New strategy for narrowing energy gaps by aza-substitution to isolated LUMO

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K19002
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 35:Polymers, organic materials, and related fields
• Research Institution: Kyoto University
• Principal Investigator: TANAKA Kazuo 京都大学, 地球環境学堂, 教授 (90435660)
• Project Period (FY): 2021-07-09 – 2023-03-31
• Keywords: 共役系分子 / 近赤外発光 / ホウ素錯体

Outline of Final Research Achievements

Substitution of electronegative nitrogen for carbon in the π-conjugated system (aza-substitution) can stabilize the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). In this project, we aim to show the selective lowering of isolated LUMO by aza-substitution for establishing a new strategy for narrowing the energy gap. In particular, molecules having an extended π-conjugated system are likely to lose solid-state luminescence, as is often the case with common organic luminescent dyes, due to concentration quenching caused by intermolecular interactions. In this research, we aimed to develop small near-infrared emitting dyes. By aza-substituting two sites on the benzene ring to selectively lower the LUMO, and by further complexing with boron, we were able to obtain near-infrared luminescence.

Free Research Field

高分子合成、光化学、元素化学

Academic Significance and Societal Importance of the Research Achievements

本研究の学術的意義は「孤立LUMO」という我々が初めて見出した概念に立脚し、アザ置換で選択的LUMOの引き下げを達成し、偶然性に頼らない狭ギャップ化の新戦略の確立を目指す点にある。従来の「共役の拡張」における分子の巨大化に伴う問題の解決のみならず、相乗的にさらなる長波長化も期待できる。また、量子化学計算的手法でゼロから設計可能であり、AIを用いた効率的な物質探索手法にも適用可能である。以上、本研究は我々の最近の学術的な発見に基づくため萌芽的段階であるが、達成時には狭ギャップ化の新戦略から機能性近赤外発光材料開発につながり、学術的インパクトと産業的波及効果は大きいと考えられる。