We can explain the more efficient rISC observed experimentally for 2 through the larger presence of states with high SOC. Firstly, 2 has three LE triplets (T13, T14 and T15) that exhibit appreciable SOCMEs with S1. Secondly, due to electronic coupling between the fins of 2, it is possible to localise CT states across neighbouring fins (Figure ). This is apparent for the T8 state which is localised differently to S1. T8 is a CT state with the hole predominantly localised on the phenoxazine moieties of fin A, and the electron mainly on the quinoxaline heterocycles of fins B and C with some bridging A contribution. Conversely, for S1 both the electron and hole are predominantly localised over fin A with some electron density extending onto the quinoxalines of B and C. These distinct differences in the localisation of S1 and T8, can translate into a change in orbital angular momentum between the two states, but they crucially retain some spatial overlap over the homoconjugated core of 2. This enables a large SOCME value of 0.9 cm -1 between the CT states S1 and T8, which are predicted to be only 0.17 eV apart in energy (Table ). A significant SOCME is also predicted between S1 and T7 (0.29 cm -1 ), which is a CT state degenerate with T8 also spread across multiple fins (Table , Figure .18).