Copper(II) Mononuclear Complexes Incorporating Pyridine Derivatives: Synthesis, Structural Characterization, and Unusual X-Band epr Spectra

Two new copper(II) complexes [Cu(L 1 ) 2 (NO 3 )]NO 3 1 and [Cu(L 2 )(H 2 O) 2 ](NO 3 ) 2 2 (L 1 = 2(2-pyridyl)benzimidazole and L 2 = 2-benzoylpyridine) have been prepared and characterized by elemental and spectral (UV–visible, FTIR and epr) techniques. Crystal structures of these complexes were determined using single crystal X-ray diffraction analysis. The low value of magnetic moments 1.75 BM for 1 and 1.73 BM for 2 and unusual X-band epr spectral pattern authenticate the antiferromagnetic behavior of complexes. The single crystal X-ray analysis reveals the development of supramolecular architectures through various non-covalent weak interactions such as CH ⋯ π and lp ⋯ π interactions. In order to see the stability of complexes, density functional theory (DFT) calculations were carried out. From the energy gap (ΔE) of frontier molecular orbitals (various molecular descriptors were also evaluated. In addition, superoxide dismutase SOD) activities of both complexes were also determined. The enhanced SOD activity of 1 is due to loosely bound nitrate ion. Graphical Abstract Two new copper(II) complexes [Cu(L 1 ) 2 (NO 3 )]NO 3 and [Cu(L 2 )(H 2 O) 2 ](NO 3 ) 2 (L 1 = 2(2-pyridyl)benzimidazole and L 2 = 2-benzoylpyridine) have been prepared and characterized by elemental, spectral, and single crystal diffraction techniques