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Two new bipolar host molecules composed of hole‐transporting carbazole and electron‐transporting cyano (CzFCN) or oxadiazole (CzFOxa)‐substituted fluorenes are synthesized and characterized. The non‐conjugated connections, via an sp3‐hybridized carbon, effectively block the electronic interactions between electron‐donating and ‐accepting moieties, giving CzFCN and CzFOxa bipolar charge transport features with balanced mobilities (10−5 to 10−6 cm2 V−1 s−1). The meta–meta configuration of the fluorene‐based acceptors allows the bipolar hosts to retain relatively high triplet energies [ET = 2.70 eV (CzFOxa) and 2. 86 eV (CzFCN)], which are sufficiently high for hosting blue phosphor. Using a common device structure – ITO/PEDOT:PSS/DTAF/TCTA/host:10% dopants (from blue to red)/DPPS/LiF/Al – highly efficient electrophosphorescent devices are successfully achieved. CzFCN‐based devices demonstrate better performance characteristics, with maximum ηext of 15.1%, 17.9%, 17.4%, 18%, and 20% for blue (FIrpic), green [(PPy)2Ir(acac)], yellowish‐green [m‐(Tpm)2Ir(acac)], yellow [(Bt)2Ir(acac)], and red [Os(bpftz)2(PPhMe2)2, OS1], respectively. In addition, combining yellowish‐green m‐(Tpm)2Ir(acac) with a blue emitter (FIrpic) and a red emitter (OS1) within a single emitting layer hosted by bipolar CzFCN, three‐color electrophosphorescent WOLEDs with high efficiencies (17.3%, 33.4 cd A−1, 30 lm W −1), high color stability, and high color‐rendering index (CRI) of 89.7 can also be realized.

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A wide variety of tert-butyldimethylsilyl (TBS) ethers as well as tert-butyldiphenylsilyl (TBDPS) ethers 1 can be easily deprotected to the corresponding parent hydroxyl compounds 2 by employing catalytic amounts of acetyl chloride in dry MeOH at 0°C to room temperature in good yields. Some of the major advantages are mild conditions, high efficiency, high selectivity, high yields, easy operation, and also compatibility with other protecting groups. Furthermore, no acetylation nor chlorination takes place under the experimental conditions. 0-5 °C, r.t. AcCl / dry MeOH R 1 = aryl / alkyl / sugar residue / nucleoside R 2 = H / alkyl; P = TBS / TBDPS Downloaded by: Karolinska Institutet. Copyrighted material. LETTER The Cleavage of tert-Butyldimethylsilyl (TBS) 695 Synlett 2003, No. 5, 694-698 ISSN 0936-5214 © Thieme Stuttgart · New York

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