fourier transmission infrared spectroscopy. The antibacterial sensitivity of the developed polyacrylonitrile-moringa extract nanofibers was evaluated against and by the agar diffusion method. A pronounced antibacterial activity was observed with the increase in the incorporated moringa leaf extract concentration within the polyacrylonitrile-moringa extract nanofibers against the bacterial strains. The best antibacterial sensitivity was observed for nanofibers containing 0.5 g of moringa leaf extract which had an inhibitory zone of 15 mm for and 12 mm for . Furthermore, the cost-effective and biodegradable nanofibrous polyacrylonitrile-moringa extract nanofiber was also ...
Abstract A pyrimidine-based ligand, 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione (L), has been sy... more Abstract A pyrimidine-based ligand, 2-(pyrimidin-2-ylamino)naphthalene-1,4-dione (L), has been synthesized by the reaction of 2-aminopyrimidine with 2-hydroxy-1,4-napthoquinone. Reaction of the ligand with Ni(II), Co(II), Mn(II) and Zn(II) acetate gave the corresponding metal complexes which were characterized by spectroscopic techniques, (infrared, electronic), elemental analysis, room-temperature magnetometry, conductance measurements and thermogravimetry-differential scanning calorimetry (TG-DSC) analyses. The room-temperature magnetic data and electronic spectral measurements of the complexes gave evidence of 4-coordinate square planar/tetrahedral geometry. The thermal analyses values obtained indicated the monohydrate complexes. The antimicrobial screening of the compounds showed mild to very good results. The Mn(II) complex showed the best result within in the range of 11.5–29 mm. The electronic, structural and spectroscopic properties of the complexes were further discussed using density functional theory. Molecular docking studies showed significant binding affinity with the drug targets and the metal complexes have potentials to be used as drugs.
Abstract Organotin(IV) complexes represented as R2SnL2 (where R = Cl, CH3, C4H9, C6H5; L = N,N-di... more Abstract Organotin(IV) complexes represented as R2SnL2 (where R = Cl, CH3, C4H9, C6H5; L = N,N-diallyldithiocarbamate) have been synthesized and characterized by elemental analysis, 1H, 13C, 119Sn NMR and FTIR spectroscopic analyses. The structures of [(CH3)2SnL2] and [(C4H9)2SnL2] were further determined using single crystal X-ray crystallography. These complexes crystallized in a triclinic crystal system with P-1(2) space group. Two N,N-diallyldithiocarbamato ligands bond to the tin(IV) ion in an anisobidentate fashion resulting in a highly distorted six coordinate geometry, best described as skew trapezoidal-bipyramidal geometry. Results obtained for the antimicrobial study showed a varied activity against some Gram (+) and (−) bacterial and fungi species. This activity generally ranged from moderate to good in which complex [(C6H5)2SnL2] and [(C4H9)2SnL2] exhibited the best antimicrobial properties. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability and reducing power studies showed that complex [(CH3)SnL2] displayed the highest antioxidant activities compared to the other compounds but a little less than the standard, gallic acid. Furthermore, the cytotoxicity study against the human tumour cell line (HeLa) showed a varied activity due to lipophilicity and selectivity of the cell line towards the complexes. This observed activity compared favourably with the standard drug (5-FU) used in which complex [(C6H5)2SnL2] was found to show a better cytotoxic activity than the standard drug.
In the present paper, the inhibition effect of some Schiff base compounds on the corrosion of alu... more In the present paper, the inhibition effect of some Schiff base compounds on the corrosion of aluminum in a composite phase change materials of Na2HPO412H2O - Na2SO410H2O has been studied by Potentiodynamic polarization and Electrochemical impedance spectroscopy measurements. The Schiff base compounds are, (E)-3-(1-(2-(benzo[d]thiazol-2-yl) hydrazono)ethyl)-2, 6-dimethyl-2H-pyran-4-ol, (E)-N'-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)benzohydrazide, (E)-3-hydroxy-N'-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)-2-naphthohydrazide, and (E)-N'-(1-(4-hydroxy-2, 6-dimethyl-2H-pyran-3-yl)ethylidene) furan-2-carboximidhydrazide, which is represented as T33, T45, T46 and T49. This kind of compounds possess a common backbone of (E)-3-(1-hydrazonoethyl) -4-hydroxy-6-methyl-2H-pyran-2-one. The results showed that all the Schiff base compounds were able to inhibit the corrosion of Aluminum in composite phase change material Na2HPO412H2O - Na2SO410H2O. The inhibition efficiency followed the order T46 > T49 > T45 > T33 at the maximum inhibitor concentration of 0.009 M. The strongest inhibition effect of T46 is ascribed to its structure, which contains a hydroxyl group (-OH) in addition to the strong polarization property of the (E)-3-(1-hydrazonoethyl)-4-hydroxy-6-methyl-2H-pyran-2-one backbone.
Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)<sub>2</sub>] (<b>1</b&g... more Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)<sub>2</sub>] (<b>1</b>), [Ni(buphdtc)(PPh<sub>3</sub>)(NCS)] (<b>2</b>) and [Ni(buphdtc)(PPh<sub>3</sub>)(NC)] (<b>3</b>) (where bu = butyl and ph = phenyl), were synthesized and characterized by elemental analysis, UVvis, and FTIR spectroscopies. Complexes <b>1</b> and <b>2</b> were further characterized by single-crystal X-ray structural analysis. The single-crystal X-ray structural analysis indicates a slightly distorted square planar geometry. In <b>2</b> and <b>3</b>, the influences of the auxiliary ligands (PPh<sub>3</sub>, NCS, and NC) on their steric and electronic properties were observed. Thermal studies of the complexes showed decomposition starting at 250–300 °C, leading to formation of nickel sulfide phases around 400 °C. The complexes were screened against some bacteria strains, <i>Staphylococcus aureus</i>, <i>S</i><i>treptococcus pneumoniae</i>, <i>Bacillus subtilis</i>, <i>Escherichia coli</i>, <i>K</i><i>lebsiella oxytoca</i> and <i>P</i><i>seudomonas aeruginosa</i>, and two fungi species, <i>A</i><i>spergillus niger</i> and <i>F</i><i>usarium oxysporum</i>. The complexes showed moderate-to-strong antimicrobial potentials, with [Ni(buphdtc)<sub>2</sub>] (<b>1</b>) displaying the best antimicrobial activity. Fluconazole and streptomycin were used as reference drugs for antifungal and antibacterial assays, respectively.
Abstract Organotin(IV) dithiocarbamate complexes have shown a large spectrum of biological activi... more Abstract Organotin(IV) dithiocarbamate complexes have shown a large spectrum of biological activities, which includes antioxidants, anti-inflammatory, antimicrobial, antituberculosis, anticancer and antiviral. In this report, organotin(IV) dithiocarbamate complexes derived from N-methyl-N-phenyldithiocarbamate (L) and organotin have been synthesized. The complexes which were represented as C4H9(Cl)SnL2 (1), C6H5(Cl)SnL2 (2), (CH3)2SnL2 (3), (C4H9)2SnL2 (4) and (C6H5)2SnL2 (5), were characterized by spectroscopic techniques (FTIR, 1H, 13C and 119Sn NMR), elemental and thermal analyses (TGA and DTG). The structures of complexes (3) and (4) were further established by X-ray single crystal diffraction. The structures, in both complexes, gave a distorted octahedral geometry around the tin center. This is due to the longer bond length of one of the Sn S bonds within the complexes compared to others, and also the electronic and steric demands caused by the alkyl substituents on the tin atom. The complexes exhibited varied antimicrobial activity against S. Aureus, B. cerues, K. pneumonia, P. aeruginosa, E. coli, C. albican and A. flavus. Complex 5 displayed the best antimicrobial activities compared to the other organotin complexes, and this could be attributed to the planar phenyl group attached to the tin center causing an increase in the lipophilicity of the complex through the lipid bilayer of the bacteria organisms.
The work reported the synthesis and characterisation of Fe2+, Co2+, and Ni2+ complexes of 2-(4,6-... more The work reported the synthesis and characterisation of Fe2+, Co2+, and Ni2+ complexes of 2-(4,6-dihydroxypyrimidin-2-ylamino)naphthalene-1,4-dione (HL). The spectroscopic and elemental analysis results obtained were consistent with the adoption of the formulas, [ML2] (M = Fe and Co) and [ML2(H2O)] (M = Ni) for the metal complexes. Electronic spectra and magnetic moments of the metal complexes corroborated octahedral geometry for Ni(II) complex and tetrahedral geometry for Fe(II) and Co(II) complexes. However, quantum-chemical calculations using density functional theory predicted trigonal bipyramidal geometry for Ni(II) complex and provided corroborative explanations for the structures of the other complexes. Conductance measurements in dimethylsulfoxide indicate that the complexes are non-electrolytes. The antimicrobial potential of the compounds was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus, Proteus mirabilis, Klebsiella oxytoca, Aspergillus niger, A. flavus, and Rhizopus stolonifer. The compounds gave moderate to good antimicrobial activity. However, the bacterial and fungal organisms were more susceptible to the cobalt complex and ligand respectively than the other compounds at concentration of 10 mg/mL. The compounds were also assessed for their antioxidant potential using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The compounds displayed good DPPH radical scavenging activities. The nickel complex exhibited the best DPPH radical scavenging activity compared to the other compounds.
The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanopar... more The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanoparticles (AgNPs) is presented. The plant extract was obtained by boiling dried leaves and using the obtained filtrate for the synthesis of AgNPs. The study was conducted to investigate an ecofriendly approach to metal nanoparticle synthesis and to evaluate the antimicrobial potential of both the aqueous plant extract and resulting silver nanoparticles against different microbes using the disc diffusion method. The synthesis of silver nanoparticles was monitored using ultraviolet–visible (UV–v is) spectroscopy, which showed a localized surface plasmon resonance band at 411 nm and a shift of the band to higher wavenumber of 422 nm after 90 min of reaction. Powder X-ray diffraction analysis and transmission electron microscopy of the obtained AgNPs revealed their crystalline nature, with average size of 12.6 nm. Presence of elemental silver was further confirmed by energy-dispersive X-ray spectroscopy. Fourier-transform infrared spectroscopy confirmed presence of phytochemicals from Lavandula × intermedia leaf extract on the AgNPs. The AgNPs showed good antimicrobial activity with inhibition zone ranging from 10 to 23 mm; the largest inhibition zone (23 mm) occurred against Escherichia coli. Generally, the AgNPs displayed more antimicrobial activity against all investigated pathogens compared with Lavandula × intermedia leaf extract, and were also more active than streptomycin against Klebsiella oxytoca and E. coli at the same concentration. The silver nanoparticles showed prominent antimicrobial activity with a lowest minimum inhibitory concentration (MIC) value of 15 μg/mL against E. coli, K. oxytoca, and Candida albicans.
Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (H... more Two novel heterocyclic ligands, 2‐[(5‐fluoro‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL1) and 2‐[(5‐methyl‐1,3‐benzothiazol‐2‐yl)amino]naphthalene‐1,4‐dione (HL2), and their Pd(II), Ni(II) and Co(II) complexes were prepared and characterized using 1H NMR, 13C NMR, infrared and UV–visible spectroscopic techniques, elemental analysis, magnetic susceptibility, thermogravimetry and molar conductance measurements. The infrared spectral data showed that the chelation behaviours of the ligands towards the transition metal ions were through one of the carbonyl oxygen and deprotonated nitrogen atom of the secondary amine group. Molar conductance results confirmed that the complexes are non‐electrolytes in dimethylsulfoxide. The geometries of the complexes were deduced from magnetic susceptibility and UV–visible spectroscopic results. Second‐order perturbation analysis using density functional theory calculation revealed a stronger intermolecular charge transfer between ligand and metal ion in [NiL1(H2O)2(CH3COO‐)] and CoL1 compared to the other complexes. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities. [NiL1(H2O)2(CH3COO‐)] exhibited the best antibacterial results with a minimum inhibitory concentration of 50 μg mL−1. The molecular interactions of the compounds with various drug targets of some bacterial organisms were established in a bid to predict the possible mode of antibacterial action of the compounds. The ferrous ion chelating ability of the ligands indicated that HL1 is a better Fe2+ ion chelator, with an IC50 of 29.79 μg mL−1, compared to HL2 which had an IC50 of 98.26 μg mL−1.
Abstract In this study, adducts of Zn(II) dithiocarbamates containing different N-donor ligands (... more Abstract In this study, adducts of Zn(II) dithiocarbamates containing different N-donor ligands (pyridine, 2,2′-bipyridine and 1,10-phenanthroline) have been synthesized. The parent dithiocarbamate complex comprise N-methyl-N-phenyl dithiocarbamate (L1) and N-ethyl-N-phenyl dithiocarbamate (L2), and the adducts are represented as [ZnL1L2py], [ZnL1L2bpy], and [ZnL1L2phen] (where py = pyridine, bpy = 2,2′-bipyridine, and phen = 1,10-phenanthroline). All the compounds have been characterized by elemental analysis and spectroscopic techniques (IR and NMR). In addition, the crystal structure of [ZnL1L2bpy] complex is also reported. The structure indicates that the two dithiocarbamate ligands are disordered in 0.67:0.33 ratio and alternatively bond as monodentate and bidentate ligands. The bipyridine acts as a bidentate ligand, and gives the structure around the Zn atom a distorted square pyramidal geometry. In order to evaluate their antimicrobial properties, the precursor complex and the adducts were screened against six pathogenic bacteria strains and two fungi organisms. The antimicrobial activities of the complexes were in the order [ZnL1L2] > [ZnL1L2py] > [ZnL1L2bpy] > [ZnL1L2phen]. The precursor complex, ZnL1L2, showed the lowest MIC and is considered as the complex with most antimicrobial activity against the selected microorganisms.
Abstract The use of plants in nanosynthesis has potentiated the application of most greeneries in... more Abstract The use of plants in nanosynthesis has potentiated the application of most greeneries in this field of study. The aqueous extract of Umbrella plant and different concentrations (1 mM, 2 mM and 5 mM) of AgNO3 were utilized in the preparation of silver nanoparticles (AgNPs). Two volume ratios, 1:5 and 1:10, of the substrate to the precursor were used, and the rate of formation of the AgNPs was monitored using UV-vis spectroscopy. The nanoparticles were characterized using infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and powder X-ray diffraction (pXRD) techniques. The particle sizes of the nanoparticles were below 20 nm, with the 1:10 ratio of all the concentrations giving the lowest size. The photocatalytic abilities of the AgNPs in the degradation of methyl red were studied. The antimicrobial properties of the nanoparticles against common microbes such as Staphylococcus auerus, Bacillus cereus, Klebsiella pneumoniae and Escherichia coli showed interesting results.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Benzothiazole moiety has gained a lot of attention because of its importance as essential pharmac... more Benzothiazole moiety has gained a lot of attention because of its importance as essential pharmacophore in the development of metal based drugs. Nickel(II) and copper(II) complexes of a benzothiazole based ligand, 2,2’‐bibenzo[d]thiazole (L1), synthesized by the reaction of benzothiazole‐2‐carbonylchloride and o‐aminothiophenol, is reported. The compounds were characterised by elemental and percentage metal analyses, spectroscopic (FTIR and UV–vis), 1H and 13C NMR, Mass spectra, thermal, magnetic moment and molar conductance analyses. The mass spectra, elemental and percentage metal composition of the metal complexes gave a 2:1 ligand to metal stoichiometric mole ratio. The spectral data showed that the ligand was coordinated to the metal ions through the nitrogen atoms of the benzothiazole moiety. The electronic spectra and magnetic susceptibility measurements showed that the nickel and copper complexes adopted square planar geometries. The ligand and its metal(II) complexes were s...
A simple and cost-effective material composed of polyacrylonitrile nanofibers containing differen... more A simple and cost-effective material composed of polyacrylonitrile nanofibers containing different concentrations of moringa (MR) leaf extracts was fabricated for antimicrobial properties and wound dressing. The fabricated materials were characterized by scanning electron microscopy, thermal gravimetric analysis, and Fourier transmission infrared spectroscopy. The antibacterial sensitivity of the developed polyacrylonitrile-moringa extract nanofibers was evaluated against and by the agar diffusion method. A pronounced antibacterial activity was observed with the increase in the incorporated moringa leaf extract concentration within the polyacrylonitrile-moringa extract nanofibers against the bacterial strains. The best antibacterial sensitivity was observed for nanofibers containing 0.5 g of moringa leaf extract which had an inhibitory zone of 15 mm for and 12 mm for . Furthermore, the cost-effective and biodegradable nanofibrous polyacrylonitrile-moringa extract nanofiber was also ...
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Papers by Damian C Onwudiwe