Abstract
We demonstrate that photoactivated oxygen addition to diphenylanthracene moities can be used as a tool for protection of porphyrin's phosphorescence against oxygen quenching. Phosphorescent palladium(II) tetrabenzoporphyrin, covalently linked to four diphenylanthracene moieties, was synthesized and studied. Upon irradiation with ambient light or red laser in solution in air, addition of oxygen and formation of the corresponding endoperoxides were observed. Heating of the irradiated samples afforded the parent porphyrin material.
Highlights
Organic chromophores able to form triplet excited states upon absorption of light are used in various fields, e.g. electroluminescence,[1] bioimaging and molecular sensing,[2] photocatalytic organic reactions,[3] and triplet–triplet annihilation photon upconversion (TTA-UC).[4]
Organic electronic materials based on triplet sensitizers promise to make revolutionary transformations in solar energy conversion technologies by improving the light-harvesting of amorphous silicon solar cells[5] and extending the infrared limit of oxygenic photosynthesis.[6]
Straightforward embedding of UC-active substances into inert polymer films with high oxygen barrier properties leads to a substantial decrease of the TTA-UC efficiency, because in solid state environments the local mobility of the chromophores involved a significant decrease.[14]
Summary
Organic chromophores able to form triplet excited states upon absorption of light (triplet sensitizers) are used in various fields, e.g. electroluminescence,[1] bioimaging and molecular sensing,[2] photocatalytic organic reactions,[3] and triplet–triplet annihilation photon upconversion (TTA-UC).[4]. The most common process which leads to the loss of triplet excited state population is related to the presence of molecular oxygen in the corresponding samples. Consumption of oxygen results in partial or complete termination of the quenching process that provides emissive relaxation of newly formed triplet states of the Pd-porphyrin core.
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