Structural, Spectroscopic and DFT Study of C₁₁H₈N₂O₄ as a Potential SARS-CoV-2 M^pro Inhibitor

In this study, the structural, electronic, and spectroscopic properties of the 3-(1,3-benzodioxol-5-yl)-1H-pyrazole-5-carboxylic acid (C11H8N2O4) molecule, which has potential biological activity and optoelectronic properties, were investigated theoretically. All quantum chemical calculations were performed at the B3LYP/6-311G(d,p) basis set level using Density Functional Theory (DFT). Frequency analysis of the optimized geometric structure confirmed that the structure has a stable minimum on the potential energy surface. The calculated energy gap of 3.982 eV, because of Frontier Molecular Orbital (FMO) analysis, revealed the chemical stability and Intramolecular Charge Transfer (ICT) behavior of the molecule. The calculated global reactivity descriptors, including a HOMO-LUMO energy gap of 3.982 eV, chemical hardness of 1.991 eV, softness of 0.502 eV-1, and electrophilicity index of 4.191 eV, indicated that the molecule possesses moderate kinetic stability and strong electrophilic character. The theoretically obtained FT-IR, NMR, and UV-Vis spectra were consistent with the characteristic functional groups of the molecule, and electronic transition properties were detailed. The Molecular Electrostatic Potential (MEP) map was used to determine the sites of electrophilic and nucleophilic attack on the molecule. Additionally, the molecule's inhibitory effect on the SARS-CoV-2 Main Protease (Mpro) was investigated using a Molecular Docking Method. Simulation results showed that the ligand docked at the enzyme's active site (Cys145-His41) with a binding affinity of –4.982 kcal/mol, providing high steric compatibility. The findings suggest that this compound is a promising candidate for both the development of next-generation nonlinear optical (NLO) materials and pharmaceutical drug design.