Role of Halobenzene Guest Molecules in Modulating Room Temperature Phosphorescence of Benzophenone-Naphthalene Diimide Inclusion Crystals

Materials exhibiting room temperature phosphorescence (RTP) have recently emerged as a subject of significant interest. In this study, we successfully created inclusion crystals by introducing halobenzenes as guests into a host molecule combining benzophenone with naphthalene diimide. This approach led to the creation of fascinating fluorescence and RTP properties dependent on the guest molecules. Notably, crystals containing chlorobenzene showed cyan fluorescence, while those with iodobenzene displayed red RTP. This difference highlights the impact of the guest molecule on the luminescent properties, with the significant external heavy-atom effect of iodobenzene playing a key role in promoting efficient intersystem crossing between the excited singlet and triplet states. Crystals with bromobenzene exhibited a unique blend of fluorescence and RTP, both from benzophenone and naphthalene diimide, highlighting the moderate heavy-atom effect. These findings reveal composite materials with remarkably diverse and interesting optical characteristics. In this study, inclusion crystals composed of a benzophenone-naphthalenediimide host (1) and halobenzene guests were developed, unveiling unique fluorescence and room temperature phosphorescence (RTP) properties. A 1 : 1 host-guest composition in these crystals was confirmed, and the effects of various guests, such as chlorobenzene, bromobenzene, and iodobenzene, on their luminescence were observed. Additionally, the influences of external heavy atom effects on the RTP properties of these crystals were discussed. image