Intramolecular triplet-triplet energy transfer enhanced triplet-triplet annihilation upconversion with a short-lived triplet state platinum(II) terpyridyl acetylide photosensitizer

摘要

A model of a dendritic compound (Pt-DPA) with two Pt-complex photosensitizer chromophores and two 9,10-diphenylanthracene (DPA) acceptor groups covalently attached to the periphery and the core of the poly(aryl ether) dendrimer of generation 1 was prepared. A triplet-triplet annihilation upconversion (TTA-UC) system (Pt-DPA/DPA-OH) was constructed in deaerated DMF by combining Pt-DPA with a dissociative acceptor (DPA-OH). Although the lifetime of the triplet state of the Pt-complex is only 52 ns, the upconversion fluorescence from DPA (400-460 nm) in the Pt-DPA/DPA-OH system was observed with a quantum yield of 0.22% upon selective excitation of the Pt-complex with a 473 nm laser, which is due to the efficient intramolecular triplet-triplet energy transfer (Phi(TTET) > 0.81) from the Pt-complex photosensitizer to the DPA acceptor within Pt-DPA. The acceptor covalently linked with the photosensitizer acts as an energy-relay to transfer the harvested energy to the dissociative acceptor which further undergoes the TTA process. The efficient intramolecular triplet-triplet energy transfer process between the photosensitizer and the acceptor plays an important role in the TTA-UC system building with a short-lived triplet state photosensitizer, which facilitates the production of the triplet state of the acceptor, thus advancing the TTA-UC process. This work presents a new strategy for construction of efficient TTA-UC systems utilizing short-lived triplet state photosensitizers.