Room‐Temperature Phosphorescence of Crystalline 1,4‐Bis(aroyl)‐2,5‐dibromobenzenes (Eur. J. Org. Chem. 3/2016)

Abstract

The cover picture shows optical and phosphorescent images of 2,5‐dibromo‐1,4‐bis(4‐trifluoromethylphenylcarbonyl)benzene in crystals under ambient conditions with a simplified Jablonski diagram and the molecular structure of 1,4‐bis(aroyl)‐2,5‐dibromobenzene. The room‐temperature phosphorescence is observed only in crystals, but neither in solution nor in a doped polymer film. Thus, a class of the bis(aroyl)benzenes can serve as chromophores that exhibit crystallization‐induced room‐temperature phosphorescence. Intramolecular motion resulting in the energy loss in the triplet excited states is suppressed by several kinds of intermolecular interactions in crystals. Details are discussed in the article by M. Shimizu et al. on p. . The authors would like to warmly thank Ms. Kuniko Kayama for artistic inspiration and assistance in preparation of this cover picture.

Pure Organic Persistent Room‐Temperature Phosphorescence at both Crystalline and Amorphous States

“…However, unlike inorganic and organometallic phosphors, [30][31][32][33][34] the fabrication of efficient pure organic RTP luminogens remains challenging, owing to the spin-forbidden intersystem crossing (ISC) process and the high susceptibility of phosphorescence to molecular motions and external quenchers. [3][4][5][7][8][9][10][11][12][13] Even though great advances have been achieved for the molecular design of pure organic RTP through incorporation of halogens, aromatic carbonyls, and heteroatoms, [7][8][9][10][11][12][13] as well as effective suppression of nonradiative processes by supramolecular interactions, [35,36] micelle stabilization, [37] absorption on solid substrate, [38] crystal-lization, [3,4,7,[15][16][17] embedding into rigid matrices, [5,23,39] chemical bonding to polymer chains, [14] etc., the development of pure organic RTP remains in its infant stage. Furthermore, persistent RTP (p-RTP) with naked eye visible emission after ceasing the excitation is even difficult to achieve, despite it has diverse promising applications in advanced OLEDs, bioimaging, encryption and anticounterfeiting.…”