4- Methoxyazobenzene

Methyl-4 -methoxyazobenzene, 320 Ar-Methyl-2[6 -methoxynaphthyl-(2 )]pyri-deine, 95... 

Control of the aggregation state in an organogel offers other attractive means for modulation of materials properties and nondestructive read-out. A photoactive gela-tor (40) was obtained by Shinkai et al.[80] by connecting 4-methoxyazobenzene through an ester linkage to cholesterol. The trans-isomer 40 formed a stable gel with... 

The nonequivalence of some signals that are equivalent in solution NMR complicates the interpretation of the 13C CP/MAS NMR spectra of azo dyes, even for simple compounds where the chemical shifts measured in solution and their interpretation are available. The dipolar dephasing experiment permits the selective measurement of nonprotonated carbon (i.e. with no directly bound hydrogen). We have used Q,Ds deuterated isotopomers88 in the analysis of the 13C CP/MAS spectra of azo dyes. I3C CP/MAS NMR spectra of 4-[/V,/V-bis(2-hydroxyethyl)amino]azobenzene (28), 2-hydroxy-5-ter -butylazo-benzene (29) 4-(Ar,A-dimethylamino)azobenzene (30), 4-methoxyazobenzene (31) and 4-hydroxybenzene (32) were recorded. 

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. ... 

There is one report of a concentration dependence of the 313 nm photo-stationary state of azobenzene and 4-methoxyazobenzene in cyclohexane— not in benzene or CCI2F-CCIF2—in the literature.A bimolecular excimer intermediate was postulated. Further work is needed to elucidate whether the absorption coefficients or the quantum yields are concentration-dependent, for instance by ground or excited-state association (cf. Equation 1.3). 

TABLE 1.3 Quantum Yields for E Z Isomerization of 4-Diethylaminoazobenzene (4-DEAMAB) and 4-Dicthylamino-4 -methoxyazobenzene (4-DEAM-4 -MOAB) in De-are rated Cyclohexane (Adapted from reference 134.)... 

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. 

Kawatsuki N, Uchida E, Ono H. 2003. Formation of pure polarization gratings in 4 methoxyazobenzene containing polymer films using off resonant laser light. Appl Phys Lett 83(22) 4544 4546. 

Kawatsuki et al., described two different techniques for thermally enhanced photoinduced reorientations of liquid crystalline polymethacrylate films that contain 4-methoxyazobenzene side groups with various alkylene spacer lengths ... 

New a-amino carboxylate complexes 94 of palladium(ii) have been reported. " Cyclopalladated aminoazobenzenes were the subject of dynamic NMR studies " cyclopalladation of 7V-(benzoyl)-jV -(2,4-dimethoxybenzylidene)hydrazine and of photochromic 4-methoxyazobenzene were reported. 

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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