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Xianfu Zhang - One of the best experts on this subject based on the ideXlab platform.
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can bodipy electron acceptor conjugates act as heavy atom free Excited Triplet State and singlet oxygen photosensitizers via photoinduced charge separation charge recombination mechanism
Journal of Physical Chemistry C, 2019Co-Authors: Mingyu Liu, Xianfu Zhang, Yaling Wang, Yun Wang, Haikuo Lan, Huaqing ZhaoAbstract:To examine if BODIPY-electron acceptor conjugates can generate Excited Triplet State and singlet oxygen efficiently via a photoinduced charge separation–charge recombination (CS-CR) mechanism, seve...
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bisbodipy as pct based halogen free photosensitizers for highly efficient Excited Triplet State and singlet oxygen formation tuning the efficiency by different linking positions
Dyes and Pigments, 2017Co-Authors: Xianfu ZhangAbstract:Abstract Four covalent BODIPY hetero-dimers, formed by different linking positions at (2,2′), (2,8′), (3,8′) and (8,8′) respectively, were designed and synthesized to compare their ability for Excited Triplet State (T1) and singlet oxygen generation. In contrast to BODIPY monomers that show negligible photosensitizing ability, the four dimers are very efficient for T1 and singlet oxygen formation depending on the individual linking style and solvent polarity. Laser flash photolysis, time-resolved/steady State fluorescence, quantum chemical calculation and thermodynamic analysis revealed that the mechanism of Triplet State T1 formation is different from the traditional intersystem crossing mechanism. The T1 formation is due to charge recombination of the twisted charge separation State (TCSS), while the TCSS is generated by photoinduced intramolecular charge transfer (PCT) from one BODIPY monomer moiety to another within the dimer. The PCT based photosensitizers are also medium polarity sensitive which may be very useful in designing and synthesizing of photosensitizers for photodynamic therapy of tumor, photobiology and organic photochemistry.
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pet based bisbodipy photosensitizers for highly efficient Excited Triplet State and singlet oxygen generation tuning photosensitizing ability by dihedral angles
Physical Chemistry Chemical Physics, 2017Co-Authors: Xianfu Zhang, Xudong YangAbstract:Herein, four covalent BODIPY heterodimers that differ by dihedral angles were shown to be highly efficient Excited Triplet State (T1) photosensitizers (PSs) for singlet oxygen formation with a quantum yield (ΦΔ) of up to 0.94 as compared to their respective monomers, which had only negligible ΦΔ of ca. 0.060. More interestingly, these PSs generate T1via charge recombination mechanism rather than traditional inter-system crossing. The photosensitizing ability of dimers is easily tuned by either the dihedral angle (between the two linked BODIPYs) or solvent polarity. Laser flash photolysis, time-resolved and steady State fluorescence, quantum chemical calculation, as well as thermodynamic analysis were employed to study the associated photophysical process to reveal the T1 formation mechanism: photo-induced electron transfer (PET) followed by charge recombination. Due to its heavy-atom-free nature, polarity selectivity, high efficiency, and easy tunability, this PET-based PS and its mechanism are very useful in developing new PS for photodynamic therapy of tumors, photobiology, and organic photochemistry.
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photoinduced electron transfer based halogen free photosensitizers covalent meso aryl phenyl naphthyl anthryl and pyrenyl as electron donors to effectively induce the formation of the Excited Triplet State and singlet oxygen for bodipy compounds
Chemistry-an Asian Journal, 2017Co-Authors: Xianfu Zhang, Nan FengAbstract:Pristine BODIPY compounds have negligible efficiency to generate the Excited Triplet State and singlet oxygen. In this report, we show that attaching a good electron donor to the BODIPY core can lead to singlet oxygen formation with up to 58 % quantum efficiency. For this purpose, BODIPYs with meso-aryl groups (phenyl, naphthyl, anthryl, and pyrenyl) were synthesized and characterized. The fluorescence, Excited Triplet State, and singlet oxygen formation properties for these compounds were measured in various solvents by UV/Vis absorption, steady-State and time-resolved fluorescence methods, as well as laser flash photolysis technique. In particular, the presence of anthryl and pyrenyl showed substantial enhancement on the singlet oxygen formation ability of BODIPY with up to 58 % and 34 % quantum efficiency, respectively, owing to their stronger electron-donating ability. Upon the increase in singlet oxygen formation, the fluorescence quantum yield and lifetime values of the aryl-BODIPY showed a concomitant decrease. The increase in solvent polarity enhances the singlet oxygen generation but decreases the fluorescence quantum yield. The results are explained by the presence of intramolecular photoinduced electron transfer from the aryl moiety to BODIPY core. This method of promoting T1 formation is very different from the traditional heavy atom effect by I, Br, or transition metal atoms. This type of novel photosensitizers may find important applications in organic oxygenation reactions and photodynamic therapy of tumors.
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bodipy photosensitizers based on pet and heavy atom effect a comparative study on the efficient formation of Excited Triplet State and singlet oxygen in bodipy dimers and monomers
Journal of Photochemistry and Photobiology A-chemistry, 2017Co-Authors: Xianfu ZhangAbstract:Abstract Covalent dimerization and iodine substitution methods were used to synthesize heavy atom free and heavy atom present BODIPY singlet oxygen photosensitizers. Both dimerization and iodization could strongly enhance the Excited Triplet State (T 1 ) formation up to 95% efficiency. The mechanism for Excited Triplet State formation was revealed by examining UV–vis electronic absorption, steady State and time resolved visible and NIR luminescence, laser flash photolysis, singlet oxygen chemical trapping, and quantum chemical calculation. The dimerization method shows a different mechanism in T 1 generation: photoinduced electron transfer (PET) from lowest lying Excited singlet State (S 1 ) followed by charge recombination, instead of the traditional intersystem crossing from S 1 State. The PET mechanism makes such a photosensitizer sensitive to solvent polarity. This type of heavy atom free and PET-based photosensitizers could be important in photodynamic therapy of tumor and organic photochemistry.
Hilkka I Kenttamaa - One of the best experts on this subject based on the ideXlab platform.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reactions occur from the lowest-energy Excited Triplet States, which has not been observed (or reported) for other meta-benzyne analogues. Quantum chemical calculations indicate that the (Excited) Triplet States are stronger Bronsted acids than their (ground) singlet States, likely due to unfavorable three-center, four-electron interactions in the singlet-State conjugate bases. The cations have substantially smaller (calculated) singlet-Triplet (S-T) splittings (ranging from ca. -11 to -17 kcal mol-1) than other related meta-benzyne analogues (e.g., -23.4 kcal mol-1 for the 3,5-isomer). This is rationalized by the destabilization of the singlet States (relative to the Triplet States) by reduced (spatial) overlap of the nonbonding molecular orbitals due to the presence of the nitrogen atom between the radical sites (making the ring more rigid). Both the singlet and Triplet States are believed to be generated upon formation of these biradicals via energetic collisions due to their small S-T splittings. It appears that once the Triplet States are formed, the rate of proton transfer is faster than the rate of intersystem crossing unless the biradicals contain heavy atoms.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reaction...
Erlu Feng - One of the best experts on this subject based on the ideXlab platform.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reactions occur from the lowest-energy Excited Triplet States, which has not been observed (or reported) for other meta-benzyne analogues. Quantum chemical calculations indicate that the (Excited) Triplet States are stronger Bronsted acids than their (ground) singlet States, likely due to unfavorable three-center, four-electron interactions in the singlet-State conjugate bases. The cations have substantially smaller (calculated) singlet-Triplet (S-T) splittings (ranging from ca. -11 to -17 kcal mol-1) than other related meta-benzyne analogues (e.g., -23.4 kcal mol-1 for the 3,5-isomer). This is rationalized by the destabilization of the singlet States (relative to the Triplet States) by reduced (spatial) overlap of the nonbonding molecular orbitals due to the presence of the nitrogen atom between the radical sites (making the ring more rigid). Both the singlet and Triplet States are believed to be generated upon formation of these biradicals via energetic collisions due to their small S-T splittings. It appears that once the Triplet States are formed, the rate of proton transfer is faster than the rate of intersystem crossing unless the biradicals contain heavy atoms.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reaction...
Hui Liu - One of the best experts on this subject based on the ideXlab platform.
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upper Excited Triplet State mediated intersystem crossing for anti kasha s fluorescence potential application in deep ultraviolet sensing
Journal of Physical Chemistry C, 2019Co-Authors: Xianfeng Qiao, Yulong Liu, Jingwen Yao, Hui LiuAbstract:Owing to the Kasha rule, only the lowest Excited State S1 contributes to the photoemission or other photoinduced processes in general, causing a waste of photoenergy and the limitation of applicati...
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Upper Excited Triplet State-Mediated Intersystem Crossing for Anti-Kasha’s Fluorescence: Potential Application in Deep-Ultraviolet Sensing
2019Co-Authors: Xianfeng Qiao, Yulong Liu, Jingwen Yao, Hui LiuAbstract:Owing to the Kasha rule, only the lowest Excited State S1 contributes to the photoemission or other photoinduced processes in general, causing a waste of photoenergy and the limitation of application scenarios. The anti-Kasha effect offers the possibility of utilizing high-energy Excited States Sn to develop novel functions and applications. Here, an anti-Kasha fluorescence has been experimentally found in a pure organic molecule and investigated in detail to reveal the underlying mechanism. The experimental lines of evidence of the excitation mapping spectrum and time-resolved photoluminescence spectrum suggest that the anti-Kasha emission is governed by an upper Excited Triplet State Tn. Intersystem crossing (ISC) from S5 to Tn can successfully compete with internal conversion, followed by reverse ISC from Tn to S2 to form upper-State emission. Further, utilizing this effect for the deep-ultraviolet light sensor is discussed. These findings provide keen insights into manipulating the Excited-State evolution, while offering the possibility for utilizing the high-energy Excited States to explore novel functions and applications of organic molecules
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upper Excited Triplet State mediated intersystem crossing for anti kasha s fluorescence potential application in deep ultraviolet sensing
The Journal of Physical Chemistry, 2019Co-Authors: Xianfeng Qiao, Yulong Liu, Jingwen Yao, Hui LiuAbstract:Owing to the Kasha rule, only the lowest Excited State S₁ contributes to the photoemission or other photoinduced processes in general, causing a waste of photoenergy and the limitation of application scenarios. The anti-Kasha effect offers the possibility of utilizing high-energy Excited States Sₙ to develop novel functions and applications. Here, an anti-Kasha fluorescence has been experimentally found in a pure organic molecule and investigated in detail to reveal the underlying mechanism. The experimental lines of evidence of the excitation mapping spectrum and time-resolved photoluminescence spectrum suggest that the anti-Kasha emission is governed by an upper Excited Triplet State Tₙ. Intersystem crossing (ISC) from S₅ to Tₙ can successfully compete with internal conversion, followed by reverse ISC from Tₙ to S₂ to form upper-State emission. Further, utilizing this effect for the deep-ultraviolet light sensor is discussed. These findings provide keen insights into manipulating the Excited-State evolution, while offering the possibility for utilizing the high-energy Excited States to explore novel functions and applications of organic molecules.
John J Nash - One of the best experts on this subject based on the ideXlab platform.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reactions occur from the lowest-energy Excited Triplet States, which has not been observed (or reported) for other meta-benzyne analogues. Quantum chemical calculations indicate that the (Excited) Triplet States are stronger Bronsted acids than their (ground) singlet States, likely due to unfavorable three-center, four-electron interactions in the singlet-State conjugate bases. The cations have substantially smaller (calculated) singlet-Triplet (S-T) splittings (ranging from ca. -11 to -17 kcal mol-1) than other related meta-benzyne analogues (e.g., -23.4 kcal mol-1 for the 3,5-isomer). This is rationalized by the destabilization of the singlet States (relative to the Triplet States) by reduced (spatial) overlap of the nonbonding molecular orbitals due to the presence of the nitrogen atom between the radical sites (making the ring more rigid). Both the singlet and Triplet States are believed to be generated upon formation of these biradicals via energetic collisions due to their small S-T splittings. It appears that once the Triplet States are formed, the rate of proton transfer is faster than the rate of intersystem crossing unless the biradicals contain heavy atoms.
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protonated ground State singlet meta pyridynes react from an Excited Triplet State
Journal of Organic Chemistry, 2021Co-Authors: Erlu Feng, Hanning Jiang, Victoria M Boulos, Jinshan Gao, John J Nash, Hilkka I KenttamaaAbstract:The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground States is too endothermic to be observed. These reaction...