The present work includes: 1. Synthesis and characterization of "8-hydroxy-7-quinolinecarboxaldehyde" azo (HL1-HL5), Schiffbases (HL6, H2L7) and azo schiff bases (HL8-HL12) ligands. 2. Synthesis and characterization of the complexes formed from the reaction of these ligands with some transion metals. 3. Determination of the dissociation constants of Schiffbase ligand (HL6) and the stability constants of its complexes at different temperatures. 4. Study of the optical properties of azo quinoline thin films (HL1-HL5). 5. Study of the dielectrical properties of azo ligands (HL1-HL5) and their complexes, Schiff base ligand (HL6) and its complexes. 6. The effect of the ligands as inhibitors for the corrosion of carbon in 2 M HCl solution and determining the corrosion rate by both of chemical and Electrochemical measurements. 7. Study of the antimicrobial activity of the investigated compounds. 8. The ultrastructural effect of azo Schiff base ligand (HL10) on Staphylococcus aureus and Escherichia coli are discussed. 9. Study the effect of Schiff base ligand (H2L7) & its complexes on the red palm weevil Rhynchophorus ferrugineus (Oliv.) and on the stored food weevils Sitophilus granaria.