Electron Acceptor Modulation: Unlocking α-Type Transition in D^●-A Luminescent Radicals

Abstract

The development of luminescent radicals with α-type transition properties is significant for advancing the understanding of luminescence mechanisms and photophysical properties in radical-based systems. Here, we present a straightforward strategy for acquiring stable luminescent radicals with α-type transition by directly decorating bis(2,4,6-trichlorophenyl)methyl radicals (BTM)-based luminescent radicals with strong electron acceptors. This approach effectively narrows the energy gap between the singly occupied molecular orbital (SOMOα) and lowest doubly unoccupied molecular orbital (LUMOα) (ΔE_{SOMOα→LOMOα}), enabling a transform of luminescent radicals from the conventional β-type transition to the rare α-type transition upon D₀→D₁ excitation process. The α-type transition was experimentally validated through the fabrication of organic light-emitting diodes (OLEDs) incorporating appropriate host materials. The result also expands the selection of available host materials for OLED devices exploiting radicals as emitters, as more host materials with higher highest occupied molecular orbital (HOMO) can now be considered. This work not only establishes a rational molecular design strategy for luminescent radicals with α-type transition but also provides valuable insights to guide future research in radical-based optoelectronic materials.

Keywords

Stable radicals / Doublet emission / α-type transition / D^●-A radicals / OLED devices / Electron transfer / Electronic structure / Semiconductors / Fluorescence / Quantum chemistry / Materials science

RIGHTS & PERMISSIONS

2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH