Constructing Ultralong Near-infrared Organic Phosphorescence Materials with 732 nm through One-axis Two-wing Guest-Host Strategy for Bioimaging

In this work, we have obtained organic room temperature phosphorescence/RTP materials with long wavelengths (657-732 nm) and long lifetimes (102-324 ms) for the first time through the one-axis two-wing guest-host strategy. The one axis refers to that the guest molecule has sufficient conjugation to reduce the lowest triplet energy level and the two wings refer to that the host assists the guest in exciton transfer and inhibits the non-radiative transition of guest excitons. These materials exhibit good tissue penetration in bioimaging. Thanks to the characteristic of long lifetime and long wavelength emissive RTP materials, the tumor imaging in living mice with a signal to background ratio value as high as 43 is successfully realized. This work provides a practical solution for the construction of organic RTP materials with both long wavelengths and long lifetimes used in bioimaging.