Singlet and triplet energy transfer dynamics in self-assembled axial porphyrin–anthracene complexes: towards supra-molecular structures for photon upconversion

Abstract

Energy and electron transfer reactions are central to many different processes and research fields, from photosynthesis and solar energy harvesting to biological and medical applications. Herein we report a comprehensive study of the singlet and triplet energy transfer dynamics in porphyrin-anthracene coordination complexes. Seven newly synthesized pyridine functionalized anthracene ligands, five with various bridge lengths and two dendrimer structures containing three and seven anthracene units, were prepared. We found that triplet energy transfer from ruthenium octaethylporphyrin to an axially coordinated anthracene is possible, and is in some cases followed by back triplet energy transfer to the porphyrin. The triplet energy transfer follows an exponential distance dependence with an attenuation factor, β, of 0.64 Å. Further, singlet energy transfer from anthracene to the ruthenium porphyrin appears to follow a R Förster distance dependence. Porphyrin-anthracene complexes are also used as triplet sensitizers for triplet-triplet annihilation (TTA) based photon upconversion, demonstrating their potential for photophysical and photochemical applications. The triplet lifetime of the complex is extended by the anthracene ligands, resulting in a threefold increase in the upconversion efficiency, Φ to 4.5%, compared to the corresponding ruthenium porphyrin-pyridine complex. Based on the results herein we discuss the future design of supra-molecular structures for TTA upconversion.

Intramolecular Triplet–Triplet Annihilation Photon Upconversion in Diffusionally Restricted Anthracene Polymer

“…The fitted triplet lifetime of DPA is surprisingly short compared to other reported values, which are in the millisecond time range. 24 , 27 , 39 The short fitted triplet lifetime can be explained by the unusually high sensitizer concentration which governs endothermic TET from the annihilator back to the PtOEP sensitizer, 21 , 42 , 43 see Supporting Information section 5 for details. The fitted values of β for TPBAP and DPA at various excitation intensities are shown in Figure 6 .…”

Development of the sensitizer for generating higher-energy photons under diluted condition via the triplet-triplet annihilation-supported upconversion

“…23 By connecting emitters, improvement of upconversion efficiencies was observed. [30][31][32][33][34] Various assembly systems have been accomplished with good upconversion efficiencies [35][36][37][38][39][40][41][42][43] even in aqueous media by molecular assembling. [44][45][46][47][48] Moreover, by connecting the triplet sensitizer with aromatic units, the lifetime at the triplet-excited state can be efficiently elongated.…”

The Role of Polyhedral Oligomeric Silsesquioxanes in Optical Applications

“…For example, POSS‐based porphyrin and anthracene systems have been investigated for applications in PDT and ion sensing but have not been extensively investigated for upconversion by triplet–triplet annihilation (TTA), despite these being common sensitizer–emitter pairs. [ 122–124 ] TTA requires careful placement of sensitizer–emitter pairs for which the templating potential of POSS could prove useful. There is also opportunity within the field of optoelectronic devices, especially for LEDs, where a number of promising POSS‐containing light‐emitting materials have been identified, although devices have not been optimized.…”