A photoredox catalysed Heck reaction: Via hole transfer from a Ru(ii)-bis(terpyridine) complex to graphene oxide

Article abstract of DOI:10.1039/d0ra08749a

The attachment of homoleptic Ru bis-terpy complexes on graphene oxide significantly improved the photocatalytic activity of the complexes. These straightforward complexes were applied as photocatalysts in a Heck reaction. Due to covalent functionalization on graphene oxide, which functions as an electron reservoir, excellent yields were obtained. DFT investigations of the charge redistribution revealed efficient hole transfer from the excited Ru unit towards the graphene oxide. This journal is

Full text of DOI:10.1039/d0ra08749a

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PAPER
A photoredox catalysed Heck reaction via hole
transfer from a Ru(II)-bis(terpyridine) complex to
graphene oxide†
Cite this: RSC Adv., 2020, 10, 42930
b
c
Marta Rosenthal,a Jorg K. N. Lindner,
W. Gero Schmidt
Uwe Gerstmann,
*
Armin Meier,d
¨
c
d
and Rene Wilhelm
´
The attachment of homoleptic Ru bis-terpy complexes on graphene oxide significantly improved the
photocatalytic activity of the complexes. These straightforward complexes were applied as
photocatalysts in a Heck reaction. Due to covalent functionalization on graphene oxide, which functions
as an electron reservoir, excellent yields were obtained. DFT investigations of the charge redistribution
revealed efficient hole transfer from the excited Ru unit towards the graphene oxide.
Received 14th October 2020
Accepted 19th November 2020
DOI: 10.1039/d0ra08749a
rsc.li/rsc-advances
these homoleptic complexes are rare.20 Here, we demonstrate
that the attachment of these complexes to graphene oxide results
Introduction
in a highly photocatalytic active material for a Heck reaction, via
a hole transfer from the complex to graphene oxide.
Bis-terpyridine Ru complexes have a very short lifetime of their
excited state1–4 which makes them less appealing for photo-
catalytic applications compared to other organic and metal
organic dyes.5–9 Recently, Schubert and Dietzek were able to
directly show a photoinduced charge-separation between a bis-
Graphene, i.e. single graphite sheets, is a carbon nano-
material.22,23 Since its rst synthesis and analysis in 2004,24 the
number of publications concerning graphene, graphene oxide
(GO) and reduced graphene oxide (reduced GO) has been
exploding. GO can easily be prepared via the oxidation of
graphite and graphene may be obtained via the treatment of
graphite with appropriate solvents or via functionalization.22,23
Over the last few years an increasing number of reports have
described the successful application of graphene/graphene
oxide as promotors in photocatalysis,25 oen doped with
nitrogen26 or in combination with a semiconductor.27–31 In
addition, 3D cross-linked graphene materials have been used in
redox catalytic applications32 and functionalized graphene
quantum dots have emerged for potential applications.33–36
terpyridine Ru complex covalently attached to
a poly-
oxometalate unit.1 In case of an Ir complex with poly-
oxometalate Dietzek et al. showed that rather an increased yield
instead of an increased charge separation is observed.10 Heter-
oleptic bis-terpyridine complexes with a donor and acceptor
unit at each terpyridine moiety have been reported, where the
bis-terpyridine metal center acts mainly as an electron relay.11–14
The latter complexes are considered promising for articial
photosynthetic applications.11,12,15–19 Nevertheless, a higher
synthetic effort towards these complexes is necessary compared
to homoleptic bis-terpyridine complexes. The latter are inter-
esting due to their straightforward synthesis. Furthermore, they
can be used to build linear structures without the danger to
obtain geometric or optical isomers.2,11,12 Yet, just recently
a homoleptic complex has been used to build a photocatalytic
active MOF material for the reduction of carbon dioxide.20
Homoleptic bis-terpyridine iron complexes have been used to
link nanoparticles.21 However, photocatalytic application with
Recently,
photocatalytic
selective
organic
trans-
formations37–41 including homogenous photocatalyzed C–C
cross-coupling reactions under visible-light have attracted
much interest.42–53 Heterogeneous catalytic systems42,54–60 for
C–C cross-coupling reactions have been reported in smaller
numbers. Ligand-free palladium catalysed cross-couplings in
general require higher temperatures.61–63 The photo-assisted
reaction allows to perform the reaction at room temperature.
The application of homoleptic terpyridine complexes would be
of special interest but could not be realized so far.
aDepartment of Chemistry, University of Paderborn, Warburgerstr. 100, 33098
Paderborn, Germany
bDepartment Physics, Experimental Physics, University of Paderborn, Warburgerstr.
100, 33098 Paderborn, Germany
Results and discussion
cDepartment of Physics, Theoretical Physics, University of Paderborn, Warburgerstr.
100, 33098 Paderborn, Germany
In order to create a new photocatalytic system with these
complexes and in order to understand the interaction of this
photoactive moiety and graphene oxide better, we rst synthe-
sized ligand 164 and the homoleptic Ru bis-terpyridine complex
dInstitute of Organic Chemistry, Clausthal University of Technology, Leibnizstr. 6,
38678 Clausthal-Zellerfeld, Germany. E-mail: rene.wilhelm@tu-clausthal.de
† Electronic supplementary information (ESI) available: Experimental details and
analytical data. See DOI: 10.1039/d0ra08749a
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2 according to literature procedures as depicted in Scheme 1.65
A
Thereaer, in order to functionalize GO, its carboxylic acid
UV/vis spectrum in acetonitrile showed a maximum absorption functions were transformed to carboxylic acid chloride with
at 500 nm (see Fig. S2†). The in situ formation of a complex via oxalyl chloride.69 Treatment with complex 2 in the presence of
metal salt addition to GO functionalized with terpyridine DMAP and triethylamine resulted in the new material 3 as
moieties was not considered in order to exclude the possibility depicted in Scheme 1. For a high level of functionalization, GO
of remnant metal salts in the material.66–68 The latter materials and complex 2 were applied in the reaction with a mass ratio of
have already been reported for their potential in the generation 1 : 1. Aer work-up and extensive washing the resulting mate-
of a photocurrent.67,68
rial 3 was obtained and analysed. As can be seen in Scheme 1 it
Scheme 1 Synthesis of [Ru(bis-terpyridine)] complex 2 and functionalized GO material 3.
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is assumed that an irregular network is formed. It consists of
the complex and GO due to the presence of the two aniline
groups in the complex. The material was insoluble in most
solvents except DMSO, where a stable suspension was formed,
and hence a good candidate for a heterogenous photocatalyst.
The material 3 was analysed via Raman, UV-vis, AFM, SEM,
EDX and XRD, which are depicted in the ESI (Page S2–S8).†
Fig. S1† shows the Raman spectrum of 3 in comparison to the
commercially available GO.70 Graphitic materials exhibit
a signicant D-band for sp3-centers and a characteristic G-band
for sp2-centers of carbon atoms. The ratio of the intensities of
the D- and G-band allows to postulate the amount of graphene
layers present in the material. While the GO consists of 16 layers
according to the Raman spectrum the material 3 has a reduced
number of 12 layers. AFM measurements of GO and material 3
are presented in Fig. S5.† A comparison of the two AFM images
shows that the particle size was increased. This can be attrib-
uted to the fact, that the bifunctional complex could connect the
GO sheets to larger particles. However, the sheets are not
forming well dened layers. SEM images of material 3 showed
no uniform structure (Fig. S6†). The edges of the particles are
so and small ber structures. Hence, the morphology of 3 is
different to GO, which can be attributed to the functionalization
with complex 2. An EDX analysis (see Fig. S7 and S8†) showed
that 3 contained ruthenium, nitrogen, uorine and phosphor
from the complex 2 next to carbon and oxygen. XRD spectra
(Fig. S9 and S10†) showed that the typical peak of GO at 13ꢀ
disappeared aer the functionalization. Instead, a very broad
peak between 23–27ꢀ appeared, which is specic for graphene
material. This change indicated the disappearance of epoxide
and carboxylic acid groups in 3. Cyclovoltammetry investiga-
tions failed with material 3.
For a structural characterization in the TEM material 3 was
suspended in ethanol and the suspension dried on a carbon
coated grid. An acceleration voltage of 80 kV was chosen to
provide a good compromise between small beam damage at low
voltages and sufficient lateral resolution. In fact, it turned out
that material 3 was more stable than the supporting carbon foil
of about 10 nm thickness. Graphene oxide is known to exhibit
a crystalline lattice indistinguishable from the one of gra-
phene.71 The high-resolution TEM analysis shows both
agglomerates of small randomly oriented crystalline akes with
irregular shapes and sizes between about 1 and 10 nm (Fig. 1a)
as well as staples of large ordered akes few hundreds of
nanometers in diameter (Fig. 1b). From an evaluation of
contrasts (see ESI Fig. S11†) it can be concluded that one to
three GO sheets are superimposed in Fig. 1b (regions I–III),
where in the region (I) of one single GO layer the lattice fringes
of 11ꢀ00 type planes are visible. The Fourier transform (FFT) of
the entire HRTEM image in Fig. 1b reveals the six-fold symmetry
expected for a graphene lattice (inset in Fig. 1b) within the
experimental errors of ꢁ1ꢀ and lattice plane spacings 5.5%
larger than reported for graphene in ref. 21.72 The FFTs of small
agglomerates of akes turn out to be difficult to interpret, most
likely due to bending effects causing spot broadening and due
to the 3D stacking of nearly 2D crystals resulting in higher order
Laue zone effects.
Fig. 1 Transmission electron microscopy of material 3. (a) HRTEM
image of an agglomerate of flakes, (b) lower magnification HRTEM
image of a stack of larger GO sheets and Fourier transformed image in
the inset. The numbers indicate the numbers of stacked GO sheets. (c)
STEM-HAADF survey image, (d) magnified detail marked in red in (c)
showing the distribution of high-Z elements, (e) magnified section of
the region marked in green in (c) with the position of spectra (1–3), (f)
STEM-EDX spectra taken at points (1–3) in (e). The red arrow in (e)
marks contamination from a previous STEM-EDX line scan.
In Fig. 1(c) and (d) STEM-HAADF images of a particularly
large agglomerate are presented. In this mode, the local image
Ð
intensity is proportional to
Z
ꢂ1.8dt, with Z being the atomic
number and t the specimen thickness; hence a high brightness
shows the presence of large amounts of heavy elements. This is
obviously the case especially at the edges of akes. A STEM-EDX
analysis performed at the same sample gives notoriously small
signals due to the limited beam interaction volume and due to
large specimen contamination rates in the STEM mode,
limiting the maximum signal integration time. Spectra (Fig. 1f)
taken at three sample positions show the presence of ruthe-
nium (Ru-La and Ru-Lb at 2.558 and 2.683 keV, respectively)
exclusively at particularly bright parts of the ake (Fig. 1e, blue
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Table 1 Optimization of the reaction time with 5-wt% 3, Pd(OAc)2,
spot) but not at the reference positions (red and green spots,
Fig. 1e), conrming the preferential presence of Ru at the GO
ake edges.
NEt3 in DMF at 495 nm for 4 and 5 at 20 ꢀ
C
Entry
Time
Conversiona
Finally, the photo-optical behaviour of material 3 was ana-
lysed via UV/vis spectroscopy in DMSO (Fig. S4†). The solvent
was chosen because of the stable suspension of material 3 in
this solvent. An absorption maximum was observed at 510 nm,
which is close to the absorption maximum of the free complex
at 500 nm in acetonitrile. The unfunctionalized GO showed
a strong absorbance in the UV region, which continuously
declined with longer wave length (Fig. S3†).
1
2
3
4
5
6
7
8
9
1 h
3 h
4 h
5 h
<1%
5%
6%
8%
12%
70%
6 h
18 h
22 h
24 h
72 h
80%, E : Z (1 : 0.03)
96%, E : Z (1 : 0.04)
97%, E : Z (1 : 0.1)
The new material 3 was investigated in the Heck reaction of
1-bromo-4-iodobenzene 4 with styrene 5 as shown in Scheme 2.
First, different wave lengths for the reaction were evaluated in
the presence of the heterogenous photocatalyst 3, Pd(OAc)2 and
triethylamine. The highest yield of 60% was obtained with
a cyan LED (495 nm), while a green LED (515 nm) resulted in
a slightly lower yield of 50%. A blue LED (455 nm) gave a low
yield of 34%. The highest yield was obtained with a wave length
which corresponds close to the maximum absorption of the
heterogenous complex 3 in DMSO (510 nm) and the free
complex 2 in acetonitrile (500 nm). All the reactions resulted
exclusively in the E-isomer.
To optimize the reaction conditions the impact of the reac-
tion time was investigated rst as shown in Table 1. It was
observed that conversion starts out slow but accelerates aer an
initial induction period, which could be explained by the time
needed to generate a sufficient amount of Pd(0) species as
indicated in Scheme 3. A reaction time of 24 h offered excellent
results with a conversion of 96% (Table 1, entry 8). In addition,
one reaction time was extended to 72 h in order to evaluate
a possible E : Z conversion (Table 1, entry 9).73 This extension
showed a slight increase in the E : Z ratio from 1 : 0.04 to 1 : 0.1.
Aer the optimized reaction conditions were established,
several control reactions were performed (Table 2). The reaction
was rst repeated in the absence of light, which resulted in only
7% yield (Table 2, entry 2). In order to evaluate the activity of
material 3, a reaction with pure GO instead of 3 was carried out.
A yield of 38% was obtained (Table 2, entry 3). The addition of
GO and Ru complex 2 gave a yield of 53% (Table 2, entry 4),
however, the expected 93% (Table 2, entry 1) were not reached.
Obviously, the formation of a covalent bond between GO and Ru
complex 2 in the material 3 is highly benecial for its catalytic
activity. The absence of material 3 and Pd(OAc)2 gave no
product (Table 2, entry 5).
a
Conversion was determined via 1H-NMR.
isolated without 3, alongside various side products (Table 2,
entry 7). Clearly, both catalytic components are needed in order
to achieve a high yield. Reducing the load of 3 from 5 wt% to
0.5 wt% resulted in a decrease of the yield to 33%.
In order to evaluate the catalytic activity of the material 3
further, the heterogenous catalyst 3 was recovered aer the
reaction and analysed. An SEM measurement revealed that the
material did not change its morphology. However, small
amounts of Pd were detectible via EDX. Nevertheless, the
recovered material 3 without the addition of Pd(OAc)2 resulted
in only 18% yield when applied in the reaction. When the
reaction was performed with the recycled material and the
normal addition of Pd(OAc)2 the same yield as in the beginning
could be achieved. Hence, the photocatalytic activity of material
3 was not compromised aer the recycling.
When Pd(OAc)2 was omitted from the reaction, only 18%
yield were observed (Table 2, entry 6) while a yield of 30% was
Scheme 3 One possible mechanism for the photocatalytic cycle
Scheme 2 Heck reaction with 4 and 5.
based on an SET.
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Table 2 Control reactions with 5 wt% photocatalytic additive 3,
Pd(OAc)2, NEt3 in DMF at 495 nm for 24 h with 4 and 5 at 20 ꢀ
C
Entry
Conditions
Yielda
1
2
Standard
Dark
93%
7%
3
4
5
6
7
8
9
GO replaced 3, 5 wt%
GO with 2, 5 wt%
Without 3 and Pd(OAc)2
3, without Pd(OAc)2
Without 3
38%
53%
—
18%
30%b
33%
—
0.5 wt% 3
Without NEt3
10
NEt3 replaced with NaOAc
26%
Fig. 2 Frontier orbitals involved in a molecular HOMO–LUMO tran-
sition (intra Ru-4d excitation) for the pure Ru complex (a) and for a Ru
unit functionalized with a GO-flake ((b), C/O ratio of 0.30); for further
examples see ESI.† The electron is transferred from the HOMO (red)
into the LUMO (blue).
a
Isolated yields. b Various side products detected in 1H-NMR.
A possible mechanism is shown in Scheme 3. As supported
by our DFT calculations (see below) it is based on hole transfer
towards the GO. An alternative, rst considered mechanism
would have been that the excited complex 2 transfers its elec-
tron to the GO, and that the resulting Ru(III) species is reduced
with triethylamine. As proposed in a homogenous photo-
assisted Heck reaction,43 the electron enriched GO could
nally transfer its electron to Pd(II) and reduce it to the active
species Pd(0). In Scheme 3 the electron is transferred from the
Ru+ species. Taking into account that the so far proposed
mechanism would need only the light for the formation of Pd(0)
which could then catalyse the reaction in the dark, a control
reaction with material 3 was carried out. The material was rst
irradiated for 2 h with 495 nm light and stirred under exclusion
of light for 24 h which provided a yield of only 6%. This implies
that the catalyst 3 would also be needed to support the oxidative
addition step or the elimination step in the palladium catalysed
cycle. Hence, next to the proposed SET mechanism in Scheme 3,
an additional subsequent transfer of a triplet state from the Ru
unit to GO cannot be ruled out. The excited GO would then act
as a sensitizer and would transfer its energy to the palladium–
olen intermediate, which has not been explicitly depicted in
Scheme 3.
that this charge transfer is almost independent of the O-content
of the attached graphene ake. In Fig. 2b it is exemplarily
shown for an O/C ratio of about 30%: the hole is transferred in
large amount to the GO where it is mainly (de)localized over the
O-free, graphene-like parts of the material. In other words, the
Ru unit serves as an efficient hole pump towards the attached
GO. This mechanism also appears to be robust with respect to
the size of the attached GO ake (see ESI†). Only for very large
GO akes we expect the excited electron to be transferred into
GO related empty states below the molecular LUMO, resulting
in an effective induction of a triplet exciton into the GO. In any
event, the calculations show that the initial excitation step
consists of a hole transfer from the Ru complex to the GO.
This is strong evidence that the photocatalytic cycle is
probably based on a hole transfer and/or an energy transfer of
a triplet state.75,76 The formation of an aryl radical from the
Table 3 Examples with different aryl iodides and olefins
Entrya
Products
Yield
In order to determine the actual mechanism behind the
photo-induced energy transfer, density functional theory (DFT)
simulations of the excitation process have been performed
using the Quantum ESPRESSO package.74 First, the excitation
process of the pure Ru complex is investigated. An efficient
excitation is possible by a HOMO–LUMO transition. Due to the
strong hybridization of the involved Ru-4d states with carbon
(and nitrogen) orbitals, the charge redistribution is not limited
to the Ru ion, but extends over the whole molecular unit (see
Fig. 2a). Upon this excitation an electron from the axial part of
the complex is transferred to the NC cage surrounding the Ru
ion enabling an efficient intra-molecular charge separation. As
suggested by the observed UV/vis-spectra we expect this intra
Ru-4d transition to be also responsible for photoexcitation of
material 3, where the Ru unit is used to functionalize GO (see
Fig. 2b). Here, the hole is further transferred from the axial part
of the Ru complex towards the GO. The LUMO (i.e. the electron)
in contrast remains almost unaffected. It is important to note
1
93% E : Z (1 : 0.1)
2
3
4
99% E : Z (1 : 0.03)
99%
99%, 98%b
5
75%
a
Aryl iodide (0.4 mmol), olen (0.8 mmol), Pd(OAc)2 (1 mol%), 3
(5 wt%), NEt3 (0.8 mmol), DMF (4 mL), rt, 495 nm, 24 h at 20 ꢀC.
b
Additional run with 3.2 mmol aryl iodide.
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iodoarene is not favourable under the reaction conditions.43
A
410 mg (0.39 mmol, 85%) as black crystalline solid. 1H-NMR
control reaction in the presence of TEMPO showed no signi- (700 MHz, CD3CN-d3, TMS): d [ppm] ¼ 4.77 (sbr, 4H, NH2), 6.95–
cant decrease in the yield, supporting the proposed absence of 6.97 (m, 4H, H3000, H5000), 7.14–7.16 (m, 4H, H5, H500), 7.41–7.42 (m,
radical intermediates. The optimized conditions were then 4H, H6, H600), 7.90–7.93 (m, 4H, H4, H400), 8.00–8.02 (m, 4H, H2000,
applied to further aryl iodides and olens. The results are H6000), 8.61 (d, J ¼ 8.0 Hz, 4H, H3, H300), 9.91 (s, 4H, H30, H50). 13C-
summarized in Table 3. Good to excellent yields could be ob- NMR (176 MHz, CD3CN-d3, TMS): d [ppm] ¼ 115.73 (C-3000, C-5000),
tained for each derivative.
120.76 (C-30, C-50), 122.74 (C-1000), 125.16 (C-3, C-300), 128.17 (C-5, C-
500), 129.77 (C-2000, C-6000), 138.76 (C-4, C-400), 149.38 (C-4000), 151.78
(C-6, C-6000), 153.31 (C-40), 156.15 (C-20, C-60), 159.47 (C-2, C-200).
HRMS(ESI): found m/z 375.0907 ([M]+); calc. for [C42H32N8Ru]2+:
Conclusions
In summary, we have shown that the attachment of a Ru bis- 375.0907. Raman n ¼ 1991, 1500–3400 cmꢄ1. FTIR n ¼ 742, 785,
terpy complex 2 on graphene oxide signicantly improved the 826, 1186, 1244, 1412, 1466, 1524, 1599, 3369 cmꢄ1. The spectral
photocatalytic activity of these complexes in a Heck reaction data were consistent with literature values.65
resulting in excellent yields. HAADF-STEM and STEM-EDX
Synthesis of graphene oxide chloride. GO powder (Graph-
measurements show the presence of Ru mainly at the edges itene Ltd.) (5 g) was solved in dry oxalyl chloride (93.3 g,
of GO akes. The improvement of photocatalytic activity is 0.735 mol, 19.5 eq.). Aer the addition of anhydrous DMF (25
attributed to a covalent functionalization to graphene oxide. In mL) the reaction mixture was treated with ultrasonic for 3 h to
principle, the latter can function as an electron sink and give a homogenous suspension. Aerwards the reaction stirred
reservoir. Although a photoinduced dark catalytic cycle could be at 60 ꢀC for 3 d. The residual oxalyl chloride was removed by N2
possible, it was observed that light is needed in order to distillation to give the crude product. Aer drying under
maintain the product. DFT simulations of the photoexcited vacuum GOCOCl was directly conrmed in the amidation
state identify hole transfer from the metal complex moiety to reaction. IR (KBr) n ¼ 801, 1024, 1092, 1263, 1406, 1626, 2349,
the attached GO as the initial step within the photocatalytic 2926, 2961, 3435 cmꢄ1
.
cycle. Hence, we presented a deeper understanding of the
Synthesis of
3
(GO [Ru(terpy-(C4H4NH2))2](PF6)2).
energy transfer between the metal complex 2 and GO.
[Ru(terpy(C4H4NH2))2](PF6)2 (0.28 g, 0.27 mmol), DMAP
(1.48 mg, 0.012 mmol, 0.044 eq.) and NEt3 (1 mL) were dissolved
in a mixture of GOCl (0.2 g) suspended in anhydrous DMF (6 mL).
The reaction mixture was treated with ultrasonic for 3 h to give
a homogenous suspension. Aerwards the reaction stirred at 100 ꢀC
Experimental
Materials and reagents
All reagents such as NEt3 (triethylamine) and DMAP (4- for 3 d. The reaction was quenched by addition of CH2Cl2 (10 mL).
(dimethylamino)-pyridine) and solvents such as DMF (dime- Aerwards the reaction mixture was stirred 2 h in the atmosphere of
thylformamide) were purchased from commercial sources like nitrogen. The crude product was collected by ltration. Aerwards
¨
Fluka AG, Merck AG, Lancaster, Alfa Aesar, Riedel de Haen and the product was washed with deionized water and chloroform
Sigma Aldrich. Unless specied otherwise the reagents were several times. The product was dried under vacuum for 24 h. Yield:
further puried by standard procedures. GO (powder, 0.5–20 0.39 g. Raman n ¼ 1342 (D), 1594 (G) cmꢄ1. ATR (KBr) n ¼ 748, 785,
mm, elemental analysis: C: 55–65 at%, O: 35–45 at%, S: 0–2 837, 1409, 1518, 1602, 1954, 3074, 3386 cmꢄ1
.
at%, N: 0–1 at%) was purchased from Graphitene Ltd. SEM
General procedure for the photoredox catalysed Heck reac-
(Scanning Electron Microscope) measurements were performed tion. All reagents were dried and deoxygenated in the present of
on a NEON 40 from Zeiss, TEM (Transmission Electron Micro- N2-atmosphere. In a general procedure a dry Schlenk tube was
scope) measurements were performed on a JEM-ARM200F charged with aryl iodide (0.4 mmol,
1 eq.), Pd(OAc)2
NEORAM from JOEL. AFM (Atomic Force Microscope) (0.004 mmol, 1 mol%), NEt3 (0.8 mmol, 2 eq.) and 5 wt% of the
measurements were performed on a Veeco Dimension Icon catalyst in DMF (4 mL).The solution was stirred at room
1
from Bruker. H-NMR spectra were measured at room temper- temperature under irradiation of a cyan blue 3 W power LED
ature by Avance 500 and Ascent 700 from Bruker using meth- cooled with a recirculating cooler to 20 ꢀC. Aer 24 h the reaction
anol as internal standard. Fourier transform infrared (FTIR) was quenched by addition of 1 mL water. The crude product was
and attenuated total reection (ATR) spectra were measured washed with water (1 ꢃ 10 mL) and extracted with chloroform (3
with VERTEX 700 by Bruker using monocrystalline NaCl or KBr ꢃ 10 mL). Aer that the organic layer was washed with brine (1 ꢃ
plates. Ligand 1 was prepared according to the literature.64
10 mL), water (3 ꢃ 10 mL) and dried over MgSO4.
Synthesis
of
[(4-([2,20 : 60,200-terpyridin]-40-yl)aniline)
Ru(II)](PF6)2 (2). 4-([2,20 : 60,200-Terpyridin]-40-yl)aniline 1 (0.3 g,
0.93 mmol, 1 eq.) was added to a solution of Ru(III)Cl3$3H2O
Conflicts of interest
(0.61 mmol, 0.6 eq.) in a mixture of 50 mL ethanol/water There are no conicts to declare.
(30 : 20) and reuxed overnight. Excess of NH4PF6 (0.1 g,
0.81 mmol, 0.8 eq.) was added to the reaction mixture and
stirred for 5 h at room temperature. Aer evaporation of
Acknowledgements
ethanol, the resulting salt was washed with water (2 ꢃ 20 mL), The authors would like to thank the DFG (413541925) for
ethanol (2 ꢃ 20 mL) and diethyl ether (2 ꢃ 20 mL). Yield: nancial support. The numerical DFT calculations have been
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performed at the Paderborn Center for Parallel Computing 24 K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang,
(PC2).
Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov,
Science, 2004, 306, 666.
25 Y. Tong, H. Pan, W. Huang, W. Qiu, Z. Ding, C. Xu and
R. Yuan, New J. Chem., 2019, 43, 8741–8745.
Notes and references
¨
1 Y. Luo, M. Wachtler, K. Barthelms, A. Winter, U. S. Schubert 26 A. Savateev and M. Antonietti, ACS Catal., 2018, 8, 9790–
and B. Dietzek, Chem. Commun., 2018, 54, 2970–2973. 9808.
2 K. Barthelmes, M. Sittig, A. Winter and U. S. Schubert, Eur. J. 27 S. Z. Liu, H. Q. Sun, S. M. Liu and S. B. Wang, Chem. Eng. J.,
Inorg. Chem., 2017, 3698–3706. 2013, 214, 298–303.
3 J.-P. Collin, S. Guillerez, J.-P. Sauvage, F. Barigelletti, 28 H. Zhang, X. Lv, Y. Li, Y. Wang and J. Li, ACS Nano, 2010, 4,
L. DeCola, L. Flamigni and V. Balzani, Inorg. Chem., 1991,
30, 4230–4238.
4 S. Chakraborty, T. J. Wadas, H. Hester, R. Schmehl and
R. Eisenberg, Inorg. Chem., 2005, 44, 6865–6878.
5 M. H. Shaw, J. Twilton and D. W. C. MacMillan, J. Org. Chem.,
2016, 81, 6898–6926.
380–386.
29 N. Zhang, M.-Q. Yang, S. Liu, Y. Sun and Y.-J. Xu, Chem. Rev.,
2015, 115, 10307–10377.
30 M.-Q. Yang, N. Zhang, M. Pagliaro and Y.-J. Xu, Chem. Soc.
Rev., 2014, 43, 8240–8254.
31 M. E. Malefane, B. Ntsendwana, P. J. Mafa, N. Mabuba,
U. Feleni and A. T. Kuvarega, ChemistrySelect, 2019, 4,
8379–8389.
6 R. A. Angnes, Z. Li, C. R. D. Correia and G. B. Hammond, Org.
Biomol. Chem., 2015, 13, 9152–9167.
¨
7 I. Ghosh, L. Marzo, A. Das, R. Shaikh and B. Konig, Acc. 32 Y. Lu, Y. Ma, T. Zhang, Y. Yang, L. Wei and Y. Chen, J. Am.
Chem. Res., 2016, 49, 1566–1577.
Chem. Soc., 2018, 140, 11538–11550.
8 Chemical Photocatalysis, ed. B. Konig, De Gruyter, Berlin, 33 T. Scharl, A. Ferrer-Ruiz, A. Saura-Sanmartin, L. Rodriguez-
¨
Boston, 2013.
Perez, M. A. Herranz, N. Martin and D. M. Guldi, Chem.
Commun., 2019, 55, 3223–3226.
34 A. Cadranel, J. T. Margraf, V. Strauss, T. Clark and
D. M. Guldi, Acc. Chem. Res., 2019, 52, 955–963.
35 S. J. Phang and L.-L. Tan, Catal. Sci. Technol., 2019, 9, 5882–
5905.
¨
9 L. Marzo, S. K. Pagire, O. Reiser and B. Konig, Angew. Chem.,
Int. Ed., 2018, 57, 10034–10072.
10 Y. Luo, S. Maloul, S. Schçnweiz, M. Wachtler, C. Streb and
B. Dietzek, Chem.–Eur. J., 2020, 26, 8045–8052.
11 E. Baranoff, J.-P. Collin, L. Flamigni and J.-P. Sauvage, Chem.
Soc. Rev., 2004, 33, 147–155.
¨
¨
36 C. Kutahya, P. Wang, S. Li, S. Liu, J. Li, Z. Chen and
12 V. Duprez, M. Biancardo, H. Spanggaard and F. C. Krebs,
Macromolecules, 2005, 38, 10436–10448.
B. Strehmel, Angew. Chem., Int. Ed., 2020, 59, 3166–3171.
37 J.-Y. Li, Y.-H. Li, M.-Y. Qi, Q. Lin, Z.-R. Tang and Y.-J. Xu, ACS
Catal., 2020, 10, 6262–6280.
¨
13 Y. Luo, M. Wachtler, K. Barthelmes, A. Winter, U. S. Schubert
and B. Dietzek, Chem. Commun., 2019, 55, 5251–5254.
38 N. Zhang, Y. Zhang, M.-Q. Yang and Y.-J. Xu, Curr. Org.
Chem., 2013, 17, 2503–2515.
¨
14 Y. Luo, J. H. Tran, M. Wachtler, M. Schulz, K. Barthelms,
A. Winter, S. Rau, U. S. Schubert and B. Dietzek, Chem. 39 M.-Q. Yangab and Y.-J. Xu, Phys. Chem. Chem. Phys., 2013, 15,
Commun., 2019, 55, 2273–2276.
19102–19118.
15 S. Sinn, B. Schulze, C. Friebe, D. G. Brown, M. Jager, J. Kubel, 40 C. Han, Y.-H. Li, M.-Y. Qi, F. Zhang, Z.-R. Tang and Y.-J. Xu,
¨
¨
B. Dietzek, C. P. Berlinguette and U. S. Schubert, Inorg.
Chem., 2014, 53, 1637–1645.
16 M. Rupp, T. Auvray, E. Rousset, G. M. Mercier, V. Marvaud,
Sol. RRL, 2020, 4, 1900577.
41 C. Han, Z.-R. Tang, J. Liu, S. Jin and Y.-J. Xu, Chem. Sci., 2019,
10, 3514–3522.
D. G. Kurth and G. S. Hanan, Inorg. Chem., 2019, 58, 9127– 42 Q. Gu, Q. Jia, J. Long and Z. Gao, ChemCatChem, 2019, 11,
9134. 669–683.
17 T. Auvray, R. Sahoo, D. Deschenes and G. S. Hanan, Dalton 43 H. Zhang and X. Huang, Adv. Synth. Catal., 2016, 358, 3736–
Trans., 2019, 48, 15136–15143.
3742.
18 A. Winter and U. S. Schubert, ChemCatChem, 2020, 12, 2890– 44 I. Abdiaj, L. Huck, J. M. Mateo, A. d. l. Hoz, M. V. Gomez,
ˆ
´
2941.
19 P. Labra-Vazquez, M. Boce, M. Tasse, S. Mallet-Ladeira,
A. Diaz-Ortiz and J. Alcazar, Angew. Chem., Int. Ed., 2018,
57, 13231–13236.
´
´
´
´
P. G. Lacroix, N. Farfan and I. Malfant, Dalton Trans., 2020, 45 M. O. Konev, T. A. McTeague and J. W. Johannes, ACS Catal.,
49, 3138–3154. 2018, 8, 9120–9124.
20 M. E. Mahmoud, H. Audi, A. Assoud, T. H. Ghaddar and 46 A. Sagadevan and K. C. Hwang, Adv. Synth. Catal., 2012, 354,
M. Hmadeh, J. Am. Chem. Soc., 2019, 141, 7115–7121.
3421–3427.
21 M. R. Dewi, T. A. Gschneidtner, S. Elmas, M. Ranford, 47 M. Majek and A. J. v. Wangelin, Angew. Chem., Int. Ed., 2013,
K. Moth-Poulsen and T. Nann, ACS Nano, 2015, 9, 1434–
52, 5919–5921.
1439.
48 A. Sagadevan, V. P. Charpe and K. C. Hwang, Catal. Sci.
Technol., 2016, 6, 7688–7692.
49 P. Chuentragool, D. Kurandina and V. Gevorgyan, Angew.
Chem., Int. Ed., 2019, 58, 11586–11598.
22 H.-X. Wang, Q. Wang, K.-G. Zhou and H.-L. Zhang, Small,
2013, 9, 1266–1283.
23 S. Eigler and A. Hirsch, Angew. Chem., Int. Ed., 2014, 53,
7720–7738.
42936 | RSC Adv., 2020, 10, 42930–42937
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Paper
RSC Advances
50 X.-J. Wei, I. Abdiaj, C. Sambiagio, C. Li, E. Zysman-Colman, 65 G. D. Storrier, S. B. Colbran and D. C. Craig, J. Chem. Soc.,
J. Alczar and T. Noel, Angew. Chem., Int. Ed., 2019, 58, 13030–
13034.
51 T. E. Schirmer, A. Wimmer, F. Wolfgang, C. Weinzierl and
Dalton Trans., 1997, 3011–3028.
66 D. Zhou, Q.-Y. Cheng, Y. Cui, T. Wang, X. Li and B.-H. Han,
Carbon, 2014, 66, 592–598.
¨
B. Konig, Chem. Commun., 2019, 55, 10796–10799.
67 T. Matsui, M. R. Karim, H. Takehira, M. Nakamura,
R. Ohtani, M. Koinuma and S. Hayami, Chem. Lett., 2016,
45, 365–367.
52 Z.-J. Wang, S. Zheng, E. n. Romero, J. K. Matsui and
G. A. Molander, Org. Lett., 2019, 21, 6543–6547.
53 G.-Z. Wang, R. Shang, W.-M. Cheng and Y. Fu, J. Am. Chem. 68 S. Song, Y. Xue, L. Feng, H. Elbatal, P. Wang,
Soc., 2017, 139, 18307–18312.
54 N. Marina, A. E. Lanterna and J. C. Scaiano, ACS Catal., 2018,
8, 7593–7597.
55 B. W. Crabbe, O. P. Kuehm, J. C. Bennett and G. L. Hallett-
Tapley, Catal. Sci. Technol., 2018, 8, 4907–4915.
C. N. Mooreeld, G. R. Newkome and L. Dai, Angew.
Chem., Int. Ed., 2014, 53, 1415–1419.
69 R. Sekiya, Y. Uemura, H. Murakami and T. Haino, Angew.
Chem., Int. Ed., 2014, 53, 5619–5623.
70 A. C. Ferrari, Solid State Commun., 2007, 143, 47–57.
56 S. Sarina, H.-Y. Zhu, Q. Xiao, E. Jaatinen, J. Jia, Y. Huang, 71 N. R. Wilson, P. A. Pandey, R. Beanland, R. J. Young,
Z. Zheng and H. Wu, Angew. Chem., Int. Ed., 2014, 53,
2935–2940.
I. A. Kinloch, L. Gong, Z. Liu, K. Suenaga, J. P. Rourke,
S. J. York and J. Sloan, ACS Nano, 2009, 3, 2547–2556.
57 A. Eskandari, M. Jafarpour and A. Rezaeifard, Appl. 72 S. Stankovich, D. A. Dikin, G. H. B. Dommett,
Organomet. Chem., 2019, 33, e5093.
58 Z. Zhang, C. R. Rogers and E. A. Weiss, J. Am. Chem. Soc.,
2020, 142, 495–501.
59 S. Rohani, A. Ziarati, G. M. Ziarani, A. Badiei and T. Burgi,
Catal. Sci. Technol., 2019, 9, 3820–3827.
60 X.-W. Guo, C.-H. Hao, C.-Y. Wang, S. Sarina, X.-N. Guo and
X.-Y. Guo, Catal. Sci. Technol., 2016, 6, 7738–7743.
61 X.-Y. Zhou, X. Chen and L.-G. Wang, Synthesis, 2017, 49,
5364–5370.
62 M. Blanco, D. Mosconi, C. Tubaro, A. Biffis, D. Badocco,
P. Pastore, M. Otyepka, A. Bakandritsos, Z. Liu, W. Ren,
S. Agnoli and G. Granozzi, Green Chem., 2019, 21, 5238–5247.
63 M. Mirza-Aghayan, M. Mohammadi, A. Addad and
R. Boukherroub, Appl. Organomet. Chem., 2020, 34, e5524.
64 T. Mutai, J.-D. Cheon, S. Arita and K. Araki, J. Chem. Soc.,
Perkin Trans. 2, 2001, 1045–1050.
K. M. Kohlhaas, E. J. Zimney, E. A. Stach, R. D. Piner,
S. B. T. Nguyen and R. S. Ruoff, Nature, 2006, 442, 282–286.
73 J. Xu, N. Liu, H. Lv, C. He, Z. Liu, X. Shen, F. Cheng and
B. Fan, Green Chem., 2020, 22, 2739–2743.
74 P. Giannozzi, S. Baroni, N. Bonini, M. Calandra, R. Car,
C. Cavazzoni, D. Ceresoli, G. L. Chiarotti, M. Cococcioni,
I. Dabo, A. Dal Corso, S. de Gironcoli, S. Fabris, G. Fratesi,
R. Gebauer, U. Gerstmann, C. Gougoussis, A. Kokalj,
M. Lazzeri, L. Martin-Samos, N. Marzari, F. Mauri,
R. Mazzarello, S. Paolini, A. Pasquarello, L. Paulatto,
C. Sbraccia, S. Scandolo, G. Sclauzero, A. P. Seitsonen,
A. Smogunov, P. Umari and R. M. Wentzcovitch, J. Phys.:
Condens. Matter, 2009, 21, 395502.
75 F. Strieth-Kalthoff, M. J. James, M. Teders, L. Pitzer and
F. Glorius, Chem. Soc. Rev., 2018, 47, 7190–7202.
76 M. Kudisch, C.-H. Lim, P. Thordarson and G. M. Miyake, J.
Am. Chem. Soc., 2019, 141, 19479–19486.
This journal is © The Royal Society of Chemistry 2020
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