Homopolymers with Octahedral Metals

Octahedral ruthenium(II) and osmium(II) polypyridyl complexes combine thermal and chemical stability with very interesting photophysical and electronic properties (see Chapter 2, Section 2.3.2). These considerations have prompted a range of studies that target polymers based on polypyridyl and related complexes [7]. For example, in the mid- and late 1990s, crosslinked films derived from the thermal, electro- or photopolymerization of polyfunctional monomeric complexes 7.1 and 

Impressive results in terms of the synthesis and characterization of soluble linear Ru-polypyridyl coordination polymers were reported in 1997 [10]. Reaction of tetrapyridylphenazine (tppz) with impure ruthenium precnirsors [Ru(R2bpy)Q3]x was found to give fairly low molecular weight polymers 7.3 with M 16,000 (DPn 15) (Eq. 7.2). However, when stoichiometric balance was possible due to 

These studies have been eictended to analogous polymers 7.5 (Eq. 7.2) with bulky adamantylmethyl groups attached to the bipyridyl substituents [11]. Viscosity measurements in the presence of added salt showed the intrinsic viscosity of 7.5 ([rj] 23 mL g ) to be approximately twice that of 7.3 and 7.4, which is indicative of a much more extended chain conformation in solution. 

Rod-like terpyridyl polymers 7.6 have also been accessed through step-growth polycondensation strategies (Eq. 7.3). Analogous routes those employed for the formation of 7.3-7.5 were successful in the preparation of high molecular weight materials with DPn 30 [12]. However, Pd-catalyzed polycondensation processes afforded only low molecular weight products. 

Main hain polymers containing tris(bipyridyl)ruthenium units have also been used in combination with electron-conducting Ti02 nanoparticles and hole-con- 

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