Investigation of spectroscopic, structural and non-linear optical properties of ethyl 3,5-dimethyl-4-[(benzenesulfonyl)-hydrazonoethyl]-1H-pyrrol-2-carboxylate

This paper describes the synthesis, spectroscopic 1H and 13C NMR, UV–Visible, FT-IR analysis, elemental analysis, structural evaluation and non-linear optical (NLO) properties of newly synthesized compound, ethyl 3,5-dimethyl-4-[(benzenesulfonyl)-hydrazonoethyl]-1H-pyrrol-2-carboxylate using experimental and quantum chemical techniques. FT-IR spectrum, electronic descriptors, molecular electrostatic potential surface (MEPS) and quantum theory of atoms in molecule (QTAIM) have been used to predict the sites and nature of interactions. A combined experimental and theoretical vibrational analysis identified red shifts in vNH and vCO as result of hydrogen bonding confirming formation of the dimer in the solid phase. The binding energy of dimer has been evaluated as 9.72 kcal/mol. The value of Gibbs free energy change (ΔG) shows that dimer formation is thermodynamically spontaneous. At room temperature, the equilibrium constant (Keq) for dimerization reaction is calculated to be 18.91 i.e. Keq ≫ 1 indicating that dimer formation is more favoured in the forward direction and confirms the formation of dimer at room temperature. The first hyperpolarizability (β0) values for monomer and dimer are found to be 8.94 × 10−30, 4.25 × 10−30 esu, respectively. The UV–Visible spectrum study reveals that the compound absorbs in the range of 299–244 nm due to π–π* and charge transfer transition and so being transparent in the entire visible region providing criteria to be exploited for NLO applications.