A comprehensive study of structural, non-covalent interactions and electronic insights into N-aryl substituted thiosemicarbazones via SC-XRD and first-principles DFT approach

Abstract

Abstract Two novel indole-based N-aryl substituted thiosemicarbazones (3a and 3b) have been synthesized by the condensation reaction of 3-acetylindole with respective thiosemicarbazide. The SC-XRD and first-principles DFT approach was then used to comprehensively elucidate the structures of both 3a and 3b after initial spectral analysis. The SC-XRD geometric parameters displayed a reasonable agreement with computed geometric parameters. Hirshfeld surface analysis (HSA) has been employed for counting the non-covalent interactions (NCIs) in the crystalline framework. Entire computational calculations were executed for 3a and 3b at DFT/B3LYP/6-311G(d,p) functional. Further, FMO and UV-Vis spectral calculation are carried out at TD-DFT/B3LYP/6-311G(d,p) functional. The most significant potential transitions were observed in 3a with higher stabilization energy value 22.17 kcal/mol and in 3b with 20.95 kcal/mol stabilization energy, explored by NBO analysis. The calculated energy gaps were determined as 4.07 and 3.897 eV for 3a and 3b, respectively. Global reactivity descriptors including electronegativity, softness, hardness, electron affinity, ionization potential and electrophilicity was estimated with assistance of HOMO and LUMO energies. The possible suitable positions for the nucleophilic or electrophilic attack on the chemical structures of investigated molecules were determined using MEP analysis. The simulated spectral data was found in good agreement with experimental based spectral findings.