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English:An Air- and Water-Stable B4N4-Heteropentalene Serving as a Host Material for a Phosphorescent OLED 
Japanese: 菓子田 惇輝, 庄子良晃, Y. Ikabata, H. Taka, H. Sakai, 羽曾部 卓, H. Nakai, 福島 孝典.  
English: J. Kashida, Yoshiaki Shoji, Y. Ikabata, H. Taka, H. Sakai, T. Hasobe, H. Nakai, T. Fukushima.  
Language English 
Journal/Book name
English:Angewandte Chemie International Edition 
Volume, Number, Page Vol. 60    Issue 44    Page 23812-23818
Published date Oct. 25, 2021 
Conference name
Conference site
Official URL https://onlinelibrary.wiley.com/doi/10.1002/anie.202110050
DOI https://doi.org/10.1002/anie.202110050
Abstract A B4N4-heteropentalene (see structure) featuring a large HOMO–LUMO gap was synthesized and found to exhibit excellent thermal and chemical stability. The compound has a high T1 energy and can therefore emit short-wavelength phosphorescence comparable to that of benzene. Owing to its photophysical properties, the B4N4-heteropentalene served as a good host material for a phosphorescent organic light-emitting diode. Replacement of the carbon–carbon bonds of antiaromatic compounds with polar boron–nitrogen bonds often provides isoelectronic BN compounds with excellent thermodynamic stability and interesting photophysical properties. By this element-substitution strategy, we synthesized a new B4N4-heteropentalene derivative, 1, which is fully substituted with mesityl groups. Owing to kinetic protection by the sterically bulky substituents, 1 is remarkably stable toward air and even water. Single-crystal X-ray analysis of 1 revealed the bonding characteristics of the B4N4-heteropentalene structure. In a glassy matrix, 1 emitted short-wavelength phosphorescence with an onset at 350 nm, indicating that the triplet energy is substantially high. DFT calculations reasonably explained the ground- and excited-state electronic structures of 1 as well as its emission properties. Motivated by the high-energy triplet state of 1, we used it as a host material to fabricate a phosphorescent organic light-emitting diode with an external quantum efficiency of 15 %.

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