Azobenzene chains

Moss. R. A., and Jiang, W. (19.97). Modulation of photoisomerization in double-azobenzene-chain liposomes. Ixtngmuir 13, 4498-4501. 

Recently, this methodology has been applied by Liu and co-workers to obtain bimetallic ruthenium Tp complexes with cr,cr -bridging azobenzene chains. ... 

Figure C2.4.6. Azobenzene stmcture modified with hydrocarbon chains [53, 54],...

Success of depositing compounds where an 18-carbon chain was attached to one end of an azobenzene group and various different hydrophilic groups attached to the other end has been reported in X and Z mode [52] and piezo-and pyroelectric effects were demonstrated. 

Nakahara H and Fukuda K 1983 Orientation of chromophores in monolayers and multilayers of azobenzene derivatives with long alkyl chains J. Colloid Interface Sol. 93 530-9... 

Perez et al. [128] investigated the crystal structure of 4-(4 -ethoxybezoy-loxy)-2-butoxy-4 -(4-butoxysalicylaldimine)azobenzene. This compound contains four rings in the main core and a lateral alkoxy branch on one of the inner rings. The lateral butoxy chain is nearly perpendicular to the long axis of the main core. This molecular conformation induces the molecules to make a very complex network in the solid. The crystal cohesion is due to van der Waals interactions. The change of the lateral chain conformation in the solid and nematic phases is discussed. 

Hydroxyethyl methacrylate hydrogel containing azobenzene in the side chain... 

Three azobenzeneophane-type crown ethers in which the 4,4 positions of azobenzene are joined by a polyoxyethylene chain have been synthesized (Shinkai, Minami, Kusano Manabe, 1983). On irradiation with UV light, the ( ) (or trans) form (198) is isomerized to the (Z) (or cis) isomer (199). The ( ) isomer may be regenerated by heating, or by irradiation with visible light the interconversion is completely reversible. 

In prior work, related molecules had been obtained in which a polyoxyethylene chain linked the 2,2 -positions of the azobenzene moiety (Shiga,Takagi Ueno, 1980). Howeverforsuchsystems,theds trans interconversion is accompanied by gradual photodegradation probably resulting from the presence of steric strain in the cis isomers. 

RA and transmission techniques [3], and applied it to the studies of LB films of cadmium stearate [3], azobenzene-containing long-chain fatty acids and their barium salts [4], dipalmitoylphosphatidylcholine (DPPC) [5], and polyion complexes [6]. Furthermore, we explored the relationship between the molecular orientation evaluated by this method and pyroelectricity in alternating (noncentrosymmetric) Y-type LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid and of their barium salts [7]. 

C Wang, H Fei, Y Qiu, Y Yang, Z Wei, Y Tian, Y Chen, and Y Zhao, Photoinduced birefringence and reversible optical storage in liquid-crystalline azobenzene side-chain polymers, Appl. Phys. Lett., 74 19-21, 1999. 

These unexacting requirements make the simplest unsulphonated azo structures, often monoazo types, quite acceptable [80]. Typical of the least polar members of this class are Cl Solvent Yellow 2 (4-68), Cl Solvent Orange 1 (4.69) and Cl Solvent Red 17 (4.70). Simple azo structures carrying sulphonamide, sulphone or carboxylate ester groups are used where a somewhat more polar, less soluble dye is needed. Simple disazo compounds (4-amino-azobenzene— 2-naphthol, for example) are used as red solvent dyes. Probably the only structural feature worthy of note in this class is the occasional adoption of structures carrying long alkyl chains to enhance solubility, as in the case of the disazo dye Cl Solvent Yellow 107 (4.71). 

The mixed liposomal solutions were prepared by the ethanol-injection method(13) in order to obtain completely transparent solutions. It is interesting to note that miscibility of the photochromic amphiphiles with DPPC depend on the position of bulky azobenzene. If azobenzene is incorporated close to the end of long alkyl chain, a stable mixed bilayer state cannot be formed. On the other hand, when the azobenzene moiety is located near the head group or at the center of the hydrocarbon tail, the azobenzene amphiphiles are successfully incorporated into the bilayer membrane. No individual micelle formation nor phase separation in the bilayer was observed at 25 °C by absorption spectroscopy. However, the microstructure of the mixed liposomes depends on the type of azobenzene amphiphiles. 

Weener et al. prepared photo-responsive monolayers from azobenzene modified polypropylene imine) dendrimers which also hold promise in the area of optical data storage [74], A fifth generation polypropylene imine) dendrimer was functionalized with equal amounts of palmitoyl and azobenzene containing alkyl chains, resulting in the formation of an amphiphilic copolymer with a random shell structure (Figure 16.5). 

Food Chain Bioaccumulation. 1,2-Diphenylhydrazine reacts rapidly in water to form azobenzene and other oxidation products (half-life in wastewater is 60 minutes). Because of this and based upon the log octanol/water partition coefficient, no bioaccumulation is expected in any aquatic organism. 

For example, PPI dendrimers functionalized with azobenzene chromophores appended with aliphatic side chains assemble into large spherical vesicles in water below pH 8 (Fig. 11.14 Tsuda et al. 2000). 

---