Synthetic Aromatic Organic Compounds Bearing 4, 4-Dimethyl-3-Thiosemicarbazide Moiety: Theoretical and Experimental Approach

Abstract

A theoretical and experimental approach for a series of synthetic aromatic organic compounds as salicylaldehyde thiosemicarbazones were prepared from 4,4-dimethyl-3-thiosemicarbazide and substituted salicylaldehydes. The newly synthesized compounds were fully characterized by FT-IR, UV-vis, 1H-NMR, 13C-NMR, CHNS, HRMS, and fluorescence spectroscopy. DFT calculations were performed on the compounds to get a structure-property relationship. Some global reactivity descriptors like chemical potential (μ), electronegativity (χ), hardness (η), and electrophilicity index (ω) were also evaluated using DFT method. Optical nonlinearity response of our novel compounds was also studied which may be significant for the hi-tech NLO applications. These compounds were also evaluated for their antibacterial activities against certain strains of Gram-positive and Gram-negative bacteria. They displayed moderate activity against using bacterial strains. Additionally, inspiring from recent developments to find a potential inhibitor for COVID-19 virus, molecular docking calculations were also performed on studied compounds to see if our novel compounds show affinity for main protease (Mpro) of SARS-CoV-2 (PDB ID: 6LU7). We have found stable docked structures where docked compounds could readily bound to the SARS-CoV-2, which would be lethal to main protease (Mpro). The molecular docking calculations of the present compounds into the protease of SARS-CoV-2 virus revealed the binding energy in the range of −7.86 to 9.92 kcal/mol with inhibition constant values in the range of 1.360–5.820 µM. These binding affinities are reasonably well as compared to recently docking results of anti-SARS-CoV-2 drugs like chloroquine (−6.293 kcal/mol), hydroxychloroquine (−5.573 kcal/mol) and remdesivir (−6.352 kcal/mol) when targeted to the active-site of SARS-CoV-2 main protease (Mpro).