Metal−Metal Interactions in a Novel Hybrid Metallopolymer

A conjugated polymer−redox polymer hybrid based on the complexation of poly[2-(2-pyridyl)bibenzimidazole] with bis(2,2‘-bipyridyl)Ru 2+ has been prepared to take advantage of electronic communication between metal centers through the conjugated backbone. The existence of such communication is confirmed by the observation of an intervalence charge-transfer band in the near-IR spectrum of the Ru(III/II) mixed valence state. Electron transport studies by rotating disk voltammetry, dual (sandwich) electrode voltammetry, and impedance spectroscopy have yielded electron diffusion coefficients ( D e ) of over 10 - 8 cm 2 s - 1 for the Ru(III/II) mixed valence state. D e in nonconjugated Ru(2,2‘-bipyridyl) 3 3+/2+ -type polymers is typically less than this by at least a factor of 10, indicating that electron transport in the new polymer is enhanced by communication of metal centers through the backbone. The redox potential of the Ru sites, and D e, can be manipulated by changing the electron density on the polymer backbone via pH control of the degree of protonation of the imidazole moieties.