Stereochemistry of new nitrogen-containing heterocyclic compounds. XV. Potentiometric, thermodynamic and biological activity studies of azoquinolines and their metal complexes

A series of azoquinolines, HL1-HL5, 5-(4-derivatives phenylazo)-8-hydroxy-7-quinoline), has been prepared and characterized by elemental analysis, H-1 NMR and IR spectra. The IR spectral data indicate that the compounds can exist in two resonance structures. Proton-ligand dissociation constants of azoquinoline derivatives, and metal-ligand stability constants of their complexes with bivalent metal ions (Co-2, Ni2+, CU2+ and Zn2+) have been determined potentiometrically in 0.1 M KCI in 40% (v/v) 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 complexes was found to be Co2+ < Ni2+ < Zn2+ < Cu2+. Thermodynamic parameters (DeltaG, DeltaH and DeltaS) were derived and discussed. hi vitro tests of antibacterial activity showed that azoquinoline derivatives and their complexes with Co-2+,Co- Ni-2+,Ni- Cu-2+,Cu- Cd2+ and UO22+ exhibited good inhibitory action against Pseddononas auruginosa, Staphylococus aureus, Bacillus subtilis, Bacillus cereus and E.coli.