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Issue 47, 2009
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Intermolecular peripheral 2,5-bipyridyl interactions by cyclization of 1,1′-silanylene unit of 2,3,4,5-aryl substituted siloles: enhanced thermal stability, high charge carrier mobility, and their application to electron transporting layers for OLEDs

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Abstract

Two 2,5-bipyridyl substituted 1,1′-silanylene unit cyclized siloles with 1,1-silacyclopentyl- or 1,1-silacyclohexyl groups (3-Cy5 and 3-Cy6) were prepared from the intramolecular reductive cyclization of silacycloalkyl bis(phenylethynyl)silane with lithium naphthalenide and a a subsequent Pd-catalyzed cross-coupling reaction. Non-cyclized bipyridyl substituted dimethylsilole, 2,5-bis(2′,2′′-dipyridin-6-yl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy), was also synthesized for comparison. All three siloles were characterized by X-ray structural studies. The results showed that the major contribution of three dimensional ordering found in crystal packing originated from distinctive intermolecular C–H⋯π interactions within the distance range 3.30–3.65 Å. Even higher ordering was apparent in the crystal packing due to the additional plane-to-plane packing interactions between the peripheral bipyridyl units in cyclized siloles, 3-Cy5 and 3-Cy6. In accordance with such an increase in the peripheral intermolecular interactions, 3-Cy5 and 3-Cy6 exhibited higher Tg values (95 and 86 °C, respectively) than the acyclic analogue, PyPySPyPy (77 °C). In particular, 3-Cy5 showed a higher electron mobility of 6.9 × 10−4 cm2V−1 s−1 at E = 0.581 MV cm−1 in the solid films. As a result, enhanced OLED performance was observed when 3-Cy5 was used as an electron transporting layer in the multilayered device structure of ITO/PEDOT·PSS/NPB/Alq3/3-Cy5/LiF/Al, showing a maximum luminance of 17430 cd m−2 at 11.5 V and a current efficiency of 4.52 cd A−1 at 69.4 mA cm−2 with a turn-on voltage of 2.6 V.

Graphical abstract: Intermolecular peripheral 2,5-bipyridyl interactions by cyclization of 1,1′-silanylene unit of 2,3,4,5-aryl substituted siloles: enhanced thermal stability, high charge carrier mobility, and their application to electron transporting layers for OLEDs

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Publication details

The article was received on 30 Jul 2009, accepted on 24 Sep 2009 and first published on 22 Oct 2009


Article type: Paper
DOI: 10.1039/B915214H
Citation: J. Mater. Chem., 2009,19, 8964-8973

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    Intermolecular peripheral 2,5-bipyridyl interactions by cyclization of 1,1′-silanylene unit of 2,3,4,5-aryl substituted siloles: enhanced thermal stability, high charge carrier mobility, and their application to electron transporting layers for OLEDs

    H. Son, W. Han, K. R. Wee, S. Lee, A. Hwang, S. Kwon, D. W. Cho, I. Suh and S. O. Kang, J. Mater. Chem., 2009, 19, 8964
    DOI: 10.1039/B915214H

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