One-electron reduction of
[Pt(bpy)2]2+ (bpy = 2,2‘-bipyridyl)
in aqueous solution results in the formation
of black-green lustrous needles on solid electrodes. The
crystalline needles grow perpendicularly from the
substrate
surface and reach lengths of 1−2 cm. Elemental analysis, X-ray
photoelectron spectroscopy, and electrochemical
measurements indicate that the new compound is a genuine
PtI complex with a d9 electronic configuration
and with
the composition
[Pt(bpy)2]NO3·2H2O.
X-ray crystallographic analysis shows that the crystalline needles
consist of
linear chains of discrete [PtI(bpy)2]
units with a Pt−Pt distance of 3.563(1) Å and with each
bipyridyl ligand overlapping
face-to-face (eclipsed) with its nearest neighbor. At the
monomeric level, the structure of
[PtI(bpy)2] units exhibits
a distorted square-planar configuration with structural parameters very
similar to those of the parent PtII complex,
[Pt(bpy)2](NO3)2·H2O.
The new linear-chain compound was prepared by chemical and
electrochemical methods.
The resulting crystals are relatively stable in air but oxidize
slowly over a period of weeks. Scanning electron
microscopy reveals that the crystals are tubular with a hollow
near-hexagonal morphology. Cooperative effects
influence the optical and electrical properties of the crystals.
Because of extensive solid-state interactions between
stacked monomeric [PtI(bpy)2] units, the
crystals absorb strongly over the whole visible region and far into the
near
infrared. Their room temperature electrical conductivity is
relatively high, 10 Ω-1
cm-1.
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