Synthesis, investigation of biological activities and theoretical studies of a novel hexaaza Schiff base ligand and its Ni(II) complex: X-ray crystal structure of the Ni(II) complex.

[Display omitted] • Synthesized of hexaxaza macroacyclic Schiff base ligand and comlexe. • Characterized the synthesized compounds by elemental analysis, IR, ESI-MS and, NMR spectroscopy and x-ray crystallography of Ni(II) complex. • Investigation of cytotoxicity and antioxidant activities by in vitro. • NBO, HOMO-LUMO studies. A new designed hexaaza Schiff base ligand including the piperazine ring was synthesized by the reaction of 2-(4-(2-aminophenyl)piperazin-1-yl)benzeneamine and pyridine-2-carbaldehyde in a 1:2 ratio and characterized by IR, mass, 13C NMR and 1H NMR spectroscopy. By the direct reaction of the nickel perchlorate with the N 6 ligand (L), in a 1:1 ratio, a novel complex was prepared and characterized by IR and mass spectroscopy as well as by a single crystal x-ray structural analysis, which showed the crystals to be composed of two compounds: [C 28 H 26 N 6 Ni(MeOH)][ClO 4 ] 2 and {[C 28 H 26 N 6 Ni(H 2 O)][ClO 4 ] 2.(H 2 O)} in the ratio 0.85:0.15. In both complexes the nickel is in a distorted octahedral environment coordinated by five nitrogen atoms of the potentially hexadentate ligand with a molecule of MeOH or water occupying the sixth coordination site. The evaluation of anti-cancer activity of the synthesized ligand (L) and the nickel complex was carried out against MCF-7 and AGS cell lines, while the anti-oxidant property was measured using the DPPH method. The binding mode of L to the nickel ion, in the [NiL(MeOH)]2+ cation, was investigated using DFT calculations at the BP86/def2-SVP level of theory. In this super stable complex, the Nickel(II) center adopted a distorted octahedral geometry, while one of the sites was occupied by the methanol as a ligand. The natural bond orbital (NBO) calculations were performed to study the HOMO, LUMO, band gap energies, global descriptors, Wiberg bond indices, atomic charges, polarizabilities as well as charge transfers and related energies. The theoretical and experimental findings are in agreement. [ABSTRACT FROM AUTHOR]