M.M. Ghoneim

Polymer complexes. LX. Supramolecular coordination and structures of N(4-(acrylamido)-2-hydroxybenzoic acid) polymer complexes

A number of novel polymer complexes of various anions of copper(II), cobalt(II), nickel(II) and uranyl(II) with N(4-(acrylamido)-2-hydroxy benzoic acid) (ABH) have been synthesized and characterized by elemental analysis, IR, 1H NMR, magnetic susceptibility measurements, electronic spin resonance, vibrational spectra and thermal analysis. The molecular structures of the ligand are optimized theoretically and the quantum chemical parameters are calculated. Tentative structures for the polymeric metal complexes due to their potential application are also suggested. The IR data exhibit the coordination of ONO2/OAc/SO4 with the metal ions in the polymeric metal complex. Vibrational spectra indicate coordination of carboxylate oxygen and phenolic OH of the ligand giving a MO4 square planar chromophore. Ligand field ESR spectra support square planar geometry around Cu(II). The thermal decomposition of the polymer complexes were discussed in relation to structure, and the thermodynamic parameters of the decomposition stages were evaluated applying Coast-Redfern and Horowitz-Metzger methods.

Inhibition of copper corrosion by arylazotriazoles in nitric acid solution

SummaryA study has been made to investigate the effect of some azoheterocyclic dyes of the type 3-arylazo 1,2,4-triazole (AT) on the corrosion of copper exposed to 0.5M nitric acid solution at different temperatures and at differentAT concentrations. Using potentiodynamic polarization andTafel electrochemical methods, it can be shown thatAT compounds are good inhibitors of copper corrosion in HNO3 solution. The kinetic and thermodynamic parameters of the inhibited system were determined. The high inhibition efficiency of these compounds may be due to the adsorption of the additive itself and/or the adsorption of the formed Cu(II)-AT complexes at the polarized electrode interface. Cathodic polarization measurements showed thatAT dyes are predominantly cationic inhibitors.ZusammenfassungDer Effekt einiger azoheterocyclischer Farbstoffe des Typs 3-Arylazo-1,2,4-triazol (AT) auf die Korrosion von Kupfer in 0.5M Salpetersäure bei verschiedenen Temperaturen und unterschiedlichenAT-Konzentrationen wurde untersucht. Potentiodynamische Polarisation und elektrochemische Methoden nachTafel zeigen, daß Verbindungen vom TypAT gute Korrosionsinhibitoren für Kupfer gegenüber HNO3 sind. Die kinetischen und thermodynamischen Parameter des inhibierten Systems wurden bestimmt. Die hohe inhibitorische Wirksamkeit der untersuchten Verbindungen kann auf die Adsorption des Additivs selbst oder auf jene des Cu(II)-AT-Komplexes an der polarisierten Elektrodenoberfläche zurückzuführen sein. Kathodenpolarisationsmessungen zeigen, daßAT-Farbstoffe vorwiegend kationische Inhibitoren sind.

Electrochemical determination of muscle relaxant drug tetrazepam in bulk form, pharmaceutical formulation, and human serum

Tetrazepam dissolved in the Britton-Robinson universal buffer of various pH values (2.5–11.5) containing 10 vol. % of ethanol was reduced at the mercury electrode in a single 2-electron irreversible step due to reduction of the 4,5 C=N double bond of the seven-membered ring. Differential pulse polarography (DPP) and adsorptive cathodic stripping voltammetry (AdCSV) techniques (Linear sweep LS, differential pulse DP and square-wave SW modes) for quantification of tetrazepam in bulk form and in myolastan tablets are presented. Moreover, the described linear sweep, differential pulse, and square-wave adsorptive cathodic stripping voltammetry was successfully applied in quantification of tetrazepam in spiked human serum without any prior extraction of the drug. The obtained results showed an increased sensitivity of the described electro-analytical procedures for the quantification of tetrazepam in the following order DPP, DP-AdCSV, LS-AdCSV, and SW-AdCSV, since the observed limits of tetrazepam quantitation by these electroanalytical techniques were 5 × 10−6 mol L−1, 3 × 10−7 mol L−1, 1 × 10−8 mol L−1, and 3 × 10−9 mol L−1, respectively.

Thermodynamics of Substituted Rhodanine III: Potentiometric and Spectrophotometric Studies of Complexes of Some Transition Metals with 3-Phenylsulfonamidorhodanine

Summary. The dissociation constants of 3-phenylsulfonamidorhodanine (PSR) were determined potentiometrically in 0.1 M KCl and 20% (v/v) ethanol-water. The stepwise stability constants of the complexes of Mn2+, Co2+, Ni2+, Cu2+, Zn2+,La3+, Ce3+, Gd3+, UO2+2, and Th4+ with PSR were determined. The stabilities of the complexes were found as follows: Th4+ > UO2+2 > Gd3+ > Ce3+ > La3+ > Mn2+< Co2+ < Ni2+ < Cu2+ > Zn2+. The thermodynamic parameters for PSR and its complexes were evaluated and discussed. The dissociation process is non-spontaneous, endothermic, and entropically unfavourable. The formation of the complexes was found to be spontaneous, exothermic or endothermic (depending on the metal), and entropically favourable. The stoichiometries of the complexes were determined spectrophotometrically and indicate the formation of 1:1 and 1:2 (metal:ligand) complexes..Zusammenfassung. Die Dissoziationskonstanten von 3-Phenylsulfonamidorhodanin (PSR) in 0.1 M KCl und 60% (v/v) Ethanol-Wasser wurden potentiometrisch ermittelt. Die stufenweisen Stabilitätskonstanten seiner Komplexe mit Mn2+, Co2+ Ni2+, Zn2+, La3+, Ce3+, Gd3+, UO2+ und Th4+ wurden bestimmt. Die Stabilitätsreihenfolge lautet Th4+ > UO2+ > Gd3+ > La3+ > Mn2+ < Co2+< Ni2+ < Cu2+ > Zn2+. Die thermodynamischen Parameter von PSR und seinen Komplexen werden diskutiert. Der Dissoziationsprozeß verläuft nicht-spontan, endotherm und entropisch ungünstig. Die Komplexbildung ist spontan, exo- oder endotherm je nach Metall und entropisch begünstigt. Die Zusammensetzung der Komplexe wurde spektrophotometrisch bestimmt; es entstehen 1:1- und 1:2-Komplexe (Metall:Ligand)..

Supramolecular Assembly on Coordination of Azopolymer Complexes: A Review

This review gives an account of the coordination chemistry of supramolecular azopolymer complexes. The syntheses and structures of azomonomers and their azopolymer complexes were described. Spectral techniques such as (IR, 1H-NMR, ESR) and thermal analysis were investigated. Supramolecular architectures assembled were exhibited through weak interaction including hydrogen bonding and π–π stacking. The spectral data indicate geometry of azopolymer complexes and the orbital reduction factors. ESR spectral data provided information about their structures on the basis of Hamiltonian parameters and degree of covalency. All the azopolymer complexes are ESR active due to the presence of an unpaired electron. The force constant FU–O(mdyn/Å) and the bond length RU–O (Å) of the U–O bond were calculated from the IR data and related to the electronic properties of the substituents. Wilsons method, the matrix method, Badgers formula, and the Jones and El-Sonbati equations were used to calculate the U–O bond distances from the values of the stretching and interaction force constants. The most probable correlations between U–O force constant to U–O bond distance were satisfactorily discussed in terms of Badgers rule, and the Jones and El-Sonbati equations. The thermal stability was investigated using thermogravimetric analysis. The results showed that the azopolymer complexes are mostly more stable than the homopolymer. The stability of the proton ligand/metal ligand constants in the monomeric and polymeric forms was studied carefully using potentiometery. Based on the thermodynamic functions, the dissociation process is nonspontaneous, endothermic and entropically unfavorable. The metal complexes that were formed exhibited spontaneous, endothermic and entropically favorable behavior. GRAPHICAL ABSTRACT

Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature.

Thermodynamics of Substituted Rhodanine IV: Potentiometric Studies of 3-(P-Tolylsulphonamido)Rhodanine Transition Metal Complexes

Abstract Proton-ligand dissociation and metal-ligand stability constants of 3-(p-Tolylsulphonamido)rhodanine (TSR) with some transition metal ions were calculated potentiometrically in 0.1 M KC1 and 20% (v/v) ethanol-water mixture. The order of stability constants was found to be: Th4+>UO2+ 2>Gd3+>Ce3+>La3+>Mn2+ Zn2+ The dissociation constants pKH of TSR and the stability constants log K of their complexes were determined at different temperatures (303, 308 and 318 K). The corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the metal complexes have been found to be spontaneous, exothermic or endothermic (depend on the metal) and entropically favourable. The stoichiometries of these complexes were determined spectrophotometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes.

Electrochemical investigation of N,N′-Propylene-bis-(salicylideneiminato) Mn(III) in phosphate buffer solutions

SummaryAn electrochemical study on N,N′-Propylene-bis-(salicylideneiminato) Mn(III) was performed using cyclic voltammetry with convolution-deconvolution and digital simulation in phosphate buffer solutions ofpH values ranging from 5–9.5 at a hanging mercury drop electrode (HMDE). The reduction pathway of the investigated complex shows that a moderately fast transfer of one electron is followed by a very fast chemical reaction (EqCirr scheme). The electrochemical parameters have been determined experimentally andvia digital simulation experiments.ZusammenfassungN,N′-Propylen-bis-(salicylideniminato)-Mn(III) wurde in Phosphatpufferlösungen mitpH-Werten im Bereich von 5–9.5 an einer Quecksilbertrofelektrode (HMDE) mittels cyclischer Voltammetrie (Konvolution-Dekonvolution, digitale Simulation) elektrochemisch untersucht. Ein mäßig schneller Transfer eines Elektrons wird von einer sehr schnellen chemischen Reaktion gefolgt (EqCirr-Schema). Die elektrochemischen Parameter wurden experimentell und durch Simulations-experimente bestimmt.

Electroreduction of phenol red, chlorophenol red and bromophenol red in buffer solutions at DME

The polarographic reduction of phenol red, chlorophenol red and bromophenol red has been investigated in buffered aqueous solutions and alcohol-water water mixtures over a widepH range (2–12). The results show that the three depolarizers are reduced through two irreversible one-electron waves of equal heights at allpH values. The two waves represent the reduction of the triphenylmethane carbon centre. The nature of the waves and the kinetics of the electrode reaction are discussed.ZusammenfassungDie polarographischen Reduktionen wurden in gepufferten wäßrigen Lösungen und in Alkohol—Wasser-Mischungen über einen weitenpH-Bereich (2–12) durchgeführt. Es zeigte sich, daß in allen drei Fällen die Reduktion über zwei irreversible Ein-Elektron-Wellen gleicher Höhen bei allenpH-Werten vor sich ging. Die Kinetik der Elektrodenreaktion wird diskutiert.

A mechanistic electrochemical study ofbis-(azaferrocene-15-crown-5-ether) at a glassy carbon electrode

SummaryThe work described in this paper concerns the electrochemical behaviour ofbis-(azaferrocene-15-crown-5-ether) at a glassy carbon electrode using CV, CA, and CP techniques. On sweeping to positive direction, a one electron quasi-reversible oxidation wave coupled with a following chemical reaction is observed. Values of the chemical rate constantkc, the rate constant of heterogeneous electron transferk0, the half-wave potentialE1/2, the transfer coefficient α, and the diffusion coefficientD of the depolarizer species are determined and discussed.ZusammenfassungDie vorliegende Arbeit beschäftigt sich mit dem elektrochemischen Verhalten vonbis-(Azaferrocen-15-Krone-5-Ether) an einer Glaskohlenstoffelektrode; die Untersuchungen wurden mittels CV-, CA- und CP-Techniken durchgeführt. Bei einem sweep in positiver Richtung beobachtet man eine quasi-reversible Einelektronen-Oxidationswelle, gekoppelt mit einer darauffolgenden chemischen Reaktion. Die folgenden Parameter wurden bestimmt: Geschwindigkeitskonstante der chemischen Reaktion (kc), Geschwindigkeitskonstante des heterogenen Elektronentransfers (k0), Halbwellenpotential (E1/2), Transferkoeffizient (α) und Diffusionskoeffizient (D).