Synthesis, molecular structure, hydrogen-bonding, NBO and chemical reactivity analysis of a novel 1,9-bis(2-cyano-2-ethoxycarbonylvinyl)-5-(4-hydroxyphenyl)-dipyrromethane: A combined experimental and theoretical (DFT and QTAIM) approach

A detailed spectroscopic analysis of a newly synthesized 1,9-bis(2-cyano-2-ethoxycarbonylvinyl)-5-(4-hydroxyphenyl)-dipyrromethane (3) have been carried out using 1H NMR, UV-Visible, FT-IR and Mass spectroscopic techniques. All the quantum chemical calculations (1H NMR, UV-Visible, FT-IR, NBOs, QTAIM) are carried out using DFT level of theory, B3LYP functional and 6-31G(d,p) as basis set. A combined experimental and theoretical vibrational analysis designates the existence of H-bonding between pyrrole NH as proton donor and nitrogen of cyanide as proton acceptor. To investigate the strength and nature of H-bonding, topological parameters at bond critical points (BCPs) are analyzed by Bader's 'Quantum theory of Atoms in molecules' in detail. Global electrophilicity index (ω = 4.5281 eV) shows that title molecule (3) is a strong electrophile. Local reactivity descriptors as Fukui functions (fk+,fk-), local softnesses (sk+,sk-) and electrophilicity indices (ωk+,ωk-) analyses are performed to find out the reactive sites within molecule.