S. A. El-Gyar

Structure and antimicrobial activity of some new azopyrazolone chelates of Ni(II) and Cu(II) acetates, sulfates, and nitrates.

Four coordinate Ni(II) and Cu(II) chelates formed by reaction of two azopyrazolone derivatives with metal sulfate, acetate, or nitrate are described. It is concluded that the ligands possess tautomeric equilibria and can coordinate to the metal ion as neutral or monobasic bidentates. The so-obtained complexes are characterized by elemental and thermal analyses, IR and electronic spectra, as well as conductivity measurements. A pseudo-tetrahedral polymeric structure is proposed for all the complexes in which the acetate, nitrate, or sulfate is attached to the metal ion in the bridging bidentate mode. It is observed that the chelates formed are more potent as antimicrobial agents than the free ligands.

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.

Synthesis and Structure of a New Series Fe(III) and Co(II) Chelates of Some Polyfunctional N-Naphthylideneamino Acids

Abstract Iron(III) and Co(II) complexes of the Schiff bases derived from 2-hydroxy-1-naphthaldehyde and a series of amino acids were prepared. The structure of the complexes is investigated by chemical microanalysis, conductance measurements as well as electronic and infrared spectra. It is concluded that the naphthylideneamino acid coordinates to the metal ion as a bivalent tridentate ligand. Octahedral and square planar structures have been suggested for Fe(III) and Co(II) complexes, respectively.

MEDIUM EFFECTS ON THE ACID DISSOCIATION CONSTANTS OF SOME DIIMINE HETEROCYCLIC BASES

The acid dissociation constants of the protonated form of diimine heterocyclic compounds (imidazole, 2-methylimidazole, 2,2′-bipyridyl, and 1,10-phenanthroline) were determinedpH-meterically in aqueous media containing different amounts of organic solvents, viz. amphiprotic (methanol, ethanol), dipolar aportic (DMSO), and low basic aprotic (acetonitrile) at 25±0.1 °C. It was observed that by increasing the amount of alcohol orDMSO in the aqueous medium thepKa, values of the investigated compounds decreased. On the other hand, thepKa values increased as the amount of acetonitrile in the medium was increased. These results are discussed in terms of various solvent characteristics. It is concluded that solvent effects, viz. differences in stabilization of the free base by dispersion forces and of the proton by its interaction with solvent molecules in amphiprotic or dipolar aprotic solvent-aqueous media relative to that in pure aqueous one, as well as the basicity effect of acetonitrile play a vital role in the ionisation equilibria of the investigated compounds.ZusammenfassungDie Säuredissoziationskonstanten der protonierten Formen der heterocyclischen Dimin-Basen Imidazol, 2-Methylimidazol, 2,2′-Bipyridyl und 1,10-Phenanthrolin wurdenpH-metrisch in wäßrigem Medium mit einem Anteil an organischen Lösungsmitteln bei 25±0.1 °C bestimmt. Dabei wurden als amphiprotische Zusätze Methanol und Ethanol, als dipolar aprotisches organisches LösungsmittelDMSO und als aprotisches niederer Basizität Acetonitril ausgewählt. Es wurde beobachtet, daß bei ansteigenden Konzentrationen an Alkohol oderDMSO diepKa-Werte der untersuchten Verbindungen kleiner werden. Andererseits bewirkt Acetonitril ein Ansteigen derpKa-Werte. Die Ergebnisse werden mittels verschiedener Lösungsmittelparameter diskutiert. Lösungsmitteleffekte wie Stabilisierung der freien Base mittels Dispersionskräften, Protonwechselwirkungen in den verschiedenen Lösungsmittelgemischen und Basizitätseffekte des Acetonitril spielen dabei eine entscheidende Rolle.

Coordinatively Unsaturated Cu(II) Chelates of Arylideneanthranilic Acids and Their Reactivity Towards Lewis Bases

Abstract Cu(II) chelates of five arylideneanthranilic acids and their Lewis base adducts are described. Characterisation of the prepared binary and mixed ligand complexes was accomplished by elemental analysis, electronic and IR spectroscopy as well as conductivity measurements. It was found that five coordinate binary Cu(II) chelates are formed with an intermolecular bridging carboxylate group. The binary chelates were reactive towards Lewis bases (imid, α-pic, quin, bipy, phen) forming mixed ligand complexes which assumed a polymeric distorted octahedral structure.

Synthesis and Properties of Zn(II)-Salicylidene Amino Acid Complexes

The synthesis of nine Zn(II) salicylideneamino acid complexes is reported. The structures of the complexes have been investigated by chemical analyses, electronic and infrared spectra, as well as molar conductance measurements. The apparent complex formation constants have been determined.ZusammenfassungEs wird die Synthese von neun Zn(II)-Salicylidenaminosäurekomplexen berichtet. Die Struktur der Komplexe wurde mittels chemischer Analyse, den Elektronen- und IR-Spektren und auch aus Leitfähigkeitsmessungen ermittelt. Die effektiven Komplexbildungskonstanten wurden ebenfalls bestimmt.

Mixed-Ligand Complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 2,2′,2″-Terpyridine and Amino Acids

Abstract A series of new mixed ligand complexes of the ype [M(terpyridine H+) (amino acid)X2]-H20, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), X = Cl or NO3, have been synthesized and characterised by elemental analysis and infrared spectra. It is deduced that the coordination mode of the terpyridine is changed from terdentate in the binary complex to bidentate in the ternary one where the uncoordinated pyridine exists in the protonated form.

Charge transfer molecular complexes of arylidene anthranilic acid derivatives with π-electron acceptors

Abstract X -Benzylidenesanthranilic acid molecular complexes with π-acceptors, tetracyanoethylene, 2,3-dichloro-5,6-dicyano- p -benzoquinone and chloranil, have been studied. The intramolecular hydrogen bonding that exists in such compounds greatly inhibits the transition of the nitrogen azomethine n -electrons. The formation constant values and molar extinction coefficients of the p -dimethyl-aminobenzylidenean-thranilic acid-DDQ CT complexes have been determined in CH 2 Cl 2 , C 2 H 4 Cl 2 and CHCl 3 in the temperature range 10–30°C. Such CT complexes are of strong n -π type.