One-axis Two-wing Guest-Host Strategy for Constructing Ultralong-lifetime Near-infrared Organic Phosphorescence Materials for Bioimaging

Abstract Organic near-infrared room temperature phosphorescence (RTP) materials have unparalleled advantages in bioimaging due to their excellent penetrability. However, limited by the energy gap law, organic matters with long wavelengths (> 700 nm) and long lifetimes (> 100 ms) have not been reported so far. In this work, we have obtained organic 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.