New ruthenium Bis(terpyridine) methanofullerene and pyrrolidinofullerene complexes: Synthesis and electrochemical and photophysical properties

Article abstract of DOI:10.1021/ic502431x

A series of terpyridine (tpy) methanofullerene and pyrrolidinofullerene dyads linked via p-phenylene or p-phenyleneethynylenephenylene (PEP) units is presented. The coordination to ruthenium(II) yields donor-bridge-acceptor assemblies with different lengt

Full text of DOI:10.1021/ic502431x

Article
pubs.acs.org/IC
New Ruthenium Bis(terpyridine) Methanofullerene and
Pyrrolidinofullerene Complexes: Synthesis and Electrochemical and
Photophysical Properties
Kevin Barthelmes,†,‡,⊥ Joachim Kubel,§,∥,⊥ Andreas Winter,†,‡ Maria Wachtler,§,∥ Christian Friebe,†,‡
̈
̈
Benjamin Dietzek,*,‡,§,∥ and Ulrich S. Schubert*,†,‡
†Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstraße 10, 07743 Jena,
Germany
‡Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743 Jena, Germany
§Institute of Physical Chemistry (IPC) and Abbe Center of Photonics, Friedrich Schiller University Jena, Helmholtzweg 4, 07743
Jena, Germany
∥Leibniz Institute of Photonic Technology e.V. (IPHT), Albert-Einstein-Straße 9, 07745 Jena, Germany
S
* Supporting Information
ABSTRACT: A series of terpyridine (tpy) methanofullerene
and pyrrolidinofullerene dyads linked via p-phenylene or p-
phenyleneethynylenephenylene (PEP) units is presented. The
coordination to ruthenium(II) yields donor−bridge−acceptor
assemblies with different lengths. Cyclic voltammetry and
UV−vis and luminescence spectroscopy are applied to study
the electronic interactions between the active moieties. It is
shown that, upon light excitation of the ruthenium(II)-based
1MLCT transition, the formed 3MLCT state is readily
quenched in the presence of C60. The photoinduced dynamics
have been studied by transient absorption spectroscopy, which
3
reveals fast depopulation of the MLCT (73−406 ps). As a
3
consequence, energy transfer occurs, populating a long-lived triplet state, which could be assigned to the C60* state.
electronic communication between the donor and acceptor
parts. Several wirelike bridging units have been studied in
recent years, including π-conjugated oligomers consisting of
phenyleneethynylenes,16,26 phenylenevinylenes,31 and fluorene
units13,17 and nonconjugated oligomers consisting of glycol,32,33
cyclohexane,28 and peptide units.34
In this work, we report the investigation of new donor−
acceptor systems, in which Ru(II) bis(terpyridine) complexes
are connected to C60. The series contains short phenyl-bridged
as well as longer octyloxy-substituted phenyleneethynylenephe-
nylene-bridged systems (Figure 1). These were chosen for their
rigidity and π conjugation with low attenuation factors β,35
which provide pathways for an efficient charge transport.
Photophysical studies of these bridging units, especially in
ruthenium(II) bis(terpyridine) complexes, have been thor-
oughly described by us previously.36−39 This latter concept was
further extended for the functionalization on C60 by cyclo-
addition reactions of 1,3-dipolar reagents with one [6,6]-double
bond to form pyrrolidine or cyclopropane monoadducts.
INTRODUCTION
■
The development of artificial devices that mimic light-triggered
reactions in natural photosynthetic systems, which are based on
the fundamental processes of energy and/or electron transfer,
has become an attractive field in modern science and
technology.1−10 A general challenge in the molecular design
of donor−bridge−acceptor systems is the generation of long-
lived charge-separated (CS) states.8,11,12 Fullerenes, in
particular C60, have high electron affinities, which make them
favorable systems regarding their electron-accepting ability.
Photoinduced electron transfer and energy transfer in (macro)-
molecular assemblies containing donors, such as ferrocene,13,14
porphyrin,15 tetrathiafulvalene,16,17 and others,18,19 which are
covalently linked to fullerene, were extensively studied; their
electrochemical and photophysical properties are of particular
interest.20,21 Ruthenium(II) polypyridyl complexes as donors
are promising materials due to their intense light absorption in
the visible range and extended excited-state lifetimes.22−24
Previous studies on Ru(II)−polypyridine−C60 assemblies
showed that both electron and energy transfer is possible in
such systems: the intermediate CS state may undergo charge
́
Martın and co-workers could show that cyclopropane adducts
3
recombination to the final lower lying triplet excited C60*
Received: October 7, 2014
state.25−30 Furthermore, the linker plays a crucial role in the
© XXXX American Chemical Society
A
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Figure 1. Schematic representations of the Ru(II)−bis(terpyridine)−C60 assemblies 1 and 2 as well as reference compounds 3 studied in this work,
along with a numbering scheme for the complexes and precursors.
a
Scheme 1. Schematic Representation of the Synthetic Route
a
Legend: (a) CrO3, H2SO4, acetic anhydride, room temperature, 16 h; (b) (i) 2-acetylpyridine, NaOH, grinding, room temperature, 30 min, (ii)
ammonia (aqueous), EtOH, room temperature, 48 h; (c) benzoyl chloride, AlCl3, dichloromethane, room temperature, 16 h; (d) 1-bromooctane,
KOH, DMSO, room temperature, 22 h; (e) 4′-(4-ethynylphenyl)-2,2′:6′,2″-terpyridine, [Pd(PPh3)4], CuI, NEt3, THF, 60 °C, 48−72 h; (f)
[Ru(tpy)Cl3], AgBF4, acetone, 70 °C, 2 h; (g) (i) DMF, 160 °C, 3 h, (ii) excess NH4PF6.
generally enhance the electronic communication between
fluorene and C60 in comparison to pyrrolidine rings.40 In
addition to the mononuclear complexes 1a,b and 2a,b, we
report the symmetrical dinuclear complex 1c, bearing two
B
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a
Scheme 2. Schematic Representation of the Synthetic Route toward the Studied Ru(II) Complexes 1a−c and 2a,b
a
Legend: (a) C60, N-methylglycine, toluene, 120 °C, 24 h; (b) tosylhydrazine, tosylic acid, THF, 80 °C, 2−5 days; (c) NaOCH3, pyridine, room
temperature, 20 min; (d) C60, o-dichlorobenzene, 180 °C, 24 h; (e) [Ru(tpy)(MeCN)3](PF6)2, DMF, 140 °C, microwave, 30 min.
a
Table 1. Electrochemical Data Obtained by Cyclic Voltammetry
E1/2,ox(Ru and/or irr P)/V
E1/2,red(C60,1)/V
E1/2,red(C60,2)/V
E1/2,red(tpy,1)/V
E1/2,red(C60,3 and/or tpy,2)/V
b
C60
8a
−1.00
−1.11
−1.14
−1.11
−1.15
−1.13
−1.09
−1.12
−1.08
−1.11
−1.14
−1.39
−1.49
−1.52
−1.48
−1.51
−1.53
−1.45
−1.49
−1.46
−1.50
−1.50
−1.86
−1.98
−2.02
−1.98
−2.03
e
8b
8c
c
10a
10b
1a
+0.99
c
+0.92
+0.91
+0.89
+0.92
−1.68
−1.65
−1.66
−1.65
−1.63
−1.63
−1.59
e
1b
1c
e
e
d
2a
+0.90
e
d
2b
3a
+0.90
e
+0.91
+0.89
−1.95
−1.95
3b
a
Conditions: potentials referenced to Fc+/Fc; scan rate 200 mV s−1; glassy-carbon-disk working electrode; AgCl/Ag reference electrode; Pt-rod
counter electrode; 0.1 M Bu4NPF6 in dichloromethane. Taken from ref 68. Irreversible process. The peak potential is shown. Two processes.
Not detectable.
b
c
d
e
bis(terpyridine) ruthenium(II) centers and one C60 unit. The
major aim of these studies is to figure out the influence of the
length of the linker as well as the way the linker is connected to
the C60 on the electrochemical and photophysical properties of
the new compounds.
solvent-free conditions in 30 min. When the bridge length was
increased, octyloxy chains were introduced to improve the
solubility. For this purpose, the starting material 4b was
synthesized according to literature procedures.43 Compound 5b
was prepared by Friedel−Crafts acylation with benzoyl chloride
(during the reaction, one octyl group was cleaved off and
reintroduced by alkylation). A Sonogashira cross-coupling
reaction with 4′-(4-ethynylphenyl)-2,2′:6′,2″-terpyridine was
applied to prepare 6b.44 The reference ligand 11b was
synthesized in good yield by an analogous route. The respective
methanofullerenes 8a,b as well as the symmetrical bis-
(terpyridine)−C60 compound 8c were obtained in a three-
step reaction. First, the terpyridine-functionalized benzophe-
nones 6a−c were reacted with tosylhydrazine and catalytic
amounts of tosylic acid to yield the desired tosyl hydrazone
derivatives 7a−c. Elimination of the tosyl group with sodium
methoxide by a mechanism analogous to the Bamford−Stevens
RESULTS AND DISCUSSION
■
Synthesis. The synthetic routes are depicted in Schemes 1
and 2. The benzophenone building blocks with rigid phenyl
units as spacers were synthesized in a two-step reaction.
Starting from para-substituted methylbenzophenones 4a,c, the
oxidation with chromium(VI) oxide yielded the desired mono-
and bis-formylated41 compounds 5a,c, respectively. The
terpyridine fragments 6a and 6c were prepared according to
a modified Krohnke-type procedure reported previously.42 By
̈
grinding the starting material 5a or 5c, 2-acetylpyridine, and
NaOH, the diketone intermediate can be prepared under these
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reaction yielded in situ the 1,3-dipolar diazo compounds, which
reacted with C60 to form pyrazolinofullerene derivates as
intermediates.45,46 Further thermal treatment eliminated
molecular nitrogen, and the desired methanofullerenes were
obtained in low to moderate yields. Recently, we reported the
synthesis of the aldehyde-functionalized 2,2′:6′,2″-terpyridines
9a,b used in this study.47,48 Pyrrolidinofullerenes 10a,b were
synthesized by the 1,3-dipolar cycloaddition of azomethine
ylides, derived from 9a,b, respectively, and N-methylglycine to
C60 in an optimized 1:10:4 ratio.49 The compounds were
obtained in low to good yields, respectively, mainly due to the
enhanced solubility of 9b. All fullerene ligands were purified by
column chromatography using neutral alumina and n-hexane/
toluene mixtures to remove and recover the unreacted C60.
[Ru(tpy)(MeCN)3](PF6)2 was used as a precursor to obtain
the corresponding heteroleptic ruthenium(II) complexes 1a−c
and 2a,b in moderate yields. The reaction was performed under
microwave irradiation for 30 min at 140 °C in DMF. Since
column chromatography using silica with potassium nitrate was
not applicable for these C60-containing complexes, the dark red
complexes were purified by treatment of a concentrated
acetonitrile solution with diethyl ether vapor to force slow
precipitation. So far, we have not been able to obtain single
crystals suitable for X-ray structure analysis. The reference
ligands 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine (ttpy) and
11b were coordinated to ruthenium by standard complexation
procedures in ethanol50,51 or DMF.52 All complexes exhibited a
good solubility in polar solvents, such as acetonitrile, and have
been characterized by NMR spectroscopy, mass spectrometry,
and elemental analysis.
attributed to the electrochemical retrocycloaddition of the
pyrrolidinofullerene fragment.53 There is no significant differ-
ence for the Ru(III)/Ru(II) redox potentials within the series
(and also in comparison to the reference complexes 3a,b),
indicating the negligible influence of the ligand sphere on the
energy of the highest occupied molecular orbital. Within the
accessible potential window, all fullerene-containing com-
pounds of the series feature three reversible C60-based
reduction waves of similar redox potentials at around −1.1,
−1.5, and −2.0 V. The half-wave potentials are shifted
cathodically in comparison to pristine C60. This can be
attributed to the attached pyrrolidine and cyclopropane units,
causing a disruption of π conjugation and a decreased electron
affinity of C60.54 As reported elsewhere,40 the values for the C60
reductions are slightly cathodically shifted (around 20 mV) on
comparison of pyrrolidine to cyclopropane rings attached to
C60. Accordingly, electron delocalization is more efficient in the
methanofullerene compounds. Another trend that holds true
at least for the first C60-based reductionis the cathodic shift
on changing to larger bridge lengths. The third reduction wave
at around −1.65 V of 1a−c and 2a,b is attributed to the first
reduction of the terpyridine unit. The assignment is proven by
comparison of the dinuclear complex 1c to the parent
mononuclear ruthenium complex 1a. Apparently, the dinuclear
complex shows similar values for the half-wave potentials but
increased currents for the ruthenium- and terpyridine-related
redox couples, while the C60-based peak currents stay nearly
constant (see Figure S3 in the Supporting Information). The
second reduction of the terpyridine unit is in the same range as
the third C60-based reduction. According to the model
complexes 3a,b, the redox potential of the second terpyridine
reduction is at ca. −1.95 V (see Figure S2 in the Supporting
Information). In the methanofullerene ruthenium(II) com-
plexes 1a−c there is another irreversible process around −1.98
V (see Figure S4 in the Supporting Information). As is known
from the literature, this process has to be assigned to the
electrochemical retrocycloaddition of Bingel adducts.55 How-
ever, this process can only be observed for the investigated
complexes and is absent for the ligands 8a−c.
Electrochemical Properties. The redox behavior of the
complexes 1a−c and 2a,b, the ligands 8a−c and 10a,b, and the
references 3a,b was studied by cyclic voltammetry. The data are
summarized in Table 1, and representative spectra are depicted
in Figure 2. The electrochemical measurements were
Photophysical Properties. The UV−vis absorption data
are summarized in Table 2. A comparison of the UV−vis
absorption spectra of C60, 2b, and 3b, as shown in Figure 3,
reveals that the spectrum of 2b can be regarded as a
superposition of the spectra of C60 and 3b. In agreement
a
Table 2. UV−Vis Absorption Data
b
λabs/nm (ε/103 M−1 cm−1
)
C60
8a
405 (2.7), 329 (50.9), 258 (189.6)
430 (2.6), 327 (46.0), 259 (150.0)
430 (4.0), 328 (78.2), 259 (157.5)
8b
8c
430 (3.1), 323 (61.4), 276 (sh, 172.9), 259 (195.5)
430 (6.2), 317 (sh, 45.0), 271 (sh, 107.0), 256 (123.8)
430 (10.3), 311 (87.4), 269 (sh, 126.5) 255 (149.0)
484 (25.1), 327 (sh, 78.1), 310 (97.7), 270 (112.6)
487 (31.6), 327 (sh, 83.9), 311 (107.2), 273 (105.4)
484 (47.0), 326 (sh, 131.5), 310 (174.5), 273 (159.7)
485 (22.8), 327 (sh, 59.3), 309 (83.7), 273 (85.8)
488 (35.8), 327 (sh, 95.0), 311 (116.8), 270 (113.9)
484 (23.4), 327 (sh, 43.4), 309 (77.5), 274 (49.3)
487 (35.4), 326 (69.2), 310 (95.6), 274 (52.3)
10a
10b
1a
Figure 2. Cyclic voltammograms of phenyl-bridged methano- and
pyrrolidinofullerene ligands and complexes in dichloromethane (with
0.1 M Bu4NPF6).
1b
1c
performed in dichloromethane at room temperature with
Bu4NPF6 as the conducting salt. For complexes 1a−c and 2a,b,
the first oxidation wave at ca. 0.9 V arises from the reversible
Ru(III)/Ru(II) redox couple. In addition, for the ligands 10a,b,
a second, irreversible oxidation, which is overlaid by the
ruthenium oxidation in 2a,b, was observed. This process is
2a
2b
3a
3b
a
b
Measured in dichloromethane at 20 °C. sh = shoulder.
D
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Supporting Information). Additionally, the fullerene-based
fluorescence at ca. 700 nm is only weakly pronounced.13 The
initially weak Ru(II)-based emission at room temperature of
the reference complexes (3a, λmax = 627 nm; 3b, λmax = 645
nm) is almost fully quenched in complexes 1a−c and 2a,b
(Figure 4). The quenching indicates an electronic interaction
3
between the MLCT state and the fullerene unit, as detailed
below.
Photoinduced Dynamics. Formation of the Long-Lived
Excited State. The photoinduced dynamics occurring after
1
excitation of the MLCT transition (λexc = 520 nm) were
investigated using transient absorption (TA) spectroscopy in
order to clarify the quenching mechanism. To provide
consistency with the steady-state data, we will focus on the
TA experiments performed in dichloromethane. Figure 5
contains transient absorption data for 2b and for the C60-free
complex 3b, as reference. The transient absorption spectra
recorded for 3b (Figure 5A) match those of typical RuII
polypyridine complexes featuring ground-state bleach (GSB)
Figure 3. UV−vis absorption spectra of the long bridged
pyrrolidinofullerene ligand and complexes measured in dichloro-
methane.
with the electrochemical measurements, there is no evidence
for an electronic interaction between the Ru(II) center and the
fullerene unit in the ground state. The spectral properties are
similar throughout the series: while intense absorption bands
between 250 and 350 nm are based on π−π* transitions within
the fullerene, phenyl, and terpyridine groups, absorption bands
in the region around 485 nm are related to Ru(II)-based metal-
to-ligand charge-transfer (MLCT) transitions.56 With an
increased bridge length in compounds 1b and 2b, the
additional phenylene and ethynylene groups cause a slight
bathochromic shift of the π−π* transitions. An analogous
behavior is observed for the MLCT transition (shift of around 3
nm), in concert with increases in the molar extinction
coefficients. The fullerene ligands 8a−c and 10a,b possess a
sharp absorption band at around 430 nm, which is bath-
ochromically shifted in comparison to pristine C60 (405 nm).
This transition is characteristic of closed-[6,6] fullerene
monoadducts.57,58 In the complexes, this transition is only
weakly defined, because it is overlaid by the tail of the strong
MLCT transition. The emission properties of 8a−c and 10a,b
were studied in dichloromethane and compared to the
reference systems ttpy and 11b. Upon excitation of the π−π*
transition (λex = 315 or 325 nm), there is a strong quenching of
the spacer- and terpyridine-based fluorescence by a factor of ca.
200 when the C60 unit is attached (for details, see the
1
in the region of the MLCT absorption band and excited-state
absorption (ESA) above 550 nm. The electronic delocalization
3
of the MLCT state over the extended ligand is apparent: the
ESA maximum of 3a, where 3MLCT delocalization is limited to
the ttpy ligand, is at ca. 560 nm in acetonitrile (see the
Supporting Information). However, for 3b the ESA maximum
is located at ca. 690 nm, clearly indicating the presence of an
extended π system.59 This was also noted for related
methoxyphenyl-substituted [Ru(bpy)3]2+ derivatives.26 The
kinetic traces (Figure 5B) illustrate that the signal decay is
not completely resolved, at least within the time scale of the
experiment. However, this decay likely corresponds to the
3
decay of the MLCT (see below).
The quantitative interpretation of the TA data is based on
global multiexponential fits corresponding to a kinetic scheme
involving consecutive first-order reactions (details are given in
the Experimental Section). In the case of 3b, four kinetic
components are used to fit the data. The decay-associated
spectra (DAS) and the corresponding characteristic time
constants are given in Figure 6. The DAS (τ4 = 1.6 ns)
features a much higher amplitude than the other DAS: i.e., it
plays a dominant role in the photoinduced dynamics of 3b. The
DAS (τ4) reflects the shape of the TA spectra recorded at long
delay times, indicating that τ4 describes the decay of the
Figure 4. (A) Normalized emission spectra (λex = 483 or 488 nm) of the reference complexes 3a,b measured in dichloromethane at room
temperature. Asterisks mark the scattered excitation light. (B) Emission spectra of isoabsorbing solutions at 487 nm of 3b and 2b in dichloromethane
together with the signal obtained from the pure solvent. The right scale shows a magnification of the spectral region containing 3MLCT
phosphorescence and C60 fluorescence (solvent and spectra recorded at 470 nm are omitted for clarity).
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Figure 5. Transient absorption spectra (A, C) at selected delay times between 0.2 and 1.8 ns (from red to black) and selected kinetic traces (B, D)
with corresponding fit curves: 488 nm (black squares), 560 nm (red circles), 620 nm (blue triangles), and 690 nm (cyan stars) for 3b (A, B) and 2b
(C, D).
extended terpyridine ligand: i.e., excited-state torsional motion
around the pyridine−phenyl bond.63 Planarization causes an
increase in the ESA in the visible part of the spectrum due to an
enhanced π conjugation of the ligand. DFT calculations on 3b
3
suggest a strong mixing of MLCT states with ligand-centered
orbitals (see the Supporting Information) leading to delocalized
3
3
states with different amounts of MLCT and LC character.
Therefore, τ3 (238 ps) has to be assigned to an equilibration
between close-lying, mixed triplet states.39,64
Dyad 2b shows transient absorption features similar to those
observed for 3b at early delay times (see Figure 5A,B). Both the
spectra and the kinetic traces are similar up to 30 ps. Later, in
2b a more pronounced decay is observed, which is not
complete: i.e., the kinetic traces reach a plateau after ca. 1 ns.
The transient absorption spectra at delay times >1.5 ns are
positive over the entire spectral range probed in our
experiment, including a rise toward 700 nm. Thus, the
nanosecond dynamics of 2b are clearly different from those
of 3b, leading to the formation of a long-lived species unique
for the dyad. The global fit routine produces three kinetic
components and an offset corresponding to the spectrum of the
long-lived species formed. The nature of this species will be
discussed in conjunction with results of nanosecond transient
absorption experiments. The sub-picosecond component (τ1 =
0.3 ps) is similar to the fastest process observed for 3b and can
be rationalized equivalently. The picosecond processes, i.e. the
processes associated with τ2 and τ3, are accelerated in 2b in
comparison to those in 3b. In detail, a process with τ2 = 3.6 ps
shows spectral characteristics similar to those of the
equilibration process (τ3) observed in 3b. The time constant
τ3 = 245 ps of 2b is identical with the value of τ3 of 3b (238 ps),
but the corresponding DAS (τ3) in the case of 2b is basically
identical with the DAS (τ4) of 3b describing the overall decay,
as discussed above. Therefore, the depopulation of the 3MLCT
Figure 6. Global fit results in terms of decay-associated spectra for 3b
(A) and 2b (B). The characteristic time constants are given in the
legends.
3MLCT and, thus, the overall decay to the ground state. This is
also supported by the emission decay time of 3b (2.3 ns in
acetonitrile), determined by time-correlated single-photon
counting (see the Supporting Information). This value can be
compared to the 1.6 ns decay time determined in the TA
experiments, as in the latter decay time there is a relatively large
uncertainty due to the limited delay time range (1.8 ns)
accessible in our experimental setup.
The fastest component (τ1 = 0.5 ps) is assigned to solvent
relaxation and vibrational energy dissipation60,61 and causes an
increase of the ESA between 550 and 700 nm. Generally, the
picosecond components (τ2 = 8.2 ps, τ3 = 238 ps) can be
attributed to the presence of the organic chromophore attached
at the 4′-position of the tpy unit:62 Here, the process associated
with τ2 is assigned to photoinduced planarization of the
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Figure 7. Nanosecond transient absorption data of 2b in dichloromethane: (A) absorption spectra of the long-lived species constructed from
integrated intervals of nanosecond transient absorption kinetics (blue solid squares) with the offset component from the femtosecond TA data
(black hollow symbols) for comparison; (B) decay of the positive absorption at λ = 700 nm after photoexcitation of 2b at 520 nm in aerated (solid
stars) and deaerated (hollow spheres) solutions with respective fit curves for τ = 800 ns (red curve) and τ = 13 μs (blue curve).
(or rather a mixed 3MLCT/π−π*) state occurs very quickly for
2b with the same time constant that was assigned to excited-
state equilibration in 3b. Given the fact that the long-lived state
in 2b is due to the fullerene unit, the process that deactivates
the MLCT is the same process that populates the long-lived
state (see below).
acetonitrile in comparison to dichloromethane, the data reveal
almost identical spectral and temporal characteristics (see the
Supporting Information). In particular, no significantly different
time constants were found, ruling out the possibility that charge
separation is contributing to the photophysics of 2b. Similar
observations are made for 2a, i.e. the short-bridged analogue, as
well as the methano-fullerene dyads 1a,b, as the photoinduced
dynamics probed in transient absorption experiments are rather
similar for all of these compounds (see the Supporting
Information). This holds true also for the dinuclear complex 1c.
Nevertheless, the quenching kinetics are not identical for the
compounds at hand. In fact, the rate constant for energy
transfer measured in acetonitrile (corresponding to the process
causing the 3MLCT absorption characteristics to vanish)
depends on both the linker type and the size of the bridge
between terpyridine and fullerene moieties (see Figure 8). The
3
Nature of the Long-Lived Excited State. Nanosecond
transient absorption experiments on 2b (Figure 7) were
conducted to detail the nature of the long-lived state: kinetic
traces for the nano- to microsecond decay were recorded for
selected wavelengths. From these curves, nanosecond transient
absorption spectra were constructed. A broad absorption peak
is found with a maximum at ca. 700 nm and steep flanks on
both the high- and low-energy sides. A shoulder is observed at
ca. 800 nm, and there are hints toward a rise at wavelengths
shorter than 450 nm. The offset component determined from
the femtosecond transient absorption data is in good agreement
with the nanosecond transient absorption spectrum. Further-
more, the nanosecond spectrum coincides with the known
31
3
absorption features of the C60* state, in particular the
maximum at around 700 nm and the long-wavelength shoulder.
Additional support for the assignment of the long-lived state as
3C60* is based on oxygen-quenching experiments: Triplet states
of organic molecules are prone to undergo quenching reactions
with triplet oxygen, strongly reducing the excited-state
lifetime.65 From a comparison of kinetic traces of the ESA
decay at 700 nm recorded in the presence and absence of
oxygen (Figure 7B), it is taken that the lifetime significantly
increases in the absence of oxygen, indicative of a triplet state.
The lifetimes of 800 ns and 13 μs with and without oxygen,
31
3
respectively, are consistent with literature reports on C603*.
Figure 8. Schematic representation of the distance and linker
Three possible quenching mechanisms leading to the C60*
dependence of the energy transfer (3MLCT depopulation) rate.
state were discussed in the literature,26 of which resonant
triplet−triplet energy transfer (Forster-type) is unlikely to
̈
3
happen due to the weak acceptor absorption. Other possibilities
are charge separation, i.e. a transport of the negative charge
located on the ligand toward the fullerene after 1MLCT
excitation followed by a fast recombination, and Dexter-type
energy transfer. The former would, however, yield a reduced
C60 species, which would absorb in the NIR region at around
1100 nm.31
fastest MLCT deactivation (73 ps) is observed for the short-
bridged pyrrolidinofullerene dyad 2a. In 1a the energy transfer
is somewhat slower (93 ps), possibly due to the different angle
of the complex fragment with respect to the fullerene surface.
The larger bridge, increasing the donor−acceptor distance in
the assemblies 1b and 2b, causes a significant prolongation of
the energy transfer time.
The fact that 3b and 2b possess strongly delocalized 3MLCT
states involving orbitals of the organic chomophore indicates
that orbital overlap with the fullerene unit might favor rapid
Dexter-type energy transfer in the Ru(II)−C60 dyads. As soon
as the extended ligand is planarized and electronic communi-
Solvent-polarity-dependent TA spectroscopy was performed
to yield additional insight into the photoinduced processes and
validate the absence of a photoinduced charge-transfer reaction.
Therefore, additional TA measurements on 2b and 3b were
performed in acetonitrile: despite the higher polarity of
G
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Inorganic Chemistry
Article
spectra were recorded using higher absorbances (ca. 0.2 in the
maximum of the MLCT band). Cyclic voltammetry measurements
cation between the metal center and the orbitals of the organic
chromophore is enhanced, there is close spatial proximity with
orbitals of the fullerene acceptor and an efficient deactivation
1
were performed on a Metrohm Autolab PGSTAT30 potentiostat with
a standard three-electrode configuration using a glassy-carbon-disk
working electrode, a platinum-rod auxiliary electrode, and a AgCl/Ag
reference electrode; a scan rate of 200 mV s−1 was applied. The
experiments were carried out in deaerated solvents (spectroscopy
grade) containing 0.1 M Bu4NPF6 salt. At the end of each
measurement, ferrocene was added as an internal standard.
3
pathway of the MLCT is accessible.
CONCLUSION
■
A series of mono- and dinuclear ruthenium(II) bis(terpyridine)
methanofullerene and pyrrolidinofullerene assemblies con-
nected with phenylene and phenyleneethynylenphenylene
units was synthesized. The key step of the synthetic route
was the cycloaddition reaction of the terpyridine building
blocks onto the fullerene unit. The complexes were compared
to related reference compounds with regard to their electro-
chemical and photophysical properties. The methanofullerene
compounds feature better electronic communication between
the active units in comparison to pyrrolidinofullerenes,
indicated by a small anodic shift of the C60-based redox
potentials. The ground-state absorption spectra are mainly a
superposition of the individual moieties’ characteristics,
indicating weak interaction between the redox-active subunits
in the ground state. However, steady-state emission spectros-
copy revealed a strong interaction in the excited state: namely,
by quenching of the ligand-based fluorescence and Ru(II)-
based phosphorescence. Photoexcitation of the Ru(II)-based
1MLCT transition results in a fast population of the lowest-
lying triplet C60 state. A distance and linker dependence of the
energy transfer rate was found. We believe that the photo-
physical and electrochemical properties of the presented
complexes have a high potential in formation of light-induced
charge-separated states for artificial photosynthetic devices, in
particular when the assemblies are extended from dyads to
triads by incorporation of lateral organic or organometallic
donor entities. This is the topic of ongoing research.
Time-Resolved Spectroscopy. The femtosecond transient
absorption measurements (λexc 520 nm) were performed on two
different setups. Each setup is based on an amplified Ti:sapphire
oscillator (800 nm, 1 kHz). One setup produces pulses of 35 fs at 3.5
mJ (Legend-Elite, Coherent Inc., used for measurements in
acetonitrile) and the other setup 100 fs at 950 μJ (Libra, Coherent
Inc., used for measurements in dichloromethane). Appropriate beam
splitters split the pulses to attenuate the intensity to pump: in case of
the former setup, a collinear optical-parametric amplifier (TOPAS-C,
LightConversion Ltd.) with 1.35 W or, for the latter setup, a
noncollinear optical-parametric amplifier (TOPASwhite, Lightconver-
ison Ltd.) with 0.5 W. The pump pulses delayed in time with respect
to the probe pulses by means of an optical delay line, and their
polarization was rotated by 54.7° (magic angle) with respect to the
probe beam by using a Berek compensator. For both setups white light
was used as the probe, which was generated by focusing a minor
fraction of the amplifier output into a sapphire plate. The probe beam
is focused and recollimated using 50 cm (20 cm) spherical mirrors,
while the focus of the pump beam is behind the sample in order to
obtain a homogeneously excited sample volume. The pump pulse is
blocked after the sample, while the probe pulse is sent to a double-
stripe diode-array detection system (Pascher Instruments AB) together
with the reference pulse. The pump pulse energy was typically adjusted
to 1 μJ while the integrated probe intensity was a few hundred
nanojoules. The sample solution (OD typically ca. 0.2 at the excitation
wavelength) was kept in a 1 mm quartz cuvette. Prior to data analysis,
the experimental differential absorption data was chirp corrected and
afterward fitted globally.
The excited-state lifetimes were determined using a nanosecond
transient absorption setup. Nanosecond pump pulses at 520 nm were
delivered by a Continuum Surelite OPO Plus pumped by a
Continuum Surelite Nd:YAG laser (pulse duration 5 ns; pulse to
pulse repetition rate 10 Hz). A 75 W xenon arc lamp provided the
probe light. Spherical concave mirrors were used to focus the probe
light into the sample and to refocus the light on the entrance slit of a
monochromator (Acton, Princeton Instruments). The probe light was
detected by a Hamamatsu R928 photomultiplier tube mounted on a
five-stage base at the monochromator exit slit, and the signal was
processed by a commercially available detection system (Pascher
Instruments AB). Some measurements were performed in oxygen-free
solutions produced by performing several freeze−pump−thaw cycles.
All measurements were performed in 1 cm fluorescence cuvettes,
allowing a 90° angle between pump and probe beam.
4-Formylbenzophenone (5a). The oxidation of the terminal
methyl group was performed according to a related literature
procedure.41 Concentrated sulfuric acid (6 mL, 113 mmol) was
added dropwise to a stirred solution of 4-methylbenzophenone (4a; 3
g, 15.29 mmol) in acetic anhydride (30 mL) at 0 °C. To this was
added a solution of chromium(VI) oxide (4.13 g, 41.3 mmol) in acetic
anhydride (20 mL) dropwise at such a rate that the temperature did
not exceed 10 °C. After all the chromium(VI) oxide was added,
stirring was continued for a further 16 h at room temperature.
Subsequently, the reaction mixture was added to an ice−water mixture
(150 mL) and the solid was collected by filtration. Further material
was extracted from the solution with diethyl ether (2 × 50 mL); the
ethereal extracts were dried, and the solvent was evaporated. The
combined solid products were washed with 2% aqueous sodium
carbonate solution (1 × 50 mL) and then heated at reflux in ethanol/
water/concentrated sulfuric acid (53 mL, 10/10/1) for 30 min. The
solution was cooled to room temperature, the product was extracted
with ethyl acetate (4 × 50 mL), the combined organic extracts were
EXPERIMENTAL SECTION
■
General Remarks. 2-Bromo-1,4-bis(octyloxy)benzene (4b),43 4′-
(4-ethynylphenyl)-2,2′:6′,2″-terpyridine,47 2,5-bis(octyloxy)-4-(4-
[2,2′:6′,2″]terpyridin-4′-ylphenylethynyl)benzaldehyde (9b),47,48 bis-
(4,4′-formyl)benzophenone (5c),41 4′-(4-formylphenyl)-2,2′:6′,2″-
terpyridine (9a),47 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine
(ttpy),66 [Ru(tpy)Cl3],67 and [Ru(tpy)(MeCN)3](PF6)2 were
50
synthesized according to literature procedures. Dry toluene, THF,
and dichloromethane were obtained from a Pure-Solv MD-4-EN
solvent purification system (Innovative Technologies Inc.). Triethyl-
amine was dried over KOH and distilled. All other chemicals were
purchased from commercial suppliers and used as received. All
reactions were performed in oven-dried flasks and were monitored by
thin-layer chromatography (TLC) (silica gel on aluminum sheets with
fluorescent dye F254, Merck KGaA). Microwave reactions were
carried out using a Biotage Initiator Microwave synthesizer. NMR
spectra were recorded on a Bruker AVANCE 250 MHz, AVANCE 300
MHz, or AVANCE 400 MHz instrument in deuterated solvents
1
(Euriso-Top) at 25 °C. H and 13C resonances were assigned using
appropriate 2D correlation spectra. Chemical shifts are reported in
ppm using the solvent as internal standard. Matrix-assisted laser
desorption ionization time of flight (MALDI-TOF) mass spectra were
obtained using an Ultraflex III TOF/TOF mass spectrometer in
reflector mode. High-resolution electrospray ionization time of flight
mass spectrometry (ESI-Q-TOF MS) was performed on an ESI-(Q)-
TOF-MS microTOF II (Bruker Daltonics) mass spectrometer.
Melting points (mp) were determined on a Stuart SMP-3 apparatus.
UV−vis absorption spectra were recorded on a PerkinElmer Lambda
750 UV/vis spectrophotometer and emission spectra on Jasco FP6500
and FP-6200 instruments, respectively. Measurements were carried out
using 10−6 M solutions of the respective solvents (spectroscopy grade)
in 1 cm quartz cuvettes at room temperature. However, some emission
H
DOI: 10.1021/ic502431x
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
washed with saturated aqueous sodium hydrogen carbonate solution
(2 × 50 mL) and dried with Na2SO4, and the solvent was evaporated
to yield the crude product. Further purification was achieved by flash
chromatography (silica, n-hexane/dichloromethane 1/3) to give a
procedure. Therefore, KOH powder (190 mg, 3.38 mmol) was stirred
in dried DMSO (6 mL) and the solution was deaerated. 4-Bromo-5-
hydroxy-2-octyloxybenzophenone (274 mg, 0.676 mmol) in DMSO
(1.5 mL) and 1-bromooctane (259 μL, 1.487 mmol) in DMSO (1.5
mL) were added. The mixture was stirred for 22 h at room
temperature. The resulting solid was filtered off and dissolved in
toluene (50 mL). The toluene solution was extracted with water (3 ×
20 mL) and dried with Na2SO4, and the organic solvent was removed
under reduced pressure. The residue was purified by column
chromatography (silica, n-hexane/dichloromethane 1/1) to yield a
low-melting white solid (312 mg, 0.603 mmol, 89%, 62% overall
1
yellow solid (1 g, 4.76 mmol, 31%). Mp: 67−68 °C. H NMR (300
MHz, CDCl3, ppm): δ 10.13 (s, 1H, −CHO), 8.00 (d, 3J = 8.4 Hz, 2H,
HE3), 7.92 (d, 3J = 8.2 Hz, 2H, HE2), 7.86−7.77 (m, 2H, HG2), 7.63 (t,
3
3J = 7.4 Hz, 1H, HG4), 7.51 (t, J = 7.5 Hz, 2H, HG3). 13C NMR (75
MHz, CDCl3, ppm): δ 195.94, 191.75, 142.70, 138.61, 136.88, 133.26,
130.45, 130.24, 129.62, 128.67. Anal. Calcd for C14H10O2: C, 79.98; H,
4.79. Found: C, 80.11; H, 4.87.
1
̈
yield). Mp: 40 °C. H NMR (300 MHz, CD2Cl2, ppm): δ 7.80−7.72
General Procedure for Krohnke-Type Terpyridine Synthesis.
(m, 2H, HG2), 7.60−7.52 (m, 1H, HG4), 7.48−7.40 (m, 2H, HG3), 7.22
2-Acetylpyridine (2.2 equiv per aldehyde group), aldehyde derivate 5
(1 equiv), and sodium hydroxide (2.2 equiv per aldehyde group) were
ground in a mortar until a bright yellow powder was formed (10−20
min). The solid was transferred to a flask, ethanol (10 mL) and 25%
aqueous ammonia solution (5 mL) were added, and the suspension
was stirred at room temperature for 48 h. The gray precipitate that
formed was filtered and washed with water (15 mL) and ethanol (5
mL). The crude product was recrystallized in THF.
3
(s, 1H, HF3), 7.02 (s, 1H, HF6), 4.00 (t, J = 6.5 Hz, 2H, α-OCH2),
3.80 (t, 3J = 6.3 Hz, 2H, α-OCH2), 1.89−1.75 (m, 2H, β-CH2), 1.58−
1.44 (m, 2H, β-CH2), 1.44−1.05 (m, 20H, γ-η-CH2), 1.04−0.84 (m,
6H, CH3). 13C NMR (75 MHz, CD2Cl2, ppm): δ 196.02, 151.70,
150.45, 138.83, 133.37, 129.92, 129.29, 128.79, 118.60, 115.96, 114.91,
70.71, 69.94, 32.45, 32.38, 29.91, 29.87, 29.81, 29.76, 29.69, 29.50,
26.59, 26.19, 23.30, 23.27, 14.52, 14.51. HRMS (ESI-TOF, m/z):
517.2300, C29H42BrO3 ([M + H]+) requires 517.2312.
4‴-[2,2′:6′,2″]Terpyridin-4′-ylbenzophenone (6a). According to
the general procedure for Krohnke-type terpyridine synthesis, 2-
General Procedure for Sonogashira Cross-Coupling Reac-
tions. Copper(I) iodide (0.1−0.15 equiv) and [Pd(PPh3)4] (0.1−0.15
equiv) were added to a deaerated solution of an aromatic bromine (1
equiv) in a mixture of THF (10 mL) and triethylamine (5 mL). With
vigorous stirring, 4′-(4-ethynylphenyl)-2,2′:6′,2″-terpyridine (1.2
equiv) in THF (2 mL) was added. Subsequently, the reaction mixture
was heated to 60 °C for 48−72 h. After the mixture was cooled to
room temperature, the precipitated ammonia salt was filtered off and
washed intensely with THF, and the solvent was removed under
reduced pressure. Dichloromethane was added, and the solution was
washed with saturated aqueous ammonium chloride/EDTA (1/1)
solution and dried with Na2SO4. Further purification was achieved by
column chromatography (neutral alumina, dichloromethane/n-hex-
ane).
̈
acetylpyridine (0.38 g, 3.14 mmol), 4-formylbenzophenone (5a; 0.3 g,
1.427 mmol), and sodium hydroxide (0.126 g, 3.14 mmol) were
reacted to yield a beige solid (217 mg, 0.525 mmol, 37%). Mp: 122 °C.
1H NMR (300 MHz, CDCl3, ppm): δ 8.78 (s, 2H, HD3), 8.73 (d, 3J =
4.7 Hz, 2H, HC6), 8.68 (d, 3J = 8.0 Hz, 2H, HC3), 8.01 (d, 3J = 8.4 Hz,
3
2H, HE3), 7.94 (d, J = 8.3 Hz, 2H, HE2), 7.92−7.81 (m, 4H, HC4,
3
3
HG2), 7.62 (t, J = 7.4 Hz, 1H, HG4), 7.52 (t, J = 7.4 Hz, 2H, HG3),
7.36 (ddd, J = 7.3 Hz, J = 4.8 Hz, J = 0.9 Hz, 2H, HC5). 13C NMR
(75 MHz, CDCl3, ppm): δ 196.35, 156.27, 156.09, 149.28, 149.25,
142.58, 137.90, 137.66, 137.07, 132.71, 130.83, 130.20, 128.51, 127.41,
124.12, 121.52, 119.12. MS (MALDI-TOF, dithranol, m/z): 414.17,
C28H20N3O ([M + H]+) requires 414.16. Anal. Calcd for C28H19N3O·
H2O: C, 77.94; H, 4.91; N, 9.74. Found: C, 77.68; H, 4.81; N, 9.56.
UV−vis (CH2Cl2): λmax/nm (ε/L mol−1 cm−1) 284 (57700).
3
3
4
2,5-Bis(octyloxy)-4-(4-[2,2′:6′,2″]terpyridin-4′-ylphenylethynyl)-
benzophenone (6b). According to the general procedure for
Sonogashira cross-coupling reactions, copper(I) iodide (16.6 mg,
0.087 mmol), [Pd(PPh3)4] (100 mg, 0.087 mmol), 4-bromo-2,5-
bis(octyloxy)benzophenone (5b; 300 mg, 0.580 mmol), and 4′-(4-
ethynylphenyl)-2,2′:6′,2″-terpyridine (232 mg, 0.696 mmol) were
reacted for 72 h. Further purification was achieved by column
chromatography (neutral alumina, dichloromethane/n-hexane 2/1) to
yield an off-white solid (252 mg, 0.327 mmol, 57%). Mp: 110−112 °C.
1H NMR (300 MHz, CDCl3, ppm): δ 8.76 (s, 2H, HD3), 8.74 (d, 3J =
Bis(4‴,4′′′′-[2,2′:6′,2″]terpyridin-4′-yl)benzophenone (6c). Ac-
cording to the general procedure for Krohnke-type terpyridine
̈
synthesis, 2-acetylpyridine (0.671 g, 5.54 mmol), bis(4,4′-formyl)-
benzophenone (5c; 0.3 g, 1.26 mmol), and sodium hydroxide (0.222
g, 5.54 mmol) were reacted to yield a beige solid (180 mg, 0.279
mmol, 22%). Mp: >250 °C dec. 1H NMR (300 MHz, CDCl3, ppm): δ
8.80 (s, 4H, HD3), 8.74 (d, 3J = 4.1 Hz, 4H, HC6), 8.69 (d, 3J = 7.9 Hz,
3
3
4H, HC3), 8.05 (d, J = 8.3 Hz, 4H, HE3), 7.99 (d, J = 8.3 Hz, 4H,
HE2), 7.89 (td, J = 7.8 Hz, J = 1.3 Hz, 4H, HC4), 7.37 (dd, J = 6.6
3
4
3
4.7 Hz, 2H, HC6), 8.68 (d, 3J = 7.9 Hz, 2H, HC3), 7.93 (d, 3J = 8.5 Hz,
2H, HE2), 7.89 (td, 3J = 7.7 Hz, 4J = 1.7 Hz, 2H, HC4), 7.82−7.77 (m,
Hz, J = 5.2 Hz, 4H, HC5). 13C NMR (75 MHz, CDCl3, ppm): δ
3
195.84, 156.33, 156.14, 149.34, 149.26, 142.79, 137.84, 137.07, 130.87,
127.54, 124.13, 121.54, 119.17. MS (MALDI-TOF, dithranol, m/z):
645.21, C43H29N6O ([M + H]+) requires 645.24. Anal. Calcd for
C43H28N6O × 2 H2O: C, 75.87; H, 4.74; N, 12.35. Found: C, 75.63;
H, 4.87. N, 12.33. UV−vis (CH2Cl2): λmax/nm (ε/L mol−1 cm−1) 285
(68300).
3
3
2H, HG2), 7.70 (d, J = 8.4 Hz, 2H, HE3), 7.55 (t, J = 7.3 Hz, 1H,
H
G4), 7.43 (t, J = 7.5 Hz, 2H, HG3), 7.36 (ddd, J = 7.4 Hz, J = 4.8
3
3
3
Hz, 4J = 1.0 Hz, 2H, HC5), 7.11 (s, 1H, HF3), 7.01 (s, 1H, HF6), 4.06 (t,
3J = 6.4 Hz, 2H, OCH2−), 3.84 (t, J = 6.3 Hz, 2H, α-OCH2), 1.93−
3
1.80 (m, 2H, β-CH2), 1.63−1.49 (m, 2H, β-CH2), 1.46−0.93 (m, 20H,
γ-η-CH2), 0.93−0.81 (m, 6H, CH3). 13C NMR (75 MHz, CDCl3,
ppm): δ 196.32, 156.26, 156.19, 154.17, 150.81, 149.51, 149.27,
138.46, 138.41, 137.06, 132.90, 132.33, 130.00, 129.63, 128.29, 127.41,
124.23, 124.05, 121.52, 118.80, 117.27, 116.26, 113.99, 94.91, 87.21,
69.86, 69.27, 31.96, 31.88, 29.51, 29.48, 29.46, 29.29, 29.20, 29.07,
26.22, 25.75, 22.82, 22.77, 14.23, 14.23. HRMS (ESI-TOF, m/z):
792.4076, C52H55N3O3Na ([M + Na]+) requires 792.4136. Anal. Calcd
for C52H55N3O3: C, 81.11; H, 7.20; N, 5.46. Found: C, 81.01; H, 7.30;
N, 5.47. UV−vis (CH2Cl2): λmax/nm (ε/L mol−1 cm−1) 360 (31500),
303 (58000).
4′-(4-((2,5-Bis(octyloxy)phenyl)ethynyl)phenyl)-2,2′:6′,2″-terpyri-
dine (11b). According to the general procedure for Sonogashira cross-
coupling reactions, copper(I) iodide (9.5 mg, 0.050 mmol), [Pd-
(PPh3)4] (0.058 g, 0.050 mmol), 2-bromo-1,4-bis(octyloxy)benzene
(4b; 207 mg, 0.5 mmol), and 4′-(4-ethynylphenyl)-2,2′:6′,2″-
terpyridine (200 mg, 0.600 mmol) were reacted for 48 h. Further
purification was achieved by column chromatography (neutral
alumina, dichloromethane/n-hexane 1/2, then 1/1) to yield a white
4-Bromo-2,5-bis(octyloxy)benzophenone (5b). A solution of 2-
bromo-1,4-bis(octyloxy)benzene (4b; 400 mg, 0.968 mmol) and
benzoyl chloride (204 mg, 1.451 mmol) in dichloromethane (5 mL)
was stirred at 0 °C under nitrogen, while a mixture of aluminum(III)
trichloride (194 mg, 1.451 mmol) was slowly added. The solution was
stirred overnight at room temperature before being poured onto iced 2
M HCl solution (50 mL). The dichloromethane layer was separated,
and the aqueous phase was extracted with dichloromethane (3 × 30
mL). The combined organic layers were dried over Na2SO4, and the
organic solvents were removed under reduced pressure. The solid
residue was dissolved in dichloromethane (100 mL) and washed
successively with 2 M sodium hydroxide solution (3 × 30 mL) and
brine (50 mL) before the solution was dried and evaporated. The
residue was purified by column chromatography (silica, n-hexane/
dichloromethane 2/1) to yield a yellow viscous liquid (277 mg, 0.683
mmol, 71%). 1H NMR indicated the formation of 4-bromo-5-hydroxy-
2-octyloxybenzophenone by the loss of one octyloxy group during the
reaction. The group was reintroduced according to the literature
I
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Article
1
solid (280 mg, 0.420 mmol, 84%). Mp: 65−67 °C. H NMR (300
25.65, 22.81, 22.76, 21.72, 14.23, 14.22. MS (MALDI-TOF, dithranol,
m/z): 938.43, C59H64N5O4S ([M + H]+) requires 938.47.
MHz, CDCl3, ppm): δ 8.76 (s, 2H, HD3), 8.73 (d, J = 4.4 Hz, 2H,
3
HC6), 8.67 (d, J = 8.0 Hz, 2H, HC3), 7.95−7.83 (m, 4H, HE2, HC4),
Bis(4‴,4′′′′-[2,2′:6′,2″]terpyridin-4′-yl)benzophenone p-Tosyl Hy-
drazone (7c). According to the general procedure for hydrazone
condensation synthesis, bis(4‴,4′′′′-[2,2′:6′,2″]terpyridin-4′-yl)-
benzophenone (6c; 120 mg, 0.186 mmol), p-toluenesulfonyl hydrazide
(69 mg, 0.372 mmol), and tosylic acid monohydrate (2 mg, 0.011
mmol) were reacted in toluene (10 mL) to yield a white solid (60 mg,
3
7.67 (d, 3J = 8.3 Hz, 2H, HE3), 7.35 (ddd, 3J = 7.5 Hz, 3J = 4.8 Hz, 4J =
1.2 Hz, 2H, HC5), 7.06 (d, J = 1.8 Hz, 1H, HF6), 6.92−6.77 (m, 2H,
4
HF4, HF3), 4.03 (t, 3J = 6.4 Hz, 2H, α-OCH2), 3.93 (t, 3J = 6.5 Hz, 2H,
α-OCH2), 1.93−1.70 (m, 4H, β-CH2), 1.63−1.20 (m, 20H, γ-η-CH2),
0.98−0.78 (m, 6H, CH3). 13C NMR (75 MHz, CDCl3, ppm): δ 156.3,
156.1, 154.4, 153.0, 149.6, 149.3, 138.0, 137.0, 132.2, 127.3, 124.7,
124.0, 121.5, 118.8, 118.5, 117.0, 114.3, 113.6, 93.1, 87.8, 70.0, 68.9,
32.99, 31.97, 29.6, 29.6, 29.5, 29.5, 29.4, 26.3, 26.2, 22.83, 22.81, 14.3.
MS (MALDI-TOF, dithranol, m/z): 666.42, C45H52N3O2 ([M + H]+)
requires 666.41. Anal. Calcd for C45H51N3O2: C, 81.17; H, 7.72; N,
6.31. Found: C, 81.15; H, 8.07; N, 6.47. UV−vis (CH2Cl2): λmax/nm
(ε/L mol−1 cm−1) 338 (27400), 292 (44300) nm.
1
0.074 mmol, 40%). Mp >240 °C dec. H NMR (300 MHz, CDCl3,
ppm): δ 8.79−8.61 (m, 12H, HD3, HC6, HC3), 8.26−8.14 (m, 1H, NH),
3
8.02−7.94 (m, 4H, HE2), 7.93−7.81 (m, 4H, HC4), 7.77 (d, J = 8.5
Hz, 2H, Artosyl-H), 7.59 (d, 3J = 8.4 Hz, 2H, Artosyl-H), 7.44−7.28 (m,
8H, HE3, HC5), 2.45 (s, 3H, Artosyl-CH3). 13C NMR (75 MHz, CDCl3,
ppm): δ 156.29, 156.13, 156.07, 153.32, 149.39, 149.30, 149.23,
149.08, 144.53, 140.68, 139.92, 137.07, 135.68, 131.60, 129.95, 129.28,
128.76, 128.35, 128.21, 127.30, 124.12, 124.03, 121.54, 121.50, 119.09,
118.87, 29.83; MS (MALDI-TOF, dithranol, m/z): 813.29,
C50H37N8O2S ([M + H]+) requires 813.28.
General Procedure for Hydrazone Condensation Synthesis.
A two-neck flask was loaded with benzophenone derivate 6 (1 equiv),
p-toluenesulfonyl hydrazide (2 equiv), tosylic acid monohydrate (0.05
equiv), and THF or toluene and the mixture heated to reflux for 48 h
under nitrogen. After the mixture was cooled to room temperature, the
solvent was evaporated and the residue further purified by column
chromatography (neutral alumina, chloroform/ethyl acetate 95/5).
When applicable, deviations from this general protocol are given
below.
[2,2′:6′,2″]Terpyridin-4′-ylbenzophenone p-Tosyl Hydrazone
(7a). According to the general procedure for hydrazone condensation
synthesis, 4‴-[2,2′:6′,2″]terpyridin-4′-yl-benzophenone (6a; 131 mg,
0.317 mmol), p-toluenesulfonyl hydrazide (118 mg, 0.634 mmol), and
tosylic acid monohydrate (3 mg, 0.016 mmol) in toluene (10 mL)
General Procedure for Methanofullerene Synthesis. To a
solution of the p-tosyl hydrazone derivate 7 (1 equiv) in anhydrous
pyridine (3 mL) was added sodium methoxide (1.1 equiv) under a
nitrogen atmosphere. After the mixture was stirred at room
temperature for 15 min, a nitrogen-purged solution of C60 (3−4
equiv) in o-dichlorobenzene (15 mL) was added at once and the
mixture was heated to 180 °C for 24 h. After it was cooled to room
temperature, the reaction mixture was purified by column chromatog-
raphy (neutral alumina, toluene/n-hexane 1/1) and precipitation in
methanol.
1-Phenyl-1-(4-[2,2′:6′,2″]terpyridin-4′-ylphenyl)methanofullerene
(8a). According to the general procedure for methanofullerene
synthesis, [2,2′:6′,2″]terpyridin-4′-yl-benzophenone p-tosyl hydrazone
(7a; 60 mg, 0.103 mmol), sodium methoxide (6 mg, 0.111 mmol), and
C60 (276 mg, 0.383 mmol) were reacted to yield a brown solid (32 mg,
0.029 mmol, 28%). Mp: >360 °C. 1H NMR (300 MHz, CDCl33, ppm):
1
were reacted to yield a white solid (68 mg, 0.117 mmol, 37%). H
NMR suggests a mixture of cis- and trans-hydrazone isomers, which
was used directly for the synthesis of 8a. Mp: >240 °C dec. 1H NMR
(300 MHz, CDCl3, ppm): δ 8.79−8.59 (m, 6H, HD3, HC6, HC3), 7.98
(d, J = 8.3 Hz, 1H, HE2), 7.90 (d, J = 8.2 Hz, 2H, Artosyl-H), 7.92−
7.75 (m, 4H, HC4, HG2), 7.59−7.46 (m, 4H, HE2, HG3, HG4), 7.39−7.30
(m, 5H, NH, HC5, Artosyl-H), 7.29−7.24 (m, 1H, HE3), 7.20−7.13 (m,
1H, HE3), 2.43 (two singlets, 3H, Artosyl-CH3). 13C NMR (75 MHz,
CDCl3, ppm): 156.27, 156.13, 156.07, 156.03, 153.92, 153.77, 149.41,
149.27, 149.20, 149.06, 144.42, 144.30, 140.54, 139.85, 137.14, 137.05,
136.48, 135.69, 135.59, 131.79, 131.06, 130.36, 130.09, 129.94, 129.85,
129.83, 129.17, 128.73, 128.46, 128.42, 128.26, 128.11, 128.09, 127.76,
127.24, 124.12, 124.02, 121.50, 119.01, 118.83, 21.77, 21.76. HRMS
(ESI-TOF, m/z): 582.1903, C35H28N5O2S ([M + H]+) requires
582.1958. Anal. Calcd for C35H27N5O2S·H2O: C, 70.10; H, 4.87; N,
11.68; S, 5.35. Found: C, 69.93; H, 4.71; N, 11.32; S, 5.16.
3
3
3
δ 8.79 (s, 2H, HD3), 8.73 (d, J = 4.8 Hz, 2H, HC6), 8.69 (d, J = 7.9
Hz, 2H, HC3), 8.27 (d, 3J = 8.3 Hz, 2H, HE2), 8.22−8.15 (m, 2H, HG2),
8.02 (d, 3J = 8.3 Hz, 2H, HE3), 7.90 (td, 3J = 7.8 Hz, 4J = 1.8 Hz, 2H,
3
HC4), 7.53 (t, J = 7.5 Hz, 2H, HG3), 7.46−7.33 (m, 3H, HG4, HC5).
MS (MALDI-TOF, negative mode, terthiophene, m/z): 1117.14,
C88H19N3 ([M + e]−) requires 1117.16. Anal. Calcd for C88H19N3·
2.5H2O·3(hexane): C, 89.55; H, 4.68; N, 2.96. Found: C, 89.57; H,
4.51; N, 3.01.
1-Phenyl-1-(2,5-Bis(octyloxy)-4-(4-[2,2′:6′,2″]terpyridin-4′-
ylphenylethynyl))methanofullerene (8b). According to the general
procedure for methanofullerene synthesis, 2,5-bis(octyloxy)-4-(4-
[2,2′:6′,2″]terpyridin-4′-ylphenylethynyl)benzophenone p-tosyl hydra-
zone (7b; 57 mg, 0.061 mmol), sodium methoxide (4 mg, 0.074
mmol), and C60 (175 mg, 0.243 mmol) were reacted to yield a dark
2,5-Bis(octyloxy)-4-(4-[2,2′:6′,2″]terpyridin-4′-yl-phenylethynyl)-
benzophenone p-Tosyl Hydrazone (7b). According to the general
procedure for hydrazone condensation synthesis, 2,5-bis(octyloxy)-4-
(4-[2,2′:6′,2″]terpyridin-4′-ylphenylethynyl)benzophenone (6b; 100
mg, 0.130 mmol), p-toluenesulfonyl hydrazide (48 mg, 0.260 mmol),
and tosylic acid monohydrate (1.2 mg, 6.5 μmol) were reacted in THF
(10 mL) for 11 days. The reaction was monitored by MALDI-TOF
MS. After 6 days, additional p-toluenesulfonyl hydrazide (1 equiv) and
tosylic acid monohydrate (0.1 equiv) were added. After purification by
column chromatography (neutral alumina, chloroform) and recrystal-
lization (n-hexane), a white solid (74 mg, 0.079 mmol, 61%) was
obtained. 1H NMR suggests a mixture of cis- and trans-hydrazone
isomers, which was used directly for the synthesis of 8b. Mp: 83 °C.
1H NMR (300 MHz, CDCl3, ppm): δ 8.81−8.65 (m, 6H, HD3, HC6,
1
brown solid (24 mg, 0.016 mmol, 27%). Mp: 148 °C. H NMR (300
3
MHz, CDCl3, ppm): δ 8.76 (s, 2H, HD3), 8.74 (d, J = 4.8 Hz, 2H,
3
3
HC6), 8.68 (d, J = 7.9 Hz, 2H, HC3), 8.24 (d, J = 7.1 Hz, 2H, HG2),
7.96−7.82 (m, 4H, HE2, HC4), 7.68 (d, 3J = 8.2 Hz, 2H, HE3), 7.64 (s,
1H, HF6), 7.50 (t, 3J = 7.3 Hz, 2H, HG3), 7.46−7.38 (m, 1H, HG4), 7.36
(dd, J = 6.8 Hz, J = 5.4 Hz, 2H, HC5), 7.18 (s, 1H, HF3), 4.27−3.98
(m, 4H, α-OCH2), 2.13−1.99 (m, 2H, β-CH2), 1.93−1.78 (m, 2H, β-
CH2), 1.75−1.10 (m, 20H, γ-η-CH2), 0.97−0.79 (m, 6H, CH3). MS
(MALDI-TOF, negative mode, terthiophene, m/z): 1473.38,
C112H55N3O2 ([M + e]−) requires 1473.43. Anal. Calcd for
C112H55N3O2·8H2O: C, 83.10; H, 4.42%; N, 2.60. Found: C, 83.34;
H, 4.47; N, 2.49.
3
3
HC3), 8.01−7.84 (m, 6H, Artosyl-H, HE2, HC4), 7.77 (s, 1H, NH), 7.70
(d, 3J = 8.4 Hz, 2H, HE3), 7.57−7.47 (m, 2H, HG2), 7.42−7.27 (m, 7H,
HC5, HG3, HG4, Artosyl-H), 7.16 (s, 1H, HF3), 6.51 (s, 1H, HF6), 3.91 (t,
3J = 6.4 Hz, 2H, α-OCH2), 3.79 (t, 3J = 6.3 Hz, 2H, α-OCH2), 2.41 (s,
3H, Artosyl−CH3), 1.75−1.46 (m, 4H, β-CH2), 1.46−0.93 (m, 20H,
γ−η−CH2), 0.95−0.78 (m, 6H, CH3); 13C NMR (75 MHz, CDCl3,
ppm): δ 156.26, 156.22, 154.69, 151.75, 149.48, 149.42, 149.28,
143.92, 138.56, 137.04, 136.66, 136.04, 132.35, 129.77, 129.68, 129.62,
129.18, 128.34, 128.32, 128.13, 127.53, 127.43, 127.37, 124.05, 121.64,
121.52, 118.79, 118.20, 115.91, 113.78, 94.86, 86.70, 69.85, 69.82,
32.00, 31.94, 31.84, 29.49, 29.44, 29.40, 29.26, 29.20, 28.93, 26.18,
1,1-Bis(4-[2,2′:6′,2″]terpyridin-4′-ylphenyl)methanofullerene (8c).
According to the general procedure for methanofullerene synthesis,
bis(4‴,4′′′′-[2,2′:6′,2″]terpyridin-4′-yl)benzophenone p-tosyl hydra-
zone (7c; 60 mg, 0.074 mmol), sodium methoxide (4 mg, 0.074
mmol), and C60 (227 mg, 0.315 mmol) were reacted to yield a brown
solid (30 mg, 0.022 mmol, 30%). Mp: >360 °C. 1H NMR (300 MHz,
CDCl3, ppm): δ 8.79 (s, 4H, HD3), 8.73 (d, 3J = 4.0 Hz, 4H, HC6), 8.68
(d, 3J = 8.0 Hz, 4H, HC3), 8.31 (d, 3J = 8.2 Hz, 4H, HE2), 8.04 (d, 3J =
3
4
8.2 Hz, 4H, HE3), 7.88 (td, J = 7.7 Hz, J = 1.7 Hz, 4H, HC4), 7.35
(ddd, J = 7.4 Hz, J = 4.8 Hz, J = 0.9 Hz, 4H, HC5). MS (MALDI-
3
3
4
J
DOI: 10.1021/ic502431x
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
TOF, negative mode, terthiophene, m/z): 1348.23, C103H28N6 ([M +
e]−) requires 1348.24. Anal. Calcd for C103H28N6·4H2O·5(hexane): C,
86.24; H, 5.77; N, 4.54. Found: C, 86.11; H, 5.48; N, 4.44.
(MeCN)3](PF6)2 (6.4 mg, 8.5 μmol) and 8a (9.4 mg, 8.4 μmol)
were reacted to yield a dark red solid (6 mg, 3.4 μmol, 41%). 1H NMR
3
(400 MHz, CD3CN, ppm): δ 9.02 (s, 2H, HD3), 8.75 (d, J = 8.2 Hz,
3
2H, HB3), 8.69−8.57 (m, 4H, HE2, HC3), 8.48 (d, J = 8.1 Hz, 2H,
N-Methyl-2-(4-[2,2′:6′, 2″]terpyridin-4′-ylphenyl)-
pyrrolidinofullerene (10a). A mixture of (4-formylphenyl)-2,2′:6′,2″-
terpyridine (9a; 33 mg, 0.098 mmol), N-methylglycine (87 mg, 0.978
mmol), and C60 (282 mg, 0.391 mmol) in deaerated, anhydrous
toluene (200 mL) was stirred at 120 °C for 24 h under a nitrogen
atmosphere. After the mixture was cooled to room temperature, the
solvent was evaporated. The crude product was purified by column
chromatography (neutral alumina, toluene then chloroform), and slow
vapor diffusion of diethyl ether into a concentrated solution yielded a
3
3
HA3), 8.41 (t, J = 8.1 Hz, 1H, HB4), 8.35 (d, J = 7.2 Hz, 4H, HG2,
HE3), 8.00−7.80 (m, 4H, HC4, HA4), 7.61−7.48 (m, 2H, HG3), 7.49−
7.39 (m, 1H, HG4), 7.38−7.30 (m, 4H, HA6, HC6), 7.21−7.01 (m, 4H,
HC5, HA5). 13C NMR (100 MHz, CD3CN, ppm): δ 159.05, 159.00,
156.47, 156.28, 153.58, 153.22, 149.57, 149.52, 148.25, 146.94, 146.80,
146.20, 145.72, 145.70, 145.61, 145.36, 145.27, 144.83, 143.96, 143.89,
143.17, 143.08, 142.46, 141.83, 139.77, 139.10, 139.01, 138.84, 138.69,
137.71, 136.89, 133.19, 132.11, 130.11, 129.73, 129.38, 128.52, 128.47,
125.49, 124.76, 122.70, 80.14, 58.87. HRMS (ESI-TOF, m/z):
726.0829, C103H30N6Ru ([M − 2PF6]2+) requires 726.0785.
1
brown solid (26.5 mg, 0.024 mmol, 25%). Mp: >360 °C. H NMR
3
(300 MHz, CDCl3, ppm): δ 8.74 (s, 2H, HD3), 8.72 (d, J = 4.8 Hz,
3
2H, HC6), 8.67 (d, J = 7.9 Hz, 2H, HC3), 8.00−7.93 (m, 4H, HE2,
[Ru(tpy)(8b)](PF6)2 (1b). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
(MeCN)3](PF6)2 (6.4 mg, 8.5 μmol) and 8b (9 mg, 6.1 μmol)
were reacted to yield a dark red solid (4 mg, 1.9 μmol, 31%). 1H NMR
HE3), 7.87 (td, 3J = 7.8 Hz, 4J = 1.7 Hz, 2H, HC4), 7.35 (ddd, 3J = 7.5
Hz, 3J = 4.8 Hz, 4J = 1.1 Hz, 2H, HC5), 5.02 (d, 2J = 9.2 Hz, 1H, HH5),
5.02 (s, 1H, HH2), 4.30 (d, 2J = 9.5 Hz, 1H, HH5), 2.85 (s, 3H, NCH3).
MS (MALDI-TOF, negative mode, terthiophene, m/z): 1083.26,
C84H19N4 ([M − H]−) requires 1083.16. Anal. Calcd for C84H20N4·
6H2O: C, 84.56; H, 2.70; N, 4.70. Found: C, 84.26; H, 2.44; N, 5.40.
N-Methyl-2-(2,5-Bis(octyloxy)-4-(4-[2,2′:6′,2″]terpyridin-4′-
ylphenylethynyl))pyrrolidinofullerene (10b). A mixture of 2,5-bis-
(octyloxy)-4-(4-[2,2′:6′,2″]-terpyridin-4′-ylphenylethynyl)-
benzaldehyde (9b; 69 mg, 0.1 mmol), N-methylglycine (89 mg, 1.0
mmol), and C60 (144 mg, 0.2 mmol) in deaerated, anhydrous toluene
(200 mL) was stirred at 120 °C for 24 h under a nitrogen atmosphere.
After the mixture was cooled to room temperature, the solvent was
evaporated. The crude product was purified by column chromatog-
raphy (neutral alumina, n-hexane/toluene 3/1 then toluene) to yield a
3
(300 MHz, CD3CN, ppm): δ 8.96 (s, 2H, HD3), 8.75 (d, J = 8.2 Hz,
2H, HB3), 8.59 (d, 3J = 7.3 Hz, 2H, 2H, HC3), 8.49 (d, 3J = 8.3 Hz, 2H,
3
3
HA3), 8.41 (t, J = 8.1 Hz, 1H, HB4), 8.35 (d, J = 5.8 Hz, 2H, HG2),
8.21 (d, 3J = 7.5 Hz, 2H, HE2), 7.99−7.78 (m, 7H, HE3, HF6, HC4, HA4),
7.56−7.39 (m, 3H, HG3, HG4), 7.39 (d, 3J = 5.2 Hz, 2H, HA6), 7.34 (d,
3J = 5.3 Hz, 2H, HC6), 7.25 (s, 1H, HF3), 7.21−7.07 (m, 4H, HC5, HA5),
4.29−4.10 (m, 3H, α-OCH2), 4.08−3.92 (m, 1H, α-OCH2), 1.85−
1.59 (m, 4H, β-CH2), 1.55−1.02 (m, 20H, γ-η-CH2), 0.91−0.67 (m,
6H, CH3). HRMS (ESI-TOF, m/z): 904.2109, C127H66N6O2Ru ([M
− 2PF6]2+) requires 904.2143.
[Ru2(tpy)2(8c)](PF6)4 (1c). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
(MeCN)3](PF6)2 (9.7 mg, 13 μmol) and 8c (8.7 mg, 6.5 μmol)
were reacted to yield a dark red solid (8 mg, 3.1 μmol, 48%). 1H NMR
1
dark brown-black solid (101 mg, 0.07 mmol, 70%). Mp: 155 °C. H
NMR (400 MHz, CD2Cl2, ppm): δ 8.77 (s, 2H, HD3), 8.71 (d, 3J = 4.7
Hz, 2H, HC6), 8.68 (d, 3J = 7.9 Hz, 2H, HC3), 7.93−7.86 (m, 4H, HE2,
HC4), 7.67 (d, 3J = 8.5 Hz, 2H, HE3), 7.65 (s, 1H, HF5), 7.37 (ddd, 3J =
7.4 Hz, 3J = 4.8 Hz, 4J = 1.1 Hz, 2H, HC5), 7.09 (s, 1H, HF2), 5.58 (s,
3
(300 MHz, CD3CN, ppm): δ 9.08 (s, 4H, HD3), 8.80 (d, J = 8.1 Hz,
3
3
4H, HE2), 8.75 (d, J = 8.2 Hz, 4H, HB3), 8.67 (d, J = 7.9 Hz, 4H,
HC3), 8.54−8.37 (m, 10H, HA3, HE3, HB4), 8.00−7.86 (m, 8H, HC4,
2
2
1H, HH2), 4.97 (d, J = 9.4 Hz, 1H, HH5), 4.33 (d, J = 9.5 Hz, 1H,
H
HA4), 7.42 (d, J = 5.2 Hz, 4H, HA6), 7.36 (d, J = 5.2 Hz, 4H, HC6),
7.23−7.10 (m, 8H, HC5, HA5). 13C NMR (63 MHz, CD3CN, ppm): δ
159.07, 156.56, 156.33, 153.58, 153.32, 149.39, 148.32, 146.92, 146.27,
146.24, 145.74, 145.68, 145.46, 144.86, 144.05, 143.98, 143.15, 143.07,
141.96, 141.91, 139.13, 139.06, 138.81, 138.09, 136.89, 133.46, 129.54,
128.54, 128.49, 125.58, 125.47, 124.76, 122.76, 79.99, 58.28. HRMS
(ESI-TOF, m/z): 504.5643, C133H50N12Ru2 ([M − 4PF6]4+) requires
504.5599.
3
3
H5), 4.20 (dt, J = 9.5 Hz, J = 6.6 Hz, 1H, α-OCH2), 4.10 (dt, J =
2
3
2
9.6 Hz, 3J = 6.4 Hz, 1H, α-OCH2), 4.03 (dt, 2J = 13.1 Hz, 3J = 6.5 Hz,
2
3
1H, α-OCH2), 3.74 (dt, J = 8.6 Hz, J = 6.5 Hz, 1H, α-OCH2), 2.83
(s, 3H, NCH3), 1.87−1.76 (m, 2H, β-CH2), 1.73−1.49 (m, 6H, β-
CH2, γ-CH2), 1.48−1.17 (m, 16H, δ-η-CH2), 0.96−0.73 (m, 6H,
CH3). 13C NMR (100 MHz, CD2Cl2, ppm): δ 157.34, 156.51, 156.39,
155.57, 154.70, 154.68, 154.36, 152.03, 149.59, 149.58, 147.66, 147.22,
147.15, 146.62, 146.60, 146.56, 146.47, 146.43, 146.41, 146.32, 146.31,
146.14, 145.99, 145.90, 145.66, 145.64, 145.60, 145.58, 145.54, 145.48,
144.97, 144.92, 144.85, 144.72, 143.40, 143.36, 143.03, 142.99, 142.91,
142.74, 142.70, 142.62, 142.57, 142.50, 142.49, 142.47, 142.34, 142.19,
142.10, 142.08, 140.50, 140.45, 139.97, 139.91, 137.24, 136.83, 136.76,
136.54, 135.09, 132.45, 128.24, 127.65, 124.72, 124.34, 121.50, 118.88,
116.49, 115.24, 113.12, 93.52, 88.23, 77.05, 76.00, 70.33, 70.17, 69.77,
69.21, 40.24, 32.35, 32.32, 30.11, 29.93, 29.90, 29.82, 29.74, 29.73,
29.67, 26.55, 26.48, 23.19, 23.14, 21.55, 14.40, 14.35. MS (MALDI-
TOF, negative mode, terthiophene, m/z): 1440.42, C108H56N4O2 ([M
+ e]−) requires 1440.44. Anal. Calcd for C108H56N4O2·0.5(hexane): C,
89.79; H, 4.28; N, 3.77. Found: C, 89.78; H, 4.43; N, 3.83.
[Ru(tpy)(10a)](PF6)2 (2a). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
(MeCN)3](PF6)2 (8.9 mg, 12 μmol) and 10a (13 mg, 12 μmol)
were reacted to yield a dark red solid (7 mg, 4.1 μmol, 34%). 1H NMR
3
(300 MHz, CD3CN, ppm): δ 9.00 (s, 2H, HD3), 8.74 (d, J = 8.2 Hz,
3
3
2H, HB3), 8.62 (d, J = 7.8 Hz, 2H, HC3), 8.48 (d, J = 8.1 Hz, 2H,
HA3), 8.40 (t, J = 8.5 Hz, 1H, HB4), 8.34−8.19 (m, 4H, HE2, HE3),
3
7.98−7.86 (m, 4H, HC4, HA4), 7.40 (d, 3J = 5.5 Hz, 2H, HA6), 7.32 (d,
3J = 5.1 Hz, 2H, HC6), 7.21−7.08 (m, 4H, HC5, HA5), 5.29 (s, 1H,
2
2
H
H2), 5.14 (d, J = 9.5 Hz, 1H, HH5), 4.44 (d, J = 9.7 Hz, 1H, HH5),
2.91 (s, 3H, NCH3). HRMS (ESI-TOF, m/z): 709.5853, C99H31N7Ru
([M − 2PF6]2+) requires 709.5839.
General Procedure for the Synthesis of Heteroleptic
Ruthenium Bis(terpyridine) Complexes. A microwave vial was
charged with [Ru(tpy)(MeCN)3](PF6)2 (1 equiv per terpyridine
group), terpyridine derivative (1 equiv), and DMF (3 mL). The vial
was capped, purged with nitrogen for 20 min, and heated through
microwave irradiation at 140 °C for 30 min. Subsequently, the solution
was cooled to room temperature and the product was precipitated by
addition of an aqueous ammonium hexafluorophosphate solution. The
solid was collected by filtration, washed thoroughly with water and
diethyl ether, and dissolved in acetonitrile. The solution was
concentrated and treated with diethyl ether vapor to slowly precipitate
the complex. When applicable, deviations from this general protocol
are given below.
[Ru(tpy)(10b)](PF6)2 (2b). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
(MeCN)3](PF6)2 (15.6 mg, 21 μmol) and 10b (30 mg, 21 μmol)
1
were reacted to yield a dark red solid (23 mg, 11 μmol, 54%). H
NMR (400 MHz, CD2Cl2, ppm): δ 8.83 (s, 2H, HD3), 8.69 (d, 3J = 8.1
Hz, 2H, HB3), 8.51 (d, 3J = 7.8 Hz, 2H, HC3), 8.48−8.36 (m, 3H, HB4,
3
HA3), 8.12 (d, J = 8.0 Hz, 2H, HE2), 7.99−7.87 (m, 4H, HC4, HA4),
7.86 (d, 3J = 7.9 Hz, 2H, HE3), 7.69 (s, 1H, HF5), 7.39 (d, 3J = 5.4 Hz,
3
2H, HA6), 7.32 (d, J = 5.7 Hz, 2H, HC6), 7.26−7.17 (m, 4H, HC5,
2
HA5), 7.14 (s, 1H, HF2), 5.61 (s, 1H, HH2), 5.01 (d, J = 9.6 Hz, 1H,
2
H
H5), 4.37 (d, J = 9.4 Hz, 1H, HH5), 4.28−4.18 (m, 1H, α-OCH2),
4.18−4.09 (m, 1H, α-OCH2), 4.10−4.00 (m, 1H, α-OCH2), 3.82−
3.71 (m, 1H, α-OCH2), 2.86 (s, 3H, NCH3), 1.90−1.78 (m, 2H, β-
CH2), 1.73−1.12 (m, 22H, β-CH2, γ-η-CH2), 0.94−0.75 (m, 6H,
CH3). 13C NMR (100 MHz, DMSO-d6, ppm): δ 157.91, 157.74,
[Ru(tpy)(8a)](PF6)2 (1a). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
K
DOI: 10.1021/ic502431x
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
157.04, 155.14, 155.00, 154.72, 154.25, 153.91, 153.54, 152.13, 152.07,
151.16, 146.80, 146.69, 146.62, 146.35, 145.74, 145.68, 145.65, 145.63,
145.57, 145.42, 145.25, 145.08, 144.99, 144.79, 144.71, 144.55, 144.49,
144.13, 143.98, 143.92, 143.85, 142.54, 142.16, 142.07, 141.89, 141.84,
141.75, 141.63, 141.49, 141.32, 141.21, 141.11, 139.65, 139.55, 139.43,
138.87, 138.77, 138.14, 138.04, 137.92, 135.85, 135.78, 135.56, 134.34,
133.52, 131.95, 129.63, 129.59, 127.92, 127.79, 127.70, 127.63, 124.88,
124.85, 124.84, 124.58, 124.56, 124.54, 124.02, 120.93, 120.91, 116.41,
114.44, 114.43, 114.40, 112.16, 109.46, 93.04, 88.81, 76.32, 75.05,
69.10, 69.06, 68.47, 40.43, 31.36, 31.30, 29.03, 28.95, 28.80, 28.73,
28.39, 25.49, 25.45, 22.25, 22.13, 14.05, 14.01. HRMS (ESI-TOF, m/
z): 887.7307, C123H67N7O2Ru ([M − 2PF6]2+) requires 887.7212.
[Ru(tpy)(ttpy)](PF6)2 (3a). According to the general procedure for
heteroleptic ruthenium bis(terpyridine) complexes, [Ru(tpy)-
(MeCN)3](PF6)2 (58.5 mg, 0.078 mmol) and ttpy (25.3 mg, 0.078
mmol) were reacted in ethanol (5 mL) at 130 °C. Subsequently, the
solvent was evaporated and the resulting residue was purified by
column chromatography (silica, MeCN/H2O/saturated aqueous
KNO3 solution 40/4/1). Concentration of the product fraction in
vacuo and precipitation by addition of an aqueous ammonium
hexafluorophosphate solution yielded a red solid (56 mg, 0.059 mmol,
76%). 1H NMR (300 MHz, CD3CN, ppm): δ 8.99 (s, 2H, HD3), 8.76
(d, 3J = 8.1 Hz, 2H, HB3), 8.64 (d, 3J = 8.1 Hz, 2H, HC3), 8.50 (d, 3J =
8.1 Hz, 2H, HA3), 8.41 (t, 3J = 8.1 Hz, 1H, HB4), 8.11 (d, 3J = 8.1 Hz,
AUTHOR INFORMATION
Corresponding Authors
*E-mail for B.D.: benjamin.dietzek@ipht-jena.de.
*E-mail for U.S.S.: ulrich.schubert@uni-jena.de.
■
Author Contributions
⊥The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript. These authors contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support by the Deutsche Forschungsgemeinschaft
(DFG, Grant Nos. SCHU1229-16/1 and DI1517-3/1) and the
Fonds der Chemischen Industrie is kindly acknowledged.
Moreover, this project was supported by the COST Action
CM1202 Perspect-H2O. The authors also thank Sarah Crotty
(MALDI MS), Nicole Fritz (ESI MS), and Sandra Kohn
(elemental analysis) for their help with the respective
measurements.
̈
3
2H, HE2), 8.00−7.87 (m, 4H, HC4, HA4), 7.58 (d, J = 7.9 Hz, 2H,
REFERENCES
3
3
HE3), 7.43 (d, J = 5.5 Hz, 2H, HA6), 7.35 (d, J = 5.4 Hz, 2H, HC6),
7.22−7.11 (m, 4H, HC5, HA5), 2.54 (s, 3H, Ph−CH3). 13C NMR (75
MHz, CD3CN, ppm): δ 159.20, 159.08, 156.41, 156.38, 153.54,
153.36, 149.42, 142.07, 139.05, 139.01, 136.71, 134.91, 131.30, 128.67,
128.46, 128.42, 125.48, 125.40, 124.70, 122.37, 21.43. Anal. Calcd for
C37H28F12N6P2Ru: C, 46.89; H, 2.98; N, 8.87. Found: C, 46.53; H,
3.02; N, 8.76.
■
(1) Artero, V.; Chavarot-Kerlidou, M.; Fontecave, M. Angew. Chem.,
Int. Ed. 2011, 50, 7238.
(2) Andreiadis, E. S.; Chavarot-Kerlidou, M.; Fontecave, M.; Artero,
V. Photochem. Photobiol. 2011, 87, 946.
(3) Artero, V.; Fontecave, M. Coord. Chem. Rev. 2005, 249, 1518.
(4) Natali, M.; Campagna, S.; Scandola, F. Chem. Soc. Rev. 2014, 43,
4005.
[Ru(tpy)(11b)](PF6)2 (3b). A mixture of [Ru(tpy)]Cl3 (4.4 mg, 10
μmol) and silver(I) tetrafluoroborate (5.8 mg, 30 μmol) in deaerated
acetone (3 mL) was heated to 70 °C for 2 h. After cooling and
filtration, DMF (2 mL) was added to the filtrate and the acetone was
removed in vacuo. The resulting blue solution of [Ru(tpy)(acetone)3]-
(BF4)3 was added to a solution of 4′-(4-((2,5-Bis(octyloxy)phenyl)-
ethynyl)phenyl)-2,2′:6′,2″-terpyridine (11b; 20 mg, 14 μmol) in DMF
(3 mL), and the mixture was heated to 160 °C for 3 h. Subsequently,
the reaction mixture was cooled to room temperature and a solid was
precipitated by addition of an aqueous ammonium hexafluorophos-
phate solution. After filtration, the solid was further purified by column
chromatography (silica, MeCN/H2O/saturated aqueous KNO3
solution 40/4/1). Concentration of the product fraction in vacuo
and precipitation by addition of an aqueous ammonium hexafluor-
(5) Sartorel, A.; Bonchio, M.; Campagna, S.; Scandola, F. Chem. Soc.
Rev. 2013, 42, 2262.
(6) Carraro, M.; Sartorel, A.; Toma, F. M.; Puntoriero, F.; Scandola,
F.; Campagna, S.; Prato, M.; Bonchio, M. Top. Curr. Chem. 2011, 303,
121.
(7) Barber, J.; Tran, P. D. J. R. Soc. Interface 2013, 10.
(8) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 2001, 34, 40.
(9) Berardi, S.; Drouet, S.; Francas, L.; Gimbert-Surinach, C.;
̀
̃
Guttentag, M.; Richmond, C.; Stoll, T.; Llobet, A. Chem. Soc. Rev.
2014, 43, 7501.
(10) Sun, L.; Gao, Y.; Yu, Z.; Ding, X.; Duan, L. Faraday Discuss.
2014, DOI: 10.1039/c4fd00127c.
(11) Fukuzumi, S.; Ohkubo, K.; Suenobu, T. Acc. Chem. Res. 2014,
1
47, 1455.
ophosphate solution yielded a red solid (10 mg, 7.8 μmol, 78%). H
NMR (300 MHz, CD3CN, ppm): δ 9.01 (s, 2H, HD3), 8.76 (d, 3J = 8.2
Hz, 2H, HB3), 8.65 (d, 3J = 8.0 Hz, 2H, HC3), 8.50 (d, 3J = 8.0 Hz, 2H,
(12) Wenger, O. S. Chem. Soc. Rev. 2011, 40, 3538.
(13) Schubert, C.; Wielopolski, M.; Mewes, L. H.; de Miguel Rojas,
G.; van der Pol, C.; Moss, K. C.; Bryce, M. R.; Moser, J. E.; Clark, T.;
Guldi, D. M. Chem. Eur. J. 2013, 19, 7575.
(14) Guldi, D. M.; Maggini, M.; Scorrano, G.; Prato, M. J. Am. Chem.
Soc. 1997, 119, 974.
(15) Guldi, D. M. Chem. Soc. Rev. 2002, 31, 22.
(16) Wielopolski, M.; Atienza, C.; Clark, T.; Guldi, D. M.; Martín, N.
Chem. Eur. J. 2008, 14, 6379.
(17) Wielopolski, M.; Santos, J.; Illescas, B. M.; Ortiz, A.; Insuasty,
B.; Bauer, T.; Clark, T.; Guldi, D. M.; Martín, N. Energy Environ. Sci.
2011, 4, 765.
3
3
HA3), 8.42 (t, J = 8.1 Hz, 1H, HB4), 8.25 (d, J = 8.5 Hz, 2H, HE2),
8.00−7.84 (m, 6H, HC4, HA4, HE3), 7.42 (d, 3J = 4.9 Hz, 2H, HA6), 7.36
(d, 3J = 4.9 Hz, 2H, HC6), 7.22−7.13 (m, 4H, HC5, HA5), 7.09 (d, 4J =
2.4 Hz, 1H, HF6), 7.02−6.90 (m, 2H, HF4, HF3), 4.08 (t, J = 6.3 Hz,
3
2H, α-OCH2), 3.97 (t, 3J = 6.5 Hz, 2H, α-OCH2), 1.91−1.68 (m, 4H,
β-CH2), 1.67−1.21 (m, 20H, γ-η-CH2), 1.01−0.80 (m, 6H, CH3). 13
C
NMR (75 MHz, CD3CN, ppm): δ 159.09, 159.05, 156.6, 156.3, 155.2,
153.9, 153.6, 153.4, 148.2, 139.12, 139.07, 137.4, 136.9, 133.4, 129.0,
128.5, 128.5, 126.5, 125.6, 125.4, 124.7, 122.4, 119.5, 118.1, 115.3,
113.7, 93.2, 89.7, 70.4, 69.6, 32.61, 32.59, 30.2, 30.14, 30.11, 30.07,
30.04, 30.02, 26.9, 26.7, 23.5, 23.4, 14.5, 14.4. HRMS (ESI-TOF, m/
z): 500.1984, C60H62N6O2Ru ([M − 2PF6]2+) requires 500.1992.
(18) Ventura, B.; Barbieri, A.; Zanelli, A.; Barigelletti, F.; Seneclauze,
J. B.; Diring, S.; Ziessel, R. Inorg. Chem. 2009, 48, 6409.
(19) Liu, Y. F.; Zhao, J. Z. Chem. Commun. 2012, 48, 3751.
(20) Martín, N.; San
98, 2527.
́ ́
chez, L.; Illescas, B.; Perez, I. Chem. Rev. 1998,
ASSOCIATED CONTENT
■
(21) Armaroli, N. Photochem. Photobiol. Sci. 2003, 2, 73.
(22) Medlycott, E. A.; Hanan, G. S. Chem. Soc. Rev. 2005, 34, 133.
(23) Medlycott, E. A.; Hanan, G. S. Coord. Chem. Rev. 2006, 250,
1763.
(24) Photochemistry and Photophysics of Coordination Compounds I ;
Balzani, V., Campagna, S., Eds.; Springer: Berlin/Heidelberg, 2007.
S
* Supporting Information
Figures S1−S62, giving cyclic voltammograms, absorption and
emission spectra, time-resolved data, DFT calculations, NMR
data, and MS spectra. This material is available free of charge
via the Internet at http://pubs.acs.org.
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DOI: 10.1021/ic502431x
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Inorganic Chemistry
Article
́
(25) Armaroli, N.; Accorsi, G.; Felder, D.; Nierengarten, J. F. Chem.
Eur. J. 2002, 8, 2314.
(55) Herranz, M. A.; Diederich, F.; Echegoyen, L. Eur. J. Org. Chem.
2004, 2299.
(56) Schubert, U. S.; Winter, A.; Newkome, G. R. Terpyridine-based
Materials; Wiley-VCH: Weinheim, Germany, 2011.
(57) Thomas, K. G.; Biju, V.; Guldi, D. M.; Kamat, P. V.; George, M.
V. J. Phys. Chem. B 1999, 103, 8864.
(26) Chaignon, F.; Torroba, J.; Blart, E.; Borgstrom, M.;
̈
Hammarstrom, L.; Odobel, F. New J. Chem. 2005, 29, 1272.
̈
(27) Zhou, Z. G.; Sarova, G. H.; Zhang, S.; Ou, Z. P.; Tat, F. T.;
Kadish, K. M.; Echegoyen, L.; Guldi, D. M.; Schuster, D. I.; Wilson, S.
R. Chem. Eur. J. 2006, 12, 4241.
(58) Bensasson, R. V.; Bienvenue, E.; Fabre, C.; Janot, J. M.; Land, E.
̈
J.; Leach, S.; Leboulaire, V.; Rassat, A.; Roux, S.; Seta, P. Chem. Eur. J.
(28) Maggini, M.; Guldi, D. M.; Mondini, S.; Scorrano, G.; Paolucci,
F.; Ceroni, P.; Roffia, S. Chem. Eur. J. 1998, 4, 1992.
(29) Allen, B. D.; Benniston, A. C.; Harriman, A.; Mallon, L. J.;
Pariani, C. Phys. Chem. Chem. Phys. 2006, 8, 4112.
1998, 4, 270.
(59) Amouyal, E.; Mouallem-Bahout, M.; Calzaferri, G. J. Phys. Chem.
1991, 95, 7641.
(60) Horng, M. L.; Gardecki, J. A.; Papazyan, A.; Maroncelli, M. J.
Phys. Chem. 1995, 99, 17311.
(61) Bhasikuttan, A. C.; Suzuki, M.; Nakashima, S.; Okada, T. J. Am.
Chem. Soc. 2002, 124, 8398.
(30) Karlsson, S.; Modin, J.; Becker, H. C.; Hammarstrom, L.;
̈
Grennberg, H. Inorg. Chem. 2008, 47, 7286.
(31) Armaroli, N.; Barigelletti, F.; Ceroni, P.; Eckert, J. F.; Nicoud, J.
F.; Nierengarten, J. F. Chem. Commun. 2000, 599.
(62) Maestri, M.; Armaroli, N.; Balzani, V.; Constable, E. C.; Cargill
Thompson, A. M. W. Inorg. Chem. 1995, 34, 2759.
(32) Sariciftci, N. S.; Wudl, F.; Heeger, A. J.; Maggini, M.; Scorrano,
G.; Prato, M.; Bourassa, J.; Ford, P. C. Chem. Phys. Lett. 1995, 247,
510.
(33) Armspach, D.; Constable, E. C.; Diederich, F.; Housecroft, C.
E.; Nierengarten, J. F. Chem.Eur. J. 1998, 4, 723.
(34) Polese, A.; Mondini, S.; Bianco, A.; Toniolo, C.; Scorrano, G.;
Guldi, D. M.; Maggini, M. J. Am. Chem. Soc. 1999, 121, 3446.
(63) Laine,
252, 2552.
́
P. P.; Campagna, S.; Loiseau, F. Coord. Chem. Rev. 2008,
(64) McClenaghan, N. D.; Leydet, Y.; Maubert, B.; Indelli, M. T.;
Campagna, S. Coord. Chem. Rev. 2005, 249, 1336.
(65) Grewer, C.; Brauer, H.-D. J. Phys. Chem. 1994, 98, 4230.
(66) Winter, A.; van den Berg, A. M. J.; Hoogenboom, R.; Kickelbick,
G.; Schubert, U. S. Synthesis 2006, 2873.
(35) Albinsson, B.; Martensson, J. J. Photochem. Photobiol., C 2008, 9,
̊
138.
(67) Sullivan, B. P.; Calvert, J. M.; Meyer, T. J. Inorg. Chem. 1980, 19,
1404.
(36) Siebert, R.; Winter, A.; Dietzek, B.; Schubert, U. S.; Popp, J.
Macromol. Rapid Commun. 2010, 31, 883.
(37) Siebert, R.; Winter, A.; Schubert, U. S.; Dietzek, B.; Popp, J. J.
Phys. Chem. C 2010, 114, 6841.
(38) Siebert, R.; Hunger, C.; Guthmuller, J.; Schlutter, F.; Winter, A.;
(68) Igartua-Nieves, E.; Ocasio-Delgado, Y.; Torres-Castillo, M. D. L.
́
A.; Rivera-Betancourt, O.; Rivera-Pagan
́ ́
, J. A.; Rodriguez, D.; Lopez,
G. E.; Cortes-Figueroa, J. E. Dalton Trans. 2007, 1293.
́
Schubert, U. S.; Gonzal
2011, 115, 12677.
́
ez, L.; Dietzek, B.; Popp, J. J. Phys. Chem. C
(39) Siebert, R.; Winter, A.; Schubert, U. S.; Dietzek, B.; Popp, J.
Phys. Chem. Chem. Phys. 2011, 13, 1606.
(40) La Rosa, A.; Gillemot, K.; Leary, E.; Evangeli, C.; Gonzalez, M.
́
T.; Filippone, S.; Rubio-Bollinger, G.; Agraït, N.; Lambert, C. J.;
Martín, N. J. Org. Chem. 2014, 79, 4871.
(41) Denholm, A. A.; George, M. H.; Hailes, H. C.; Tiffin, P. J.;
Widdowson, D. A. J. Chem. Soc., Perkin Trans. 1 1995, 541.
(42) Cave, G. W. V.; Raston, C. L. J. Chem. Soc., Perkin Trans. 1 2001,
3258.
(43) Egbe, D. A. M.; Carbonnier, B.; Ding, L. M.; Muhlbacher, D.;
̈
Birckner, E.; Pakula, T.; Karasz, F. E.; Grummt, U. W. Macromolecules
2004, 37, 7451.
(44) Schlutter, F.; Wild, A.; Winter, A.; Hager, M. D.; Baumgartel, A.;
̈
̈
Friebe, C.; Schubert, U. S. Macromolecules 2010, 43, 2759.
(45) Hirsch, A. Synthesis 1995, 895.
(46) Yamada, M.; Akasaka, T.; Nagase, S. Chem. Rev. 2013, 113,
7209.
(47) Winter, A.; Egbe, D. A. M.; Schubert, U. S. Org. Lett. 2007, 9,
2345.
(48) Winter, A.; Friebe, C.; Hager, M. D.; Schubert, U. S. Eur. J. Org.
Chem. 2009, 801.
(49) Maggini, M.; Dono,
Chem. Commun. 1995, 845.
(50) Schulze, B.; Escudero, D.; Friebe, C.; Siebert, R.; Gorls, H.;
̀
A.; Scorrano, G.; Prato, M. J. Chem. Soc.,
̈
Sinn, S.; Thomas, M.; Mai, S.; Popp, J.; Dietzek, B.; Gonzal
Schubert, U. S. Chem. - Eur. J. 2012, 18, 4010.
(51) Sinn, S.; Schulze, B.; Friebe, C.; Brown, D. G.; Jager, M.; Kubel,
́
ez, L.;
̈
̈
J.; Dietzek, B.; Berlinguette, C. P.; Schubert, U. S. Inorg. Chem. 2014,
53, 1637.
(52) Barigelletti, F.; Flamigni, L.; Balzani, V.; Collin, J. P.; Sauvage, J.
P.; Sour, A.; Constable, E. C.; Cargill Thompson, A. M. W. J. Am.
Chem. Soc. 1994, 116, 7692.
(53) Lukoyanova, O.; Cardona, C. M.; Altable, M.; Filippone, S.;
́
Martín Domenech, A.; Martín, N.; Echegoyen, L. Angew. Chem., Int.
Ed. 2006, 45, 7430.
(54) Hirsch, A.; Brettreich, M. Fullerenes; Wiley-VCH: Weinheim,
Germany, 2005.
M
DOI: 10.1021/ic502431x
Inorg. Chem. XXXX, XXX, XXX−XXX