Metal complexes of N′-[2-hydroxy-5-(phenyldiazenyl)-benzylidene] isonicotinohydrazide. Synthesis, spectroscopic characterization and antimicrobial activity

Abstract

A new series of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II), VO(II), UO2(II), Fe(III) and Ru(III) complexes of N′-[2-hydroxy-5-(phenyldiazenyl) benzylidene]isonicotinohydrazide (H 2L) was synthesized and characterized by elemental analysis, 1H-NMR, IR, UV-Vis and ESR spectroscopy, magnetic and thermogravimetric (TG) analyses, and conductivity measurements. The spectral data showed that the ligand behaved as a neutral bidentate (complexes 2, 4-6 and 14), monobasic bidentate (complexes 7 and 9), monobasic tridentate (complexes 3, 8, 10, 11 and 16) or dibasic tridentate (complexes 12, 13 and 15) and was bonded to the metal ions via the carbonyl oxygen atom in the ketonic or enolic form, the azomethine nitrogen atom and/or the deprotonated phenolic hydroxyl oxygen. The ESR spectrum of the solid vanadyl(II) complex 2 showed an axially anisotropic spectrum with eight lines in the low field region and with g ⊥ > g∥ and A∥ ≫ A ⊥ relationships, which are characteristics of a distorted octahedral structure with a dxy ground state. However, the copper(II) complexes 4-6, and the manganese(II) complex 10 showed an isotropic type symmetry, while the copper(II) complexes 3 and 7 showed an axial symmetry type with g∥ > g⊥ > ge, indicating a covalent bond character. The antibacterial and antifungal activities of the ligand and its metal complexes showed low activity compared with the standard drugs (tetracycline for the bacteria and amphotricene B for the fungi).