Synthesis, characterization and biological activity of some transition metals with Schiff base derived from 2-thiophene carboxaldehyde and aminobenzoic acid

Metal complexes of Schiff base derived from 2-thiophene carboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The ligand dissociation as well as the metal-ligand stability constants were calculated pH metrically at 25 degrees C and ionic strength mu=0.1 (1M NaCl). The complexes are found to have the formulae [M(HL)2](X)n.yH2O (where M=Fe(III) (X=Cl, n=3, y=3), Co(II) (X=Cl, n=2, y=1.5), Ni(II) (X=Cl, n=2, y=1) and UO2(II) (X=NO3, n=2, y=0)) and [M(L)2] (where M=Cu(II) (X=Cl) and Zn(II) (X=AcO)). The molar conductance data reveal that Fe(III) and Co(II), Ni(II) and UO2(II) chelates are ionic in nature and are of the type 3:1 and 2:1 electrolytes, respectively, while Cu(II) and Zn(II) complexes are non-electrolytes. IR spectra show that HL is coordinated to the metal ions in a terdentate manner with ONS donor sites of the carboxylate O, azomethine N and thiophene S. From the magnetic and solid reflectance spectra, it is found that the geometrical structure of these complexes are octahedral. The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the DrTG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.     

Antimicrobial and anticancer activities of Schiff base ligand and its transition metal mixed ligand complexes with heterocyclic base

A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, ¹H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X‐ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H₂O)]Cl_x?nH₂O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)Cl]?3H₂O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X‐ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram‐positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC₅₀ higher than that of HL, especially the Cu(II) complex which showed the highest IC₅₀ against breast cell line.     

Metal complexes of novel Schiff base derived from the condensation of 2‐quinoline carboxaldehyde and ambroxol drug with some transition metal ions

A new Schiff base was prepared as the condensation product of the reaction of 2‐quinoline carboxaldehyde and ambroxol drug. The Schiff base ligand thus obtained (HL; trans‐4‐[(2‐(2‐quinolinoimino)‐3,5‐dibromobenzyl)amino]cyclohexanol) was further employed as a tridentate ligand for the synthesis of new complexes through reaction with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal ions. The synthesized HL and its metal complexes were characterized using various physicochemical techniques including elemental analysis, Fourier transform infrared and UV–visible spectroscopies, conductimetric and magnetic susceptibility measurements, mass spectrometry and thermal analyses. ¹H NMR data indicated that complex formation was through the amino group rather than the aliphatic hydroxyl group. Thermal analysis gave an idea about the decomposition pattern of HL and its complexes. Also, it revealed the number of water molecules in the inner and outer spheres of the complexes. An octahedral geometry for all the complexes has been suggested. HL and its complexes were screened for their antimicrobial activity against various species of bacteria and fungi using the disc diffusion method. The Cr(III) complex had the highest antimicrobial activity.     

Molecular structure,molecular docking,thermal, spectroscopic and biological activity studies of bis‐Schiff base ligand and its metal complexes

Coordination compounds of Fe(III), Zn(II), Ni(II), Co(II), Cu(II), Cd(II) and Mn(II) ions were synthesized from the ligand [4,4′‐((((ethane‐1,2‐diylbis(oxy))bis(2,1‐phenylene))bis(methanylylidene))bis(azanylylidene))diphenol]ethane (H₂L) derived from the condensation of bisaldehyde and 4‐aminophenol. Microanalysis, magnetic susceptibility, infrared, ¹H NMR and mass spectroscopies, molar conductance, X ray powder diffraction and thermal analysis were used to confirm the structure of the synthesized chelates. According to the data obtained, the composition of the 1:1 metal ion–bis‐Schiff base ligand was found to be [M(H₂L)(H₂O)₂]Cl_n (M = Zn(II), Ni(II), Co(II), Cu(II), Cd(II) and Mn(II), n = 2; Fe(III), n = 3). Magnetic susceptibility measurements and reflectance spectra suggested an octahedral geometry for the complexes. Central metals ions and bis‐Schiff base coordinated together via O2 and N2 donor sites which as evident from infrared spectra. The Gaussian09 program was applied to optimize the structural formula for the investigated Schiff base ligand. The energy gaps and other important theoretical parameters were calculated applying the DFT/B3LYP method. Molecular docking using AutoDock tools was utilized to explain the experimental behaviour of the Schiff base ligand towards proteins of Bacillus subtilis (5 h67), Escherichia coli (3 t88), Proteus vulgaris (5i39) and Staphylococcus aureus (3ty7) microorganisms through theoretical calculations. The docked protein receptors were investigated and the energies of hydrogen bonding were calculated. These complexes were then subjected to in vitro antibacterial studies against several organisms, both Gram negative (P. vulgaris and E. coli) and Gram positive (S. pyogones and B. subtilis). The ligand and metal complexes exhibited good microbial activity against the Gram‐positive and Gram‐negative bacteria.     

Comparative study between two fabricated potentiometric sensors to enhance selectivity towards ferrous ions

Electroanalytical methods are highly selective for measuring electrical quantities including the charge, potential and current with their relation to chemical parameters. They are widely applied in various fields such as biochemical analysis, industrial quality control and environmental monitoring. They have many advantages over other techniques in that they are not time consuming and are specific for certain oxidation states of certain elements which give these techniques high selectivity and sensitivity features. This paper is based on two parts: the first part describes the fabrication of screen‐printed electrodes (SPEs) modified with methyl red as electroactive material, while second part describes the preparation and characterization of Fe(II)–methyl red complex using various spectroscopic tools, the complex being used for the construction of carbon paste electrodes (CPEs). The two proposed electrodes were successfully applied for the determination of Fe(II) in water and pharmaceutical (pharovit) samples. The electrodes under investigation show potentiometric response for Fe(II) in the concentration range 8.0 × 10^?7–1.0 × 10^?2 and 5.0 × 10^?7–1.0 × 10^?2 M at 25°C for SPE and CPE, respectively, and the electrode response is independent of pH in the range 1.5–7.0. These sensors show Nernstian slopes of 29.1 ± 0.2 and 29.7 ± 0.16 mV decade^?1 with detection limit values of 8.0 × 10^?7 and 5.0 × 10^?7 M for SPE and CPE, respectively. These electrodes show fast response time of 6 and 4 s and exhibit a lifetime of 100 and 30 days for SPE and CPE, respectively. The mechanism of chemical reaction between modifier and Fe(II) on the SPE surface was studied using infrared spectra, scanning electron microscopy and energy‐dispersive X‐ray analysis. The proposed potentiometric method was validated according to the IUPAC recommendations. The results obtained using the proposed sensors were comparable with those obtained with inductively coupled plasma analysis.     

Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Coordination compounds of some transition metal ions with new Schiff base ligand derived from dibenzoyl methane. Structural characterization,thermal behavior,molecular structure,antimicrobial, anticancer activity and molecular docking studies

Series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were prepared with tetradentate Schiff base ligand derived by condensation of 2‐aminophenol with dibenzoylmethane. The novel Schiff base H₂L (2–2′‐((1Z,1Z’)‐(1,3‐diphenyl propane‐1,3 diylidene) bis (azanylylidene) diphenol) and its binary metal complexes were characterized by physicochemical procedures i.e. elemental analysis, FT‐IR, UV–Vis, thermal analyses (TGA/DTG), mass spectrometry, magnetic susceptibility and conductometric measurements. On the basis of these studies, an octahedral geometry for all these complexes was proposed expect Ni(II) complex which had tetrahedral geometry. Molar conductivity values revealed that the complexes were electrolytes except Mn(II), Zn(II) and Cd(II) complexes were non electrolytes. The ligand bound to the metal ions via two azomethine N and two phenolic OH as indicated from the IR and ¹H NMR spectral study. The molecular and electronic structures of H₂L and its zinc complex were optimized theoretically and the quantum chemical parameters were calculated. The antimicrobial activity against a number of bacterial organisms as Streptococcus pneumonia, Bacillus Subtilis, Pseudomonas aeruginosa and Escherichia coli and fungi as Aspergillus fumigates, Syncephalastrum racemosum, Geotricum candidum and Candida albicans by disk diffusion method were screened for the Schiff base and its complexes. The Cd(II) complex has potent antimicrobial activity. Anticancer activity of the Schiff base ligand and its metal complexes were evaluated in human cancer (MCF‐7 cells viability). The Cr(III) complex exhibited higher activity than other complexes and ligand. Molecular docking was used to predict the binding between Schiff base ligand (H₂L) and its Zn(II) complex and the receptors of RNA of amikacin antibiotic (4P20) and human‐DNA‐Topo I complex (1SC7). The docking study provided useful structural information for inhibition studies.     

Synthesis,characterization, density functional theory,X‐ray study,thermal stability,and biological and MOE relevance of metal complexes of griseofulvin

Metal(II) and metal(III) coordination compounds of griseofulvin (GFV) drug were synthesized. The structure of the ligand was determined on the basis of elemental analyses, infrared and ¹H NMR spectroscopies and thermal studies. GFV behaved as a neutral tridentate chelating agent and coordinated to metal ions through three oxygen atoms: two methoxy groups and oxygen atom of furan ring. Metal complexes were characterized by means of elemental analyses and molar conductance, spectral (infrared, electron spin resonance) and thermal studies. All the complexes showed molar conductance behaviour corresponding to an electrolytic nature. All the complexes showed octahedral geometry, except [Zn(GFV)Cl]Cl that showed tetrahedral geometry. Density functional theory (DFT) calculations were employed to understand and estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The computed parameters from DFT calculations for structure optimizations and vibrational frequencies were in good agreement with the experimental data. Newly synthesized metal complexes in addition to GFV were examined against opportunistic pathogens. The biological applications of complexes were studied with two Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram‐negative bacteria (Escherichia coli and Neisseria gonorrhoeae) as well as their antifungal activity against Candida albicans. Results suggested that metal complexes were more biologically sensitive than free ligand. The complexes showed a moderate inhibition of MCF7 breast cancer cell line growth. Molecular docking studies further helped in understanding the mode of action of the compounds through their various interactions with the crystal structures of: human serum albumin (PDB: 5FUO), Staphylococcus aureus nucleoside (PDB: 3Q8U), human acetylcholinesterase (PDB: 1B41) and the human DNA–Topo I complex (PDB: 1SC7).     

Synthesis and spectroscopic characterization of indomethacin-Cd(II), Ce(III), and Th(IV) complexes: IR, 1H NMR,thermal, and biological studies

Solid complexes have been prepared and characterized by IR, UV-Vis, elemental analysis, and ¹H NMR. Indomethacin forms complexes with Cd(II), Ce(III), and Th(IV) ions in molar ratios (ligand: metal) (2: 1), (3: 1), and (4: 1), respectively. The IR spectra of the complexes suggest that the Indomethacin behaves as a monobasic monodentate ligand coordinated to the metal ions via the deprotonated carboxylate group. Prepared complexes exhibit higher antimicrobial activity against several microorganisms, compared to free ligand.     

Synthesis, structure investigation, spectral characteristics and biological activities of some novel azodyes

Four novel azo compounds were synthesized; o-phenylazo- (C(14)H(13)N(3)O(2)) (I), p-bromo-o-phenylazo- (C(14)H(13)BrN(3)O(2)) (II), p-methoxy-o-phenaylazo- (C(15)H(16)N(3)O(3)) (III) and p-nitro-o-phenylazo-p-acetamidophenol (C(14)H(13)N(4)O(4)) (IV). These compounds were carefully investigated using elemental analyses, UV-vis, FT-IR, (1)H NMR and mass spectra. Also, the effects of p-substituents such as bromo, methoxy and nitro groups on the mass fragmentation pathways of these dyes were studied using Hammet's effects. This research aimed chiefly to threw lights on the structures-stability relationship of four novel newly prepared azo derivatives of p-acetoamidophenol. The data obtained referred to the variation of mass fragmentation pathways with the variation of p-substituent of these dyes which can be used in industry for various dyeing purposes. This variation is also correlated and verified by molecular orbital calculations which were done on ionic forms of these dyes using semi empirical PM3 program. The biological activities of these dyes were also investigated and its structure relationship was correlated.