Polymers Containing Azobenzene Chromophores in Their Sidechains

POLYMERS CONTAINING AZOBENZENE CHROMOPHORES IN THEIR SIDECHAINS 

It was observed that the colors of complexes 55a-c were orange, orange-red, and red, respectively, while complex 53 is light beige-yellow. UV-Vis analysis of complexes 55a-c showed that they absorbed at 421, 452, and 491 ran, respectively, while the wavelength maximmn for complex 53 was around 273 nm.  

The NMR spectrum of complex 55b shows three methyl resonances at 12.31,26.83, and 27.72ppm five methylene resonances at 30.67,37.02,46.16,48.96, and 62.29 ppm and a quaternary aliphatic carbon at 45.50 ppm. The cyclopentadienyl carbons appear at 80.31 ppm and the complexed aromatic carbons resonate at 76.86, 87.66, 104.70, and 133.73ppm. There are six aromatic CH carbons resonating between 112.36 and 130.50ppm and six quaternary aromatic carbons observed between 137.91 and 156.30ppm. Finally, the carbonyl resonances can be seen at 173.50 and 197.34ppm. 

The thermal properties of the carboxylic acid-frmctionalized polymers were compared with the azo-frmctionalized polymers in order to examine the effects of the azobenzene sidechains. In addition, a comparison of the thermal properties of the metallated and demetallated azo-frmctionalized polymers could provide information on the influence of the cyclopentadienyliron moieties on these materials. Thermal analysis of these polymers was performed using thermogravimetric analysis and differential scanning calorimetry. 

Cotter, Engineering Plastics A Handbook of Polyarylethers, Gordon and Breach, New York, 1995. 

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V POLYMERS CONTAINING AZOBENZENE CHROMOPHORES IN THEIR SIDECHAINS... 

Polymers Containing Azobenzene Chromophores in their Sidechains 223... 

Abd-El-Aziz and coworkers have also reported the preparation of organoiron polymers containing azobenzene chromophores in their sidechains. Scheme 14 shows the synthesis of orange and red-colored cationic polymers (58) that absorbed between 417 and 489 nm. Polymers 58 were subsequently demetallated to produce their corresponding organic analogs (59). Photolysis of polymers 59 in the presence of hydrogen peroxide resulted in the decoloration of these polymers. 

The azobenzene-fimctionalized complexes 55a-c (Scheme 18) were also reacted with nucleophiles 2d, 7, and 10, resulting in the isolation of polymers 57a-c, 58a-c, and 59a-c in excellent yields. These cyclopentadienyliron-coordinated polyaromatic ethers or ether/thioethers containing azobenzene chromophores in their sidechains displayed fair to excellent solubility in polar organic solvents such as DMF, DMSO, and acetonitrile. The polymers prepared using bisphenol A (2d) possessed the highest solubibty, while polymers prepared with 4,4 -thio-Z>/5-benzenethiol (7) and 1,8-octanedithiol (lOd) often formed gels. 

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