Conducting redox polymers: Investigations of polythiophene-Ru(bpy)3(n+) hybrid materials

Article abstract of DOI:10.1039/a903193f

A series of thiophene-appended Ru(II)(bpy)₃ derivatives, Ru(1)₃, Ru(2)₃, Ru(3)₃, Ru(bpy)₂(1), and Ru(bpy)₂(2), and their resulting polymers have been synthesized and characterized. The bpy ligands 5,5'-bis (5-(2,2'-bithienyl))-2,2'-bipyridine, 1, 4,4'-bis (5-(2,2'-bithienyl))-2,2'- bipyridine, 2, and 4-(5-(2,2'-bithienyl))-2,2'-bipyridine, 3, all contain electrochemically polymerizable bithienyl moieties. The monomers Ru (2)₃, Ru(3)₃, Ru (bpy)₂(1) and Ru(bpy)₂(2) display spectroscopic features that are similar to the ligand-based and MLCT bands found for Ru(bpy)₃. The cyclic voltammograms of all of these polymers display both metal-centered and thiophene-based electroactivity. High redox conductivity was found in poly(Ru(2)₃) and poly(Ru(3)₃) for both the thiophene-based oxidation and metal-based reduction processes. These results indicate that the polymers display charge localization for both the metal complexes as well as the tetrathienyl connecting units. The degree of interconnection (number of linkages) as well as the substitution pattern were found to control the conductivity of these polymers. The highest conductivity (3.3 x 10^-3 S cm^{- 1}) was found for poly(Ru(2)₃), which is able to have up to 6 linkages with other ruthenium complexes as well as possessing a 4,4'-substitution pattern that allows effective orbital overlap of the conjugated polymer backbone with the ruthenium centers.

Full text of DOI:10.1039/a903193f

J O U R N A L O F
Conducting redox polymers: investigations of
polythiophene–Ru(bpy) n+ hybrid materials
3
S. Sherry Zhu, Richard P. Kingsborough and Timothy M. Swager*
Department of Chemistry and Center for Materials Science and Engineering, Massachusetts
Institute of Technology, Cambridge, MA 02139, USA
C H E M I S T R Y
Received 21st April 1999, Accepted 14th June 1999
A series of thiophene-appended RuII(bpy) derivatives, Ru(1) , Ru(2) , Ru(3) , Ru(bpy) (1), and Ru(bpy) (2),
3
3
3
3
2
2
and their resulting polymers have been synthesized and characterized. The bpy ligands 5,5∞-bis(5-(2,2∞-bithienyl))-
2,2∞-bipyridine, 1, 4,4∞-bis(5-(2,2∞-bithienyl))-2,2∞-bipyridine, 2, and 4-(5-(2,2∞-bithienyl))-2,2∞-bipyridine, 3, all
contain electrochemically polymerizable bithienyl moieties. The monomers Ru(2) , Ru(3) , Ru(bpy) (1) and
3
3
2
Ru(bpy) (2) display spectroscopic features that are similar to the ligand-based and MLCT bands found for
Ru(bpy) . The cyclic voltammograms of all of these polymers display both metal-centered and thiophene-based
electroactivity. High redox conductivity was found in poly(Ru(2) ) and poly(Ru(3) ) for both the thiophene-based
oxidation and metal-based reduction processes. These results indicate that the polymers display charge localization
for both the metal complexes as well as the tetrathienyl connecting units. The degree of interconnection (number of
linkages) as well as the substitution pattern were found to control the conductivity of these polymers. The highest
2
3
3
3
conductivity (3.3×10−3 S cm−1) was found for poly(Ru(2) ), which is able to have up to 6 linkages with other
3
ruthenium complexes as well as possessing a 4,4∞-substitution pattern that allows effective orbital overlap of the
conjugated polymer backbone with the ruthenium centers.
poly(1), displayed conductivity derived from charge
delocalization in both n-doped and p-doped states.1
Introduction
Conjugated organic polymers incorporating redox-active
transition metal centers that are coupled to the p system offer
the potential to enhance the rate and range of electron transfer
between localized metal-centered redox sites relative to non-
conjugated polymeric systems.1–6 Integration of transition
metal complexes into a conducting polymer framework also
presents opportunities for unique photophysical, photochem-
ical, and electrochemical properties, catalysis, as well as the
Changing the position of the bithiophene moieties to the 4-
and 4∞-positions on the bipyridine ligand creates a system in
which the d and d orbitals of the ruthenium center can
xz
yz
communicate with neighboring metal centers by overlapping
with the p orbitals of the conjugated bridge. This is possible
due to the para relationship between the ruthenium centers
and the tetrathienyl bridge, allowing for the maximum elec-
tronic communication between the metal complexes. In this
paper we describe the polymerization of two new homoleptic
complexes, Ru(2) and Ru(3) , which have bithiophene
ability to create sensors for small molecules (O , CO, NO) or
2
anions (Cl−, PO 2−).7–15 Numerous investigations have
4
3
3
focused on nonconjugated polymers containing isolated
groups at the 4,4∞- and 4-position of the bipyridine ligand,
Ru(bpy) L ,8–15 ferrocene,16 and other redox-active metal
respectively, as well as the heteroleptic complexes Ru(bpy) (1)
n 3−n
2
centers.6,17 In these systems the charge hopping between these
and Ru(bpy) (2), which form polymers having Ru(bpy)
2
2
isolated metal centers can result in redox conductivity. There
are far fewer investigations of polymers wherein redox-active
metal centers are in electronic communication through conju-
gated bridges.1–6,8,18 These limited studies nevertheless suggest
that this is a promising approach to an important class of
materials.
complexes appended to an organic backbone. The metal-free
polymer poly(2) has also been prepared by oxidative polymer-
ization. Owing to the meta relationship of the bithiophene
moieties in this polymer and a lack of extended conjugation,
no drain current (conductivity) was detected under our exper-
imental conditions. The hybrid polymers, poly(Ru(2) ),
3
2
We have recently communicated the synthesis of
a
poly(Ru(3) ), poly(Ru(1)(bpy) ) and poly(Ru(2)(bpy) ),
3
2
polythiophene–Ru(bpy) 2+ hybrid material,1 poly(Ru(1) ),
display metal-centered redox-type conductivity that is compar-
able to the conductivity observed from the tetrathienyl
(organic) portion of the polymer. For comparison, additional
3
3
by the anodic polymerization of a tris[5,5∞-bis(5-(2,2∞-bithi-
enyl))-2,2∞-bipyridine]ruthenium() complex, Ru(1) (Chart
1). The bithiophene groups were substituted at the 5,5∞-
positions of bipyridine to produce a monomeric bipyridine
unit (1) in which there is extended conjugation across the
3
optical absorption and electrochemical studies of poly(Ru(1) )
3
are also reported.
bipyridine. In the case of poly(Ru(1) ) the ruthenium centers
3
are coordinated directly to the conjugated polymer backbone,
allowing for interactions between the polymer and the metal
centers. However, the 5,5∞-substitution of the bipyridine of
Results and discussion
Synthesis and characterization of Ru(bpy) derivatives
3
poly(Ru(1) ) produces limited interactions between neighbor-
3
We previously reported the synthesis of 5,5∞-bis(5-(2,2∞-bithi-
enyl))-2,2∞-bipyridine 1 from 5,5∞-dibromo-2,2∞-bipyridine19 via
standard Stille coupling methods (Scheme 1).1 4,4∞-Bis(5-(2,2∞-
bithienyl))-2,2∞-bipyridine 2 was prepared by similar methods
from 4,4∞-dibromo-2,2∞-bipyidine.20 Mononitration of 2,2∞-
bipyridine-N,N∞-dioxide21 with KNO in 98% H SO afforded
ing metal centers as a result of the non-conjugated meta
relationship between the thiophenes and the metal binding
sites, generating a system where the ruthenium complexes and
the polymer backbone have isolated electrochemical activities.
In spite of this localization, we found this hybrid system to
exhibit a redox conductivity of 9.4×10−4 S cm−1 involving
3
2
4
self-exchange between localized Ru(1) n+ sites,1 which is high
a route to 4-bromo-2,2∞-bipyridine (Scheme 2), which can be
converted into 4-(5-(2,2∞-bithienyl))-2,2∞-bipyridine 3 as above
3
relative to other redox conductors. The metal-free polymer,
J. Mater. Chem., 1999, 9, 2123–2131
2123

S
S
S
S
S
S
S
S
S
S
N
Ru
N
S
S
N
N
S
S
S
N
N
S
S
N
N
N
N
N
N
N
N
Ru
N
N
Ru
S
S
S
S
S
N
S
S
N
S
S
S
S
S
S
Ru(1)3
Ru(2)3
Ru(3)3
S
S
S
N
Ru
N
N
S
S
S
N
N
N
N
N
N
N
Ru
N
S
N
S
Ru(bpy)2(1)
Ru(bpy)2(2)
Chart 1
(Scheme 1). These compounds are characterized as low solu-
bility yellow solids which show satisfactory 1H NMR, mass
spectroscopy, and elemental analysis.
found by others in diphenyl substituted Ru(bpy) complexes.23
3
The spectra are dominated by both ligand-based and metal-
to-ligand charge transfer (MLCT) absorptions. The complex
The homoleptic ruthenium complexes Ru(1) ,1 Ru(2) , and
Ru(1) displays a broad absorption peak at 454 nm
3
3
3
Ru(3) were synthesized by standard procedures.22 The 1H
accompanied by a slight shoulder at 410 nm. The broad
absorption is most likely a combination of ligand-centered
and MLCT bands and is almost coincident with that of
Ru(bpy) . In the case of Ru(2) the absorption at 404 nm is
3
NMR spectra of Ru(1) 1 and Ru(2) display only one set of
3
3
ligand-based proton signals, indicative of the expected D
symmetry of the octahedral metal centers. Complex Ru(3)
also exhibits one set of ligand-based proton signals that are
broadened due to the multiple isomers that are present. The
heteroleptic complexes Ru(1)(bpy) and Ru(2)(bpy) were
prepared in similar fashion from cis-RuCl (bpy) and the
appropriate bipyridyl ligand and show 1H NMR spectra which
3
3
3
3
likely a ligand-based transition which is red shifted from the
‘free’ ligand absorption due to coordination. These shifts are
expected based on the donor–acceptor nature of the ligand
chromophore. The strong absorption centered at 507 nm
(Table 1 and Fig. 1), which is far removed from the optical
spectra of free 2, is MLCT in nature. These spectral features,
while similar to those of Ru(bpy) (PF ) ,24 have both ligand-
2
2
2
2
are consistent with a C symmetry imposed by an ML L∞
2
2
ligand set in a six coordinate complex.
3
6 2
The UV–vis absorption spectra of the three ligands and
their ruthenium complexes are shown in Fig. 1. The spectrum
of 1 displays the lowest energy ligand-based absorption of the
based and MLCT absorbances that are red shifted due to the
electron-rich bithienyl moieties. Complex Ru(3) also displays
3
a similar optical absorption spectrum, although the red shift
series at l =396 nm, due to the extended conjugation
afforded by the 5,5∞-bithienyl moieties. The bithienyl substitu-
is not as substantial as in Ru(2) . The latter is likely due to
the diminished number of electron donating groups on the
max
3
ents on the bipyridine result in a substantially higher l
as
bipyridine ligands.
The heteroleptic complexes display features similar to their
homoleptic counterparts. Complex Ru(1)(bpy) displays a
UV–vis spectrum that is intermediate between those of
max
compared to parent bipyridine (l =283 nm). Bipyridine 2
max
exhibits a slightly higher energy absorption maximum at
2
361 nm due to its shorter conjugation length than bipyridine
1. Removal of one bithienyl moiety in bipyridine 3 results in
Ru(bpy) and Ru(1) . Two intense waves at 289 and 455 nm
3
3
a further blue shift of the absorption at l =354 nm (Fig. 1).
can be attributed to absorption by the bpy ligand and a MLCT
absorption, respectively. The intense MLCT band of
Ru(bpy) (1) is nearly coincident with that of Ru(1) , signify-
max
The UV–vis spectra of the ruthenium complexes show much
larger absorption cross-sections than those of the parent
ligands (Fig. 1). Similar absorption coefficient enhancements
of ruthenium complexes over ‘free’ ligands have also been
2
3
ing that the meta relationship between the bithienyl moieties
and the ruthenium center exerts little influence on the MLCT
2124
J. Mater. Chem., 1999, 9, 2123–2131

1.
2.
RuCl3·H2O
DMF
reflux 12 h
Ru(1)3
S
NH4PF6
acetone
SnBu3
S
S
S
S
S
Br
Br
PdCl2(PPh3)2
DMF
N
N
1. cis-RuCl2(bpy)2
EtOH/DMF
N
N
80 ºC
1
reflux 12 h
Ru(1)(bpy)2
2.
NH4PF6
acetone
1. RuCl3·H2O
DMF
reflux 12 h
S
S
Ru(2)3
2. NH4PF6
acetone
S
S
S
Br
Br
SnBu3
S
PdCl2(PPh3)2
DMF
cis-RuCl2(bpy)2
EtOH
1.
2.
1.
N
N
N
N
80 ºC
reflux 12 h
2
Ru(2)(bpy)2
NH4PF6
S
S
RuCl3·H2O
DMF
reflux 12 h
S
Br
SnBu3
S
Ru(3)3
PdCl2(PPh3)2
DMF
N
N
N
N
2. NH4PF6
acetone
80 ºC
3
Scheme 1
nated’ ligands.25–29 In this case we are able to observe the
meta and para effects of bithienyl substitution as well as the
overall number of bithienyl moieties that can perturb the
electronic structure of the complex.
NO2
H2SO4 (98%)
KNO3
100 ˚C
24 h
N+
O- O-
N+
N+
O- O-
N+
The reduction potentials (referenced to the Fc–Fc+ couple)
in CH Cl solutions for the ruthenium complexes studied here
2
2
are presented in Table 1. Data taken in MeCN solution for
selected complexes are also presented for comparison to pub-
lished [Ru(bpy) ][PF ] electrochemistry, as well as our pre-
CH3COBr
CH3CO2H
reflux
3
6 2
2 h
vious studies1 of Ru(1) . One trend that is immediately obvious
3
is that substitution of bithienyl residues onto the bipyridine
ligand results in reduction at more positive potentials than the
parent [Ru(bpy) ][PF ] . For the homoleptic series, only two
reversible redox waves are observed, not the three that are
Br
Br
3
6 2
PBr3
CHCl3
reflux
75 min
seen in [Ru(bpy) ][PF ] .30 Continued sweeping to more nega-
N
N
N+
O- O-
N+
3
6 2
tive potentials resulted in decomposition. Complex Ru(1)
3
shows an approximately 250 mV more positive reduction
potential in CH Cl than [Ru(bpy) ][PF ] . Changing the
Scheme 2
2
2
3
6 2
position of the bithienyl units to the 4- and 4∞-positions in
Ru(2) resulted in a reduction potential 70–80 mV more
absorption band. Complex Ru(bpy) (2) shows an intense
3
2
negative than Ru(1) . Complex Ru(3) , with only one bithi-
ligand-based absorbance with a l
at 291 nm (Fig. 1). It
3
3
max
enyl group attached to the bipyridine ligand, affords only a
moderate positive shift (80–120 mV) in the reduction poten-
tials relative to [Ru(bpy) ][PF ] . Consistent with the fact
also possesses two resolved, strong absorptions at 392 and
409 nm, as well as two MLCT bands at 465 and 485 nm. The
lower absorptivity of the 392 and 409 nm bands relative to
3
6 2
that the reduction processes of these complexes are principally
ligand-centered, their relative reduction potentials appear to
be related to the delocalization in the ligand. Apparently the
more highly conjugated ligand, 1, is more stable in its
reduced state.
those of Ru(2) supports their assignment as ligand-centered
3
transitions. Multiple MLCT bands have been observed for
other mixed-chelate complexes in which there are separate
transitions for each ligand.
The heteroleptic monomers also show shifts in the reduction
potentials. In CH Cl solution Ru(bpy) (1) shows only one
Electrochemical studies
2
2
2
The electrochemical behavior of all the reported complexes
has been investigated and found to depend on the amount
and position of the bithienyl substitution on the bipyridine
ligand. The reductive processes in ruthenium polypyridyl com-
plexes correlate with the reduction potential of the ‘uncoordi-
reduction wave at −1.50 V, unlike the homoleptic Ru(1) ;
3
Ru(bpy) (2) also displays only one redox wave at −1.73 V.
2
However, in MeCN solution different electrochemistry is
observed. Complex Ru(bpy) (1), like [Ru(bpy) ][PF ] , dis-
2
3
6 2
plays three one-electron redox waves at −1.49, −1.84 and
J. Mater. Chem., 1999, 9, 2123–2131 2125

Table 1 Electrochemical and electronic absorption characteristics of
monomers and polymers investigateda
Complex
E
/V vs. Fc–Fc+
l
b/nm
1/2
max
[Ru(bpy) ][PF ]
−1.74c
290, 452
3
6 2
−1.93c
[Ru(1) ][PF ]
−1.48 (−1.48)c
−1.68 (−1.68)c
−1.56
310, 400, 454
404, 507
3
6 2
[Ru(2) ][PF ]
3
6 2
−1.75
[Ru(3) ][PF ]
−1.62
398, 486
3
6 2
−1.85
[Ru(bpy) (1)][PF ]
−1.50 (−1.49)c
(−1.84)c
(−2.03)c
−1.73d (−1.60)c
(−1.86)c
−1.40
289, 399, 455
2
6 2
[Ru(bpy) (2)][PF ]
392, 409, 465, 485
412, 470
2
6 2
poly(Ru(1) )
3
−1.59
poly(Ru(2) )
−1.60
408, 506
3
−1.76
poly(Ru(3) )
−1.67
—
3
−1.79
poly(Ru(bpy) (1))
poly(Ru(bpy) (2))
−1.49
500
518
480
—
2
−1.92
2
poly(1)
poly(2)
−2.02
−2.07
aUnless noted otherwise, electrochemical measurements were per-
formed in 0.1 M Bu NPF –CH Cl solution at a platinum button
4
6
2 2
electrode at a scan rate of 50 mV s−1. bIn CH Cl solution. cIn 0.1 M
2
2
Bu NPF –MeCN solution at a platinum button electrode at a scan
rate of 100 mV s−1. dOnly one redox process observed.
4
6
that flowed between the two sets of electrodes, source and
drain, can then be observed as a function of the applied
potential. This drain current can be related directly to absolute
conductivity (s) by eqn. (1), where W is the distance between
the electrodes (5 mm), n the number of spaces between elec-
trodes, T the thickness of the film in the region between the
electrodes, and L the length of the finger.
i
W
D
D
s=
·
(1)
V
nT L
The thickness was determined for a film of poly(Ru(1) )
3
and from this value and the surface coverage C calculated
from integrating the ruthenium waves a ruthenium site concen-
tration of 3.8×10−4 mol cm−3 was determined. This value is
similar to that observed for other polymeric systems.† In the
polymers investigated here, where T%W (the calculated T was
between 8.0×10−6 and 3.0×10−5 cm), the calculated conduc-
tivity presented here represents a lower limit due to the thin
nature of the polymer film. Specifically, not all of the polymer
measured will be in the gap between the electrodes and the
thickness at the center of the gap is expected to be less than T.
In our previous communication1 we described the electro-
Fig. 1 The UV–vis spectra of ligands 1, 2 and 3 and the ruthenium
complexes Ru(1) , Ru(2) , Ru(3) , Ru(bpy) (1) and Ru(bpy) (2)
3
3
3
2
2
in CH Cl .
2
2
−2.03 V. Complex Ru(bpy) (2) displays two one-electron
2
redox waves at −1.60 and −1.86 V, which are very similar to
those observed for Ru(3) . The reason for the solvent depen-
3
chemical properties of poly(1) and poly(Ru(1) ) in MeCN
dency is unclear. The similarity of the redox potentials of
3
solutions. Poly(1) displayed conductivity in both the oxidative
Ru(3) and Ru(bpy) (2) suggests that only a single bithienyl-
3
2
and reductive regions. Poly(Ru(1) ) showed electrochemical
substituted ligand need be present to affect the first reduction.
This is also observed in the UV–vis spectra, as these two
complexes display bands at very similar wavelengths.
3
processes typical of materials composed of thienyl moieties
and ruthenium complexes. There was little difference in the
thienyl electrochemistry upon coordination of the ruthenium
Polymeric films of the ruthenium complexes were deposited
onto interdigitated microelectrodes31 by the anodic polymeriz-
ation of CH Cl monomer solutions. Once synthesized, the
centers; however, new Ru(bpy) -centered reduction processes
3
could be observed in the reduction region. Owing to the
2
2
limited stability of this polymer in the more nucleophilic
films were rinsed and transferred to a cell containing fresh
0.1 M Bu NPF –CH Cl for electrochemical analysis and
MeCN solvent, we reexamined the poly(Ru(1) ) electrochem-
3
4
6
2 2
istry in CH Cl . Examination of the polymer CV (Fig. 2a)
redox conductivity measurements. The polymer films were
electrochemically deposited on 5 mm interdigitated microelec-
trodes such that the film served as the connection between the
two sets of independently addressable electrodes. After a small
2
2
shows that the charge passed by the ruthenium bipyridyl-
†The same value was used for all of the compounds; however, these
complexes all have slightly different volumes due to their shapes and
density of polymerizable appendages. We previously determined the
potential difference (V ) was applied between the two elec-
D
trodes, the potentials of both electrodes were scanned versus
redox conductivity of poly(Ru(1) ) in MeCN as 9.4×10−4 S cm−1
3
the reference electrode at a slow rate. The drain current (i )
by measuring the thickness of the polymers by SEM.
D
2126
J. Mater. Chem., 1999, 9, 2123–2131

sweep (Fig. 2a, dotted line). Scanning the oxidative and
reductive regions separately (solid line) results in no charge
trapping peaks. Similar charge trapping phenomena have been
observed in other thienyl- or Ru(bpy) -based polymers.32 While
3
different explanations for charge trapping have been reported,32
we believe it is likely due to a structural change in the polymers
during the reduction process.
The conductivity profile in CH Cl also displays two
2
2
conductivity maxima (Fig. 2b) associated with the oxidized
tetrathienyl linker and the reduced Ru(bpy) centers, with the
3
maximum conductivity (1.2×10−3 S cm−1) associated with the
higher than the conductivity of a highly conductive non-
Ru(bpy) complexes. This value is an order of magnitude
3
conjugated polymer. For example, poly(Os(bpy) (4-vpy) ) (4-
vpy=4-vinylpyridine) was shown by Chidsey and Murray to
have a conductivity of 1.2×10−4 S cm−1.12e
2
2
Bipyridine 2, with the pseudo-meta relationship between the
bithienyl units, is expected to have limited conjugation.
Nevertheless, CH Cl solutions of 2 can be oxidatively poly-
2
2
merized to generate red films of poly(2). The CV of poly(2) is
shown in Fig. 3a and is characterized by a broad, unresolved
tetrathienyl oxidative process centered at 0.68 V. Similar to
poly(1),1 poly(2) also exhibits a stable reduction wave centered
at −2.13 V. Charge trapping processes are also observed when
sweeping the entire oxidative and reductive regions. As
expected for these polymers with no extended conjugation due
to the meta linkage, no detectable conductivity (our detection
limit is 10−6–10−7 S cm−1) was observed under our
experimental conditions.
Films of poly(Ru(2) ) exhibit cyclic voltammograms that
are very different to that of poly(2). They are characterized by
3
Fig. 2 (a) Cyclic voltammograms of poly(Ru(1) ) in 0.1 M
two well defined tetrathienyl-based redox waves at 0.57 and
0.85 V (Fig. 3b) as well as two Ru(bpy) -based redox waves at
−1.60 and −1.76 V. Again we believe the charged thienyl
3
Bu NPF –CH Cl on 5 mm interdigitated microelectrodes at a sweep
4
6
2 2
3
rate of 50 mV s−1. The dotted lines indicate the first scan in each
direction from −0.4 V and the solid lines show the third scan. (b)
Drain current profile of poly(Ru(1) ) on the same electrode at a
groups shift the Ru2+/3+ redox couple to more positive poten-
a region where poly(2) is inactive. The reduction potentials of
3
tials. These two Ru(bpy) -based reduction processes occur in
sweep rate of 3 mV s−1 with an offset potential of 40 mV.
3
poly(Ru(2) ) are more negative than those of poly(Ru(1) ),
which follows the trend observed in the monomeric complexes.
3
3
based reduction process is approximately 1.9 times smaller
than that passed due to the tetrathienyl oxidation.
However, in contrast to poly(Ru(1) ), the reduction potentials
of poly(Ru(2) ) are now more negative than those of its
3
For
a
poly(Ru(L) (bpy) )2+ complex three distinct
x
3−x
3
electrochemical processes are expected: (1) the oxidation of
the tetrathienyl groups, (2) the Ru2+/3+ couple, and (3) a
primarily ligand-based reduction of the metal bipyridyl groups.
Previous investigations2 in our laboratory have established
that poly(1) and its metal complexes undergo two sequential
one-electron tetrathienyl-based oxidation processes. The first
occurs below the expected potential of the Ru2+/3+ redox
couple. However, while the second anodic wave may obscure
a Ru2+/3+ process, in some cases we believe that positive
charge from the oxidized tetrathienyl groups shifts the Ru2+/3+
wave to higher potentials than would be predicted from the
optical band gaps. The electrochemical behavior of
monomer. Continuous sweeping of the reduction region results
in a slow decline in the current of the reduction waves,
indicating slow decomposition of the polymer. The coulombic
ratio of these two processes (Q 5Q ) was found to be 2.351,
indicating an average of 4.6 dithienyl groups underwent
ox red
oxidative coupling during the anodic polymerization.
The conductivity profile of poly(Ru(2) ) on interdigitated
3
microelectrodes is shown in Fig. 3c. It was found that while
the Ru(bpy) -centered reduction process was less stable than
the tetrathienyl-based oxidation, both of these regions display
3
similar conducitivity. As expected for redox conduction, the
conductivity profile displays a maximum at −1.76 V with a
small shoulder at −1.60 V, which are coincident with the
potentials of the two reduction processes observed in CV.
poly(Ru(1) ) is very similar to that of complexes of 1 with
3
non-redox active metals and hence we believe that the Ru2+/3+
couple is shifted to higher potential as a result of the combined
electrostatic and inductive effects from the oxidized ligands.
Our understanding of the nature of the electrochemistry also
provides a means to evaluate the degree of polymerization of
the thienyl groups. Considering that only ligand-based electro-
chemistry occurs below the decomposition potential for
Poly(Ru(2) ) exhibits a slightly higher conducting current
when oxidized, with the conductivity reaching a maximum at
3
0.85 V accompanied by a shoulder at 0.58 V. The correlation
between the redox potentials of the tetrathienyl waves and the
conductivity suggests that the anodic conductivity also results
from hopping between charges localized on the thienyl moiet-
poly(Ru(1) ), we expected that, if all of the bithienyl moieties
ies. The conductivity maximum of poly(Ru(2) ) observed for
the Ru(bpy) -based processes is 3.3×10−3 S cm−1, which is
indicates that the self exchange conductivity between adjacent
3
3
underwent oxidative coupling, a 351 coulombic ratio of the
thienyl-based wave to the Ru(bpy) -based waves would be
observed. Non-polymerized bithienyl groups oxidize at a higher
3
2.7 times greater than that observed for poly(Ru(1) ). This
3
3
potential, hence this ratio provides a measure of the tetrathio-
phene-to-Ru ratio. Based on this figure, we calculate that each
ruthenium complex is, on average, connected to two neighbors.
ruthenium complexes is further enhanced by having the
ruthenium bipyridyl complexes connected by a tetrathienyl
bridge in the para position. It is important to emphasize that
the Ru2+ metal center facilitates conduction resulting from the
oxidized tetrathienyl units relative to poly(2), which had a
Also observed in the poly(Ru(1) ) CV is an electrochemically
irreversible charge trapping wave during the first reductive
3
J. Mater. Chem., 1999, 9, 2123–2131
2127

Fig. 4 (a) Cyclic voltammograms of poly(Ru(3) ) in 0.1 M
3
Bu NPF –CH Cl on 5 mm interdigitated microelectrodes at a sweep
4
6
2 2
rate of 50 mV s−1 in each direction from −0.6 V. (b) Drain current
profile of poly(Ru(3) ) on the same electrode at a sweep rate of
3
5 mV s−1 with an offset potential of 40 mV.
of these signals was found to be 1.2651, close to the ideal
1.551, indicative of an average coupling of 2.5 bithienyl units
per monomer during electrochemical polymerization. The
higher polymerization ratio observed for poly(Ru(3) ) may be
3
due to the less crowded nature of Ru(3) , allowing for higher
3
crosslinking. In spite of the reduced stability of poly(Ru(3) )
3
to reduction, conductivity measurements were successfully
performed (Fig. 4b). Like the other homoleptic polymers,
poly(Ru(3) ) shows redox conductivity in both the oxidative
and reductive regions. We have determined the conductivity
Fig. 3 (a) Cyclic voltammograms of poly(2) in 0.1 M
Bu NPF –CH Cl on 5 mm interdigitated microelectrodes at a sweep
3
4
6
2 2
rate of 50 mV s−1 in each direction from −0.6 V. (b) Cyclic
due to self-exchange between the ruthenium complexes to be
1.73×10−3 S cm−1. The intermediate conductivity value
between poly(Ru(1) ) and poly(Ru(2) ) suggests that, while
voltammograms of poly(Ru(2) ). Conditions as in (a). (c) Drain
3
current profile of poly(Ru(2) ) on the same electrode at a sweep rate
3
of 5 mV s−1 with an offset potential of 40 mV.
3
3
the redox conductivity is enhanced by having the tetrathienyl
bridges para to the ruthenium, a higher number of linkages
seems to facilitate a higher self-exchange between neighboring
ruthenium complexes.
much lower (<10−6 S cm−1) conductivity value. In effect, the
para relationship between the Ru2+ and the tetrathienyl groups
creates a conjugation path. An additional factor that may
contribute is that ruthenium complexation exerts changes in
the orbital energies which facilitate conductivity. Other features
which have not fully been investigated at present include the
effects of chain–chain interactions to result in enhanced
interchain conduction.
We also investigated structures wherein Ru(bpy) complexes
are tethered to poly(1) or poly(2) backbones. The cyclic
2
voltammogram of poly(Ru(bpy) (1)) is shown in Fig. 5a. There
are a number of significant differences in comparison to
poly(Ru(1) ). In the reductive region, unlike poly(Ru(1) ),
2
3
3
only one reduction process is observed, which is coincident
with monomer reduction. In the oxidative region there are two
waves of unequal charge. In comparing the first tetrathienyl-
based redox wave to the ruthenium reduction wave, the second
oxidation wave does not appear to be a one-electron process.
The larger nature of the second oxidation wave suggests that
a Ru2+/3+ couple may be present in addition to a second one-
electron oxidation of the tetrathienyl group. This is also
consistent with a smaller electrostatic and inductive pertur-
bation caused by having only one oxidizable ligand attached
to the Ru2+ center. The coulombic ratio of the oxidation to
Complex Ru(3) was designed to have only one bithienyl
substituent per bipyridine ligand. Keeping this in mind, the
3
electrochemistry of poly(Ru(3) ) is very similar to that of
poly(Ru(2) ) (Fig. 4a). Two Ru(bpy) -based reduction waves
3
3
3
were observed at −1.67 and −1.79 V; however, the peak
current of these waves decreased with repeated sweeping. The
potentials of the reduction waves are more negative than those
of poly(Ru(2) ), consistent with comparisons of the monomeric
species. In the tetrathienyl oxidation region two well defined
waves are observed at 0.55 and 0.84 V. The coulombic ratio
3
2128
J. Mater. Chem., 1999, 9, 2123–2131

thienyl-based redox processes that exhibit high redox conduc-
tivity. Systematic studies of the polymer structure revealed the
importance of electronic interactions between the metal com-
plexes through a conjugated polymer backbone. The highest
conductivities observed in these systems resulted from a 4,4∞-
and 4-bithienyl substitution pattern on the bipyridine ligand,
indicating that, when the ruthenium complexes are in direct
communication through a conjugated organic bridge, self-
exchange between ruthenium complexes is more favorable
than through space. The ruthenium centers also induce elec-
tronic coupling between thienyl groups that ordinarily are not
conjugated. This fact is readily apparent from conductivity
comparisons
between
poly(2),
poly(Ru(2) ),
and
3
poly(Ru(bpy) (2)). We have also shown that cross linking in
these polymers is an important contributor to high polymer
2
conductivity and stability. Based upon previous results with
related systems,2,3 further enhancements in the metal-centered
redox conductivity will be realized by redox matching the
metal centered redox wave with the organic backbone to
provide an isoenergetic conduit for electron hopping. Further
work on the sensory and catalytic properties of this class of
hybrid polymers is ongoing.
Experimental
General procedures
Air- and moisture-sensitive reactions were carried out in
oven-dried glassware using standard Schlenk techniques under
an inert atmosphere of dry argon. Anhydrous DMF, CH Cl ,
2
2
and CH CN were obtained as sure-seal bottles and used as
3
Fig. 5 (a) Cyclic voltammograms of poly(Ru(bpy) (1)) in 0.1 M
received. Other reagents were used as received from Aldrich
2
Bu NPF –CH Cl on 5 mm interdigitated microelectrodes at a sweep
unless otherwise noted. The NMR spectra were recorded with
a Bruker AC-250 (1H) or Varian 300 or 500 MHz spectrometer
(1H and 13C), UV–Vis absorption spectra on a Hewlett-
Packard 8453 diode array spectrophotometer. Electrochemical
studies were performed under an air-free dry-box under
reduced laboratory lighting using a one compartment cell with
either a platinum button or 5 mm interdigitated microelectrode
as the working electrode, a platinum coil counter electrode
and an isolated silver wire reference electrode. The electrolyte
solutions used for all electrochemistry and conductivity
measurements were 0.1 M Bu NPF in CH Cl . All electro-
4
6
2 2
rate of 50 mV s−1 in each direction from −0.25 V. (b) Cyclic
voltammograms of poly(Ru(bpy) (2)) sweeping in each direction
2
from −0.6 V. Conditions as in (a).
reduction waves was approximately 251. Conductivity studies
on interdigitated microelectrodes reveal that poly(Ru(bpy) (1))
2
has a maximum conductivity of ca. 1×10−3 S cm−1 at 0.96 V,
conductivity due to the reduction of the ruthenium bipyridyl
nearly the same as that of poly(Ru(1) ). The self-exchange
3
complexes is, however, diminished, being nearly a third of the
value of poly(Ru(1) ). This difference shows that a cross-
linked polymer network facilitates conduction through three
dimensions, rather than just by a simple one-dimensional
electron hopping mechanism.
The CV of poly(Ru(bpy) (2)) also shows differences in
comparison to poly(Ru(2) ). The reductive region is charac-
terized by a single redox wave at −1.92 V (Fig. 5b). The
negative shift of this wave in comparison to the monomer is
4
6
2 2
chemical potentials are reported with reference to the ferro-
3
cene–ferrocenium (Fc–Fc+) redox couple. The thickness of
poly(Ru(1) ) was determined by profilometry on a Dektak
3
8000 instrument.
2
Preparations
3
4-Nitro-2,2∞-bipyridine N,N∞-dioxide. In a 50 ml round
more substantial than for poly(Ru(2) ), which could be caused
by the decreased number of electron donating groups on the
bottom flask, 8 g (79.12 mmol) of KNO and 5 g (26.57 mmol)
of 2,2∞-bipyridine N,N∞-dioxide21 in 13 mL of concentrated
3
3
bipyridine ligands. In the oxidative region the peak areas are
again unequal. Integrating the area under the redox waves
reveals a 152 ratio between the reductive and oxidative regions.
Conductivity measurements performed on these polymers
H SO (95–98%) were heated at 100 °C for 24 h. After cooling
2
4
to room temperature, the reaction mixture was poured into
500 ml of water and stirred for 2 h. The volume of the aqueous
solution was reduced to 150 mL, and neutralized to pH 8. The
revealed that the conductivity associated with the Ru(bpy)
reduction was diminished by an order of magnitude (s
aqueous solution was thoroughly extracted with CHCl .
3
3
Combination and evaporation of the CHCl fractions pro-
3
=
max
3×10−4 S cm−1 at −1.60 V) compared to that of
polymer architecture rather than a cross linked polymer.
duced the crude mononitro compound which was further
poly(Ru(2) ). This result was expected due to the linear
purified by chromatography (1% MeOH–CHCl ) to afford
3
3
1.01 g (4.33 mmol, 16%) of 4-nitro-2,2∞-bipyridine N,N∞-dioxide
Unfortunately, the polymer has limited stability and the
electroactivity diminished with repeated sweeping.
(mp 198 °C, decomp.). 1H NMR (500 MHz, DMSO-d ): d
8.61 (d, 2 H, J=3.5), 8.56 (d, 2 H, J=7), 8.39 (d, 2 H, J=7),
6
8.32 (dd, 2 H, J=7 and 3), 7.71 (dd, 2 H, J=8 and 2), 7.58
(td, 2 H, J=7.5 and 2) and 7.46 (t, 2 H, J=7.5 Hz). 13C
Conclusion
NMR (125 MHz, DMSO-d ): d 143.69, 141.15, 140.8, 140.51,
6
We have synthesized conducting polymer transition metal
139.18, 128.75, 127.72, 124.78, 123.20 and 121.33. MS: m/z
hybrid materials based on bithienyl-substituted Ru(bpy)
derivatives. These materials display metal bipyridyl-based and
234 ([M+H]+). HRMS (FAB): found m/z 234.0516
3
([M+H]+); calc. for C H N O 234.0515.
J. Mater. Chem., 1999, 9, 2123–2131
10
8 3 4
2129

4-Bromo-2,2∞-bipyridine N,N∞-dioxide. To a suspension of
1.0 g (4.29 mmol) of 4-nitro-2,2∞-bipyridine N,N∞-dioxide in
15 mL of glacial acetic acid at 60 °C are added 3.0 mL
C H N S 321.0520. Calc. for C H N S : C, 67.47; H, 3.77;
N, 8.74. Found: C, 67.23; H, 3.54; N, 8.31%.
18 13 2 2
18 12 2 2
(40.58 mmol) of CH COBr. The mixture was refluxed for 2 h
Tris[4,4∞-Bis(5–(2,2∞-bithienyl))-2,2∞-bipyridine)]ruthenium
3
and then cooled to room temperature. The solution was
bis(hexafluorophosphate) (Ru(2) ). A 30 mL solution of DMF
3
poured into 150 g of crushed ice, neutralized with 15%
Na CO , and then dried under vacuum. The resulting solid
containing 0.1 g of compound 2 (0.2 mmol) and 0.0143 g
(0.068 mmol) RuCl ·xH O was refluxed under N for 12 h.
2
3
3
2
2
was suspended in MeOH, stirred for 3 h, and then filtered.
The filtrate was evaporated and the resulting solid dried under
vacuum to yield 0.74 g (2.77 mmol, 64%) of 4-bromo-2,2∞-
bipyridine N,N∞-dioxide as a tan solid (mp >260 °C). 1H
After removing the DMF, the residue was dissolved in EtOH
and filtered. The filtrate was treated with NH PF in EtOH
4
6
and cooled to 0 °C overnight. The resulting red precipitate was
collected and dried under vacuum to afford crude Ru(2) ,
3
NMR (500 MHz, DMSO-d ): d 8.35 (d, 1 H, J=6.5), 8.28 (d,
which was further purified by recrystallization from
6
1 H, J=7), 7.99 (d, 1 H, J=2.5), 7.76 (dd, 1 H, J=7 and 3),
acetone–MeOH to afford 0.05 g (40%) red solid (mp 248 °C,
7.67 (dd, 1 H, J=7.5 and 2), 7.53 (td, 1 H, J=7.5 and 2) and
7.43 (td, 1 H, J=7.5 and 1). 13C NMR (125 MHz, DMSO-
decomp.). 1H NMR (250 MHz, acetone-d ): d 9.25 (s, 6 H),
6
8.22 (d, 6 H), 8.01 (d, 6 H), 7.78 (dd, 6 H), 7.57 (d, 6 H),
d ): d 150.71, 151.0, 149.47, 137.62, 133.29, 127.09, 124.92,
7.49 (d, 6 H), 7.445 (d, 6 H) and 7.15 (t, 6 H). 13C NMR
6
123.3 and 120.85. MS: m/z 267 ([M+H]+). HRMS (FAB):
266.9769.
(partially) (125 MHz, acetone-d ): d 176.20, 176.17, 176.11,
6
found m/z 266.9773 ([M+H]+); calc. for C H BrN O
176.08, 176.07, 176.02, 145.18, 114.37 and 96.13. Calc. for
10
8
2 2
C H F N P RuS ·8H O: C, 47.08; H, 3.24; N, 4.23. Found:
78 48 12 6 2
12
2
C, 46.67; H, 3.72; N, 4.61%.
4-Bromo-2,2∞-bipyridine. A suspension of 0.4 g (1.50 mmol)
of crude 4-bromo-2,2∞-bipyridine N,N∞-dioxide in 12 mL of
Tris[4-(5-(2,2∞-bithienyl))-2,2∞-bipyridine]ruthenium bis(hex-
anhydrous CHCl was cooled to −3 °C and 1.4 mL
afluorophosphate) (Ru(3) ). This compound was prepared by
3
3
(14.74 mmol) of PBr were added. The mixture was refluxed
a procedure similar to that of Ru(2) except using 3 as the
3
3
for 75 min, cooled and poured into ice–water. After phase
starting material (mp 260 °C, decomp.). 1H NMR (500 MHz,
separation, the organic layer was extracted repeatedly with
distilled water, and the aqueous extracts were combined.
Neutralization of the aqueous solution with 25% NaOH
solution resulted in a white precipitate which was dried under
vacuum to afford 0.21 g (0.893 mmol, 60%) of 4-bromo-2,2∞-
acetone-d ): d 9.09 (d, 2 H), 8.27 (m, 2 H), 8.15 (m, 1 H),
6
8.03 (m, 1 H), 7.76, (s, 1 H), 7.64 (s, 1 H), 7.58 (s, 1 H), 7.48
(s, 1 H), 7.44 (s, 1 H) and 7.16 (s, 1 H). The poor solubility
prevented characterization by 13C NMR. Calc. for
C H F N P RuS : C, 47.96; H, 2.68; N, 6.21. Found: C,
54 36 12 6 2
6
bipyridine. 1H NMR (250 MHz, CDCl ): d 8.67 (d, 1 H),
47.42; H, 2.76; N, 6.05%.
3
8.609 (s, 1 H), 8.46 (d, 1 H), 8.37 (d, 1 H), 7.81 (t, 1 H), 7.46
(d, 1 H) and 7.33 (t, 1 H). MS: m/z 235 ([M+H]+).
Bis(2,2∞-bipyridine)[5,5∞-bis(5-(2,2∞-bithienyl))-2,2∞-
bipyridine]ruthenium bis(hexafluorophosphate) (Ru(bpy) (1)).
A 50 mL Schlenk flask was charged with 50 mg (0.103 mmol)
2
4,4∞-Bis(5-(2,2∞-bithienyl))-2,2∞-bipyridine
2.
0.88 g
(1.9 mmol) of 5-(tributylstannyl)-2,2∞-bithiophene, 0.2 g
(0.64 mmol) of 4,4∞-dibromo-2,2∞-bipyridine, and 0.028 g
(0.0399 mmol, 0.05 equivalent) of trans-dichlorobis(triphenyl-
phosphine)palladium() were combined in 60 mL of DMF
and heated at 80–90 °C for 8 h. After removal of the DMF,
the resulting solid was chromatographed (silica gel, 2%
of compound 1 and 50 mg (0.103 mmol) of cis-Ru(bpy) Cl
2
2
in 25 mL of anhydrous DMF. The red slurry was heated to
reflux for 12 h. After cooling to room temperature, the solution
was filtered to remove any insoluble material. To the wine red
filtrate was added a saturated EtOH solution of NH PF to
4
6
result in a flocculent brick-red precipitate, which was filtered
off, washed with EtOH and dried under vacuum to afford
39 mg (0.0328 mmol, 32%) of dark red solid (mp >250 °C).
MeOH–CHCl ) to give compound 2 as a yellow solid in 60%
3
yield. For large scale reactions recrystallization is suggested.
1H NMR (500 MHz, CDCl ): d 8.70 (d, 2 H, J=5), 8.65 (d,
2 H, J=1.5), 7.59 (d, 2 H, J=4), 7.51 (dd, 2 H, J=5 and 2),
1H NMR (300 MHz, acetone-d ): d 8.93 (d, 1 H, J=8.1), 8.85
(d, 1 H, J=7.8), 8.81 (d, 1 H, J=8.1), 8.44 (dd, 1 H, J=8.7
3
6
7.28 (td, 4 H, J=5 and 1.5), 7.23 (d, 2 H, J=4) and 7.07 (dd,
2 H, J=5 and 3.5 Hz). The poor solubility of this compound
prevented characterization by 13C NMR. MS: m/z 485
([M+H]+). HRMS (FAB): found m/z 485.0280 ([M+H]+);
calc. for C H N S 485.0275. Calc. for C H N S : C, 64.46;
and 2.1), 8.34–8.32 (m, 2 H), 8.25–8.20 (m, 2 H), 8.00 (d,
1 H, J=1.8), 7.72 (ddd, 1 H, J=7.65, 5.7 and 1.5), 7.61 (ddd,
1 H, J=7.58, 5.7, and 1.2), 7.54 (dd, 1 H, J=4.95 and 1.2),
7.41 (d, 1 H, J=3.9), 7.32 (dd, 1 H, J=3.75 and 1.2), 7.30 (d,
1 H, J=3.9), 7.12 (dd, 1 H, J=5.25 and 3.9 Hz). The poor
solubility prevented characterization by 13C NMR. MS: m/z
26 17 2 4
26 16 2 4
H, 3.33; N, 5.79. Found: C, 63.13; H, 3.33; N, 5.82%.
898 ([M−2PF +H]+). HRMS (FAB): found m/z 899.0674
6
4-(5-(2,2∞-Bithienyl))-2,2∞-bipyridine 3. 0.77 g (1.7 mmol) of
5-(tributylstannyl)-2,2∞-bithiophene, 0.2 g (0.85 mmol) of 4-
bromo-2,2∞-bipyridine, and 0.06 g (0.085 mmol, 0.05 equival-
ent) of trans-dichlorobis(triphenylphosphine)palladium()
were mixed in 60 mL DMF and heated at 80–90 °C for 6 h
under argon. After removal of the DMF, the resulting solid
was chromatographed (silica gel, 2% MeOH–CH Cl ) to give
([M-2PF +H]+); calc. for C H N RuS 899.0693. Calc. for
46.53; H, 2.69; N, 7.12%.
6
46 33
6
4
C H F N P RuS : C, 46.50; H, 2.71; N, 7.07. Found: C,
46 32 12 6 2
4
Bis(2,2∞-bipyridine)[4,4∞-bis(5-(2,2∞-bithienyl))-2,2∞-
bipyridine]ruthenium bis(hexafluorophosphate) (Ru(bpy) (2)).
2
A 50 mL Schlenk flask was charged with 50 mg (0.103 mmol)
2
2
0.15 g (0.468 mmol, 55%) of compound 3 as a yellow solid
of compound 2 and 50 mg (0.103 mmol) of cis-Ru(bpy) Cl .
2
2
(mp 112–113 °C). 1H NMR (500 MHz, CDCl ): d 8.73 (dm,
25 mL of degassed EtOH were added and the dark red slurry
was refluxed for 12 h. After cooling to room temperature, the
solution was filtered to remove any insoluble material. To the
wine red filtrate was added a saturated EtOH solution of
NH PF to result in a flocculent brick-red precipitate, which
3
1 H, J=5), 8.64 (d, 2 H, J=5.5), 8.62 (d, 1 H, J=2), 8.43 (d,
1 H, J=8), 7.85 (td, 1 H, J=7.75 and 2), 7.58 (d, 1 H, J=4),
7.48 (dd, 1 H, J=5.25 and 2), 7.35 (ddd, 1 H, J=7.5 and 4.75
and 3.5), 7.27 (td, 2 H, J=7 and 1), 7.22 (d, 1 H, J=4) and
7.06 (dd, 1 H, J=4.75 and 3.5 Hz). 13C NMR (125 MHz,
4
6
was filtered off, washed with EtOH and dried under vacuum
to afford 44 mg (0.037 mmol, 36%) of brick red solid
CDCl ): d 156.81, 155.86, 149.78, 149.18, 142.02, 139.81,
3
139.17, 136.95, 136.86, 128.01, 126.36, 125.15, 124.73, 124.34,
(mp>250 °C). 1H NMR (500 MHz, acetone-d ): d 9.20 (d,
6
123.91, 121.22, 119.39 and 116.78. MS: m/z 321 ([M+H]+).
2 H, J=2), 8.86 (d, 2 H, J=4), 8.27–8.25 (m, 2 H), 8.24 (dd,
HRMS (FAB): found m/z 321.0516 ([M+H]+); calc. for
2 H, J=3.75 and 1.5), 8.22 (dd, 2 H, J=4 and 1.5), 8.09
2130
J. Mater. Chem., 1999, 9, 2123–2131

1984, 106, 1991; (e) C. E. D. Chidsey and R. W. Murray, J. Phys.
Chem., 1986, 90, 1479; ( f) P. Denisevich, K. W. Willman and
R. W. Murray, J. Am. Chem. Soc., 1981, 103, 4727.
13 V. Grosshenny, A. Harriman, J. P. Gisselbrecht and R. Ziesel,
J. Am. Chem. Soc., 1996, 118, 10315.
14 J. A. Moss, R. Argazzi, C. A. Bignozzi and T. J. Meyer, Inorg.
Chem., 1997, 36, 762.
15 S. C. Rasmussen, D. W. Thompson, V. Singh and J. D. Peterson,
Inorg. Chem., 1996, 35, 3449.
16 E. W. Neuse, J. Macromol. Sci., Chem., 1981, A16, 3 and refs.
therein.
(dm, 2 H, J=2), 8.01 (s, 2 H), 8.00 (d, 2 H, J=4), 7.74 (dd,
2 H, J=6.25 and 2.5), 7.62 (dtd, 4 H, J=7.5, 5.75 and 1),
7.58 (dd, 2 H, J=5 and 1), 7.49 (d, 2 H, J=4), 7.46 (dd, 2 H,
J=3.75 and 1.5) and 7.17 (dd, 2 H, J=5.25 and 4 Hz). The
poor solubility prevented characterization by 13C NMR. MS:
m/z 897 ([M−2PF +H]+). HRMS (FAB): found m/z 899.0682
6
([M-2PF +H]+); calc. for C H N RuS 899.0693. Calc. for
46.25; H, 2.62; N, 6.74%.
6
46 33
6
4
C H F N P RuS : C, 46.50; H, 2.71; N, 7.07. Found: C,
46 32 12 6 2
4
17 H. W. Segawa, F.-P. Wu, N. Nakayama, H. Maruyama,
S. Sagisaka, N. Higuchi, M. Fujitsuka and T. Shimidzu, Synth.
Met., 1995, 71, 2151; J. L. Reddinger and J. R. Reynolds,
Macromolecules, 1997, 30, 673; Synth. Met., 1997, 84, 225; Chem.
Mater., 1998, 10, 3; 1236.
18 R. P. Kingsborough and T. M. Swager, Prog. Inorg. Chem., 1999,
48, 123.
Acknowledgements
We acknowledge funding from the Office of Naval Research
and Union Carbide Corporation.
19 C. P. Whittle, J. Heterocycl. Chem., 1977, 14, 191.
20 G. Maerker and F. H. Case, J. Org. Chem., 1958, 80, 2745.
21 S. Anderson, E. C. Constable, K. R. Seddon, J. E. Turp,
J. E. Baggot and M. J. Pilling, J. Chem. Soc., Dalton Trans.,
1985, 2247.
22 C. M. Elliot and E. J. Hershehart, J. Am. Chem. Soc., 1982,
104, 7519.
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