1,7‐Di‐tert‐butyl‐Substituted aza‐BODIPYs by Low‐Barrier Rotation to Enhance a Photothermal‐Photodynamic Effect

1,7‐Di‐tert‐butyl‐substituted aza‐BODIPYs (tBu‐azaBDP) were successfully obtained for the first time. The structures of tBu‐azaBDP and Ph‐azaBDP were confirmed by X‐ray crystal analysis, and tBu‐azaBDP 2 is more twisted than Ph‐azaBDP 5. tBu‐azaBDPs have significant photo‐stability and enhanced water solubility. tBu‐azaBDPs possess excellent optical properties, such as high molar extinction coefficients, broad full width half maxima, and large Stokes shifts, which is comparable to those of the parent dye Ph‐azaBDP. Although the low‐barrier rotation of the distal ‐tBu groups in tBu‐azaBDPs results in low quantum yield, photothermal conversion efficiency and singlet oxygen generation ability of tBu‐azaBDPs are more effective than those of Ph‐azaBDP, which is highly desirable for a photothermal‐photodynamic therapy agent. 1,7‐Di‐tert‐butyl‐substituted aza‐BODIPYs (tBu‐azaBDPs) were successfully prepared for the first time. Although the low‐barrier rotation of the distal ‐tBu groups in tBu‐azaBDPs results in low quantum yield, photothermal conversion efficiency and single oxygen generation ability of tBu‐azaBDPs are effective than those of Ph‐azaBDP, which is highly desirable for a photothermal‐photodynamic therapy agent.