Synthesis, complexation studies and structural characterization of d and f metal ion complexes with 4-chloroquinaldinic acid N-oxide

► Complexes of 4-chloroquinaldinic acid N-oxide with d- and f-metal ions were obtained. ► Structure, coordination and spectroscopic properties of complexes were characterized. ► Stabilization of the structures was revealed by hydrogen bonding and π–π interactions. The behavior of 4-chloroquinaldinic acid N-oxide (4Cl–QNO) towards divalent 3d transition elements and 4f or 5f elements has been investigated. Four coordinate copper(II), six coordinate cobalt(II), manganese(II), zinc(II) and uranyl as well as seven coordinate europium(III) complexes were synthesized and structurally characterized on the basis of spectral (infrared absorption spectra), thermogravimetric and X-ray diffraction studies. Crystals of Zn(II), Co(II) and Mn(II) complexes suitable for single crystal X-ray diffraction were obtained and their structures were reported together with the crystal structure of the 4Cl–QNO ligand. The 4-chloroquinaldinic acid N-oxide ion is bidentate, it coordinates with metal ions through the N–O oxygen and one of the COO− oxygens. Lattice water and methanol are also present in these complexes.