Highly Efficient Multifunctional Luminescent Radicals

Abstract

Stable organic luminescent radicals are a special class of compounds integrating optical, electrical, and magnetic properties. Luminescent radicals not only have potential applications in the field of the organic light-emitting diodes (OLEDs) but can also be applied in the fields of fluorescence sensing, bioimaging, and so forth. Nevertheless, due to the adverse effects of solvent polarity on the luminescent performance of radicals, no feasible approaches have been found in the literature toward fluorescent sensing. In this work, we report two luminescent radicals, 2αPyID-TTM and 2δPyID-TTM, whose emissions show high efficiency and less dependence on solvent polarity. Both radicals show remarkable protonationdeprotonation properties. Besides, 2αPyID-TTM exhibits significant fluorescence quenching and colorimetric response toward Fe 3+ in aqueous solution. This suggests the possibility of a fluorometric/ colorimetric dual-channel probe for Fe 3+ . Moreover, an optimized OLED using 2δPyID-TTM as an emissive dopant shows pure red emission and a maximum external quantum efficiency (EQE) of 10.6%. These results show promise for luminescent radicals as fluorescent probes and electroluminescent emitters.

Enhancement of fluorescence and photostability of luminescent radicals by quadruple addition of phenyl groups

“…These phenomena were also reported in D–π–A-type radicals with a diminished donor character. 13 c ,15 The lack of electron-donation from the methoxy group caused the difference in the D 1 excited state properties.…”

“…Recently, improved photostability by adding donors to radicals has also been reported. 2 e,f ,13 d ,15 We studied whether methoxy groups could serve as such donors to improve fluorescence efficiency and photostability.…”

Characterization of a Novel Fe2+ Activated Non-Blue Laccase from Methylobacterium extorquens

“…It is probable that N in the residues form Melac13220 formed a complex with Fe 2+ and that the two transition electrons in the outer layer of N formed a co-orbital with Fe. The significant response of Fe 2+ with N as the chelating atom may be due to the better thermodynamic affinity and faster chelation rate of iron ions, as well as their stronger oxidation, compared to that of other transition metal ions [ 52 ].…”

Research Progress on Triarylmethyl Radical-Based High-Efficiency OLED

“…At the same time, they synthesized two disubstituted radicals, biscarbazoline-substituted TTM, 2αPyID-TTM and 2δPyID-TTM, which also realized excellent luminescence properties and better thermal and electrochemical stability. Additionally, because 2αPyID-TTM and 2δPyID-TTM had more protonation sites, they exhibited better proton response characteristics than single-substituted radicals [95]. Then, in 2018, Li's group selected carbazoles with different N positions to modify TTM and obtained four stable triarylmethyl radicals, αPyID-TTM, βPyID-TTM, γPyID-TTM, and δPyID-TTM [94], which exhibited red light emissions (Figure 13).…”

“…At the same time, they synthesized two disubstituted radicals, biscarbazoline-substituted TTM, 2αPyID-TTM and 2δPyID-TTM, which also realized excellent luminescence properties and better thermal and electrochemical stability. Additionally, because 2αPyID-TTM and 2δPyID-TTM had more protonation sites, they exhibited better proton response characteristics than single-substituted radicals [ 95 ].…”