Single‐Component Molecular Dual Persistent Room Temperature Phosphorescence from Low‐ and High‐Lying Triplet States

Abstract

Single molecules with dual persistent luminescence are very rarely explored, in spite of their emerging use in frontier optoelectronic applications. Here, a pure organic phosphor of tris(4‐chlorophenyl)phosphine oxide (CPO) possessing a large energy gap between the lowest excited triplet (T1) and higher excited triplet (T2) states is reported, which can emit dual persistent room‐temperature phosphorescence (RTP) from low‐ and high‐lying triplet excited states. The femtosecond transient absorption experiments and theoretical calculations reveal that the excitons to the T1 and T2 states are populated through different pathways. As a result, the distribution of the triplet excitons can be efficiently manipulated by using different excitation energy, and tunable afterglow colors from green to yellow can be achieved. Furthermore, the CPO molecule is successfully applied in the fabrication of high‐level anti‐counterfeiting tags and flexible 3D objects with curling properties. From these initial discoveries, it is expected that triphenylphosphine derivatives, with their rich chemistry of core‐substitution, can provide infinite opportunities in the expansion of organic molecules with high‐lying persistent RTP.

[4]Triangulenes Modified by Three Oxygen-Boron-Oxygen (OBO) Units: Synthesis, Characterizations, and Anti-Kasha Emissions

“…Normally, photoluminescence of organic molecules originates from only the lowest excited state of a given spin multiplicity and is irrespective of the excitation wavelength, which is also known as Kasha’s rule . The significant overlap between the weak absorption band over 400 nm and fluorescence exhibits the possibility of anti-Kasha emissions (Figure c), which is also in agreement with the forbidden S 0 → S 1 and S 0 → S 2 transitions calculated by TD-DFT (Section S7 in SI). , To further investigate the anti-Kasha emission behaviors of 1-C5 , 1-C10 , and 1-Mes , the excitation-wavelength-dependent fluorescence and phosphorescence spectra (Figure b,d and Section S5 in SI) and emission-wavelength-dependent excitation spectra (Figure c and Section S5 in SI) were exploited. − Different solvents were tested to exclude the influence of solvents on the anti-Kasha emission phenomenon (Figures S26–S34 in SI). As shown in Figure b, the right shoulder intensity at 410 nm of the emission of 1-Mes was increased when the excitation wavelength was changed from 350 to 370 nm.…”

“…49,50 The higher triplet states should be generated through intersystem crossing (ISC) from higher singlet states instead of thermal repopulation. 47 This phenomenon of phosphorescence from higher triplet states could have great potential in organic blue-emitting phosphorescent materials. In summary, a class of [4]triangluenes modified by three OBO units has been synthesized and characterized by singlecrystal X-ray diffraction analysis.…”

“…The excitation-wavelength-dependent phosphorescence spectra of 1-Mes at 77 K under nitrogen showed that the phosphorescence from higher excited triplet states exists (Figure d and Section S5.3 in SI). The different time scales of phosphorescence decay at different emission peaks indicate that these emission peaks could originate from different higher triplet states (Section S5.3 in SI). , The higher triplet states should be generated through intersystem crossing (ISC) from higher singlet states instead of thermal repopulation . This phenomenon of phosphorescence from higher triplet states could have great potential in organic blue-emitting phosphorescent materials.…”

Simple Stimulus-Responsive Organic Long Persistent Luminescence Systems Based on Methoxy-Functionalized Triphenylphosphine

“…By contrast, n/π-type pure organic room-temperature phosphorescent molecules are favored because of their good photophysical properties, modifiability, thermal stability, processability, and biocompatibility, which is an important development direction in the current research field of organic room-temperature phosphorescent materials. − Nevertheless, most of the previous studies were limited to nitrogen-containing n/π systems with relatively single modifiable sites and properties . There have been few studies of n/π-type arylphosphine long afterglow materials with readily modified structures and properties . Compared to nitrogen atoms in the same main group, phosphorus atoms have unique electronic properties.…”

“…23 There have been few studies of n/π-type arylphosphine long afterglow materials with readily modified structures and properties. 24 Compared to nitrogen atoms in the same main group, phosphorus atoms have unique electronic properties. For example, the lone pair of electrons on the central phosphorus atom provides the possibility for the n → π* transition.…”