Aminou Mohamadou

Copper, nickel and cobalt complexes with N,N-disubstituted′-benzoyl thioureas

Abstract The complexes of 8 N,N-disubstituted,N′-benzoyl thioureas with copper, nickel and cobalt have been studied. NMR spectra and magnetic measurements have shown square planar NiL 2 and fac CoL 3 compounds. The electrochemical parameters obtained from cyclic voltammetry for the irreversible process copper(II)/copper(I) redox systems are slightly influenced by the different substituents.

Synthesis and characterization of copper, nickel and cobalt complexes with N-disubstituted, N′-ethoxy carbonyl thioureas

Abstract The complexes of N-disubstituted, N′-ethoxy carbonyl thioureas with copper, nickel and cobalt have been synthesized and studied. NMR spectra and magnetic data have shown square-planar NiL 2 and fac- or mer -CoL 3 compounds. The existence of copper(III)/copper(II) and copper(II)/copper(I) redox systems has been chemically and electrochemically proved in solution.

Synthesis of N-morpholine or N,N-diethyl, N′-monosubstituted benzoyl thiourea copper complexes: characterization and electrochemical investigations

Abstract A series of N-morpholine or N,N-diethyl, N′-substituted benzoyl thioureas (R = Cl, Br, OMe or NO 2 in ortho, meta or para position) have been synthesized by condensation of morpholine or diethylamine with substituted benzoyl isothiocyanates. All CuL 2 complexes have been characterized. Cyclic voltammetry has shown that the irreversible process copper(II)/copper(I) redox systems are influenced slightly by the substitution, whereas the quasi-reversible copper(III)/copper(II) redox systems are not.

Copper(II) and nickel(II) complexes of pyridylamido hexadentate ligands: chemical speciation and spectroscopic studies

Abstract Two novel potentially hexadentate ligands, 1,10-(2-bis picolinamide)-4,7-diazadecane (pycdpnen) and 1,8-bis(2-picolinamide)-3,6-dioxaoctane (pycdado) have been synthesised as their hydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Amide groups deprotonation permits the formation of [MLH −1 ] + species in all cases, while only pycdado gives [MLH −2 ] species. The solid complexes of copper and nickel with the neutral and the deprotonated ligands have been synthesised and characterised by IR, UV–Vis and ESR spectroscopy. The amidic groups are coordinated through the oxygen atoms in all solid complexes [ML](ClO 4 ) 2 (M=Cu 2+ and Ni 2+ ). The complexes obtained with the deprotonated forms of the ligands imply the coordination through the nitrogen atoms of the amidic groups.

Extraction of Metal Ions with Task Specific Ionic Liquids: Influence of a Coordinating Anion

Hydrophobic ionic liquids (ILs) were generated by association between a cationic ester derivative of betaine and bis(trifluoromethylsulfonyl)imide (Tf2N−) or dicyanamide (Dca−) anions. Extraction of Cu(II), Ni(II), Pb(II), and Cd(II) from water was performed with these ILs at room temperature. The use of Dca− anion greatly enhances the extraction efficiency of IL phase towards metal ions extraction. The metal could be back-extracted from the ionic liquid phase with aqueous EDTA solutions. The metal extractability of the ionic liquid after the back-extraction is equivalent to that of the fresh mixture showing that ionic liquid can be reused for several extraction and back-extraction cycles.

Synthesis and spectroscopic characterization of copper, nickel and cobalt complexes with N-(N″,N″-disubstituted-aminothiocarbonyl)-N′-substituted benzamidines

Abstract A series of copper(II), nickel(II) and cobalt(III) complexes with N -( N ″, N ″-disubstituted-aminothiocarbonyl)-N′-substitutedbenzamides have been synthesized and characterized. 1 H and 13 C NMR spectra have shown a mer configuration for the CoL 3 compounds. The NiL 2 complexes have a square-planar structure. Electron spin resonance spectra have shown that the presence of a bulky substituent on the nitrogen donor atom generates a large tetrahedral distortion around the copper in CuL 2 compounds. Cyclic voltammetry has revealed irreversible redox waves corresponding to the Cu(III)Cu(II) and Cu(II)Cu(II) couples.

Molecular structure and spectroscopic characterization of cobalt and copper complexes with a hexadentate nitrogen ligand, 1,10-bis(2-pyridylmethyl)-1,4,7,10-tetraazadecane

Abstract The syntheses of the cobalt(III) and copper(II) complexes with the hexadentate nitrogen ligand 1,10-bis(2-pyridylmethyl)-1,4,7,10-tetraazadecane (bpteta) are reported. NMR spectra and X-ray structure determination have shown that these octahedral complexes have a β-cis configuration with pyridine nitrogen atoms mutually cis and trans to amine nitrogen atoms. A large distortion due to the Jahn–Teller effect is observed in the case of the copper(II) compound.

Copper(II) complexes with lactamides: solution and solid state studies

Three functionalized ligands, S(−)-N-(pyridin-2-ylmethyl)lactamide (pml), S(−)-N-(2-dimethylaminoethyl)lactamide (dmael) and S(−)-N-(3-dimethylaminopropyl)lactamide (dmapl), were synthesized by the aminolysis of S(−)-methyl lactate with the corresponding primary amines. Their protonation constants and the stability constants of the chelates formed with copper(II) were determined by potentiometry. In all cases, we detected the formation of CuLH−1+, CuLH−2 and CuLH−3− species (L = free ligand). The copper(II) complexes prepared in the solid state were characterized by IR and UV-visible spectroscopies. The crystal structure of [Cu(pmlH−1)X] (X = Cl, Br) shows that copper(II) is bound to the pyridyl and the deprotonated amidic nitrogen atoms, as well as to the oxygen atom of the hydroxyl group, which leads to a mono-chelated compound. The geometry around Cu2+ is square pyramidal.

Efficient extraction of gold from water by liquid–liquid extraction or precipitation using hydrophobic ionic liquids

Extraction of tetrachloroaurate or tetrabromoaurate anions has been carried out using several ionic liquids bearing trialkyl(2-ethoxy-2-oxoethyl)ammonium (alkyl group = C2H5 [EtGBOEt+], n-C3H7 [PrGBOEt+] or n-C4H9 [BuGBOEt+]) cations and halide (Cl− or Br−), bis(trifluoromethanesulfonyl)imide (Tf2N−) and dicyanamide (Dca−) anions. The removal of gold anionic moieties from water was first studied by mixing aqueous solutions containing gold complexes and water soluble bromide ionic liquids. This led to the formation of a solid precipitate corresponding to a hydrophobic ionic liquid based on a tetrahalogenoaurate anion. Liquid–liquid extraction of anionic gold complexes using hydrophobic ionic liquids was also investigated.

Synthesis and characterization of copper and nickel complexes with N-arylpyrrole-2-aldimines

Abstract A series of 17N-arylpyrrole-2-aldimine ligands has been synthesized by condensation of pyrrole-2-carboxaldehyde and substituted anilines. All CuL2 complexes are square, whereas NiL2 compounds are square, tetrahedral or eventually present a square α tetrahedral equilibrium. Attempts of chemical oxidation have shown the existence of nickel(III) and copper(III) in solution.