Photochemical Formation of Metastable Species From 1,3‐diphenylisobenzofuran*

Abstract

Abstract— Photochemical formation of metastable species from 1,3‐diphenylisobenzofuran (DPBF) in solutions has been investigated. On irradiation at 410 nm, in the presence of oxygen, DPBF is bleached. The bleached solutions show two fluorescence bands, one at ˜380nm and the other at ˜420nm. None of these fluorescence bands are due to o‐dibenzoylbenzene, which is the main stable product formed on photo‐bleaching of DPBF in the presence of O2. The species showing fluorescence at ˜380nm and ˜420nm are also formed on reaction of DPBF with 1O2 and undergo further reactions with light as well with 1O2; the resulting products do not all show fluorescence. After the photo‐bleached solutions have stood for some time in the dark, or are warmed, regeneration of DPBF seems to occur. The triplet energy of DPBF has been estimated by energy transfer studies to be between 22 and 29 kcal/mol (between 92 and 121 kJ mol‐1).

Singlet Oxygen Generation by Laser Irradiation of Gold Nanoparticles

“… 37 The oxygen dependence of phase i is in agreement with direct photogeneration of singlet oxygen by visible light, which has been suggested to be the reason for DPBF photobleaching upon irradiation with light at wavelengths above 470 nm. 38 However, the slower phase ii is not affected by removing oxygen from the solution (see Figure S4b and Figure 3 ) and hence cannot be ascribed to singlet oxygen formation. At the present moment, the mechanism of both phases of DPBF photobleaching remains unclear, although both effects are highly reproducible and bleaching does not occur when the sample is not exposed to light (see Figure S4a ).…”

A Family of RuII Photosensitizers with High Singlet Oxygen Quantum Yield: Synthesis, Characterization, and Evaluation

“…To measure the quantum yields of 1 O 2 generation by ruthenium complexes C1 – C3 , we utilized the reaction of the generated 1 O 2 with DPBF, which is a well‐known highly efficient 1 O 2 scavenger 35–39. For this reason, we applied a strategy that combines the procedures reported by the groups of Zhang35,36 and Hoebeke40 with two modifications: (1) we utilized the absorption intensity decrease instead of the luminescence intensity decrease of DPBF, and (2) we fine‐tuned the concentrations of the photosensitizers to achieve almost equal values for the absorption intensity integrations of the sensitizers in the region of the spectra that the analysis is performed.…”

“…The timeframe of the measurements was set to 10 min to obtain linear first‐order curves of DPBF consumption and, furthermore, to have at least 30–40 % absorption intensity remaining at the end of the experiment 38. Equally importantly, this timeframe allows oxygenated solutions of solely DPBF to remain quite steady, independently from the presence of oxygen and low ambient light 39. This procedure is very reliable and is not sensitive to other factors such as (1) the photodegradation of DPBF in the presence of oxygen during the illumination of the samples with light at 400–420 nm or (2) the partial thermal regeneration of DPBF 32,38,39…”

Light‐Induced Generation of Singlet Oxygen by Naked Gold Nanoparticles and its Implications to Cancer Cell Phototherapy

“…It should be noted that the DPBF assay suffers from the autooxidation events of DPBF27, 40 (though this is negligible at irradiation wavelengths above ca. 400 nm) and therefore all results were normalized against suitable controls (SI).…”