Spectroscopic and density functional theory (DFT) approach of zwitterionic 4-aminobenzenesulfonic acid for optoelectronic applications

Abstract

In this present study, a coupled experimental and density functional theory (DFT) studies of organic nonlinear optical (NLO) material, 4-aminobenzenesulfonic acid (4AB), is reported. By slow evaporation method the optical quality, single crystals of 4AB were developed under aqueous medium condition. Single-crystal XRD analysis reveals the crystalline nature of 4AB crystal; the 4AB crystal structure is in the orthorhombic system with noncentrosymmetric (NCS), Pca21, space group. The morphology of developed crystal has been indexed and showed a major facet of the crystal as (002). The molecular construction of 4AB has been well established using 13C and 1H NMR spectroscopic studies. FTIR and FT-RAMAN were found out to be the corresponding vibrational modes of 4AB. Linear optical studies of grown crystal allow near-UV cut-off wavelength range at 261 nm with good optical transparency in the visible and near-IR region and exhibited ultraviolet wavelength emission. Thermal analysis revealed a high thermal stability value of 288 °C for 4AB crystal. Moreover, dielectric and photoconductivity investigations were accomplished efficiently and revealed low dielectric constant and positive photoconducting nature, respectively. The molecular structure of 4AB was optimized at the B3LYP/cc-pVTZ basis set using density functional theory (DFT). The intermolecular hydrogen bond (N1–H1···O1) formation was confirmed by the Mulliken atomic charge distribution analysis and molecular electrostatic potential map analysis. Frontier molecular orbitals (FMOs) evidenced the lower energy gap for the 4AB molecule. Besides NLO properties, the dipole moment (µ0), polarizability (α) and first-order hyperpolarizability (β) were measured for the optimized 4AB molecule.