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Issue 20, 2018
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Triisopropylsilylethynyl-substituted indenofluorenes: carbonyl versus dicyanovinylene functionalization in one-dimensional molecular crystals and solution-processed n-channel OFETs

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Abstract

The design and synthesis of novel electron-deficient and solution-processable polycyclic aromatic hydrocarbons offers great opportunities for the development of low-cost and large-area (opto)electronics. Although (trialkylsilyl)ethynyl (R3Si–C[triple bond, length as m-dash]C–) has emerged as a very popular unit to solubilize organic semiconductors, it has been applied only to a limited class of materials that are mostly substituted on short molecular axes. Herein, two novel solution-processable indenofluorene-based semiconductors, TIPS-IFDK and TIPS-IFDM, bearing (triisopropylsilyl)ethynyl end units at 2,8-positions (long molecular axis substitution) were synthesized, and their single-crystal structures, optoelectronic properties, solution-sheared thin-film morphologies/microstructures, and n-channel field-effect responses were studied. In accordance with the DFT calculations, the HOMO/LUMO energies of the new compounds are found to be −5.77/−3.65 eV and −5.84/−4.18 eV for TIPS-IFDK and TIPS-IFDM, respectively, reflecting the high electron deficiency of the new π-backbones. Both semiconductors exhibit slightly S-shaped molecular frameworks with highly coplanar IFDK/IFDM π-cores, and they form slipped π-stacked one-dimensional (1-D) columnar motifs in the solid state. However, substantial differences in the degree of π–π interactions and stacking distances (4.04 Å vs. 3.47 Å) were observed between TIPS-IFDK and TIPS-IFDM as a result of carbonyl vs. dicyanovinylene functionalization, which results in a three orders of magnitude variation in the charge carrier mobility of the corresponding thin films. Top-contact/bottom-gate OFETs fabricated via solution-shearing TIPS-IFDM yielded one of the best performances in the (trialkylsilyl)ethynyl literature (μe = 0.02 cm2 V−1 s−1, Ion/Ioff = 107–108, and VT ∼ 2 V under ambient atmosphere) for a 1-D polycrystalline semiconductor microstructure. To the best of our knowledge, the molecules presented here are the first examples of n-type semiconductors substituted with (trialkylsilyl)ethynyl groups on their long molecular axes.

Graphical abstract: Triisopropylsilylethynyl-substituted indenofluorenes: carbonyl versus dicyanovinylene functionalization in one-dimensional molecular crystals and solution-processed n-channel OFETs

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Publication details

The article was received on 10 Aug 2018, accepted on 05 Sep 2018 and first published on 06 Sep 2018


Article type: Research Article
DOI: 10.1039/C8QO00856F
Citation: Org. Chem. Front., 2018,5, 2912-2924
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    Triisopropylsilylethynyl-substituted indenofluorenes: carbonyl versus dicyanovinylene functionalization in one-dimensional molecular crystals and solution-processed n-channel OFETs

    R. Ozdemir, S. Park, İ. Deneme, Y. Park, Y. Zorlu, H. A. Alidagi, K. Harmandar, C. Kim and H. Usta, Org. Chem. Front., 2018, 5, 2912
    DOI: 10.1039/C8QO00856F

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