Mohamed K. Awad

Synthesis, characterization, and biological activity studies of copper(II)–metal(II) binuclear complexes of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone)

A new series of copper(II) mononuclear and copper(II)–metal(II) binuclear complexes [(H2L)Cu] ⋅ H2O, [CuLM] ⋅ nH2O, and [Cu(H2L)M(OAc)2] ⋅ nH2O, n = 1–2, M = Co(II), Ni(II), Cu(II), or Zn(II), and L is the anion of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone), H4L, were synthesized and characterized. Elemental analyses, molar conductivities, and FT-IR spectra support the formulation of these complexes. IR data suggest that H4L is dibasic tetradentate in [(H2L)Cu] ⋅ H2O and [Cu(H2L)M(OAc)2] ⋅ nH2O but tetrabasic hexadentate in [CuLM] ⋅ nH2O (n = 1–2). Thermal studies indicate that waters are of crystallization and the complexes are thermally stable to 347–402°C depending upon the nature of the complex. Magnetic moment values indicate magnetic exchange interaction between Cu(II) and M(II) centers in binuclear complexes. The electronic spectral data show that d–d transitions of CuN2O2 in the mononuclear complex are blue shifted in binuclear complexes in the sequences: Cu–Cu > Cu–Ni > Cu–Co > Cu–Zn, suggesting that the binuclear complexes [CuLM] ⋅ nH2O are more planar than the mononuclear complex. The structures of complexes were optimized through molecular mechanics applying MM +force field coupled with molecular dynamics simulation. [(H2L)Cu] ⋅ nH2O, [CuLM] ⋅ nH2O, and the free ligand were screened for antimicrobial activities on some Gram-positive and Gram-negative bacterial species. The free ligand is inactive against all studied bacteria. The screening data showed that [CuLCu] ⋅ H2O > [(H2L)Cu] ⋅ H2O > [CuLZn] ⋅ H2O > [CuLNi] ⋅ 2H2O ≈ [CuLCo] ⋅ H2O in order of biological activity. The data are discussed in terms of their compositions and structures.

Photophysical properties and semiempirical calculations of perylene-3,4,9,10-tetracarboxylic tetramethylester (PTME)

The spectral behavior and fluorescence quantum yield of perylene-3,4,9,10-tetracarboxylic tetramethylester (PTME) have been measured in different solvents. Both electronic absorption and fluorescence spectra are not sensitive to medium polarity. The dye exhibits high fluorescence quantum yield and high photostable. Crystalline solid of PTME gives excimer-like emission at 530 nm. The laser activity of PTME has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 480 nm upon excitation by 337.1 nm nitrogen laser pulse. The excitation energy transfer from 7-dimethylamino-4-methylcoumarine (DMC) to PTME has also has been studied and the value of energy transfer rate constant, k(ET), and critical transfer distance, R(0) indicate a Förster-type mechanism. The photodecomposition of PTME in chloromethane solvents has been also studied. We applied semiempirical MO calculations using (PM3 and ZINDO-CI) calculations to explain the geometric and electronic behaviors of the PTME molecule in both ground and excited states and make a correlation with the experimental observations.

Spectral, magnetic studies and molecular orbital calculations for (4,5-dimethyl-3-pyrazolyl)aldazine copper(II) complexes

SummaryA new series of copper(II) complexes derived from (4,5-dimethyl-3-pyrazolyl) aldazine (DMPA), formulated as: (a) [LCuX2]·nEtOH; (b) [LCu(H2O)](ClO4)2; and (c) [LCuX]BF4·nH2O, where n = 1/2 or 1, X = Cl or Br and L = DMPA, have been synthesized. The formulations are based on elemental analyses and molar conductivity data. I.r., u.v.-vis., e.s.r. and magnetic data reveal that the complexes are trigonal bipyramidal, tetrahedral and stacked square-planar structures for (a), (b) and (c), respectively. The trigonal bipyramidal structure for class (a) compounds is confirmed using the atom superposition and electron delocalization-molecular orbital calculations, which agree with the experimental electronic spectral data. Variable temperature magnetic susceptibility data shows a ferromagnetic interaction within copper(II) complexes of class (c).

Quantum chemical studies and atomistic simulations of some inhibitors for the corrosion of al surface

Atomistic simulations are becoming increasingly important in the field of corrosion inhibition. New research and development efforts using computational chemistry in studying the behavior of corrosion inhibitors on the metal surfaces are introduced. Accordingly, the density functional theory (DFT) at the B3LYP/6-31G++(d,p) basis set level, ab initio calculations using the HF/6-31G++(d,p) and MP2/321G+(d) methods are performed on some triazoles and sulphur containing compounds, namely, 1,2,4-triazole (TA), 3-amino-1,2,4-triazole (ATA), benzotriazole (BTA) and 2-mercaptobenzothiazole (MTA), used as corrosion inhibitors. The correlation between its quantum chemical parameters and the corresponding inhibition efficiency (IE%) is investigated. Quantum chemical parameters, such as the energy of the highest occupied molecular orbital energy (EHOMO), the energy of the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (µ), sum of total negative charges (TNC), molar volume (MV), polarizability (α), chemical potential (Pi), electronegativity (χ), hardness (η), softness (σ), electrophilicity (ω) and the total energy change (ΔET), are calculated. Furthermore, Monte Carlo simulation technique incorporating molecular mechanics and molecular dynamic is used to simulate the adsorption of the investigated inhibitors on Al (1 1 1) surface. A good correlation is found between the theoretical data and the experimental results.

Molecular docking, molecular modeling, vibrational and biological studies of some new heterocyclic α-aminophosphonates

A new diphenyl (aryl) (Ǹ-quinazolin-4-yl-hydrazino) methylphosphonates 3a-3d was synthesized via anhydrous zinc chloride catalyzed Kabachnic-Fields reaction. The structure of the synthesized compounds was confirmed by elemental analysis, FT-IR, 1H NMR, 13C NMR, 31P NMR and MS spectral data. The synthesized compounds showed significant antimicrobial and also remarkable cytotoxicity anticancer activities against breast carcinoma cell line (MCF7). The quantum chemical calculations were performed using density functional theory (DFT) to study the effect of the changes of molecular and electronic structures on the biological activity of the investigated compounds. Also, NBO and theoretical FT-IR were calculated. The experimental results were validated by molecular docking simulation of compound 3b in the active pocket of the enzyme. The important binding interactions with the key residues in the active site were revealed. A good correlation was found between the quantum chemical parameters and experimental data.

Factors Influencing the Potency of Alzheimer Inhibitors: Computational and Docking Studies

Density functional theory (B3LYP/6-31G [d]) is performed to study the effect of molecular and electronic structures of the investigated β-secretase 1 (BACE1) Alzheimer’s inhibitors on their biological activities and discuss the correlation between their inhibition efficiencies and quantum chemical descriptors. IC50 values of the investigated compounds are mostly affected by the substituted R2 phenyl moiety. The calculations show that the presence of electron withdrawing group increases the half maximal inhibitory concentration (IC50). Structure–activity relationship studies show that the electronic descriptors, energy of high occupied molecular orbital, ΔE, lipophilicity, hardness, and ionization potential index, are the most significant descriptors for the correlation with IC50. Molecular docking simulation is performed to explain the mode of interaction between the most potent drug and the binding sites of the BACE1 target. A good correlation between the experimental and the theoretical data confirms that the quantum chemical methods are successful tools for the discovery of novel BACE1 drugs.