Mostafa M. Kamal

Kinetics of hydrolysis of some N′-(4-substituted benzylidene) salicylohydrazides

The rates of hydrolysis of a series of substituted benzylidenesalicylohydrazide derivatives in 40%(v/v) ethanol–buffer mixture have been investigated by differential pulse polarography. The hydrolysis is catalysed by H+ and its rate follows strictly first-order kinetics. The rate constant decreases with increasing pH up to around pH 3.9, beyond which no measurable reaction was observed; here the protonation of imine begins to be significantly incomplete. The attack of water on the protonated substrate is considered to be the rate-determining step. The effects of pH, molecular structure, and temperature on the reaction rate and the activation energy are reported. Thermodynamic parameters (ΔG‡, ΔH‡, and ΔS‡) for the hydrolysis are discussed.

Spectrophotometric Studies of the Coordination Polymers Based on Poly(8-Hydroxyquinoline) Matrix

Incorporation of various metal ions into a poly(8-hydroxyquinoline) (PHQ) matrix via a complexation mechanism to form the corresponding coordination polymers was investigated experimentally and computationally. TGA, DTG, MS, and elemental analysis measurements show that the polymeric chelates of copper(II) ion with the PHQ matrix have a hydrophilic nature about two-times stronger than the salt (i.e., copper acetate monohydrate). The results of DSC, TGA, and DTG suggest that the PHQ-Cu(II) matrix is more thermally stable than the copper acetate complex. A first-order derivative treatment of the UV-visible absorption spectra of the matrixes under investigation is sensitive to at least 1.5-times that of the normal (zero-order derivative) spectra. Analysis of the absorbance vs. mole fraction data for metal ions such as Cu(II), Ni(II), Co(II), and Fe(III), which are coordinated to the PHQ matrix, afforded information about the equilibria that prevailed in solution. The largest stability constant (log β) corresponds to a stiochiometric ratio of 2PHQ:1Mn+. The results are supported by elemental analysis, TGA, DTG, and mass spectroscopic measurements, and are consistent with molecular mechanics (MM+) calculations. A simple, rapid and sensitive method for the spectrophotometric determination of trace amounts of Cu(II) ion in solution by coordination with the PHQ matrix is proposed. The method has been applied successfully to the determination of Cu(II) ion in Heamoton capsule samples (mg/g). The proposed method is in excellent agreement with the determination of Cu(II) ion by atomic absorption spectrometry.

Differential pulse polarographic determination of some nucleic acid components

Abstract The analytical application of differential pulse polarography (d.p.p) for the quantitative determination of cytosine, cytidine, cytidylyl-(3′–5′)-cytidine (CpC) and cytidylyl-(3′–5′)-adenosine (CpA) has been investigated. The dependence of the differential pulse peak on various quantities (pH, pulse amplitude, scan rate and drop time) was studied and the optimum conditions for the analytical determination of these compounds were found. The detection limit for cytidine, CpC and CpA was 0.5–1.0 μM; for cytosine it was 5 μM. Results of the analysis of mixtures of cytidine-cytosine, cytidine-CpA and cytidine-CpC are reported under the optimum conditions. The analytical determination of cytidine, CpC and CpA in the presence of the same concentration of cytosine was also investigated.

Studies on the reaction of salicylidenebenzoic-hydrazide (SBH) with Ce3+, Th4+ and UO22+

The stoichiometry and structure of salicylidenebenzoic-hydrazine (SBH) chelates with UO2(II), Ce(III) and Th(IV) in buffer-ethanol mixtures and in pure ethanol is studied applying conductometric titration, visible spectrophotometry and ir-spectrophotometry. The ir-spectra revealed that coordination takes place through the C=O and C=N groups.ZusammenfassungDie Stöchiometrie und die Struktur derSBH-Me(x) Chelate in Puffer-Ethanol-Mischungen und in reinem Ethanol wurde mittels Leitfähigkeitsmessungen, UV- und IR-Spektroskopie untersucht. Insbesondere die IR-Messungen zeigen, daß die Koordination über die C=O- und C=N-Gruppierung stattfindet.The stoichiometry and structure of salicylidenebenzoic-hydrazine (SBH) chelates with UO2(II), Ce(III) and Th(IV) in buffer-ethanol mixtures and in pure ethanol is studied applying conductometric titration, visible spectrophotometry and ir-spectrophotometry. The ir-spectra revealed that coordination takes place through the C=O and C=N groups.

Resolution and Trace Determination of Selected Oxyanions in Binary and Ternary Mixtures by Differential Pulse Polarography

Abstract Resolution and trace determination of selected oxyanions in binary and ternary mixtures were studied by differential pulse polarography (DPP) at the dropping mercury electrode. The applicability of DPP for the simultaneous determination of the investigated oxyanions (TeO2- 4, VO− 3, IO− 3, IO− 4, and BrO− 3) in the binary and ternary mixtures was also examined with regard to the dependence of the DP current on various parameters such as pH, pulse amplitude, scan rate and drop time. Statistical analysis is included on t h e observed concentrations for each of the oxyanions in the mixture and compared with that obtained by the calibration curves. Limits of detection and quantitat - ion have been calculated for the DPP determination of binary and ternary mixtures of these lected oxyanions.

Mixed dithizonato-alkylxanthato complexes of Ni(II): spectral, magnetic, and thermogravimetric studies

Mixed ligand complexes of the type Ni(ROCS2)HDz) have been prepared, where R = methyl, ethyl, propyl, butyl and cyclohexyl, and HDz = dithizonate anion. These complexes were identified on the basis of spectroscopic measurements (IR, UV-VIS and NMR), magnetic moment values, thermogravimetric analysis, and analytical data. The results permit assignment of a tetrahedral structure for these complexes.

Studies on the chelation of cytosine, cytidine and cytidine phosphate with U(VI), Th(IV), Ce(III) and La(III)

Abstract The complexes formed between cytosine, cytidine and cytidine phosphate and U(VI), Th(IV), Ce(III) and La(III) have been investigated using spectrophotometric and conductometric methods. The apparent formation constants of these complexes have been calculated. The mode of bonding of the ligand in the solid chelates was studied by I.R. spectrophotometry which showed that chelate formation takes place through C(2)O and CN(3) groups in the case of cytosine and cytidine. The I.R. spectra of cytidine phosphate complexes indicated a tridentate ligand which coordinated via the former two groups and phosphate groups to the central metal ion.

Studies on Some Metal Chelates of 8-Hydroxy-Quinoline-5-Sulphonylhydrazide

Abstract Cu(II), Zn(II), Cd(II), Pb(II) and UO2(II) complexes of 8-hydroxyquinoline-5-sulphonylhydrazide (QSH) have been investigated. The formation, stoichiometry and stability of the complexes have been tested in solution using electronic spectral measurements and conductometric titrations. Characterization of the isolated solid complexes has been performed on the basis of elemental analysis, electronic and IR spectral data as well as polarographic measurements. It is concluded that the ligand acts as a monobasic ON bidentate ligand. The different bands observed in the electronic spectra of the ethanolic solution of the complexes have been assigned to the L + MCT and d-d electronic transitions.

Reactivity of 1,1-DithioIato Ni(II) and Co(II) with Phenylthiourea, Chlorophenylthiourea and Bis(diphenylphosphinothioyl)methane

Abstract The following mixed ligand complexes were synthesized and characterized: Co(Phdtcz)2(Phtu)2, Co(Phdtcz)2(Clphtu)2 , Co(Phdtcz)2(dtm), Ni(Et2dtc)2(dtm), Ni(Phdtc)2(dtm), Ni(p-Toluiddtc)2(dtm), Ni(α-naphdtc)2(dtm), and Ni(Phdtcz)(Et2dtc); where Phdtcz = phenyldithiocarbazate, Et2dtc = diethyldithiocarbamate, Phdtc = phenyldithiocarbamate, p-Toluiddtc = p-toluidinedithiocarbamate, α-naphdtc = α-naphthyldithiocarbamate, Phtu = phenylthiourea, Clphtu - chlorophenylthiourea, and dtm - bis(diphenylphosphinothioyl)-methane. Electronic and IR spectra, magnetic, conductivity and X-ray powder diffraction measurements were carried out. The Ni(II) and Co(II) complexes are suggested to be square planar and octahedral, respectively. The biological activity of the complexes was also tested.

Synthesis and Characterization of Some Transition Metal Complexes of Arylidene Salicyloyl and Benzoyl Hydrazones

Abstract Complexes of arylidene salicyloyl- and benzoyl-hydrazones with the 3d metal ions, Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II), have been prepared using 2:1 ligand to metal ion ratio. Characterization of the isolated solids was accomplished by IR and electronic spectra, elemental analysis, and molar conductivity measurements. It is concluded that the two Schiff bases function as neutral bidentate ligands and the complexes formed assume a distorted octahedral geometry.