Development of Dibenzo[a,j]phenazine-Cored Organic Emitters: Synthesis, Photophysical Modulation, and Optoelectronic and Sensing Applications

 

Date: 13^th November, 2024 (Wednesday)

Time: 5:30 - 6:30 pm (HKT)

Venue: Lecture Room 8, Library Extension Building

Prof. Youhei Takeda

 

Department of Applied Chemistry

Osaka University

Youhei Takeda is an Associate Professor at Osaka University. Youhei earned his B.Eng. from Waseda University in 2005, followed by his Ph.D. from Kyoto University in 2010 under the guidance of Professor Tamejiro Hiyama. He then conducted postdoctoral research at Massachusetts Institute of Technology (MIT) with Professor Timothy M. Swager, during which, he was appointed as JSPS research fellow (DC2 and PD). In 2011, he joined Osaka University as an Assistant Professor and was promoted to Associate Professor in 2015. His achievements have been widely recognized, receiving several prestigious awards, including the Incentive Award in Synthetic Organic Chemistry, Japan (2019), The Young Scientists’ Prize from the MEXT (2020), The Nozoe Memorial Award for Young Organic Chemists (2020), Thieme Chemistry Journals Award (2021), and Asian Core Program Lectureship Award (2023). His research focuses on the innovative design and synthesis of heteroatom-embedded exotic π-conjugated organic molecules, with applications spanning various interdisciplinary fields.

The development of high-performance, multifunctional organic emitters is crucial for advancing applications in fields such as optoelectronics, sensing, and bio-imaging. Among these, heavy-metal-free organic emitters capable of efficiently harvesting electrically generated triplet excitons and converting them into light have garnered significant attention as the next-generation materials for highly efficient organic light-emitting diodes (OLEDs). From a materials design perspective, twisted or resonant donor-acceptor (D–A) p-conjugated systems have emerged as promising candidates for thermally activated delayed fluorescence (TADF) materials. This is due to their ability to distinctly separate the HOMO and LUMO, thereby reducing singlet-triplet energy splitting in excited states and accelerating reverse intersystem crossing. In 2014, we achieved a breakthrough by discovering an oxidative skeletal rearrangement of binaphthalene diamines (BINAMs) to synthesize dibenzo[a,j]phenazines (DBPHZs), a structure previously unattainable through conventional methods. Leveraging the unique molecular architecture and physicochemical properties of DBPHZ, we have developed novel multi-photofunctional organic emitters based on DBPHZ-cored twisted D–A–D triads and D–A–D–A macrocycles. These materials exhibit a range of advanced photophysical behaviors, including efficient TADF, multi-color-changing mechanochromic luminescence, and room-temperature phosphorescence (RTP).

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