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]

　白金などの重原子を含む光学活性な有機金属錯体は、三重項状態からの円偏光”燐光”を示します。燐光発光性材料は、すでに有機 EL 素子 (OLED) に応用されており、近年も盛んに研究されています。

円偏光燐光材料は、円偏光の高機能性に加えて燐光特性による省エネルギー性が期待できるため、持続可能な社会創りには欠かすことができません。しかしながら、円偏光燐光は三重項状態が複雑であるため、その機構はほとんど未解明の状態でした。

 我々は高効率な円偏光燐光材料を開発するとともに、世界に先駆けて基礎理論の構築を行うことで当該分野に貢献しています[1-4]。

[1] Chem. Commun. 2020, 56, 15438-15441. 

[2] Chem. Mater. 2022, 34, 7959-7970. 

[3] Chem. Commun. 2023, 59, 5571-5574. 

[4] Chem. Commun. 2025, 61, 957-960.

　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]

　芳香族性は有機分子の光学特性等の予測/理解のための重要な指標です。我々は様々なπ拡張 Pt 錯体を用いて、燐光発光と芳香族性の相関関係を実験と理論計算で初めて明らかにしました。それらから芳香族性が低いほど励起状態の分子運動による熱失活が抑制され、室温で発光するという新法則を見出しました[5]。

[5] Chem. Eur. J. 2019, 25, 3650-3661. 

　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]

　柔らかな配位平面を有する Pt 錯体 は、室温溶液状態では発光を示さないが、結晶状態では結晶配列に依存した凝集誘起燐光を示します。本研究では、我々が開発した単結晶 X 線構造解析と理論計算を組み合わせた方法によって、初めて凝集誘起燐光の要因となる励起状態失活の阻害機構を明らかにしました。本システムは幅広い燐光性金属錯体に適用可能であるため、当該研究分野を大きく発展させ得るものであると考えています

[6]。

[6] Chem. Asian. J. 2021, 16, 3129-3140.