Room‐Temperature Phosphorescence Emitters Exhibiting Red to Near‐Infrared Emission Derived from Intermolecular Charge‐Transfer Triplet States of Naphthalenediimide−Halobenzoate Triad Molecules
Toshikazu Ono, Kazuki Kimura, Megumi Ihara, Yuri Yamanaka, Miori Sasaki, Hirotoshi Mori, Yoshio Hisaeda
Abstract
Room-temperature phosphorescence (RTP) emitters have attracted significant attention. However, purely organic RTP emitters in red to near-infrared region have not been properly investigated. In this study, a series of naphthalenediimide-halobenzoate-linked molecules are synthesized, one of which exhibits efficient RTP properties, showing red to near-infrared emission in solid and aqueous dispersion. Spectroscopic studies and single-crystal X-ray diffraction analysis have shown that the difference in the stacking modes of compounds affects the optical properties, and the formation of intermolecular charge-transfer complexes of naphthalenediimide-halobenzoate moiety results in a bathochromic shift of absorption and RTP properties. The time-dependent density functional theory calculations showed that the formation of charge-transfer triplet states and the external heavy atom effect of the halogen atom enhance the intersystem crossing between excited singlet and triplet states.