title: Photo-induced electron transfer in a diamino-substituted Ru(bpy)3[PF6]2 complex and its application as a triplet photosensitizer for nitric oxide (NO)-activated triplet-triplet annihilation upconversion.
abstract: A system demonstrating Nitric Oxide (NO) activated Triplet-Triplet Annihilation (TTA) upconversion has been devised, based on a substituted [Ru(II)(bpy)3](PF6)2 complex (bpy = 2,2'-dipyridine) bearing a single 1,2-diaminophenyl moiety as an NO activatable triplet photosensitizer (Ru-1), and 9,10-diphenylanthracene (DPA) as a triplet acceptor/emitter. The excited triplet state of Ru-1 is significantly quenched (ΦT∼ 22%) by a Photoinduced Electron Transfer (PET) reaction, as confirmed by steady state phosphorescence and transient absorption spectroscopy, and hence Ru-1 does not function as a TTA upconversion sensitizer. However, in the presence of NO/O2, the 1,2-diaminophenyl group of Ru-1 is transformed into a benzotriazole. This inhibits PET, and the triplet state quantum yield is increased to ca. 85%, switching on the TTA upconversion process which increases by 10-fold. These processes were studied using a combination of steady state and time-resolved luminescence together with transient absorption spectroscopy on the nanosecond and femtosecond timescales. The energy level of the charge transfer state (CTS) for Ru-1 was also obtained electrochemically, supporting the PET mechanism of triplet state quenching and hence the lack of TTA upconversion with Ru-1.
authors.affiliation: State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Rd., Dalian 116024, P. R. China. zhaojzh@dlut.edu.cn.
authors.forename: Kejing
authors.initials: K
authors.lastname: Xu
authors.forename: Jianzhang
authors.initials: J
authors.lastname: Zhao
authors.forename: Evan G
authors.initials: EG
authors.lastname: Moore
mesh_terms: D000873:Anthracenes / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D055664:Electrochemical Techniques; D004579:Electron Transport; D053844:Lasers, Solid-State; D009569:Nitric Oxide / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D010782:Photolysis / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000737:chemistry*; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D000873:Anthracenes; D056831:Coordination Complexes; D017319:Photosensitizing Agents; D009569:Nitric Oxide; C046961:9,10-diphenylanthracene; D012428:Ruthenium; D010100:Oxygen