Synthesis, Crystal Structures, and Magnetic Studies of Two Six-Coordinate Nickel(II) Complexes with Tripodal Benzimidazole Ligands

Herein, two nickel(II) complexes [Ni(ntb)(chdc)(CH3OH)]⋅CH3OH⋅3.5H2O (1) and [Ni2(ntb)2(btc)(CH3OH)R]⋅Cl⋅4CH3OH⋅H2O (2) (chdc is trans-1,4-cyclohexanedicarboxylate, btc is 1,3,5-benzenetricarboxylate, ntb is tris(2-benzimidazolylmethyl)amine, R = CH3OH/H2O) containing tetradentate poly-benzimidazole ligand have been synthesized and characterized by FT-IR spectroscopy, UV-Vis spectroscopy, elemental analysis, single‑crystal X‑ray diffraction, and magnetic analysis. X-ray crystallographic analysis shows that the Ni(II) ions in 1 and 2 have distorted octahedral geometries with four nitrogen atoms of ntb, one oxygen atom of carboxylate and one oxygen atom of H2O or CH3OH. Complex 1 is mononuclear with trans-1,4-cyclohexanedicarboxylate coordinated by Ni(II) in monodentate bonding fashion, and complex 2 consists of 1,3,5-benzenetricarboxylato-bridged nickel(II) centers in bis(monodentate) bonding mode. Hydrogen bonds and π–π interactions are important in stabilization of the crystal structures. The variable temperature magnetic susceptibilities of complexes 1 and 2 indicate that there are antiferromagnetic interactions.

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