Synthesis of aza-BODIPYs with barrier-free rotation of the -tBu group at 3-site and enhancement of photothermal therapy by triggering cancer cell apoptosis.

Breaking through the traditional 1,7,3,5-aryl substituted aza-BODIPY structure, asymmetric aza-BODIPYs, tBu-azaBDPs, containing non-aryl group at 3-site were prepared for the first time. tBu-azaBDP exhibited a severely twisted configuration. tBu-azaBDPs had a near-infrared fluorescence emission and high molar extinction coefficients. Although the barrier-free rotation of the distal -tBu group in tBu-azaBDP resulted in low fluorescence quantum yield, the photothermal conversion efficiency was markedly enhanced. tBu-azaBDP nanoparticles with laser irradiation were revealed to induce cell apoptosis in photothermal therapy. We consider that development of aza-BODIPYs with the barrier-free rotation of the -tBu group at 3-site provides a strong platform for design of phototherapy agents for cancer treatment in photothermal therapy by apoptosis.