Photo-induced energy transfer in ruthenium-centred polymers prepared by a RAFT approach

Triplet and singlet excitation energy transfer processes are investigated in two novel di- and hexa-functionalised ruthenium centred polymers prepared by RAFT methods. The polymers consist of a ruthenium trisbipyridyl ligand complex (Ru(bpy)3) core and pendant polymer ‘arms’ of 9,10-diphenylanthracene (DPA). Steady state and transient emission and absorption experiments are used to investigate intramolecular energy transfer processes following photoexcitation of Ru(bpy)3 and DPA. Triplet energy transfer from the Ru(bpy)3 core to pendant DPA chromophores in the polymer arms is found to be more efficient than the reverse singlet energy transfer process, attributed in part to the long triplet lifetime of Ru(bpy)3 and the polymer structure. A consequence is that intra-polymer chain triplet energy transfer from Ru(bpy)3 to DPA chromophores followed by triplet–triplet annihilation and delayed fluorescence from the DPA can be observed.