Synthesis and spectroscopic characterization of copper(II) complexes with the polydentate chelating ligand 4,4′-[1,4-phenylenedi(nitrilo)dipente-2-one

A new series of complexes of 4,4′-[1,4-phenylenenedi(nitilo)]dipenten-2-one, (H2L) with CuX2·nH2O, X = Cl, Br, ClO4, NO3 and OAc; n = 1–6 as well as their ethylenediamine adducts have been synthesized and characterized by different physical techniques. The formulation of the complexes is assumed based on their elemental analysis and the molar conductivity. The products are found to be pH-dependent. The IR data showed that the ligand acts as dibasic tetradentate coordinated to copper(II) ions through the enolato-oxygen and the azomethine nitrogen atoms. Electronic, ESR spectra and room temperature magnetic moments indicate that complexes 1–9 are square planar while complexes 10 and 11 are square based pyramidal. The different electronic spectral and ESR parameters are calculated and used to describe the nature of ligand-metal bonding (σ and π) as well as to estimate the extent of distortion. A macrocyclic containing copper(II) complex, 12 have been isolated by the reaction of Schiff-base with copper(II)-ethylenediamine mixture. The ligand (H2L) is designed as a building block for larger molecules and superamolecular assemblies.