Neutral and Cationic Cyclopentadienyliron Macromolecules Containing Azo Dyes

Abstract

A number of classes of organoiron polymers containing azo dyes pendent to, or in their backbone have been prepared. The first class includes cationic organometallic polyethers, polythioethers and polynorbomenes incorporating aryl and hetaryl azo dyes. These organometallic polymers were synthesized via nucleophilic aromatic substitution reactions or ring opening metathesis polymerization. The resultant polymers were all brightly colored and displayed excellent solubility in polar organic solvents. Thermal analysis indicated that the polymers were thermally stable with decomplexation of the metal moiety at approximately 235 °C. Photolytic demetallation of the polymers resulted in the decoordination of the cationic cyclopentadienyliron moieties and the formation of organic polymers. The organic polymers displayed lower glass transition temperatures than their cationic organoiron analogues. The second class of polymers is ferrocene based polymers with pendent cationic cyclopentadienyliron moieties. The reaction of arene complexes containing azo dye chromophores and terminal hydroxyl groups with 1,1'-ferrocenedicarbonyl chloride gave rise to triiron complexes with a substituted ferrocene center and two terminal arene complexes containing chloro groups. Nucleophilic aromatic substitution polymerization of these triiron complexes with O- and S-containing nucleophiles followed by photolytic demetallation led to the isolation of neutral ferrocene based polymers containing azo dyes in the backbone. Electrochemical studies of these complexes showed the reduction of the cationic iron moieties at -1.42 V, while the neutral iron species were oxidized at 0.89 V. UV-visible studies showed absorption at 419 nm and a bathochromic shift to 530 nm with the addition of HCl.