Synthesis, Characterization, Crystal Structure and Computational Study of Third-Order NLO Properties of Schiff bases

Abstract

The current study involves the synthesis of two azomethine compounds, (E)-2-((6-nitrobenzo[d][1,3]dioxol-5-yl)methylene)amino)phenol (2AP6NO) and (E)-2-((4-ethylbenzylidene)amino)phenol (2AP4ETH), as well as their theoretical investigations. The synthesized azomethine compounds were then characterized by combustion analysis (CHN), FT-IR, NMR (1H and 13C), and single crystal X-ray diffraction (SC-XRD) analysis. The SC-XRD study confirmed the enol tautomeric form of 2AP6NO as well as 2AP4ETH. The strong and comparatively weak intermolecular interactions were elaborated by Hirshfeld surface analysis. For both compounds, intermolecular interaction energies between the pair of molecules, energy framework, and void analysis were calculated to visualize the three-dimensional topology of the crystal packing. Additionally, quantum chemical computations were also utilized to study the optical and nonlinear optical (NLO) response. The molecular geometries were optimized at the M06-2X/6-311G* method and equated to their respective experimental counterparts. The third-order NLO polarizabilities were also calculated at the same level of theory. The calculated average third-order NLO polarizabilities were 62.55×10−36 esu and 55.08×10−36 esu, respectively, predicting the modest behavior of the above compounds when displaying NLO properties.