Fluorescent Organic π‐Radicals Stabilized with Boron: Featuring a SOMO–LUMO Electronic Transition

Abstract

We report on the fluorescence properties of a new class of emissive and stable π‐radicals that contain a boron atom at a position distant from the radical center. A fully planarized derivative exhibited an intense red fluorescence with high fluorescence quantum yields (ΦF >0.67) even in polar solvents. To elucidate the origin of this phenomenon, we synthesized another boron‐stabilized radical that contains a bulky aryl group on the boron atom. A comparison of these derivatives, as well as with conventional donor–π–acceptor (D–π–A)‐type emissive π‐radicals, unveiled several characteristic features in their photophysical properties. A theoretical analysis revealed that the SOMO–LUMO electronic transition generates an emissive D1 state. Unlike conventional D–π–A‐type π‐radicals, this state does not undergo significant structural relaxation. The boron‐stabilized π‐radicals demonstrated promising potential for organic light‐emitting diodes as an emitting material.

Theoretical investigations on P-stabilized boryl cation radicals: from the Aufbau principle to SOMO–HOMO conversion

“…12 Although the SHC molecules have attracted considerable attention in radical chemistry, only a limited number of organic radical molecules have been reported. Boron-containing radicals are well-known attractive species because of their fundamental significance in chemistry and potential application in organic synthesis, 13,14 particularly the P-stabilized boryl radicals, which have attracted increasing attention in boron-containing radical chemistry, due to their increased stability resulting from the enhanced intramolecular P → B interaction. 15,16 Nevertheless, although a few P-stabilized boryl radicals have been studied to date, the P-stabilized boryl radicals with SHC properties have not been reported yet.…”

Systematic radical species control by electron push–pull substitution in the perylene-based D–π–A compounds

“…Over the past few years, there has been a steadily growing interest in stable organic radicals and radical ions because of their intriguing electronic, optical, and magnetic properties. [1][2][3][4][5][6] Radical species with fascinating optoelectronic properties have led to manifold applications ranging from information storage, 7 uorescence probes, 8,9 chemical sensors, 10,11 organic electronic devices, 12,13 or photovoltaics. [14][15][16] These considerable advances have equally required radical generation efficiency, kinetics and stability.…”

Ladder-type boron-containing π-systems with enhanced open-shell characteristics and photothermal conversion properties

“…1a, including neutral boron-containing π-monoradicals (I-III) and π-diradicaloids (IV-VII). [23][24][25][26][27][28][29][30][31] For instance, Yamaguchi et al elegantly developed the highly stable π-radical I that contains a boron atom in a planarized triphenylmethyl radical framework, and demonstrated its potential utility as an ambipolar semiconductor in singlecrystal field-effect transistors and as an emitting material in organic light-emitting diodes. 23,24 Wang et al reported dioxoborocyclic monoradical III and diradical VII as new kinds of boron-containing π-radicals, which feature an intramolecular ion pairing state via Lewis acid-induced single electron transfer.…”

“…[23][24][25][26][27][28][29][30][31] For instance, Yamaguchi et al elegantly developed the highly stable π-radical I that contains a boron atom in a planarized triphenylmethyl radical framework, and demonstrated its potential utility as an ambipolar semiconductor in singlecrystal field-effect transistors and as an emitting material in organic light-emitting diodes. 23,24 Wang et al reported dioxoborocyclic monoradical III and diradical VII as new kinds of boron-containing π-radicals, which feature an intramolecular ion pairing state via Lewis acid-induced single electron transfer. 26,31 Braunschweig et al developed cAAC-stabilized 9,10-diboraanthracene V, proved its open-shell singlet diradical ground state and further explored its reactivity toward gaseous CO and its fixation.…”