Ahmed M. Mansour

Molecular structures of antitumor active Pd(II) and Pt(II) complexes of N,N-donor benzimidazole methyl ester

[MLCl2] · zH2O · C2H5OH (L = 2-[(1H-benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester; M = Pd, z = 2; M = Pt, z = 0) complexes were synthesized as potential antitumor compounds and their structures were elucidated by elemental analysis and spectroscopic data. Theoretical molecular structures were investigated by the DFT/B3LYP method using the LANL2DZ basis set. The calculated molecular parameters, bond distances, and angles, revealed a square-planar geometry around the metal through pyridine-type nitrogen (Npy) of benzimidazole and the secondary amino group (NHsec). The lone pair interaction LP(2)O48 of ethanol with anti-bonding σ*(C(16)–H(29)) is an evidence for charge transfer from ethanol to platinum. The electronic movement and assignment of electronic spectra were carried out by TD-DFT calculations. The ligand in comparison to its metal complexes was screened for antibacterial activity and cytotoxicity.

Structural and in vitro cytotoxicity studies on 1H-benzimidazol-2-ylmethyl-N-phenyl amine and its Pd(II) and Pt(II) complexes

[MLCl(2)]·zH(2)O (L = (1H-benzimidazol-2-ylmethyl)-N-phenyl amine; M = Pd, z = 0; M = Pt, z = 1) and [PdL(OH(2))(2)]·2X·zH(2)O (X = Br, I, NO(3), z = 0; X = SCN, z = 1) complexes were synthesized as potential anticancer compounds and characterized by elemental analysis, spectral and thermal methods. FT-IR and (1)H NMR studies revealed that the benzimidazole L is coordinated to the metal ions via the pyridine-type nitrogen (N(py)) of the benzimidazole ring and secondary amino group (NH(sec)). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and (1)H NMR of the benzimidazole L and its complexes were carried out by density functional theory using B3LYP functional combined with 6-31G(d) and LANL2DZ basis sets. Natural bond orbitals (NBOs) and frontier molecular orbitals were performed at B3LYP/LANL2DZ level of theory. The synthesized ligand, in comparison to its metal complexes was screened for its antibacterial activity. The benzimidazole L is more toxic against the bacterium Staphylococcus aureus (MIC = 58 μg/mL) than the standard tetracycline (MIC = 82 μg/mL). The complexes showed cytotoxicity against breast cancer, Colon Carcinoma, and human heptacellular Carcinoma cells. The platinum complex (6) displays cytotoxicity (IC(50) = 12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.

Novel Ni(II) and Zn(II) complexes coordinated by 2-arylaminomethyl-1H-benzimidazole: molecular structures, spectral, DFT studies and evaluation of biological activity.

[NiL(1,2)Cl(2)(OH(2))(3)]·zH(2)O and [ZnL(1,2)(CH(3)CO(2))(2)] (L(1)=(1H-benzimidazol-2-ylmethyl)-N-phenyl amine, z=0 and L(2)=2-[(1H-Benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester, z=1) complexes have been synthesized and characterized by a variety of physico-chemical techniques. The central Ni(II) ion is coordinated by only the pyridine-type nitrogen (N(py)) of benzimidazole ring, three water molecules and two chlorido ligands forming a distorted octahedral geometry. Five coordinated zinc complexes were obtained, where the coordination sphere of zinc ion is made up of secondary amino group (NH(sec)), N(py) and two acetate groups, one acts as a unidentate and the other as a bidentate. A theoretical DFT/UB3LYP method combined with LANL2DZ basis set shows that all the metal-ligand bonds are of the L→M type. Electronic structures have been calculated using TD-DFT method. The antibacterial activity of NiL(2) complexes decreases by the introduction of COOCH(3) group in the ortho-position of the aniline moiety.

Molecular structures of 2-arylaminomethyl-1H-benzimidazole: Spectral, electrochemical, DFT and biological studies

In the present work, structural studies on (1H-benzimidazol-2-ylmethyl)-N-(4-chloro-phenyl)-amine (L(1)) and (1H-benzimidazol-2-ylmethyl)-N-(4-iodo-phenyl)-amine (L(2)) have been done extensively by a variety of physico-chemical techniques. Optimized geometrical structures, harmonic vibrational frequencies, natural bonding orbital (NBO) analysis, and Frontier molecular orbitals (FMO) were obtained by DFT/B3LYP method. TD-DFT calculations help to assign the electronic transitions. The polarizable continuum model (PCM) fails to describe the experimental chemical shift associated with the NH protons as calculated by applying Gauge-invariant atomic orbital (GIAO) method, but a very good correlation between the theoretical and experimental values was achieved by taking into account the specific solute-solvent interactions. DFT calculations showed a good agreement between the theoretical and observed results. These compounds exhibited a high biological activity through the inhibition of the metabolic growth of the investigated bacteria.

2-[(1H-Benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester: Crystal structure, DFT calculations and biological activity evaluation

In the present study, structural properties of 2-[(1H-benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester have been studied extensively by spectral methods and X-ray crystallography. Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, NMR and electronic transitions were carried out by DFT using B3LYP functional combined with 6-31G(d) basis set. Natural bond orbitals (NBO) analysis and frontier molecular orbitals were performed at the same level of theory. DFT calculations showed good agreement between the theoretical and experimental values of optimized and X-ray structure as well as between the vibrational and NMR spectroscopy. The title compound was screened for its antibacterial activity referring to Tetracycline as standard antibacterial agent.

Photocatalytic degradation of methylene blue with hematite nanoparticles synthesized by thermal decomposition of fluoroquinolones oxalato–iron(III) complexes

[Fe(C2O4)(FQ)(H2O)2] complexes (H-FQ = ciprofloxacin (1), lomefloxacin (2) and norfloxacin (3)) were synthesized and characterized using a variety of analytical and spectral techniques such as elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, magnetic and conductance measurements. The experimental studies were complemented by quantum chemical calculations in terms of geometry optimization, natural bond orbital analysis and molecular electrostatic potential maps. Electronic structures were discussed by TD-DFT. Hematite (α-Fe2O3) nanoparticles, as promising materials for different catalytic applications, were prepared in air via the controlled thermal decomposition of 1–3. Powder X-ray diffraction was used to identify the polymorph of iron oxide. The morphology of nano-hematite was investigated by a field emission scanning electron microscope coupled to energy-dispersive X-ray spectroscopy for surface analysis. The catalytic degradation of methylene-blue (MB), as an industrial pollutant, exposed to UV radiation in the presence of nano-α-Fe2O3 as a catalyst and hydrogen peroxide as the oxidant was studied at room temperature in water.

Selective coordination ability of sulfamethazine Schiff-base ligand towards copper(II): molecular structures, spectral and SAR study.

In the present work, a combined experimental and theoretical study of the N-(4,6-Dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)amino]benzenesulfonamide ligand (H2L) and its mononuclear and magnetically diluted binuclear Cu(II) complexes has been performed using IR, TG/DTA, magnetic, EPR, and conductivity measurements. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using the MPW1PW91 functional. Coordination of H2L to a Cu(II) center, regardless of the binding site and Cu:L stoichiometry, leads to a significant decrease in the antibacterial activity compared to the free ligand as well as reference drugs in the case of Staphylococcus aureus. Structural-activity relationship suggests that ELUMO, ΔE, dipole moment, polarizability and electrophilicity index were the most significant descriptors for the correlation with the antibacterial activity.

Sulfamethazine copper(II) complexes as antimicrobial thermal stabilizers and co-stabilizers for rigid PVC: spectroscopic, thermal, and DFT studies

[CuL2(OH2)]·1.5H2O (1), [CuL2(bpy)]·0.66H2O (2) and [CuLQ(OH2)]·H2O (3) (HL = sulfamethazine, bpy = 2,2′-bipyridine and HQ = 8-hydroxyquinoline) complexes were prepared, characterized (elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, magnetic and conductivity measurement), and tested for their antibacterial activity. Coordination of HL to the Cu(II) ion did not markedly change its toxicity, but the presence of a secondary ligand gave rise to lower activity. Sulfamethazine and its complexes have been investigated as thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride). A synergism has been achieved when the investigated compounds were mixed in an equivalent weight ratio with the reference stabilizers. The experimental studies have been complemented by density functional theory data in terms of optimization, natural bond orbital (NBO) analysis, and molecular electrostatic potential maps. The structural-thermal stabilization relationship showed that energy of the highest occupied molecular orbital, ΔE, and softness were the most useful descriptors for the correlation with the thermal stability.

New thiocyanate potentiometric sensors based on sulfadimidine metal complexes: experimental and theoretical studies.

Three sulfadimidine metal complexes (M=Fe(III), Cu(II), and Ag(I)) were prepared, characterized, and examined as neutral carriers for the determination of SCN(-) using modified carbon paste electrode. These sensors were successfully applied in the pure samples, and biological fluids. The electrode mechanism was investigated by UV-vis and FT IR. The experimental studies were complemented by quantum chemical calculations at DFT/B3LYP level of theory. The best performance was observed for Cu(II) electrode (C) containing 7.0% complex, 53.0% o-nitrophenyloctyl ether, 37.0% graphite and 3.0% cetylpyridinium chloride, and also for Fe(III)-electrode (A) having 6.0% complex, 52.0% o-nitro phenyloctyl ether, 40.5% graphite and 2.5% cetylpyridinium chloride.

DFT studies, spectral and biological activity evaluation of binary and ternary sulfamethazine Fe(III) complexes

[FeL3]·H2O (1) and [FeL2Q]·3H2O (2) (HL = sulfamethazine and HQ = 8-hydroxyquinoline) have been synthesized, characterized (elemental analysis, FT IR, UV–vis, TGA, magnetic and conductivity), and tested for their antibacterial activity against Staphylococcus aureus and Escherichia coli. Theoretical calculations involving geometry optimization, natural orbital analysis, electronic spectra, and molecular electrostatic potential have been done at the DFT/B3LYP level of theory. The high 3d-electron contribution of 6.71 is accounted to L → dFe charge transfer. Coordination of HL to Fe(III) in 1 led to a significant decrease in the antibacterial activity, and presence of a secondary ligand in 2 completely abolished it. Graphical Abstract Coordination of sulfamethazine drug to Fe(III) center 1 led to a significant decrease in the antibacterial activity, but presence of a secondary ligand 2 gave rise to inactive compound.