The influence of the molecular packing on the room temperature phosphorescence of purely organic luminogens

Jie Yang,Kanyi Pu,Zichun Ren,Xuming Gao,Xu Zhen,Bin Wang,Yujun Xie,Qian Peng,Jiaqiang Wang,Jianrong Li,Zhen Li

doi:10.1038/s41467-018-03236-6

Abstract

Organic luminogens with persistent room temperature phosphorescence (RTP) have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, these materials are still very scarce, partially due to the unclear mechanism and lack of designing guidelines. Herein we develop seven 10-phenyl-10H-phenothiazine-5,5-dioxide-based derivatives, reveal their different RTP properties and underlying mechanism, and exploit their potential imaging applications. Coupled with the preliminary theoretical calculations, it is found that strong π–π interactions in solid state can promote the persistent RTP. Particularly, CS-CF3 shows the unique photo-induced phosphorescence in response to the changes in molecular packing, further confirming the key influence of the molecular packing on the RTP property. Furthermore, CS-F with its long RTP lifetime could be utilized for real-time excitation-free phosphorescent imaging in living mice. Thus, our study paves the way for the development of persistent RTP materials, in both the practical applications and the inherent mechanism.

Highlights

FluorescenceNanoparticle (CS-F)Phosphorescence 5 Axillary11,000 lymph nodeRadiance (108 p/s/cm2/sr)Radiance (p/s/cm2/sr)
After stopping the photo-excitation, green or sky blue room temperature phosphorescence (RTP) emissions lasting for more than 1.5 s could be visually seen for CS-H, CS-Br, CS-Cl, and CS-F, while those of CS-CH3O and CS-CH3 would die out quickly
This viewpoint is applicable to other RTP systems in which the π– π distances in single crystals are found to have direct relationship with RTP lifetimes (Supplementary Figs. 31–32), further confirming the accuracy of the statement[21,46]

Summary

Introduction

FluorescenceNanoparticle (CS-F)Phosphorescence 5 Axillary11,000 lymph nodeRadiance (108 p/s/cm2/sr)Radiance (p/s/cm2/sr). The introduction of the electron-withdrawing substituents would be beneficial to the π–π interactions, which could stabilize the excited triplet state accompanying with the ultralong RTP effect in this system.

Results

Conclusion