Akin to the phenomenon in triplet statesthe S 2 /S 1 states in the para isomer are energetically distinct compared to those in the ortho and meta isomers (see Figure ). In summary, both 2-TP and 3-TP provide possibility of vibronic couplings in singlet and triplet multiplicities, which could enhance the spin-orbit coupling and facilitate the ISC dynamics. In contrast, no such evidence is observed for 4-TP, resulting in a slower rate of triplet crossing and a lower triplet population.