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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Veröffentlicht in: | Photochemical & photobiological sciences 2016-01, Vol.15 (8), p.995-1005 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | 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
. |
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ISSN: | 1474-905X 1474-9092 |
DOI: | 10.1039/c6pp00153j |