Antimicrobial activities and theoretical studies on the weak interactions formation in two different configuration complexes

The ligand 2-(3-pyrazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide (L) was synthesized, and two transition metal complexes, namely [Cu(L)2]center dot(NO3)2 (1) and [Ni(L)3]center dot(NO3)2 center dot 3CH3OH (2) were prepared through complexation reaction between L and the corresponding metal salt. L and both complexes were characterized by elemental analysis, as well as compared with spectrographic technique for example FT-IR and UV-Vis spectroscopy. X-ray single-crystal diffraction demonstrated that 1 was tetra-coordinated square planar whereas 2 was hexa-coordinated slightly distorted octahedral geometry. Meanwhile, the metal-ligand ratios were 2:1 in 1 whereas 3:1 in 2. Through the superposition of hydrogen bonds and other weak interactions, both complexes formed 1-D chain-like, 2-D layered, and 3-D supramolecular structures. Theoretical investigations explained the optimized geometries of complexes and the electrostatic potential distribution in molecules, and also analyzed the electron transition types of L and both complexes in combination with UV-vis spectroscopy, which provided theoretical support for the experimental conclusions. Electrostatic potential (ESP) was computed for both complexes to predict the reaction positions of electrophilic and nucleophilic assaults. Hirshfeld Surface Analysis quantified interactions in molecules and analyzed the contribution of various weak interactions to stabilize the structure of complexes. Especially, antibacterial experiments displayed compounds had certain antibacterial activities against both Gram-positive and Gram-negative bacterial strains.