Synthesis and Characterization of Transition Metal Complexes Derived from (E)-N-(1-(Pyridine-2-yl)ethylidiene)benzohydrazide (PEBH)

Abstract

Three metal complexes derived from (E)-N-(1-(pyridine-2-yl)ethylidene)benzohydrazide (PEBH) with Cu(II), Co(II), and Ni(II) have been synthesized and characterized using elemental analyses, spectral analyses (infrared [IR], ultraviolet [UV], mass spectroscopy [MS], nuclear magnetic resonance [¹H-NMR]), thermal analyses, conductance, and magnetic measurements. The results showed that 1:1 (M:L) chelates with the general formula [M L Ac]nH₂O have been formed. IR and ¹H-NMR spectra of the ligand (E)-N-(1-(pyridine-2-yl)ethylidene)benzohydrazide (PEBH) showed that the free ligand exists in the keto form, while it binds to the metal ions in the enol form. The difference between ν_as and ν_s stretching vibrations of the acetate group suggests the monodentate nature of this group. Some semiempirical calculations of the vibrational spectra have been done using AM1, PM3, and ZINDO/1 methods to assist in the assignments of the experimental results. The optical band gap (E_g) values of Co, Ni, and Cu were found to be 3.4, 1.45, and 1.20 eV, respectively, arising from direct transitions. These values indicate the semiconductivity nature of these complexes.

Keywords:

• metal complexes
• spectral characterization
• (E)-N-(1-(pyridine-2-yl)ethylidene)benzohydrazide

Notes

*Nitrogen of the new azomethine group; py = pyridine nitrogen.