Crystal structure, Hirshfeld surface analysis, DFT and mol-ecular docking studies of ethyl...

In the title compound, C₈H₉BrN₂O₂, the C-O-C-C torsion angle between isonicotine and the ethyl group is 180.0 (2)°. Intra-molecular N-H⋯O and C-H⋯O inter-actions consolidate the mol-ecular structure. In the crystal, N-H⋯N inter-action form S(5) zigzag chains along [010]. The most significant contributions to the Hirshfeld surface arise from H⋯H (33.2%), Br⋯H/H⋯Br (20.9%), O⋯H/H⋯O (11.2%), C⋯H/H⋯C (11.1%) and N⋯H/H⋯N (10%) contacts. The topology of the three-dimensional energy frameworks was generated using the B3LYP/6-31 G(d,p) model to calculate the total inter-action energy. The net inter-action energies for the title compound are E _ele = 59.2 kJ mol^-1, E _pol = 15.5 kJ mol^-1, E _dis = 140.3 kJ mol^-1 and E _rep = 107.2 kJ mol^-1 with a total inter-action energy E _tot of 128.8 kJ mol^-1. The mol-ecular structure was optimized by density functional theory (DFT) at the B3LYP/6-311+G(d,p) level and the theoretical and experimentally obtained parameters were compared. The frontier mol-ecular orbitals HOMO and LUMO were generated, giving an energy gap ΔE of 4.0931 eV. The MEP was generated to identify active sites in the mol-ecule and mol-ecular docking studies carried out with the title compound (ligand) and the covid-19 main protease PDB ID: 6LU7, revealing a moderate binding affinity of -5.4 kcal mol^-1.