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Spectroscopic, Cyclic Voltammetry, Thermal and Biological Activity Studies of Co(II), Ni(II) and Cu(II) Complexes of Novel Azo Dyes Derived from Thiadiazole Compounds

Rageh M. N., Fouad D. M., Khafagi Z. A., El-Gahami M. A.

Polish Journal of Chemistry

2007

Vol. 81, nr 10

1785-1793

Novel complexes obtained by reaction of [5-phenyl[1,3,4]thiadiazol-2-yl]azo-4- resorcinol (L1) and [5-phenyl[1,3,4]thiadiazol-2-yl]azo- -naphthol (L2) with Co(II), Ni(II) and Cu(II) have been synthesized and characterized by elemental analysis, molar conductance, electronic, IR and TGA studies as well as cyclic voltammetry. These complexes have the general formula [M(L)Cl22H2O]nH2O and [M(L)2Cl2]nH2O whereM= Cu(II), Ni(II), or Co(II) and L = L1 or L2. It was found that the free ligands are neutral bidentate ON donors of carbonyl and azo groups. The stoichiometry of these complexes is M:L= 1:1 and 1:2. TG studies of these complexes showed that thermal degradation proceeds in two steps. Octahedral geometry is proposed for the divalent metal complexes, cyclic voltammetry reveals a reversibility of the CuII/CuI couple, while for the CoII and NiII complexes there was no reaction. It is observed that the chelates formed are more potent as antimicrobial agents than the free ligands. The stability constants of these complexes determined by spectroscopy methods change in the following sequence: Co(II) < Ni(II) < Cu(II).

Dinuclear polypyridine complexes of 2,4,6-tris(2-pyridyl)-1,3,5-triazine: mixed ligand Ni(II), Co(II) and Cu(II) complexes containing dithiooxamide and thiosemicarbazide

Ibrahim S. A., Hammam A. M., El-Gahami M. A., Fouad D. M.

Bulletin of the Polish Academy of Sciences. Chemistry

2003

Vol. 51, No. 2

93-103

A series of novel dinuclear mixed-ligand complexes having the general formula [M(2)(tpt)(L)(4]Cl(4)nH(2)O where M = Ni(II), Co(II) or Cu(II); tpt = 2,4,6-tris(2-pyridyl)-l,3,5-triazine; L = dithiooxamide (dto) or thiosemicarbazide (tsc); n = 2 — 4, have been synthesized and characterized. The tpt molecule is flexidentate, where it can behave as di- or tridentate and either mono- or dinucleating ligand. The coordination mode of the tpt to the M(II) apparently occurs through pyridyl and a triazine nitrogen atoms. The binary complexes have the formulas [Co(2)(tpt)Cl4H(2)O].2H(2)O, [Ni(tpt)Cl]Cl.5.5H(2)O and [Cu(tpt)Cl(2)].3H(2)O. All the mixed-ligand complexes are dinuclear with bridging tpt molecule and having an octahedral structure. Binary Co(II) and Cu(II) complexes are probably penta coordinated. The complexes under study were characterized by chemical analysis, spectral, molar conductance and thermal studies.