Regulating Phosphorescence Lifetime of Organic Cocrystals by Alkyl Engineering

Abstract

Phosphorescent cocrystal is one of the emerging room-temperature phosphorescence (RTP) materials. However, it remains a great challenge to understand the relationship between the phosphorescent properties and molecular aggregation. Herein, we prepared a series of organic cocrystals with RTP features composed of different alkyl chain lengths. It is worth noting that the phosphorescent lifetime varied by the different lengths of alkyl chains. For melamine−succinic acid cocrystal, the phosphorescence lifetime can reach up to 512 ms. From the single-crystal analysis, the longer lifetime was mainly attributed to the shorter distance of molecular stacking between phosphorescent chromophores resulting in smaller free volume. This study not only provides a simple method to prepare RTP materials but also explores the relationship between phosphorescent properties and molecular stacking in organic phosphorescent cocrystals.

Enhancing Purely Organic Room Temperature Phosphorescence via Supramolecular Self‐Assembly

“…In addition, effective through-space conjugation narrowed the energy gaps ΔE ST , thus further facilitating the ISC process. Following the above, Qu et al prepared three phosphorescent cocrystals of melamine and alkyl carboxylic acids, with the longest phosphorescence lifetime reaching 512 ms. [29] Halogen bonding also provides a convenient pathway to construct RTP cocrystals. In 2019, Fu and co-workers discovered that 1,7-phenanthroline (PR) and 1,4-diiodotetrafluorobenzene (DITFB) with the stoichiometric ratio of 1:0, 2:1, and 1:1, could form three kinds of RTP cocrystals (Figure 5c,d).…”

“…Following the above, Qu et al. prepared three phosphorescent cocrystals of melamine and alkyl carboxylic acids, with the longest phosphorescence lifetime reaching 512 ms. [ 29 ]…”