Enhancing Deep Blue Emission by Selectively Tailoring Noncovalent Interactions

Abstract Organic phosphine‐based compounds hold important applications in various optoelectronic technologies, including organic light‐emitting diodes, X‐ray radiation detection, and circularly polarized luminescent materials. A fundamental understanding of their photophysical mechanisms is essential for designing high‐performance luminescent systems. In this work, tris(4‐chlorophenyl) phosphine (1) and tris(4‐chlorophenyl) phosphine oxide (2) are selected as model systems to investigate the mechanism underlying luminescence enhancement. Through in situ high‐resolution X‐ray single‐crystal diffraction under both dark and 360 nm laser irradiation, the experimental charge density distributions of both compounds are precisely characterized. Compared to 1, the P═O group in 2 not only weakens the C─H···π interaction that governs the bandgap, promoting the blueshift of emission, but also introduces strong hydrogen bonding (O···H) that regulates the rates of radiative and nonradiative transitions, considerably enhancing the photoluminescence quantum yield. This dual optimization effect, driven by the strong electronegativity of the electron‐withdrawing group, offers an effective avenue of designing high‐performance organic deep blue emission materials by selectively tailoring noncovalent interactions.