Quantum yield singlet oxygen generation

Although the above indirect method provided relatively accurate results, a new method of direct measurement of the IR phosphorescence of O2 ( A ) at 1270 nm was expected to improve the measurement [103]. The quantum yield of two-photon singlet oxygen generation, was calculated from... 

Table 6 Two-photon absorption cross sections, 32PA> and quantum yields of singlet oxygen generation, under single and two-photon excitation of 57-60 at 775 nm in ACN...

A few current examples are shown below and include unsymmetrically substituted derivatives 14227, the cationic derivative 15228, the neutral derivative 16226 and the classic anionic derivative 17229 230, (tetrabenzoporphyrinato)zinc(II) , an intermediate structure between that of porphyrins and phthalocyanines, and have also been investigated in this respect. However, its quantum yield for singlet oxygen generation (0.023) in liposomes is much lower than that of Photofrin (0.19)177. 

On the other hand. Type II process competes efficiently with the electron-transfer pathway in aerobic environments where the concentration of ground triplet state molecular oxygen is relatively high ( 0.27 mM), and singlet molecular oxygen (1O2) is the most abimdant ROS generated under these conditions, with a quantum yield 0.48 (Valle et al., 2011), eqn. 8. It is also possible an electron-transfer reaction from 3RF to 02 to form anion superoxide, but this reaction occurs with very low efficiency <0.1% (Lu et al., 2000). 

Evidence for adiabatic photolytic cycloreversions at room temperature has been obtained more frequently in recent years [121,122], The adiabatic generation of singlet oxygen by photochemical cycloreversion of the anthracene and 9,10-dimethylanthracene endoperoxides 105 and 106 proceeds with wavelength-dependent quantum yields of 0.22 and 0.35, respectively, and involves the second excited singlet state of the endoperoxides [123]. Photodissociation of the 1,4-endoperoxide from l,4-dimethyl-9,10-diphenylanthracene was found to yield both fragments, i.e., molecular oxygen and l,4-dimethyl-9,10-diphenylanthracene, in their electronically excited state [124]. 

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