Synthesis and characterization of new materials with pyrrole units and their semiconductor behavior
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Synthesis and characterization of new materials with pyrrole units and their semiconductor behavior Olivia Monroy1, Lioudmila Fomina1, Roberto Salcedo1 1
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n. C.U. A. Postal 70-360, Delegación Coyoacán, C.P. 04510. México D.F. México ABSTRACT New organic materials with semiconductor behavior were prepared from diphenyldiacetylene and aromatic amines with withdrawing groups by Reisch-Schulte reaction and characterized by IR, RMN spectroscopy. The obtained materials share the property of having electron withdrawing groups joint to the attached aromatic ring, it seems this feature accounts in large fashion to improve the semiconducting behavior of this kind of substances, this topic was studied by means theoretical calculations and the results are also discussed. The calculations were carried out by means the Gaussian09 software and all the involved species were geometrically optimized. INTRODUCTION Recently, organic materials have started to play an important role in electronic and photonic technologies. Organic semiconductors are very useful because they have electrical properties similar to those of inorganic semiconductors, but manifest the same properties as plastic (low cost, easily processed, flexibility and versatility of chemical synthesis). Extensive research [1, 2], using both experimental and theoretical approaches has been carried out in an attempt to endow a low HOMO/LUMO gap to organic materials. One strategy employed in order to decrease the band gap in organic molecular materials consists of substitution with electron-withdrawing groups [3]. In this work, 2,5-diphenyl-1-(4(trifluoromethyl)phenyl)-1H-pyrrole and 1-(4-nitro-3-(trifluoromethyl)phenyl)-2,5diphenyl-1H-pyrrole were synthesized using a modification of the Reisch-Schulte reaction, as previously described [4, 5] and characterized by IR, RMN spectroscopy and theoretically studied to explain the origin of their semiconducting behavior. EXPERIMENTAL DETAILS Reagents were provided by Aldrich Chemical Company and used as purchased. FTIR spectra were taken, using Nicolet 510p spectrophotometer. NMR 1H and 13C spectra were recorded using a Bruker Avance 400 MHz spectrometer. The chemical shifts are reported in ppm, scaled relative to TMS. Melting points are uncorrected. Synthesis of the monomer compounds Synthesis of the precursor (2) 1, 4-diphenylbuta-1,3-diyne. Copper (I) chloride (0.4g, 4 mmol) and N, N, N´, N´tetramethylethylendiamine (TMEDA), 0.1 mL (0.0775g, 0.666 mmol) were added to the
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solution of phenyl acetylene (2.042 g, 20 mmol) in isopropanol. The mixture was left stirring under an oxygen atmosphere for 3 hours, and the resulting solution added to acidified water. The product was separated by filtration, dried
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