Azobenzene complexes

The facile insertion of CO takes place. The 2-aryl-3-indazolone 484 is obtained in high yields from the azobenzene complex 463 in alcohol or waterf442]. For unsymmetrically substituted 4-methyl, 4-chloro-, and 4-meth-... 

Chlorination of the azobenzene complex 463 with chlorine produces mono-chloroazobenzene with regeneration of PdCN. Then complex formation takes place again with the chlorinated azobenzene. By this sequence, finally tetra-chloroazobenzene (503) is obtained using a catalytic amount of PdCT. The reaction, carried out by passing chlorine gas into an aqueous dioxane solution of azobenzene and PdCf for 16 h, gives a mixture of polychlorinated azoben-zenes[455]. 

Structural motifs related to Schiff-base ligands have been explored. Three tridentate ligands have been coordinated to the VO (quin) fragment (quin = 8-quinolinato). The octahedral azobenzene complex VO (quin) (2-hydroxy-2 -carboxy-5-methylazobenzene) shown in Fig.22 has a reversible reduction (by CV and controlled potential electrolysis) at ca —0.31 V versus Cp2Fe/CH2Cl2. This potential is 0.58 V more positive than the potential found in the analogous Schiff-base VO (quin) (V-(l-hydroxyethyl)salicylaldimine) complex. The latter complex reduction is also... 

The visible absorption bands of a series of azobenzene complexes are reported in Table 13. It has been noted that the visible band shifts to higher energy on increasing the a basicity of the coligand L.208... 

Barigelletti, F., Ghedini, M., Pucci, D., and LaDeda, M. (1999). A mercurated azobenzene complex for photoswitching between trans- and cis forms. Chem. Lett. 297-298. 

Tachibana, H., Yoshino, N., and Matsumoto, M. Photoinduced Orientational Change in Langmuir-Blodgett Films of Azobenzene Complexed with Polyviologen. Chem. Lett., 240 (2000). 

Recently Rouike has reported a series of cyclopalladated imine complexes with either acetylacetonate or cyclopentadienyl as the other ligand, as in Figure 8 [29]. Unlike Ghedini s azobenzene complexes these are isomerically pure but still display mesophases at similar temperatures. The square planar 16e acetylacetonate complexes display both nematic and Sa phases with extended mesophase ranges compared to the free ligands. Not surprisingly, the formally trigonal bipyramidal 18e cyclopentadienyl complexes show a nematic phase at much lower temperatures and tend to decompose above c. 180°C. 

A related series of palladium(II) azobenzene complexes with halogen bridging ligands has been prepared by Ghedini, in which the chirality was present in one of... 

Figure 2.13 Deeply coloured dinuclear cyclopalladated azobenzene complexes. The colour depends on the bridging group...

Several Pd(II) cyclometallated azobenzene complexes, having general structures (azb )PdBr(L) and (azb")PdBr(L) (12) where L = 4-stylbazole, have... 

The reaction of chlorine with the azobenzene complex affords ortho-chlorinated azobenzene, and palladium chloride is regenerated 112). 

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