"This is the peer reviewed version of the following article: Highly Efficient Binuclear Ruthenium Catalyst
for Water Oxidation,which has been published in final form at
http://onlinelibrary.wiley.com/doi/10.1002/cssc.201403344/abstract
This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for SelfArchiving."

Highly Efficient Binuclear Ruthenium Catalyst for Water Oxidation
Anett C. Sander[a], Somnath Maji[b], Laia Francàs[b], Torben Böhnisch[a], Sebastian Dechert[a], Antoni
Llobet,[b]* Franc Meyer[a]*

Abstract: Water splitting is one of the key steps in the conversion of
sunlight into a usable renewable energy carrier such as dihydrogen
or more complex chemical fuels. Developing rugged and highly
efficient catalysts for the oxidative part of water splitting, the water
oxidation reaction generating dioxygen, is a major challenge in the
field. Herein we introduce a new, and rationally designed,
pyrazolate-based diruthenium complex with the highest activity in
water oxidation catalysis for binuclear systems reported to date.
Single crystal X-ray diffraction showed favorable preorganization of
the metal ions, well suited for binding two water molecules at a
distance adequate for O-O bond formation, and redox titrations as
well as spectro-electrochemistry allowed for characterization of the
system in several oxidation states. Low oxidation potentials reflect
the trianionic character of the elaborate compartmental pyrazolate
ligand furnished with peripheral carboxylate groups. Water oxidation
has been mediated both with a chemical oxidant (CeIV) - using
manometry and a Clark electrode for monitoring the dioxygen
production - and electrochemically, with impressive activities.

The world’s energy consumption is predicted to increase from
2010 to 2040 by 56 %.[1] Diminishing fossil energy resources
make new technologies a necessity to meet future energy
demands. Thus, the exploitation of renewable energy sources is
of prime interest in chemical research today. In nature,
photosynthesis uses solar energy to split water, generating
protons and reducing equivalents for the production of organic
material. Its artificial emulation is expected to yield energy rich
organic material and dihydrogen as future energy carriers.[2] The
oxidative half reaction of water splitting, viz. the generation of
dioxygen, is usually considered a bottleneck in this endeavor,
since it represents a thermodynamically and kinetically
demanding 4e–/4H+ process.[3] Today the quest for efficient
catalysts for water oxidation (WOCs) remains to be one of the

[a]

[b]

A. C. Sander, T. Böhnisch, Dr. S. Dechert, Prof. Dr. F. Meyer
Institute of Inorganic Chemistry, Georg-August-University Göttingen
Tammannstraße 4, 37077 Göttingen (Germany)
franc.meyer@chemie.uni-goettingen.de
www.meyer.chemie.uni-goettingen.de
Dr. S. Maji, Dr. L. Francàs, Prof. Dr. A. Llobet
Institute of Chemical Research of Catalonia (ICIQ)
Av. Països Catalans 16, 43007 Tarragona (Spain)
allobet@iciq.cat
Supporting information for this article is given via a link at the end of
the document.

major research challenges in this field.
Binuclear ruthenium complexes have attracted much interest as
WOCs,[4,5] starting with T. J. Meyer’s so-called Blue Dimer.[6] A
significant advance was the use of a compartmental pyrazolate
bridging ligand for preorganizing in close proximity the two metal
ions in [{Ru(trpy)}2(µ-Hbpp)(µ-OAc)]3+ (Figure 1, A(µ-OAc)2+).[7]
We recently reported a further elaboration of that motif by
introducing
a
bis(terdentate)
pyrazolate
scaffold
in
[{Ru(py)2}2(µ-Mebbp)(µ-OAc)]2+ (B(µ-OAc)2+) and its highly water
soluble derivative [{Ru(py-SO3)2}2(µ-Mebbp)(H2O)2]2+ (B’(H2O)2-),
which is a rugged and quite efficient WOC.[8] The related
binuclear complex [{Ru(pic)2}2(µ-dabpphtha)(Cl)]+ (D(µ-Cl)+)
introduces two anionic carboxylic groups in its ligand structure,
but at the same time forfeits the beneficial effect of the anionic
pyrazolate bridge by using the neutral phthalazine unit instead.[9]
Despite these developments, however, the existing binuclear
catalysts are still far from reaching nature’s photosynthetic WOC
efficiency. In 2012, the mononuclear ruthenium complexes
[{Ru(pic)2}(bpa)] (C(pic)) and [{Ru(isoq)2}(bpa)] (C(isoq)) were
reported to reach turn over frequencies (TOFs) of 32 sec-1 and
303 sec-1 under the conditions used in that work,[10] which comes
close to the performance of nature’s oxygen evolving complex
(OEC, TOF ≈ 300 sec-1).[11] Most recently, exceptionally fast
WOCs with initial TOF’s close to one thousand per second have
been developed, namely cobalt complexes containing
polyoxometalate ligands and related Ru-bpa complexes.[12,13]
The ligand system in C comprises two carboxylic groups that
lower the oxidation potential of the ruthenium center. Since in
the catalytic cycle a dimerization process has been
proposed,[10,13,14] we surmised that preorganizing two ruthenium
ions in a pyrazolate-based binuclear complex with metal
coordination environments akin to C and D(µ-Cl)+ might give a
catalyst with most favorable properties.

2+
N

2+

N
N

N

N
Ru

N N
O

O

N

N
Ru

N

N

N

O

O

Ru
N

Cl

O

O
N

O

N

N

N
Ru
N

O

Ru

N
O

N

O

N

[{Ru(pic)2}(bda)]
C(pic)
-

N
N N
Ru
OH2
H2O
N
SO3

[{Ru(pic)}2(µ-dabpphtha)(µ-Cl)]+
D(µ-Cl)+

N

N

N

N
N

Ru

O

O3S

O3S

N
N N

N N
O

[{Ru(py)2}2(µ-Mebbp)(µ-OAc)]2+
B(µ-OAc)2+
+

N

N
Ru

N

[{Ru(trpy)}2(µ-Hbpp)(µ-OAc)]2+
A(µ-OAc)2+

N

N
Ru

N

N

N

O

N
O

Ru
N

N
O

O

SO3

[{Ru(py-SO3)2}2(µ-Mebbp)(H2O)2]B'(H2O)2-

[{Ru(isoq)2}(bda)]
C(isoq)

Figure 1. Ruthenium WOCs from literature discussed in this paper.

To this end we have now designed a new proligand H3L
(Scheme 1; see SI for ligand synthesis) that can be viewed as a
hybrid of the ligands in B(µ-OAc)2+ and D(µ-Cl)+/C. H3L provides,
in its deprotonated form, two rigid and pyrazolate-bridged
terdentate binding sites as well as pronounced anionic character
because of the carboxylate and pyrazolate groups. L3– positions
two Ru ions in a well defined distance and enables them to
simultaneously bind water molecules in close proximity within
the bimetallic pocket, preset for O-O bond formation. As a future
option, axial ligands may be easily varied, e.g. by using
pyridines with different substituents, for tuning the electronic
properties and the solubility of the catalyst.

+

Scheme 1. Synthesis of the new WOC cat .

The synthesis of the new family of complexes [{Ru(py)2}2(µL)(X)] (py is pyridine; X = H2O/Cl for 1, X = µ-dmso for 2+, X = µOAc for 3, X = µ-CH3OHOCH3 for 4 and X = (H2O)2 for cat+) is
depicted in Scheme 1. To avoid the formation of grid like
complexes[15] the ligand H3L has to be added in deprotonated
form very slowly to a solution of Ru(dmso)4Cl2. The intermediate
µ-dmso- and Cl/H2O-bridged complexes, 1 and 2+, were heated
further at reflux in a degassed mixture of ethanol and water with
an excess of NaOAc to yield the catalyst precursor complex 3.
Acetate-bridged 3 can be isolated from the reaction mixture after
solvent evaporation by ··taking advantage of the different
solubility properties of the components. A different route is the
synthesis of a methanol-methanolato bridged complex 4 via
heating the intermediate complexes 1 or 2+ in a mixture of 2 м
NaOH(aq)/methanol (1:1) to reflux over night. The catalyst cat+
is finally generated from its immediate precursors 3 and 4 in
acidic aqueous solution (H2O/CF3SO3H, pH = 1.0) via exchange
of the bridging moiety. Replacement of the acetate bridge under

acidic conditions has been evidenced by NMR studies and ESI
mass spectrometry (see Figures S18 S19).
Characterization of the complexes in solution by NMR shows the
diamagnetic character of the low spin d6 RuII centres (see
Figures S1-S13). In the case of intermediates 1 and 2+ the
spectra reflect the reduced symmetry (Cs) of the complexes,
whereas the spectra of 3 and 4 both feature fewer resonances
because of their apparent C2v symmetry. Complexes 1, 3 and 4
were further characterised by X-ray diffraction (Scheme 1 and
Supporting Information). Similar to the Mebbp- ligand in B(µOAc)2+,[8] L3– spans the two Ru ions and serves as a bismeridional scaffold, and the monodentate pyridines occupy axial
positions. From the crystallographically determined molecular
structure of 4 one can anticipate how the catalyst looks like
under neutral pH conditions; note that the (H3C)O-H···O(CH3)
moiety in 4 is labile and is prone to undergo rapid
methanol/water exchange,[16] and that the resulting complex with
HO-H···OH bridge represents a singly deprotonated form of
cat+.[17] It is also noteworthy that all equatorial atoms originating
from the L3– and OAc- ligands in 3 are situated roughly within a
plane, and hence the RuNNRu torsion angle along the
pyrazolate unit in complex 3 is small (3.6°) which is similar to the
situation in B(µ-OAc)2+ (0.4°).[8] In contrast, the acetate is
strongly tilted and the RuNNRu torsion angle is much larger
(25.4°) in the previously reported catalyst A(µ-OAc)2+.[7] This is
important because in the case of B(µ-OAc)2+ the acetate is
tightly bound and not readily hydrolyzed under acidic conditions.
Exchange of the acetate bridge in cat+ is likely facilitated by the
significantly lower charge of the [{Ru(py)2}2(µ-L)]+ scaffold
compared to [{Ru(py)2}2(µ-Mebbp)]3+. Hydrolysis of the acetate
bridge in 3 is evident from NMR spectroscopy and also in
electrochemical experiments, since both complexes 3 and 4
produce the same cyclic voltammogram (CV) in acidic aqueous
solution (0.1 м triflic acid), reflecting the exchange of their
bridging units and the formation of cat+ under those conditions.
Redox properties of 3, 4, and cat+ were investigated by means
of CV and square wave voltammetry (SQWV).[18] Figure 2 (left)
shows the CVs of 3 and 4 in DCM using 0.1 м NBu4PF6, as
supporting electrolyte. In both cases the CV displays two
chemically reversible waves that are assigned to two
consecutive 1e– steps associated with the RuIIIRuII + 1e– →
RuIIRuII and the RuIIIRuIII + 1e– → RuIIIRuII processes. UV-vis
spectra of all species are reported in the Supporting Information,
Figure S21.

Figure 2. Left: CVs of 3 (bold line) and 4 (dashed line) in DCM, 0.1 м NBu4PF6
+
solution. Right: CV and SQWV of cat in H2O/CF3SO3H (0.1 м, pH = 1.0)
solution.

Redox potentials of the two sequential processes in organic
solvent are compiled in Table 1 together with those of related
mononuclear and dinuclear complexes for comparison. It is
interesting to realize here that for dinculear complexes, the
replacement of two pyridyl donors in A(µ-OAc)2+ and B(µOAc)2+ by two anionic carboxylate groups in the ligand
framework of 3 leads to a huge cathodic shift of around 400-500
mV (compare entries 4, 5 and 7 in Table 1). The very low
potentials of 3 and 4 thus reflect the beneficial effect of the
rationally designed new trianionic binucleating ligand L3–.
Table 1. Redox potentials in organic solvents for complexes 3 and 4 and for
related mononuclear and dinuclear complexes reported in the literature.
entry

E1/2 [V vs. SCE]
Complex

Ref
III,II / II,II

III,III / III,II

0.86 (III/II)

---

19

0.46 (III/II)

---

this work
(Fig. S20)

0.41 (III/II)

---

this work
(Fig. S20)

2+a

0.72

1.04

5, 7a

2+b

0.64

1.04

8

0.66

1.16

9

0.21

0.63

this work

0.64

this work

1

{Ru(trpy)(bpy)(Cl)}

2

C(pic)2

3

C(isoq)2

4

A(µ-OAc)

a

5

B(µ-OAc)

6

D(µ-Cl)

7

3

a

4

a

8
a

a

+c

a

0.06
b

c

DCM: dichloromethane, propylene carbonate, MeCN

The CV of cat+ in aqueous solution at pH = 1.0 (0.1 м triflic acid;
Figure 2 right) shows two chemically reversible redox waves at
0.37 and 0.45 V that are tentatively assigned to two consecutive
one electron oxidations giving RuIIRuIII and RuIIIRuIII species,
respectively. Their one electron nature is corroborated by
chemical redox titrations experiments at pH = 1.0 (see Figure 3,
and Figure S22 in the SI). Redox titrations using
(NH4)2[Ce(NO3)6] (abbreviated as CeIV or CAN; 0.1 eq per 10 µL,
H2O/CF3SO3H, pH 1, 0.1 м) furthermore provide the spectra of
the individual species at oxidation states RuIIRuII, RuIIIRuII and
RuIIIRuIII. Further addition of CeIV generates the RuIVRuIII species
that is not stable for long periods of time under these conditions.

scan rate, CoA is the concentration of substrate (55.56 M for
water) and R is 8.314 J·mol-1K-1. Background corrected CVs of
cat+ at different scan rates (10 – 90 mV⋅s-1) are shown in Figure
4 (left). Now, kcat can be extracted from the plot of icat/id vs.
1/{1+exp[(F/RT)(Eocat-E)]} as shown in Figure 4 (right) and in
Figure S25 in the SI. The largest slope at the very beginning of
the catalytic process gives an impressive value of kcat = 7 ± 4 s-1.
It should be noted that kinetic parameters for catalytic reactions
derived from electrochemical measurements depend on various
details of the experimental procedures, and values from different
studies should be compared only with caution.[21]
20

-5

Figure 3. Redox titration in H2O/CF3SO3H (pH = 1.0; 0.1 м) of cat (5·10 м,
IV
-3
10 mL) using Ce in 0.1 eq steps (5·10 м, in 10 µL steps). Top: UV-vis
II
II
spectra of first (left) and second (right) oxidation (red: [Ru Ru ], green:
III
II]
III
III
[Ru Ru , blue: [Ru Ru ]); bottom: absorption changes at selected
wavelengths (332 nm and 550 nm).

10

𝑅𝑇 0
2.24
𝐶 𝑘
𝑖 𝑐𝑎𝑡
𝐹𝑣 𝐴 𝑐𝑎𝑡
=
𝐹
𝑖𝑑
1 + exp
𝐸0 𝑐𝑎𝑡   − 𝐸
𝑅𝑇

-1

-1

7s

5
0
-5
0,000

0,025

6

5

0,050

υ [V/s]

0,075

0,100

4

0

2

-­‐5

0

0.0

0.2

0.4

0.6

0.8

E 	
  [V ]	
  vs .	
  S C E

Besides the two one electron waves a catalytic peak current
whose foot of the wave appears at 0.92 V is observed in the CV
of cat+ (Figure 2 right); a DPV for cat+ under identical condition
is also included in the right part of Figure 2. The DPV shows two
peaks that coincide with the first two oxidations just described
and two more peaks at 0.94 and 1.07 V that are assigned to two
further consecutive one electron oxidations to generate the
RuIIIRuIV and RuIVRuIV species, respectively. It is interesting to
note here that the latter two redox processes are located just
below the catalytic wave observed in the CV, which suggests
that the RuIVRuIV species is responsible for water oxidation. We
do not know the exact proton content of this species but it can
be tentatively assigned to a bis(oxo) species, [{RuIVO}{ORuIV}],
where 4H+ and 4e– have been removed from the initial
[{RuII(OH2)}{(H2O)RuII}]+ complex, cat+, in close analogy to what
has been observed for the type A and B dinuclear complexes
(compare Figure 1).[7,8]
In order to obtain kinetic information about the catalytic process,
a foot of the wave analysis was carried out to calculate apparent
rate constant kcat. We followed the methodology described by
Saveant et al.[20] which assumes that the rate determining step
(rds) is the last electron transfer step. Under catalytic conditions
eq. (1) is operative,

cat

8

15

i c at/i d

i	
   [µA ]

20

+

10

10

k

25

15

12

[s ]

14

30

1.0

1.2

1.4

0.0

0.1

0.2

0.3

0.4

0.5

1/{1+ ex p [(F /R T )(E

0.6
o

0.7

0.8

0.9

1.0

-­‐E )]
c at

Figure 4. Left: Background corrected CVs in H2O/CF3SO3H (pH = 1.0) at 10-1
90 mV⋅s scan rates. Color codes: magenta, 10; pink, 20; violet, 30; purple,
40; wine, 50; red, 60; orange, 70; yellow, 80; brown, 90 mV/s). Right: foot of
o
the wave analysis plotting icat/id vs. 1/{1+exp[(F/RT)(E ca-E)]} at each scan rate
(same color code). Inset: plot of the different kcat values extracted from the foot
of the wave analysis at each scan rate. The black line represents the average
kcat value.

The catalytic performance of cat+ was also studied chemically in
0.1 M triflic acidic aqueous solutions using CAN as oxidant.
Dioxygen production was simultaneously monitored by
manometry and by a Clark electrode in the gas phase of the
reaction vessel. The system cat+ 0.1 mM/CeIV 10 mM/0.1 M
aqueous triflic acid (total solution volume 2 mL) gives 4.8 µmol of
O2 which corresponds to 24 turn overs (TN) with an impressive
and nearly quantitative oxidative efficiency of 96%, and with an
initial turnover frequency (TOFi) of 1.4 s-1. A second addition of
CeIV to the same solution generates again 4.8 µmol of O2
although the TOFi now is slightly lower (Figure 5 left).

(1)

where E0cat is the standard potential for the catalysis-initiating
redox couple (1.07 V), icat is the current intensity in the presence
of substrate, id is the current intensity in the absence of substrate
(here we approximate this current to the current associated with
the RuIIIRuII/RuIIRuII couple), F is the faraday constant, v is the

Figure 5. Water oxidation catalysis in H2O/CF3SO3H solution (0.1 м, pH = 1.0,
+
-1
IV
V = 2 mL), [cat ] = 0.1 mmol⋅L . Left: two times 100 eq. Ce monitored by
manometry (black line) and oxygen sensor (red line; differences are due to the
slow response time of the Clark electrode in the gas phase of the reaction

data for the first 200 s of catalysis are shown in Figure 5 (right),
and the resulting TOFi data are included in Table 2. It is
interesting to see that cat+ with its new trianionic L3- ligand is by
far the best dinuclear WOC: it is roughly 100 times faster than
A(H2O)23+ (compare entries 4 and 7) and about 18 times faster
than B’(H2O)2- (entry 5). This higher activity of cat+ correlates
with the lowering of redox potentials for the corresponding aqua
species. The same effect has been observed for mononuclear
complexes, as can be seen from Table 2 when comparing
entries 1–3: C(isoq) containing the carboxylate groups is about
570 times faster than [Ru(trpy)(bpy)(H2O)]2+. Finally under
identical conditions C(isoq) seems about 6 times faster than
cat+ although in the absence of the anation effect they show
essentially very similar activity. Because of the potentially
bridging binding mode of the nitrate anion within the bimetallic
pocket, the anation effects cat+ much more strongly than
mononuclear C(isoq).
In conclusion, a rugged diruthenium complex cat+ based on a
new pyrazolate ligand with appended carboxylate groups has
been synthesized and fully characterized, including its
spectroscopic signatures in several oxidation states. The
trianionic character of the pyrazolate-bridged ligand scaffold
imparts very low oxidation potentials, and the new system’s
catalytic performance in water oxidation is found superior to all
previously known diruthenium catalysts and practically identical
to the best mononuclear ones. This study shows how rational
ligand design, founded on the knowledge gained in previous
WOC research, leads to significantly improved catalysts; an
impressive
TOF
of
1.4
s-1
was

vessel), right: manometry data for the first 200 s of catalysis (under identical
+
3+
conditions) of cat (black), A(H2O)2
(blue), B’(H2O)2 (green), C(pic)
(magenta) and C(isoq) (orange).

Consistency of the results with regard to the oxidative efficiency,
obtained after the first and second addition of CeIV, indicates full
integrity of the molecular catalyst, which was further
corroborated by ESI mass spectrometry (see Figure S24). On
the other hand the slight decrease of the TOFi upon the second
CeIV addition is due to the increasing NO3- concentration is
solution, as was proven by repeating the same experiment with
different amounts of NO3– added prior to the start of the catalytic
reaction (see Figure S23 in the SI). This phenomenon is
associated with an anion binding equilibrium (anation; see eq.
(2)) that has also been observed previously for other systems.[4]
The anation phenomenon might also be responsible for a
somewhat lower TOFi in the CAN-mediated reaction compared
to the electrochemically determined kcat (which here coincides
with TOFi).
[Ru

[Ru-OH2 H2O-Ru] + NO3-

O

N
O

+

cat

O

Ru]

+ 2 H2O

(2)

Thermodynamic and kinetic parameters for cat+ and related
mononuclear and dinuclear Ru complexes are collected in Table
2. In order to allow useful comparison, the 1:100 cat+:CeIV
reaction shown in Figure 5 (left) was repeated under exactly the
same conditions for mononuclear C(pic) and C(isoq) as well as
for dinuclear A(H2O)23+ and B’(H2O)2– complexes; manometry

+

Table 2. Redox potentials and TOFi’s in 0.1 M triflic acid pH 1 aqueous solution, for cat and related mononuclear and dinuclear Ru complexes reported in the
literature.
E1/2 [V vs. SCE]
Entry

a

Ref

---

0.015

21,22

b

---

2.8 (32.0 )

d

---

III,II / II,II
1

[Ru(trpy)(bpy)(H2O)]

2+

III,III / III,II

IV,III / III,III

IV,IV / IV,III

0.79 (III/II)

0.98 (IV/III)

1.55 (V/IV)

2

C(pic)2

0.36 (III/II)

b

0.83 (IV/III)

b

1.01 (V/IV)

3

C(isoq)2

0.39 (III/II)

0.85 (IV/III)

1.03(V/IV)

3+

0.58

0.64

0.87

-

0.56

0.86

4

A(H2O)2

5

B’(H2O)2

6

D(µ-Cl)

+

+

7

cat

8

~0.56

OEC-PSII

a

IV

d

~1.01

c

this work (10)

8.6 (303 )

c

this work (10)

1.09

0.013

5, 7a, 23

0.93

1.06

0.068

8

---

---

-- (1.2 )

d

0.37

0.48

0.94

---

---

---

1.4 (7 )

this work

-- (~300)
b

(9)

f

---

IV

IV

e

1.07

[cat] = 0.1 mM, [Ce ] = 10 mM ([cat]:[Ce ] = 1:100) in 0.1M triflic acid aqueous solution; total volume 2 mL;
= 1:3)
c

-1

TOFi [s ]

WOC

(7)

acetone/aqueous triflic acid solution (pH = 1.0) (v:v

IV

[cat] = 0.216 mM, [Ce ] = 0.484 M ([cat]:[Ce ] = 1:2240) in 0.1M triflic acid aqueous solution; total volume 3.7 mL;
IV

mM ([cat]: [Ce ] = 1:40000) in 0.1M triflic acid aqueous solution; total volume 20 mL;

determined for cat+ using CAN as terminal oxidant, which is an
improvement by more than two orders of magnitude compared
to the original pyrazolate-based system A(H2O)23+.[7]

f

d

IV

0.1 M HNO3; [cat] = 0.5 mм, [Ce ] = 20

obtained electrochemically

Understanding the effect of the ligand framework on the catalytic
performance is important, and bimetallic systems preorganized
for O-O bond formation hold much promise for the development
of heterogeneous catalysts with immobilized molecule-based

active sites. Detailed mechanistic studies towards unravelling
the actual O-O bond formation mechanism in cat+ as well as
further elaboration of the growing family of pyrazolate-based
WOCs, including their anchoring on conductive supports, are
currently being pursued in our laboratories.

[16]
[17]
[18]
[19]

Acknowledgements
Support from the German Research Foundation (DFG project
Me 1313/9-1) in the framework of the ERA Chemistry program
and from MINECO (EUI2009-04139, CTQ-2013-49075-R and
SEV-2013-0319) is gratefully acknowledged
Keywords: Water oxidation catalysis • artificial photosynthesis •
ruthenium • binuclear complexes • oxygen evolving complex
[1]

[2]
[3]
[4]

[5]

[6]
[7]

[8]
[9]

[10]
[11]

[12]

[13]

[14]

[15]

L. E. Doman, V. Arora, International Energy Outlook 2013 - Highlights,
U.S. Energy Information Administration – Independent Statistics And
Analysis, Washington, 2013, p. 1.
(a) N. D. McDanie, S. Bernhard, Dalton Trans. 2010, 39, 10021-10030;
(b) N. S. Lewis, D. G. Nocera, PNAS 2006, 103, 15729-15735.
A. Llobet, F. Meyer, Angew. Chem. Int. Ed. 2011, A30-A33.
(a) A. E. Clark, J. K. Hurst, Progr. Inorg. Chem. 2012, 57, 1-54; (b) A.
Llobet, X. Sala, L. Escriche, RSC Energy and Environment
Series 2012, 5, 273-287; (c) S. Romain, L. Vigara, A. Llobet, Acc.
Chem. Res. 2009, 42, 1944-1953; (d) J. J. Concepcion, J. W. Jurss, M.
K. Brennaman, P. G. Hoertz, A. O. T. Patrocinio, N. Y. Murakami Iha, J.
L. Templeton, T. J. Meyer, Acc. Chem. Res. 2009, 42, 1954-1965.
I. Romero, M. Rodríguez, C. Sens, J. Mola, M. R. Kollipara, L. Francàs,
E. Mas-Marza, L. Escriche , A. Llobet, Inorg. Chem. 2008, 47, 18241834.
S. W. Gersten, G. J. Samuels T. J. Meyer, J. Am. Chem. Soc. 1982,
104, 4029-4030.
(a) C. Sens, I. Romero, M. Rodríguez, A. Llobet, T. Parella, J. BenetBuchholz, J. Am. Chem. Soc. 2004, 126, 7798-7799.; (b) J. GarciaAnton, R. Bofill, L. Escriche, A. Llobet, X. Sala, Eur. J. Inorg. Chem.
2012, 4775-4789.
S. Neudeck, S. Maji, I. López, S. Meyer, F. Meyer, A. Llobet, J. Am.
Chem. Soc. 2014, 136, 24-27.
Y. Xu, A. Fischer, L. Duan, L. Tong, E. Gebrielsson, B. Åkermark, L.
Sun, Angew. Chem. 2010, 122, 9118-9121; Angew. Chem. Int. Ed.
2010, 49, 8934 –8937.
L. Duan, F. Bozoglian, S. Mandal, B. Stewart, T. Privalov, A. Llobet, L.
Sun, Nature Chem. 2012, 4, 418-423.
G. C. Dismukes, R. Brimblecombe, G. A. N. Felton, R. S. Pryadun, J. W.
Sheats, L. Spiccia, G. F. Swiegers, Acc. Chem. Res. 2009, 42, 19351943.
H. Lv, J. Song, Y. V. Geletii, J. W. Vickers, J. M. Sumliner, D. G.
Musaev, P. Kögerler, P. F. Zhuk, J. Bacsa, G. Zhu, C. L. Hill, J. Am.
Chem. Soc. 2014, 136, 9268-9271.
(a) L. Wang, L. Duan, Y. Wang, M. S. G. Ahlquist, L. Sun, Chem.
Commun., 2014, 50, 12947-12950. (b) C. J. Richmond, R. Matheu, A.
Poater, L. Falivene, J. Benet-Buchholz, X. Sala, L. Cavallo, A. Llobet,
Chem. Eur. J. 2014, in press.
(a) Y. Jiang, F. Li, B. Zhang, X. Li, X. Wang, F. Huang, L. Sun, Angew.
Chem. 2013, 125, 3482–3485; Angew. Chem. Int. Ed. 2013, 52, 33983401.
(a) J. I. van der Vlugt, S. Demeshko, S. Dechert, F. Meyer, Inorg. Chem.
2008, 47, 1576-1585; (b) B. Schneider, S. Demeshko, S. Dechert, F.
Meyer, Angew. Chem. 2010, 122, 9461-9464; Angew. Chem. Int. Ed.

[20]
[21]
[22]

[23]
[24]

2010, 49, 9274-9277; (c) B. Schneider, S. Demeshko, S. Neudeck, S.
Dechert, F. Meyer, Inorg. Chem. 2013, 52, 13230−13237.
S. V. Kryatov, E. V. Rybak-Akimova, F. Meyer, H. Pritzkow, Eur. J.
Inorg. Chem. 2003, 1581-1590.
F. Meyer, P. Rutsch, Chem. Commun. 1998, 1037-1038.
all redox potentials reported in this work are against the SCE reference
electrode
N. Planas, T. Ona, L. Vaquer, P. Miro, J. Benet-Buchholz, L. Gagliardi,
C. J. Cramer, A. Llobet, Phys. Chem. Chem. Phys. 2011, 13, 1948019484.
C. Costentin, S. Drouet, M. Robert, J.-M. Saveant, J. Am. Chem. Soc.
2012, 134, 11235-11242.
E. S. Rountree, B. D. McCarthy, T. T. Eisenhart, J. L. Dempsey Inorg.
Chem. 2014, 53, 9983-10002.
D. J. Wasylenko, C. Ganesamoorthy, M. A. Henderson, B. D. Koivisto,
H. D. Osthoff, C. P. Berlinguette, J. Am. Chem. Soc. 2010, 132, 1609416106.
S. Maji, I. López, F. Bozoglian, J. Benet-Buchholz, A. Llobet, Inorg.
Chem. 2013, 52, 3591-3593.
F. Bozoglian, S. Romain, M. Z. Ertem, T. K. Todorova, C. Sens, J. Mola,
M. Rodríguez, I. Romero, J. Benet-Buchholz, X. Fontrodona, C. J.
Cramer, L. Gagliardi, A. Llobet, J. Am. Chem. Soc. 2009, 131, 1517615187.

Entry for the Table of Contents

COMMUNICATION
A new binuclear ruthenium water
oxidation catalyst is presented that
combines
multiple
beneficial
structural elements for lowering the
metal
ions’
redox
potentials,
enhancing catalyst durability and
favoring the catalytic process. This
leads to an impressive TOF of 1.4 s-1
in CeIV-mediated water oxidation and
high electrocatalytic activity (kcat = 7 ±
4
s-1).
Spectroscopic
and
electrochemical signatures reflect the
well-designed molecular properties.

L

Anett C. Sander[a], Somnath Maji[b], Laia
Francàs[b], Torben Böhnisch[a],
Sebastian Dechert[a], Antoni Llobet, [b]*
Franc Meyer[a]*
Page No. – Page No.

Ru
N
O
C

A Highly Efficient Binuclear
Ruthenium Catalyst for Water
Oxidation