Abstracts

Chemiluminescence (CL) in the crystalline state is an attractive research subject because it is applicable to construct the solid-state reaction theories including kinetics and to design functional materials having the abilities to respond to external stimuli such as light, heat, vapor, etc. The first report on the solid-state CL is about the thermolytic CL reaction of rubrene endoperoxide found in 1926. While the mechanism of the solid-state CL of rubrene has not been clarified yet, this finding encourages us to develop the chemistry of the solid-state CL of an aromatic endoperoxide. In fact, we have clarified the relationships between the CL properties and crystal structure of 9,10-diphenylanthracene endoperoxide (DPA-EP). The thermolytic reaction of DPA-EP generates DPA and singlet oxygen (¹O₂) and ¹O₂ can show phosphorescence with the maximum at ca. 1275 nm. When a crystal sample of DPA-EP was heated to 200 ºC, 1275 nm-emission was observed to show that the thermolytic reaction and crystal melting proceeded simultaneously. The result indicates that the crystal lattice decreases the freedom of molecular motion for the reaction by intermolecular interactions. Based on the previous finding, we investigated here the thermolytic reaction of 9-phenyl-10-phenylethynylanthracene endoperoxide (PPEA-EP) as a more reactive endoperoxide compared to DPA-EP. Then, we found that heating of a PPEA-EP crystal sample at 120 ºC showed a dual-mode emission property with maintaining the solid state. One is 1275 nm-emission originated from ¹O₂ and the other is 510 nm-emission originated from PPEA excimer. In this presentation, we will discuss the mechanism of this characteristic CL emissions based on crystal structure, reactivity, and an energy relationship.