Nahed M.H. Salem

Synthesis, characterization and magnetochemical studies of dicopper(II) complexes derived from bis(N-salicylidene)dicarboxylic acid dihydrazides

Two series of dicopper(II) complexes derived from bis(N-salicylidine)dicarboxylic acid dihydrazides (H4L n ) of general formula [Cu2(L n )·xH2O]·yH2O and [Cu2(H2L n )Cl2·xH2O]·yH2O have been synthesized and characterized, where n refers to the number of carbon atoms in the aliphatic spacer between the two N-salicylideneacylhydrazine units. Magnetic susceptibility measurements for neutral dicopper(II) complexes [Cu2(L n )·xH2O]·yH2O indicate significant antiferromagnetic coupling between copper(II) centers. The −2J values obtained from the Bleany–Bowers equation are within the range 121–223 cm−1, suggesting association of the coordinated copper(II) units Cu(ONO) via phenoxy bridges. This leads to a polynuclear structure in which the dimeric units are connected with the aliphatic spacer. From the best-fit values of the mole fraction of paramagnetic uncoupled copper(II) centers (ρ), the degree of association in these polynuclear copper(II) complexes has been estimated. The chloro dicopper(II) complexes [Cu2(H2L n )Cl2·xH2O]·yH2O with n = 0, 2 and 3 also show strong antiferromagnetic exchange coupling (−2J = 215–423 cm−1), suggesting a polynuclear structure in which the copper(II) is in a distorted square-pyramidal environment, bound in the equatorial plane with a monoanionic ONO tridentate acylhydrazone unit and the μ-phenoxy oxygen and the axial site occupied by a chloride. The dicopper(II) complexes with n = 1 and 4 show weak antiferromagnetic exchange coupling (−2J = 16–20 cm−1). In these complexes the chloride ion may occupy the fourth equatorial site while the μ-phenoxy is in the apical position.

Metal complexes derived from hydrazoneoxime ligands: II. Synthesis, electrospray mass spectra and magnetochemical studies of some copper(II) complexes derived from p-substituted aroylhydrazoneoximes

Mono- and binuclear copper(II) complexes derived from substituted aroylhydrazoneoximes of the general formulae [Cu(H2LR)Cl2]·nH2O, [Cu(HLR)Cl], [{Cu(HLR)}2]·2NO3·nH2O and [{Cu(LR)}2]·nH2O have been prepared and characterized, where H2LR, HLR and LR refer, respectively, to the neutral, monoanionic and dianionic ONN tridentate aroylhydrazoneoxime ligands. Electrospray ionization (ESI) mass spectra revealed the formation of tri- and tetranuclear copper(II) complexes in dimethylformamide (DMF) or dimethysulphoxide (DMSO) solutions. The effect of substitution in the aroylhydrazone residue on the degree of deprotonation of the ligand and the energies of d–d transitions of the copper(II) complexes have been studied. Tuning of the antiferromagnetic exchange coupling by different substituents in [{Cu(HLR)}2]·2NO3·nH2O and [{Cu(LR)}2]·nH2O complexes have been discussed.

Metal Complexes Derived from Hydrazoneoxime Ligands: I. Synthesis, Characterization and Magnetochemical Studies of (Acylhydrazoneoxime) Copper(II) Complexes

Reactions of 2-hydroxyimino-1-methylpropylidene (acetyl-) and (benzoylhydrazine) with copper(II) chloride, nitrate and acetate were studied. Three types of copper(II) complexes of general formula [Cu(H2L)Cl2], [{Cu(HL)}2]⋅2NO3⋅nH2O and [{Cu(L)}2], where H2L, HL, and L refer, respectively, to the neutral, monoanionic and dianionic ONN tridentate acylhydrazoneoxime ligands, were isolated and characterized. Variable-temperature magnetic susceptibility measurements for [Cu(H2L)Cl2] suggest Curie-Weiss behavior. Both [{Cu(HL)}2]⋅2NO3⋅nH2O and [{Cu(L)}2] show strong antiferromagnetic exchange coupling with − 2J values of 898-934 and 718-757 cm−1, respectively, indication dimeric structures with oximate bridges.

Synthesis and Magnetic Properties of Copper(II) Complexes Derived from Dihydrazones

A series of new acyldihydrazones, H2Ln, obtained by condensation of ethylpyruvate with oxalic, malonic, succinic, glutaric and adipic dihydrazides, undergoes quantitative hydrolysis of the ‒C(O)OC2H5 group via reactions with copper(II) acetate in alcoholic medium. Dicopper(II) complexes of the general formula [Cu2(L′n) · H2O] · xH2O have been isolated, where L′n refers to the quadruply deprotonated pyruvic acid dihydrazone ligand and n refers to the number of carbon atoms of the aliphatic spacer between the two acylhydrazone units. The isolated complexes were characterized by elemental analyses, infrared spectra, mass spectra, as well as variable temperature magnetic susceptibility measurements. Magnetic susceptibility measurements in the 4.2–298 K range indicate significant antiferromagnetic coupling between copper(II) centers and suggest association of the coordinated copper(II) units Cu(ONO) via oxazine oxygen bridges. This leads to a polymeric structure where the dimeric units are connected together with aliphatic spacer. From the best fit values of the mole fraction of paramagnetic uncoupled copper(II) centers (ρ), the degree of association in these polynuclear copper(II) complexes has been estimated.

Synthesis, characterization and molecular structures of copper(II) and nickel(II) complexes derived from diacetylmonooxime thiosemicarbazone and diacetylmonooxime S-benzyl dithiocarbazonate

The dinuclear Cu(II) and Ni(II) complexes, [{M(Oxsbz)}2], [{M(Oxtsc)}2] (M = Cu or Ni), [{Cu(HOxsbz)}2](NO3)2, and [{Cu(HOxsbz)Cl}2], as well as the mononuclear [Ni(Oxtsc)HIm] and [Ni(Oxtsc)HPyr], where H2Oxsbz and H2Oxtsc refer, respectively, to diacetylmonooxime S-benzyldithiocarbazonate and diacetylmonooxime thiosemicarbazone, have been prepared and characterized by IR, UV–vis and 1H NMR spectral measurements as well as ESI mass spectra. The magnetic properties of [{Cu(Oxsbz)}2], [{Cu(Oxtsc)}2], [{Cu(HOxsbz)}2](NO3)2, and [{Cu(HOxsbz)Cl}2] have also been studied. The single-crystal diffraction studies indicated that in [{Cu(HOsbz)Cl}2], each Cu(II) is in a distorted square pyramidal environment and the Cu(II) centers are connected by chloride bridges. In both [Ni(Oxtsc)HIm] and [Ni(Oxtsc)HPyr], HIm = imidazole and HPyr = pyrazole, Ni(II) is in a distorted square planar environment, bound to the Oxtsc dianion via deprotonated oxime nitrogen, imine nitrogen, and deprotonated thiol sulfur; the fourth coordination site is occupied by the heterocyclic nitrogen.

Metal complexes derived from hydrazoneoxime ligands: V. Spectral and structural studies on diacetylmonoxime n-alkanoylhydrazones and their nickel(II) and copper(II) complexes

A series of diacetylmonoxime n-alkanoylhydrazones (H₂L(n), n=4, 5, 6, 12 and 16) were prepared by the condensation of diacetylmonoxime with the corresponding n-alkanoylhydrazine in ethanol. The X-ray crystal structure of diacetylmonoxime octadecanoyl hydrazone has been solved and its molecular and supramolecular structures have been discussed. Both neutral dinuclear Cu(II) and Ni(II) complexes, [{M(L(n))}₂] (M=Cu, Ni and n=4, 5, 6, 12 and 16) as well as cationic dinuclear Cu(II) complexes, [Cu₂(L(n))(HL(n))]NO₃ (n=12 and 16) have been also prepared and characterized by elemental analyses, FD- and ESI-mass spectra as well as IR, UV-Vis, (1)H NMR, (13)C NMR spectra. Variable temperature magnetic susceptibility measurements for dinuclear Cu(II) complexes have been also discussed.

Synthesis, Characterization and Magnetochemical Studies of Some Copper(II) Complexes Derived from Tetrakis(N-Salicylidene)ethanetetracarboxylic Acid Tetrahydrazide

Copper(II) complexes of a new salicylaldehyde tetrahydrazone, H8L derived from ethanetetracarboxylic acid tetrahydrazide, have been synthesized. Three types of copper(II) complexes Cu4(L).6H2O, Cu4(H4L)(NO3)4.7H2O and Cu4(H4L)Cl4.3H2O have been isolated and characterized by elemental analyses, infrared spectra, ultraviolet-visible spectra, as well as variable temperature magnetic susceptibility measurements. Magnetic susceptibility measurements of Cu4(L).6H2O and Cu4(H4L)(NO3)4.7H2O indicate significant antiferromagnetic coupling between copper(II) centers. The –2J values obtained from the Bleaney–Bowers equation equal 213 and 203 cm−1 suggest association of the coordinated copper(II) units Cu(ONO) via phenolic oxygen bridges. This gives rise to a polynuclear structure in which dimerization of coordinated acylhydrazone residues occurs. The chloro copper(II) complex Cu4(H4L)Cl4.3H2O also shows strong antifer-romagnetic exchange coupling (–2J = 472 cm−1), suggesting a polynuclear structure in which the copper(II) is in a distorted square-pyramidal environment, bound in the equatorial plane with a monomeric ONO tridentate acylhydrazone unit, and the bridged phenoxy oxygen and the axial site occupied by a chloride ion.