8840 J. Phys. Chem. B, Vol. 105, No. 37, 2001
Cameron et al.
Ru(bpy)2Cl2‚2H2O (0.0899 g, 0.173 mmol) and poly(Py-
Im2Ph) (0.0390 g, 0.127 mmol‚site) were refluxed for 4 days
in glycerol (50 mL) under N2. Dilution with two volumes of
water, filtration, and addition of a large excess of saturated aque-
ous NaClO4 solution to the filtrate produced a red solid, which
was collected by filtration and then stirred in water (20 mL)
overnight. The solid was again collected by filtration, washed
with water then diethyl ether, and then air-dried to give 0.124
g (100% yield) of a fine red-brown solid. Elemental analysis:
Calculated for C33H23N9O8Cl2Ru‚H2O‚C3H8O3: C 45.24%, H
3.48%, N 13.19%. Found: C 45.16%, H 3.12%, N 13.23%.
Bisbipyridylruthenium(II) complex of poly[(6,6′-bibenzimi-
dazole-2,2′-diyl)-2,5-pyrazine] (poly{[Ru{Pz-(ImPh)2}(bpy)2]-
(ClO4)2}). Ru(bpy)2Cl2‚2H2O (0.0980 g, 0.188 mmol) and
poly(Pz-(PhIm)2) (0.0308 g, 0.070 mmol‚site) were refluxed in
glycerol (50 mL) for 3 days. The resulting red liquid was cooled
to r.t., filtered (leaving no residue), diluted with H2O (200 mL),
and filtered again. Addition of a large excess of saturated
aqueous NaClO4 solution precipitated a green solid which was
collected by filtration, rinsed copiously with water and air-dried
to give 0.130 g (108%) of a dark green solid. Elemental
analysis: Calculated for C18H10N6(C20H16N4Cl2O8Ru)1.95‚(H2O)-
(C3H8O3)2: C 44.34%, H 3.50%, N 11.33%. Found C 44.51%,
H 3.18%, N 11.24%.
Figure 3. Cyclic voltammetry (100 mV s-1) of poly[Os{Py-(PhIm)2}-
(bpy)2] on a Pt disk electrode in CH3CN containing 0.1 M Et4NClO4.
Scan numbers are indicated.
A similar polymer complex with lower Ru content was
prepared analogously, with only one equivalent of Ru(bpy)2Cl2‚
2H2O having been used.
Bisbipyridylosmium(II) complex of poly[(6,6′-bibenzimida-
zole-2,2′-diyl)-2,5-pyridine] (poly{[Os{Py-(PhIm)2}(bpy)2]-
(ClO4)2}). Os(bpy)2Cl2 (0.118 g, 0.207 mmol) and poly(Py-
(PhIm)2) (0.061 g, 0.157 mmol‚site) were refluxed together in
glycerol (50 mL) for 6 days. The resulting dark solution was
filtered and diluted with H2O (300 mL). A large excess of solid
NaClO4 was added, and the resulting red precipitate was
collected by filtration. It was then stirred in a large volume of
water overnight and collected by filtration again, giving 0.148
g (90%) of a fine black powder. Elemental analysis: Calculated
for C19H11N5(C20H16N4Cl2O8Os)‚2H2O: C 44.75%, H 2.98%,
N 12.04%, Cl 6.77%. Found C 45.26%, H 3.21%, N 11.01%,
Cl 6.16%.
Bisbipyridylosmium(II) complex of Poly([6,6′-bibenzimida-
zole-2,2′-diyl]-2,5-pyrazine) (poly{[Os{Pz-(ImPh)2}(bpy)2]-
(ClO4)2}). Os(bpy)2Cl2 (0.045 g, 0.079 mmol) and poly(Pz-
(PhIm)2) (0.011 g, 0.025 mmol‚site) were refluxed in glycerol
(25 mL) under N2 for 4 days. Dilution of the resulting dark
solution with two volumes of water, filtering, and addition of
excess solid NaClO4 to the filtrate produced a dark green-brown
solid, which was collected and then stirred in H2O (20 mL)
overnight. The resulting black solid was collected by filtration,
rinsed with water then ether, and air-dried to give 39.8 mg (80%)
of a fine black solid. Elemental analysis: Calculated for
C18H10N6(C20H16N4Cl2O8Os)1.95‚3.4C3H8O3: C 40.53%, H 3.46%,
N 9.71%. Found C 40.95%, H 3.12%, N 9.31%.
Figure 4. Cyclic voltammetry (100 mV s-1) of poly[Os{Py-(PhIm)2}-
(bpy)2] on a Pt disk electrode in CH3CN containing 0.1 M Et4NClO4
and HClO4 or Bu4NOH.
Results and Discussion
Cyclic Voltammetry. The cyclic voltammetry of poly[Ru-
{Py-(PhIm)2}(bpy)2] has been described in detail elsewhere.9
A redox wave due to the Ru(III/II) couple appears in the range
of ca. 0.8 V to 1.2 V vs SSCE, depending on the degree of
protonation of the polymer backbone, and a pair of bipyridine-
based reductions appear at -1.47 and -1.77 V vs SSCE (in
neutral CH3CN). The Ru(III/II) half-wave potential changes by
-63 mV pH-1 in the pH 2-4 range, consistent with a one-
proton, one-electron process, and a pKa of ca. 5. The voltam-
metric behavior of poly[Ru{Py-Im2Ph}(bpy)2] is similar to that
of poly[Ru{Py-(PhIm)2}(bpy)2] and so will not be discussed.
Figures 3 and 4 show voltammograms of films of poly[Os-
{Py-(PhIm)2}(bpy)2] on Pt electrodes in neutral, acid, and basic
CH3CN. The first scan in the neutral electrolyte (Figure 3) shows
Os(III/II) waves at ca. +0.4 V and +0.8 V and several ligand-
based reduction waves in the -1 to -2 V region. Cycling
through these reduction waves causes (a) the appearance of a
new Os(III/II) wave at ca. +0.15 V, (b) a large increase in the
size of the +0.4 V wave, and (c) disappearance of the +0.8 V
wave. As previously discussed for the Ru analogue,9 these
changes arise from an increase in pH resulting from the
reduction of water in the film or electrolyte. As shown by the
voltammograms recorded under acidic and basic conditions
(Figure 4), the +0.8 V formal potential corresponds to the
protonated polymer, while that at +0.4 V corresponds to the
deprotonated form. However, this explains neither the presence
of the small wave at +0.15 V in the neutral electrolyte (second
Purity of the Metallopolymers. The absence of monomeric
Ru complexes in the poly{[Ru{Py-(PhIm)2}(bpy)2](ClO4)2}
sample was established by gel permeation chromatography.9 For
the other metallopolymers, the absence of significant extraction
of colored species into CH2Cl2 and the absence of electrochemi-
cal waves characteristic of M(bpy)2X2 and M(bpy)3 species were
taken as sufficient evidence that monomeric complexes had been
removed during washing.
Film Preparation. Films of the metallopolymers were cast
onto Pt or glassy carbon disk electrodes from solutions in N,N-
dimethyl acetamide, DMF, or water saturated nitromethane.