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

A system demonstrating Nitric Oxide (NO) activated Triplet-Triplet Annihilation (TTA) upconversion has been devised, based on a substituted [Ru II (bpy) 3 ](PF 6 ) 2 complex (bpy = 2,2′-dipyridine) bearing a single 1,2-diaminophenyl moiety as an NO activatable triplet photosensitizer ( Ru-1 ), and 9...

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Bibliographic Details
Published in:Photochemical & photobiological sciences 2016-01, Vol.15 (8), p.995-1005
Main Authors: Xu, Kejing, Zhao, Jianzhang, Moore, Evan G.
Format: Article
Language:English
Subjects:
Anthracenes - chemistry
Biochemistry
Biomaterials
Chemistry
Coordination Complexes - chemistry
Electrochemical Techniques
Electron Transport
Lasers, Solid-State
Nitric Oxide - chemistry
Oxygen - chemistry
Photolysis - radiation effects
Photosensitizing Agents - chemistry
Physical Chemistry
Plant Sciences
Quantum Theory
Ruthenium - chemistry
Spectrometry, Fluorescence
Temperature
Thermodynamics
Time Factors
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Summary:A system demonstrating Nitric Oxide (NO) activated Triplet-Triplet Annihilation (TTA) upconversion has been devised, based on a substituted [Ru II (bpy) 3 ](PF 6 ) 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 ( Φ T ∼ 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/O 2 , 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 .
ISSN:1474-905X
1474-9092
DOI:10.1039/c6pp00153j