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.

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.

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.

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 [MLX 2(H2O)2] and [ML 2 X 2] or [ML 2 X 2]·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.

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 [MLX 2(H2O)2] and [ML 2 X 2] or [ML 2 X 2]·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.

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 [MLX 2(H2O)2] and [ML 2 X 2] or [ML 2 X 2]·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.

Microporous tricobalt tetraoxide, Co3O4, nanoparticles (NPs) clusters have been successfully fabricated using a simple but efficient controlled solution combustion route. Such a synthesis involves combustion reaction of cobalt nitrate with cetyl trimethylammonium bromide (CTAB). The combustion process has been analyzed by simultaneous thermal analysis. The resultant powders were characterized by means of X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and nitrogen adsorption at 196 C. The morphology and specific surface area of the obtained Co3O4 nanoparticles clusters have proved to be strongly dependent on the fuel (F)/oxidizer (O) molar ratio and the calcination temperature. It was found that both the crystallite size and the lattice parameter nanocrystalline Co3O4 increase with increasing the F/O molar ratio as well as the calcination temperature. X-ray diffraction confirmed the formation of CoO phase together with spinel Co3O4 using F/O ratio of 1. The concentration of such phase increases with increasing the F/O ratio. Moreover, when the calcination is applied at 900–1000 C traces of CoO was obtained together with Co3O4 as a major phase.