Substituent Effect on Intramolecular Hydrogen Bond and Electronic Structure of E)-2-(1H-Benzo[D]Imidazol-2-Yl)-3-Phenylacrylonitrile Derivatives: QTAIM and NBO Study

In this study the quantitative analysis of delocalization of electrons acceptor and electrons donor substituent lone pairs on (E)-2-(1H-benzo[d]imidazol-2-yl)-3-phenylacrylonitrile structure and its derivatives and the effects of the substituents on the strength of intramolecular hydrogen bond have been investigated. NBO analysis revealed two types of interactions with the lone pair of substituents The stabilization energies of interactions are generally greater than that of interactions. The insertion of -NO2 on the imidazole heterocycle leads to increase of its stabilization energy and induces a greater intramolecular charge transfer in these molecules. The positive values of interaction energies of the substituents -CH3, -N (CH3)2, -OH, -OCH3, -Cl and -Br show that they have electron-donating properties with respect to the title molecule. QTAIM analysis was also used to evaluate the strength and nature of intramolecular interactions. For types of intramolecular interactions have been observed The highest intramolecular interaction energy has been observed in A16 and A6 molecules at BCPs of with an interaction energy of 4.48945 and 4.38873 kcal/mol. Geometrical parameters and QTAIM result showed that these interactions are closed-shell interaction in nature.