Syntheses, crystal structures, fluorescent, and thermal properties of nickel(II) 5,5-diethylbarbiturate complexes with (2-aminomethyl), (2-aminoethyl), and (2-hydroxyethyl)pyridines

Three nickel(II) complexes of 5,5-diethlybarbiturate (barb) with (2-aminomethyl)pyridine (ampy), (2-aminoethyl)pyridine (aepy), and (2-hydroxyethyl)pyridine (hepy), [Ni(barb-N)2(ampy)2] (1), [Ni(barb-N,O)(aepy)2](barb) center dot H2O (2), and [Ni(barb-O)2(hepy)] center dot 2H2O (3), have been synthesized and characterized by elemental analysis, IR, thermal analysis, and single crystal X-ray diffraction. All complexes are mononuclear with nickel(II) exhibiting an octahedral coordination. Ampy, aepy, and hepy are bidentate chelating ligands, while barb shows different coordination modes. In 1, two barb ligands are N-bonded, whereas in 3 they are O-coordinated through one carbonyl oxygen. In 2, one barb is bidentate chelating, while the second barb remains outside the coordination sphere as a counterion. The molecules of 1-3 are bridged by multiple hydrogen bonds to generate 1-D or 2-D supramolecular networks. All complexes are fluorescent due to -* transitions.