Abstract:The triplet lifetime of 2,3-diazabicyclo[2.2.2]oct-1-ene has been measured, and the triplet energy estimated, by photoacoustic calorimetry. These direct measurements are compared to previous estimates obtained through indirect methods.
“…These methods have been used for the study of the lifetime as well as the triplet state quantum yield. [100][101][102] 2. Formation of the triplet excited state of Bodipy 2.1.…”
Section: Wenbo Yangmentioning
confidence: 99%
“…Electrochemical studies show that the 2,6-diiodoBodipy is more difficult to be oxidized (E ox = 1.13 V vs SCE) than RB (0.89 V vs SCE), thus 2,6-diiodoBodipy is more stable toward 1 O 2 (strong oxidant) than RB. The PDT effect on living HeLa cells was studied, and it was found the cells 100 were killed by photoirradiation after incubation with 2,6-diiodoBodipy. 88 The normal Bodipys give absorption in the green spectra range (ca.…”
Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet-triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Förster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were briefly discussed.
“…These methods have been used for the study of the lifetime as well as the triplet state quantum yield. [100][101][102] 2. Formation of the triplet excited state of Bodipy 2.1.…”
Section: Wenbo Yangmentioning
confidence: 99%
“…Electrochemical studies show that the 2,6-diiodoBodipy is more difficult to be oxidized (E ox = 1.13 V vs SCE) than RB (0.89 V vs SCE), thus 2,6-diiodoBodipy is more stable toward 1 O 2 (strong oxidant) than RB. The PDT effect on living HeLa cells was studied, and it was found the cells 100 were killed by photoirradiation after incubation with 2,6-diiodoBodipy. 88 The normal Bodipys give absorption in the green spectra range (ca.…”
Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet-triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Förster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were briefly discussed.
“…Moreover, its triplet state is too short lived (ca. 25 ns) 36 to investigate quenching by additives, which precludes experimental access to reactivity data. However, some fused DBH derivatives, including DDBH, have recently been found 38 to undergo spontaneous ISC to form sufficiently long-lived triplet states to allow quenching studies and, thus, to examine their bimolecular photoreactivity.…”
The reaction enthalpies for the photoreduction of n,pi*-excited states (acetone, benzophenone, 2.3-diazabicyclo[2.2.2]oct-2-ene, and a 2,3-diazabicyclo[2.2.1]hept-2-ene derivative) by model hydrogen donors (methanol and dimethylamine) were calculated on the basis of a critically evaluated data set of bond dissociation energies for donors and reduced acceptors. These were compared with the observed photoreactivity, which can be assessed through quenching rate constants of the excited states by hydrogen donors. The intriguing observation of a preferential attack at electrophilic hydrogen atoms, i.e., N-H or O-H, by n,pi*-excited azoalkanes is rationalised on the basis of the calculated thermochemical data, differences in electrophilicity, and varying contributions of antibonding character in the transition state. Singlet-excited azoalkanes act as nucleophilic species, while excited ketones display an electrophilic reactivity. This is in line with the pictorial description of the electron distribution in these excited states.
“…The azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) and its derivatives possess the longest fluorescence lifetimes (up to 1 μs) among purely organic compounds. Although the exceptional photophysics of the parent DBO have already been examined 30 years ago, − the interest in this azoalkane has continued over the years − and remains the subject of ongoing investigations. − …”
The fluorescence lifetimes of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) were determined in a large number of
solvents and solvent mixtures, displaying variations from 825 ns in CD3CN to 13 ns in CHCl3. Large deuterium
isotope effects (8−11) and significant activation energies (generally 2−15 kJ mol-1) for fluorescence quenching
of DBO are observed, which support a novel solvent-induced quenching mechanism via an aborted hydrogen
atom transfer. In CCl4 a photoinduced electron-transfer quenching mechanism may compete. The fluorescence
quenching by solvent mixtures is not proportional to the mole fraction of the two components, indicating a
preferential solvation of the excited state.
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