Two mono‐ and dinuclear Bi(III) complexes, Bi(L)2(NO3)2·NO3 (1) and Bi2(L)2Cl8 (2) (L = (2‐(2‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide), were obtained via complexation of L with Bi(III) nitrate pentahydrate and Bi(III) chloride. L and both complexes were characterized by elemental analyses and spectroscopic methods including FT‐IR, UV–Vis, and fluorescence spectroscopy. Specifically, it clearly manifested that both complexes had good fluorescence emission and showed different fluorescence behaviors in diverse solvents. Both Bi(III) complexes were further determined by X‐ray crystallography, and it was found that the ratio of ligand to metal was 2:1 in 1, whereas 2 was 1:1. Their coordination geometric configurations were significantly different, such as octa‐coordinated complex 1 formed an infinite 1‐D chain‐like, funnel‐shaped 2‐D network, and ladder‐like 3‐D supramolecular framework, whereas hexa‐coordinated complex 2 with a binuclear structure exhibited two slightly distorted octahedral geometric structures; meanwhile, symmetric units came into being an infinite 2‐D layer even and meter‐shaped 3‐D supramolecular skeleton. The optimal geometries, frontier molecular orbital energies, and molecular electrostatic potential diagrams of both complexes were calculated using DFT/B3LYP. The electronic distribution of HOMO‐LUMO rationalized the results of UV–Vis spectra with the help of TD‐DFT calculations. Furthermore, all samples demonstrated excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In addition, non‐covalent interactions of complexes and their contributions were quantified with Hirshfeld surfaces using CrystalExplorer17 program. Two 2‐D and 3‐D supramolecular complexes, Bi(L)2(NO3)2NO3 (1) and Bi2(L)2Cl8 (2), were obtained by reaction of L with different metal salts. Both complexes were characterized by X‐ray crystallography, spectroscopic methods such as FT‐IR, UV–Vis, and fluorescence spectroscopy, as well as Hirshfeld surface analysis and DFT studies. The antimicrobial activities of all compounds were also compared.