Pd–Porphyrin Oligomers Sensitized for Green‐to‐Blue Photon Upconversion: The More the Better?. Issue 25 (3rd May 2016)

• Record Type: Journal Article
• Authors: Xun, Zhiqing; Zeng, Yi; Chen, Jinping; Yu, Tianjun; Zhang, Xiaohui; Yang, Guoqiang; Li, Yi
• Is Part Of: Chemistry. Volume 22:Issue 25(2016)
• Page Start: 8654
• Page End: 8662
• Publication Date: 2016-05-03
• Subjects: energy transfer -- light harvesting -- sensitizers -- triplet–triplet annihilation -- upconversion; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201504498
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A series of directly meso ‐ meso ‐linked Pd–porphyrin oligomers (PdDTP‐M, PdDTP‐D, and PdDTP‐T) have been prepared. The absorption region and the light‐harvesting ability of the Pd–porphyrin oligomers are broadened and enhanced by increasing the number of Pd–porphyrin units. Triplet–triplet annihilation upconversion (TTA‐UC) systems were constructed by utilizing the Pd–porphyrin oligomers as the sensitizer and 9, 10‐diphenylanthracene (DPA) as the acceptor in deaerated toluene and green‐to‐blue photon upconversion was observed upon excitation with a 532 nm laser. The triplet–triplet annihilation upconversion quantum efficiencies were found to be 6.2 %, 10.5 %, and 1.6 % for the [PdDTP‐M]/DPA, [PdDTP‐D]/DPA, and [PdDTP‐T]/DPA systems, respectively, under an excitation power density of 500 mW cm −2 . The photophysical processes of the TTA‐UC systems have been investigated in detail. The higher triplet–triplet annihilation upconversion quantum efficiency observed in the [PdDTP‐D]/DPA system can be rationalized by the enhanced light‐harvesting ability of PdDTP‐D at 532 nm. Under the same experimental conditions, the [PdDTP‐D]/DPA system produces more 3 DPA* than the other two TTA‐UC systems, benefiting the triplet–triplet annihilation process. This work provides a useful way to develop efficient TTA‐UC systems with broad spectral response by using Pd–porphyrin oligomers as sensitizers. Abstract : Annihilating triplets : Triplet–triplet annihilation upconversion systems are constructed by utilizing Pd–porphyrin oligomers with broadened and enhanced absorption as the sensitizer and 9, 10‐diphenylanthracene (DPA) as the acceptor. Detailed photophysical investigations reveal that the enhanced light‐harvesting ability of the dimer benefits the triplet–triplet annihilation process (see figure).