On the conducting [Ru(bpy)(CO)2]n (bpy = 2,2’-bipyridine) polymer: Doping process, near-IR absorption, T-dependence and film growth

Electrochemical, metal-centred partial oxidation of the electrodeposited d8 Ru–Ru bonded chain [Ru0(bpy)(CO)2]n results in high electrical conductivity on the order of 10−1 S cm−1. The partial oxidation of Ru0 is reversible in presence of charge-compensating PF6- and ClO4- anions, and quartz crystal microbalance data show that the doping/undoping process is accompanied with transfer of unsolvated electrolyte anions. For BF4- and Cl− the process is more complex and in the chloride-case the doping results in break-up of the polymer film. The conductivity of the film is linearly dependent on the electrochemically controlled doping level. Spectroscopic evidence for charge delocalisation is obtained in the near-IR region, with the absorbance proportional to the doping level. The conduction process is thermally activated and ohmic behaviour is found for films both in electrolyte and gas phase. The microscopic structure of dry polymeric films is studied by SEM and anisotropic growth of cone-shaped columns is found. Linear increase in film thickness with deposition charge is obtained above 20 μm with a volume yield corresponding to a density 90% of the X-ray diffraction derived value reported in literature.

► High electronic conduction in Ru–Ru bonded chains upon partial oxidation.
► Electrochemically controlled doping level.
► Near-IR evidence for charge delocalisation.
► The conduction process is thermally activated.
► Polymer film growth and microscopic structure.