Molecular structure, heteronuclear resonance assisted hydrogen bond analysis, chemical reactivity and first hyperpolarizability of a novel ethyl-4-{[(2,4-dinitrophenyl)-hydrazono]-ethyl}-3,5-dimethyl-1H-pyrrole-2-carboxylate: A combined DFT and AIM approa

A new ethyl-4-{[(2,4-dinitrophenyl)-hydrazono]-ethyl}-3,5-dimethyl-1H-pyrrole-2-carboxylate (EDPHEDPC) has been synthesized and characterized by FT-IR, 1H NMR, UV–vis, DART-Mass spectroscopy and elemental analysis. Quantum chemical calculations have been performed by DFT level of theory using B3LYP functional and 6-31G(d,p) as basis set. The 1H NMR chemical shifts are calculated using gauge including atomic orbitals (GIAO) approach in DMSO as solvent. The time dependent density functional theory (TD-DFT) is used to find the various electronic transitions and their nature within molecule. A combined theoretical and experimental wavenumber analysis confirms the existence of dimer. Topological parameters such as electron density (ρBCP), Laplacian of electron density (▿2ρBCP), kinetic electron energy density (GBCP), potential electron density (VBCP) and the total electron energy density (HBCP) at bond critical points (BCP) have been analyzed by Bader's ‘Atoms in molecules’ AIM theory in detail. The intermolecular hydrogen bond energy of dimer is calculated as −12.51 kcal/mol using AIM calculations. AIM ellipticity analysis is carried out to confirm the presence of resonance assisted intra and intermolecular hydrogen bonds in dimer. The calculated thermodynamic parameters show that reaction is exothermic and non-spontaneous at room temperature. The local reactivity descriptors such as Fukui functions (fk+, fk−), local softnesses (sk−, sk+) and electrophilicity indices (ωk+, ωk−) analyses are performed to determine the reactive sites within molecule. Nonlinear optical (NLO) behavior of title compound is investigated by the computed value of first hyperpolarizability (β0).

Graphical abstractA novel ethyl-4-{[(2,4-dinitrophenyl)-hydrazono]-ethyl}-3,5-dimethyl-1H-pyrrole-2-carboxylate (EDPHEDPC) has been synthesized and characterized by different spectroscopic and micro analysis. Quantum chemical calculations have been performed by DFT level of theory using B3LYP functional and 6-31G(d,p) as basis set. A combined theoretical and experimental wavenumber analysis confirms the existence of dimer. Topological parameters such as electron density, Laplacian of electron density, kinetic electron energy density, potential electron density and the total electron energy density at the bond critical points (BCP) have been analyzed by Bader's ‘Atoms in molecules’ AIM theory in detail. The intermolecular hydrogen bond energy of dimer is calculated as −12.5074 kcal/mol using AIM calculations. The calculated thermodynamic parameters show that reaction is exothermic and non-spontaneous at room temperature. The local reactivity descriptor analysis is performed to find the reactive sites within molecule. The computed value of first hyperpolarizability (β0) shows that EDPHEDPC is an attractive molecule in future for nonlinear optical (NLO) applications.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► FT-IR spectrum of EDPHEDPC was recorded and compared with the theoretical results. ► The theoretical calculations were made using DFT/B3LYP/6-31G(d,p) method. ► By using TD-DFT/6-31G method, electronic spectra for title compound have been predicted. ► Chemical reactivity have been explained with the aid of global and local electronic descriptors. ► The computed value of first hyperpolarizability have been also predicted.