Crystallographic, spectroscopic, and antimicrobial activities of nickel(II) and cadmium(II) complexes with N-heterocycle: TD/DFT calculations and Hirshfeld surface analysis

Two 1-D, 2-D, 3-D supramolecular complexes, namely [Ni(L1)2(CH3OH)2](NO3)2 (1) and [Cd(L2)2(NO3)2] (2) with N-heterocycle ligands (L1 = 2-(4-imidazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide, L2 = 2-(2-thia-zolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide), were synthesized by corresponding nitrate and characterized by elemental analysis and spectroscopic methods. X-ray diffraction displayed that both complexes were hexa-coordination geometries and had 2:1 ligand-to-metal ratios. Ni(II) in 1 was coordinated with two L1 and two lattice methanol molecules, counterbalanced by nitrate ions, whereas Cd(II) in 2 by two L2 and nitrate ions. In the crystal structures, 1 based on an infinite 1-D chains to form 2-D wavy-like and 3-D supramolecular self -assembly. Similarly, 2 further developed 2-D and 3-D network structure by several interactions. The electro-chemical behavior of 1 in DMF revealed the electronic effects on redox potential of the groups. Most conspicuously, the investigation of antibacterial activities demonstrated that both complexes had good activity against two selected bacteria strains. Density functional theory (DFT) by B3LYP method was used to obtain optimizations, frontier molecular orbital energies and electrostatic potential (ESP) of both complexes. On the basis of optimized geometries, time-dependent DFT (TD-DFT) recorded the specific electronic transitions in the UV-Vis spectra. In addition, the non-covalent interactions in 1 and 2 were analyzed by Hirshfeld surface analysis (HSA).