Synthesis and Characterization of Push‐Pull Aza‐BODIPY Dyes Towards Application in NIR‐II Photothermal Therapy

Abstract A new series of aza‐BODIPYs ( CN−X ) with significantly red‐shifted absorbances were designed and synthesized by installation of various electron‐donating groups on the para ‐positions of 3,5‐phenyl groups while strong electron‐withdrawing groups (nitrile groups) were fixed on the para ‐positions of 1,7‐phenyl moieties. Interestingly, strong electron‐donating groups such as N'N ‐dimethylaniline ( CN−NMe 2 ) could provide strong NIR absorption up to 857 nm and weak fluorescence emission up to 967 nm, whereas strong evidence supported heat production via non‐radiative decay after excitation. Electrochemical studies revealed that the substituents on the dyes showed strong effects on the oxidation potentials where the oxidation wave of CN−NMe 2 occurred at the lowest overpotential, followed by CN−OMe , CN−Me , CN−Br and CN−H , respectively. Calculations were also performed to understand the push‐pull effect of the substituents on the aza‐BODIPY systems. Finally, applications of dyes in NIR cancer cell imaging and the NIR‐II photothermal effect were also investigated.