The ligational behavior of an isatinic quinolyl hydrazone towards copper(II)- ions

Background: The importance of the isatinic quinolyl hydrazones arises from incorporating the quinoline ring with the indole ring. Quinoline ring has therapeutic and biological activities whereas, the indole ring occurs in Jasmine flowers and Orange blossoms. As a ligand, the isatin moiety is potentially ambidentate and can coordinate the metal ions either through its lactam or lactim forms. In a previous study, the ligational behavior of a phenolic quinolyl hydrazone towards copper(II)- ions has been studied. As continuation of our interest, the present study is planned to check the ligational behavior of an isatinic quinolyl hydrazone. Results: New homo- and heteroleptic copper(II)- complexes were obtained from the reaction of an isatinic quinolyl hydrazone (HL) with several copper(II) salts viz. Cl-, Br-, NO3-, ClO4-, SO42- and AcO-. The obtained complexes have O-h, T-d and D-4h- symmetry and fulfill the strong coordinating ability of Cl-, Br-, NO3- and SO42- anions. Depending on the type of the anion, the ligand coordinates the copper(II)- ions either through its lactam (NO3- and ClO4-) or lactim (the others) forms. Conclusion: The effect of anion for the same metal ion is obvious from either the geometry of the isolated complexes (O-h, T-d and D-4h) or the various modes of bonding. Also, the obtained complexes fulfill the strong coordinating ability of Cl-, Br-, NO3- and SO42- anions in consistency with the donor ability of the anions. In case of copper(II)- acetate, a unique homoleptic complex (5) was obtained in which the AcO- anion acts as a base enough to quantitatively deprotonate the hydrazone. The isatinic hydrazone uses its lactim form in most complexes.