We are pioneering fundamental theories to clarify the mechanisms and properties that govern whether molecules in the triplet state emit light or remain non-emissive.
Optically active organometallic complexes containing heavy atoms such as platinum exhibit circularly polarized phosphorescence (CPP) originating from their triplet excited states. Phosphorescent materials have already been applied to organic light-emitting diodes (OLEDs) and continue to be intensively investigated in recent years.
CPP-active materials are particularly promising because they combine the advanced functionality of circular polarization with the energy efficiency inherent to phosphorescence, making them indispensable for building a sustainable society. However, due to the complexity of triplet states, the fundamental mechanism of CPP has remained largely unexplored.
We have contributed to this emerging field by not only developing highly efficient CPP materials but also pioneering the establishment of fundamental theoretical frameworks for CPP, ahead of other groups worldwide. [1–4]
[1] Chem. Commun. 2020, 56, 15438-15441.
[2] Chem. Mater. 2022, 34, 7959-7970.
Aromaticity is an essential indicator for predicting and understanding the optical properties of organic molecules. Using a series of π-extended platinum complexes, we have, for the first time, experimentally and theoretically clarified the correlation between phosphorescence and aromaticity. From these studies, we discovered a new principle: the lower the aromaticity, the more the nonradiative thermal deactivation caused by molecular motion in the excited state is suppressed, thereby enabling phosphorescence at room temperature. [5]
Platinum complexes with flexible coordination planes are non-emissive in solution at room temperature, but exhibit aggregation-induced phosphorescence in the crystalline state, depending on the crystal packing. In this study, by combining single-crystal X-ray structural analysis with theoretical calculations, we have, for the first time, elucidated the suppression mechanism of excited-state deactivation responsible for aggregation-induced phosphorescence. Since this system can be applied to a wide range of phosphorescent metal complexes, we believe it has great potential to significantly advance this research field. [6]
[6] Chem. Asian. J. 2021, 16, 3129-3140.
