Mechanically attached, solid-state films of [Os(bpy)(2) bpt Cl] have been f
ormed on platinum microelectrodes and their voltammetric properties investi
gated, bpy is 2,2'-bipyridyl and bpt is 3,5-bis(pyridin-4-yl)-1,2,4-triazol
e. Scanning electron microscopy reveals that voltammetric cycling in 1.0 M
HClO4 converts the amorphous array of microscopically small particles into
a plate-like semi-crystalline form. In contrast, crystallisation does not o
ccur when the films are cycled in 1.0 M NaClO4. In both electrolytes, the v
oltammetric response of these films is reminiscent of that observed for an
ideal reversible, solution phase redox couple. Slow and fast scan linear sw
eep voltammograms have been used to provide an absolute determination of th
e fixed site concentration and apparent diffusion coefficient, D-app. The f
ixed site concentration is 1.65 +/-0.05 M for films cycled in either electr
olyte and the D-app values increase with increasing electrolyte concentrati
on, C-elec. These observations suggest that ion transport rather than the r
ate of electron self-exchange limit the overall rate of charge transport th
rough these solids. In 1.0 M NaClO4, D-app values for oxidation and reducti
on are identical at 8.3 +/-0.5x10(-12) cm(2) s(-1). In 1.0 M HClO4, D-app i
s significantly lower and depends on whether the deposit is being oxidised
(9.7 +/-0.4x10(-13) cm(2) s(-1)) or reduced (6.3 +/-0.4x10(-13) cm(2) s(-1)
). These data have been used to obtain an insight into the relative importa
nce of intra- vs. inter-particle charge transport. When C-elec>0.5 M, the s
tandard heterogeneous electron transfer rate constant, k degrees, becomes i
ndependent of the electrolyte concentration with a value of 1.7 +/-0.2x10(-
5) cm s(-1) being observed in both 1.0 M NaClO4 and HClO4. Significantly, t
he distance normalised heterogeneous electron transfer rate constant for th
ese solid state films is almost three orders of magnitude smaller than that
found within a spontaneously adsorbed monolayer of the same complex. The i
mportance of these results for the rational design of solid-state redox act
ive materials for battery, display and sensor applications is considered.