Pesticidal compound Pirimicarb: Spectral analysis, DFT computations, molecular docking study and in vitro bioactivity

Highlights: • Bond lengths of CH (methyl groups) which are shortened due to electron delocalization infer transfer of electrons through sigma bond and pi bond. • Carbon atoms in the pirimidine ring attached to the electron withdrawing nitrogen atom decreases the shielding. • nπ conjugation between the amino nitrogen lone-pair electrons and pirimidine ring π system is strong in the ground state, as indicated by the Py–N wavenumber at 1367 cm⁻¹. This is well reflected in the NBO analysis as the energies of hyperconjugative interactions become strong as 61.64 kJ/mol. • The best binding score of Pirimicarb has been obtained with protein 5LM8 (−6.95 kcal/mol). In structural conformation, lowering of bond angles is due to the charge transfer from pirimidine ring through carbonyl group to the dimethylamino group. Downshift of 24 cm⁻¹ in FT-IR due to the change from the ground state to the intramoleclar charge transfer (ICT) state and Py–N (pyrimidine-nitrogen) wavenumber shift is predicted theoretically. In natural bonds orbital analysis the magnitudes of charges transferred from lone pairs of LP(1)(N7) into the antibonds π∗(N₁-C₆) has stabilization energy 61.64 kJmol⁻¹ due to resonance effect concomitant to red shift of their stretching frequencies. Best binding score of Pirimicarb was obtained with protein 5LM8 (−6.95 kcal/mol).