Figure 1.

a) Schematic representation of the donor–acceptor (D–A) molecule composed of a phenothiazine donor and a dibenzothiophene‐S,S‐dioxide acceptor (PTZ‐DBTO2).5 b) A 3D structure of the ground state of PTZ‐DBTO2.5 The transparent overlaid structure is the optimised geometry in the S₁ state. c) A simplified energy diagram representing a general schematic of the the up‐conversion of triplet states to a higher energy singlet state. k _rISC is approximately equal to the k _ISC multiplied by a Boltzmann factor determine the number of states with sufficient energy to overcome barrier (ΔE ${}_{S{}_1-T{}_1}$ ). Deviations from this relationship arise from a higher density of final states expected for the direct intersystem crossing case.6