Benzophenones in the higher triplet excited states.
作者： Xichen Cai , Masanori Sakamoto , Michihiro Hara , Akira Sugimoto , Sachiko Tojo
DOI: 10.1039/B307443A
关键词: Internal conversion (chemistry) 、 Photochemistry 、 Quantum yield 、 Excited state 、 Benzophenone 、 Quenching (fluorescence) 、 Ultrafast laser spectroscopy 、 Chemistry 、 Radical 、 Bond cleavage
摘要: Transient phenomena of benzophenone (BP) in the higher triplet excited state (Tn) have been investigated by two-colour two-laser excitation method. Triplet energy transfer from BP(Tn) to quenchers (Q) occurred within duration a laser pulse (5 ns) give Q(T1) with than that BP(T1). The quantum yield energy-transfer quenching CCl4 was found be 0.0023 ± 0.0002 bleaching transient absorption BP(T1) and absorbed photon number. It appears internal conversion is predominant process. lifetimes (τTn) several substituted benzophenones (BPs) [BPs(Tn)] were estimated dependence Q concentration on efficiency Q, 110–450 ps, depending nature substituents BPs. effect τTn may explained gap between Tn T1 states, because main deactivation pathway for BPs(Tn) In contrast, substituent BPs(T1) cannot law. behaviour depends properties quencher. Sequential BP p-dichlorobenzene tert-butylbenzene as quenchers, while reacted partly form excimers (3Q2*) benzene, chlorobenzene, o-dichlorobenzene quenchers. When used quencher, homolytic cleavage C–Cl bond CCl4(T1) Cl˙ Cl3C˙ radicals.
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