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Near-infrared to Violet Triplet-Triplet Annihilation Fluorescence Upconversion of Os(ii) Complexes by Strong Spin-Forbidden Transition

Near-infrared to Violet Triplet-Triplet Annihilation Fluorescence Upconversion of Os(ii) Complexes by Strong Spin-Forbidden Transition

Yaxiong Wei, Min Zheng, Lin Chen, Xiaoguo Zhou, Shilin Liu

Dalton Trans. 2019 Aug 21;48(31):11763-11771.

PMID: 31298244

Abstract:

Three Os(ii) complexes were synthesized with ligands 2,2'-dipyridyl (dipy), 1,10-phenanthroline monohydrate (phen), and 4,7-diphenyl-1,10-phenanthroline (diphen), and applied as triplet photosensitizers for triplet-triplet annihilation (TTA) fluorescence upconversion. The strong spin-orbital coupling made direct spin-forbidden transition of S0-T1 feasible. Lifetimes of the lowest triplet state of these complexes were determined to be 107 ns, 373 ns, and 386 ns for Os-dipy, Os-phen, and Os-diphen, respectively, using nanosecond transient absorption spectra. From steady-state phosphorescence emission spectra, energies of the triplet states were derived to be 1.75 eV, 1.80 eV, and 1.74 eV for Os-dipy, Os-phen, and Os-diphen, respectively. Using these photosensitizers, strong upconverted fluorescence of the triplet acceptors, 9,10-diphenylanthracene (DPA), perylene, and 9,10-bis(phenethynyl) anthracene (BPEA), was observed in the visible to violet range. In particular, fluorescence emission with the largest anti-Stokes shift of 1.14 eV was observed for the Os-phen/DPA system, and the upconverted quantum yield was determined as 5.9% in deoxygenated dichloroethane. Additionally, upconversion was determined in air using mixtures of dichloroethane and DMSO solvents, and the maximal quantum yield was measured to be 4.5% for Os-phen/DPA.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP5144898	1,10-Phenanthroline monohydrate		5144-89-8	Price

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