Solid state spectroelectrochemistry of microparticles of ruthenium diimine complexes immobilised on optically transparent electrodes |
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Authors: | Gregory J Barbante Conor F Hogan Andrew B Hughes |
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Institution: | (1) Department of Chemistry, La Trobe University, Melbourne, Victoria, 3086, Australia |
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Abstract: | The solid state electrochemistry and solid state spectroelectrochemistry of two ruthenium complexes, ruthenium tris-(4,7-diphenyl-1,10-phenanthroline)
bis-hexafluorophosphate, Ru(dpp)3](PF6)2, and ruthenium bis-(2,2′-bipyridine)(4,6-diphenyl-2,2′-bipyridine)bis-hexafluorophosphate, Ru(bpy)2(dpb)](PF6)2, is described. Microparticles of the material are immobilised on ITO electrodes, and stable voltammetric signals are obtained
in contact with aqueous electrolyte solution. Spectral changes monitored during a slow cyclic voltammetric scan confirm the
exhaustive oxidation of the Ru2+ species to the Ru3+ form. The derivative of the absorbance signal monitored at a single wavelength during potential cycling is morphologically
identical to a cyclic voltammogram with no background current. This technique is shown to be useful when peaks of small magnitude
are obscured by capacitive background or when peaks close to the solvent limit are obscured by solvent electrolysis current.
The technique effectively widens the electrochemical window available for voltammetric measurements. After suitable correction
of the signal, the value of the voltammetric peak height (I
p) as well as peak potential (E
p) may be obtained from the derivative absorbance signal. Chronospectrometry is demonstrated to provide the equivalent to a
chronocoulometric response, but is closer to the ideal simulated response. A facile method for simulating time or potential-dependant
spectroelectrochemical responses using commercial electrochemical simulation software is described. Absorbance transients
monitored during the electrolysis of solid particles of Ru(dpp)3](PF6)2 show best agreement with simulated data at very short and very long timescales. This observation, in conjunction with the
observations from the potential scan experiments, suggests that the absorbance, charge, or current vs. time behaviour of the
system can be adequately described by a semi-infinite diffusional model at short experimental timescales and by a finite diffusional
model at sufficiently long timescales.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Dedicated to the 80th birthday of Keith B. Oldham. |
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Keywords: | Voltammetry of microparticles Ruthenium diimine complexes UV-Vis spectroelectrochemistry Optically transparent electrodes Derivative cyclic voltabsorptometry Chronospectrometry |
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