| Following light excitation of acridine to the first excited triplet state T1 by H-transfer from fluorene the |
| the radical pair triplet state TRP can be formed. The radical pair quickly decays back to the educt ground |
| states. The intermolecular guest/host H-transfer reaction is observed between acridine and fluorene |
| molecules occupying the transitionally equivalent positions A and A' within the fluorene crystal |
| ab-plane. From the reaction geometry the distance of H-transfer corresponds to 2.55 Å. View also the |
| diagram of the energy levels involved showing the transitions relevant for the H-transfer. |