Enhancing the phosphorescence performance of organic doped system by carbonylation of guests

The host-guest doped strategy has become the main method for constructing organic phosphorescence materials. In the doped system, guest molecules emit phosphorescence, therefore, improving the luminescence performance of guests is the key to optimizing the phosphorescence property of the doped materials. Herein, we designed to introduce the carbonyl group on the guest molecules. Carbonyl group can effectively promote n-π* transitions, thereby increasing the spin-orbit coupling (SOC) constant of the guests, ultimately improving the phosphorescence performance of the doped materials. Using the indazole derivative (IZ) as the initial guest, two other guests containing carboxyl group (IZ-CG) or ethoxycarbonyl group (IZ-EG) were successfully obtained. Further selected two small molecules and two polymers as the hosts to construct four doped systems. Among these doped systems, the phosphorescence performance of doped materials with IZ-CG or IZ-EG as the guest is significantly better than that of doped materials with IZ as the guest. The phosphorescence lifetime has increased by 2.3-5.0 times, and the phosphorescence quantum yield has increased by 3.0-5.7 times. Theoretical calculations and single crystal structures indicated that carbonyl groups can not only increase the SOC constant, but also enhance the intermolecular interactions of the guests. In addition, doped material can be effectively used for imaging subcutaneous and lymph nodes in mice, achieving a high signal-to-noise ratio.