Stereochemistry of New Nitrogen Containing Heterocyclic Aldehyde. VII. Potentiometric, Conductometric and Thermodynamic Studies of Novel Quinoline Azodyes and Their Metal Complexes with Some Transition Metals

A novel series of quinoline azodyes (5-(49-derivatives phenyldiazo)-8-hydroxy-7-quinolinecarboxaldehyde))
(HL1—HL5) has been prepared and characterized by elemental analyses, 1H-NMR and IR spectra. The IR spectral
data indicate that the compounds can exist in two resonance structures. Proton–ligand dissociation constants
of quinoline azodyes and their subsituted derivatives, and metal–ligand stability constants of their complexes
with bivalent (Mn21, Co21, Ni21, Cu21) metal ions have been determined potentiometrically in 0.1M KCl and
40% (v/v) dimethylformamide (DMF)–water mixture. The influence of substituents on the dissociation and stability
constants was examined on the basis of the electron repelling property of the substituent. The order of the
stability constants of the formed complexes was found to be Mn21,Co21,Ni21,Cu21. The effect of temperature
was studied and the corresponding thermodynamic parameters (DG, DH, DS) were derived and discussed. The
stoichiometries of these complexes were determined conductometrically and indicated the formation of 1 : 1 and
1 : 2 (metal : ligand) complexes was indicated.