Synthesis, Structural Characterization, Spectroscopic Properties, and Theoretical Investigations of Aminoacridine Derivatives

<p>Synthesis of four N-(heterocyclic)-9-aminoacridine derivatives was investigated. The synthesized compounds, N-thiazolyl-9-aminoacridine (<b>AC1</b>), N-(1,3,4-thiadiazolyl)-9-aminoacridine (<b>AC2</b>), N-(5-methyl-1,3,4-thiadiazolyl)-9-aminoacridine (<b>AC3</b>), and N-(5-phenyl-1,3,4-thiadiazolyl)-9-aminoacridine (<b>AC4</b>) were characterized by FT-IR, <sup>1</sup>H NMR, mass-spectral, and elemental analysis. Amine-imine tautomerism was suggested by density functional theory (DFT) calculations. The optimized structures were obtained using B3LYP/6–311++G(d,p) level of theory. The UV–Vis absorption spectra were measured in various organic solvents. The synthesized compounds <b>AC1–AC4</b> exhibit absorption spectra characteristic of typical donor–acceptor compounds. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) analysis have been used to explain the internal charge transfer (ICT) phenomena within the molecules. Also, simulated UV spectra were calculated using TD-DFT (B3LYP/6–311++G(d,p) and the results were compared with the experimental values.</p>