Synthesis, Doping and Characterization of new Molecular Semiconductors Containing (2E, 4Z)-5, 7-diphenylhepta-2, 4-dien-6-ynoic acids

This work refers to the synthesis and characterization of new (2E, 4Z)-5, 7-diphenylhepta-2, 4-dien-6-ynoic acids. We describe the nucleophilic addition of bis(trimethylsylil)ketene acetals (TMS) to aryl ynones substituted by halogen groups activated by boron trifluoride diethyl etherate (BF_3·Et₂O) for the stereoselective synthesis of dienynoic acid. The molecular materials were structurally characterized by IR spectroscopy, NMR spectroscopy and X-ray diffraction. After the characterization the synthesized acids were doped with indium(III) phthalocyanine chloride (In(III)PcCl) in order to generate a organic semiconductor that was characterized by UV–Vis spectroscopy to subsequently obtain their optical bandgap (Eg) values. The Eg value was compared to that obtained for the pure state dienynoic acids in order to evaluate the doping effect with the In(III)PcCl. The Eg diminished from values near 2.6 eV obtained for pure compounds to values around 1.4 eV for the same compounds, but now with doping. With the molecular semiconductors obtained were manufactured structures of disperse heterojunction which later were evaluated in their electric behavior. A behaviour ohmic at low voltages and Space Charge Limited Current (SCLC) at higher voltages was observe from the study J(V) carried out.