Synthesis, characterization and semiconducting behavior of N,2,5-trisubstituted pyrroles

Abstract
In this work, N,2,5-trisubstituted pyrroles were synthesized and characterized by IR, UV–Vis and NMR spectroscopies. These materials' electronic and optical properties were then evaluated. Theoretical calculations were carried out by means of the Gaussian09 software and all the involved species were geometrically optimized in order to obtain the theoretic HOMO, LUMO and band gaps. From the HOMO and LUMO calculations, it turns out that monomer 1-(3,5-dinitrophenyl)-2,5-diphenyl-1H-pyrrole could be used as a p-type semiconductor or n-type semiconductor, depending on the substituent. The experimental optical band gaps were obtained by the Tauc and Cody methods and compared to the ones calculated through DFT. The results show that the semiconducting behavior is found in all the monomers and depends on the functional group of the structure, its crystallinity degree, as well as its HOMO and its LUMO energies.