Crystal Structure of Two Nickel Complexes with m-Aminophenol-N,N,O-Triacetic Acid, the Effect of Temperature in the Synthesis

Two nickel coordination compounds with m-aminophenol-N,N,O-triacetic acid (H3L), [Ni(L)·(H2O)3]2·Ni(H2O)6·4.3H2O (1), and [Ni(L)·H2O]2·Ni(H2O)6 (2), were obtained under similar reaction conditions but at different synthesis temperature. Single crystal X-ray diffraction analysis reveals that both coordination compounds exhibit discrete dimeric entity structures and contain hexaaquanickel cations acting as counter-ions. Unit cell data for (1): triclinic, space group P-1, a = 7.9977(16), b = 10.475(2), c = 12.952(3) A and α = 107.36(3), β = 99.66(3), γ = 96.15(3)°; and for (2): monoclinic, space group P21/c, a = 13.524(3), b = 8.5703(17), c = 13.820(3) A and β = 95.25(3)°. In (1), O–H⋯O hydrogen bonds link the complex anions into a dimeric unit. But in (2), the dimeric unit is generated from two Ni centers bridged by two ligands. Extensive hydrogen bond interactions exist in both coordination compounds, and connect the complex anions, hexaaquanickel cations and/or water molecules, resulting in three-dimensional supramolecular structures. The compounds also have been characterized by elemental analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), FT-IR and UV–Vis spectra. More coordinated water molecules of metal ion are substituted by N and/or O donors of ligand at higher reaction temperature.