Abstract: In this study, two zinc-based complexes [Zn(4,4'-bipy)(H2O)4]·(4-ABS)2 (1) and [Zn(4,4'-bipy)(H2O)4]·(4-MBS)2 (2) were obtained through solvothermal synthesis with Zn(II) salts using p-aminobenzenesulfonate (4-ABS-) and p-methylbenzenesulfonate (4-MBS-) as the main ligands and 4,4'-bipyridine (4,4'-bipy) as the auxiliary ligand. The complexes were characterized by single-crystal X-ray diffraction (S-XRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), powder X-ray diffraction (P-XRD), and field-emission scanning electron microscopy (SEM). The performance of complexes 1 and 2 in catalyzing the synthesis of 2,3-diphenyl-2,3-dihydroquinazoline-4(1H)-one was investigated, and complex 1 with better catalytic effect was chosen for substrates universality experiments. The experimental results show that high-yield products could be obtained using a small amount of catalyst in short time under solvent-free conditions. This green process was applicable to a variety of raw materials amines/ammonium compounds and aromatic aldehydes with different substituents. In addition, density functional theory (DFT) was used to optimize the structures of complex 1 and the three reactants. Through computational analysis of the frontier molecular orbitals (NBO), the reaction sequence and the core active sites of complex 1 for the three reactants were inferred. The active sites of complex 1 and the reaction sites of the reaction substrates were further predicted in detail by analyzing the electrostatic potential (ESP) of the molecular surface, the average local ionization energy (ALIE) and the Mulliken charges. Finally, the reaction mechanism of multi-site synergistic catalysis of the complexes was explained in combination with DFT.（CCDC: 2171834, 1; 2225758, 2）

Key words: Zinc-based complexes, Crystal structure, 2,3-Dihydroquinazolin-4(1H)-one, Catalytic mechanism, Density functional theory (DFT)