Synthesis, spectroscopic and structural evaluation of ethyl 2-cyano-3-{5-[(4-nitro-benzoyl)-hydrazonomethyl]-1H-pyrrol-2-yl}-acrylate using experimental and theoretical approaches

A new C-vinylpyrrole containing aroylhydrazone, ethyl 2-cyano-3-{5-[(4-nitro-benzoyl)-hydrazonomethyl]-1H-pyrrol-2-yl}-acrylate (ECNBHPA) derived from ethyl 2-cyano-3-(5-formyl-1H-pyrrol-2-yl)-acrylate and 4-nitro-benzohydrazide has been characterized by various spectroscopic techniques (1H NMR, 13C NMR, Mass, UV-Visible, Emission, FT-IR). TD-DFT has been used to calculate the various electronic excitations and their nature within molecule. The emission spectra of ECNBHPA show photoluminescent behavior of title molecule. Natural bond orbital (NBO) analysis has been carried out to explore the various conjugative/hyperconjugative interactions within molecule and their second order stabilization energy (E(2)). A combined experimental and theoretical vibrational analysis designates presence of the classical hydrogen bonding N1H29⋯N9 between pyrrole NH as proton donor and N atom of cyanide as proton acceptor. To determine the strength and nature of hydrogen bonding, topological parameters at bond critical points (BCP) have been analyzed by 'Quantum theory of atoms in molecules' (QTAIM) in detail. The result of hydrogen bonding is obvious in 1H NMR, FT-IR and ESP map as down field chemical shift, vibrational red shift and absence of blue colur relative to pyrrole NH proton, respectively. Global electrophilicity index (ω = 6.573 eV) shows that title molecule behaves as a strong electrophile. The local reactivity descriptors analyses such as Fukui functions (fk+,fk-), local softnesses (sk+,sk-) and electrophilicity indices (ωk+,ωk-) have been performed to determine the reactive sites within molecule. The first hyperpolarizability (β0) of ECNBHPA has been computed to evaluate the non-linear optical (NLO) response of the investigated molecule.