Facile synthesis, structural elucidation and spectral analysis of pyrrole 4-imidazole derivatives

• Experimental spectroscopic data were compared with the theoretical results.
• The UV–Vis spectra of (3A–3D) show π→π* and n→π* electronic transitions.
• The β0 values for pyrrole-imidazoles indicate suitability for non-linear optical response.

In this work pyrrole 4-imidazole derivatives (3A-3D): benzimidazoles and pyrrole 4-imidazoline have been synthesized by condensation, cyclization and oxidation of ethyl 4-formyl-3,5-dimethyl-1H-pyrrole carboxylate and phenylene diamine derivatives/ethylene diamine. The structure of these biheterocyclic compounds have been derived by elemental and spectroscopic - IR, UV, MS, 1H and 13C NMR analysis as well as theoretical study. The static first hyperpolarizability, β0 values for pyrrole 4-imidazole derivatives, (3A-3D) have been calculated as 10.901 × 10−31, 19.607 × 10−31, 40.323 × 10−31, 5.686 × 10−31 esu, respectively. The gradual increase in β0 value of synthesized pyrrole-benzimidazole derivatives from 3A to 3C is due to addition of acceptors -Cl atom in 3B to –NO2 group in 3C on benzimidazole side. The experimental absorption spectra found to be in UV region and the high β0 values show that the synthesized pyrrole-imidazoles are suitable as non–linear optical (NLO) materials.

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