Design and Synthesis of Highly Stable N2O2-Type Azadipyrromethene NIR-II Dyes

Abstract N2O2-type azadipyrromethenes represent an important class of near-infrared (NIR) dyes that typically exhibit absorption below 900 nm. It is of great significance to extend their absorption beyond 900 nm. In this work, eight N2O2-type Zn (II)/Ni (II) azadipyrromethene NIR dyes with excellent solubility (>4 mg mL–1 in CHCl3) were synthesized and characterized. Compared with conventional N2O2-type azadipyrromethenes dyes, the absorption of these compounds exhibited a red shift to 1190 nm. Cyclic voltammetry measurements indicated that their LUMO energy levels ranged from −3.80 to −4.09 eV, showing a favorable tunable energy level range. Photostability and thermogravimetric analysis (TGA) results indicated that they possessed excellent photostability and thermal stability, with their thermal decomposition temperatures above 242 °C. The distinctive spectral properties, appropriate energy level alignment, and excellent thermal stability endow this class of materials with promising potential for applications as optoelectronic materials.