Nanotechnologies / Materials
Organic electronic materials, Organic magnetic materials

Triplet diradical cation with near-infrared emission
Department of Materials Engineering Science, Graduate School of Engineering Science
Associate Professor Akihiro Shimizu

https://researchmap.jp/7000009063?lang=en

Professor Ryo Shintani					https://researchmap.jp/RMshintani?lang=en

Nanotechnologies / Materials

Abstract
Luminescent organic molecules have attracted attention as
materials for organic light-emitting diodes and sensing devices.
In addition to typical closed-shell molecules, luminescent organic
radicals have recently been studied. On the other hand, triplet
diradicals with two unpaired electrons aligned have attracted attention as magnetic materials. However, their optical properties
remained to be clarified due to their high reactivity and instability,
and only two triplet diradicals emitting UV-visible light have beenreported to date.
We previously succeeded in designing and synthesizing a triangulene derivative, a triplet polycyclic hydrocarbon. In this study, we
designed and synthesized a nitrogen-doped triangulene cation byreplacing the central carbon atom of the triangulene derivative witha nitrogen cation. The nitrogen-doped triangulene cation had similar magnetic properties to the triangulene derivative but showedsignificantly different optical properties, exhibiting near-infraredabsorption and emission.

▍ Significance of the research and Future perspective
This is the first study of a triplet diradical with near-infrared emission. On the basis of this study, various luminescent triplet diradicals would be generated, leading to the creation of functional organic materials with characteristic optical and magnetic properties.

▍ Background & Results
Luminescent organic molecules have attracted attention as
materials for organic light-emitting diodes and sensing devices.
In addition to typical closed-shell molecules, luminescent organic
radicals have recently been studied. On the other hand, triplet
diradicals with two unpaired electrons aligned have attracted attention as magnetic materials. However, their optical properties
remained to be clarified due to their high reactivity and instability,
and only two triplet diradicals emitting UV-visible light have beenreported to date.
We previously succeeded in designing and synthesizing a triangulene derivative, a triplet polycyclic hydrocarbon, and experimentally elucidated that the two unpaired electrons aligned evenat room temperature. In this study, we designed and synthesized
a nitrogen-doped triangulene cation by replacing the central carbon atom of the triangulene derivative with a nitrogen cation togenerate a stable triplet diradical. The nitrogen-doped triangulene
cation was stable in air, and had similar magnetic properties to thetriangulene derivative: two electrons were delocalized over the periphery of the molecule and aligned even at room temperature. Thenitrogen-doped triangulene cation exhibited near-infrared absorption at 815 nm and emission at 846 nm because of its rigid corestructure.
Quantum chemical calculations showed that the characteristic
optical properties were caused by breaking the alternancy symmetry of triangulene by nitrogen doping, making the T0–T1 transition
allowed. The doping of a nitrogen cation to triplet hydrocarbons
would be a promising method to generate triplet diradical cation
with magnetic properties similar to the parent hydrocarbons butwith different optical properties.

P a t e n t
Arikawa, Shinobu; Shimizu, Akihiro; Shintani, Ryo et al. A kinetically stabilized nitrogen-doped triangulene cation: Stable and NIR fluorescent diradical
cation with triplet ground state. Angew. Chem., Int. Ed. 2023, 62(29), e202302714. doi: 10.1002/anie.202302714
UR
L http://www.chem.es.osaka-u.ac.jp/poc/en/
K e y w o r d magnets, spins, radicals, organic molecules, near-infrared absorption
Tr e a t i s e