The effects of pendant vs. fused thiophene attachment upon the luminescence lifetimes and electrochemistry of tris(2,2′-bipyridine)ruthenium(II) complexes

Article abstract of DOI:10.1002/ejic.200800456

The electrochemical and photophysical properties for a range of tris(2,2′-bipyridine)ruthenium(II) complexes in which a thiophene substituent is attached to one of the bipyridine ligands by either a pendant or a fused mode have been determined. The fused mode of attachment eliminates torsional movement between the thiophene unit and the chelating bipyridine, thereby offering optimal overlap between the ?-systems of the chelating unit and the attached thiophene unit. The electrochemical properties of these complexes were found to be similar; however, the luminescence lifetimes and intensities (in CH₃CN at room temperature) were found to be correlated to the mode of attachment. The longest luminescence lifetime was observed for the complex [Ru(bpy)₂{4-(thiophen-2-yl)-2,2′-bipyridine}] ²⁺ (3000 ns), as compared to the prototypic [Ru(bpy) ₃]²⁺ (1745 ns). This complex also had the highest quantum yield (0.045). In the four isomeric complexes, where the thiophene ring was fused to the b or c face of the pyridine ring, the lifetimes fell in the interval 275-1510 ns, and the quantum yield ranged between 0.0047 and 0.014. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800456

FULL PAPER
DOI: 10.1002/ejic.200800456
The Effects of Pendant vs. Fused Thiophene Attachment
upon the Luminescence Lifetimes and Electrochemistry of
Tris(2,2Ј-bipyridine)ruthenium(II) Complexes
Lasse J. Nurkkala,[a] Robert O. Steen,[a] Henrik K. J. Friberg,[a] Johanna A. Häggström,[a]
Paul V. Bernhardt,[b] Mark J. Riley,[b] and Simon J. Dunne*[a]
Keywords: Luminescence / N ligands / Ruthenium / Ligand design / Cyclic voltammetry
The electrochemical and photophysical properties for a
range of tris(2,2Ј-bipyridine)ruthenium(II) complexes in
which a thiophene substituent is attached to one of the bipyr-
idine ligands by either a pendant or a fused mode have been
determined. The fused mode of attachment eliminates tor-
sional movement between the thiophene unit and the chelat-
ing bipyridine, thereby offering optimal overlap between the
π-systems of the chelating unit and the attached thiophene
unit. The electrochemical properties of these complexes were
found to be similar; however, the luminescence lifetimes and
intensities (in CH3CN at room temperature) were found to
be correlated to the mode of attachment. The longest lumi-
nescence lifetime was observed for the complex [Ru(bpy)2{4-
(thiophen-2-yl)-2,2Ј-bipyridine}]2+ (3000 ns), as compared to
the prototypic [Ru(bpy)3]2+ (1745 ns). This complex also had
the highest quantum yield (0.045). In the four isomeric com-
plexes, where the thiophene ring was fused to the b or c face
of the pyridine ring, the lifetimes fell in the interval 275–
1510 ns, and the quantum yield ranged between 0.0047 and
0.014.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
have chosen to use the well-studied [Ru(bpy)3]2+ as an elec-
tron source due to the efficiency and stability of its excited
state.[3] Upon photoexcitation, by a metal-to-ligand charge-
transfer (MLCT) process, the complex undergoes red lumi-
nescence from the MLCT triplet state. The lifetime of this
state can then be used to reflect the ability of the complex
to act as an energy or electron source/sink.
Introduction
While still in its infancy, molecular electronics is quickly
expanding to be one of the hottest areas of chemical re-
search. Part of the allure of this area is that no one ap-
proach dominates the field, and prototypic systems have
been established from a wide range of chemical structures.
The conductivity of organic molecules such as oligoacetyl-
enes, oligophenylenes and oligothiophenes (as molecular
wires, the simplest functional units of a molecular circuit)
has been found to be dependant upon the length of the
conjugation path, together with their ability to establish a
fully planar completely delocalised π-system.[1] Such oligo-
mers are rigid and beyond a certain length, the handling
properties of these oligomers become problematic due to
their poor solubility. In this regard, oligothiophenes offer
some advantages due to their fully planar structures, ease
of synthesis and substitution, and their stability to oxi-
dation.[2] However, a molecular wire is not an active com-
ponent in a molecular circuit, and thus it must be connected
to an energy or electron source/sink to fulfill its role. We
3
The coupling between an energy/electron source and its
conducting unit is of great importance.[4] In our previous
study[5] we examined the isomeric effects within the covalent
coupling of oligothiophene units and 2,2Ј-bipyridine chelat-
ing units upon the electrochemical and photophysical prop-
erties of their [Ru(bpy)2L]2+ complexes. It was found that
coupling of the oligothiophene in the 6-position of the 2,2Ј-
bipyridine unit led to quenching of all long-lived red lumi-
nescence This is due to the energy of the metal-centred
d–d transition being lowered for 6-substituted bipyridines,
leading to competitive radiationless relaxation and quench-
ing of the luminescence. Coupling through the 4-position
produced lifetimes longer than that of the prototype
[Ru(bpy)3]2+, but when this motif was used as the chelating
unit in bridged dimetallic compounds, only weak electronic
coupling was observed, perhaps due to lack of coplanarity
between the bipyridine and the bridgehead, resulting from
interannular interaction. This led us to investigate a new
coupling mode where the first member of the oligothi-
ophene was fused to one of the b or c faces of the chelating
unit, thereby ensuring absolute planarity between these sub-
units. In this work we present a comparison of the electro-
[a] Department of Biology and Chemical Engineering, Mälardalen
University,
Gamla Tullgatan 2, 63105 Eskilstuna, Sweden
Fax: 46-16-153710
E-mail: simon.dunne@mdh.se
[b] Department of Chemistry, School of Molecular & Microbial
Sciences, University of Queensland,
Brisbane 4072, Qld, Australia
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2008, 4101–4110
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S. J. Dunne et al.
FULL PAPER
chemical and photophysical properties of the four [Ru-
(bpy)2L]2+ complexes formed from this new class of connec-
tors, with those of the [Ru(bpy)3]2+, [Ru(bpy)2L1]2+ and
[Ru(bpy)2L2]2+, where L1 is 6-(thiophen-2-yl)-2,2Ј-bipyr-
idine and L2 is 4-(thiophen-2-yl)-2,2Ј-bipyridine in order to
establish an optimal connecting mode for these components
in molecular electronic applications.
Scheme 1. The condensation reaction leading to the formation of
the chalcone precursors P2–P9 (X = H, thiophen-2-yl, 5-methyl-
thiophen-2-yl;
Y = thiophen-2-yl, 4-tert-butylphenyl, 4-meth-
oxyphenyl, 4-nitrophenyl).
These chalcones were then treated with the Kröhnke rea-
gent 2-[1-oxo-2-(1-pyridinio)ethyl]pyridine iodide[6] and an
excess of ammonium acetate (Scheme 2) to yield the pure
products after column chromatography/Soxhlet extraction,
and recrystallization.
Results and Discussion
Synthesis
The complexes C1–C13 were prepared from their respec-
tive ligands L1–L13 (see Figures 1 and 2) by treating the
ligands with cis-[Ru(bpy)2Cl2] in ethylene glycol. Addition
of ammonium hexafluorophosphate to the cooled reaction
mixture resulted in precipitation of the complexes.
Scheme 2. Generation of the 2,4,6-trisubstituted pyridines by using
the Kröhnke methodology [X = H (L2), thiophen-2-yl (L3–L5), 5-
methylthiophen-2-yl (L6–L9); Y = thiophen-2-yl (L2, L9), 4-tert-
butylphenyl (L3, L6), 4-methoxyphenyl (L4, L7), 4-nitrophenyl
(L5, L8)].
The fused pyridyl-thienopyridines L10, L11 and L12
were synthesized by using our recently reported methods,[8]
which are presented in schematic form in the Supporting
Information (Schemes S1, S2 and S3, respectively).
The preparation of ligand L13 began with an attempt to
perform a Heck reaction on 3-bromothiophene-2-carbal-
dehyde (Scheme 3), but the reaction failed. Protection of
the formyl group as a cyclic acetal[9] (a functional group
tolerated in the Heck reaction) resulted in subsequent for-
mation of 2-{2-[2-(1,3-dioxolan-2-yl)thiophen-3-yl]vinyl}-
pyridine (14) in 94% yield. Steric effects could thereby be
Figure 1. The thiophenyl-bipyridine ligands L1–L9 used in this
study.
Figure 2. The fused thienopyridine ligands L10–L13 used in this
study.
The ligands L1–L9 were prepared in moderate yields by
adaptations of methods described earlier by Kröhnke[6] and
Constable.[7] The propenone precursors (chalcones) P2–P9
were generated by aldol condensation of the corresponding
aromatic methyl ketone with an aromatic aldehyde
(Scheme 1).
Scheme 3. Synthetic route to 5-(pyridin-2-yl)thieno[2,3-c]pyridine
(L13).
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Luminescence Lifetimes and Electrochemistry of Tris(2,2Ј-bipyridine)ruthenium(II) Complexes
discounted as the reason for the failure of the Heck reaction
in the earlier attempt, suggesting rather participation of for-
myl π-orbitals in the catalytic complex. Deprotection gave
3-[2-(pyridin-2-yl)vinyl]thiophene-2-carbaldehyde (15) in
87% yield, which could be quantitatively converted into the
oxime 16 prior to the thermal ring-closure. The pyridyl-thi-
enopyridine L13 was then obtained in moderate yield by
cyclization in Decalin® (35%).[10]
Electrochemistry
The redox potentials of the Ru complexes determined by
cyclic voltammetry in CH3CN with 0.1  Et4NClO4 as sup-
porting electrolyte (reported in mV vs. the ferrocene/ferro-
cenium couple) are listed in Table 1. Three of these are
shown in Figure 3 as representative of the compounds in
this series. All voltammograms are collected in Figure S1
(Supporting Information), and were measured at a sweep
rate of 200 mVs–1. (Polypyridine)RuII complexes exhibit
rich and complex electrochemistry in non-aqueous solu-
tions comprising both metal-centred oxidation (RuIII/II) and
Figure 3.Voltammograms of the complexes C6, C7 and C8. The
bpy-centred reduction reactions. The RuIII/II couples are all
totally reversible and appear in a narrow range (Table 1).
The substitution of a thiophene ring into either the 4- or
the 6-position of the 2,2Ј-bipyridine system appears to have
concentration was 1 m in CH3CN, ν = 200 mVs–1 and all other
conditions are given in the Experimental Section.
only a minor effect upon the value for the RuIII/II couple, stituent is abated by the inability of the phenyl ring to fully
with most complexes possessing values similar to that of adopt a coplanar conformation with the central pyridine
the parent complex [Ru(bpy)3]2+
.
ring. The introduction of these Y-substituents directly onto
As the redox potentials displayed by the prototypes C1 one of the chelating rings to amplify their effect is currently
and C2 fell within a narrow range, it was of interest to ex- under investigation.
amine the effect on the RuIII/II couple of a 4-Y-phenyl sub-
The nitro group in C5 and C8 had a profound effect on
stituent upon the unique 2,2Ј-bipyridine ring system. For the ligand-centred reduction potentials. The nitro group
ease of synthesis, analogues of L1 were chosen and the itself is electroactive and the distinctly different voltamme-
Kröhnke methodology[6] applied, leading to the ligands L3– try displayed by these complexes (see Figure 3) is indicative
L9 in moderate yields. The corresponding RuIII/II couples of a reaction where reduction of the nitro-substituted bpy
for C3–C9 were indeed found to reflect the electron-with- is facilitated by delocalisation over the nitro group. Interest-
drawing/donating character of the Y substituent, but the ingly, the second and third bpy reduction potentials are an-
shifts were small in all cases (1–33 mV). It is most likely odically shifted by a similar degree (Figure 3) indicating
that the transfer of electron density to and from the Y-sub- that electron delocalisation across the metal atom and the
Table 1. Redox potentials (mV vs. Fc+/0). Experimental conditions: 1 m complex in CH3CN with 0.1  Et4NClO4 as supporting
electrolyte, T = 298 K, glassy carbon working electrode (3 mm), Pt auxiliary electrode and Ag/Ag+ (MeCN) reference electrode,
ν = 200 mV s–1.
[Ru(bpy)2Ln]2+
[Ru(bpy)2Ln]3+/2+
[Ru(bpy)2Ln]2+/+
[Ru(bpy)2Ln]+/0
[Ru(bpy)2Ln]0/–
[Ru(bpy)3]2+[a]
+874
+869
+850
+854
+846
+878
+846
+836
+870
+845
+892
+924
+829
+849
–1728
–1706
–1694
–1690
–1705
–1295
–1688
–1706
–1295
–1653
–1676
–1641
–1755
–1758
–1912
–1915
–1896
–1899
–1907
–1514
–1896
–1908
–1513
–1889
–1882
–1874
–1942
–1948
–2162
–2227
–2139
–2215
–2219
–1890
–2214
–2216
–1861
–2208
–2132
–2136
–2152
–2214
1
2
3
4
5
6
7
8
9
10
11
12
13
[a] [Ru(bpy)3]2+ data collected during this study.
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S. J. Dunne et al.
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three ligands influences all subsequent reductions. The pres- Luminescence Properties
ence of the 5-methylthiophen-2-yl substituent in C6–C9
As observed in our previous study,[5] the red [Ru-
(bpy)3]2+-type MLCT luminescence was quenched in those
cases where a thiophenyl substituent was present in the 6-
position of the unique 2,2Ј-bipyridine, the only exception
being the prototype C1 and C3 where a very weak red lumi-
nescence was observed (see Table 2). Whereas, when the
thiophene is attached to the 4-position (C2), a red lumines-
cence and an excitation spectrum very similar to that of
[Ru(bpy)3]2+ (Figure 4) are observed, although with a
slightly greater quantum yield and longer lifetime (3000 ns)
when compared to that of [Ru(bpy)3]2+ (1745 ns) obtained
under identical conditions.
shifted the metal-centred oxidation to lower potentials,
whereas the effects upon the ligand reductions were mar-
ginal.
The results for the fused pyridyl-thienopyridine com-
plexes C10–C13 were interesting and revealed some signifi-
cant isomeric effects. The complexes in which the thiophene
ring was fused to the b face of the bipyridine (C10, C11)
exhibited higher RuIII/II potentials than [Ru(bpy)3]2+
,
whereas those in which the thiophene was attached to the c
face (C12, C13) were lower by a similar degree. The orienta-
tion of the fused thiophene ring (with the S-atom syn or
anti relative to the adjacent N-donor) has an additional in-
fluence on the RuIII/II redox potential. In this case it seems
that the proximity of the electronegative S-atom to the Ru
ion is responsible for this effect. In compounds C11 and
C13 the RuIII/II redox potential is ca. 20–30 mV higher than
in C10 and C12. The thiophene S-atoms in C11 and C13
are one connection closer to the Ru centre than C10 and
C12, respectively. The influences on the ligand-based re-
ductions are less significant (see Table 1).
The rigid geometry of the ligands L10 and L11 can result
in distortion of the inner coordination sphere of Ru, re-
sulting in a poorer overlap between the donor atoms of the
ligands and the dπ-orbitals of Ru, thus diminishing any
electronic effect from the fused electron-rich thiophene ring.
This, however, is not reflected in the luminescence results,
as both C10 and C11 display red luminescence with a life-
time and intensity comparable to those of [Ru(bpy)3]2+
,
compared with C1 where only a very weak red lumines-
cence is detected (see Table 2). The fusion of the thiophene
ring onto the c face does not introduce the same steric
strain to the inner coordination sphere, resulting in less pos-
itive RuIII/RuII couples and longer luminescence lifetimes
(see next section). In our earlier work,[5] a second oxidation
process at higher potentials was detected in the voltammog-
rams of complexes bearing a bithiophenyl moiety attached
to one of the bpy ligands, whereas those possessing only a
single (uncoupled) thiophene ring possessed no such wave.
Figure 4. Luminescence (RHS, λex = 337 nm) and excitation (LHS,
λfl = 410 nm) spectra of C2 in CH3CN solution.
The red luminescence spectra observed for complexes C2
As anticipated, no such oxidation processes were observed and C10–C13 were similar to that of [Ru(bpy)3]2+ with
for the complexes C1–C13 within the solvent limit.
small wavelength shifts, and the luminescence band max-
ima, quantum yield and lifetimes are given in Table 2. The
same emission spectra are observed when excited at either
337 or 450 nm. All excitation spectra indicate that the com-
plexes have similar excited state structures, whereas the
similarity in shape, lifetime and excitation maxima of the
emission indicates that for these complexes it originates
Table 2. Luminescence maxima, lifetimes and quantum yields for
the RuII complexes C1–C13.
[Ru(bpy)2Ln]2+ Luminescence peak [nm] Quantum yield [φ] τ [ns][a]
2+
Ru(bpy)3
C1
610
620
610
620
–
620
622
612
614
0.042 [11]
Ͻ 0.001
0.045
Ͻ 0.001
–
0.0047
0.013
0.014
1745
–
3000
–
3
from the same MLCT transition.
The weak red luminescence observed in complexes C1
and C3 was only detected in freshly prepared solutions. The
luminescence becomes weaker over time, disappearing after
several hours. It has been previously reported that photoly-
sis of [Ru(bpy)3]2+ results in loss of one bpy ligand;[11]
furthermore, it has been shown that in acetonitrile solutions
the formation of CH3CN-coordinated bis(bpy)rutheni-
um(II) complexes can occur.[12] Analysis by 1H NMR spec-
troscopy of CD3CN solutions of C1 and C3 indicated
C2
C3
C4–C9
C10
–
275
1040
1420
1510
C11
C12
C13
0.0097
[a] Luminescence lifetimes at 610 nm, in CH3CN under continuous
Ar purge, 17.5 °C. In all cases excitation is at 337 nm from an N2
laser.
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Luminescence Lifetimes and Electrochemistry of Tris(2,2Ј-bipyridine)ruthenium(II) Complexes
that under the influence of ambient light photosubstitu-
In addition, the luminescence of C10 and C11 is slightly
tion occurs, and the complex [Ru(bpy)2(CD3CN)2]2+ is redshifted with respect to C12 and C13 (Figure 5 and
formed,[13a–13c] with subsequent loss of luminescence. For Table 2) which may indicate that the filled t2g metal orbitals
the complexes C4–C9, the red luminescence was completely are shifted to higher energy, decreasing the energy of the
absent.
MLCT transition. The luminescence spectra in Figure 5
In the complexes where the red luminescence is weak were recorded at concentrations that gave the same absorp-
(C1, C3) or absent and the ligand does not contain a nitro tion at the 337 nm excitation wavelength in order to quan-
group (C4, C6, C7, C9) a blue emission characteristic of tify the quantum yield (Table 2). The quantum yields of the
the free ligand is observed. The origin of this blue emission complexes C10–C13 were somewhat smaller than that of
is unlikely to be a ligand-centred (LC) emission of the com- [Ru(bpy)3]2+, with that of C10 being the smallest. However,
plex, as the lifetimes are very short (Ͻ 10 ns) implying a all complexes with fused thiophene were markedly different
spin-allowed fluorescence, unlike the 3LC emission de- from the non-luminescent complexes with the thiophene at
tected, for example, in [Ru(i-biq)3]2+ (i-biq = 3,3Ј-biisoquin- the 6-position, C3–C9.
oline).[14] In addition the observed blue emission of these
complexes is unshifted with respect to that of the pure li-
gand, and has identical excitation spectra. We conclude that
this ligand emission is either due to small amounts of ligand
Conclusions
impurity in our samples, or that some ligand dissociation is
occurring. For the complexes containing the nitro group strongly with the structure of the chelating bipyridine unit;
(C5 and C8) neither blue nor red emission was observed. thus, both the position and mode of attachment have im-
The excited-state lifetimes were found to correlate
A comparison of the excitation and emission spectra of portant consequences for the establishment of a stable ex-
the four fused pyridyl-thienopyridine complexes C10–C13 cited electronic state. If the unique ligand possessed a thio-
is displayed in Figure 5. The lifetimes for C10–C13 are phene substituent in the 6-position of the 2,2Ј-bipyridine
somewhat shorter than those observed for [Ru(bpy)3]2+ and (motif L1) luminescence was very weak or absent.
the prototypic C2 under the same conditions. These four
The deactivation of luminescence from complexes with
red luminescent compounds are all isomers, and the differ- 6-substituted bipyridyl ligands is well known[16,3a] and has
ences in the luminescence lifetimes may be due to the dif- been rationalized by a decrease in the energy gap between
ferent accessibility of the C–H vibrations to the emission the MLCT and a higher metal-centred state (3MC) based
3
process, which would promote radiationless relaxation.
on ligand-field transitions to the σ*-orbitals. The 3MC state
is expected to have a large geometry change from the
ground state and provides an efficient pathway for radia-
tionless relaxation. This mechanism has been used to ex-
plain the weak luminescence of bis(terpyridine)RuII where
3
the MC state is lowered due to a weaker ligand field from
the small bite angle of the terpyridine ligand.[16] A distor-
tion in the coordination geometry from octahedral geome-
3
try is also thought to lower the MC state. In the present
case, presumably it is the distortion due to steric factors
between the pendant 6-thiophen-2-yl substituent and an ad-
jacent bipyridine auxiliary ligand that leads to deactivation
of the luminescence and the long-lived excited state desired
for electron transfer.
When the thiophene ring is moved to the 4-position (and
the 6-position is unsubstituted, motif L2), red luminescence
is observed with a higher quantum efficiency and a longer
lifetime than those of [Ru(bpy)3]2+ (see Table 2). The fusion
of the thiophene ring onto either the b or c face of one
of the pyridine rings, thereby ensuring a completely planar
interface between the chelator and the conjugation-ex-
tending thiophene ring, led to a series of ligands L10–L13,
the complexes of which all displayed red luminescence with
lifetimes slightly shorter than that of [Ru(bpy)3]2+. Fusions
to the b and c faces were chosen so as to achieve both a
non-charged thienopyridine (a charged system would result
from fusion to the a face) and to avoid steric interactions
within the interannular region of the bipyridine. Those
complexes which contained a fused thiophene on the c face
(C12 and C13) displayed the longest lifetimes in this series,
Figure 5. Luminescence (λex = 337 nm) and excitation spectra of
C10–C13 in CH3CN. The excitation spectra were measured by
monitoring the luminescence intensity of the peak position of the
luminescence spectra.
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S. J. Dunne et al.
FULL PAPER
as +87 mV vs. Ag/Ag+(MeCN)]. The potentials are correct to a
precision of Ϯ5 mV.
in line with the fact that their coordination geometries most
closely mimic that of [Ru(bpy)3]2+. As only weak electronic
coupling was found in bridged dimetallic complexes com-
prising the chelating motifs L1 and L2,[5] it is therefore of
interest to extend these studies through the generation of
bridged complexes by utilising the fused L12 and L13 mo-
tifs. The study of the photophysical properties and interval-
ence charge-transfer properties (IVCT) of such bridged
complexes will help elucidate the optimal structural and
electronic requirements for communication between metal
centres linked in this manner.
Synthetic Procedures
Representative Procedure for the Preparation of the Complexes from
Their Corresponding Ligands
[Ru(bpy)2(L3)] (C3): Ligand L3 (74.1 mg, 200 µmol) and Ru(bpy)2-
Cl2 (96.6 mg, 200 µmol) were dissolved in ethylene glycol (6 mL)
and heated to 120 °C. After 2 h, TLC showed complete consump-
tion of the ligand, and heating was stopped. When the mixture
reached room temp., a solution of ammonium hexafluorophos-
phate (97.8 mg, 600 µmol) in H2O (16 mL) was added. The mixture
was placed in a refrigerator overnight and then cooled in ice to
complete precipitation. The red precipitate was collected on a sin-
tered glass funnel and was purified by dissolution in the minimum
amount of CH3CN and addition to diethyl ether (200 mL). The red
precipitate was recovered by suction filtration and reprecipitated a
second time. The product was recovered by suction filtration
through a fine glass funnel. Analytical samples were prepared by
recrystallization from CH3CN or dichloromethane. Product ap-
pearance: orange/red powder. Yield: 193 mg (90%). 1H NMR
([D6]dmso, 300 MHz): δ = 9.22 (d, J = 8.0 Hz, 1 H), 9.15 (s, 1 H),
8.82 (d, J = 8.3 Hz, 1 H), 8.77–8.68 (m, 2 H), 8.51 (d, J = 5.6 Hz,
1 H), 8.39 (d, J = 8.2 Hz, 1 H), 8.28–8.14 (m, 3 H), 8.10–8.01 (m,
3 H), 7.86 (d, J = 1.4 Hz, 1 H), 7.80–7.68 (m, 2 H), 7.67–7.54 (m,
4 H), 7.54–7.43 (m, 2 H), 7.43–7.31 (m, 2 H), 7.22 (d, J = 4.9 Hz,
1 H), 7.09–6.95 (m, 2 H), 6.45 (br. s, 1 H), 1.32 (s, 9 H) ppm.
C44H38F12N6P2RuS (1073.89) + 4 H2O + 1/2 CH3CN: calcd. C
46.34, H 4.10, N 7.81; found C 46.24, H 3.97, N 7.78.
[Ru(bpy)2(L1)] (C1): Orange/red powder (75%). 1H NMR (CD3CN,
300 MHz): δ = 8.59 (m, 2 H), 8.48 (d, 1 H), 8.42 (d, 1 H), 8.40 (d,
1 H), 8.31 (dm, 1 H), 8.11 (td, 1 H), 8.10 (d, 1 H), 8.09 (m, 2 H),
8.08 (td, 1 H), 7.94 (td, 1 H), 7.70 (dm, 1 H), 7.65 (td, 1 H), 7.56
(dm, 1 H), 7.52 (m, 1 H), 7.48 (d, 1 H), 7.39 (dm, 1 H), 7.38 (m, 1
H), 7.33 (m, 1 H), 7.21 (m, 1 H), 7.11 (dm, 1 H), 7.04 (d, 1 H),
6.89 (m, 1 H), 6.40 (m, 1 H) ppm. C34H26F12N6P2RuS (941.69) +
1/3 CH2Cl2: calcd. C 42.51, H 2.77, N 8.66; found C 42.74, H 2.92,
N 8.57. MS (MALDI-TOF): m/z (calcd.) = 653 (651.7) [M + H –
2 PF6]+.
[Ru(bpy)2(L2)] (C2): Orange/red powder (81%). 1H NMR (CD3CN,
300 MHz): δ = 8.68 (d, 1 H), 8.65 (s, 1 H), 8.47–8.53 (d, 4 H), 8.08
(td, 1 H), 8.03–8.10 (td, 4 H), 7.90 (dd, 1 H), 7.76 (dm, 1 H), 7.84
(dm, 4 H), 7.71 (dd, 1 H), 7.64 (d, 1 H), 7.56 (d, 1 H), 7.42 (m, 1
H), 7.37–7.45 (m, 4 H), 7.27 (m, 1 H) ppm. C34H26F12N6P2RuS
(941.69) + 1/3 CH2Cl2: calcd. C 42.51, H 2.77, N 8.66; found C
42.59, H 2.83, N 8.45. MALDI-TOF MS: m/z (calcd.) = 796 (796.7)
[M – PF6]+, 652 (651.7) [M – 2 PF6]+.
[Ru(bpy)2(L4)] (C4): Orange/red powder (85%). 1H NMR (CD3CN,
300 MHz): δ = 8.79–8.74 (m, 2 H), 8.49–8.31 (m, 4 H), 8.14–8.04
(m, 4 H), 7.97–7.89 (m, 3 H), 7.74–7.70 (m, 2 H), 7.65 (dt, J = 1.4,
7.9 Hz, 1 H), 7.58–7.48 (m, 2 H), 7.42–7.30 (m, 3 H), 7.22 (ddd, J
= 1.2, 5.7, 7.6 Hz, 1 H), 7.16–7.08 (m, 3 H), 7.03 (d, J = 5.4 Hz, 1
H), 6.87 (ddd, J = 1.2, 5.7, 7.6 Hz, 1 H), 6.40 (t, J = 3.9 Hz, 1 H),
3.88 (s, 3 H) ppm. C41H32F12N6OP2RuS (1047.81) + 2 H2O: calcd.
C 45.44, H 3.35, N 7.75; found C 45.55, H 3.48, N 7.71. MALDI-
TOF MS: m/z (calcd.) = 901.9 (901.9) [M – H – PF6]+, 756.0 (755.9)
[M – 2 H – 2 PF6]+.
Experimental Section
General: All moisture- and air-sensitive reactions were performed
in oven-dried (120 °C, 12 h) glassware under nitrogen. Analytical
TLC was performed on commercially prepared plates coated with
0.20 mm of Macherey–Nagel silica gel 60. The compounds were
visualized by illumination with UV light (254 nm). Column
chromatography was performed by using Matrex Normal Phase
Silica 60 (particle size 35–70 µm). All melting points were deter-
mined by using an Electrothermal 9200 melting point apparatus
and are uncorrected. Infrared spectra (IR) were measured with a
Perkin–Elmer Spectrum One spectrophotometer. Mass spectra
(MS) were obtained with a Fisions Instrument Trio 1000 spectrom-
eter equipped with a Hewlett Packard 5MS GC column. NMR
spectra were recorded with a Bruker DPX Avance 300 MHz spec-
trometer, and the chemical shifts are expressed in ppm from tet-
ramethylsilane as internal standard. Abbreviations for signal coup-
ling are as follows: s, singlet; d, doublet; t, triplet; q, quartet; dd,
doublet of doublets; ddd, doublet of doublets of doublets; dt,
doublet of triplets; m, multiplet; br., broad. All commercially avail-
able chemicals were used as received unless otherwise noted.
Steady-state luminescence spectra were acquired with an ISS PC1
fluorimeter in photon-counting mode immediately after purging
with argon gas. Concentrations were adjusted to give an absorption
of 0.05 at the excitation wavelength of 337 nm, and were in the
range 1–3ϫ10–6 . Luminescence lifetimes were measured by using
the 337 nm excitation of an N2 laser at 2 Hz. After a long-pass
filter and Jobin Yvon H-20 monochromator centred at 610 nm, the
luminescence was detected by an S-20 photomultiplier tube. The
signal was amplified by two stages of a Stanford 445 preamplifier
and collected with a Tektronix TDS4010 digital storage oscillo-
scope. The solutions were purged with argon for 20 min before and
during the lifetime measurements. The red-emitting compounds
show a strong sensitivity to dissolved oxygen. All luminescence
measurements were carried out with acetonitrile solutions at
17.5 °C. Quantum effiency measurements were obtained from inte-
grating the spectra when plotted in wavenumber, adjusting for the
refractive index of acetonitrile and using the value of φ = 0.042 for
[Ru(bpy)3]2+ as a standard.[15,17] The error in the measurments were
as follows; luminescence peak Ϯ1 nm; quantum yield Ϯ10%; lumi-
nescence lifetimes Ϯ10 ns. Cyclic voltammetry was performed with
a BAS100B/W electrochemical workstation by employing a glassy
carbon working electrode (3 mm), an Ag/Ag+ (MeCN) non-aque-
ous reference electrode and a Pt wire counter electrode. All solu-
tions contained ca. 1 m complex in CH3CN, and the supporting
electrolyte was Et4NClO4. The electrochemical cell was purged with
nitrogen before measurement and maintained anaerobic during
measurement with a blanket of nitrogen. All potentials are cited
relative to the ferrocene/ferrocenium redox couple [measured here
[Ru(bpy)2(L5)] (C5): Orange/red powder (89%). 1H NMR (CD3CN,
300 MHz): δ = 8.86 (d, J = 1.9 Hz, 1 H), 8.79 (d, J = 8.1 Hz, 1 H),
8.52–8.35 (m, 5 H), 8.32 (d, J = 5.3 Hz, 1 H), 8.18–8.05 (m, 6 H),
7.95 (dt, J = 1.4, 7.9 Hz, 1 H), 7.81 (d, J = 1.9 Hz, 1 H), 7.75–7.48
(m, 4 H), 7.45–7.32 (m, 3 H), 7.23 (dt, J = 1.2, 7.0 Hz, 1 H), 7.12
4106
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Eur. J. Inorg. Chem. 2008, 4101–4110

Luminescence Lifetimes and Electrochemistry of Tris(2,2Ј-bipyridine)ruthenium(II) Complexes
(d, J = 5.1 Hz, 1 H), 7.05 (d, J = 4.9 Hz, 1 H), 6.89 (t, J = 6.1 Hz, [Ru(bpy)2(L12)] (C12): Orange/red powder (95%). 1H NMR
1 H), 6.41 (br. t, 1 H) ppm. C40H29F12N7O2P2RuS (1062.78): calcd.
C 45.21, H 2.71, N 9.23; found C 45.09, H 2.89, N 8.95.
(CD3CN, 300 MHz): δ = 9.15 (s, 1 H), 8.54–8.44 (m, 5 H), 8.25 (d,
J = 0.44 Hz, 1 H), 8.11–7.98 (m, 5 H), 7.93 (d, J = 5.5 Hz, 1 H),
7.81–7.67 (m, 5 H), 7.45–7.31 (m, 6 H) ppm. C32H24F12N6P2RuS
(915.65) + 2 H2O: calcd. C 40.39, H 2.97, N 8.83; found C 40.64,
H 2.58, N 8.66. MALDI-TOF MS: m/z (calcd.) = 770.7 (770.7)
[M – PF6]+, 625.5 (625.8) [M – 2 PF6]+.
[Ru(bpy)2(L6)] (C6): Orange/red powder (70%). 1H NMR (CD3CN,
300 MHz): δ = 8.79 (d, J = 2.0 Hz, 1 H), 8.76 (d, J = 8.2 Hz), 8.50–
8.35 (m, 3 H), 8.25 (d, J = 5.5 Hz, 1 H), 8.14–8.05 (m, 4 H), 8.95
(dt, J = 1.4, 7.9 Hz, 1 H), 7.89 (d, J = 8.6 Hz, 2 H), 7.77 (d, J =
2.0 Hz, 1 H), 7.75–7.67 (m, 2 H), 7.64 (d, J = 8.6 Hz, 2 H), 7.57
(d, J = 5.6 Hz, 1 H), 7.51 (ddd, J = 1.2, 5.7, 7.6 Hz, 1 H), 7.44–
7.30 (m, 3 H), 7. 23 (ddd, J = 1.3, 5.7, 7.6 Hz), 7.18 (d, J = 5.6 Hz,
1 H), 6.95 (ddd, J = 1.2, 5.7, 7.6, 1 H), 6.5–5.7 (br. m, 2 H), 2.18
(s, 3 H), 1.37 (s, 9 H) ppm. C45H40F12N6P2RuS (1087.92) + 2 H2O:
calcd. C 48.09, H 3.95, N 7.48; found C 48.31, H 3.48, N 7.51.
MALDI-TOF MS: m/z (calcd.) = 941.9 (942.1) [M – 2 H – PF6]+.
[Ru(bpy)2(L7)] (C7): Orange/red powder (35%). 1H NMR (CD3CN,
300 MHz): δ = 8.78–8.72 (m, 2 H), 8.50–8.36 (m, 3 H), 8.28 (d, J
= 5.1 Hz, 1 H), 8.13–8.04 (m, 4 H), 8.00–7.88 (m, 3 H), 7.74–7.66
(m, 3 H), 7.56 (d, J = 5.0 Hz, 1 H), 7.50 (ddd, J = 1.2, 5.7, 7.6 Hz,
1 H), 7.43–7.29 (m, 3 H), 7.26–7.09 (m, 4 H), 6.94 (ddd, J = 1.2,
6.0, 7.2 Hz, 1 H), 6.5–5.7 (br. m, 2 H), 3.88 (s, 3 H), 2.18 (s, 3 H)
ppm. C42H34F12N6OP2RuS (1045.84) + 1/2 H2O: calcd. C 47.11, H
3.29, N 7.85; found C 46.83, H 2.89, N 7.84.
[Ru(bpy)2(L8)] (C8): Red/brown powder (79%). 1H NMR (CD3CN,
300 MHz): δ = 8.83 (d, J = 2.1 Hz, 1 H), 8.77 (d, J = 8.2 Hz, 1 H),
8.50–8.37 (m, 5 H), 8.25 (d, J = 5.6 Hz, 1 H), 8.15–8.05 (m, 6 H),
7.96 (dt, J = 1.5, 7.9 Hz, 1 H), 7.81 (d, J = 2.0 Hz, 1 H), 7.75–7.67
(m, 2 H), 7.58 (d, J = 5.7 Hz, 1 H), 7.51 (ddd, J = 1.3, 5.7, 7.6 Hz,
1 H), 7.43–7.32 (m, 3 H), 7.26 (ddd, J = 1.3, 5.7, 7.6 Hz, 1 H), 7.17
(d, J = 5.6 Hz, 1 H), 6.95 (ddd, J = 1.3, 5.6, 7.6 Hz, 1 H), 6.5–5.7
(br. m, 2 H), 2.18 (s, 3 H) ppm. C41H31F12N7O2P2RuS (1076.81) +
1/2 H2O: calcd. C 45.35, H 2.97, N 9.03; found C 45.08, H 2.58,
N 9.02. MALDI-TOF MS: m/z (calcd.) = 785.2 (785.2) [M – H –
PF6]+.
[Ru(bpy)2(L9)] (C9): Orange/red powder (64%). 1H NMR (CD3CN,
300 MHz): δ = 8.74 (d, J = 8.2 Hz, 1 H), 8.67 (d, J = 2.1 Hz, 1 H),
8.50–8.35 (m, 3 H), 8.30 (d, J = 5.6 Hz, 1 H), 8.15–8.04 (m, 4 H),
7.98–7.91 (m, 2 H), 7.76–7.65 (m, 4 H), 7.56 (d, J = 5.6 Hz, 1 H),
7.51 (ddd, J = 1.2, 5.7, 7.6 Hz, 1 H), 7.43–7.30 (m, 3 H), 7.27 (dd,
J = 3.8, 5.0 Hz, 1 H), 7.22 (ddd, J = 1.2, 5.7, 7.6 Hz, 1 H), 7.16 (d,
J = 5.6 Hz, 1 H), 6.95 (ddd, J = 1.2, 5.7, 7.6 Hz, 1 H), 6.6–5.3 (br.
m, 2 H), 2.18 (s, 3 H) ppm. C39H30F12N6P2RuS2 (1051.84) + 1
H2O: calcd. C 44.36, H 3.05, N 7.96; found C 44.11, H 2.68, N
7.68. MALDI-TOF MS: m/z (calcd.) = 891.9 (891.9) (M – H –
PF6)+, 746.0 (746.0) (M – 2 H – 2 PF6)+.
[Ru(bpy)2(L13)] (C13): Orange/red powder (60%). 1H NMR
(CD3CN, 300 MHz): δ = 9.01 (s, 1 H), 8.56–8.49 (m, 5 H), 8.39 (s,
1 H), 8.12 (d, J = 5.4 Hz, 1 H), 8.12–8.01 (m, 5 H), 7.83–7.73 (m,
5 H), 7.71 (d, J = 5.4 Hz, 1 H), 7.45–7.33 (m, 5 H) ppm.
C32H24F12N6P2RuS (915.65) + 1 H2O: calcd. C 41.17, H 2.81, N
9.00; found C 41.09, H 2.82, N 8.90. MALDI-TOF MS: m/z
(calcd.) = 769.7 (769.7) [M – H – PF6]+, 624.8 (624.8) [M – H – 2
PF6]+.
Preparation of Ligand L1
6-(Thiophen-2-yl)-2,2Ј-bipyridine (L1): This compound was pre-
pared according to the method of Constable, Henney and Leese.[7]
Yield: 65%. M.p. 78 °C (ref.[6,10] 78 °C). FT-IR: ν = 3051 (w), 1578
˜
(m), 1561 (s), 1530 (m), 1475 (m), 1454 (s), 1425 (s), 1349 (w), 1311
(w), 1290 (w), 1268 (w), 1227 (w), 1152 (m), 1091 (w), 1079 (m),
1045 (w), 996 (m), 967 (w), 905 (w), 852 (m), 825 (w), 778 (s), 746
(w), 737 (w), 717 (s), 689 (m), 652 (w), 625 (m), 569 (w), 508 (w)
1
cm–1. H NMR (CDCl3, 300 MHz): δ = 8.68 (br. d, 1 H), 8.58 (d,
J = 7.8 Hz, 1 H), 8.29 (dd, J = 1.0, 7.8 Hz, 1 H), 7.85 (dt, J = 2.0,
7.8 Hz, 1 H), 7.81 (t, J = 7.8 Hz, 1 H), 7.66 (dd, J = 1.0, 7.8 Hz, 1
H), 7.65 (dd, J = 1.0, 3.4 Hz, 1 H), 7.42 (dd, J = 1.0, 4.9 Hz, 1 H),
7.29–7.34 (m, 1 H), 7.13 (dd, J = 3.4, 4.9 Hz, 1 H) ppm.
Representative Procedure for the Preparation of Ligands L2–L9
4-(4-tert-Butylphenyl)-6-(thiophen-2-yl)-2,2Ј-bipyridine (L3): Pro-
penone P3 (2.70 g, 10 mmol), 2-[1-oxo-2-(1-pyridinio)ethyl]pyr-
idine iodide[6] (3.26 g, 10 mmol) and ammonium acetate (3.85 g,
50 mmol) were dissolved in glacial acetic acid (40 mL) and refluxed
for 4 h. The reaction mixture was cooled to room temperature and
then in ice before being rendered alkaline with NaOH and then
extracted with dichloromethane (3ϫ50 mL). The collected organic
phases were washed with water (50 mL) and brine (50 mL) and
dried with MgSO4. After evaporation of the solvent, a black oil
was obtained, which was purified by column chromatography with
an EtOAc/hexane (1:6) eluent system. The product glows intensely
blue upon radiation at 356 nm on a TLC plate. Recrystallization
from methanol gave a pure product. Product appearance: yellow
crystals. Yield: 1.15 g (31%). M.p. 129.7–131.2 °C. FT-IR: ν = 2962
˜
[Ru(bpy)2(L10)] (C10): Orange/red powder (78%). 1H NMR
(CD3CN, 300 MHz): δ = 8.68 (dd, J = 8.7, 0.75 Hz, 1 H), 8.64 (d,
J = 8.2 Hz, 1 H), 8.69–8.47 (m, 4 H), 8.44 (d, J = 8.1 Hz, 1 H),
8.14–8.05 (m, 4 H), 8.00 (dt, J = 1.4, 7.9 Hz, 1 H), 7.92–7.85 (m,
2 H), 7.81 (d, J = 5.81 Hz, 1 H), 7.67–7.60 (m, 3 H), 7.46 (ddd, J
= 1.4, 5.7, 7.5 Hz, 1 H), 7.42–7.31 (m, 4 H), 6.12 (dd, J = 5.8,
0.75 Hz, 1 H) ppm. C32H24F12N6P2RuS (915.65) + 1/2 H2O: calcd.
C 41.57, H 2.73, N 9.09; found C 41.21, H 2.35, N 8.92. MALDI-
TOF MS: m/z (calcd.) = 770.7 (770.7) [M – PF6]+, 625.5 (625.7)
[M – 2 PF6]+.
(m), 1600 (s), 1583 (s), 1567 (m), 1542 (s), 1473 (m), 1434 (w),
1388 (m), 830 (s), 793 (s), 743 (w), 699 (s), 540 (w) cm–1. 1H NMR
(300 MHz, CDCl3): δ = 8.73 (d, J = 4.1 Hz, 1 H), 8.66 (d, J =
8.0 Hz, 1 H), 8.63 (s, 1 H), 7.95–7.86 (m, 2 H), 7.78 (d, J = 8.4 Hz,
1 H), 7.73 (dd, J = 1.1, 3.7 Hz, 1 H), 7.54 (d, J = 8.4 Hz, 1 H),
7.43 (dd, J = 1.1, 5.1 Hz, 1 H), 7.38 (ddd, J = 0.9, 5.1, 7.1 Hz, 1
H), 7.16 (dd, J = 3.7, 5.1 Hz, 1 H), 1.38 (s, 9 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 156.2, 155.9, 152.8, 152.7, 150.4, 149.1,
145.7, 137.7, 135.8, 128.4, 128.0, 127.4, 125.0, 124.3, 122.1, 117.7,
117.1, 35.2, 31.8 ppm.
[Ru(bpy)2(L11)] (C11): Orange/red powder (93%). 1H NMR
(CD3CN, 300 MHz): δ = 8.61 (d, J = 8.2 Hz, 1 H), 8.58–8.43 (m,
4-(Thiophen-2-yl)-2,2Ј-bipyridine (L2): Pale yellow prisms (44%).
M.p. 106–107.5 °C. FT-IR: ν = 3074 (w), 3048 (w), 2999 (w), 1598
˜
6 H), 8.12–7.98 (m, 5 H), 7.84 (d, J = 5.6 Hz, 1 H), 7.74 (d, J = (s), 1580 (s), 1563 (s), 1547 (s), 1522 (m), 1457 (s), 1424 (m), 1395
5.6 Hz, 1 H), 7.68–7.60 (m, 3 H), 7.52 (d, J = 6.0 Hz, 1 H), 7.47
(d, J = 6.0 Hz, 1 H), 7.43–7.29 (m, 5 H) ppm. C32H24F12N6P2RuS
(915.45): calcd. C 41.98, H 2.64, N 9.18; found C 41.80, H 2.22, N
9.18. MALDI-TOF MS: m/z (calcd.) = 770.7 (770.7) [M – PF6]+,
625.5 (625.8) [M – 2 PF6]+.
(s), 1357 (w), 1345 (w), 1286 (w), 1270 (w), 1256 (w), 1233 (w),
1196 (w), 1151 (w), 1094 (w), 1054 (w), 990 (m), 910 (w), 891 (w),
855 (w), 823 (w), 795 (s), 741 (w), 700 (s), 659 (w), 637 (w), 617 (w)
cm–1. 1H NMR (CDCl3, 300 MHz): δ = 8.73 (m, J = 4.8, 0.9 Hz, 1
H), 8.69–8.64 (m, 2 H), 8.44 (d, J = 8.0 Hz, 1 H), 7.85 (dt, J = 7.8,
Eur. J. Inorg. Chem. 2008, 4101–4110
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4107

S. J. Dunne et al.
FULL PAPER
1.8 Hz, 1 H), 7.67 (dd, J = 3.7, 1.1 Hz, 1 H), 7.53 (dd, J = 5.2,
1.9 Hz, 1 H), 7.45 (dd, J = 5.1, 1.1 Hz, 1 H), 7.36 (ddd, J = 7.5,
3.6, 1.2 Hz, 1 H), 7.17 (dd, J = 5.1, 3.6 Hz, 1 H) ppm. 13C NMR
(d, J = 8.0 Hz, 1 H), 8.52 (d, J = 1.4 Hz, 1 H), 8.37 (d, J = 8.8 Hz,
2 H), 7.94 (d, J = 8.8 Hz, 2 H), 7.89 (td, J = 7.7, 1.7 Hz, 1 H), 7.78
(d, J = 1.4 Hz, 1 H), 7.55 (d, J = 3.6 Hz, 1 H), 7.36 (dd, J = 4.8,
(CDCl3, 75 MHz): δ = 157.0, 156.1, 150.0, 149.4, 142.6, 141.7, 1.1 Hz, 1 H), 6.81 (d, J = 3.6, 1.2 Hz, 1 H), 2.58 (s, 3 H) ppm. 13C
137.2, 128.6, 127.4, 125.8, 124.1, 121.5, 120.1, 117.4 ppm.
NMR ([D6]dmso, 75 MHz): δ = 156.8, 156.0, 153.4, 149.5, 148.6,
148.1, 145.5, 143.6, 142.6, 137.5, 128.6, 126.9, 125.6, 124.7, 124.6,
122.0, 117.1, 116.5, 16.1 ppm.
4-(4-Methoxyphenyl)-6-(thiophen-2-yl)-2,2Ј-bipyridine (L4): Yellow
crystals (51%). M.p. 145.9–147.3 °C. FT-IR: ν = 1598 (m), 1582
˜
6-(5-Methylthiophen-2-yl)-4-(thiophen-2-yl)-2,2Ј-bipyridine
(L9):
(m), 1568 (w), 1543 (w), 1515 (s), 1472 (w), 1424 (w), 1391 (w),
1295 (w), 1257 (m), 1183 (w), 1110 (w), 1032 (w), 829 (m), 795 (m),
Yellow crystals (47%). M.p. 116.8–121.0 °C. FT-IR: ν = 2909.4 (w),
˜
1
714 (m), 575 (w), 513 (w) cm–1. H NMR (CDCl3, 300 MHz): δ =
1596.3 (m), 1581.9 (m), 1556.6 (m), 1543.0 (m), 1403.5 (m), 789.0
1
(s), 694.3 (s) cm–1. H NMR (CDCl3, 300 MHz): δ = 8.71 (d, J =
8.72 (d, J = 0.8, 4.8 Hz, 1 H), 8.64 (d, J = 8.0 Hz, 1 H), 8.55 (d, J
= 1.2 Hz, 1 H), 7.88 (dt, J = 1.6, 8.0 Hz, 1 H), 7.85 (d, J = 1.5 Hz,
1 H), 7.78 (d, J = 8.8 Hz, 2 H), 7.73 (dd, J = 1.0, 3.7 Hz, 1 H),
7.44 (dd, J = 1.0, 5.0 Hz, 1 H), 7.34 (ddd, J = 0.8, 7.3, 4.9 Hz, 1
H), 7.17 (dd, J = 3.7, 5.0 Hz, 1 H), 7.04 (d, J = 8.8 Hz, 2 H), 3.89
(s, 9 H) ppm. 13C NMR (CDCl3, 75 MHz): δ = 160.9, 156.4, 152.7,
150.1, 149.4, 145.9, 137.4, 131.1, 128.8, 128.4, 128.0, 124.9, 124.3,
122.0, 117.1, 116.5, 114.8, 55.8 ppm.
4.8 Hz, 1 H), 8.58 (d, J = 8.1 Hz, 1 H), 8.49 (d, J = 1.5 Hz, 1 H),
7.86 (td, J = 7.5, 1.8 Hz, 1 H), 7.77 (d, J = 1.5 Hz, 1 H), 7.68 (dd,
J = 3.6, 1.8 Hz, 1 H), 7.53 (d, J = 3.60 Hz, 1 H), 7.44 (dd, J = 5.1,
1.2 Hz, 1 H), 7.34 (dd, J = 4.8, 1.2 Hz, 1 H), 7.17 (dd, J = 5.1,
3.6 Hz, 1 H), 6.82 (dd, J = 3.6, 1.2 Hz, 1 H), 2.58 (s, 3 H) ppm.
13C NMR (CDCl3, 75 MHz): δ = 156.5, 156.2, 153.1, 149.4, 143.4,
143.1, 142.9, 142.1, 137.3, 128.7, 127.4, 126.8, 126.0, 125.2, 124.3,
121.9, 115.4, 114.8, 16.2 ppm.
4-(4-Nitrophenyl)-6-(thiophen-2-yl)-2,2Ј-bipyridine (L5): Green crys-
L10, L11 and L12 were prepared as reported earlier.[8] Experimen-
tal schemes are enclosed in the Supporting Information.
tals (28%). M.p. 167.4–169.4 °C (ref.[6] 183 °C). FT-IR: ν = 3110
˜
(w), 3087 (w), 1651 (w), 1595 (m), 1581 (m), 1548 (m), 1511 (s),
1472 (w), 1435 (w), 1419 (w), 1387 (w), 1346 (s), 1242 (w), 1110
(w), 859 (w), 851 (m), 793 (w), 780 (w), 755 (m), 742 (w), 689 (m)
L13 was prepared via the intermediate compounds 14–16.
3-{2-(Pyridin-2-yl)vinyl]-2-1,3-dioxolan-2-yl}thiophene (14): 2-(3-
Bromothiophen-2-yl)-1,3-dioxolane[9] (1.65 g, 7 mmol), 2-vinylpyr-
idine (0.75 g, 7 mmol) and potassium carbonate (1.93 g, 14 mmol)
were dissolved in DMF (20 mL, dried with molecular sieves). The
solution was thoroughly stirred for 10 min before the addition of
tetrakis(triphenylphosphane)palladium (40 mg, 35 µmol, 0.5 mol-%).
The solution was refluxed, and the reaction was monitored by
TLC. After 8 h, TLC indicated that all starting material had been
consumed, and the reaction mixture was poured into water
(200 mL). The resulting precipitate was filtered through a fine sin-
tered glass funnel and became a viscous oil on the funnel surface.
Extraction with boiling heptane provided 14, which was further
purified by flash chromatography [silica, hexane/EtOAc (1:1)].
Product appearance: viscous yellow oil. Yield: 1.71 g (94%). 1H
NMR (300 MHz, CDCl3): δ = 8.60 (d, J = 4.8 Hz, 1 H), 7.76 (d,
J = 16.0 Hz, 1 H), 7.65 (dt, J = 1.8, 7.7 Hz, 1 H), 7.37 (d, J =
8.0 Hz, 1 H), 7.35 (d, J = 5.3 Hz, 1 H), 7.28 (d, J = 5.3 Hz, 1 H),
7.14 (ddd, J = 1.1, 4.8, 7.5 Hz, 1 H), 7.04 (d, J = 16.0 Hz, 1 H),
6.37 (s, 1 H), 4.23–4.00 (m, 4 H) ppm. 13C NMR (CDCl3, 75 MHz):
δ = 155.7, 149.8, 138.6, 137.5, 136.7, 129.7, 126.0, 125.8, 124.4,
122.3, 122.2, 99.1, 65.6 ppm. MS: m/z = 259 [M+]. C14H13NO2S
(259.32): calcd. C 64.84, H 5.05, N 5.40; found C 64.68, H 4.88, N
5.29.
1
cm–1. H NMR ([D6]dmso, 300 MHz): δ = 8.74 (d, J = 4.5 Hz, 1
H), 8.56 (s, 1 H), 8.48 (d, J = 7.9 Hz, 1 H), 8.39 (d, J = 8.7 Hz, 2
H), 8.37 (s, 1 H), 8.24 (d, J = 8.7 Hz, 2 H), 8.11 (d, J = 3.7 Hz, 1
H), 8.04 (dt, J = 1.6, 7.6 Hz, 2 H), 7.73 (d, J = 5.0 Hz, 2 H), 7.53
(dd, J = 4.9, 7.4 Hz, 1 H), 7.25 (dd, J = 4.8, 3.9 Hz, 1 H) ppm. 13
C
NMR ([D6]dmso, 75 MHz): δ = 156.5, 155.2, 153.4, 150.2, 148.8,
148.0, 144.9, 144.4, 138.4, 130.0, 129.43, 129.41, 127.4, 125.6,
125.1, 121.6, 117.6, 117.2 ppm.
4-(4-tert-Butylphenyl)-6-(5-methylthiophen-2-yl)-2,2Ј-bipyridine (L6):
Yellow crystals (39%). M.p. 162.0–164.8 °C. FT-IR: ν = 2963.2
˜
(m), 2866.5 (w), 1596.0 (s), 1581.9 (s), 1566.0 (s), 1539.5 (s), 1479.6
(s), 1389.2 (s), 1244.7 (w), 1116.8 (w), 1017.0 (w), 830.7 (s), 794.2
1
(s), 743.66 (w), 541.9 (w) cm–1. H NMR (CDCl3, 300 MHz): δ =
8.70 (d, J = 4.2 Hz, 1 H), 8.61 (d, J = 8.0 Hz, 1 H), 8.52 (d, J =
1.4 Hz, 1 H), 7.86 (td, J = 7.6, 1.8 Hz, 1 H), 7.81 (d, J = 1.5 Hz, 1
H), 7.75 (d, J = 8.5 Hz, 2 H), 7.54 (d, J = 8.6 Hz, 2 H), 7.54 (d, J
= 2.0 Hz, 1 H), 7.33 (dd, J = 4.8, 1.2 Hz, 1 H), 6.81 (dd, J = 3.6,
0.9 Hz, 1 H), 2.58 (s, 3 H), 1.45 (s, 9 H) ppm. 13C NMR (CDCl3,
75 MHz): δ = 160.2, 159.9, 156.3, 156.2, 153.9, 153.0, 147.0, 146.4,
140.9, 139.6, 130.9, 130.3, 129.9, 128.6, 127.7, 125.5, 120.7, 120.0,
38.7, 35.3 ppm.
4-(4-Methoxyphenyl)-6-(5-methylthiophen-2-yl)-2,2Ј-bipyridine (L7):
Yellow crystals (20%). M.p. 150.0–155.0 °C. FT-IR: ν = 3435.0 (w),
˜
3-[2-(Pyridin-2-yl)vinyl]thiophene-2-carbaldehyde (15): A solution of
KHSO4 (0.90 g, 6.6 mmol) in H2O (5 mL) was added to a solution
of 14 (1.55 g, 6.0 mmol) in acetone (20 mL). The mixture instantly
turned cloudy and yellow. The mixture was refluxed, and, after 2 h,
TLC showed the total consumption of the starting material. The
acetone was evaporated, and water was added (200 mL), thus dis-
solving most of the inorganic precipitate. The solution was ex-
tracted with dichloromethane (3ϫ50 mL), the organic extracts
were combined and were dried with anhydrous MgSO4 and concen-
trated to provide pure 15. Product appearance: viscous yellow oil.
2914.0 (w), 1608.4 (s), 1598.2 (s), 1517 (s), 1423.4 (s), 1254.7 (s),
1184.8 (s), 1110.8 (m), 1029.6 (s), 837.1 (m), 797.0 (s), 744.6 (m),
574.0 (m) cm–1. 1H NMR (CDCl3, 300 MHz): δ = 8.69 (d, J =
0.9 Hz, 1 H), 8.60 (d, J = 7.8 Hz, 1 H), 8.48 (d, J = 1.5 Hz, 1 H),
7.85 (td, J = 7.5, 1.8 Hz, 1 H), 7.78 (s, 1 H), 7.77 (d, J = 9.0 Hz, 2
H), 7.46 (d, J = 3.6 Hz, 1 H), 7.36 (dd, J = 5.6, 1.2 Hz, 1 H), 7.04
(d, J = 9.0 Hz, 2 H), 6.82 (dd, J = 3.6, 1.2 Hz, 1 H), 3.89 (s, 3 H),
2.55 (s, 3 H) ppm. 13C NMR (CDCl3, 75 MHz): δ = 160.8, 156.1,
156.1, 156.7, 149.8, 149.2, 143.1, 142.6, 137.1, 131.1, 128.6, 126.5,
124.8, 124.0, 121.7, 116.5, 115.8, 114.6, 55.4, 16.2 ppm.
1
Yield: 1.12 g (87%). H NMR (300 MHz, CDCl3): δ = 10.31 (s, 1
H), 8.64 (d, J = 4.6 Hz, 1 H), 8.20 (d, J = 15.9 Hz, 1 H), 7.75–7.67
(m, 2 H), 7. 49 (d, J = 5.1 Hz, 1 H), 7.43 (d, J = 7.8 Hz), 7.26–7.18
(m, 2 H) ppm. MS: m/z = 215 [M+]. C12H9NOS (215.27): calcd. C
66.95, H 4.21, N 6.51; found C 67.07, H 4.37, N 6.40.
6-(5-Methylthiophen-2-yl)-4-(4-nitrophenyl)-2,2Ј-bipyridine
(L8):
Yellow needles (3.5%). M.p. 212.8–214.1 °C. FT-IR: ν = 3413.5
˜
(w), 3052.1 (w), 2917.4 (w), 2850.0 (w), 1595.1 (m), 1566.9 (m),
1584.6 (s), 1471.0 (s), 1345.0 (s), 1248.1 (m), 1108.3 (m), 852.1 (m),
754.8 (m), 741.4 (w), 696.28 (w), 616.3 (w), 469.5 (w) cm–1. 1H 3-[2-(Pyridin-2-yl)vinyl]thiophene-2-carbaldehyde Oxime (16): The
NMR ([D6]dmso, 300 MHz): δ = 8.70 (d, J = 4.7 Hz, 1 H), 8.62
aldehyde 15 (1.04 g, 4.8 mmol), hydroxylamine hydrochloride
4108
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 4101–4110

Luminescence Lifetimes and Electrochemistry of Tris(2,2Ј-bipyridine)ruthenium(II) Complexes
7.19 (dd, J = 3.8, 4.9 Hz, 1 H), 1.35 (s, 9 H) ppm. 13C NMR
(0.67 g, 9.7 mmol) and sodium acetate (0.79 g, 9.7 mmol) were
added to ethanol (16 mL), and the mixture was refluxed. The reac-
tion was monitored by TLC and stopped when no starting material
was present anymore. Two products [(E) and (Z) isomers] were de-
tected. The ethanol was evaporated, and H2O (50 mL) was added
to the oily residue. The mixture was then extracted with dichloro-
methane (3ϫ50 mL) and then with ethyl acetate (3ϫ50 mL). The
isomers show different solubility characteristics in the two solvents,
although this was not investigated further. The organic extracts
were combined, dried with anhydrous MgSO4 and concentrated to
afford 16 sufficiently pure for the following step. Product appear-
ance: yellow powder. Yield: 1.09 g (99%). 1H NMR (300 MHz,
CDCl3): (E) isomer: δ = 8.73 (s, 1 H), 8.64 (d, J = 4.8 Hz, 1 H),
7.89 (d, J = 15.8 Hz, 1 H), 7.70 (dt, J = 2.0, 7.7 Hz, 1 H), 7.39 (d,
J = 7.8 Hz, 1 H), 7.36 (d, J = 5.5 Hz, 1 H), 7.29 (d, J = 5.4 Hz, 1
H), 7.20 (m, 1 H), 7.05 (d, J = 15.8 Hz, 1 H) ppm; (Z) isomer: δ =
8.64 (d, J = 4.8 Hz, 1 H), 8.17 (s, 1 H), 7.97 (d, J = 15.8 Hz, 1 H),
7.71 (dt, J = 2.0, 7.7 Hz, 1 H), 7.53 (d, J = 5.4 Hz, 1 H), 7.43 (d,
J = 5.3 Hz, 1 H), 7.39 (d, J = 7.8 Hz, 1 H), 7.20 (m, 1 H), 7.12 (d,
J = 15.8 Hz, 1 H) ppm. MS: m/z = 230 [M+]. C12H10N2OS (230.28):
calcd. C 62.59, H 4.38, N 12.16; found C 62.71, H 4.52, N 12.01.
(CDCl3, 75 MHz): δ = 182.6, 154.7, 146.1, 144.45, 134.2, 132.4,
132.2, 128.8, 128.7, 126.4, 121.2, 35.4, 31.8 ppm.
3-(Thiophen-2-yl)propenal (P2): Pale yellow oil (61%). FT-IR: ν =
˜
2424.8 (w), 1665.1 (s), 1608.5 (s), 1421.0 (m), 1225.8 (w), 1113.3
(m), 1044.2 (w), 958.5 (m), 856.4 (m), 702.6 (s) cm–1. 1H NMR
(CDCl3, 300 MHz): δ = 9.60 (d, J = 7.7 Hz, 1 H), 7.58 (d, J =
15.6 Hz, 1 H), 7.49 (d, J = 5.1 Hz, 1 H), 7.36 (d, J = 3.1 Hz, 1 H),
7.10 (dd, J = 5.1, 3.7 Hz, 1 H), 6.49 (dd, J = 15.6, 7.7 Hz, 1 H)
ppm. 13C NMR (CDCl3, 75 MHz): δ = 193.0, 144.6, 139.3, 132.3,
130.5, 128.6, 127.3 ppm.
3-(4-Methoxyphenyl)-1-(thiophen-2-yl)propenone (P4): Yellow crys-
tals (76%). M.p. 84.5–86.0 °C (ref.[18] 87 °C). FT-IR: ν = 1647 (s),
˜
1595 (s), 1512 (s), 1459 (w), 1413 (m), 1355 (w), 1299 (w), 1268
(m), 1229 (m), 1219 (m), 1174 (m), 1065 (w), 1016 (m), 981 (m), 855
(w), 819 (s), 741 (m), 514 (w) cm–1. 1H NMR (CDCl3, 300 MHz): δ
= 7.86 (dd, J = 1.2, 3.7 Hz, 1 H), 7.83 (d, J = 15.5 Hz, 1 H), 7.66
(dd, J = 1.1, 4.9 Hz, 1 H), 7.61 (d, J = 8.7 Hz, 2 H), 7.31 (d, J =
15.5 Hz, 1 H), 7.18 (dd, J = 3.8, 4.9 Hz, 1 H), 6.94 (d, J = 8.8 Hz,
2 H), 3.88 (s, 3 H) ppm. 13C NMR (CDCl3, 75 MHz): δ = 182.5,
162.1, 146.2, 144.3, 134.0, 132.0, 130.7, 128.6, 127.8, 119.6, 114.8,
5-(Pyridin-2-yl)thieno[2,3-c]pyridine (L13): The oxime 16 (1.05 g, 55.8 ppm.
4.95 mmol) was dissolved in decahydronaphthalene (50 mL) and
3-(4-Nitrophenyl)-1-(thiophen-2-yl)propenone (P5): Yellow powder
refluxed. The reaction was monitored by TLC, and, when no start-
ing material was left anymore, the reaction was stopped. The sol-
vent was removed by vacuum distillation, and the remaining black
oil was dissolved in dichloromethane (50 mL), which was extracted
with dilute hydrochloric acid (3ϫ50 mL). The aqueous phase was
made alkaline with Na2CO3 and then extracted with dichlorometh-
ane (3ϫ50 mL), dried with anhydrous MgSO4 and concentrated
to yield a viscous black oil which solidified upon standing. The
black solid was triturated with boiling heptane, which, after evapo-
ration, yielded a yellow low-melting solid. Recrystallization from
methanol afforded pure L13. Product appearance: off-white prisms.
Yield: 0.37 g (35%). M.p. 122–124 °C. 1H NMR (300 MHz,
CDCl3): δ = 9.21 (s, 1 H), 8.83 (d, J = 0.9 Hz, 1 H), 8.70 (ddd, J
= 7.8, 1.7, 0.8 Hz, 1 H), 8.47 (dt, J = 8.0, 0.9 Hz, 1 H), 7.83 (dt, J
= 7.7, 1.8 Hz, 1 H), 7.72 (d, J = 5.4 Hz, 1 H), 7.46 (dd, J = 5.4,
0.6 Hz, 1 H), 7.30 (ddd, J = 7.5, 4.8, 1.2 Hz, 1 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 156.6, 150.6, 149.4, 146.2, 144.1, 137.2,
136.7, 132.6, 124.0, 123.5, 121.4, 115.4 ppm. MS: m/z = 212 [M+].
C12H8N2S (212.27): calcd. C 67.90, H 3.80, N 13.20; found C 67.78,
H 3.86, N 13.11.
(69%). M.p. 225.0–226.0 °C (ref.[19] 220 °C). FT-IR: ν = 1951 (s),
˜
1605 (m), 1513 (s), 1411 (m), 1338 (s), 1290 (w), 1240 (w), 1223
(w), 1107 (w), 1086 (w), 975 (w), 862 (w), 841 (w), 762 (w), 741 (m)
cm–1. 1H NMR ([D6]dmso, 300 MHz): δ = 8.41 (dd, J = 4.2, 0.5 Hz,
1 H), 8.29 (d, J = 8.8 Hz, 2 H), 8.17 (d, J = 8.86 Hz, 2 H), 8.12
(dd, J = 0.5, 4.4 Hz, 1 H), 8.08 (d, J = 15.6 Hz, 1 H), 7.82 (d, J =
15.6 Hz, 1 H), 7.33 (dd, J = 4.3, 4.5 Hz, 1 H) ppm. 13C NMR ([D6]
dmso, 75 MHz): δ = 182.2, 149.0, 146.0, 141.9, 141.2, 137.3, 135.4,
130.8, 130.0, 126.7, 124.8 ppm.
3-(4-tert-Butylphenyl)-1-(5-methylthiophen-2-yl)propenone
(P6):
Yellow needles (69%). M.p. 89.1–89.8 °C. FT-IR: ν = 3070.8 (w),
˜
3052.9 (w), 2960.1 (s), 1647.7 (s), 1599.2 (s), 1514.0 (m), 1458.3 (s),
1385.1 (w), 1365.1 (m), 1333.2 (m), 1244.1 (m), 1222.3 (m), 1073.8
(m), 980.2 (s), 812.8 (s), 555.0 (m) cm–1. 1H NMR (CDCl3,
300 MHz): δ = 7.81 (d, J = 15.6 Hz, 1 H), 7.69 (d, J = 3.8 Hz, 1
H), 7.58 (d, J = 8.4 Hz, 2 H), 7.44 (d, J = 8.4 Hz, 2 H), 7.5 (d, J
= 15.6 Hz, 1 H), 6.85 Hz (dd, J = 3.8, 0.95 Hz, 1 H), 2.57 (d, J =
0.95 Hz, 3 H), 1.34 (s, 9 H) ppm. 13C NMR (CDCl3, 75 MHz): δ
= 181.9, 154.2, 150.1, 143.7, 143.5, 132.5, 132.3, 128.5, 127.1, 126.1,
120.9, 35.1, 31.3, 16.3 ppm.
Representative Procedure for the Preparation of the Propenones P2–
P9
3-(4-Methoxyphenyl)-1-(5-methylthiophen-2-yl)propenone (P7): Yel-
low crystals (92%). M.p. 118.0–119.5 °C. FT-IR: ν = 1639.9 (s),
˜
1570.2 (s), 1513.5 (m), 1453.7 (m), 1310.7 (w), 1297.4 (m), 1261.2
(w), 1238.5 (m), 1223.4 (m), 1176.6 (s), 1071.1 (m), 1029.8 (w),
3-(4-tert-Butylphenyl)-1-(2-thiophen-2-yl)propenone (P3): NaOH
(2.5 g, 62.5 mmol) was dissolved in a mixture of ethanol (30 mL)
and water (20 mL) and well cooled with ice. 4-tert-Butylbenzalde-
hyde (4.87 g, 30 mmol) was added in 5 portions over 5 min, and
then 2-acetylthiophene (3.80 g, 30 mmol) was added dropwise over
20 min to the reaction mixture. The mixture was protected from
light and stirred vigorously for 48 h, during which time the tem-
perature was allowed to rise to room temperature. The product was
extracted with dichloromethane (3ϫ50 mL), and the collected or-
ganic phases were dried with MgSO4 before the solvent was evapo-
rated. The residue was recrystallized from methanol to give the
pure product. Product appearance: yellow crystals. Yield: 5.84 g
1
986.1 (m), 830.9 (w), 802.0 (s), 719.6 (w) cm–1. H NMR (CDCl3,
300 MHz): δ = 7.79 (d, J = 15.5 Hz, 1 H), 7.67 (d, J = 3.6 Hz, 1
H), 7.59 (d, J = 8.7 Hz, 2 H), 7.26 (d, J = 15.5 Hz, 1 H), 6.94 (d,
J = 8.7 Hz, 2 H), 6.85 (dd, J = 2.8, 1.0 Hz, 1 H), 3.85 (s, 3 H), 2.59
(s, 3 H) ppm. 13C NMR (CDCl3, 75 MHz): δ = 181.9, 161.8, 149.9,
143.4, 132.3, 130.4, 127.8, 127.1, 119.4, 114.6, 55.6, 16.3 ppm.
1-(5-Methylthiophen-2-yl)-3-(4-nitrophenyl)propenone (P8): Orange
powder (92%). M.p. 191.6–197.1 °C. FT-IR: ν = 2155.9 (w), 1643.9
˜
(m), 1588.0 (m), 1509.4 (m), 1455.5 (m), 1336.8 (s), 1236.6 (m),
985.0 (m), 806.3 (s), 667.7 (s) cm–1. 1H NMR ([D6]dmso,
300 MHz): δ = 8.30 (d, J = 8.7 Hz, 2 H), 8.23 (d, J = 3.9 Hz, 1 H),
(72%). M.p. 79.3–80.0 °C. FT-IR: ν = 3087 (m), 2961 (s), 1644 (s),
˜
1583 (s), 1558 (m), 1516 (m), 1456 (w), 1417 (s), 1354 (s) cm–1. H 8.14 (d, J = 8.7 Hz, 2 H), 8.03 (d, J = 15.7 Hz, 1 H), 7.77 (d, J =
1
NMR (CDCl3, 300 MHz): δ = 7.87 (dd, J = 1.2, 3.9 Hz, 1 H), 7.85
15.7 Hz, 1 H), 7.05 (d, J = 3.0 Hz, 1 H), 2.55 (s, 3 H) ppm. 13C
(d, J = 15.5 Hz, 1 H), 7.68 (dd, J = 1.1, 5.0 Hz, 1 H), 7.60 (d, J = NMR ([D6]dmso, 75 MHz): δ = 180.9, 148.1, 143.2, 141.2, 140.0,
8.4 Hz, 2 H), 7.45 (d, J = 8.4 Hz, 2 H), 7.39 (d, J = 15.6 Hz, 1 H), 135.3, 134.7, 129.9, 128.0, 127.3, 124.0, 16.0 ppm.
Eur. J. Inorg. Chem. 2008, 4101–4110
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4109

S. J. Dunne et al.
FULL PAPER
[4]
[5]
A. C. Benniston, A. Harriman, Chem. Soc. Rev. 2006, 35, 169–
1-(5-Methylthiophen-2-yl)-3-(thiophen-2-yl)propenone (P9): Yellow
179.
crystals (71%). M.p. 108.3–110.0 °C. FT-IR: ν = 1637.2 (m), 1577.8
˜
R. O. Steen, L. J. Nurkkala, S. J. Angus-Dunne, C. X. Schmitt,
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(m), 1454.4 (m), 1277.7 (m), 1212.8 (m), 1065.0 (m), 1039.7 (m),
1
957.2 (s), 863.6 (m), 827.2 (m), 796.0 (s), 714.0 (s) cm–1. H NMR
(CDCl3, 300 MHz): δ = 7.93 (d, J = 15.3 Hz, 1 H), 7.66 (d, J =
3.9 Hz, 1 H), 7.41 (d, J = 5.1 Hz, 1 H), 7.34 (d, J = 3.3 Hz, 1 H),
7.17 (d, J = 15.3 Hz, 1 H), 7.09 (dd, J = 5.1, 3.6 Hz, 1 H), 6.85 (d,
J = 4.5 Hz, 1 H), 2.55 (s, 3 H) ppm. 13C NMR (CDCl3, 75 MHz):
δ = 181.6, 150.6, 143.8, 140.7, 136.2, 132.8, 132.4, 129.0, 128.7,
127.4, 120.7, 16.6 ppm.
[6]
[7]
[8]
[9]
Supporting Information (see footnote on the first page of this arti-
cle): Reaction schemes for ligands L10–L12. Cyclic voltammog-
rams for complex C1–C13. 1H NMR spectra of ligands L1–L13. 1H
NMR and COSY spectra of complexes C1–C13. UV/Vis spectra of
complexes C1–C13.
[10]
[11]
[12]
[13]
Acknowledgments
The authors would like to thank Fakultetsnämnden (Naturveten-
skap och teknik), Mälardalen University, for their generous and
continued support of this project. R. O. S. would like to thank the
Dentist Gustav Dahl Memorial Fund for generous support. The
authors also would like to thank Mr. George Blazak at the Univer-
sity of Queensland, Australia, for performing elemental analysis
and Dr. Conor Brennan at the University of Basel, Switzerland,
for performing MALDI-TOF analysis.
[14]
[15]
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[1] P. Bäuerle in Electronic Materials: The Oligomer Approach
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Received: May 6, 2008
Published Online: August 4, 2008
4110
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Eur. J. Inorg. Chem. 2008, 4101–4110