Electronic to vibrational energy conversion and charge transfer contributions during quenching by molecular oxygen of electronically excited triplet statesDedicated to Professor Frank Wilkinson on the occasion of his retirement.

Abdel-Shafi, Ayman A.; Wilkinson, Frances

doi:10.1039/b108272h

Cited by 47 publications

(110 citation statements)

References 31 publications

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“…Later Wilkinson and Garner found that charge‐transfer (CT) interactions between T 1 excited sensitizer and O 2 lead to a strong increase of k T Q in the region of high values of E T (15). Further investigations of the same group demonstrated that for sensitizers of high and almost constant triplet energy values of k T Q increase and those of SΔ decrease with decreasing sensitizer oxidation potential E ox , indicating the competition of a CT and a non‐CT pathway in the quenching of triplet states by O 2 (16–24). Interestingly, both pathways contribute to the formation of O 2 (1Δ g ).…”

Section: Discussionmentioning

confidence: 97%

Photosensitized Generation of Singlet Oxygen

Schmidt

2007

Photochemistry and Photobiology

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This work gives an overview of what is currently known about the mechanisms of the photosensitized production of singlet oxygen. Quenching of ππ* excited triplet states by O2 proceeds via internal conversion of excited encounter complexes and exciplexes of sensitizer and O2. Both deactivation channels lead with different efficiencies to singlet oxygen generation. The balance between the deactivation channels depends on the triplet‐state energy and oxidation potential of the sensitizer, and on the solvent polarity. A model has been developed that reproduces rate constants and efficiencies of the competing processes quantitatively. Sensitization by excited singlet states is much more complex and hence only qualitative rules could be elaborated, despite serious efforts of many groups. However, the most important deactivation paths of fluorescence quenching by O2 are again directed by excess energies and charge‐transfer interactions similar to triplet‐state quenching by O2. Finally, two recent developments in photo‐sensitization of singlet oxygen are reviewed: Two‐photon sensitizers with particular application potential for photodynamic therapy and fluorescence imaging of biological samples and singlet oxygen sensitization by nanocrystalline porous silicon, a material with very different photophysics compared to molecular sensitizers.

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Section: Discussionmentioning

confidence: 97%

Photosensitized Generation of Singlet Oxygen

Schmidt

2007

Photochemistry and Photobiology

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“…Figure 3 shows a plot of the half-wave oxidation potential of the aryl residues [51,52] (see Table 2) versus the energies that correspond to the LW maximum. Figure 3 shows a plot of the half-wave oxidation potential of the aryl residues [51,52] (see Table 2) versus the energies that correspond to the LW maximum.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 3 shows a plot of the half-wave oxidation potential of the aryl residues [51,52] (see Table 2) versus the energies that correspond to the LW maximum. On the other hand, compound 2, which contained a hard-to-oxidize 4-cyanonaphthyl residue (E 1/2 (ox) = 2.01 V versus SCE in MeCN), [52] had its only emission band at 437 nm. For example, compound 6, which contained a 4-(N,N-dimethylamino)naphthyl moiety (E 1/2 (ox) = 0.75 V versus SCE in MeCN), [51] showed the most red-shifted emission, with l max = 608 nm.…”

Section: Introductionmentioning

confidence: 99%

Borylated Arylisoquinolines: Photophysical Properties and Switching Behavior of Promising Tunable Fluorophores

Pais

El‐Sheshtawy

Fernández

et al. 2013

Chemistry A European J

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A series of nine borylated arylisoquinolines has been prepared with systematic variation in their electronic properties and their photophysical properties were investigated. The color of their fluorescence can be finely tuned by changing the properties of the aryl moiety, which is involved in internal-charge-transfer processes. For example, methoxy-substituted compound 5 showed an intense green emission, whereas dimethylamino-substituted compound 6 showed an orange-red emission. These new fluorophores were tested for their potential as molecular switches with external ionic stimuli, such as protons and fluoride ions. On the one hand, protonation of the isoquinoline moiety led to fluorescence enhancement for compounds that showed weak charge transfer and fluorescence quenching for compounds that showed strong charge transfer. On the other hand, the formation of ate complexes with fluoride led to strong fluorescence quenching in all of the investigated cases.

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“…S8, ESI †). 24,25 The largest production of singlet oxygen was detected in o-xylene (F D = 0.16), the less polar solvent, followed by THF (F D = 0.13). Notably, comparison of these figures with F in the same apolar solvents indicated that intersystem crossing to triplet accounts for a large fraction of the non-radiative depopulation of the singlet excited state.…”

Section: Characterization Of the Tpap Triplet Statementioning

confidence: 99%

A fluorescent molecular rotor showing vapochromism, aggregation-induced emission, and environmental sensing in living cells

et al. 2016

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Among the plethora of recently proposed molecular sensors, those belonging to the class of fluorescent molecular rotors (FMRs) have attracted much attention owing to their peculiar photophysical properties that enable an unprecedented sensitivity towards environmental microviscosity. The usual FMR synthetic design prescribes chromophores characterized by an intramolecular rotation between two well-defined excited states, a locally excited state and a twisted internal charge transfer (TICT) state, where the sensing capabilities arise from a dual competition of the corresponding radiative/non-radiative decay processes. However, we have recently demonstrated a different modus operandi of a new subclass of solvatochromic FMRs, which exploit a solvent-independent, barrier-free intramolecular rotation of the excited dye. The rotational dynamics is modulated by local viscosity and, in turn, manifested through a variable spectral signal. In order to translate the same rotational mechanism in a versatile sensor of polarity and viscosity, we designed and thoroughly characterized a novel FMR, namely 4-(triphenylamino)-phthalonitrile (TPAP). Remarkably, in addition to a high sensitivity versus solvent polarity and viscosity, TPAP is also able to form stable fluorescent nanoparticles characterized by aggregation-induced emission, via a simple sonochemical treatment. Such peculiar features are tested in different applications aiming at illustrating its capability to report on solvatochromic and vapochromic effects, as well as to provide detailed intracellular information through bioimaging studies.

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Electronic to vibrational energy conversion and charge transfer contributions during quenching by molecular oxygen of electronically excited triplet statesDedicated to Professor Frank Wilkinson on the occasion of his retirement.

Cited by 47 publications

References 31 publications

Photosensitized Generation of Singlet Oxygen

Photosensitized Generation of Singlet Oxygen

Borylated Arylisoquinolines: Photophysical Properties and Switching Behavior of Promising Tunable Fluorophores

A fluorescent molecular rotor showing vapochromism, aggregation-induced emission, and environmental sensing in living cells

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