Porphyrin–Anthracene Complexes: Potential in Triplet–Triplet Annihilation Upconversion

Abstract

Triplet−triplet annihilation photon upconversion (TTA-UC) systems contain both an absorbing and an emitting molecule, the sensitizer and annihilator, respectively. Through a series of energy-transfer steps, two low frequency photons can be combined into one high frequency photon. In organic solvents, the required energy transfer steps are limited by diffusion and are relatively efficient. In solid-state systems, however, the diffusion is slower, which usually results in lower efficiencies for these systems. An interesting way around this is to connect the sensitizer and annihilator. In order to increase understanding of the TTA-UC process in supramolecular systems, we synthesized four pyridine-substituted anthracene annihilators capable of coordinating axially to a zinc octaethylporphyrin sensitizer with a maximum binding constant of 6000 M −1 in toluene. This is a first example of a sensitizer−annihilator coordination complex for TTA-UC. Both the upconversion efficiency and the parasitic quenching of excited annihilator singlets by the sensitizer through Forster resonant energy transfer (FRET) were studied. On the basis of the findings herein, possible strategies for future supramolecular TTA systems with minimized FRET quenching are discussed.

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

“…Ligand design is based on our previous work with 9,10-diphenylanthracene (DPA) based ligands and dendrimeric structures. 25,45 Fig. 1 shows the structures of the ligands: ligand 1 has a metapyridine substitution, ligands 2-5 have para-pyridine substitutions with increasing bridge lengths and dendrimeric ligands 6 and 7 have an increasing number of DPA monomer units.…”

“…The synthesis of ligands 1-5 was reported previously. 25 The dendrimer ligands were synthesized by repeating a sequence of three high yielding and simple reactions; bromination followed by borylation followed by a Suzuki-coupling, similar to our previously established route for DPA dendrons and dendrimers. 45 The synthetic route is illustrated in Fig.…”

“…[22][23][24] Engineered photosynthetic systems with increased efficiencies will require even greater oxygen protection, motivating further exploration of TET in model porphyrin donor-acceptor systems. 24 Furthermore, in the development of supramolecular structures designed for photochemical applications, such as triplet-triplet annihilation based photon upconversion [25][26][27] or photocatalysis [28][29][30] the delicate balance between energy and electron transfer reactions requires careful tuning.…”

“…As part of the ongoing studies of energy and electron transfer reactions in porphyrin donor-acceptor system for various photochemical and electrochemical applications, 4,5,7,24,25,[31][32][33][34][35][36][37][38][39][40][41][42][43][44] we present a detailed photophysical study of a series of new, well-defined, self-assembled, axially coordinated ruthenium porphyrin-anthracene donor-acceptor systems. These systems consist of 2,3,7,8,12,13,17,18-octaethylporpyrin ruthenium(II) carbonyl (RuOEP(CO)) coordinated axially by five different pyridine functionalized anthracene based ligands with various bridge lengths (8-25 Å) or two different dendrimer ligands with 3-7 monomer units.…”

Enhanced phosphorescence properties of a Pt-porphyrin derivative fixed on the surface of nano-porous glass

“…Some chromophores like metalloporphyrins are known to show room-temperature (RT) phosphorescence, which has attracted considerable attention due to various applications such as oxygen [1][2][3][4] and pressure sensors, 4,5 organic light-emitting diodes (OLED), [6][7][8][9][10][11] and sensitizers for wavelength conversion devices [12][13][14][15][16][17] based on triplet-triplet annihilation upconversion (TTA-UC) utilising high triplet quantum yield. Solid materials are preferable for such device applications; however, many RT-phosphorescence chromophores easily aggregate 18 and cause phosphorescence quenching.…”