Six-coordinated nickel(ii) complexes with benzothiadiazole Schiff-base ligands: synthesis, crystal structure, magnetic and HFEPR study

Abstract

Two new nickel(II) complexes, namely Ni(L¹)₂ (1) and Ni(L²)₂·CH₂Cl₂(2) were obtained by reacting nickel(II) acetate tetrahydrate with the benzothiadiazole Schiff base ligands HL¹ = 2-[4-(2,1,3-benzothiadiazole)imino]methyl-phenol or HL² = 2-[(2,1,3-benzothiadiazol-4-ylimino)methyl]-6-methoxyphenol in the presence of Et₃N. The tridentate NNO chelate ligands induce a distorted octahedral environment around the nickel(II) ions. Single crystal X-ray diffraction analysis reveals elongated Ni–N bonds with the nitrogen atom of the benzothiadiazole ring in both complexes. Intermolecular hydrogen bonds and π–π stacking interactions create two-dimensional and three-dimensional supramolecular arrays, respectively, for complexes 1 and 2. Magnetic susceptibility and high-field electron paramagnetic resonance measurements show the presence of significant magnetic anisotropy, with an axial distortion parameter D of −8–−10 cm⁻¹.