<i>N</i>-Acetyl Indole Linked to a Fused Triazolo/Thiadiazole Scaffold: Synthesis, Single Crystal X-Ray Structure, and Molecular Insight

Abstract

The designed target compound of N-acetyl indole linked to a fused triazolo/thiadiazole scaffold was synthesized via the reaction of 4-amino-5-(1H-indol-2-yl)-1,2,4-triazol-3(2H)-thione as the starting material with acetic anhydride under reflux conditions for 6 h, resulting in an excellent and pure chemical yield. The structural features of the designed compound were confirmed using spectroscopic tools including single crystal X-ray diffraction analysis along with 1H-NMR, 13C-NMR, 2D-NMR, and high resolution mass spectrometry. Using Hirshfeld analysis, we determined the molecular packing depends on strong interactions (O···H and N···H) along with weak interactions (S···H, C···H and H···H). The shortest contacts corresponding to the N3···H12 (2.490 Å), N2···H5 (2.503 Å), and O1···H2 (2.490 Å) interactions were confirmed based on the Hirshfeld analysis. The calculated dipole moment was 6.6557 Debye. The atomic charge distribution, molecular electrostatic potential map, and reactivity descriptors are also discussed. The computed NMR spectra of the requisite compound correlated well with the results obtained experimentally. The UV-Vis electronic spectra of the requisite compound were simulated using the TD-DFT method and compared with the experimental data. The different σ→σ*, π→π*, n→σ*, and n→π* donor–acceptor interactions and their interaction energies stabilized the studied system to 9.84, 20.65, 29.33, and 45.82 kcal/mol, respectively.

Keywords

• indole
• 4-amino-1,2,4-triazole-3-thiones
• DFT
• Hirshfeld analysis