Metal-ion directed synthesis of N2O2 type chelate complexes of Ni(II), Cu(II) and Zn(II): Spectral, thermal and single crystal studies

A set of Ni(II), Cu(II) and Zn(II) complexes of Schiff base have been synthesized by one pot condensation reaction of 2-hydroxy-4-methoxybenzophenone with 1,3-diaminopropane in 1:2:1 molar ratio. They have been characterized by elemental analysis, conductance measurement, thermal analysis (TGA/DTA), FT-IR, 1H-NMR, EPR spectra, ESI–MS and electronic spectral studies. In order to establish the geometry, a single crystal X-ray structure for [Ni(L)] complex was determined. It crystallizes in monoclinic system having unit cell parameters a = 14.015(5) Å, b = 13.391(5) Å, c = 14.931(5) Å and α = 90.000(5)o, β = 112.237(5)o, γ = 90.000(5)o with P 21/c space group. No π–π stacking interaction was obtained in molecular packing diagram. A square-planar geometry has been confirmed for Ni(II) complex. Furthermore, on the basis of elemental analysis, IR, UV–visible and EPR data a square-planar geometry for Cu(II) and a distorted octahedral geometry for the Zn(II) complex has been established. In case of Zn(II) complex NO3- group was found to be coordinated in monodentate fashion. The low molar conductivity values of the complexes measured in chloroform and DMSO suggest their non-ionic nature.

Figure optionsDownload as PowerPoint slideHighlights
► Central metal ion is coordinated with azomethine nitrogen and phenolic oxygen atoms.
► Ni(II) and Cu(II) are square-planar however Zn(II) is octahedral in geometry.
► Exocyclic –OCH3 facilitates deprotonation of phenolic oxygen by resonance.
► Single crystal studies of Ni(II) complex reveal monoclinic crystal system.