Assembly structures of 1:2 nickel(II) complex of 5-methylimidazol-4-yl-methylidene-l-phenylalanine and 1:2 nickel(II) complex of its racemic ligand

Two 1:2 nickel(II) complexes, [Ni(HLL-phe)2]·MeOH·3H2O (1) using an optically pure tridentate ligand of 5-methylimidazol-4-yl-methylidene-L-phenylalanine (H2LL-phe) and [Ni(HLDL-phe)2]·6H2O (2) using its racemic ligand (H2LDL-phe) were synthesized and the crystal structures were determined. Both nickel(II) ion is coordinated by (N2O)2 donor atoms from two tridentate ligands and has an octahedral coordination environment. Complex 1 crystallized in an acentrosymmetric monoclinic space group, P21 (No. 4). In the crystal, 1 contains only the l-isomer and forms a homochiral 2D structure through hydrogen bonding between the adjacent complex molecules. In contrast, Complex 2 crystallized into a centrosymmetric monoclinic space group P21/c (No. 14). In the crystal, 2 consists of [Ni(HLd-phe)2] and [Ni(HLl-phe)2] molecule that are related and forms a heterochiral 3D structure via hydrogen bonding through the crystal solvents.