Synthesis, structures and biological properties of nickel(II) phthalates with imidazole and its derivatives

Four new nickel(II) phthalate compounds: mononuclear complexes [Ni(Im)]6(Pht)·H2O (1), [Ni(Pht)(Im)3(H2O)2]·H2O (2) and [Ni(Pht)(2-MeIm)3(H2O)3]·H2O (3), and coordination polymer [Ni(Pht)(4-MeIm)2(H2O)]n (4) (where Pht = dianion of o-phthalic acid, Im = imidazole, 2-MeIm = 2-methylimidazole, 4-MeIm = 4-methylimidazole) have been synthesized. The complexes 1–4 were characterised by elemental analysis, IR data, thermogravimetric, and X-ray diffraction analyses. X-ray analysis shows that the asymmetric unit of 1 consists of [Ni(Im)]62+ cation, Pht2− anion and solvate H2O molecule. The phthalate dianion does not take part in coordination to metal ion. The cations, anions and water molecules are linked via   N–H⋯⋯O and O–H⋯⋯O interactions forming 2D hydrogen-bonded networks. The structures of 2 and 3 are similar to other mononuclear Ni(II) phthalate complexes where Pht2− anions act as monodentate ligands and uncoordinated carboxylate oxygen atoms participate in the formation of hydrogen bonded double-chains. The structure of 4 consists of [Ni(4-MeIm)2(H2O)] building units connected by phthalate ions to form helical chains. The complexes 1–4 were tested for their ability to increase the biosynthesis of enzymes.

Graphical abstractFour new Ni(II) coordination compounds with o-phthalic acid and imidazole ligand and its derivatives such as 2-methylimidazole and 4-methylimidazole were synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography. The structural patterns displayed in 1–4 illustrate the rich binding facilities of carboxylate groups of the o-phthalate ligand and their ability to form extensive hydrogen-bonding interactions and building up supramolecular aggregates.Figure optionsDownload full-size imageDownload as PowerPoint slide