title: Stability of transition metal complexes involving three isomeric quinolyl hydrazones.
abstract: The stability constants of three isomeric quinolyl hydrazones; {4,6-(para); 4,7-(meta) and 4,8-MeBHQ(ortho)} towards some bivalent metal ions have been determined in 75% solvent (dioxane, isopropanol, ethanol and methanol)-water by a pH-titrimetry. The insertion of the Me-group in the 8-position decreases the stability of the complexes to a great extent. The complexation of the ortho-derivative is endothermic, whereas that of the para-derivative is exothermic. Using the solvent parameters, the stability constants of the para-derivative towards Co(II), Ni(II) and Cu(II) ions were evaluated in aqueous medium by five different methods. Also, the electronic absorption spectra of the ortho-hydrazone have been studied in solvents of various polarities to investigate the dependence of the band shift (Δύ) on the solvent parameters viz. 1/D, Z, E(T), DN, AN and (α, β, π*). The interaction of the hydrazones with CoCl(2)·6H(2)O afforded an octahedral complex in case of the ortho-hydrazone and square planar complexes in case of the meta- and para-hydrazones.
authors.affiliation: Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt. hsseleem@yahoo.com
authors.forename: H S
authors.initials: HS
authors.lastname: Seleem
authors.forename: M
authors.initials: M
authors.lastname: Mostafa
authors.forename: F I
authors.initials: FI
authors.lastname: Hanafy
mesh_terms: D002614:Chelating Agents / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry; D004583:Electrons; D006835:Hydrazones / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007700:Kinetics; D011804:Quinolines / Q000737:chemistry*; D012997:Solvents; D013696:Temperature; D028561:Transition Elements / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D004146:Dioxanes; D006835:Hydrazones; D011804:Quinolines; D012997:Solvents; D028561:Transition Elements; D014867:Water; C025223:1,4-dioxane