Thermally Activated Delayed Fluorescence and Room‐Temperature Phosphorescence in Sulfidoazatriangulene‐Based Materials and their S‐oxides

Abstract

with higher-lying triplet states. [9] TADF behavior can be observed if the energy gap between T 1 and S 1 (ΔE ST ) is sufficiently small. This requires minimization of the electron exchange interaction, which is typically achieved by spatial separation of a material's frontier molecular orbitals (HOMO and LUMO). The ability to productively harvest triplet excitons in allorganic systems has unlocked many new applications for TADF and RTP materials, including photocatalysts, [10][11][12][13] luminescent sensors, [14][15][16][17][18] tools for information encryption, [19][20][21][22][23] bioimaging probes, [24][25][26][27] and emitters for electroluminescent devices.Despite their advantages, many donoracceptor (D-A) TADF compounds exhibit poor photostability and low color purity, hindering their practical use. Triarylamines in particular are often the cause of poor stability in these systems, despite being the most common π-electron donors used in TADF materials today. The cleavage of C(sp 2 )N(sp 2 ) bonds is a common degradation mechanism in triarylamine-containing organic semiconductors, [28] and few triphenylamine radical cations are known to be stable. [29] As a result, the identification of new electron donors with improved photophysical properties remains a critical need.Rigidified electron donors such as hexamethylazatriangulene (HMAT) have recently been used to give TADF materials with improved photoluminescence quantum yields, narrower emission spectra, higher two-photon cross sections, and improved photostability. [30][31][32][33] These outcomes are achieved by reducing vibrational and rotational degrees of freedom, giving improved properties that are almost universally desirable in optoelectronics. This approach was described by Brédas in 2017 by combining triazine (TRZ) as a weak acceptor with the HMAT donor, giving the green emitter HMAT-TRZ (Figure 1). [33] In spite of a small D-A dihedral angle and a large ΔE ST (0.38 eV), this material displays TADF in doped poly(methylmethacrylate) (PMMA) films. Several more coplanar D-A TADF materials have since been reported, exhibiting enhanced PLQY, color purity, and molar absorptivity as a consequence of molecular rigidity. [31,32,34,35] These advances motivated us to seek new rigidified moieties for the design of high-performance TADF and RTP materials. In 2019, Lacquai and Kato simultaneously described an S,C,C-bridged triphenylamine (SMAT), and demonstrated Structural constraint is an emerging strategy for improving the photoluminescence quantum yield, molar absorptivity, and color purity of luminescent materials. In this report, emitters displaying thermally activated delayed fluorescence (TADF) are achieved for the first time using the planarized donor sulfidotetramethyazatriangulene (SMAT). Compared to non-planarized phenothiazine (PTZ) donors, the enhanced rigidity of SMAT contributes to improved color purity and photoluminescence quantum yield, with up to 90% quantum yield observed for donor-acceptor compounds in toluene solution. Planarized SMAT-base...

Deoxygenation-Promoted Aggregation-Induced TADF–RTP Dual Emission for High-Contrast Channel-Selectable Hypoxia Probing

“…Sulfur atoms provide powerful electron donation capability and high-energy electron orbitals that can enhance SOC by the heteroatom effect. Compared to the complex synthesis and purification processes of boron and nitrogen-centered materials, sulfur-modified emitters are particularly attractive in the field of bioimaging. − These considerations motivate us to choose persulfurated arene with its aggregation-induced phosphorescence (AIP) behavior as a core and introduce functional moieties with different electronic push–pull capabilities for branch grafting to derive a TADF property.…”

Thermal control over phosphorescence or thermally activated delayed fluorescence in a metal–organic framework

“…[26][27][28][29] Based on the mechanisms described above, phosphorescence and TADF can potentially be obtained simultaneously in single-component materials. 4,19,30,31 However, the controlled switching between ISC-related phosphorescence and RISC-related TADF remains challenging.…”

Recent advances in the cyclization reactions of pyridinium 1,n-zwitterions (n = 4 and 5): scope and mechanism

“…1, examples of drugs, nitrogen-containing materials, and bioactive compounds containing nitrogen or sulfur atoms include lipoic acid, 2 chlorpromazine, 3 CGP37157, 4 heronamide D, 5 GF196960, 6 asperlicin C, 7 pyrazinodiindolizine (PDIz), 8 HATCN, 9 and SMAT-TRZ. 10 Among them, GF196960 possesses anti-hypertensive properties and plays an important role in the field of medicine. HATCN has been widely used in organic materials due to its excellent properties; for example, the doping of HATCN could significantly improve the stability of organic materials and prolong their lifetimes.…”