Acquiring Charge-Transfer-Featured Single-Molecule Ultralong Organic Room Temperature Phosphorescence via Through-Space Electronic Coupling.

Although long-lived triplet charge-transfer ( CT) state with high energy level has gained significant attention, the development of organic small molecules capable of achieving such states remains a major challenge. Herein, by using the through-space electronic coupling effect, we have developed a compound, namely NIC-DMAC, which has a long-lived CT state at the single-molecule level with a lifetime of 210 ms and a high energy level of up to 2.50 eV. Through a combination of experimental and computational approaches, we have elucidated the photophysical processes of NIC-DMAC, which involve sequential transitions from the first singlet excited state (S ) that shows a CT character to the first triplet excited state (T ) that exhibits a local excited state feature ( LE), and then to the second triplet excited state (T ) that shows a CT character (i.e., S ( CT)→T ( LE)→T ( CT)). The long lifetime and high energy level of its CT state have enabled NIC-DMAC as an initiator for photocuring in double patterning applications.