Vibrational spectra, hydrogen bonding analysis and herbicidal activity study of mefenacet: A DFT approach

Abstract

Abstract The present study aims to provide deeper knowledge of structural, spectroscopic conformational analysis and herbicidal activity of the rice paddy herbicide Mefenacet on monomeric (MM) and dimeric (MD) model. The specific solvent effect of MM with water molecule (MM-H2O) has been investigated at the B3LYP/6-311G (d,p) level in order to observe the hydrogen bonding interaction. The fundamental modes of vibration are addressed by experimental FT-IR (400-4000 cm−1) and FT-Raman (50-3500 cm−1) techniques. The vibrational spectrum is performed with normal coordinate analysis (NCA) and the wavenumbers are scaled by using Wavenumber–Linear Scaling (WLS) method in order to identify the herbicidal active mode of vibration. Additionally, Quantum Theory of Atoms in Molecules (QTAIM) describing the electronic structure of the monomer and dimer molecules by means of various topological parameters to scrutinize the herbicidal active region. Potential energy surface (PES) scanning of MM with eight different dihedral angles has been performed to discover the most stable conformer, which leads to the herbicidal activity. The UV and global reactivity descriptors have also been carried out to check the herbicidal activity. Hirshfeld surface analysis of MD is done to confirm the existence of intermolecular interactions. Docking studies are performed to predict the herbicidal active site. Moreover, the stability of MM has been evaluated via Molecular Dynamic Simulations (MDS).