Synthesis and characterisation of poly(bipyridine)ruthenium complexes as building blocks for heterosupramolecular arrays

Article abstract of DOI:10.1002/ejic.200701303

Poly(bipyridine)ruthenium complexes with carboxylate anchor groups are key components in dye-sensitised solar cells. In this contribution, an improved microwave-assisted synthetic procedure is presented for the important building block [RuCl₂(dcmb)₂] (dcmb = 4,4′-dimethoxycarbonyl- 2,2′-bipyridine), which results in short reaction times and high purity. The methyl esters are easily deprotected to give free carboxylate functions. In addition, a full structural, spectral and electrochemical characterisation of a series of complexes with the general formula [Ru(dcmb)_3-n(tbbpy) _n](PF₆)₂ with n = 0-3 and tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine is presented. The location of the lowest-energy metal-to-ligand charge transfer (MLCT) excited state is investigated by resonance Raman spectroscopy for selected complexes. The results obtained indicate that the nature of the excited state that is populated is dependent on the excitation wavelength. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200701303

FULL PAPER
DOI: 10.1002/ejic.200701303
Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes as
Building Blocks for Heterosupramolecular Arrays
Matthias Schwalbe,[a] Bernhard Schäfer,[a] Helmar Görls,[a] Sven Rau,*[a]
Stefanie Tschierlei,[b] Michael Schmitt,[b] Jürgen Popp,[b] Gavin Vaughan,[c]
William Henry,[d] and Johannes G. Vos[d]
Keywords: Ruthenium / Bipyridine / Microwave-assisted reaction / Raman spectroscopy
Poly(bipyridine)ruthenium complexes with carboxylate an-
chor groups are key components in dye-sensitised solar cells.
In this contribution, an improved microwave-assisted syn-
thetic procedure is presented for the important building
block [RuCl2(dcmb)2] (dcmb = 4,4Ј-dimethoxycarbonyl-2,2Ј-
with the general formula [Ru(dcmb)3–n(tbbpy)n](PF6)2 with n
= 0–3 and tbbpy = 4,4Ј-di-tert-butyl-2,2Ј-bipyridine is pre-
sented. The location of the lowest-energy metal-to-ligand
charge transfer (MLCT) excited state is investigated by reso-
nance Raman spectroscopy for selected complexes. The re-
bipyridine), which results in short reaction times and high sults obtained indicate that the nature of the excited state
purity. The methyl esters are easily deprotected to give free
carboxylate functions. In addition, a full structural, spectral
and electrochemical characterisation of a series of complexes
that is populated is dependent on the excitation wavelength.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
surface-bound complexes. For instance, their long-life sta-
bility relies on a stable redox system, like the RuII/RuIII cou-
ple, and a stable bond between pigment and surface, which
has indeed been observed for carboxylate functions. The
strength of the binding of the ruthenium complexes in-
creases with increasing number of anchoring groups per
molecular unit. Unfortunately, the synthesis and, in particu-
lar, the purification of metal complexes with multiple carb-
oxylate functions is very challenging, and the availability of
efficient synthetic pathways towards the required functional
building blocks is an important issue. Previously, we have
shown that poly(bipyridine)ruthenium complexes contain-
ing 2,2Ј-bipyridine (bpy), 4,4Ј-dimethyl-2,2Ј-bipyridine
(dmbpy) and 4,4Ј-di-tert-butyl-2,2Ј-bipyridine (tbbpy) can
be prepared in high yields of up to 95% by microwave-
assisted reactions.[10] In this contribution, we describe the
extension of this methodology to the synthesis of a series
of ruthenium complexes containing up to six carboxylate
anchoring groups. By using appropriate protecting groups,
improved yields and reduced reaction times are observed.
We have utilised two different ligands to prepare a series
of model complexes and to evaluate the synthetic flexibility
of the methodology. In addition, the influence of the intro-
duction of dimethoxycarbonyl-based ligands on the chemi-
cal and photophysical properties is investigated. The ligands
4,4Ј-dimethoxycarbonyl-2,2Ј-bipyridine (dcmb) and 4,4Ј-di-
tert-butyl-2,2Ј-bipyridine (tbbpy) are used to prepare the
complexes [Ru(dcmb)3–n(tbbpy)n](PF6)2 with n = 0–3 (2, 3,
4, 5), as shown in Figure 1. The latter ligand, i.e. tbbpy,
induces solubility in less polar solvents, whereas the former
can easily be deprotected and bound to TiO2 surfaces. As
Introduction
Over the last 20 years poly(bipyridine)ruthenium com-
plexes have been extensively studied because of their excep-
tional photochemical properties.[1] In particular, their abil-
ity to function as tuneable pigments in dye-sensitised solar
cells (dssc) has attracted considerable attention. Grätzel et
al. and other groups reported that complexes with carb-
oxylate anchor groups bind strongly to the titanium dioxide
surface of such solar cells.[2] The majority of the complexes
investigated utilise 4,4Ј-dicarboxy-2,2Ј-bipyridine as the an-
choring ligand. It has been shown that this ligand facilitates
photoinduced electron transfer from the excited ruthenium
centre to the surface, which is crucial for the efficiency of
dssc devices.[3]
In addition to their application in solar cells,[9] the at-
tachment of ruthenium complexes to surfaces allows for a
range of other potential applications ranging from sensors[4]
to photocatalysis,[5] molecular switches,[6] electromechanical
motors[7] or light-collecting molecular antenna.[8] A number
of chemical properties are important for the application of
[a] Institute of Inorganic and Analytical Chemistry, FSU – Jena,
August-Bebel-Str. 2, 07743 Jena, Germany
Fax: +49-3641-948102
E-mail: sven.rau@uni-jena.de
[b] Institute of Physical Chemistry, FSU – Jena,
Helmholtzweg 4, 07743 Jena, Germany
[c] European Synchrotron Radiation Facility (ESRF),
B. P. 220, 38043 Grenoble Cedex, France
[d] National Centre for Sensor Research, School of Chemical
Sciences, Dublin City University,
Dublin 9, Ireland
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Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes
it is very important to know the location of the excited state
Results and Discussion
Synthesis of the Ruthenium Complexes
for a rational design of photo- and redox active compounds,
we investigated them using resonance Raman spectroscopy.
The results indicate that the nature of the excited state that
is populated in the heteroleptic complexes is dependent on
the excitation wavelength.
4,4Ј-Dimethoxycarbonyl-2,2Ј-bipyridine (dcmb) was pre-
pared starting from 4,4Ј-dimethyl-2,2Ј-bipyridine, which can
be oxidised with either KMnO4 (70% yield)[12] or K2Cr2O7
as the oxidising agent. The latter gave better yields of the
dicarboxy compound (90%) as was seen previously,[13] and
we therefore used this method. The subsequent protection
of the acid as the methyl ester gives the desired ligand in an
overall yield of 60% (starting from the dimethyl analogue).
Protection was carried out as the presence of free carboxyl-
ate functions would induce severe problems in the workup
of the desired complexes, as these compounds start to be-
have similarly to surfactants. Furthermore, the synthesis of
such ruthenium complexes containing free carboxylate
functions requires harsh conditions and the use of pressure
vessels, as shown by Pakkanen et al.[14] It is highly likely
that multiple protonation/deprotonation reactions play a
detrimental role and lead to limiting yields and prolonged
Figure 1. Structure of the synthesised complexes.
A similar series of complexes with the general formula reaction times. The synthesis of heteroleptic poly(bipyrid-
[Ru(decbpy)n(dmbpy)3–n](PF6)2 with n = 0–3, decbpy = di- ine) compounds of this type generally starts with the prepa-
ethoxycarbonylbipyridine and dmbpy = dimethylbipyridine ration of a ruthenium dichloride as the building block, in
was prepared by Schmehl et al.[11] On the basis of a combi- this case [RuCl2(dcmb)2] (1). This compound can be pre-
nation of absorption, emission and electrochemical mea- pared almost in the same manner as that previously re-
surements, Schmehl et al. suggested that the highest-occu- ported for [RuCl2(tbbpy)2][10] by using microwave irradia-
pied molecular orbital (HOMO) for [Ru(decbpy)3]2+ is low- tion in dry DMF with 2 equiv. dcmb and [RuCl2(cod)]n in
est in energy relative to those of the other compounds in less than 2 h. This is a significant advantage compared to
the series. With an increasing number of dmbpy ligands, an the long (50 h) and lower yielding (78%) thermal reac-
increase in the energy of this orbital was postulated. How- tion.[15] Compound 1 is obtained in over 95% purity after
ever, no solid-state structures or resonance Raman data are a brief workup procedure – removal of DMF from the reac-
presented in this publication to support this interpretation. tion solution, dissolution of the crude product in chloro-
To the best of our knowledge, we present here the most form and precipitation by addition of diethyl ether. No fur-
efficient synthetic procedure for the preparation of dyes for ther purification by column chromatography is required; see
dye-sensitised solar cells, in conjunction with the first com- Figure 2 for the 1H NMR spectrum of the reaction product.
plete structurally and photochemically investigated series of This is the first time that compound 1 has been prepared
complexes of that kind.
in a fast reaction procedure giving high purity and high
1
Figure 2. H NMR spectrum of [RuCl2(dcmb)2] (1) in CD2Cl2.
Eur. J. Inorg. Chem. 2008, 3310–3319
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S. Rau et al.
FULL PAPER
Scheme 1. Synthesis of the compounds 1, 2 and 3.
yield. The efficient access to complex 1 reported here is of the ester compound is stirred in an aqueous solution of
significant importance as 1 represents an essential building sodium hydroxide or sodium carbonate for several hours, as
block in dye-sensitised solar cell architectures.
described in the Experimental Section. The corresponding
The syntheses of [RuCl2(dcmb)2] (1), [Ru(dcmb)3](PF6)2 sodium salt can be isolated in reasonable yields by precipi-
(2) and [Ru(dcmb)2(tbbpy)](PF6)2 (3) are shown in tation with ethanol or tetrahydrofurane. The sodium salts
Scheme 1. Ligand substitution to prepare compounds 2 and show slight solubility in methanol or DMF, from which a
3 was performed in refluxing methanol/water in order to fixation to titanium dioxide surfaces is possible.
avoid high temperatures, which could lead to decarboxyl-
ation. All reactions can be performed in the microwave as
Structures of the Ruthenium Complexes
well by using a methanol/water mixture. Previously, it was
reported that decarboxylation can take place in such reac-
tions when sealed tubes in a microwave oven were used.[16]
This was not observed in our case where we use a pres-
sureless setup. After removal of methanol, the aqueous
solution is filtered to remove excess ligand. Upon addition
of NH4PF6, the desired product is formed as a red
precipitate, which can be isolated and washed with diethyl
ether.
Crystals suitable for single-crystal X-ray analysis were
obtained for compound 1 upon slow evaporation of an ace-
tonitrile/toluene solution containing the compound. Fig-
ure 3 shows an octahedrally coordinated ruthenium centre,
and the two chlorido ligands are in a cis arrangement.[17]
No exchange of chlorido ligands with acetonitrile was ob-
served.
The synthetic approach towards [Ru(dcmb)(tbbpy)2]-
(PF6)2 (4) and [Ru(tbbpy)3](PF6)2 (5) is similar, but starts
from [RuCl2(tbbpy)2].
The introduction of the methyl protecting groups for the
carboxylate functions increases the solubility of the formed
complexes, simplifies workup and improves the yield. With
the ester groups, the solubility is very good in acetonitrile,
acetone and is also good in dichloromethane, whereas com-
plexes with more than two free carboxylate functions per
ruthenium centre become insoluble in these solvents. No
column chromatography was needed for purification of the
obtained complexes. This is another important feature of
the high yield and high purity preparation developed here,
as ester functionalities in ruthenium complexes tend to de-
compose during chromatographical workup, which dimin-
ishes yields and purity.
However, the attachment of ruthenium complexes to
TiO2 surfaces requires the presence of free carboxylate
groups. The free carboxylate functions are obtained when Figure 3. Structural motif of compound 1.
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Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes
Complexes 2– 5 were recrystallised from acetone/water/
methanol solutions. The solid-state structures of com-
pounds 2–5 are presented in Figures 4, 5, 6 and 7, relevant
bond lengths and angles can be found in the captions.
Figure 6. Molecular structure of complex 4 (H atoms and PF6 ions
are omitted for clarity). Selected bond lengths [Å] and bond angles
[°]: Ru–N1 2.068(5), Ru–N2 2.054(5), Ru–N3 2.061(5), Ru–N4
2.063(5), Ru–N5 2.052(5), Ru–N6 2.046(5), N1–Ru–N5 174.95(19),
N2–Ru–N4 175.70(19), N3–Ru–N6 172.30(18), N1–Ru–N2 79.3(2),
N3–Ru–N4 78.19(19), N5–Ru–N6 77.92(19).
Figure 4. Molecular structure of complex 2 (H atoms and PF6 ions
are omitted for clarity). Selected bond lengths [Å] and bond angles
[°]: Ru–N1A 2.061(6), Ru–N1B 2.041(7), Ru–N2A 2.049(6), Ru–
N2B 2.048(7), Ru–N1C 2.056(7), Ru–N2C 2.067(6), N1A–Ru–N2B
175.7(2), N1B–Ru–N2C 175.4(3), N2A–Ru–N1C 175.7(2), N1A–
Ru–N2A 78.6(2), N1B–Ru–N2B 78.9(2), N1C–Ru–N2C 79.1(3).
Figure 7. Molecular structure of complex 5 (H atoms and PF6 ions
are omitted for clarity). Selected bond lengths [Å] and bond angles
[°]: Ru–N1A 2.055(3), Ru–N1 2.055(3), Ru–N2A 2.062(3), Ru–N2
2.062(3), Ru–N3A 2.063(3), Ru–N3 2.063(3), N1A–Ru–N1
78.64(14), N3A–Ru–N2 78.39(10), N2A–Ru–N3 78.39(10), N1A–
Ru–N3 172.43(10), N1–Ru–N3A 172.43(10), N2A–Ru–N2
173.24(14).
Figure 5. Molecular structure of complex 3 (H atoms and PF6 ions
are omitted for clarity). Selected bond lengths [Å] and bond angles
[°]: Ru–N1 2.055(4), Ru–N2 2.059(4), Ru–N3 2.056(4), Ru–N4
2.052(4), Ru–N5 2.059(4), Ru–N6 2.058(4), N1–Ru–N4 172.05(16),
attributed to vibrational effects. The N–Ru–N angles devi-
N2–Ru–N6 174.64(16), N3–Ru–N5 173.84(16), N1–Ru–N2 ate greatly from the ideal 90° value, but this fact is due to
78.63(16), N3–Ru–N4 79.16(17), N5–Ru–N6 78.41(16).
the small bite angle of the bipyridines and agrees well with
known structural parameters in the literature.[14,18] The dis-
All tris(bipyridine) complexes have a similar basic struc-
tortion of the octahedron stems, very likely, from the com-
ture of a distorted octahedrally coordinated ruthenium cen-
bination of bite angle and repulsion of the ligands.
tre. The Ru–N bond lengths vary between 2.041(7) and
2.068(5) Å, and the N–Ru–N bite angles of the bipyridines
vary between 77.92(19)° and 79.3(2)°. No trends in the Ru–
N distances and the N–Ru–N angles are observed. The ef-
Spectroscopic Properties of the Compounds
fect of the methoxycarboxylate substituents in the periphery
All spectroscopic investigations were performed in
of the complexes on the structural parameters around the dichloromethane and acetonitrile. There are slight differ-
ruthenium centre is negligible. For example, no trans effect ences between the UV/Vis spectra in the two different sol-
is observed, and the variation in the bond lengths can be vents because of the different polarity of the solvent. These
Eur. J. Inorg. Chem. 2008, 3310–3319
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S. Rau et al.
Table 1. Absorption and emission maxima in dichloromethane and acetonitrile; extinction coefficients are given in parentheses [–1 cm–1].
FULL PAPER
Complex
λmax [nm]
λmax [nm]
λem [nm] λem [nm] τ [ns]
τ [ns]
τ [ns]
(CH2Cl2)
(CH3CN)
(CH2Cl2) (CH3CN) (aerated CH3CN) (deaerated CH3CN) (aerated CH2Cl2)
5 [Ru(tbbpy)3](PF6)2
2 [Ru(dcmb)3](PF6)2
461
(15700)
464
458
(16000)
467
(19700)
443, 486
604
619
645
681
613
631
657
691
107
603
395
229
730
248
992
678
448
1174
1002
646
(23400)
3 [Ru(dcmb)2(tbbpy)](PF6)2 442, 485
(16200, 18600) (14300, 16900)
4 [Ru(dcmb)(tbbpy)2](PF6)2 425, 494
426, 492
(12900, 12800) (11400, 11000)
differences are, however, far less pronounced when com-
pared with data obtained for some ruthenium complexes
with tetrasubstituted phenanthrolines.[19] In addition, the
emission is stronger in dichloromethane than in acetonitrile,
and the maxima observed are blueshifted by approximately
10 nm for dichloromethane.
The absorption spectra of the homoleptic compounds 2
and 5 in dichloromethane show a single maximum at
464 nm and 461 nm, respectively. The heteroleptic com-
pounds 3 and 4 show two maxima in the region between
400 and 500 nm (see Table 1), which can be assigned to the
two possible MLCT states of the two different ligands, cor-
responding to a transition from the d orbital of the ruthe-
nium centre to the π* orbital of tbbpy or dcmb. Absorption
spectra of the complexes [Ru(dcmb)3–n(tbbpy)n](PF6)2 with
n = 0–3 in dichloromethane are shown in Figure 8. The shift
in the absorption maxima in the case of the heteroleptic
compounds probably occurs as a result of a decrease in
symmetry and a cumulative effect of electron-withdrawing
and electron-donating properties.[11]
Figure 9. Emission spectra of the series of complexes [Ru(dcmb)n-
(tbbpy)3–n](PF6)2 with n = 0–3 in acetonitrile solution.
The lifetime measurements for the series of compounds
[Ru(dcmb)3–n(tbbpy)n](PF6)2 with n = 0–3 were performed
in aerated or deaerated acetonitrile and dichloromethane
(Table 1). For all the compounds, the values obtained are
higher in dichloromethane than in acetonitrile. The smallest
increase is observed for compound 2; in this case, the life-
time of the excited state in dichloromethane is only in-
creased by 50%. As expected, the lifetimes are also higher
in deaerated solvents than in aerated solvents. With increas-
ing numbers of dcmb ligands, the lifetimes increase too.
Interestingly, compound 2 presents the highest lifetime of
the four complexes, and the value exceeds 1 µs in deaerated
acetonitrile. The increase in lifetime for compound 5 on go-
ing from aerated to deaerated solvents renders this complex
a potential candidate for luminescent oxygen sensing.[19]
Resonance Raman Data of the Complexes
Figure 8. Absorption spectra of the series of complexes [Ru(dcmb)n-
(tbbpy)3–n](PF6)2 with n = 0–3 in dichloromethane solution.
To obtain further information on the location of the
The emission spectra of the complexes show a single 1MLCT excited state, compounds 2, 4 and 5 were investi-
maximum in the region between 600 and 700 nm (Figure 9). gated by resonance Raman spectroscopy. The location of
The order (in nm) of the emission maxima is 4 Ͼ 3 Ͼ 2 Ͼ the excited state is especially important in metal complexes
5, which corresponds to the order (in nm) of the absorption that serve as dyes in dye-sensitized solar cells. If the excited
maxima, as is expected for the photophysical deactivation state is not located on the TiO2-bound ligand, lower effi-
processes in such systems. The emission most likely occurs ciencies of charge injection are observed.[9] To the best of
3
exclusively from the lowest lying MLCT state.
our knowledge, the results presented here are the first reso-
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Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes
nance Raman spectroscopy experiments done on a com-
plete series of complexes with carboxylate functions.
All resonance Raman spectra were measured in dichloro-
methane. The nonresonant Raman spectra of the solids of
the homoleptic compounds 2 and 5 presented marker bands
that can be assigned to one specific ligand, i.e. tbbpy (5) or
dcmb (2). From the nonresonant Raman spectra, the peaks
at 1731, 1549, 1474 and 1445 cm–1 can be associated with
the dcmb ligand and the peaks at 1486 and 1422 cm–1 to the
tbbpy ligand. The peaks at 1617, 1320, 1028 and 1032 cm–1
cannot be assigned to one specific ligand because of over-
laps (see Table 2).
Table 2. Summary of the Raman bands of the free ligands tbbpy
and dcmb as well as of the complexes [Ru(tbbpy)3](PF6)2 (5),
[Ru(dcmb)(tbbpy)2](PF6)2 (4) and [Ru(dcmb)3](PF6)2 (2) in the
nonresonant Raman experiment; excitation wavelengths are given
in parentheses [nm] and wavenumbers in cm–1.
tbbpy (830.15) 5 (830.15) 4 (830.15) 2 (1064) dcmb (830.15)
1731
1617
1549
1732
1617
1553
1729
1604
1565
1609
1614
1552
1491
1537
1480
1486
1474
1445
1422
1320
1474
1447
1437
1427
1426
1321
1001
1417
1313
1027
1324
1324
997
Figure 10. Resonance Raman spectra of [Ru(tbbpy)3](PF6)2 (5),
[Ru(dcmb)(tbbpy)2](PF6)2 (4) and [Ru(dcmb)3](PF6)2 (2) dissolved
in dichloromethane. Peaks of the solvent are marked with an *;
the spectrum of 4 is normalised relative to the solvent band at
1425 cm–1.
1028+1032 1029
The excitation wavelength for the resonance Raman ex-
periments was 488 nm or 457 nm, which was obtained with
a continuous wave argon-ion laser. The excitation wave-
length for compound 5, 457 nm, is close to the absorption
maxima at 466 nm, and all enhanced peaks (1615, 1538,
1481, 1317 and 1031 cm–1) can be assigned to a d–π* transi-
tion from ruthenium to tbbpy as previously reported (see
Figure 10).[20] The excitation wavelength for compound 2
was also 457 nm and close to the absorption maxima at
461 nm, and all enhanced peaks (1737, 1619, 1553, 1477,
1448, 1323 and 1025 cm–1) can be assigned to a d–π* transi-
tion from ruthenium to dcmb.
In case of the heteroleptic complex 4 d–π*-transitions
to both ligands are possible as indicated by the absorption
spectra. The resonance enhancement depends on the loca-
tion of the MLCT process, which is activated with the exci-
tation wavelength. The transition to either a tbbpy or a
dcmb ligand or to both ligands simultaneously may occur.
For the absorption maxima at 492 nm, which is lowest in
energy, the excitation wavelength is 488 nm. This resonance
Raman spectrum shows a good agreement with the spec-
trum for 2, i.e. for the homoleptic dcmb compound.
ruthenium–tbbpy transition, arise in addition to the peaks
for the ruthenium–dcmb transition.
Nonetheless, on the basis of the resonance Raman data
obtained, we can assign the absorption maxima at 424 nm,
at least partially, to a MLCT transition from the ruthenium
centre to a tbbpy ligand, while the absorption at 492 nm
can exclusively be assigned to a MLCT transition to a dcmb
1
ligand. A “summarisation” of the MLCT processes that
occur in compounds 2, 4 and 5 is presented in Figure 11,
and these processes agree well with the electrochemical data
reported below.
For the second absorption maxima at 424 nm, we used
an excitation wavelength of 457 nm. Unfortunately, this
value is not very close to the absorption maxima, because
of restrictions of the laser wavelengths, and so still contains
some part of the long wavelength absorption. This is very
likely the reason why we can see an enhancement in both
MLCTs in the spectrum; in particular, a peak at 1484 cm–1
Figure 11. Schematic representation of the MLCT transitions of
and a shoulder at 1541 cm–1, which we can assign to the the different compounds 2, 4 and 5.
Eur. J. Inorg. Chem. 2008, 3310–3319
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S. Rau et al.
FULL PAPER
Electrochemistry
lying π* orbital that is populated first is a carboxy-substi-
tuted bipyridine. On fixation to a titanium dioxide surface,
the electron can be introduced from the ruthenium via the
carboxylated bipyridine into the conduction band of the
surface, which is the crucial step in the application as solar
cell devices. Hence, the direction of the photoelectron trans-
fer is predetermined by the choice of the connecting ligand.
The influence of the connection of the complexes to TiO2
will be part of following studies.
The oxidation and reduction potentials of all the com-
plexes in the series [Ru(dcmb)n(tbbpy)3–n](PF6)2 with n = 0–
3 and also the ∆E values for the potential difference be-
tween the first oxidation (Eox) and the first reduction (Ered1
)
process are given in Table 3. All electrochemical processes
appear to be quasireversible. In accordance to Schmehl et
al.,[11] these values are linearly related to the absorption
maxima. The electrochemical data show a decreasing order
of the ∆E value from 5 Ͼ 2 Ͼ 3 Ͼ 4, which corresponds to
the order of the absorption maxima and so supports a
linear relationship. The dcmb ligand, being a better π ac-
ceptor, shows two reduction processes. The data obtained
suggest that, in the case of mixed-ligand complexes, the first
ligand that is reduced is a dcmb ligand. Thereafter, a second
dcmb ligand or a tbbpy ligand is reduced. Only when every
other ligand is reduced can the dcmb ligand be reduced for
a second time.
Experimental Section
1H NMR and 13C NMR spectra were recorded at ambient tem-
perature with a Bruker AC 200 or AC 400 MHz spectrometer. All
spectra were referenced to TMS or deuterated solvent as an internal
standard. Mass spectra were recorded with a MAT 95 XL or a
SSQ 170, Finnigan Mat. The positive ES mass spectra were ob-
tained with voltages of 3–4 kV applied to the electrospray needle.
IR measurements were carried out with a Perkin–Elmer System
2000 FT-IR. UV/Vis absorption spectra (accuracy Ϯ2 nm) were ob-
tained with a Specord S 600 (AnalytikJena) with standard soft-
ware-based tools. Emission spectra (accuracy Ϯ5 nm) were mea-
sured at 298 K by using a Perkin–Elmer LS50B luminescence spec-
trophotometer equipped with a Hamamatsu R928 red-sensitive de-
tector. Emission spectra are uncorrected for photomultiplier re-
sponse. 10-mm path length quartz cells were used for recording
spectra. Luminescence lifetime measurements were obtained with
an Edinburgh Analytical Instruments (EAI) time-correlated single
photon counting apparatus (TCSPC) comprising two model J-yA
monochromators (emission and excitation), a single photon photo-
multiplier detection system model 5300 and a F900 nanosecond
flashlamp (nitrogen filled at 1.1 atm pressure, 40 kHz or 0.3 atm
pressure, 20 kHz) interfaced with a personal computer by a Nor-
landMCA card. A 410-nm cut-off filter was used in emission to
attenuate scatter of the excitation light (337 nm); luminescence was
monitored at the kmax of the emission. Data correlation and manip-
ulation was carried out with EAI F900 software version 6.24. Sam-
ples were deaerated by using argon for 30 min prior to measure-
ments, followed by repeated purging to ensure complete oxygen
Table 3. Oxidation and reduction potentials for the series of com-
plexes [Ru(dcmb)3–n(tbbpy)n](PF6)2 with n = 0–3 [potentials re-
corded in acetonitrile against ferrocene (0.47 V) as internal stan-
dard and tetrabutylammonium hexafluorophosphate as supporting
electrolyte]; ∆E = potential difference between first oxidation and
first reduction process.
Eox Ered1 Ered2 Ered3 Ered4 Ered5 Ered6 ∆E
Complex
[V]
0.73 –1.82 –2.02 –2.28
0.89 –1.40 –1.90 –2.12 –2.39
1.05 –1.32 –1.52 –1.99 –2.19 –2.48
[V]
[V]
[V]
[V]
[V]
[V]
[V]
5
4
3
2
2.55
2.29
2.37
1.18 –1.28 –1.44 –1.65 –2.10 –2.26 –2.54 2.46
Conclusions
In conclusion, we have shown that heteroleptic ruthe-
nium complexes are easily accessible starting from
[RuCl2(dcmb)2] and [RuCl2(tbbpy)2]. Both starting com- exclusion. Emission lifetimes were calculated by using a single-ex-
ponential fitting function, Levenberg–Marquardt algorithm with
iterative deconvolution (Edinburgh Instruments F900 software).
The reduced ν2, and residual plots were used to judge the quality
of the fits. Lifetimes are Ϯ5%. The resonance Raman spectra were
obtained by using a continuous-wave argon-ion laser from Spectra
Physics as the excitation source and a CCD-camera Photometrics
M9000 as the detector. The electrochemical measurements were ex-
ecuted with a PGSTAT booth (manufacturer: Autolab) with the
aid of the appropriate GPES software. The experiments were car-
ried out by means of a three-electrode technique in degassed aceto-
pounds can be prepared in high yields and in short reaction
times by using microwave-assisted reaction conditions. The
introduction of another bipyridine ligand leads to the func-
tional building blocks; this second step proceeds with rea-
sonable yields. Characteristic for both steps, are the short
reaction times of less than 2 h and the high purities of the
obtained complexes. The solid-state structures of all com-
pounds are similar and show distorted octahedrally coordi-
nated ruthenium centres. In the series of complexes investi-
gated, no correlation between the solid-state structures and nitrile with tetrabutylammoniumtetrafluoroborate (0.1 –1) as the
conducting salt. An Hg-dropping electrode or a rotating-disc plati-
num electrode was used as the working electrode. The reference
electrode was an Ag/AgCl electrode. The calibration of the elec-
trode took place according to the ferrocene standard potential in
acetonitrile for which a value of +0.827 V was assumed. The micro-
wave-assisted reactions were carried out with a Microwave Labora-
tory System MLS EM-2 microwave system. RuCl3·xH2O, NH4PF6,
4,4Ј-dimethyl-2,2Ј-bipyridine and all solvents were of commercial
grade and used without further purification. [RuCl2(cod)]n,[21] 4,4Ј-
ditertbutyl-2,2Ј-bipyridine (tbbpy)[22] and [RuCl2(tbbpy)2] were pre-
the photophysical properties of the complexes is obtained.
Absorption and emission maxima follow the order 4 Ͼ 3 Ͼ
2 Ͼ 5 and show highest extinction coefficients in dichloro-
methane. The same order can be found for the electrochemi-
cally measured ∆E values. The resonance Raman data show
that the lowest-energy absorption maximum can be as-
signed to a MLCT transition from the ruthenium centre to
a dcmb ligand, and thus verifies experimentally the hypoth-
esis of Schmehl. This fact is important because it means
that upon excitation of a ruthenium compound, the lowest pared as described in the literature.
3316 Eur. J. Inorg. Chem. 2008, 3310–3319
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes
4,4Ј-Dicarboxy-2,2Ј-bipyridine (dcbpy): The ligand was prepared by
using a variation of the known synthesis.[13] 4,4Ј-Dimethyl-2,2Ј-bi-
pyridine (2.7 g, 15 mmol) was dissolved in concentrated sulfuric
acid (70 mL). At 0 °C potassium dichromate (17.6 g, 60 mmol) was
added in small portions. After that the reaction mixture was heated
to 50 °C for 1 h. The green solution was poured into ice water
(300 mL); the resulting precipitate was collected on a filter and
washed with water until the filtrate became colourless. The pale
green–yellow solid was refluxed in nitric acid (70 mL; 50% aq.) for
4 h, poured into 300 mL ice, filtered and washed with water and
acetone. The resulting white solid was dried in vacuo. Yield: 3.16 g
(86%). C12H8N2O4 (244.2): calcd. C 59.02, H 3.30, N 11.47; found
(30 mL/20 mL) was heated at reflux overnight. Methanol was re-
moved with the rotary evaporator; the obtained solution was fil-
tered, and an aqueous solution of NH4PF6 was added. The red-
brown solid obtained was collected, washed with ethanol and di-
ethyl ether and dried in air. Yield: 0.10 g (55%). C46H48F12N6O8-
P2Ru (1203.89): calcd. C 45.89, H 4.02, N 6.98; found C 45.77, H
4.07, N 6.75. IR (KBr): ν(C=O) = 1732 (s) cm–1. UV (CH CN):
˜
3
λmax = 486 nm. MS (ES in methanol): m/z (%) = 457 (20) [(M –
1
2PF6)/2]2+, 913 (10) [M – 2PF6 – H]+, 1059 (100) [M – PF6]+. H
NMR (400 MHz, CD2Cl2, 300 K): δ = 8.99 (d, J = 1.6 Hz, 2 H),
8.98 (d, J = 1.6 Hz, 2 H), 8.28 (d, J = 2.0 Hz, 2 H), 8.02 (dd, J =
1.6, 6.0 Hz, 2 H), 7.96 (d, J = 6.0 Hz, 4 H), 7.91 (d, J = 6.0 Hz, 2
H), 7.53 (d, J = 6.0 Hz, 2 H), 7.48 (dd, J = 2.0, 6.0 Hz, 2 H), 4.03
(s, 6 H), 4.04 (s, 6 H), 1.41 (s, 18 H) ppm. 13C{1H} NMR (50 MHz,
CD2Cl2, 300 K): δ = 30.3, 36.0, 53.7, 121.4, 123.9, 126.6, 127.9,
139.6, 151.2, 153.1, 156.2, 157.2, 157.5, 163.8, 163.9, 164.3 ppm.
Crystals suitable for X-ray diffraction were obtained from a solu-
tion of acetonitrile/water/methanol.
C 58.72, H 3.25, N 11.43. IR (KBr): ν(C=O) = 1721 (s) cm–1. MS
˜
1
(EI): m/z (%) = 244 (40) [M]+, 200 (100) [M – CO2]+, 172, 155. H
NMR (200 MHz, D2O/Na, 300 K): δ = 8.56 (dd, J = 0.8, 5.0 Hz,
2 H), 8.17 (dd, J = 0.8, 1.6 Hz, 2 H), 7.65 (dd, J = 1.6, 5.0 Hz, 2
H) ppm.
4,4Ј-Dimethoxycarbonyl-2,2Ј-bipyridine (dcmb): The ligand was pre-
pared as described in the literature.[23] C14H12N2O4 (272.25). IR
[Ru(dcmb)(tbbpy)2](PF6)2 (4): A suspension of [RuCl2(tbbpy)2]
(KBr): ν(C=O) = 1732 (s) cm–1. MS (EI): m/z (%) = 272 (20) (0.142 g, 0.2 mmol) and dcmb (0.054 g, 0.2 mmol) in methanol/
˜
[M]+, 241 (10) [M – CH3O]+, 214 (100) [M – CH3OCO]+. 1H NMR
(200 MHz, CDCl3, 300 K): δ = 8.94 (dd, J = 0.8, 1.6 Hz, 2 H), 8.84
(dd, J = 0.8, 5.0 Hz, 2 H), 7.87 (dd, J = 1.6, 5.0 Hz, 2 H), 3.96 (s,
6 H) ppm.
water (60 mL/20 mL) was heated at reflux overnight. Methanol was
removed with the rotary evaporator; the obtained solution was fil-
tered, and an aqueous solution of NH4PF6 was added. The red-
brown solid obtained was collected, washed with ethanol and
diethyl ether and dried in air. Yield: 0.18 g (75%).
C50H60F12N6O4P2Ru·0.5H2O (1209.04) calcd: C 49.67, H 5.09, N
[RuCl2(dcmb)2] (1): The complex was prepared in an analogous
fashion to [RuCl2(tbbpy)2].[10] A suspension of [RuCl2(cod)]n
(0.56 g, 2.0 mmol) and dcmb (1.09 g, 4.0 mmol) in DMF (150 mL)
were treated for 1 h under microwave irradiation (microwave setup:
30 s, 600 W; 60 min, 200 W; 10 min, ventilation). The solvent was
immediately removed with the rotary evaporator. The obtained
dark green solid was recrystallised with chloroform/diethyl ether
and dried in air. Yield: 1.29 g (90%). C28H24Cl2N4O8Ru·H2O
(734.49): calcd. C 45.78, H 3.57, N 7.63; found C 45.81, H 3.48, N
6.95; found C 49.88, H 5.20, N 6.88. IR (KBr): ν(C=O) = 1732
˜
(s) cm–1. UV (CH3CN): λmax = 492 nm. MS (ES in methanol): m/z
(%) = 455 (10) [(M – 2PF6)/2]2+, 909 (10) [M – 2PF6 – H]+, 1055
1
(100) [M – PF6]+. H NMR (400 MHz, CD3CN, 300 K): δ = 9.02
(d, J = 1.6 Hz, 2 H), 8.48 (d, J = 2.0 Hz, 2 H), 8.46 (d, J = 1.6 Hz,
2 H), 7.90 (d, J = 6.0 Hz, 2 H), 7.82 (dd, J = 1.6, 6.0 Hz, 2 H),
7.53 (d, J = 6.0 Hz, 2 H), 7.50 (d, J = 6.0 Hz, 2 H), 7.42 (dd, J =
2.0, 6.0 Hz, 2 H), 7.34 (dd, J = 1.6, 6.0 Hz, 2 H), 3.99 (s, 6 H), 1.41
(s, 18 H), 1.39 (s, 18 H) ppm. 13C{1H} NMR (100 MHz, CD3CN,
300 K): δ = 30.5, 36.4, 54.0, 122.7, 124.6, 125.7, 125.8, 127.4, 139.1,
151.7, 152.1, 153.6, 157.5, 157.6, 158.9, 164.2, 165.0 ppm. Crystals
suitable for X-ray diffraction were obtained from a solution of ace-
tone/water.
7.69. IR (KBr): ν(C=O) = 1725 (s) cm–1. UV (methanol): λ
=
˜
max
555 nm. MS (ES in methanol): m/z (%) = 681 (20) [M – Cl]+, 739
(100) [M + Na]+, 1457 (40) [2M + Na]+. 1H NMR (400 MHz,
CD2Cl2, 300 K): δ = 10.33 (dd, J = 0.4, 6.0 Hz, 2 H), 8.89 (dd, J
= 0.4, 1.6 Hz, 2 H), 8.72 (dd, J = 0.4, 1.6 Hz, 2 H), 8.19 (dd, J =
1.6, 6.0 Hz, 2 H), 7.72 (dd, J = 0.4, 6.0 Hz, 2 H), 7.49 (dd, J =
1.6, 6.0 Hz, 2 H), 4.07 (s, 6 H), 3.93 (s, 6 H) ppm. 13C{1H} NMR [Ru(tbbpy)3](PF6)2 (5): The complex was prepared as described in
(100 MHz, CD2Cl2, 300 K): δ = 53.1, 53.3, 122.1, 122.3, 124.7,
125.3, 135.2, 136.4, 153.1, 155.2, 158.6, 160.8, 164.5, 165.0 ppm.
Crystals suitable for X-ray diffraction were obtained from a solu-
tion of acetonitrile/toluene.
the literature.[10] C54H72F12N6P2Ru (1196.17): calcd. C 54.22, H
6.07, N 7.03; found C 54.37, H 6.25, N 7.05. UV (CH3CN): λmax
= 458 nm. MS (ESI in methanol): m/z (%) = 438 (10) [(M – 2CH3 –
1
2PF6)/2]2+, 906 (10) [M – 2PF6 – H]+, 1051 (100) [M – PF6]+. H
NMR (200 MHz, CD3CN, 300 K): δ = 8.52 (d, J = 2.0 Hz, 6 H),
7.54 (d, J = 6.0 Hz, 6 H), 7.38 (dd, J = 2.0, 6.0 Hz, 6 H), 1.94 (s,
18 H) ppm. 13C{1H} NMR (50 MHz, CD3CN, 300 K): δ = 30.5,
36.3, 122.4, 125.6, 151.7, 157.9, 163.4 ppm. Crystals suitable for X-
ray diffraction were obtained from a solution of acetone/water.
[Ru(dcmb)3](PF6)2 (2): A suspension of 1 (0.190 g, 0.265 mmol) and
dcmb (0.072 g, 0.265 mmol) in methanol/water (40 mL/20 mL) was
heated at reflux overnight. Methanol was removed with the rotary
evaporator; the obtained solution was filtered, and an aqueous
solution of NH4PF6 was added. The red-brown solid obtained was
collected, washed with ethanol and diethyl ether and dried in air.
Yield: 0.19 g (60%). C42H36F12N6O12P2Ru·H2O (1225.76) calcd: C
41.15, H 3.12, N 6.86; found C 41.39, H 3.23, N 6.79. IR (KBr):
[Ru(dcbpy)3]Na4: A suspension of 2 (0.06 g, 0.05 mmol) with so-
dium hydroxide (0.014 g, 0.35 mmol) in water (20 mL) was heated
at reflux overnight. The red solution was reduced in volume with
ν(C=O) = 1732 (s) cm–1. UV (CH CN): λmax = 467 nm. MS (ES in the rotary evaporator; an orange precipitate was obtained on ad-
˜
3
methanol): m/z (%) = 459 (90) [(M – 2PF6)/2]2+, 917 (50) [M – dition of ethanol. The solid was collected, washed with ethanol and
2PF6 – H]+, 1063 (100) [M – PF6]+. H NMR (400 MHz, CD3CN, diethyl ether and dried in air. The results obtained from the analysis
1
300 K): δ = 9.05 (d, J = 1.6 Hz, 6 H), 7.86 (d, J = 6.0 Hz, 6 H), of the compound agrees well with literature values.[24] Yield: 0.03 g
7.82 (dd, J = 1.6, 6.0 Hz, 6 H), 3.98 (s, 18 H) ppm. 13C{1H} NMR
(100 MHz, CD3CN, 300 K): δ = 54.1, 125.1, 127.8, 140.5, 154.1,
(65%). IR (KBr): ν(C=O) = 1607 (s) cm–1. 1H NMR (200 MHz,
˜
D2O, 300 K): δ = 8.76 (d, J = 1.6 Hz, 6 H), 7.75 (d, J = 5.8 Hz, 6
158.3, 164.8 ppm. Crystals suitable for X-ray diffraction were ob- H), 7.56 (dd, J = 1.6, 5.8 Hz, 6 H) ppm.
tained from a solution of acetone/water.
Crystal Structure Determination: The intensity data for the com-
pounds were collected with a Nonius KappaCCD diffractometer,
0.152 mmol) and tbbpy (0.41 g, 0.152 mmol) in methanol/water by using graphite-monochromated Mo-Kα radiation. For com-
[Ru(dcmb)2(tbbpy)](PF6)2 (3):
A
suspension of
1
(0.109 g,
Eur. J. Inorg. Chem. 2008, 3310–3319
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3317

S. Rau et al.
FULL PAPER
pound 1, measurements were carried out at beamline ID11 at the
European Synchrotron Radiation Facility (ESRF). Data were col-
lected with a Bruker Smart CCD-camera system at fixed 2θ, while
the sample was rotated over 0.1° intervals over 2 s exposures, by
Crystal Data for 5: C57H78F12N6OP2Ru, Mr = 1254.26 gmol–1,
brown prism, size 0.38ϫ0.32ϫ0.30 mm, monoclinic, space group
C2/c, a = 20.7485(7), b = 26.0046(7), c = 11.4949(4) Å, β =
103.392(2)°, V = 6033.5(3) Å3, T = –90 °C, Z = 4, ρcalcd.
=
using monochromated radiation from λ = 0.46409 Å. Data were 1.381 gcm–3, µ (Mo-Kα) = 3.93 cm–1, F(000) = 2608, 8098 reflec-
corrected for Lorentz and polarisation effects, but not for absorp- tions in h(–23/22), k(–28/28), l(0/12), measured in the range 3.27°
tion.[25–27] The structures were solved by direct methods
(SHELXS[28]) and refined by full-matrix least-squares techniques
against Fo2 (SHELXL-97[29]). The hydrogen atoms of the structures
were included at calculated positions with fixed thermal param-
eters. All non-hydrogen atoms were refined anisotropically.[29] The
quality of the data for compound 1 was poor. Therefore, we will
only publish the conformation of the molecule and the crystallo-
graphic data. We will not deposit the data in the Cambridge Crys-
tallographic Data Centre. XP (Siemens Analytical X-ray Instru-
ments, Inc.) was used for structure representations. CCSD-614182
(2), -614183 (3), -614184 (4), and -614185 (5) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Յ Θ Յ 23.30°, completeness Θmax = 94.8%, 4129 independent re-
flections, Rint = 0.054, 3564 reflections with Fo Ͼ 4σ(Fo), 368 pa-
rameters, 0 restraints, R1obs = 0.0465, wR2obs = 0.1257, R1all
=
0.0572, wR2all = 0.1332, GOOF = 1.017, largest difference peak
and hole: 0.734/–0.886 eÅ–3.
Acknowledgments
We thank the Scholarship program of the Studienstiftung des Deut-
schen Volkes, the Deutsche Forschungsgemeinschaft, the Founda-
tion for the technology, innovation and research in Thuringia
(STIFT) for support of this research.
Crystal Data for 1: C28H24Cl2N4O8Ru, Mr = 716.48 gmol–1, green-
brown prism, size 0.04ϫ0.04ϫ0.03 mm, triclinic, space group P1,
¯
[1] V. Balzani, P. Piotrowiak, M. A. J. Rodgers, J. Mattay, D. As-
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a = 13.4390(7), b = 13.6738(8), c = 15.8298(11) Å, α = 90.069(3),
β = 90.022(3), γ = 89.995(3)°, V = 2908.9(3) Å3, T = –90 °C, Z =
4, ρcalcd. = 1.636 gcm–3, µ (λ = 0.46409 Å) = 4.15 cm–1, F(000) =
1448, 25645 reflections in h(–18/18), k(–18/18), l(–21/21), measured
in the range 1.68° Յ Θ Յ 18.80°, completeness Θmax = 84.6%,
13793 independent reflections.
Crystal Data for 2: C42H36F12N6O12P2Ru·0.5C3H6O, Mr
=
[3] a) X. Marguerettaz, D. Fitzmaurice, J. Am. Chem. Soc. 1994,
116, 5017–5018; b) K. Kalyanasundaram, M. Gratzel, Coord.
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[4] a) V. Balzani, F. Scandola in Supramolecular Photochemistry,
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atne, T. Gunnlaugsson, A. J. M. Huxley, C. P. McCoy, J. T. Ra-
demacher, T. E. Rice, Chem. Rev. 1997, 97, 1515–1566.
[5] a) R. Konduri, H. Ye, F. M. MacDonnell, S. Serroni, S. Cam-
pagna, K. Rajeshwar, Angew. Chem. 2002, 41, 3185–3187; b)
M. Kaneko, N. Katakura, C. Harada, Y. Takei, M. Hoshino,
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M. Hara, N. Saito, Y. Inoue, H. Kobayashi, K. Domen, J. Am.
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[6] S. L. Gilat, S. H. Kawai, J.-M. Lehn, J. Chem. Soc., Chem.
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1236.82 gmol–1, red-brown prism, size 0.05ϫ0.05ϫ0.04 mm, tri-
¯
clinic, space group P1, a = 10.3660(4), b = 13.0534(5), c =
19.4694(9) Å, α = 94.930(2), β = 97.402(2), γ = 92.085(2)°, V =
2599.81(19) Å3, T = –90 °C, Z = 2, ρcalcd. = 1.580 gcm–3, µ (Mo-
Kα) = 4.71 cm–1, F(000) = 1248, 18434 reflections in h(–13/13),
k(–16/16), l(–25/23), measured in the range 1.81° Յ Θ Յ 27.49°,
completeness Θmax = 98.4%, 11739 independent reflections, Rint
0.049, 8444 reflections with Fo Ͼ 4σ(Fo), 672 parameters, 0 re-
straints, R1obs = 0.1249, wR2obs = 0.3510, R1all = 0.1617, wR2all
=
=
0.3763, GOOF = 1.428, largest difference peak and hole: 4.245/
–2.058 eÅ–3.
Crystal Data for 3: C46H48F12N6O8P2Ru·1.5H2O·0.5CH3CN, Mr =
1251.46 gmol–1, red-brown prism, size 0.06ϫ0.06ϫ0.04 mm, mo-
noclinic, space group P21/n, a = 9.9092(2), b = 33.0889(7), c =
16.8815(4) Å, β = 98.440(1)°, V = 5475.2(2) Å3, T = –90 °C, Z =
4, ρcalcd. = 1.518 gcm–3, µ (Mo-Kα) = 4.45 cm–1, F(000) = 2552,
32367 reflections in h(–12/9), k(–42/42), l(–21/21), measured in the
range 2.17° Յ Θ Յ 27.48°, completeness Θmax = 97.3%, 12192
independent reflections, Rint = 0.083, 6869 reflections with Fo
4σ(Fo), 710 parameters, 0 restraints, R1obs = 0.0743, wR2obs
Ͼ
=
0.1767, R1all = 0.1515, wR2all = 0.2124, GOOF = 1.018, largest
difference peak and hole: 1.605/–0.492 eÅ–3.
Crystal Data for 4: C50H60F12N6O4P2Ru, Mr = 1200.05 gmol–1,
red-brown prism, size 0.04ϫ0.04ϫ0.03 mm, monoclinic, space
group P21/n, a = 18.6766(9), b = 16.0388(9), c = 19.9485(9) Å, β =
114.637(3)°, V = 5431.6(5) Å3, T = –90 °C, Z = 4, ρcalcd.
=
1.468 gcm–3, µ (Mo-Kα) = 4.37 cm–1, F(000) = 2464, 35699 reflec-
tions in h(–19/24), k(–20/20), l(–25/25), measured in the range 1.70°
Յ Θ Յ 27.44°, completeness Θmax = 99.3%, 12307 independent
reflections, Rint = 0.050, 7837 reflections with Fo Ͼ 4σ(Fo), 655
parameters, 0 restraints, R1obs = 0.0878, wR2obs = 0.2367, R1all
=
0.1367, wR2all = 0.2773, GOOF = 1.038, largest difference peak
and hole: 1.318/–1.112 eÅ–3.
3318
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 3310–3319

Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes
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Received: December 3, 2007
Published Online: June 13, 2008
Eur. J. Inorg. Chem. 2008, 3310–3319
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3319