Water-soluble chiral tetrazine derivatives: towards the application of circularly polarized luminescence from upper-excited states to photodynamic therapy.

A new family of water-soluble chiral tetrazine derivatives and is reported. Spectroscopic studies reveal that the derivatives violate Kasha's rule and emit from their upper-excited states (S , > 1). The transition assignments are supported by time-dependent density functional theory calculations. More importantly, both chromophores exhibit anisotropy factors on the order of ∼10 to 10 for circular dichroism and circularly polarized luminescence (CPL) from upper-excited states. Additionally, the nonplanar geometry of the derivatives induces a significant yield of triplet excited states. Transient absorption spectroscopic measurements reveal high triplet quantum yields of ∼86% for and ∼81% for . Through studies, we demonstrate that the derivatives can be used as photodynamic therapy (PDT) agents, providing a highly efficient form of cancer therapy. This study is the first demonstration of simple organic molecules with CPL from upper-excited states and efficient PDT.