Structural, spectroscopic, theoretical calculation and Hirshfeld surface analyses of 3-D supramolecular dinuclear zinc(II) and copper(II) complexes

Two three-dimensional dinuclear zinc(II) and copper(II) complexes, [Zn2(L2)2(CH3COO)2] (1) and [Cu2(L2)2(NO3)2] (2) (HL2 = 1-(2-{[(E)-2-hydroxy-benzyli-dene]amino}phenyl)ethanone oxime), were synthesized by Zn(II) acetate tetrahydrate or Cu(II) nitrate trihydrate with based ligand HL1 (2-(2-phenoxy)-4-methyl-1,2-quinazoline-N3-oxide, H is the deprotonate hydrogen) originally. HL1 and both complexes were characterized by elemental analyses and spectroscopic methods, as well as were confirmed by single-crystal X-ray crystallography. It was revealed that two complexes had 2:2 ligand-to-metal ratios and 1 was hexa-coordinated whereas 2 was penta-coordinated. In the crystal structures, HL1 showed a chain-like, while complexes showed 2-D network stacking constructions, and both complexes further formed a 3-D supramolecular structure. The frontier molecular orbital energy of all compounds was calculated, and TD-DFT calculations were performed to analyze the electronic transitions of HL1 and both complexes. Additionally, the structural optimization and electronic transitions of the molecules were obtained via DFT calculations, molecular electrostatic potential (ESP), Hirshfeld surface analysis (HSA), and two-dimensional fingerprint (2D-FP), supporting X-ray diffraction results with the existence of the H···H and C/O···H bonds as the main interactions in the crystal lattice. Especially, cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) spectroscopy properties of 2 were further analyzed. In terms of biological applications, all compounds were investigated for antibacterial activity, and the results displayed two complexes had the best antibacterial performance than others.