M. R. Mahmoud

Cobalt(II), nickel(II), copper(II), thorium(IV) and uranium(VI) complexes of some heterocyclic Schiff bases derived from hydroxy aromatic aldehydes and 2-aminopyridine

Abstract Co(II), Ni(II), Cu(II), Th(IV) and UO2(II) complexes with Schiff bases derived from 2-aminopyridine with salicylaldehyde L1, p-hydroxybenzaldehyde L2 and vanillin L3 have been prepared. The complexes have been characterized by elemental analysis, UV, visible and IR-spectra as well as conductance measurements. It is concluded that the molecules and not anions of L1 are coordinated to the metal ion as bidentate ligand. The two bonding sites are the central azomethine nitrogen and the aldehydic OH-group. On the other hand, the neutral molecules of L2 are coordinated to the metal ion as monodentate ligand where the nitrogen pyridine ring is the bonding site.

Synthesis, characterization and stability constant determination of l-phenylalanine ternary complexes of cobalt(II), nickel(II), copper(II) with N-heterocyclic aromatic bases and X-ray crystal structure of aqua-1,10-phenanthroline-l-phenylalaninatocopper(II) perchlorate complex

Abstract The ternary l -phenylalanine ( l -phe) complexes of Co II , Ni II and Cu II with heterocyclic bases such as 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen) were prepared and characterized by conventional methods, IR spectroscopy, pH-metric titrations and, for [Cu(OH 2 )(phen)( l -phe)]ClO 4 , the X-ray structure was carried out: copper is in a square-pyramidal arrangement in which the base is formed by two phenanthroline nitrogens, one carboxylic oxygen and the amino nitrogen of an l -phenylalaninate ion; the apical site is occupied by a water molecule. Formation constants of Co II , Ni II and Cu II ternary complexes involving 2,2′-bipyridyl, 1,10-phenanthroline or imidazole and the bidentate l -phenylalanine were determined. The results indicate that the stability of the ternary complexes containing the same metal ion varies with the nature of the primary ligand according to the order 1,10-phenanthroline > 2,2′-bipyridyl > imidazole.

Ni(II) complexes of some polyfunctional n-Naphthylideneamino acids

Abstract A new series of amino acid Schiff base Ni(II) complexes of 2-hydroxy- 1 -naphthaldehyde with glycine, l -alanine, l -valine, l -leucine, dl -isoleucine, dl -norleucine, l -serine and l -aspartic acid has been prepared by constituent combination. The structure of the complexes is investigated by microanalysts, conductance, electronic and IR spectral measurements. It is concluded that the bivalent anions of the Schiff bases coordinated to Ni(II) as a tetradentate ligand (O N O O), in the case of the aspartic acid moiety, or as a tridentate ligand (O N O) in the case of the other amino acid moieties. The structure of the Ni(II) complexes is suggested to be square planar.

Reduction of azo-compounds—I. Polarographic behaviour of some 4-hydroxymonoazo compounds at the dropping mercury electrode

Abstract The polarographic behaviour of some monoazo compounds has been studied in aqueous solutions of varying pH. The reduction current in alkaline media is almost half that of the limiting value in acid solution, indicating a change in the mechanism of reduction. A general mechanism for the reduction process in alkaline and acid media is suggested, which includes a rate-determining step involving one electron. The different kinetic parameters for the electrode reaction support the suggested mechanism. The effect of substituents is clarified.

Molecular Complexes of some N-Aryldithiocarbamates with π-Electron Acceptors

Summary. Solid 1:1 CT complexes formed between some S-alkyl-N-aryldithiocarbamates and π-electron acceptors (2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoethylene (TCNE), chloranil (CHL)) are synthesized and characterized. Spectral characteristics and stability of the complexes are investigated and discussed in terms of donor molecular structure, π-acceptor electron affinity, and solvent polarity. It is deduced that the complexes are mainly of the n-π type where the ground state wave function can be described primarily by the non-bonding structure. Ionization potentials of the donors are estimated from the CT transition energies of their complexes.Zusammenfassung. Charge-transfer-Komplexe aus S-Alkyl-N-aryldithiocarbamaten und π-Elektronenakzeptoren (2,3-Dichlor-5,6-dicyano-1,4-benzochinon (DDQ), Tetracyanoethylen (TCNE) und Chloranil (CHL); stöchiometrisches Verhältnis: 1:1) wurden hergestellt und charakterisiert. Die spektroskopischen Eigenschaften und die Stabilitäten der Verbindungen wurden untersucht und werden im Zusammenhang mit Parametern wie Struktur, π-Elektronenakzeptoraffinität und Lösungsmittelpolarität diskutiert. Es zeigt sich, daß die Komplexe hauptsächlich dem n-π-Typ angehören, in dem die Wellenfunktion des Grundzustands vorwiegend durch eine nichtbindende Struktur beschrieben werden kann. Die Ionisationspotentiale der Donatoren werden aus den charge-transfer-Übergangsenergien ihrer Komplexe abgeschätzt.

Kinetics of hydrolysis of some new heterocyclic azomethines

Kinetics of base hydrolysis of new heterocyclic azomethines derived from active methyl quaternary salts and aromatic nitroso compounds were investigated in the presence of 70% (wt/wt) water-methanol. The base hydrolysis of these compounds is strictly first-order with respect to OH− and azomethine. The rate determining step is suggested to be the attack of the hydroxide ion on the free base. Effects of water content and nature of organic hydroxylic solvent have been studied. It is concluded that specific solute-solvent interactions through dispersion forces play a major role in the base hydrolysis rate of the azomethines investigated. The effect of pH (2.98 – 12.24) on hydrolysis rates of compounds having a diethylamino substituent in the presence of 30% methanol has been studied. In acidic media, the rate determining step is probably the water attack on the protonated substrate.

Ternary complexes of N-(2-acetamido)iminodiacetic acid and some aromatic acids. Isolation and stability constants in solution

SummaryTernary 1:1:1 complexes of YIII, CoII, NiII, CuII, LaIII, CeIII and UO22+with N-(2-acetamido)iminodiacetic acid (H2ADA) as primary ligand and salicylic, anthranilic or phthalic acid as secondary ligand are described. The complexes of CoII and CuII were isolated and characterized by microanalysis, molar conductance measurements, thermal analysis, i.r. and u.v.-vis. spectra. The formation constants of the 1∶1∶1 ternary complexes were determined potentiometrically in 20% (w/w) EtOH-H2O at 24 °C. The stabilities of the 1∶1∶1 Mn+:ADA2−:aromatic acid ternary complexes are higher than those of the corresponding 1∶1 Mn+:aromatic acid binary complexes.

Coordination compounds of heterocyclic azo derivatives. III. Co(II), Ni(II) and Cu(II) complexes of some arylazo-4,5-diphenylimidazole derivatives

The 3d transition metalion [Co(II), Ni(II) and Cu(II)] complexes of some 4,5-diphenylimidazole azo derivatives have been isolated and characterized by chemical analysis, conductance, electronic and IR spectra. These dyes are characterized by a high tendency towards complex formation with the neutral molecules coordinated to the metal ion as bidentate ligands. The molecular formula of the 1:1 and 1:2 complexes are suggested to be [MLX2(H2O)2] and [ML2X2] or [ML2X2]·2H2O respectively, whereX=Cl− or NO3. the different bands observed in the visible spectra of methanolic solutions of the complexes have been assigned to the possible electronic transition type (L →MCT and d-d). It is suggested that the complexes studied have a distorted octahedral geometry.ZusammenfassungEs wurden einige Komplexe von 4,5-Diphenylimidazol-azo-Derivaten mit den 3 d-Übergangsmetallen Co(II), Ni(II) und Cu(II) isoliert und mittels chemischer Analyse, Leitfähigkeitsmessungen und den Elektronen- bzw. IR-Spektren charakterisiert. Diese Farbstoffe zeigen eine sehr starke Tendenz zur Komplexbildung, wobei die neutralen Moleküle als zweizähnige Liganden an das Metallion koordinieren. Die Formeln für die 1:1- und 1:2-Komplexe werden mit [MLX2(H2O)2] und [ML2X2] bzw. [ML2X2]·2H2O vorgeschlagen (X=Cl− oder NO3−). Die verschiedenen Absorptionsbanden in den VIS-Spektren in methanolischer Lösung werden den möglichen e-Übergängen (L →MCT und d-d) zugeordnet. Für die Komplexe werden verzerrte oktaedrische Geometrien vorgeschlagen.

Charge-transfer molecular complexes of 2-amino-1,3,4-thiadiazoles

Abstract Charge-transfer molecular complexes of 2-amino-5-X-1,3,4-thiadiazole (D) (X = H, I ; = CH 3 , II ; = phenyl, III ) with some π-electron acceptors (A) have been studied in methanol. It is concluded that these complexes are predominantly of the π-π type. Solid 1:1 CT complexes of the donors I – III with π-acceptors DDQ and TCNE have been synthesized and characterized.

Low excitation energy band of 4-hydroxyazobenzene derivatives

Abstract The low excitation energy band appeared in the electronic spectra of some 4-hydroxyazobenzene derivatives is assigned to an electronic transition of the type n—π*. It is concluded that 4-hydroxyazobenzene derivatives exist mainly in the true azo form. On the other hand, the visible spectra of the azo compound; 4-hydroxy-2-carboxyazobenzene is interpreted on the basis that this compound exists in a tautomeric equilibrium of the type azo ⇌ hydrazone, originating from the carboxyl group at the ortho position to the azo one.