The First Example of Cationic Iron-Coordinated Polyaromatic Ethers and Thioethers with Azo Dye-Functionalized Side Chains Alaa S. Abd-El-Aziz,* Tarek H. Afifi, Wes R. Budakowski, Ken J. Friesen, and Erin K. Todd Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, Canada R3B 2E9 Received June 25, 2002 Revised Manuscript Received October 3, 2002 Recently, there have been a number of articles outlin- ing the unique electrooptic properties that result from the incorporation of azo chromophores into high molec- ular weight materials. 1 The properties of these materials are related to both the structure of the polymer and the bathochromicity of the dye. These types of polymers often exhibit nonlinear optical properties, which has led to their application in optical storage devices, electro- optic modulators, and second harmonic generators. A recent report has demonstrated the use of azo dye- functionalized polymers as polyelectrolytes and de- scribed the property changes that may arise from the trans-cis isomerization of azo chromophores. 2 The UV- vis properties of these azo compounds did not change upon inclusion into the polymers, and they showed promise as ultrathin multilayers and stimuli responsive materials. Organometallic polymers have received a great deal of attention in recent years due to their interesting electrical, catalytic, physical, and chemical properties. 3 Manners and co-workers have reported the synthesis and liquid crystalline properties of poly(ferrocenylsi- lanes) incorporating azo chromophores in their side chains. 4 We have recently reported the synthesis of a number of linear and star polymers incorporating cat- ionic cyclopentadienyliron (CpFe + ) moieties pendent to their backbones and side chains. 5 Herein, we report the first example of highly colored cyclopentadienyliron- coordinated polyaromatic ethers and thioethers contain- ing azobenzene dyes in their side chains. It has been established that chloroarenes coordinated to cyclopentadienyliron cations undergo facile nucleo- philic aromatic substitution reactions with oxygen- and sulfur-based nucleophiles, resulting in the formation of novel monomeric and polymeric materials. 5 Monomers containing azo dyes in their structures were synthesized via reaction of complex 1 5c with dyes 2a-c as described in Scheme 1. 6 Functionalization of the diiron complex 1 with the azo chromophores resulted in orange and red solids (3a-c) that absorbed at 421, 491, and 452 nm, respectively. These complexes were subsequently re- acted with dinucleophiles 4a-c to yield cyclopentadi- enyliron-coordinated polyaromatic ethers or ether/ thioethers containing azo chromophores in their side chains (5a-i) (Scheme 2). 7 These polymerization reac- tions occurred under very mild reaction conditions due to the excellent electron-withdrawing capability of the cyclopentadienyliron cations. Polymers 5a-i displayed fair to excellent solubility in polar organic solvents such as DMF, DMSO, and acetonitrile. The molecular weights of the polymers were determined using gel permeation chromatography following cleavage of the cyclopenta- dienyliron moieties. The weight-average molecular weights of polymers 5a-i were determined to be 13 400- 31 600 with polydispersities ranging from 1.2 to 2.6. Reaction of monomer 1 with dinucleophiles 4a-c using the same reaction conditions resulted in the isolation of organoiron-coordinated polymers containing pendent carboxylic acid groups. These polymers could be solu- bilized in a sodium hydroxide solution and displayed good solubility in DMF and DMSO. The wavelength maxima of organoiron polymers 5a-i were very similar to those of their corresponding monomers. The UV-vis spectra of these polymers obtained in DMF, ethanol, and acidic ethanol show peaks that are characteristic of the n f π* and π f π* transitions of azo dyes. 1 By increasing the electron- withdrawing nature of the R group (H, COCH 3 , NO 2 ), these materials exhibited bathochromic shifts, which corresponds to shifts to longer wavelengths. 8 For ex- ample, the maxima of 5a-c ranged from 418 to 420 nm, while the maxima of 5d-f and 5g-i ranged from 490 to 491 nm and 451 to 454 nm, respectively, in DMF. Increases in λ max were also observed upon addition of HCl to ethanolic solutions of these polymers. This halochromism is clearly seen by comparing the maxima of 5a in ethanol (418 nm) and acidic ethanol solutions (520 nm) due to the formation of azonium ions. 8 In contrast to the bright orange and red polymers func- tionalized with azo dyes (5a-i), the carboxylic acid- functionalized polymers were pale yellow or beige, and their absorptions occurred between 272 and 274 nm. It was possible to remove the cyclopentadienyliron moi- eties from the polymer backbones by irradiating the polymers with 300 nm light solutions of dichloromethane/ acetonitrile. NMR analysis of these organic polymers (6a-i) indicated that the organoiron units were no longer present; however, the integrities of the azo- functionalized polymers were retained. Figure 1 shows the visible spectra of polymers 6a, 6d, and 6g prepared via reaction of monomers 3a-c with bisphenol A (4a). * Corresponding author: Tel (204) 786-9944; Fax (204) 783- 8910; e-mail a.abdelaziz@uwinnipeg.ca. Figure 1. Visible spectra of polymers 6a, 6d, and 6g with maxima at 417, 489, and 452 nm, respectively. 8929 Macromolecules 2002, 35, 8929-8932 10.1021/ma0255837 CCC: $22.00 © 2002 American Chemical Society Published on Web 10/24/2002