Experimental and DFT study on pyrrole tosylhydrazones

Two pyrrole tosylhydrazones, 1H-pyrrole-2-tosylhydrazone (PT) and ethyl 3,5-dimethyl-4-(1-(2-tosylhydrazono)ethyl)-1H-pyrrole-2-carboxylate (EDTEPC) have been synthesized and characterized by various spectroscopic techniques. All calculations have been performed using B3LYP functional and 6-31G(d,p) basis set. The result of hydrogen bonding is obvious in 1H NMR and FT-IR due to down field chemical shift and vibrational red shift to pyrrole NH proton, respectively. The red shift in both the proton donor (pyrrole NH) and proton acceptor (SO) group designates presence of intermolecular classical hydrogen bonding NH⋯O. The binding energy of dimer formation is calculated as 13.12, 14.12 kcal/mol, after correction in basis set superposition error (BSSE). Topological parameters indicate the weaker interactions presents in the molecules. The global electrophilicity index (ω = 2.54, 2.28 eV) shows that PT and EDTEPC molecules are strong electrophile. The local reactivity descriptors analyses are performed to determine the reactive sites within the PT and EDTEPC. Computed first hyperpolarizability (β0 = 6.50/8.38 × 10−30 esu) of PT and EDTEPC indicates non-linear optical (NLO) response of the molecules.