4-Diethylamino-4 methoxyazobenzene

Photochemically induced Z,E-isomerization has been observed in 4-diethyl-aminoazobenzene and 4-diethylamino-4 -methoxyazobenzene and in the mesoionic azo-compounds (6). The photoisomerization of aromatic azo-compounds on hydrated Si02 and AI2O3 has made available in the adsorbed state Z-isomers which were previously inaccessible. Z-2,3,4,5,6-Pentafluoro-phenylazobenzene, obtained by irradiation of the corresponding E-isomer, is unusually stable in the dark. ... 

Albini, A., Fasani, E., and Pietra, S. (1983). The photochemistry of azo dyes. Photo-isomerisation versus photoreduction from 4-diethylaminoazobenzene and 4-diethylamino-4 -methoxyazobenzene. J. Chem. Soc. Perkin Trans. II, 1021-1024. 

TABLE 1.3 Quantum Yi lds for -> Z Isomerization of 4-Dlethylaminoazobenzene (4>DEANAB) and 4 Diethylamino-4 -methoxyazobenzene (4-DEAH-4 -MOAB) in De-arerated Cyclohexane (Adapted from reference 134.)... 

Because thermal Z—>E isomerization can occur, determining quantum yields of aminoazobenzenes is more difficult. They can be determined if the photostationary state shows a different absorbance compared to the starting pure E-isomer and if can be measured. 4-Diethylaminoazobenzene and 4-(diethylamino)-4 -methoxyazobenzene gave 4>g > 0.7 on excitation at 436 nm but lower values of <0.4 were obtained using 366 nm and shorter wavelengths when these were determined at room temperature. ... 

The photochemistry of 4-diethylamino- and 4-diethylamino-4 -methoxyazobenzene was studied as reasonable models for commercially useful mono-azo dyes. It was concluded that the lowest singlet and triplet states of these azobenzene derivatives are only capable of geometrical isomerization, whereas hydrogen abstraction takes place from the high-lying triplet state of both the E- and Z-forms of these dyes. ... 

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