- BENZOXAZOLE DERIVATIVES AND FLUORESCENT MATERIAL COMPRISING THE SAME
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A benzoxazole derivative represented by Structural Formula 1 is provided. Thus, the present invention is not limited thereto. A fluorescent material is provided to remarkably improve fluorescence yield, to have excellent dyeing property and dispersibility, to minimize environmental pollution and to improve economic feasibility. Structural 1.
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- Singlet and Triplet Contributions to the Excited-State Activities of Dihydrophenazine, Phenoxazine, and Phenothiazine Organocatalysts Used in Atom Transfer Radical Polymerization
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The photochemical dynamics of three classes of organic photoredox catalysts employed in organocatalyzed atom-transfer radical polymerization (O-ATRP) are studied using time-resolved optical transient absorption and fluorescence spectroscopy. The nine catalysts selected for study are examples of N-aryl and core-substituted dihydrophenazine, phenoxazine and phenothiazine compounds with varying propensities for control of polymerization outcomes. Excited singlet-state lifetimes extracted from the spectroscopic measurements are reported in N,N-dimethylformamide (DMF), dichloromethane (DCM), and toluene. Ultrafast (200 fs to 3 ps) electronic relaxation of the photocatalysts after photoexcitation at near-UV wavelengths (318-390 nm) populates the first singlet excited state (S1). The S1-state lifetimes range from 130 ps to 40 ns with a considerable dependence on the photocatalyst structure and the solvent. The competition between ground electronic state recovery and intersystem crossing controls triplet state populations and is a minor pathway in the dihydrophenazine derivatives but is of greater importance for phenoxazine and phenothiazine catalysts. A comparison of our results with previously reported O-ATRP performances of the various photoredox catalysts shows that high triplet-state quantum yields are not a prerequisite for controlling polymer dispersity. For example, the photocatalyst 5,10-bis(4-cyanophenyl)-5,10-dihydrophenazine, shown previously to exert good polymerization control, possesses the shortest S1-state lifetime (135 ps in DMF and 180 ps in N,N-dimethylacetamide) among the nine examples reported here and a negligible triplet-state quantum yield. The results call for a re-evaluation of the excited-state properties of most significance in governing the photocatalytic behavior of organic photoredox catalysts in O-ATRP reactions.
- Bhattacherjee, Aditi,Sneha, Mahima,Lewis-Borrell, Luke,Amoruso, Giordano,Oliver, Thomas A.A.,Tyler, Jasper,Clark, Ian P.,Orr-Ewing, Andrew J.
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supporting information
p. 3613 - 3627
(2021/04/07)
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- Structure-property relationships for tailoring phenoxazines as reducing photoredox catalysts
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Through the study of structure-property relationships using a combination of experimental and computational analyses, a number of phenoxazine derivatives have been developed as visible light absorbing, organic photoredox catalysts (PCs) with excited state reduction potentials rivaling those of highly reducing transition metal PCs. Time-dependent density functional theory (TD-DFT) computational modeling of the photoexcitation of N-aryl and core modified phenoxazines guided the design of PCs with absorption profiles in the visible regime. In accordance with our previous work with N,N-diaryl dihydrophenazines, characterization of noncore modified N-aryl phenoxazines in the excited state demonstrated that the nature of the N-aryl substituent dictates the ability of the PC to access a charge transfer excited state. However, our current analysis of core modified phenoxazines revealed that these molecules can access a different type of CT excited state which we posit involves a core substituent as the electron acceptor. Modification of the core of phenoxazine derivatives with electron-donating and electron-withdrawing substituents was used to alter triplet energies, excited state reduction potentials, and oxidation potentials of the phenoxazine derivatives. The catalytic activity of these molecules was explored using organocatalyzed atom transfer radical polymerization (O-ATRP) for the synthesis of poly(methyl methacrylate) (PMMA) using white light irradiation. All of the derivatives were determined to be suitable PCs for O-ATRP as indicated by a linear growth of polymer molecular weight as a function of monomer conversion and the ability to synthesize PMMA with moderate to low dispersity (dispersity less than or equal to 1.5) and initiator efficiencies typically greater than 70% at high conversions. However, only PCs that exhibit strong absorption of visible light and strong triplet excited state reduction potentials maintain control over the polymerization during the entire course of the reaction. The structure-property relationships established here will enable the application of these organic PCs for O-ATRP and other photoredox-catalyzed small molecule and polymer syntheses.
- McCarthy, Blaine G.,Pearson, Ryan M.,Lim, Chern-Hooi,Sartor, Steven M.,Damrauer, Niels H.,Miyake, Garret M.
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p. 5088 - 5101
(2018/04/24)
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- LIGHT-EMITTING MATERIAL FOR ORGANIC ELECTROLUMINESCENT DEVICE, ORGANIC ELECTROLUMINESCENT DEVICE USING SAME, AND MATERIAL FOR ORGANIC ELECTROLUMINESCENT DEVICE
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Disclosed are a novel fused cyclic compound having excellent light emitting efficiency and thermal stability, a method for producing the same, and an organic electroluminescent device including the same compound. The fused cyclic compound is represented b
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Paragraph 0350-0353
(2016/10/08)
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- Bromination of 10-Phenylphenothiazine and 10-Phenylphenoxazine
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The reaction of either 10-phenylphenothiazine (1) with bromine in acetic acid or the cation radical of 1 with bromide ion gives ring substitution only and in accord with customary stoichiometry for nucleophilic substitution of aromatic cation radicals.However, the reaction of 1 with pyridinium bromide perbromide (2) gives predominantly 10-phenyl ring substitution and a small amount of ring substitution products.Evidence is presented which indicates that ring substitution occurs via cation radical whereas 10-phenyl substitution proceeds via electrophilic attack on the neutral molecule 1.Substitution of 10-phenylphenoxazine (4) occurs predominantly but not exclusively on the phenoxazine ring; some bromination does occur on the 10-phenyl ring.In contrast, the reaction of 4 with bromine gives only ring mono- and disubstitution products.These results indicate that both 1 and 4 react similarly under the same conditions.
- Jovanovic, Misa V.,Biehl, Edward R.
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p. 1905 - 1908
(2007/10/02)
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