Fig. 1. (A) Chemical structures of TPP, 1-Ir and 4-Ir; (B) the calculated excitation energy distributions of singlet (S_n) and triplet (T_n) excited states for TPP, L4, 1-Ir and 4-Ir; (C) the transition charge density differences (CDD) for singlet (S_n) and triplet (T_n) excited states in 4-Ir; (D) the photophysical mechanism for photoactive cancer therapy using PSs; (E) schematic illustration of PSs for in vivo photophysical applications.