Chemical Society Seminar: Youhei Takeda-Triplet-Harvesting Organic Emitters Based on a Dibenzo[a,j]phenazine Core: From Novel Synthesis to Multifunctional Applications

Abstract:

The design of high-performance, multifunctional organic emitters is pivotal for advancing technologies in optoelectronics, sensing, and bio-imaging. Heavy-metal-free organic materials that efficiently harvest triplet excitons and converting them into light are emerging as next-generation candidates for high-efficiency organic light-emitting diodes (OLEDs) From a materials-design standpoint, twisted or resonant donor-acceptor (D–A) -conjugated systems are promising for thermally activated delayed fluorescence (TADF), as they spatially separate HOMO and LUMO to reduce singlet-triplet energy gaps, thereby accelerating reverse intersystem crossing.  

In 2014, we achieved a synthetic breakthrough via an oxidative skeletal rearrangement of binaphthalene diamines (BINAMs), leading to the previously inaccessible dibenzo[a,j]phenazines (DBPHZ) scaffold. Leveraging the unique structure and physicochemical properties of DBPHZ, we designed and synthesized novel DBPHZ-cored emitters, including twisted D–A–D triads and D–A–D–A macrocycles. These emitters exhibit advanced photophysical functionalities—efficient TADF, multi-color-mechanochromic luminescence, and room-temperature phosphorescence (RTP). 

This presentation will cover key publications including:  

1) Chem. Commun. 2014, 50, 10291; 2) Angew. Chem., Int. Ed. 2016, 55, 5739; 3) Chem. Sci. 2017, 8, 2677; 4) Chem. Commun. 2018, 54, 6847; 5) Commun. Chem. 2020, 3, 118; 6) J. Am. Chem. Soc. 2020, 142, 1482; 7) ACS Appl. Mater. Interfaces 2021, 13, 2899; 8) Angew. Chem., Int. Ed. 2024, 63, e202405158; 9) Acc. Chem. Res. 2024, 57, 2219; 10) ChemRxiv doi: 10.26434/chemrxiv-2025-sfp9s. 

Acknowledgements  

Parts of this research were supported by the JST ASPIRE program (Adopting Sustainable Partnerships for Innovative Research Ecosystem; Grant No. JPMJAP2424), which aims to foster international collaboration and advance Japan’s research ecosystem.  

Bio:

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.