Synthesis and spectral characterization of nickel(II) and copper(II) complexes with the hexadentate (±)-1,3-pentanediamine-N,N,N′,N′-tetraacetate ligand and its pentadentate derivative: Stereospecific formation and crystal structure of [Mg(H2O)6][Ni(

► Synthesis of Ni(II) and Cu(II) complexes with 1,3-pdta-type ligands. ► Spectroscopic characterization of Ni(II) and Cu(II) complexes with 1,3-pdta-type ligands. ► X-ray structure of the octahedral 1,3-pndta-Ni(II) complex. ► Stereospecific formation of the octahedral Ni(II) complex with 1,3-pndta ligand.