Copper(II) and zinc(II) 5,5-diethylbarbiturate complexes with 2,6-bis(hydroxymethyl)pyridine: syntheses, crystal structures and thermal decomposition behaviors

Cu(II) and Zn(II) 5,5-diethylbarbiturate (barb) complexes with 2,6-bis(hydroxymethyl)pyridine (pydimH2), namely [Cu(H2O)(barb)(pydimH)]⋅H2O and [Zn(barb)2(pydimH2)]⋅2H2O, were synthesized and fully characterized by elemental analysis, UV–Vis, FTIR, NMR and single-crystal X-ray crystallography techniques. Both Cu(II) and Zn(II) ions displayed a distorted square-pyramidal coordination sphere. The pydimH2 ligand was found in the deprotonated form (pydimH–) in the Cu(II) complex. Both neutral pydimH2 and monoanionic pydimH ligands acted as O, N, O tridentate pincer ligands, while barb was N-coordinated via the deprotonated N site. Thermal behavior of both complexes was studied in a dynamic atmosphere of air by differential thermal analysis (DTA) and thermogravimetric analysis (TG) techniques. The thermal decompositions yielded the corresponding metal oxides as a final decomposition product.