Mohamed Shaker S. Adam

Some New Nano-sized Mononuclear Cu(II) Schiff Base Complexes: Design, Characterization, Molecular Modeling and Catalytic Potentials in Benzyl Alcohol Oxidation

In the present contribution, some novel Cu(II) complexes were synthesized from tri- and tetradentate imine ligands. All the prepared compounds were elucidated by different physicochemical methods. Density Functional Theory calculations were carried out to explain the equilibrium geometry of the bsisnph and npisnph ligands and their Cu(II) complexes. Interaction of the synthesized ligands with Cu(II) affords nano-sized particles via TEM. The catalytic potentials of the prepared complexes has been tested within the oxidation of benzyl alcohol using an environmental friendly terminal oxidant, i.e. H2O2. The effect of various parameters, e.g. solvents, temperature and amount of catalyst was investigated. A mechanistic pathway of the catalytic oxidation was tentatively described and discussed.Graphical Abstract

Hydrophilicity and acid hydrolysis of water-soluble antibacterial iron(II) Schiff base complexes in binary aqueous solvents

Kinetics of acid hydrolysis of seven antibacterial iron(II) Schiff base complexes has been studied. The Schiff base ligands were derived from sodium 2-hydroxybenzaldehyde-5-sulfonate and a series of amino acids. The hydrolysis rate is studied by spectrophotometric method and compared with complex hydrophilicity. Addition of the organic co-solvent, dimethylsulfoxide or n-propanol, significantly accelerates the hydrolysis.

Reactivity of base catalysed hydrolysis of 2-pyridinylmethylene-8-quinolinyl-Schiff base iron(II) iodide complexes: solvent effects

Three ligands of 2-pyridinylmethylene-8-quinolinyl (L1), methyl-2-pyridinylmethylene-8-quinolinyl (L2), and phenyl-2-pyridinylmethylene-8-quinolinyl (L3), Schiff bases were synthesised by direct condensation of 8-aminoquinoline with 2-pyridinecarboxaldehyde, 2-acetylpyridine, or 2-benzoylpyridine. They coordinated to Fe(II) ion in a 1: 2 mole ratio followed by treatment with iodide ions affording complexes with a general formula [Fe(L)2]I2·2H2O, (L = L1, L2, or L3). Spectrophotometric evaluation of the kinetics of base catalysed hydrolysis of these complex cations was carried out with an aqueous solution of NaOH in different ratios of water/methanol binary mixtures. Kinetics of the hydrolysis followed the rate law (k2[OH−] + k3[OH−]2)[complex]. Reactivity trends and their rate constants were compared and discussed in terms of ligand structure and solvation parameters. The methanol ratio affects the hydrolysis as a co-solvent which was analysed into initial and transition state components. The increase in the rate constant of the base hydrolysis of Fe(II) complexes, as the ratio of methanol increases, is predominantly caused by the strong effect of the organic co-solvent on the transition states.

Synthesis and characterization of novel bis(diphenylphosphino)-oxalyl and (substituted) malonyl dihydrazones: P,N,N,P-tetradentate complexes of an oxalyl derivative with Cu(II), Pd(II), and Mn(II)

Abstract Novel ligands of bis(diphenylphosphino)-oxalyl, malonyl, and methyl- and ethyl-malonyl dihydrazones were synthesized by condensation of oxalyl, malonyl, methyl-malonyl, and ethyl-malonyl dihydrazide with o-(diphenylphosphino)benzaldehyde in different conditions. The dihydrazones exhibit three different tautomeric structures detected by NMR and IR spectra. The 31P NMR spectrum demonstrates four different singlet signals, i.e., chemical shifts, of the three respective tautomers. Complexes of the oxalyl ligand with Pd2+, Cu2+, and Mn2+ ions are formed in 1:1 molar ratio. Their structures were characterized by IR, NMR, EPR, MS, EA, and TGA, in which the oxalyl ligand acts as a neutral P,N,N,P-tetradentate chelate. The pH stability of the complexes is in the region of ca. 4.5–7.5 and their activation energy was calculated from the conductivity measurements.Graphical abstract

Pyrido-anellated 1,3-azaphospholes-current state and future challenges

GRAPHICAL ABSTRACT ABSTRACT A short overview of the syntheses, properties and some reactions of pyrido-anellated 1.3-azaphospholes is presented. Except for 2-phosphaindolizines, which have been intensively studied with respect to syntheses, electrophilic substitution and cycloadditions, this is a class of compound that has still been only sparingly investigated. Preliminary results and hints as to possible perspectives are included to encourage further research on these novel P,N hybrid ligands.

Effect of bromide salts on the acid hydrolysis of anti-bacterial hydrophilic Schiff base amino acid iron(II) complexes

Salt effects on the kinetics of acid hydrolysis of some novel hydrophilic iron(II) complexes have been investigated in aqueous medium. The ligands are derived from the condensation of amino acids (glycine, L-alanine, L-leucine, L-isoleucine, DL-methionine, DL-serine or L-phenylalanine) and sodium 2-hydroxybenzaldehyde-5-sulfonate. The reaction was studied under conditions of pseudo first order kinetics. The general rate equation was suggested as follows: rate = kobs[complex], where kobs = k2[H+]. The reaction rate decreases with an increase of the salt concentration.

Kinetics of acid hydrolysis and reactivity of some antibacterial hydrophilic iron(II) imino-complexes

Kinetic study of acid hydrolysis of some hydrophilic Fe(II) Schiff base amino acid complexes with antibacterial properties was performed using spectrophotometry. The Schiff base ligands were derived from sodium 2-hydroxybenzaldehyde-5-sulfonate and glycine, L-alanine, L-leucine, L-isoleucine, DL-methionine, DL-serine, or L-phenylalanine. The reaction was studied in aqueous media under conditions of pseudo-first order kinetics. Moreover, the acid hydrolysis was studied at different temperatures and the activation parameters were calculated. The general rate equation was suggested as follows: rate = kobs [Complex], where kobs = k2 [H+]. The evaluated rate constants and activation parameters are consistent with the hydrophilicity of the investigated complexes.

Novel Benzo-and Pyrido-Anellated 1, 3-Azaphospholes

We present the synthesis of OH-functional and bulky N-substituted benzazaphospholes, novel pyrido-azaphospholes, addition versus CH-metalation by tBuLi and reactions with electrophiles yielding a novel asymmetric P,N-heterocyclic ethylene-1,2-bis(phosphine) and phosphino-functional benzazaphospholes for hemilabile σ3,σ2–P,P′ coordination.