Showing papers on "Schiff base published in 1969"

Five co-ordinate complexes of bivalent iron, cobalt, nickel, copper, and zinc halides with terdentate Schiff base and azo-ligands containing tertiary nitrogen donor atoms

Abstract: The ligands N-(β-N′N′-dimethylaminoethyl)pyridinaldimine (paenMe2), N-(2′-N′N′-dimethylaminophenyl)-pyridinaldimine (paphen–NMe2), N-(2′-N″N″-dimethylaminophenyl)-2-N′N′-dimethylaminobenzylideneimine (Me2N–baphen–NMe2) and 2,2′-bis-(NN-dimethylamino)azobenzene (Me2N–ab–NMe2) form complexes with the chlorides or bromides of bivalent iron, cobalt, nickel, copper, and zinc having the general formula MLX2. The stereochemistry of these complexes has been studied by means of magnetic and spectrophotometric measurements. With the exception of Cu(Me2N–baphen–NMe2)Cl2 and Cu(Me2N–ab–NMe2)Cl2, which attain six-co-ordination through chlorine bridging linkages, all are five-co-ordinate complexes.

Monomeric cobalt-oxygen complexes.

Abstract: Some Schiff base complexes of cobalt(II) form stable cobalt-oxygen species in solution instead of the usual cobalt-oxygen-cobalt bridged complexes. These one-to-one adducts were isolated as crystalline solids and characterized by means of elemental analysis, magnetic properties, and molecular weight determinations.

Five-co-ordinate copper(II) complexes of the quadridentate Schiff-base ligand NN′-bis-(2-pyridylmethylene)ethane-1,2-diamine, and some related ligands

Abstract: Three classes of complexes of copper(II) with the quadridentate Schiff-base ligand (bpe) derived from pyridine-2-carbaldehyde and ethane-1,2-diamine are described: (a) Cu2 bpe X4(where X = Cl, Br, and NCS); (b) Cu bpe X′X″(where X′= X″= ClO4 and Br, and X′= l, X″= ClO4); and (c)[Cu2 bpe3](ClO4)4. Complexes of the first type appear to be polymeric, possibly based on a five-co-ordinate copper(II) stereochemistry. Evidence is given for the existence of the five-co-ordinate cations [Cu bpe X]+(where X = Br, I) in the solid compounds of type (b), and in solution in nitromethane (X = Cl, Br, l). Details are given of a reaction in which the compound Cu bpe (ClO4)2 reacts with alcohol solutions of a tetra-alkylammonium halide or thiocyanate to form five-co-ordinate compounds of the type [Cu(bpe,ROH)X]ClO4(where R = Me, Et; and X = Cl, Br, l, NCS). One molecule of alcohol adds across only one of the Schiff-base CN groups. The rationalisation of this reaction by consideration of the steric requirements of the ligand is supported by a recent X-ray structural determination of one of the crystalline compounds. Compounds of the homologous Schiff-base ligand (bpt) derived from pyridine-2-carbaldehyde and propane-1,3-diamine, Cu bpt (ClO4)2 and [Cu bpt I] ClO4 are also described.

Dioxouraniun(VI) Complexes of Schiff Bases Obtained from Substituted Salicylaldehydes and Alkyl Amines

Abstract: Dioxouranium(VI) complexes have been examined with Schiff bases obtained from substituted salicylaldehydes and alkyl amines. Many new complexes of the type abbreviated as UO2−(NO3)2(X-SAL·R·H)2 have been prepared as orange-red crystals. The notation X denotes H, 5,6-benzo and 3-CH3O, and R represents alkyl groups. Infrared spectra indicate that there is no uncoordinated nitrate ion, and that the nitrate ions are coordinated with the uranium(VI) ion as unidentate ligands in these complexes. It is to be noted that the molecules, and not anions, of the Schiff bases are coordinated with the metal ions, as in many other dioxouranium(VI) complexes.

The Stability of Fused Rings in Metal Chelates. IV. Preparation and Relative Stability of Copper(II) Complexes with Tetradentate Schiff Base Ligands

Abstract: Relative stability of sixteen aldehyde- and the corresponding ketone-Schiff base chelates has been investigated in terms of their decomposing temperature and half-wave potential against the reduction of copper(II) at the dropping mercury electrode. The previous conclusion, established for copper(II) tridentate Schiff base complexes, that Schiff base chelates of aldehydes are generally less stable than those of corresponding ketones has been proved to be valid also for copper(II) tetradentate Schiff base complexes if there is no serious steric hindrance in the Schiff base ligand. As a result of this investigation, six new copper(II) chelates were synthesized and characterized.

Magnetic properties and Mössbauer spectra of some terdentate Schiff-base–iron(III) halide complexes

Abstract: The preparation and magnetic susceptibilities over the temperature range 80–300°K of a series of iron(III) chloro- and bromo-complexes with terdentate Schiff bases are reported. The magnetic data indicate polynuclear structures and have been interpreted by use of the spin–spin exchange theory assuming both binuclear and long linear chain models. The binuclear configuration leads to the best fits of the data in most cases and values of the exchange integral, J, are found to be in the range –7·0 to –10·5 cm.–1. The Mossbauer spectra of several of the complexes have been measured at 298°, 78°, and 4·2 °K and have been compared with those for the related binuclear complex with a quadridentate Schiff base [Fe salen Cl]2. The spectra suggest that some of the complexes might possess a similar binuclear structure whereas others probably contain iron atoms in non-equivalent sites.

Acylated and alkylated derivatives of 2-aminohexahydrobenzo(a)quinolizines

Abstract: ACYLATED AND ALKYLATED DERIVATIVES OF 2-AMINOHEXAHYDROBENZO(A)QUINOLIZINE AND PHARMACOLOGICALLY ACCEPTABLE SALTS THEREOF THAT ARE USEFUL AS ANTIHYPERTENSIVE AGENTS. PREPARED BY REACTING 2-OXO-1,3,4,6,7,11B-HEXAHYDRO-2HBENZO(A)QUINOLIZINE WITH AN AMINE TO FORM A SCHIFF BASE WHICH IS THEN REDUCED. THE AMINE IS ACYLATED OR ALKYLATED WITH A HALIDE OR AN ANHYDRIDE.

2-substituted amino-hexahydrobenzo(a)quinolizines

Abstract: 2-SUBSTITUTED AMINO-HEXAHYDROBENZO(A)QUINOLIZINES AND PHARMACOLOGICALLY ACEPTABEL SALTS THEREOF THAT ARE USEFUL AS ANTI-HYPERTENSIVE AGENTS. PREPARED BY REACTING 2-OXO1,3,4,6,7,11B-HEXAHYDRO -2H -BENZO(A) QUINOLIZINE WITH AN AMINO TO FORM A SCHIFF BASE WHICH IS THEN REDUCED.

Schiff base equilibria. VII. Formation and distribution of N-(β-Hydroxyethyl)salicylideneimine

Abstract: The formation constant and pK of the Schiff base N-(8- hydroxyethyl)salicylideneimine in aqueous solution at 25° have been determined spectrophotometrically to be 5.01 x 103 and 11.4 respectively. These equilibrium constants have been used to account for the distribution of the imine between water and chloroform.

The Molecular and Crystal Structure of Bis(2-hydroxyethylimino-pyruvato)copper(II) Tetrahydrate

Abstract: A new copper(II) chelate of the Schiff base derived from pyruvic acid and ethanolamine has been prepared. The crystal structure of this complex, [Cu(pyv=etham)2]·4H2O, has been determined from three dimensional X-ray diffraction data. The dimensions of monoclinic cell are a=6.50A, b=19.75A, c=7.26A, β=113.0° and Z=2. The space group is P21⁄n. The structure has been refined by three dimensional difference syntheses to R=0.126. It has been disclosed that copper (II) links to the 2-hydroxyethyliminopyruvate anion through the terminal carboxylate group, and the nitrogen of the Schiff base linkage. Having a center of symmetry, the complex molecule is in the trans-configuration and has normal bond distances and angles. The coordination around copper(II) is square planar; the Cu–O and Cu–N distances are 1.92 and 2.00A, respectively. Two additional oxygen atoms of the water molecules at 2.57A complete a distorted octahedron around copper(II). The complex molecules are held together in the crystal by the O–H···O h...

Reactions involving pyridoxal phosphate or pyridoxamine phosphate in the presence of metal ions. Part I. The reaction between pyridoxal phosphate and glutamate in the presence of cupric ions

Abstract: The reaction of pyridoxal phosphate with glutamate in the presence of cupric ions has been studied spectrophotometrically. At 25° and pH 4 the rate of formation of the copper–Schiff-base complex is first-order both in pyridoxal phosphate and in glutamate, but zero order in copper. We conclude that the presence of metal ions does not kinetically catalyse the formation of the Schiff base, but acts as a trap for both the Schiff base and an amino-alcohol intermediate.

Copper Complexes Obtained from the Schiff Base of Quinoline-2-Aldehyde and Aliphatic Diamines

Abstract: Schiff base bis (2— quinolidene)- diamine gives a purple-red complex with copper ions with a λmax at 530 mμ. The optimum pH for production of this complex is approximately 9.5. None of the metallic ions of the analytical groups II and III give rise to red complexes with the above Schiff base. Manganous (Mn2+) and stannous (Sn2+)ions as well as reducing agents such as hydrazine or hydroxylamine exert a catalytic effect on the rate of formation of these copper complexes. The thermal stability of the copper complex formed from the Schiff bases (2-quinoline-aldehyde with NH2-(CH2)n-NH2) is greater for diamine for which n = 4–6 than for n = 2–3.

Inner complexes of transition metals with paramagnetic Schiff bases

Abstract: 1. Schiff bases containing stable iminoxyl radical moieties were prepared, which are capable of forming complexes with various metals. 2. Copper(II) complexes with paramagnetic Schiff bases were synthesized.