Nanotechnologies / Materials
Organic electronics, Energy conversion, Life science

Efficient and facile induction of room-temperature phosphorescence byconfinement of luminescent molecules in heavy atom spaces
Department of Applied Chemistry, Graduate School of Engineering
Professor Norimitsu Tohnai
https://researchmap.jp/read0089607?lang=en

Nanotechnologies / Materials

AbstractThe development of room-temperature phosphorescent materials using only organic molecules has been limited due to thecomplex molecular design and control of specific intermolecularinteractions required to induce room-temperature phosphorescence. Our research group has succeeded in constructing a highly
efficient and facile room-temperature phosphorescence induction
system by confining luminescent molecules inside heavy atomic
spaces which are generated by arranging heavy atoms such as
bromine and iodine on the pore surface in porous materials. These
porous materials can confine a wide variety of luminescent molecules, allowing the color tone, lifetime, and other characteristics ofroom-temperature phosphorescence to be freely modified depending on the application.

use is limited to heavy metal complexes with rare metals such as
iridium and platinum. From a geopolitical perspective, the systematic development of room-temperature phosphorescent materials
that do not use such rare metals and are composed of all-organicmaterials are desirable.
This system has the potential to efficiently and facilely induceroom-temperature phosphorescence in a variety of previously unknown luminescent molecules, and is expected to have a significant impact on the fields of organic electronics, energy conversion
and life sciences.

▍ Background & Results
Our research group has reported that a wide variety of porous
organic salts (POSs) can be constructed from various organic
sulfonic acids and bulky amines. These POSs can be designed tohave different sizes, shapes, and surface properties by combining
the acids and the amines. These materials led to great expectations for the development of selective adsorption and separationof carbon dioxide and chlorofluorocarbon gases, storage materials
for fuel gases such as hydrogen and methane, and other applications in ultra-high sensitive sensing devices for specific chemicals
such as toxic substances. In this research, we have establisheda method that allows flexible chemical modification of the porous
material’s pore surface.
Designing porous structures using tetrasulfonic acid with an adamantane core and triphenylmethylamine (TPMA-X), in which heavy
atoms such as bromine and iodine are introduced at the para position of the phenyl group, led to sodalite-type porous organic salts(s-POS) with large cage-shaped pores as large as 2 nanometers
in diameter. On the surface of these pores, bromine and iodine
introduced into TPMA-X are exposed, creating a space surrounded by heavy atoms. Confining luminescent polycyclic aromaticcompounds (pyrene, coronene, etc.) within these pores enabledextremely efficient and facile room-temperature phosphorescence.
The heavy atom space has a large spin-orbit interaction, easily
generating the excited triplet state necessary for phosphorescentemission. In addition, the confinement of luminescent moleculesin the pores prevents the vibrational deactivation of excitons byheat. In addition, the sodalite-type porous organic salts selectively
adsorb only carbon dioxide and do not adsorb oxygen at all, thus
suppressing singlet oxygen quenching. As described above, thissystem developed can efficiently and facilely induce room-temperature phosphorescence even in air at room temperature due to thethree effects of heavy atom space.

Figure 1. Construction of Sodalite-type Porous Organic Salts and Confinement ofLuminescent Molecules in Heavy Atom Space▍ Significance of the research and Future perspective
Room-temperature phosphorescent materials have been used aslight-emitting materials in high-efficiency OLEDs, but their current

Figure 2. Room-Temperature Phosphorescence Induction of Pyreneby Heavy-Atom SpaceP a t e n tSei, Hiroi; Oka, Kouki; Tohnai, Norimitsu et al. Cage-like sodalite-type porous organic salts enabling luminescent molecule’s incorporation and roomtemperature phosphorescence induction in air. Small. 2023, 19, 2301887. doi: 10.1002/smll.202301887
Sei, Hiroi; Oka, Kouki; Tohnai, Norimitsu. Incorporation of coronene into cage-like porous organic salts and induction of its room-temperature
Tr e a t i s ephosphorescence in air. ChemNanoMat. 2023, 9, e202300248. doi: 10.1002/cnma.202300248
Ami, Takahiro; Oka, Kouki; Tohnai, Norimitsu et al. Porous organic salts: Diversifying void structures and environments. Angew. Chem., Int. Ed. 2022, 61,e202202597. doi: 10.1002/anie.202202597
URL
K e y w o r d porous organic salt, heavy atom effect, room temperature phosphorescence