Spectroscopic behavior, FMO, NLO and substitution effect of 2-(1H-Benzo [d]imidazole-2-ylthio)-N-o-substituted-acetamides: Experimental and

The benzimidazole-based derivatives 2a-c were designed and synthesized via C-N coupling reaction and experimentally characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance (H-1 NMR) spectroscopy and mass spectrometry (MS). The observed and calculated FT-IR frequencies correspond to C=O stretching of amide group are depicted at 1657, 1672 and 1682, 1689 and 1699, 1682 for 2a, 2b and 2c respectively and are in good agreement. The synthesized compounds 2a-c exhibit non-linear optical response with the first hyperpolarizability (beta(0)) at 783, 1550 and 694 au, respectively. Due to the presence of electron withdrawing -NO2 on the primary amine of 2b, the beta(0) value is estimated at 1550 au, which reduces the energy barrier hence increasing the beta(0) value, with maximum UV-vis absorption at 224 nm with TD-DFT method. The opposite behavior is demonstrated by the electron donor -OCH3 substituent. This study of NLO responses would be beneficial to the development of high-performance NLO materials.