Ahmed M. El-Nahas

Effect of structural properties of acid dyes on their adsorption behaviour from aqueous solutions by amine modified silica

Monoamine modified silica particles (MAMS) were prepared and characterized by infrared (FT-IR) and thermogravimetric analysis (TGA). The modified silica particles were used for removal of acid orange 10 (AO-10) and acid orange 12 (AO-12) from their aqueous solutions. The adsorption behaviour of the two dyes was studied at different experimental conditions of pH, contact time, concentration of dye, temperature and salt solution. The adsorption of AO-10 followed pseudo-first order kinetics whereas AO-12 followed pseudo-second order. The two dyes showed different modes of interaction with silica surface. Desorption of the loaded dyes was carried out at pH 10 and found to be 10.4 and 91.6% for AO-12 and AO-10, respectively.

Structural studies and anticancer activity of a novel (N6O4) macrocyclic ligand and its Cu(II) complexes

A novel (N6O4) macrocyclic ligand (L) and its Cu(II) complexes have been prepared and characterized by elemental analysis, spectral, thermal (TG/DTG), magnetic, and conductivity measurements. Quantum chemical calculations have also been carried out at B3LYP/6-31+G(d,p) to study the structure of the ligand and one of its complexes. The results show a novel macrocyclic ligand with potential amide oxygen atom, amide and amine nitrogen atoms available for coordination. Distorted square pyramidal ([Cu(L)Cl]Cl·2.5H2O (1), [Cu(L)NO3]NO(3)·3.5H2O (2), and [Cu(L)Br]Br·3H2O (4) and octahedral ([Cu(L)(OAc)2]·5H2O (3)) geometries were proposed. The EPR data of 1, 2, and 4 indicate d1x2(-y)2 ground state of Cu(II) ion with a considerable exchange interaction. The measured cytotoxicity for L and its complexes (1, 2) against three tumor cell lines showed that coordination improves the antitumor activity of the ligand; IC50 for breast cancer cells are ≈8.5, 3, and 4 μg/mL for L and complexes (1) and (2), respectively.

A theoretical study on the catalysis of Cu-exchanged zeolite for the decomposition of nitric oxide

The catalysis of Cu-exchanged zeolite for the direct decomposition of nitric oxide was investigated by hybrid density functional theory (B3LYP) using a molecular model of the active site. For reactions of two NO molecules over a Cu ion bound to the zeolite model (ZCu), the structures and energies of adsorption complexes and transition states were examined and compared with those of the corresponding reactions over an isolated Cu+ and Cu atom and also reactions of free NO. The ZCu shows an enhanced catalytic activity compared with the isolated Cu+. The ZCu and adsorbed molecules interact strongly in the transition state structures through π(d–p) bonding. Theory also suggests that the Cu atom has the potential to be a highly active catalyst for the NO decomposition reaction.

Thermal Decomposition of 2-Butanol as a Potential Nonfossil Fuel: A Computational Study

The thermochemistry and kinetics of the pyrolysis of 2-butanol have been conducted using ab initio methods (CBS-QB3 and CCSD(T)) and density functional theory (DFT). The enthalpies of formation and bond dissociation energies of some alcohols including 2-butanol and its derived radicals have been calculated. A variety of simple and complex dissociations have been examined. The results indicated that dehydration to 1- and 2-butene through four-center transition states is the most dominant channel at low to moderate temperatures (T ≤ 700 K), where formation of butenes is kinetically and thermodynamically more favorable than other complex and simple bond scission reactions. Although the C-C bond fission channels require more energy than needed for some complex decomposition reactions, the former pathways predominate at higher temperatures (T ≥ 800 K) due to the higher values of the pre-exponential factors. The progress of the complex decomposition reactions has been followed through intrinsic reaction coordinate (IRC) calculations to understand the mechanism of transformation of 2-butanol to different products.

On the existence of Cu2+(NH3)1,2 and Cu2+(OH2)1,2 in the gas phase

Abstract This Letter is prepared to reply the comment by Stace et al. [A.J. Stace, N.R. Walker, R.R. Wright, S. Firth, Chem. Phys. Lett. 329 (2000) 173–175] on our Letter in Chemical Physics Letters [A.M. El-Nahas, N. Tajima, K. Hirao, Chem. Phys. Lett. 318 (2000) 333]. The authors performed new experiments and showed the presence of clear peaks with the same m/z values as the ions of interest. They assigned these peaks to fragmentation of impurities and not to the decomposition products of the Cu 2+ systems. It is recommended that the experimental determination of the desired products be repeated. Our calculations have been performed at high ab initio level of theory and this provides strong evidence for the stability of di-ligated Cu 2+ complexes with water and ammonia and proposes the possibility of detecting one-ligand systems.

Thermochemically stable M2+OH2 complexes in the gas phase: M=Mn, Fe, Co, Ni, and Cu

Abstract The interaction of first-row transition metal ions (Mn2+ to Cu2+) with a single water molecule is presented at B3LYP and CCSD(T) levels of theory using triple-zeta quality basis sets. Transition states for the dissociation of the M2+OH2 complexes to M+ and H2O+ (i.e., M 2+ OH 2 →[ M ( OH 2 )] 2+ → M + + + OH 2 ) are located. The results obtained greatly support the possibility of observing all of the investigated M2+OH2 complexes as long-lived species with abundance increases toward the left-hand side in the periodic table.

Synthesis and Photophysical Property Studies of the 2,6,8-Triaryl-4-(phenylethynyl)quinazolines

The 2-aryl-6,8-dibromo-4-chloroquinazolines derived from the 2-aryl-6,8-dibromoquinazolin-4(3H)-ones were subjected to the Sonogashira cross-coupling with terminal acetylenes at room temperature to afford novel 2-aryl-6,8-dibromo-4-(alkynyl)quinazoline derivatives. Further transformation of the 2-aryl-6,8-dibromo-4-(phenylethynyl)quinazolines via Suzuki-Miyaura cross-coupling with arylboronic acids occurred without selectivity to afford the corresponding 2,6,8-triaryl-4-(phenylethynyl)quinazolines. The absorption and emission properties of these polysubstituted quinazolines were also determined.

Quantum chemical calculations on metal dications solvated by formaldehyde, acetone and DMSO ligands

Abstract Ab initio and DFT calculations have been carried out to explore the thermodynamic and/or kinetic stabilities of M 2+ L complexes (M=Be, Mg, Ca, and Zn, L=formaldehyde, acetone, and DMSO). Based on the computational data, all of the investigated monoligated doubly charged metal cation complexes are expected to be observable in the gas phase. In addition to thermodynamic stability, the kinetic energy barriers further stabilize the monoligated doubly charged metal cations. Thermodynamically unstable complexes are stabilized by Coulomb barriers. Monoligated metal dications have been classified into metastable and thermodynamically stable species. Comparison with experiments indicates agreement for magnesium and calcium containing systems.

Monohydrated alkaline earth metal dications do exist

Abstract The potential energy surfaces for Be 2+ OH 2 and Mg 2+ OH 2 dications in the gas phase have been investigated at B3LYP and CCSD(T) levels of theory. Different dissociation channels have been taken into account. The results indicate that the monohydrated Be and Mg dications are thermodynamically and kinetically stable species and coulomb explosion is hindered by a barrier of 57–75 kcal/mol. The Be 2+ OH 2 and Mg 2+ OH 2 dications can dissociate to M + and + OH 2 if sufficient kinetic energy is given to the system.

Oxidative Stress Induced by Pt(IV) Pro-drugs Based on the Cisplatin Scaffold and Indole Carboxylic Acids in Axial Position.

The use of Pt(IV) complexes as pro-drugs that are activated by intracellular reduction is a widely investigated approach to overcome the limitations of Pt(II) anticancer agents. A series of ten mono- and bis-carboxylated Pt(IV) complexes with axial indole-3-acetic acid (IAA) and indole-3-propionic acid (IPA) ligands were synthesized and characterized by elemental analysis, ESI-MS, FT-IR, 1H and 195Pt NMR spectroscopy. Cellular uptake, DNA platination and cytotoxicity against a panel of human tumor cell lines were evaluated. All the complexes are able to overcome cisplatin-resistance and the most potent complex, cis,cis,trans-[Pt(NH3)2Cl2(IPA)(OH)] was on average three times more active than cisplatin. Mechanistic studies revealed that the trend in cytotoxicity of the Pt(IV) complexes is primarily consistent with their ability to accumulate into cancer cells and to increase intracellular basal reactive oxygen species levels, which in turn results in the loss of mitochondrial membrane potential and apoptosis induction. The role of the indole acid ligand as a redox modulator is discussed.