Experimental and theoretical studies of trinuclear cadmium(II) complex containing pyridine ring: Synthesis, crystallographic, spectroscopic, TD/DFT calculations and Hirshfeld surface analysis

Two three-dimensional supramolecular structures of L and [Cd3L2(CH3OH)4Cl6] complex (L = 2-(6-bromopyridin-2-yl)-4-methyl-1,2-dihydroquinazoline-N3-oxide), were synthesized and characterized by X-ray crystallography and elemental analysis, as well as FT-IR, UV–Vis, and fluorescence spectroscopy. The photoluminescence behavior of the Cd(II) complex was also investigated in different solvents. X-ray diffraction analysis results revealed that the Cd(II) complex was a trinuclear hexa-coordinate structure and made up of two L, three Cd2+ metal central, four methanol and six chlorine ions. In the crystal structures, it was noteworthy that L formed an infinite 1-D chain-like, 2-D square structure, parallelogram 3-D supramolecular skeleton, whereas the Cd(II) complex formed an infinite 1-D chain-like, 2-D ladder-like configuration, and even expanding into 3-D grid-like supramolecular frameworks. Density functional theory (DFT) calculation was used to compute the optimization, molecular frontier orbital energies (HOMO and LUMO). Specifically, owing to the combination of metal orbitals and the ligand, the energy gap of the complex was less than L. Electrostatic potential (ESP) was used to analyze the reaction sites of two compounds. On the basis of optimized geometry, time-dependent DFT (TD-DFT) simulated the electronic transitions rationalized the UV-Vis spectra peaks of L and Cd(II) complex. In addition, some non-covalent interactions were quantified by Hirshfeld surface and analyzed by Interaction region indicator (IRI).