Synthesis, structure, magnetic properties and biological activity of supramolecular copper(ii) and nickel(ii) complexes with a Schiff base ligand derived from vitamin B₆

Abstract

Three new complexes of Cu(II) and Ni(II), [Cu(II)(H(2)pydmedpt)](2+)·2Cl(-) (1), [Ni(II)(H(2)pydmedpt)](2+)·2Cl(-) (2) and [Ni(II)(pydmedpt)(OH)](-)·K(+) (3) of the Schiff base ligand [H(2)pydmedpt](2+)·2Cl(-) were synthesized by the in situ reaction of pyridoxal (pyd), a vitamer of vitamin B(6), N,N-bis[3-aminopropyl]methylamine (medpt) and copper(II) acetate or nickel(II) acetate, respectively. The molecular structures of 1 and 2 were determined by single crystal X-ray diffraction studies. The structure of 3 in the solid state was inferred by elemental analysis, diffuse reflectance spectrum, variable temperature magnetic moment studies and DFT calculations. The binding of the Schiff base ligand to the metal centers involves two phenolato oxygens, two imine nitrogens and one amine nitrogen. The coordination geometry around Cu in 1 is distorted square pyramidal and that around the Ni atom in 2 is intermediate between square-pyramidal and trigonal-bipyramidal. In the crystals the compounds form supramolecular one dimensional chain structures stabilized by hydrogen bonding and π-π stacking interactions. Variable temperature magnetic moment data of 2 indicate the presence of a momomeric high spin Ni(II) centre in the complex. The solid state diffuse reflectance spectrum, conductance and elemental analysis suggest that 3 is a Ni(II) complex with a tetragonally distorted octahedral field, the sixth position being occupied by the oxygen atom of a hydroxyl group. The variable temperature magnetic moment of 3 indicates the presence of a ferromagnetic dinuclear species (29.2%) along with the major monomeric species, the intra-dimer exchange term J value being 14.3 cm(-1). The competitive binding of 1 and 2 with DNA was studied in the concentration range 40 to 400 μM, the apparent binding constants being K = 2.9 × 10(3) and 6.7 × 10(3) M(-1), respectively. Human Serum Albumin (HSA) binding studies were carried out at concentrations of 800-1000 μM and 400-500 μM for the complexes and HSA, respectively, in PBS buffer at pH 7.4. Complex 1 binds to HSA, while no binding is observed in case of 2, instead, the complex hydrolyses under the experimental conditions used and the resulting Ni(2+) ions bind with HSA.

Cu(II), Ni(II) complexes derived from chiral Schiff-base ligands: Synthesis, characterization, cytotoxicity, protein and DNA–binding properties

“…Copper (II) and nickel (II) complexes are regarded as the most of promising anti-carcinogen to replace the cisplatin, an idea supported by a considerable number of research articles describing the synthesis, DNA binding, and cytotoxic activities of numerous copper (II) complexes [12][13][14][15][16][17]. Certainly, a wide variety of polydentate organic ligands play a pivotal role to determine the properties of complexes [18].…”

Thirty years through vanadium chemistry

“…The compounds prepared are slightly to moderately soluble in water and the order of stability of the complexes formed is pyridoxamine b H 2 pyr 2 en b H 2 pyr 2 an. Pyridoxal and pyridoxamine are forms of Vitamin B 6 and are non-toxic metabolites and this work promoted the start of many other studies involving pyridoxal Schiff base (pyr 2 en) and reduced Schiff base derivatives (pyr 2 an) by several groups including ours [155][156][157][158][159].…”

“…[154] were published, either for the preparation and use of vanadium complexes or of other metal ions. As mentioned Schiff bases and reduced Schiff bases derived from pyridoxal have the advantage of being more compatible with solvents containing water, thus they were proposed either as ligands for the preparation of complexes with potential pharmaceutical use, or for homogeneous or supported catalytic systems to be used with water containing solvents [155][156][157][158][159].…”

Synthesis, crystal structure and antimicrobial activity of a hetero trinuclear manganese(III)-iron(II) complex derived from N,N’-bis(5-methylsalicylidene)-1,2-diaminoethane

“…Schiff bases and their biologically active complexes have been often used as chelating ligands in the coordination chemistry of transition metals as radiopharmaceuticals for cancer targeting, agrochemicals, as model systems for biological macromolecules, as catalysts and as dioxygen carriers [4][5][6][7]. In recent years, metal complexes of Schiff bases have attracted dramatically attention due to their versatile biological activity, such as antifungal, antibacterial and antitumor [8][9][10]. It has been shown that the Schiff base complexes derived from salicylaldehyde and its derivatives with primary amines, bearing the N 2 O, N 2 S, NO 2 or NSO donor sets, have interesting biological activity [11][12][13][14].…”