Synthesis, characterization and crystal structure of a glycylglycinate chelate of zinc(II)

The reaction of glycylglycine (H(2)GG) with zinc oxide in a 2:1 ratio in water produced [Zn-2(HGG(1-))(4)(H2O)(2)] in high yield. The compound was characterized by elemental analysis, thermogravimetric analysis/differential scanning calorimetry, and FTIR spectroscopy. In addition, a single crystal structure revealed a binuclear complex with the H(2)GG ligand in two distinct coordination modes. The first coordination mode exhibits each Zn(II) site coordinated to a terminal, bidentate HGG1-via amine nitrogen atoms and the carbonyl amide oxygen atom. The second coordination mode shows a bridging tridentate HGG(1)-linked to one Zn site through the amine nitrogen and the carbonyl amide oxygen, and to the neighbouring Zn site through a carboxylate oxygen donor. In addition, each Zn site bonds to an aqua ligand to complete the six-coordinate coordination sphere. Crystal data: triclinic space group P-1, a = 7.374 angstrom, alpha = 105.57 degrees, b = 10.054 angstrom, beta = 91.084., c = 10.756 angstrom, gamma = 102.676 degrees, V = 746.88 angstrom(3).