Absorption spectra azobenzenes

Fig. 11. Nonlinear scattering spectra for chloroform solution of nitro-azobenzene dendrimer (curve a) and neat chloroform solution (curve b). Inset is absorption spectrum of sample...

Fig.7. Quadratic Stark effect spectrum of a poly(methylmetacrylate) film doped with an azobenzene-linked amphiphile C180AZ0C00H (solid line). Dotted line, broken line, and dash and dotted line show an absorption spectrum of the film, its first derivative, and second derivative, respectively.

Figure 16 shows a change in the absorption spectrum of the LB film of APT(8-12) with UV (365 nm) and visible (436 nm) photoirradiation. The strong band around 360 nm is due to the trans isomer of azobenzene. The absorption due to the local excitation of TCNQ polarized along the long axis is located at about 315 nm but is indiscernible in this spectrum since the transition moment of this band is oriented almost perpendicular to the film surface and the electric field of the light is parallel to the film surface [149]. 

The utility of such an approach is demonstrated on the molecular level with the case of benzylideneaniline 6-XXXV (R-H), which occupied spectroscopists for nearly three decades (Haselbach and Heilbronner 1968, and references therein). This material is isoelectronic with azobenzene 6-XXXVI and stilbene 6-XXXVII, but its solution absorption spectrum differs significantly from them (Fig. 6.18). 

The quantum yield at 436 nm is significantly higher than it is at shorter wavelength irradiation (Table 1.3) which is like in azobenzene-type compounds. Indeed, in hydrocarbon solution, the absorption spectrum shows the azobenzene-type feature of a long wavelength n —> band (Figure 1.11). 

Figure 1.11), and a pseudo-stilbene type with a (7t,7t ) state as the lowest-excited state (see also Figure 1.13). The assignment of an azo molecule or an azobenzene-containing macromolecule or system to one of these classes can be made by a simple inspection of the absorption spectrum. The spectroscopic properties of these types of azo compounds will be covered in Sections 1,3 to 1.5 of this chapter.

Figure 4.5 Absorption spectrum of a Hyflon AD60X membrane doped with azobenzene, starting with the film as prepared, containing the trans isomer, and using a blank film without the dye as a reference. The isomerization is reversible over several cycles of alternating irradiation at 350nm and 440nm...

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