Ruthenium(II) Bipyridyl Complexes with C∧C? Cyclometalated Mesoionic Carbene Ligands

Article abstract of DOI:10.1021/acs.organomet.8b00637

The synthesis of four 2,2′-bipyridyl ruthenium(II) complexes with cyclometalating mesoionic 1,2,3-triazolylidene ligands via their respective p-cymene ruthenium(II) precursors is presented. Solid-state structures confirm the formation of the proposed comp

Full text of DOI:10.1021/acs.organomet.8b00637

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Ruthenium(II) Bipyridyl Complexes with C∧C* Cyclometalated
Mesoionic Carbene Ligands
†
‡
,†
̌
́
Johannes Soellner, Ivana Císarova, and Thomas Strassner*
†
̈
Physikalische Organische Chemie, Technische Universitat Dresden, 01069 Dresden, Germany
‡Department of Inorganic Chemistry, Faculty of Science, Charles University Prague, 128 43 Praha 2, Czech Republic
S
* Supporting Information
ABSTRACT: The synthesis of four 2,2′-bipyridyl ruthenium(II) complexes
with cyclometalating mesoionic 1,2,3-triazolylidene ligands via their respective
p-cymene ruthenium(II) precursors is presented. Solid-state structures
confirm the formation of the proposed complexes, which were characterized
by UV/vis and electrochemical experiments as well as time-dependent DFT
calculations including NTO analysis. The title motif shows improved
photophysical properties compared to structurally related ruthenium(II)
complexes with C∧C* cyclometalating imidazole-based N-heterocyclic
carbene ligands. Due to their electronic properties, the presented dyes are
promising candidates for an application in dye-sensitized solar cells.
significant extent. Up to now, the most prominent and efficient
sensitizing molecules are the N3,5 N719,6 and N7497 (“black
dye”) molecules, reaching cell efficiencies >10%. They are
based upon ruthenium(II) complexes bearing carboxy
functionalized polypyridyl as well as thiocyanate ligands.
However, rhodanide ligands are labile, due to their
monodentate nature, and contribute to decomposition
processes of the dye.8 A promising strategy to replace
INTRODUCTION
■
In the last two decades, the global power output increased by
nearly 40%, according to the quinquennial energy statistics
released by the United Nations.1 Managing the balancing act of
stilling the ever-increasing hunger for energy while adjusting its
generation to become more climate friendly is one of the
dominating challenges of the 21st century. An obvious free and
“renewable” alternative to fossil fuels as a source of energy is,
among others, the sun. It is not surprising that solar energy
accounted for approximately 38% of the global power capacity
that was commissioned in 2017, even surpassing fossil fuels in
that respect.2 Current photovoltaic technologies still rely
heavily on inorganic materials, which are expensive to prepare
and process. Problems also arise from their toxicity and low
natural abundance, for example, in the case of CdTe.3 Dye-
sensitized solar cells (DSSCs) with organometallic dyes can
avoid those problems but are still lagging behind in terms of
efficiency compared to established inorganic materials.3
Generally, DSSCs consist of a transparent conductive substrate
that is coated with a semiconductor such as TiO2 to which the
sensitizing dye is adsorbed. Upon excitation of the dye by
sunlight, an electron is injected into the conduction band of
the semiconductor. This process is commonly referred to as
charge separation, since the electron is transported to the
conduction band while the hole remains at the dye.
Subsequently, the oxidized sensitizer molecule needs to be
regenerated, which is usually achieved by the triiodide/iodine
redox couple. The latter is in turn regenerated by the counter
electrode. In order to function efficiently, each part of the
DSSC needs to be carefully optimized and compatible with the
other components. This challenge has been addressed in depth
in a number of reviews.3,4
thiocyanates is the use of cyclometalating phenylpyridine
10
ligands, which was studied by van Koten,9 Gratzel, and
̈
Berlinguette11 (Figure 1, I) among others.12 Following initial
studies by Li13 and Chung,14 Barnard and co-workers15 then
introduced a charge-neutral imidazole based N-heterocyclic
carbene (NHC) ligand to ruthenium bis-2,2-bipyridyl
complexes (Figure 1, II). At the same time, structurally related
tridentate ligands using 1,2,3-triazolylidenes were studied by
Schubert and Berlinguette.16 These C*∧N∧C* pincer type
ligands carry an N-donating pyridine bridge, which is bound to
the backbone of the 1,2,3-triazole moiety. Shortly after, the
group of Albrecht presented ruthenium(II) complexes with the
analogous bidentate ligands.17 Especially the groups of
Berlinguette and Schubert discussed the effect of the mesoionic
carbene (MIC) donors on the photophysical properties of the
resulting ruthenium(II) complexes. The higher σ-donor
strength compared to classical NHCs enables an efficient
3
destabilization of MC states, which in turn leads to longer
excited state lifetimes.16a,b The most recent developments,
which were introduced simultaneously by our group and the
group of Nazeeruddin, feature C∧C* cyclometalating ligands
based on imidazolinylidenes as analogs to phenylpyridines
(Figure 1, III).18 A common goal of these ligand modifications
The efficiency of the solar cell depends on the charge
separation step, and therefore the sensitizer molecule, to a
Received: August 31, 2018
© XXXX American Chemical Society
A
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Scheme 1. Synthesis of the Title Compounds 4a−d via
a
Ruthenium(II) p-Cymene Complexes 3a−d
Figure 1. Recent development of bis-2,2′-bipyridyl ruthenium(II)
complexes with cyclometalating ligands.
a
Reagents and conditions: (i) NaNO2, H2O/HCl, 0 °C; (ii) NaN3, 0
°C to room temperature; (iii) CH3CH2CHO, mCPBA, pyrrolidine,
THF, 50 °C; (iv) MeI, THF, 110 °C; (v) Ag2O, [Ru(p-cymene)Cl2]2,
DCM, 45 °C; (vi) 2,2′-bipyridine, NH4PF6, DMSO, 140 °C.
is to fine-tune the energy levels of the frontier molecular
orbitals (FMOs), particularly of the highest occupied
molecular orbital (HOMO). This is done to tailor the
absorption properties and correctly set the redox potentials
of the dye. Thereby, it can interact optimally with the adjacent
parts of the DSSC.3 In that respect, cyclometalated ruthenium-
(II) complexes with carbene ligands gave promising
results.13,16,17,19
Herein, we report the synthesis of four ruthenium(II)
complexes bearing mesoionic, C∧C* cyclometalating 1,2,3-
triazolylidene ligands. This novel class of sensitizing molecules
is investigated concerning their applicability in DSSCs by UV/
vis and electrochemical experiments, as well as density
functional theory (DFT) calculations. The mesoionic ligands
form complexes with superior spectroscopic properties
compared to their imidazolinylidene analogs as well as to
related C*∧N ligated ruthenium complexes.
Ru(II) p-cymene complexes is visible in the proton NMR
spectra by the appearance of the characteristic septet of the
isopropyl group. The yellow to orange compounds are readily
soluble in polar solvents, such as dimethyl sulfoxide,
acetonitrile, tetrahydrofuran, dichloromethane, and chloro-
form, but tend to decompose in solution within hours or days.
This can be attributed to the lability of the p-cymene ligand,
which is utilized in the following reaction step: the syntheses of
the title complexes is achieved by stirring the compounds 3a−
d with 2,2′-bipyridine in DMSO solution at elevated
temperatures. The reaction is carried out under the exclusion
of light to avoid side reactions induced by the excitation of the
molecule. After precipitation of residual 2,2′-bipyridine by
addition of water, the cationic ruthenium complexes can be
precipitated from the aqueous solution as their respective
hexafluorophosphate salts by the addition of NH4PF6. The
workup of the crude product is again achieved by flash
chromatography of a dichloromethane solution of the
complexes over basic aluminum oxide. Isolation of the
analytically pure complexes 4a−d is accomplished by
subsequent crystallization from dichloromethane/diethyl
ether mixtures.
The compounds form solids of a dark purple to black color
and deep purple solutions in polar solvents like acetonitrile,
DMSO, dichloromethane, and chloroform. At low concen-
trations, the solutions of 4a and 4b appear violet, while 4c and
4d show a violet to red color. In contrast to the p-cymene
complexes, the tris(bidentate) ruthenium complexes 4a−d are
stable in solution over the course of days and weeks without
any apparent decomposition.
Single-crystals of all complexes 4a−d suitable for X-ray
diffraction experiments could be obtained by slow evaporation
of solutions in water/acetone mixtures (Figures 2−5). Upon
crystallization, the ruthenium complexes form dark rhomboid
shaped blocks, which have a tendency to shatter when removed
from the mother liquor. This can be attributed to evaporation
of cocrystallized solvent molecules. Complexes 4a and 4b
RESULTS AND DISCUSSION
■
Synthesis and Characterization. Aryl-1,2,3-triazole
ligand platforms for C∧C* cyclometalation are readily available
from substituted anilines (Scheme 1). The employed
procedure involves the in situ formation of the respective
aryldiazonium salt, which is then reacted with sodium azide to
give the intermediate arylazide. Aryl-1,2,3-triazoles 1a−d are
then synthesized according to a literature procedure, which
selectively introduces a methyl group to the 4-position of the
heterocycle.20 Syntheses of the ligand precursors are concluded
by quarternization of 1a−d using methyl iodide to yield the
respective 1-aryl-3,4-dimethyl-1H-1,2,3-triazolium iodides 2a−
d. Due to the selective blocking of one backbone position in
the 1,2,3-triazole motif, silver(I)-oxide will selectively de-
protonate 2a−d and form the mesoionic carbene, as desired,
adjacent to the aryl moiety. In analogy to a recently published
procedure15,17,21 by our group, addition of [Ru(p-cymene)-
Cl2]2 leads to a transmetalation of the N-heterocyclic ligand to
ruthenium and subsequent cyclometalation into the N-aryl
fragment.22 The analytically pure Ru p-cymene complexes 3a−
d are isolated by flash chromatography of THF solutions of the
complexes over basic aluminum oxide and subsequent
precipitation by addition of n-pentane. The formation of the
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Figure 4. ORTEP3 illustration of the crystal structure of compound
4c. Thermal ellipsoids drawn at 50% probability; H atoms, disordered
acetone, and counterion omitted for clarity.
Figure 2. ORTEP3 illustration of the crystal structure of compound
4a. Thermal ellipsoids drawn at 50% probability; H atoms and
counterion omitted for clarity.
Figure 3. ORTEP3 illustration of the crystal structure of compound
4b. Thermal ellipsoids drawn at 50% probability; H atoms,
cocrystallized H2O, and disordered counterion omitted for clarity.
Figure 5. ORTEP3 illustration of the crystal structure of compound
4d. Thermal ellipsoids drawn at 50% probability; H atoms and
counterion omitted for clarity.
crystallize in the monoclinic space groups P21/n (4a) and C2/c
(4b), while 4c and 4d display a triclinic symmetry in the space
group P1. All structures show the presence of a racemic
̅
mixture of the respective Λ and Δ enantiomers of the
ruthenium(II) complexes.
Table 1. Selected Bond Lengths [Å] and Angles [deg] for
the Crystal Structures of 4a−d
4a
4b
4c
4d
Ru1−C1
Ru1−C6
Ru1−N4
Ru1−N5
Ru1−N6
Ru1−N7
C1−Ru1−C6
2.030(2)
2.060(2)
2.104(2)
2.060(2)
2.047(2)
2.089(2)
79.15(9)
2.0385(17)
2.0626(17)
2.1064(15)
2.0577(14)
2.0529(15)
2.0957(14)
79.62(7)
2.0369(15)
2.0673(15)
2.1045(13)
2.0609(12)
2.0555(12)
2.0916(12)
79.78(6)
2.032(3)
2.054(3)
2.105(3)
2.053(2)
2.055(2)
2.096(2)
79.80(10)
−1.8(3)
All complexes 4a−d show slightly distorted octahedral
coordination geometries around the ruthenium center. This
distortion is mainly a result of the formation of five-membered
metallacycles by the 2,2′-bipyridines as well as the cyclo-
metalating ligands. For example, the C∧C* bite angle C1−
Ru1−C6 ranges from 79.1° to 79.8° in all complexes (Table 1)
and thereby deviates from the ideal value by approximately
11°. The cyclometalating ligand itself remains almost perfectly
planar in all solid-state structures. The corresponding dihedral
C1−N1−C5−C6 displays values from 0.2(3)° for 4a to
−2.8(2)° in 4b. Also, due to the bisheteroleptic nature of the
title complexes, the ruthenium−nitrogen bond lengths are a
valuable probe to assess the donor strength of the C∧C*
cyclometalating ligand. Compared to Ru1−N5/Ru1−N6, the
bond lengths for Ru1−N4 and Ru1−N7 show a significant
C1−N1−C5−C6 0.1(3)
−2.8(2)
0.76(19)
elongation by 0.03−0.05 Å displaying a distinct trans influence
by the carbon donors (Table 1). This effect is strongest for the
Ru1−N4 bond trans to the anionic aryl ligand. These findings
are in good agreement with data reported on other transition
metal complexes bearing C∧C* cyclometalating ligands.18
Generally, the highlighted bond lengths do not exhibit any
C
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significant dependency on the substitution pattern of the
ligands.
highest occupied molecular orbitals to the two lowest
unoccupied molecular orbitals (LUMOs). While the
HOMOs are clearly dominated by the metal with contributions
from the cyclometalating MIC ligand, the LUMOs are almost
exclusively located in the 2,2′-bipyridyl ligands (see ESI,
Tables S1 and S2).
Spectroscopic and Electrochemical Data. Absorption
spectra of all complexes 4a−d were recorded in acetonitrile
solution at a concentration of 5 × 10−5 mol/L to study their
spectroscopic properties. All of the compounds show
structured absorptions up to wavelengths of 650−675 nm.
The slow absorption onset in the low energy range is
characteristic for ruthenium-based sensitizing molecules due
The contributions of the cyclometalating moiety to the
FMOs reflect the observed bathochromic shift in the
experimental absorption spectra observed for 4c and 4d,
compared to 4a and 4b, which is in agreement with recently
published studies.18b In order to visualize these results, the
natural transition orbitals (NTOs) of the three lowest spin-
allowed transitions (oscillator strength ≥0.01) were calculated
(Figure 7). The NTOs show a clear metal-to-ligand charge
transfer process from the ruthenium center to the 2,2′-
bipyridyl ligands. This directed flow of electrons is ideal for the
application of these complexes as sensitizers, since the binding
of the molecules to a TiO2 substrate would be achieved via
carboxylate functions at the 2,2′-bipyridyl ligands. To model
the impact of potential carboxylate functionalizations, we
calculated the respective molecules, again, at the B3LYP/6-
31G(d) level of theory. While the nature of the transitions
remains unchanged in the carboxylate substituted molecule,
the energies of the FMOs are stabilized noticeably and the
absorption onset is red-shifted by roughly 30 nm (see ESI,
Figures S2 and S3).
3
to low energy MLCT transitions. All complexes show three
distinct absorption maxima between 325 and 575 nm, and
their position is dependent on the substitution pattern of the
cyclometalating ligand. For the unsubstituted complex 4a, they
can be found at approximately 380, 500, and 570 nm. The
electron-donating methoxy group in 4b seems to have no
impact on the absorption properties and gives an almost
congruent spectrum. However, an effect of the electronic
modifications in the structures is visible for 4c and 4d, which
carry electron-withdrawing bromine and nitrile substitution,
respectively. Here, the aforementioned absorption bands are
shifted to higher energies by approximately 20 nm. The
absorption maxima recorded below 325 nm, on the other hand,
are identical for all presented complexes.
Compared to recently published, related molecules with
imidazole based C∧C* cyclometalating ligands18 the absorp-
tion spectra of 4a and 4b display a bathochromic shift of about
20 nm, while these of 4c and 4d feature absorptions at very
similar energies (Figure 6). To better understand the
The high energy excitations at around 300 nm can be
attributed by the NTO analysis to consist of π−π*-transitions
at the 2,2′-bipyridyl moieties. This is in accordance with their
independence from substitution effects in the experimental
spectra.
Upon excitation of the low-energy absorption bands (λexc
=
560 nm) in deaerated acetonitrile solutions, we were able to
obtain emission spectra in the near-infrared region of the
electromagnetic spectrum (Figure 6). All complexes 4a−d
display a single, unstructured emission band with emission
maxima at 804 nm (4a), 802 nm (4b), 785 nm (4c), and 776
nm (4d) and thereby reproduce the energetic trends observed
for the absorption spectra.
Cyclic voltammetry (CV) spectra of all title compounds 4a−
d were recorded in degassed acetonitrile solutions. The results
are given in Figure 8 and Table 2 and are converted to E vs
normal hydrogen electrode (NHE) for better comparison (for
full spectra see ESI, Figures S4−S7). Except for the bromine-
substituted complex 4c, all compounds display two reversible
reduction events at approximately −1.41 V and −1.67 V (vs
NHE). These events show no dependency on the substitution
pattern of the cyclometalating MIC ligand, which agrees with
their attribution to stepwise reductions of the 2,2′-bipyridyls
that are characteristic of these ligands.18b Reversible oxidative
events for RuII/RuIII are recorded for all complexes 4a−d in
the range of 0.49 to 0.68 V (vs NHE). Due to the contribution
of the cyclometalating ligands to the HOMO, the electron-
withdrawing substitutions in 4c and 4d result in a higher
oxidation potential compared to the complexes 4a and 4b.
This finding is also in agreement with the shifted absorption
spectra discussed earlier. These experimentally observed trends
are reproduced in the HOMO energies obtained from single
point calculations with the CPCM model (solvent =
acetonitrile). The DFT method underestimates the exper-
imental values by 0.1 V for 4a and 4b, while the absolute
deviation decreases for complexes 4c and 4d with electron-
withdrawing substituents (Table 2).
Figure 6. Absorption (solid) and emission (dashed) spectra for
complexes 4a−d in 5 × 10−5 mol/L acetonitrile solutions.
transitions involved in the absorption processes, time-depend-
ent DFT calculations using several functional/basis set
combinations were employed. Among the screened methods
were the GGA functionals BP86 and PBE, as well as the hybrid
functionals B3LYP and PBE0 together with Pople and Ahlrichs
basis sets. None of the tested combinations describes the
energies of the excitations fully accurately. While the GGA
functionals systematically underestimate the excitation ener-
gies, the hybrid functionals overestimate them (see ESI, Figure
S1). However, the B3LYP/6-31G(d) level of theory gave the
most accurate results, which are given exemplarily for complex
4a in Figure 7. According to the TD-DFT calculations, all low
energy transitions are dominated by excitations from the three
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Figure 7. Comparison of experimental and TD-DFT calculated absorption spectra (half-width at half height = 0.1 eV) of complex 4a. For selected
excitations, the obtained natural transition orbitals (isoval = 0.04) are given as transitions from hole (bottom) to particle (top).
yield the title compounds as hexafluorophosphate salts.
Characterization by solid-state structures confirmed the
proposed binding mode of the cyclometalating ligands. In
UV/vis experiments, the title compounds displayed broad
absorptions with an onset between 650 and 675 nm. This
corresponds to a 20 nm red-shift compared to related
complexes bearing imidazole based C∧C* ligands18 and a
bathochromic shift of more than 100 nm with respect to
known C*∧N complexes with mesoionic triazole ligands.17
Time-dependent DFT calculations in combination with NTO
analysis helped to assign the observed low energy transitions to
MLCT processes with a directed electron transfer from the
ruthenium center/cyclometalating moiety to the 2,2′-bipyridyl
ligands. The contribution of the mesoionic carbene ligand to
the HOMO was visualized by cyclic voltammetry, which
showed a direct influence of the substitution pattern on the
potential of the first oxidative event. All conducted experiments
confirmed the applicability of the presented dyes as sensitizers
in DSSCs.
Figure 8. CV spectra of all title complexes 4a−d in acetonitrile
solution vs NHE (ferrocene used as internal standard, sweep rate =
100 mV/s).
Table 2. Electrochemical Data and Comparison with DFT
Calculated HOMO Energies for All Title Compounds
EXPERIMENTAL SECTION
General. All ruthenium complexes were synthesized in flame-dried
■
a
b
cyclic voltammetry
DFT
glassware under argon atmosphere. Solvents of at least 99.0% purity
were used in all reactions in this study. Dimethyl sulfoxide (DMSO)
was dried using standard techniques, degassed using the freeze−
pump−thaw technique, and stored over molecular sieves (4 Å).
[Ru(p-cymene]Cl2]2 was prepared according to a modified literature
procedure. All other chemicals were obtained from common suppliers
E1/2,red2 [V]
E1/2,red1 [V]
E1/2,ox [V]
EHOMO [V]
4a
4b
4c
4d
−1.67
−1.68
c
−1.40
−1.42
−1.41
−1.40
0.60
0.59
0.66
0.69
0.50
0.49
0.62
0.68
and used without further purification. H, 13C, and 19F spectra were
1
−1.65
a
CVs in acetonitrile referenced internally vs Fc/Fc+ and converted to
E vs NHE by addition of 0.63 V. HOMO eigenvalues converted to E
vs NHE. Irreversible event.
acquired on Bruker NMR Avance 300, Bruker DRX 500, and Bruker
Avance 600 NMR spectrometers. 1H and 13C spectra were referenced
b
internally (1H 7.26 ppm, 13C 77.16 ppm for CDCl3; 1H 2.50 ppm, 13
C
c
39.43 ppm for DMSO-d6). 19F NMR spectra were also referenced
externally against trifluoromethylbenzene (−63.72 ppm vs CCl3F).
Chemical shifts are given in ppm, and coupling constants J in Hz.
Elemental analyses were performed by the microanalytical laboratory
of our institute on a Hekatech EA 3000 Euro Vector elemental
analyzer. Melting points were determined by using a Wagner and
Munz PolyTherm A system and are not corrected.
CONCLUSION
■
We prepared four ruthenium(II) 2,2′-bipyridyl complexes with
cyclometalated 1,2,3-triazolylidene ligands. The synthesis
started from substituted anilines to give the respective 1,2,3-
triazolium ligand precursors. The subsequently prepared
ruthenium(II) p-cymene complexes were used as starting
material in a ligand exchange reaction with 2,2′-bipyridine to
Spectroscopy. All absorption spectra were recorded in acetoni-
trile solutions of the respective complexes with analyte concentrations
of 5 × 10−5 mol/L on a PerkinElmer Lambda 365 UV/vis
E
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spectrophotometer. Prior to emission measurements, the solutions
were purged with argon for 20 min. All emission spectra were
obtained using a Cary Eclipse fluorescence spectrophotometer.
Electrochemistry. Cyclic voltammetry experiments were carried
out using a Biologic SP-150 potentiostat in degassed, dry acetonitrile
solutions, employing a platinum wire counter electrode, a glassy
carbon working electrode, and a Ag/Ag+ pseudo-reference electrode.
All complexes were measured as 0.5 mM solutions along with 0.1 M
supporting electrolyte (N(n-Bu)4ClO4) at a sweep rate of 100 mV/s.
All measurements were internally referenced against Fc/Fc+. The
obtained potentials were converted to E vs NHE via the redox
potential of the Fc/Fc+ couple vs NHE (E = 0.63 V).23
(Ci), 121.9 (CHarom), 119.6 (CHarom), 10.8 (CCH3). GC-MS (EI) m/
+
z (%) = 237 [M+, 7], 208 [M − N2 , 100]. Anal. Calcd for C9H8BrN3:
C 45.40%; H 3.39%; N 17.65%. Found: C 45.54%; H 3.25%; N
17.35%.
Compound 1d. Compound 1d was prepared analogously to 1a at a
50 mmol scale. 4-Aminobenzonitrile (5.907 g, 50 mmol) was
dissolved in 100 mL of aqueous HCl (10%). Sodium nitrate (3.795
g, 55 mmol, 1.1 equiv) and sodium azide (3.901 g, 60 mmol, 1.2
equiv) were added. Later, 3.194 g (55 mmol, 1.1 equiv) of
propionaldehyde, 3.556 g (50 mmol, 1 equiv) of pyrrolidine, and
13.092 g (55 mmol, 1.1 equiv) of 3-chloroperbenzoic acid were used.
Purification via flash column chromatography (isohexanes/ethyl
acetate, 1:2) and subsequent crystallization a from hot isohexanes/
ethyl acetate mixture yielded compound 1d (1.50 g, 16%). Mp 183
Computational Details. The Gaussian1624 package was used to
perform all quantum chemical calculations employing the hybrid
functionals B3LYP25 and PBE0,26 as well as the pure functionals
BP8627 and PBE28 together with 6-31G(d)29 and def2-SVP30 basis
sets. Ruthenium was described by the LANL2DZ ECP and basis set.31
All given structures were verified as true minima by vibrational
frequency analysis and the absence of negative eigenvalues. UV/vis
spectra and electronic transitions were calculated using TD-DFT
methods (singlet, nstates = 50, CPCM, solvent = acetonitrile) as
implemented in the Gaussian16 package. Conversion of energy values
obtained in calculations to E vs NHE according to Eabs [eV] = −4.5
eV − eU (vs NHE).32 Calculated geometries were visualized with
CYLview33 and GaussView.34
1
°C. H NMR in CDCl3 (300 MHz) δ 7.95−7.84 (m, 2H, CHarom),
7.87−7.77 (m, 2H, CHarom), 7.79 (s, 1H, CHtriazole), 2.46 (s, 3H,
CCH3). 13C NMR in CDCl3 (75 MHz) δ 145.1 (Ci), 140.1 (Ci),
134.0 (CHarom), 120.4 (CHarom), 119.0 (CHarom), 117.9 (Ci), 112.1
(Ci), 11.0 (CCH3). GC-MS (EI) m/z (%) = 184 [M+, 13], 156 [M −
+
+
N2 , 43], 155 [M − N2H+, 100], 102 [M − C3H4N3 , 46]. Anal.
Calcd for C10H8N4: C 65.21%; H 4.38%; N 30.42%. Found: C
65.10%; H 4.34%; N 30.39%.
Compound 2a. In a sealed tube, 1.035 g (6.5 mmol) of triazole 1a
and 2.279 g (13 mmol, 2 equiv) of methyl iodide were dissolved in 3
mL of THF. The mixture was stirred at 110 °C for 20 h; the
precipitate was collected and washed with THF and diethyl ether. The
analytically pure product was obtained as a brown solid after drying in
vacuo (1.44 g, 74%). Mp 149 °C. 1H NMR in DMSO-d6 (600 MHz)
δ 9.36 (s, 1H, CHtriazole), 8.01−7.94 (m, 2H, CHPhenyl), 7.78−7.69 (m,
3H, CHPhenyl), 4.33 (s, 3H, NCH3), 2.58 (s, 3H, CCH3). 13C NMR in
DMSO-d6 (151 MHz) δ 141.4 (Ci), 134.7 (Ci), 131.6 (CHarom), 130.4
(CHarom), 127.0 (CHarom), 121.3 (CHarom), 37.3 (NCH3), 8.73
(CCH3). MS (ESI) m/z = 174.0 [M-I]+, 475.0 [2M-I]+. Anal. Calcd
for C10H12IN3: C 39.89%; H 4.02%; N 13.95%. Found: C 40.17%; H
4.06%; N 13.81%.
Synthesis and Characterization. Compound 1a. Compound
1a was prepared analogously to a literature procedure.20 In a 250 mL
round-bottom flask, 2.794 g (30 mmol) of aniline was dissolved in 60
mL of aqueous HCl (10%) and cooled to 0 °C. Sodium nitrite (2.277
g, 33 mmol, 1.1 equiv) in 20 mL of water was added dropwise to this
solution and stirred at 0 °C for 1 h. At this temperature, 2.340 g (36
mmol, 1.2 equiv) of sodium azide was added, and the mixture was
stirred at 0 °C for 4 h. The aqueous phase was extracted with diethyl
ether; the combined organic phase was dried over magnesium sulfate
and concentrated under reduced pressure. The residue was diluted in
THF, 1.917 g (33 mmol, 1.1 equiv) of propionaldehyde and 0.866 g
(30 mmol, 1 equiv) of pyrrolidine were added, and the mixture was
stirred at 50 °C overnight. The solution was cooled to 0 °C; 7.855 g
(33 mmol, 1.1 equiv) of 3-chloroperbenzoic acid was added in small
portions and then stirred for 1 h at room temperature. All volatiles
were removed in vacuo, and the product was isolated by column
chromatography with an eluent mixture of isohexanes/ethyl acetate
(1:1). After evaporation of all volatiles and drying in vacuo, the
analytically pure product was obtained as brown solid (1.41 g, 30%).
Compound 2b. Compound 2b was prepared analogously to 2a.
Triazole 1b (1.041 g, 5.5 mmol) and 2.342 g (16.5 mmol, 3 equiv) of
methyl iodide in 3 mL of THF were used. Yield 1.15 g (63%). Mp
1
213 °C. H NMR in DMSO-d6 (600 MHz) δ 9.26 (s, 1H, CHarom),
7.94−7.83 (m, 2H, CHarom), 7.32−7.19 (m, 2H, CHarom), 4.29 (s, 3H,
NCH3), 3.87 (s, 3H, OCH3), 2.56 (s, 3H, CCH3). 13C NMR in
DMSO-d6 (151 MHz) δ 161.3 (Ci), 141.1 (Ci), 127.8 (Ci), 126.6
(CHarom), 122.9 (CHarom), 115.3 (CHarom), 55.9 (OCH3), 37.6
(NCH3), 8.6 (CCH3). MS (ESI) m/z = 204.0 [M − I]+, 535.0 [2M −
I]+. Anal. Calcd for C11H14IN3O: C 39.90%; H 4.26%; N 12.69%.
Found: C 39.89%; H 4.29%; N 12.65%.
1
Mp 59 °C. H NMR in CDCl3 (300 MHz) δ 7.80 (s, 1H, CHarom),
7.75−7.67 (m, 2H, CHarom), 7.57−7.48 (m, 2H, CHarom), 7.47−7.39
(m, 1H, CHarom), 2.47 (s, 3H, CCH3). 13C NMR in CDCl3 (75 MHz)
δ 143.8 (Ci), 137.0 (Ci), 129.9 (CHarom), 128.9 (CHarom), 120.6
(CHarom), 119.9 (CHarom), 10.7 (CCH3). GC-MS (EI) m/z (%) = 159
Compound 2c. Compound 2c was prepared analogously to 2a.
Triazole 1c (1.548 g, 6.5 mmol) and 1.845 g (13 mmol, 2 equiv) of
methyl iodide in 5 mL THF were used. Yield 1.95 g (79%). Mp 222
+
1
[M+, 5], 131 [M-N2 , 60]. Anal. Calcd for C9H9N3: C 67.91%; H
°C. H NMR in CDCl3 (600 MHz) δ 9.37 (s, 1H, CHtriazole), 8.01−
5.70%; N 26.40%. Found: C 68.04%; H 5.95%; N 26.47%.
7.95 (m, 2H, CHarom), 7.96−7.91 (m, 2H, CHarom), 4.32 (s, 3H,
NCH3), 2.57 (s, 3H, CCH3). 13C NMR in CDCl3 (151 MHz) δ =
141.4 (Ci), 133.9 (Ci), 133.3 (CHarom), 127.1 (CHarom), 124.7 (Ci),
123.3 (CHarom), 37.8 (NCH3), 8.6 (CCH3). MS (ESI) m/z = 252.1
[M − I]+, 254.0 [M − I]+, 633.0 [2M − I]+. Anal. Calcd for
C10H11BrIN3: C 31.61%; H 2.92%; N 11.06%. Found: C 31.68%; H
3.11%; N 11.00%.
Compound 1b. Compound 1b was prepared analogously to 1a. 4-
Methoxyaniline (3.695 g, 30 mmol) was used instead of aniline. The
product was isolated by column chromatography with isohexanes/
1
ethyl acetate (1:2) as eluent mixture (1.19 g, 21%). Mp 71 °C. H
NMR in CDCl3 (300 MHz) δ 7.65 (d, J = 0.8 Hz, 2H, CHtriazole),
7.63−7.57 (m, 2H, CHarom), 7.05−6.95 (m, 2H, CHarom), 3.86 (s, 3H,
OCH3), 2.43 (s, 3H, CCH3). 13C NMR in CDCl3 (75 MHz) δ 159.9
(Ci), 143.7 (Ci), 130.6 (Ci), 122.2 (CHarom), 119.9 (CHarom), 114.9
(CHarom), 55.7 (OCH3), 10.8 (CCH3). GC-MS (EI) m/z (%) = 189
Compound 2d. Compound 2d was prepared analogously to 2a.
Triazole 1d (1.079 g, 5.86 mmol) and 1.680 g (11.7 mmol, 2 equiv)
of methyl iodide in 4 mL of THF were used. Yield 1.51 g (79%). Mp
+
1
(M+, 14), 161 (M − N2 , 100), 146 (M − N2 − Me+, 46). Anal. Calcd
206 °C. H NMR in DMSO-d6 (300 MHz) δ 9.47 (s, 1H, CHarom),
for C10H11N3O: C 63.48%; H 5.86%; N 22.21%. Found: C 63.77%; H
5.99%; N 21.88%.
8.31−8.23 (m, 2H, CHarom), 8.24−8.17 (m, 2H, CHarom), 4.36 (s, 3H,
NCH3), 2.60 (s, 3H, CCH3). 13C NMR in DMSO-d6 (75 MHz) δ
141.6 (Ci), 137.6 (Ci), 134.6 (CHarom), 127.4 (CHarom), 122.2
(CHarom), 117.5 (Ci), 114.0 (Ci), 38.0 (NCH3), 8.7 (CCH3). MS
(ESI) m/z = 199.0 [M − I]+. Anal. Calcd for C 40.51%; H 3.40%; N
17.18%. Found: C 40.81%; H 3.30%; N 17.19%.
Compound 1c. Compound 1c was prepared analogously to 1a. 4-
Bromoaniline (5.161 g, 30 mmol) was used instead of aniline. The
product was isolated by crystallization from a hot mixture of
1
isohexanes and ethyl acetate (1.79 g, 25%). Mp 151 °C. H NMR
in CDCl3 (300 MHz) δ 7.71 (d, J = 0.9 Hz, 1H, CHtriazole), 7.69−7.55
(m, 4H, CHarom), 2.45 (d, J = 0.8 Hz, 3H, CCH3). 13C NMR in
CDCl3 (75 MHz) δ 144.2 (Ci), 136.1 (Ci), 133.0 (CHarom), 122.5
Compound 3a. In a 50 mL round-bottom flask, 0.151 g (0.5
mmol) of triazolium salt 2a and 0.064 g (0.275 mmol, 0.55 equiv) of
silver(I) oxide were suspended in 15 mL of dichloromethane and
F
DOI: 10.1021/acs.organomet.8b00637
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Organometallics
Article
refluxed overnight under the exclusion of light. The mixture was
filtered through a plug of Celite; the filtrate was transferred into a
flame-dried Schlenk tube and purged with argon for 15 min. [Ru(p-
cymene)Cl2]2 (0.153 g 0.25 mmol, 0.5 equiv) and 0.058 g (0.25
mmol, 0.5 equiv) of silver(I) oxide were added, and the reaction was
stirred under argon atmosphere at room temperature for 3 days. The
mixture was filtered through a plug of Celite; the filtrate was collected
and concentrated to dryness. The residue was dissolved in THF and
subjected to flash chromatography using basic aluminum oxide. The
orange colored fraction was collected concentrated in vacuo, and the
analytically pure, yellow to orange product was precipitated by
Compound 3d. Compound 3d was prepared analogously to 3a at a
2.5 mmol scale. Initially, 0.815 g (2.5 mmol) of triazolium salt 2d and
0.319 g (1.38 mmol, 0.55 equiv) of silver(I) oxide were suspended in
50 mL of dichloromethane. Later, 0.765 g (1.25 mmol, 0.5 equiv) of
[Ru(p-cymene)Cl2]2 and 0.290 g (1.25 mmol, 0.5 equiv) silver(I)
1
oxide were added. Yield 228 mg (20%). Mp > 220 °C (dec.). H
NMR in CDCl3 (300 MHz) δ 8.48 (d, J = 1.6 Hz, 1H, CHarom/phenyl),
7.56 (d, J = 8.1 Hz, 1H, CHarom/phenyl), 7.30 (dd, J = 8.1, 1.7 Hz, 1H,
CHarom/phenyl), 5.56 (d, J = 6.0 Hz, 1H, CHarom/cymene), 5.52 (d, J = 5.9
Hz, 1H, CHarom/cymene), 5.45 (d, J = 5.9 Hz, 1H, CHarom/cymene), 5.39
(d, J = 6.7 Hz, 1H, CHarom/cymene), 4.08 (s, 3H, NCH3), 2.74 (s, 3H,
CCH3), 2.27 (sept, J = 6.9 Hz, 1H, CH(CH3)2), 2.00 (s, 3H, CCH3),
1
addition of n-pentane (89 mg, 40%). Mp > 185 °C (dec.). H NMR
in CDCl3 (300 MHz) δ 8.20 (dd, J = 7.4, 1.4 Hz, 1H, CHarom/phenyl),
7.51 (dd, J = 7.6, 1.4 Hz, 1H, CHarom/phenyl), 7.08 (td, J = 7.3, 1.4 Hz,
1H, CHarom/phenyl), 6.98 (td, J = 7.5, 1.4 Hz, 1H, CHarom/phenyl), 5.53
(dd, J = 6.0, 1.3 Hz, 1H CHarom/cymene), 5.45 (dd, J = 5.8, 1.2 Hz, 1H,
CHarom/cymene), 5.39 (dd, J = 5.9, 1.3 Hz, 1H, CHarom/cymene), 5.35 (dd,
J = 5.8, 1.3 Hz, 1H, CHarom/cymene), 4.03 (s, 3H, NCH3), 2.73 (s, 3H,
CCH3), 2.28 (sept, J = 7.2 Hz, 1H, CH(CH3)2), 0.92 (d, J = 6.9 Hz,
3H, CHCH3), 0.85 (d, J = 6.9 Hz, 3H, CHCH3). 13C NMR in CDCl3
(75 MHz) δ 171.1 (Ci), 166.1 (Ci), 145.0 (Ci), 142.1 (CHarom), 141.1
(Ci), 127.4 (CHarom), 122.5 (CHarom), 113.8 (CHarom), 100.9 (Ci),
100.6 (Ci), 90.0 (CHarom/cymene), 87.8 (CHarom/cymene), 87.5
(CHarom/cymene), 84.9 (CHarom/cymene), 36.2 (NCH3), 31.2 (CH-
(CH3)2), 22.9 (CCH3), 22.2 (CCH3), 19.1 (CCH3), 11.3 (CCH3).
MS (ESI) m/z = 408.3 [M − Cl]+, 444.2 [M + H]+, 850.4 [2M −
Cl]+. Anal. Calcd for C20H24ClN3Ru: C 54.23%; H 5.46%; N 9.49%.
Found: C 54.34%; H 5.49%; N 9.41%.
0.91 (d, J = 6.9 Hz, 3H, CCH3), 0.83 (d, J = 6.9 Hz, 3H, CCH3). 13
C
NMR in CDCl3 (75 MHz) δ 172.6 (Ci), 167.5 (Ci), 148.3 (Ci), 145.4
(CHarom), 141.7 (Ci), 126.8 (CHarom), 120.3 (Ci), 113.8 (CHarom),
110.2 (Ci), 102.2 (Ci), 101.4 (Ci), 90.1 (CHarom), 88.4 (CHarom), 88.2
(CHarom), 85.3 (CHarom), 36.5 (NCH3), 31.2 (CH(CH3)2), 22.8
(CCH3), 22.2 (CCH3), 19.1 (CCH3), 11.2 (CCH3). MS (ESI) m/z =
433.3 [M − Cl]+, 496.2 [M + H]+, 486.2 [M + NH4]+, 954.2 [2M +
NH4]+. Anal. Calcd for C21H23ClN4Ru: C 53.90%; H 4.95%; N
11.97%. Found: C 53.80%; H 5.12%; N 11.74%.
Compound 4a. In a flame-dried Schlenk tube, 0.133 g (0.3 mmol)
of ruthenium complex 3a and 0.103 g (0.66 mmol, 2.2 equiv) of 2,2′-
bipyridine were dissolved in 3 mL of DMSO. The reaction was stirred
under argon atmosphere and under the exclusion of light for 20 h at
140 °C. The reaction was cooled to room temperature, 15 mL of
water was added, and the mixture was stored at 8 °C overnight. The
suspension was filtered through a plug of Celite, and 0.062 g (0.375
mmol, 1.25 equiv) of ammonium hexafluorophosphate in 5 mL of
water was added dropwise. After storing at 8 °C overnight, the
precipitate was collected, dissolved in dichloromethane, and dried
over magnesium sulfate. The solution was concentrated in vacuo and
subjected to flash chromatography using basic aluminum oxide. The
dark violet fraction was collected anf again concentrated in vacuo, and
the analytically pure product was slowly precipitated by addition of
Compound 3b. Compound 3b was prepared analogously to 3a at a
2.5 mmol scale. Initially, 0.828 g (2.5 mmol) of triazolium salt 2b and
0.319 g (1.38 mmol, 0.55 equiv) of silver(I) oxide were suspended in
50 mL of dichloromethane. Later, 0.765 g (1.25 mmol, 0.5 equiv) of
[Ru(p-cymene)Cl2]2 and 0.290 g (1.25 mmol, 0.5 equiv) of silver(I)
1
oxide were added. Yield 299 mg (25%). Mp 190 °C. H NMR in
CDCl3 (300 MHz) δ 7.75 (d, J = 2.6 Hz, 1H, CHarom/phenyl), 7.45 (d, J
= 8.5 Hz, 1H, CHarom/phenyl), 6.53 (dd, J = 8.5, 2.6 Hz, 1H,
CHarom/phenyl), 5.51 (dd, J = 5.9, 1.2 Hz, 1H, CHarom/cymene), 5.42 (dd,
J = 5.8, 1.2 Hz, 1H, CHarom/cymene), 5.39 (dd, J = 5.9, 1.2 Hz, 1H,
CHarom/cymene), 5.35 (dd, J = 5.8, 1.2 Hz, 1H, CHarom/cymene), 4.02 (s,
3H, NCH3), 3.88 (s, 3H, OCH3), 2.71 (s, 3H, CCH3), 2.29 (sept, J =
6.9 Hz, 1H, CH(CH3)2), 1.98 (s, 3H, CCH3), 0.92 (d, J = 7.0 Hz, 3H,
CCH3), 0.85 (d, J = 6.9 Hz, 3H, CCH3). 13C NMR in CDCl3 (75
MHz) δ 169.4 (Ci), 167.9 (Ci), 157.9 (Ci), 140.9 (Ci), 139.0 (Ci),
126.6 (CHarom), 114.2 (CHarom), 107.9 (CHarom), 100.9 (Ci), 100.4
(Ci), 89.8 (CHarom), 87.6 (CHarom), 87.5 (CHarom), 85.0 (CHarom),
55.4 (OCH3), 36.0 (NCH3), 31.1 (CH(CH3)2), 22.9 (CCH3), 22.2
(CCH3), 19.1 (CCH3), 11.2 (CCH3). MS (ESI) m/z = 438.3 [M −
Cl]+, 474.2 [M + H]+, 491.2 [M + NH4]+, 911.4 [2M − Cl]+. Anal.
Calcd for C21H26ClN3ORu: C 53.33%; H 5.54%; N 8.88%. Found: C
53.41%; H 5.61%; N 8.72%.
1
diethyl ether (133 mg, 61%). Mp > 325 °C. H NMR in DMSO-d6
(300 MHz) δ 8.66 (d, J = 5.9 Hz, 1H, CHarom), 8.64 (d, J = 5.7 Hz,
1H, CHarom), 8.59 (d, J = 8.2 Hz, 1H, CHarom), 8.55 (d, J = 8.2 Hz,
1H, CHarom), 8.18 (d, J = 5.6 Hz, 1H, CHarom), 8.09−7.91 (m, 3H,
CHarom), 7.92−7.75 (m, 3H, CHarom), 7.66 (d, J = 5.5 Hz, 1H,
CHarom), 7.53 (d, J = 7.6 Hz, 1H, CHarom), 7.51−7.40 (m, 2H,
CHarom), 7.33 (t, J = 6.6 Hz, 1H, CHarom), 7.28 (t, J = 6.6 Hz, 1H,
CHarom), 6.83 (t, J = 7.3 Hz, 1H, CHarom), 6.74 (t, J = 7.1 Hz, 1H,
CHarom), 6.29 (d, J = 7.0 Hz, 1H, CHarom), 3.99 (s, 3H, NCH3), 1.54
(s, 3H, CCH3). 13C NMR in DMSO-d6 (75 MHz) δ 177.3 (Ci), 176.5
(Ci), 156.9 (Ci), 156.2 (Ci), 155.2 (2 Ci), 153.4 (CHarom), 152.9
(CHarom), 148.5 (CHarom), 147.8 (CHarom), 147.1 (Ci), 141.6 (Ci),
136.4 (CHarom), 135.0 (CHarom), 134.5 (CHarom), 133.6 (CHarom),
132.8 (CHarom), 126.5 (CHarom), 126.4 (CHarom), 126.1 (2 CHarom),
123.3 (CHarom), 123.2 (CHarom), 123.0 (CHarom), 122.9 (CHarom),
120.6 (CHarom), 112.6 (CHarom), 35.8 (NCH3), 8.1 (CCH3). 19F
NMR in DMSO-d6 (282 MHz) δ −70.78 (d, J = 711.2 Hz). MS (ESI)
m/z = 586.2 [M − PF6]+. Anal. Calcd for C30H26F6N7PRu: C 49.32%;
H 3.59%; N 13.42%. Found: C 49.25%; H 3.60%; N 13.34%.
Compound 3c. Compound 3c was prepared analogously to 3a at a
2.5 mmol scale. Initially, 0.950 g (2.5 mmol) of triazolium salt 2c and
0.319 g (1.38 mmol, 0.55 equiv) of silver(I) oxide were suspended in
50 mL of dichloromethane. Later, 0.765 g (1.25 mmol, 0.5 equiv) of
[Ru(p-cymene)Cl2]2 and 0.290 g (1.25 mmol, 0.5 equiv) of silver(I)
Compound 4b. Compound 4b was prepared analogously to 4a at a
0.5 mmol scale. Initially, 0.236 g (0.5 mmol) of ruthenium complex
3b and 0.172 g (1.1 mmol, 2.2 equiv) of 2,2′-bipyridine were
dissolved in 4 mL of DMSO. Later, 0.103 g (0.625 mmol. 1.25 equiv)
ammonium hexafluorophosphate in 5 mL of water was added. Yield
1
oxide were added. Yield 511 mg (39%). Mp > 215 °C (dec.). H
NMR in CDCl3 (300 MHz) δ 8.30 (d, J = 2.1 Hz, 1H, CHarom/phenyl),
7.38 (d, J = 8.3 Hz, 1H, CHarom/phenyl), 7.11 (dd, J = 8.3, 2.0 Hz, 1H,
CHarom/phenyl), 5.52 (d, J = 5.9 Hz, 1H, CHarom/cymene), 5.48 (d, J = 5.8
Hz, 1H, CHarom/cymene), 5.42 (d, J = 5.9 Hz, 1H, CHarom/cymene), 5.38
(d, J = 5.9 Hz, 1H, CHarom/cymene), 4.04 (s, 3H, NCH3), 2.72 (s, 3H,
CCH3), 2.27 (sept, J = 7.0 Hz, 1H, CH(CH3)2), 2.00 (s, 3H, CCH3),
0.91 (d, J = 6.9 Hz, 3H, CCH3), 0.84 (d, J = 6.9 Hz, 3H). 13C NMR in
CDCl3 (75 MHz) δ 170.8 (Ci), 169.2 (Ci), 143.9 (Ci), 143.7
(CHarom), 141.3 (Ci), 125.4 (CHarom), 121.1 (Ci), 115.0 (CHarom),
101.9 (Ci), 100.6 (Ci), 89.7 (CHarom), 88.1 (CHarom), 87.7 (CHarom),
85.3 (CHarom), 36.2 (NCH3), 31.2 (CH(CH3)2), 22.8 (CCH3), 22.3
(CCH3), 19.1 (CCH3), 11.2 (CCH3). MS (ESI) m/z = 486.2 [M −
Cl]+, 1061.1 [2M + NH4]+. Anal. Calcd for C20H23BrClN3Ru: C
46.03%; H 4.44%; N 8.05%. Found: C 46.10%; H 4.45%; N 7.97%.
1
251 mg (66%). Mp > 325 °C. H NMR in DMSO-d6 (300 MHz) δ
8.67 (d, J = 5.2 Hz, 1H, CHarom), 8.64 (d, J = 5.0 Hz, 1H, CHarom),
8.58 (t, J = 8.8 Hz, 2H, CHarom), 8.18 (d, J = 5.6 Hz, 1H, CHarom),
8.11−8.02 (m, 1H, CHarom), 7.98 (tt, J = 7.9, 1.5 Hz, 2H, CHarom),
7.91−7.77 (m, 3H, CHarom), 7.65 (d, J = 5.5 Hz, 1H, CHarom), 7.53−
7.40 (m, 3H CHarom), 7.40−7.32 (m, 1H, CHarom), 7.32−7.24 (m,
1H, CHarom), 6.35 (d, J = 8.5 Hz, 1H, CHarom), 5.68 (s, 1H, CHarom),
3.97 (s, 3H, NCH3), 3.47 (s, 3H, OCH3), 1.52 (s, 3H, CCH3). 13C
NMR in DMSO-d6 (75 MHz) δ 157.5 (Ci), 156.8 (Ci), 156.2 (Ci),
155.4 (Ci), 155.2 (Ci), 153.3 (CHarom), 152.8 (CHarom), 148.6
(CHarom), 147.9 (CHarom), 141.4 (Ci), 140.9 (Ci), 135.0 (CHarom),
G
DOI: 10.1021/acs.organomet.8b00637
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134.5 (CHarom), 133.6 (CHarom), 132.9 (CHarom), 126.5 (CHarom),
126.4 (CHarom), 126.2 (CHarom), 126.1 (CHarom), 123.2 (CHarom),
123.0 (CHarom), 122.9 (CHarom), 121.7 (CHarom), 113.1 (CHarom),
104.9 (CHarom), 54.2 (OCH3), 35.6 (NCH3), 8.04 (CCH3). 19F NMR
in DMSO-d6 (282 MHz) δ −70.78 (d, J = 711.4 Hz, PF6). MS (ESI)
m/z = 616.3 [M − PF6]+. Anal. Calcd for C31H28F6N7OPRu: C
48.95%; H 3.71%; N 12.89%. Found: C 48.76%; H 3.88%; N 12.74%.
Compound 4c. Compound 4c was prepared analogously to 4a at a
0.5 mmol scale. Initially, 0.261 g (0.5 mmol) of ruthenium complex 3c
and 0.172 g (1.1 mmol, 2.2 equiv) of 2,2′-bipyridine were dissolved in
5 mL of DMSO. Later, 0.103 g (0.625 mmol, 1.25 equiv) ammonium
hexafluorophosphate in 5 mL of water was added. Yield 194 mg
(48%). Mp > 300 °C. 1H NMR in DMSO-d6 (300 MHz) δ 8.68 (d, J
= 3.2 Hz, 1H, CHarom), 8.66 (d, J = 3.4 Hz, 1H, CHarom), 8.61 (d, J =
4.4 Hz, 1H, CHarom), 8.58 (d, J = 4.4 Hz, 1H, CHarom), 8.15 (dd, J =
5.8, 0.9 Hz, 1H, CHarom), 8.06−7.94 (m, 3H, CHarom), 7.92−7.80 (m,
3H, CHarom), 7.69−7.63 (m, 1H, CHarom), 7.53−7.43 (m, 3H,
CHarom), 7.41−7.35 (m, 1H, CHarom), 7.34−7.26 (m, 1H, CHarom),
7.00 (dd, J = 8.2, 2.2 Hz, 1H, CHarom), 6.30 (d, J = 2.1 Hz, 1H,
CHarom), 3.99 (s, 3H, NCH3), 1.53 (s, 3H, CCH3). 13C NMR in
DMSO-d6 (75 MHz) δ 182.7 (Ci), 176.7 (Ci), 156.8 (Ci), 156.2 (Ci),
155.2 (Ci), 153.5 (CHarom), 153.1 (CHarom), 148.6 (CHarom), 148.0
(CHarom), 146.4 (Ci), 141.9 (Ci), 138.1 (CHarom), 135.4 (CHarom),
135.0 (CHarom), 134.0 (CHarom), 133.6 (CHarom), 126.8 (CHarom),
126.5 (2 CHarom), 126.3 (CHarom), 123.4 (2 CHarom), 123.1 (2
CHarom), 120.5 (Ci), 114.5 (CHarom), 35.9 (CCH3), 8.1 (CCH3). 19F
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*T.S.: tel, (+49)351-463-38571; fax, (+49)351-463-39679; e-
mail, thomas.strassner@chemie.tu-dresden.de.
■
ORCID
Thomas Strassner: 0000-0002-7648-457X
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the ZIH Dresden for the generous allocation of
computational time on their high performance computing
system. We are grateful to David Schleicher for the
development of the synthesis of the ruthenium complexes.
J.S. also thanks the Studienstiftung des Deutschen Volkes for
funding.
REFERENCES
■
−
(1) United States Statistics Division 2015 United Nations Energy
Statistics Yearbook; New York, 2017.
NMR in DMSO-d6 (282 MHz) δ −70.78 (d, J = 711.2 Hz, PF6 ). MS
(ESI) m/z = 664.2 [M − PF6]+, 666.2 [M − PF6]+. Anal. Calcd for
C30H25BrF6N7PRu: C 44.51%; H 3.11%; N 12.11%. Found: C
44.54%; H 3.03%; N 12.13%.
(2) UNEP Frankfurt School of Finance and Management;
Bloomberg New Energy Global Trends in Renewable Energy Investment;
Frankfurt/Main, 2016.
Compound 4d. Compound 4d was prepared analogously to 4a at a
0.35 mmol scale. Initially, 0.164 g (0.35 mmol) of ruthenium complex
3d and 0.120 g (0.77 mmol, 2.2 equiv) of 2,2′-bipyridine were
dissolved in 3 mL of DMSO. Later, 0.072 g (0.438 mmol. 1.25 equiv)
of ammonium hexafluorophosphate in 5 mL of water was added. Yield
251 mg (66%). Mp 229 °C. 1H NMR in DMSO-d6 (300 MHz) δ 8.70
(d, J = 4.2 Hz, 1H, CHarom), 8.68 (d, J = 4.1 Hz, 1H, CHarom), 8.61 (t,
J = 7.4 Hz, 2H, CHarom), 8.12 (d, J = 5.0 Hz, 1H, CHarom), 8.10−7.96
(m, 2H, CHarom), 7.96−7.87 (m, 2H, CHarom), 7.88−7.81 (m, 2H,
CHarom), 7.70−7.64 (m, 2H, CHarom), 7.57−7.44 (m, 2H, CHarom),
7.39−7.33 (m, 1H, CHarom), 7.32−7.25 (m, 2H, CHarom), 6.54 (d, J =
1.8 Hz, 1H, CHarom), 4.03 (s, 3H, NCH3), 1.56 (s, 3H, CCH3). 13C
NMR in DMSO-d6 (75 MHz) δ 180.1 (Ci), 178.8 (Ci), 156.7 (Ci),
156.1 (Ci), 155.1 (2 Ci), 153.6 (CHarom), 153.3 (CHarom), 151.2 (Ci),
148.5 (CHarom), 148.0 (CHarom), 142.2 (Ci), 139.5 (CHarom), 135.5
(CHarom), 135.3 (CHarom), 134.2 (CHarom), 133.8 (CHarom), 126.9
(CHarom), 126.6 (CHarom), 126.4 (CHarom), 124.8 (CHarom), 123.5
(CHarom), 123.4 (CHarom), 123.2 (2 CHarom), 120.1 (Ci), 112.7
(CHarom), 108.6(Ci), 36.1 (NCH3), 8.1 (CCH3). 19F NMR in DMSO-
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d6 (282 MHz) δ −70.78 (d, J = 711.2 Hz, PF6 ). MS (ESI) m/z =
611.3 [M − PF6]+. Anal. Calcd for C31H25F6N8PRu: C 49.28%; H
3.33%; N 14.83%. Found: C 48.95%; H 3.46%; N 14.43%.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00637.
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