2,3-Di(2-pyridyl)-5-phenylpyrazine: A NN-CNN-type bridging ligand for dinuclear transition-metal complexes

Article abstract of DOI:10.1002/asia.201300327

A new bridging ligand, 2,3-di(2-pyridyl)-5-phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN-CNN-type coordination mode. The reaction of dpppzH with cis-[(bpy)₂RuCl₂] (bpy=2,2′-bipyridine) affords monoruthenium complex [(bpy)₂Ru(dpppzH)]²⁺ (12+) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy)₂Ru(dpppz)Ru(Mebip)]³⁺ (23+) was prepared from complex 12+ and [(Mebip)RuCl₃] (Mebip=bis(N- methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy)₂Ru(dpppz)Pt(C≡CPh)]²⁺ (42+) has been prepared from complex 12+, in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λ_max=695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3-di(2-pyridyl)-5,6-diphenylpyrazine.

Full text of DOI:10.1002/asia.201300327

FULL PAPER
DOI: 10.1002/asia.201300327
2,3-Di(2-pyridyl)-5-phenylpyrazine: A NN-CNN-Type Bridging Ligand for
Dinuclear Transition-Metal Complexes
Si-Hai Wu,[a, b] Yu-Wu Zhong,*[a, c] and Jiannian Yao[a]
Abstract: A new bridging ligand, 2,3-
di(2-pyridyl)-5-phenylpyrazine
pyridine), in which one hydrogen atom
on the phenyl ring of dpppzH is lost
and the bridging ligand binds to the
second ruthenium atom in a CNN tri-
dentate fashion. In addition, the RuPt
these complexes have been probed by
using electrochemical and spectroscop-
ic techniques and studied by theoretical
calculations. Complex 12+ is emissive at
room temperature, with an emission
lmax =695 nm. No emission was detect-
ed for complex 23+ at room tempera-
ture in MeCN, whereas complex 42+
displayed an emission at about 750 nm.
The emission properties of these com-
plexes are compared to those of previ-
ously reported Ru and RuPt bimetallic
complexes with a related ligand, 2,3-
di(2-pyridyl)-5,6-diphenylpyrazine.
(dpppzH), has been synthesized. This
ligand was designed so that it could
bind two metals through a NN-CNN-
type coordination mode. The reaction
of dpppzH with cis-[(bpy)2RuCl2]
(bpy=2,2’-bipyridine) affords monoru-
heterobimetallic complex [(bpy)2Ru-
2+
ꢀ
G
(C CPh)]
(42+) has been
prepared from complex 12+, in which
the bridging ligand binds to the plati-
num atom through a CNN binding
mode. The electronic properties of
thenium
complex
[(bpy)2Ru-
ACHTUNGTRENNUNG
which dpppzH behaves as a NN biden-
tate ligand. The asymmetric birutheni-
um complex [(bpy)2RuACHTNUTGRNEUNG(dpppz)Ru-
Keywords: bridging ligands · coor-
ACHTUNGTRENNUNG
(Mebip)]3+ (23+) was prepared from
dination modes
· cyclometalated
complex 12+ and [(Mebip)RuCl3]
(Mebip=bis(N-methylbenzimidazolyl)-
complexes · platinum · ruthenium
Introduction
a great number of linear and rigid molecular assemblies
when bound to octahedral transition-metal ions in a NNN-
NNN bis-tridentate fashion.[5] Another bridging ligand that
The design of polyazine bridging ligands for the construction
of bimetallic or macromolecular coordination assemblies has
received much attention.[1] A “good” bridging ligand should
have a rigid and well-defined geometry and allow optimal
orbital overlap between the metals and the organic ligands.
Because of their appealing photophysical and electrochemi-
cal properties, the resulting bimetallic or multimetallic com-
plexes have been extensively used in a wide range of fields,
such as molecular electronics,[2] electrochromism,[3] and the
photoconversion of solar energy.[4] One of the most exten-
sively studied bridging ligands is 2,3,5,6-tetrakis(2-pyridyl)-
pyrazine (tppz, Scheme 1), which has been shown to yield
[a] S.-H. Wu, Prof. Dr. Y.-W. Zhong, Prof. Dr. J. Yao
Beijing National Laboratory for Molecular Sciences
CAS Key Laboratory of Photochemistry
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (China)
E-mail: zhongyuwu@iccas.ac.cn
Homepage: http://zhongyuwu.iccas.ac.cn/
[b] S.-H. Wu
University of Chinese Academy of Sciences
Beijing 100049 (China)
[c] Prof. Dr. Y.-W. Zhong
State Key Laboratory of Coordination Chemistry
Nanjing University
Nanjing 210093 (China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300327.
Scheme 1. Bridging ligands and the design of new ligand dpppzH.
1504 ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2013, 8, 1504 – 1513

www.chemasianj.org
Yu-Wu Zhong et al.
has received extensive attention is 2,3-bis(2-pyridyl)pyrazine
(dpp). This ligand binds to two metals through a NN-NN-
type coordination mode and is particularly useful for the
construction of macromolecular complexes with multiple
metal centers.[6] Despite the progress in this area, the devel-
opment of new polyazine bridging ligands with comparable
and complementary electronic properties is still of great in-
terest to the materials science and chemistry communities.[1]
Recently, there has been growing interest in the synthesis
CNN-CNN-type coordination modes, depending on whether
the two phenyl rings of dpdpzH2 bind to the metal site or
not. Among these compounds, one interesting example is
ꢀ
the RuPt heterobimetallic complex [(bpy)2RuACTHUNRTGNE(GNU dpdpzH)PtC
CPh]2+ (Scheme 1),[15] where bpy is 2,2’-bipyridine and
dpdpz is the bis-deprotonated form of dpdpzH2. This com-
plex emits near-infrared (NIR) light[17] (lmax =780 nm) with
a quantum yield (f) of 0.15%, which is relatively higher
than that of monoruthenium complex [(bpy)2Ru-
and study of cyclometalated complexes that contain a s M
(dpdpzH2)]2+, which emits at 709 nm (f=0.057%).[14] As
ACHTUNGTRENNUNG
a continuation of this project, we conjectured that the un-
ꢁ
C bond.[7] These complexes either contain a CN-type biden-
tate ligand or a NCN/CNN-type tridentate chelate ligand.
The most studied cyclometalated complexes have been
those that bind to iridium,[8] ruthenium,[9] and platinum
ions.[10] Because of the presence of the anionic carbon
ligand, these complexes exhibit significantly different photo-
physical and electrochemical properties with respect to their
corresponding noncyclometalated complexes. However,
most of these studies have been concerned with monometal-
lic complexes and the design of bridging ligands for the syn-
thesis of cyclometalated dinuclear complexes has been limit-
ed. Some representative examples include NCN-NCN-type
bis-cyclometalating ligands 1,2,4,5-tetra(pyrid-2-yl)benzene
(tpbH2, Scheme 1),[11] 1,3,6,8-tetra(pyrid-2-yl)pyrene,[12] and
others.[13] These ligands have been used for the syntheses of
touched phenyl ring of the bridging ligand in [(bpy)2Ru-
2+
ꢀ
N
freely to provide a non-emissive deactivation pathway. Thus,
a new ligand, 2,3-di(2-pyridyl)-5-phenylpyrazine (dpppzH),
was designed in which this phenyl ring was removed.
Herein, we describe the use of dpppzH as a NN-CNN-type
bridging ligand for the synthesis of RuRu and RuPt bimetal-
lic complexes and electrochemical and spectroscopic studies
of these complexes. In addition, density functional theory
(DFT) and time-dependent DFT (TDDFT) calculations
have been performed to complement these experimental re-
sults.
ꢁ
bis-ruthenium complexes and for studies of metal metal
electronic coupling.
Results and Discussion
Synthesis and Characterization
In addition to these above-mentioned bis-cyclometalating
ligands, we recently reported that 2,3-di(2-pyridyl)-5,6-di-
phenylpyrazine (dpdpzH2, Scheme 1) displayed rich coordi-
nation chemistry with various transition metals, such as
ruthenium,[14] platinum,[15] and rhenium,[16] to yield a number
of monometallic and bimetallic complexes with interesting
electrochemical and spectroscopic properties. In the case of
bimetallic complexes, the bridging ligand and the metal
atoms can either connect through NN-NN, NN-CNN, or
The compounds that were studied herein are shown in
Scheme 2. Ligand dpppzH was prepared by the condensa-
tion of d,l-phenylethylenediamine with 2,2’-pyridil, followed
by subsequent dehydrogenation; d,l-phenylethylenediamine
was prepared according to a literature procedure by the re-
duction of a-azidoacetophenone O-methyl oxime ether with
lithium aluminum hydride.[18] The 1H NMR spectrum of
dpppzH shows a singlet at d=9.11 ppm, which is assigned to
the proton on the pyrazine ring. The reaction of dpppzH
with cis-[(bpy)2RuCl2], followed by anion exchange with
KPF6, gave monoruthenium complex [(bpy)2Ru
AHCTUNGTRENNUNG
ACHTUNGTRENUN(NG dpppzH)]-
(PF6)2 (12+) in 64% yield. The coordination mode between
Abstract in Chinese:
Ru and dpppzH was confirmed by subsequent transforma-
tions.
The treatment of complex 12+ with [(Mebip)RuCl3][19]
(Mebip=bis-(N-methylbenzimidazolyl)pyridine) in the pres-
ence of AgOTf afforded the asymmetric bis-ruthenium com-
(PF6)3 (23+), where dpppz
plex [(bpy)2RuACHTGNUTREN(NGUN dpppz)RuACHTUNRTEGG(NNUN Mebip)]ACHTGUNTRENNUGN
is the mono-deprotonated form of dpppzH. The identity of
complex 23+ was confirmed by mass spectroscopy, single-
crystal X-ray diffraction, and electrochemical studies. The
reaction of monoruthenium complex 12+ with K2PtCl4 in
a mixture of MeCN and water[10] gave the crude hetero-di-
nuclear RuIIPtII complex [(bpy)2Ru (PF6)2 (32+)
ACTHNUTRGENN(UG dpppz)PtCl]ACHUTNGTRENNGUN
in good yield (90%); this crude product was used in a subse-
quent transformation without further purification. The reac-
tion of complex 32+ with phenylacetylene, in the presence of
CuI and triethylamine,[20] afforded platinum-acetylide com-
plex 42+ in 70% yield. The successful synthesis and isolation
Chem. Asian J. 2013, 8, 1504 – 1513
1505
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
Scheme 2. Synthesis of the studied compounds.
of complexes 23+ and 42+ indicate that the [Ru
ponent in complex 12+ binds to the NN side of dpppzH and,
hence, that the open CNN side is available to accommodate
another cyclometalated ion.
AHCTUNGRTENN(GUN bpy)2] com-
the bridging ligand through a Ru C bond. The two rutheni-
ꢁ
ꢁ
um atoms are separated by a Ru Ru distance of 6.78 ꢁ.
ꢁ
The Ru N bonds are associated with the noncyclometalated
Ru1 atom and are within the range 2.04–2.06 ꢁ. In many of
the reported cyclometalated monoruthenium complexes,[19,22]
ꢁ
ꢁ
the Ru C bond is slightly shorter than the Ru N bonds.
Single-Crystal Structures
3+
ꢁ
However, the Ru2 C1 bond in complex 2 has a distance
ꢁ
A single crystal of complex [2]
N
of 2.02 ꢁ, which is longer than the Ru2 N7 (1.96 ꢁ) and
Ru2 N10 bonds (1.99 ꢁ). In addition, the Ru2 N8 bond
(2.18 ꢁ) is much longer relative to other Ru N bonds,
owing to the trans effect of the s Ru2 C1 bond. The two
planes of the pyridine groups with the N5 and N8 atoms
have a torsion angle of 22.18.
ꢁ
ꢁ
ture of MeCN and Et2O; the X-ray structure is shown in
Figure 1.[21] Both ruthenium atoms adopt a distorted octahe-
dral configuration. The Ru1 atom has a tris-bidentate coor-
dination mode, whereas the Ru2 atom has a bis-tridentate
coordination mode and is connected to the phenyl ring of
ꢁ
ꢁ
Electrochemical Studies
The cyclic voltammograms (CVs) of these complexes are
shown in Figure 2. The corresponding electrochemical data
are summarized in Table 1, together with those of some re-
lated complexes for comparison. The anodic scan of mono-
ruthenium complex 12+ shows one RuII/III redox couple at
+1.41 V versus Ag/AgCl, which is comparable to those of
[(bpy)2RuACTHNUTRGENNUG ACHTUNGTRENNGUN
(dpp)]2+ and [(bpy)2Ru(dpdpzH2)]2+.[14] Four
cathodic waves for complex 12+ appear at ꢁ0.96, ꢁ1.43,
ꢁ1.64, and ꢁ1.98 V. The first wave at ꢁ0.96 V is assigned to
the reduction of the dpppzH ligand;[14] the other three
waves cannot be clearly assigned. However, two of these
waves must be associated with the reductions of two bpy li-
gands. The further reduction of dpppzH ligand may be re-
sponsible for the remaining wave.
Figure 1. Single-crystal X-ray structure of complex [2]ACHTNUGTRNEG(UN PF6)3; thermal el-
lipsoids are set at 30% probability. Counteranions and hydrogen atoms
are omitted for clarity. Selected bond lengths [ꢁ]: Ru1–Ru2 6.78, Ru1–
N1=Ru1–N2=Ru1–N5=Ru1–N6 2.06, Ru1–N3 2.05, Ru1–N4 2.04,
Ru2–C1 2.02, Ru2–N7 1.96, Ru2–N8 2.18, Ru2–N9 2.06, Ru2–N10 1.99,
Ru2–N11 2.05.
Chem. Asian J. 2013, 8, 1504 – 1513
1506
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
ꢁ
which also supports the formation of the Ru C bond in
complex 23+. The RuII/III process that is associated with the
[RuACTHUNTRGNENG(U bpy)2] unit takes place at +1.58 V, which is more posi-
tive than the corresponding process in monoruthenium com-
plex 12+. This result reflects the electron-withdrawing nature
of the added ruthenium ion in complex 23+. The irreversible
oxidation process at +1.15 V may be caused by ligand-based
oxidative decomposition. Such a peak is commonly observed
in cyclometalated ruthenium complexes.[9] Five cathodic
waves are observed at ꢁ0.83, ꢁ1.29, ꢁ1.51, ꢁ1.73, and
ꢁ1.88 V versus Ag/AgCl for complex 23+. The first two
waves are assigned to the reduction of the bridging ligand
and the other three waves are due to the reduction of the
bpy and Mebip ligands. In comparison, the previously asym-
metric bis-ruthenium complex [(bpy)2RuACTHNUGRTENNUG(dpdpzH)RuACHTUNGTRENNUNG(tpy)]-
Figure 2. CVs of a) 12+, b) 23+, and c) 42+ on a glassy carbon electrode in
0.1m Bu4NClO4/MeCN. Scan rate: 100 mVsꢁ1
ACHTUGNTRENUN(NG PF6)3 (tpy=2,2’,6’,2“-terpyridine) similarly showed three
anodic waves and five cathodic waves.[14] However, the cy-
clometalated RuII/III potential of complex 23+ is less positive,
as a result of the electron-donating nature of the Mebip
ligand.[19]
.
The anodic scan of asymmetric bis-ruthenium complex 23+
shows two chemically reversible oxidation waves at +0.61
and +1.58 V and an irreversible wave at +1.15 V versus Ag/
AgCl. The redox couple at +0.61 V is due to oxidation of
the cyclometalated ruthenium site (Ru2, Figure 1). This po-
tential is in accordance with the oxidation potential of most
reported cyclometalated monoruthenium complexes,[9]
RuPt complex 42+ shows some ill-defined anodic waves
(Figure 2c). However, the RuII/III process appears at +1.57 V
versus Ag/AgCl. Prior to the RuII/III process, the irreversible
waves may be due to oxidation of the platinum center or to
the platinum-acetylide component.[10,15] Five cathodic redox
couples can be observed within the solvent window of com-
plex 42+ (ꢁ0.66, ꢁ1.20, ꢁ1.46, ꢁ1.67, and ꢁ2.00 V).
The former two waves are attributable to the con-
secutive reductions of dpppz and the following two
Table 1. Electrochemical data.[a]
waves are assigned to the reductions of the bpy li-
gands. The origin of the fifth wave is unclear at this
stage. These electrochemical behaviors are quite
similar to the previously reported complex
Complex
12+, [(bpy)2Ru
E1/2 (anodic)
+1.41
E1/2 (cathodic)
(dpppzH)]
G
ꢁ0.96,
ꢁ1.43,
ꢁ1.64,
ꢁ1.98
ꢁ0.83,
ꢁ1.29,
ꢁ1.51,
ꢁ1.73,
ꢁ1.88
ꢁ0.66,
ꢁ1.20,
ꢁ1.46,
ꢁ1.67,
ꢁ2.00
ꢁ1.01,
ꢁ1.49,
ꢁ1.72
ꢁ0.97,
ꢁ1.40,
ꢁ1.73
ꢁ0.82,
ꢁ1.25,
ꢁ1.55,
ꢁ1.73,
ꢁ1.90
ꢁ0.65,
ꢁ1.23,
ꢁ1.51,
ꢁ1.79
2+ [15]
ꢀ
[(bpy)2Ru
N
23+, [(bpy)2Ru
42+, [(bpy)2Ru
A
G
+0.61,
+1.15,[b]
+1.58
DFT Calculations
To assist in the understanding of the electronic
structures of these complexes, DFT calculations
have been performed on complexes 23+ and 42+ by
A
(PF6)2
+1.35,[b]
+1.57
using
the
B3LYP/LANL2DZ/6-31G*/CPCM
method (for details, see the Experimental Section).
The single-crystal structure of complex 23+ was used
to generate the input file for the geometrical opti-
mizations. The optimized bond lengths that are as-
sociated with the Ru1 and Ru2 atoms are slightly
longer than those in the single-crystal structure (see
[c]
[(bpy)2Ru
(dpp)]
N
+1.38
+1.38
ACHTUNGTRENNUNG[(bpy)2RuACHTUNGTRENNUNG(dpdpzH2)]ACHTUNGTRENNUNG(PF6)2
A
(dpdpzH)Ru
N
+0.81,
+1.32,[b]
+1.57
ꢁ
the Supporting Information, Table S1). The Ru2
N8 bond (2.263 ꢁ) is the longest of all of the calcu-
ꢁ
ꢁ
ꢁ
lated Ru N bonds; the Ru2 N7, Ru2 N10, and
ꢁ
Ru2 C1 bonds are relatively shorter (2.033, 2.032,
A
(dpdpzH)PtCCPh]
+1.37,[b]
+1.58
and 2.036 ꢁ, respectively). This trend is in agree-
ment with the crystallographic data. The structure
of complex 42+ was constructed on the basis of the
DFT-optimized structure of complex 23+ by replac-
ꢁ ꢀ
[a] All measurements were performed in 0.1m nBu4NClO4/MeCN. Unless otherwise
stated, the potential is reported as E1/2 versus Ag/AgCl. Potentials versus Fc/Fc+ can
be estimated by substracting 0.45 V. [b] Irreversible, Epeak,anodic. [c] See Ref. [14].
ing the [RuACTHUNTGRNEUNG(Mebip)] component with [Pt C CPh].
Table S2 in the Supporting Information shows se-
Chem. Asian J. 2013, 8, 1504 – 1513
1507
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
lected bond lengths and angles in the DFT-optimized struc-
commonly present in cyclometalated complexes.[9,11] The
lower-lying HOMOꢁ3 and HOMOꢁ4 levels have major
contributions from the noncyclometalated ruthenium (Ru1)
component. The LUMO and LUMO+1 are associated with
the bridging ligand. The bpy ligands are responsible for the
higher-lying LUMO+2 and LUMO+3 levels. The Mebip
ligand makes a dominant contribution to the LUMO+4 and
LUMO+5 levels. This order of orbital alignment suggests
that the cyclometalated ruthenium atom in complex 23+ is
very likely to be oxidized prior to the noncyclometalated
atom. Moreover, the DFT-optimized structure of the one-
electron-oxidized form (24+) indicates a spin density that is
dominated by the cyclometalated ruthenium component
(see the Supporting Information, Figure S1). The order of
reduction of complex 23+ may take place from the bridging
ligand, followed by the bpy and Mebip ligands. These results
are consistent with the above assignments of the electro-
chemical behavior of complex 23+.
2+
ꢁ
ꢁ
ture of complex 4 . The Pt C1 and Pt C2 bond lengths are
calculated to be 2.002 and 1.966 ꢁ, respectively. The C1-Pt-
N8 angle is 158.298. These data agree well with those of
known cyclometalated platinum complexes.[10]
Figure 3 and Figure 4 show the isodensity plots of the
frontier orbitals for complexes 23+ and 42+, along with their
corresponding energy diagrams, respectively. The HOMO,
HOMOꢁ1, and HOMOꢁ2 of complex 23+ are mainly asso-
ciated with the cyclometalated ruthenium (Ru2) component.
However, there is also significant electron density on the cy-
clometalating phenyl ring in the HOMO, a feature that is
The HOMO of complex 42+ contains mixed contributions
from the phenylacetylide component and the platinum atom
(Figure 4). The HOMOꢁ1 and HOMOꢁ2 levels contain
mixed contributions from the triple bond, the platinum
atom, and the cyclometalating phenyl ring. The lower-lying
HOMOꢁ3 and HOMOꢁ4 levels are dominated by the
ruthenium component. The orbital compositions of the un-
occupied orbitals in complex 42+ share some similarities with
those in complex 23+. The LUMO and LUMO+1 levels are
associated with the bridging ligand. The LUMO+2 and
LUMO+3 levels are associated with the bpy ligands. The
pyridine rings of the bridging ligand are responsible for the
LUMO+4 orbital. Again, these results are consistent with
the electrochemical behavior of complex 42+, as shown in
Figure 2.
Figure 3. Isodensity plots of the frontier molecular orbitals of complex
23+, along with the energy diagram.
Absorption Studies and TDDFT Calculations
The electronic absorption spectra of complexes 12+, 23+, and
42+ are shown in Figure 5, along with those of previously re-
ported complexes [(bpy)2RuACTHNUTRGNEUNG
(dpdpzH2)]2+ and [(bpy)2Ru-
2+
AHCTUNGTRENNUNG
(dpdpzH)PtC CPh] for comparison.[14,15] The spectroscop-
ꢀ
ic data are delineated in Table 2. In addition, TDDFT calcu-
lations have been performed on the above DFT-optimized
structures of complexes 23+ and 42+ at the same level of
theory and the predicted low-energy excitations are sum-
marized in Table 3. Absorptions in the ultraviolet-light
ꢁ
region are due to intraACTHNUTRGENNlGU iACHTUTGNRNENUGgand p p* excitations. The metal-
to-ligand charge-transfer (MLCT) transitions in complex 12+
(lmax =427 and 481 nm) are slightly blue-shifted relative to
those in [(bpy)2RuACTHNUTRGNEUNG
(dpdpzH2)]2+ (lmax =446 and 490 nm).
Complex 23+ showed an intense absorption band at 577 nm
(e=0.41ꢂ105 mꢁ1 cmꢁ1). In addition, in the region 700–
1000 nm, some weak-but-distinct absorption are present.
TDDFT results suggest that the NIR absorption of complex
23+ is associated with HOMO!LUMO+1 and HOMO!
LUMO excitations (the S1 and S2 states, S stands for sin-
glet). The S11 state, with an oscillator strength (f) of 0.3817,
is likely responsible for the observed absorption band at
Figure 4. Isodensity plots of the frontier molecular orbitals of complex
42+, along with the energy diagram.
Chem. Asian J. 2013, 8, 1504 – 1513
1508
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
577 nm, although the predicted excitation is at higher
energy. This state is mainly associated with the HOMOꢁ2!
LUMO+1 excitation (MLCT transition from the Ru2 atom
to the bridging ligand) and has minor contributions from the
HOMOꢁ1!LUMO+4,
HOMO!LUMO+3,
and
HOMO!LUMO+5 excitations (MLCT transition from the
Ru2 atom to the Mebip or bpy ligands). Inconsistency be-
tween the TDDFT-predicted excitation energy and the ex-
perimental value is often observed in charge-transfer transi-
tions in metal complexes. The weaker absorption band of
complex 23+ at 456 nm is assigned to MLCT transitions from
the noncyclometalated ruthenium (Ru1) component.
RuPt complex 42+ has a very similar absorption spectrum
2+
ꢀ
to [(bpy)2Ru
N
ed low-energy absorption edge. The TDDFT results suggest
that the absorption band of complex 42+, with lmax =534 nm,
contains a major component from the HOMO!LUMO+1
excitation (the S2 state), which can be interpreted as a mix-
ture of platinum-based MLCT transitions and ligand-to-
ligand charge-transfer (LLCT) from the phenyl-acetylide
unit. The ruthenium-based MLCT transitions are very likely
within the region 400–500 nm. A similar situation has previ-
2+ [15]
ꢀ
ously been observed for [(bpy)2Ru
N
Figure 5. Electronic absorption spectra in MeCN and TDDFT results for
Emission Studies
a) 12+, b) 23+, and c) 42+. The right axes in (b) and (c) are associated with
the TDDFT excitations for complexes 23+ and 42+
.
The previously reported monoruthenium complex
[(bpy)2RuACTHNUTRGNEUNG
(dpdpzH2)]2+ exhibited an emission band at
709 nm and f=0.057% (Table 2 and Figure 6).[14] The excit-
ed-state lifetime (t) of this com-
plex was later determined to be
41 ns under ambient conditions
Table 2. Absorption and emission data.[a]
Complex
Absorption lmax [nm]
(e [ꢂ105 mꢁ1 cmꢁ1])
Emission[b] lmax [nm]/f [%]/t [ns]
in dilute MeCN. The newly pre-
pared ruthenium complex 12+,
12+, [(bpy)2Ru
G
N
285 (0.90),
347 (0.40),
427 (0.15),
481 (0.14)
299 (1.08),
365 (0.61),
456 (0.16),
577 (0.41),
834 (0.04)
282 (0.95),
363 (0.33),
426 (0.22),
468 (0.22),
534 (0.24)
695/2.9/302
which contains the dpppz
ligand, shows an emission band
at 695 nm. This slightly blue-
23+, [(bpy)2Ru
42+, [(bpy)2Ru
G
E
E
no emission detected
shifted emission maximum rela-
tive to complex [(bpy)2Ru-
AHCTUNGTRENNUNG
(dpdpzH2)]2+ is in accordance
with the difference in their ab-
sorption spectra. To our delight,
complex 12+ displays a much
752/0.41/170
higher
f value (2.9%) and
a longer lifetime (302 ns) under
the same experimental condi-
tions. These results suggest that
the free-standing phenyl rings
in the dpdpz ligand provide
[c]
G
R
G
N
430
470
U
675/5.1/135
[d]
G
E
N
299 (0.63),
360 (0.23),
446 (0.10),
490 (0.088)
286 (0.78),
380 (0.30),
436 (0.20),
477 (0.20),
545 (0.20)
709/0.057/41
a
non-emissive deactivation
[d]
[(bpy)2Ru
E
N
780/0.15/120
pathway, as discussed in the
design strategy of dpppzH (see
the Introduction).
No emission for bis-rutheni-
um complex 23+ was detected at
room temperature. Possible
[a] All spectra were recorded in MeCN at room temperature. [b] Excitation wavelength: 400 nm for all com-
pounds studied. Quantum yield was determined by comparison with [Ru
yield of 5.9% in N2-saturated MeCN. [c] See Ref. [6a]. [d] See Ref. [14].
ACHTUNGTRENGU(N bpy)3]ACHTUNTGREN(NUGN PF6)2, which had a quantum
emission from the [RuACHTUNGTRENNUNG(bpy)2]
Chem. Asian J. 2013, 8, 1504 – 1513
1509
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
Table 3. TDDFT results.[a]
170 ns. The emission maximum
of compound 42+ is slightly
blue-shifted relative to that of
Complex
Sn
E [eV]
l[nm]
f
Dominant transition(s)
Assignment[c]
(percentage contribution[b]
)
23+
1
2
6
10
11
1.75
1.81
2.25
2.53
2.54
706.6
686.8
550.8
490.5
488.8
0.0105
0.0491
0.0214
0.0453
0.3817
HOMO!LUMO+1 (77)
HOMO!LUMO (74)
HOMOꢁ2!LUMO (92)
HOMO!LUMO+3 (76)
MRu2LBLCT
MRu2LBLCT
MRu2LBLCT
MRu2LbpyCT
MRu2LBLCT
MRu2LMebipCT
MRu2LbpyCT
[(bpy)2RuACTHNUTRGENUG(N dpdpzH)PtC
ꢀ
CPh]2+, in accordance with
their absorption spectra, as
shown in Figure 5. It has been
reported that the excited-state
lifetime of bis-tridentate ruthe-
nium complexes can be pro-
longed by forming a two-metal
system, which stabilizes the
HOMOꢁ2!LUMO+1 (44)
HOMOꢁ1!LUMO+4 (12)
HOMO!LUMO+3 (11)
HOMO!LUMO+5 (10)
HOMOꢁ2!LUMO+4 (83)
HOMOꢁ1!LUMO+5 (98)
HOMO!LUMO (73)
M
Ru2LMebipCT
12
14
1
2
3
2.60
2.65
2.04
2.12
2.27
476.0
467.9
606.5
584.4
546.4
0.0538
0.0604
0.0444
0.2798
0.0478
MRu2LMebipCT
MRu2LMebipCT
MPtLBLCT/LLCT
42+
HOMO!LUMO+1 (72)
HOMOꢁ3!LUMO (46)
HOMOꢁ2!LUMO (24)
HOMOꢁ1!LUMO (18)
HOMOꢁ1!LUMO+1 (35)
HOMOꢁ1!LUMO (29)
HOMOꢁ2!LUMO+1 (17)
HOMOꢁ2!LUMO (14)
HOMOꢁ2!LUMO+1 (34)
HOMOꢁ3!LUMO+1 (23)
HOMOꢁ1!LUMO+1 (13)
HOMOꢁ3!LUMO+1 (50)
HOMOꢁ5!LUMO (52)
HOMOꢁ5!LUMO+1 (60)
MPtLBLCT/LLCT ligand p*-acceptor orbital and
MRuLBLCT
MPtLBLCT
MPtLBLCT
MPtLBLCT
MPtLBLCT
MPtLBLCT
MPtLBLCT
MPtLBLCT
MRuLBLCT
MPtLBLCT
MRuLBLCT
MRuLBLCT
MRuLBLCT
lowers the MLCT state below
the deactivating ligand-field
state.[24] However, previous
TDDFT results have shown
that the lowest MLCT transi-
tions are mainly associated with
the platinum-acetylide compo-
nent. Thus, we believe that the
NIR emission of complex 42+ is
7
8
2.53
2.58
289.7
480.1
0.0423
0.1258
9
11
15
2.63
2.71
2.87
471.7
457.4
432.1
0.1698
0.0373
0.0686
a
Pt-based MLCT/LLCT, as
a result of an energy-transfer
process from the excited Ru-
based MLCT state to the Pt-
based charge-transfer level.[25]
The enhanced f value and pro-
[a] Computed at the B3LYP/LANL2DZ/6-31G*/CPCM level of theory. [b] Actual contribution [%]=(configu-
ration coefficient)2 ꢂ2ꢂ100. [c] BL=bridging ligand. The Ru2 atom in complex 23+ is the cyclometalated one.
longed lifetime of complex 42+ with respect to [(bpy)2Ru-
(dpdpzH)PtC CPh] are presumably a combined result of
2+
ꢀ
G
the energy-gap law and the absence of a free-standing
phenyl ring in the bridging ligand in complex 42+.
Conclusions
In summary, a new NN-CNN-type bridging ligand 2,3-di(2-
pyridyl)-5-phenylpyrazine has been developed for the syn-
thesis of bimetallic complexes with interesting spectroscopic
and electrochemical properties. The asymmetric nature of
this ligand allows for the construction of heterobimetallic
complexes or homobimetallic complexes with different coor-
dination modes, as exemplified by RuPt complex 42+ and
bis-ruthenium complex 23+. As a result of the absence of
free-rotating phenyl groups, these new complexes display
enhanced emission quantum yields and prolonged excited-
state lifetimes with respect to the previously reported Ru
and RuPt complexes with 2,3-di(2-pyridyl)-5,6-phenylpyra-
zine. These properties make the RuPt complex potentially
useful for the photocatalytic reduction of water.[26] The
newly developed bridging ligand will also be useful for the
construction of other bimetallic complexes with mixed non-
cyclometalated and cyclometalated coordination modes.
Figure 6. Normalized emission spectra in MeCN at room temperature.
Excitation wavelength: 400 nm.
component could be quenched by the cyclometalated ruthe-
nium moiety, as a result of an energy-transfer process. Simi-
lar cyclometalated ruthenium-induced energy transfer and
emission quench have been reported previously.[14,23]
The previously reported heterobimetallic RuPt complex
2+
ꢀ
[(bpy)2Ru
N
0.15%.[15] The excited-state lifetime of [(bpy)2Ru-
(dpdpzH)PtC CPh] was later determined to be 120 ns.
The dpppz-bridged RuPt complex 42+ shows an emission
band at about 750 nm, with f=0.41% and a lifetime of
Chem. Asian J. 2013, 8, 1504 – 1513
1510
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
analysis calcd [%] for C61H46F18N13P3Ru2·3H2O: C 44.34, H 3.17, N 11.02;
found: C 44.28, H 3.03, N 11.32.
Experimental Section
Synthesis
General
(PF6)2 (32+
Synthesis of [(bpy)2RuACTHNUTRGENN(GU dpppz)PtCl]HCATUNGTRENNUNG )
An aqueous solution of K2PtCl4 (15 mL, 0.20 mmol, 82.0 mg) was added
to a solution of monoruthenium complex 12+ (0.10 mmol, 102 mg) in
MeCN (15 mL). The mixture was heated at reflux for 24 h under a nitro-
gen atmosphere. After cooling to RT, the organic solvent was evaporated
before adding an excess of aqueous KPF6. The resulting precipitate was
collected to afford complex 32+ as a deep red solid (112 mg, 90% yield).
This crude product was used in the next transformation without further
purification. MS (MALDI): m/z: 952.7 [Mꢁ2PF6]+.
Solution NMR spectra were recorded on a Bruker Avance 400 MHz
spectrometer. 1H NMR spectra are reported in ppm and are referenced
to residual protons in the deuterated solvent (d=7.26 ppm for CDCl3
and d=1.92 ppm for CD3CN). MS data were obtained on Bruker Dalton-
ics Inc. Apex II FT-ICR or Autoflex III MALDI-TOF mass spectrome-
ters. The matrix for the matrix-assisted laser desorption ionization time-
of-flight (MALDI-TOF) measurements is a-cyano-4-hydroxycinnamic
acid. Microanalysis was performed on Flash EA 1112 or Carlo Erba 1106
analyzers at the Institute of Chemistry, the Chinese Academy of Sciences.
Ferroceneboronic acid was purchased from Aladdin reagent of China.
ꢀ
Synthesis of [(bpy)2Ru
(dpppz)PtC CPh]
(PF6)2 (42+
)
The above-prepared complex 32+ (50.0 mg, 0.040 mmol), CuI (2.0 mg),
and phenylacetylene (0.30 mL, 0.30 mmol) were added to a mixture of ni-
trogen-saturated DMF (10 mL) and triethylamine (2 mL). The mixture
was stirred in the dark at RT for 22 h. The solvent was removed under
reduced pressure. The residue was purified by flash column chromatogra-
phy on silica gel (MeCN/H2O/aq. KNO3, 200:10:1), followed by anion ex-
change with an aqueous solution of KPF6, to give complex 42+ as a deep-
brown solid (36 mg, 70% yield). MS (MALDI): m/z: 1161.6 [MꢁPF6]+,
1017.7 [Mꢁ2PF6]+, 861.8 [Mꢁ2PF6ꢁbpy]+; elemental analysis calcd [%]
for C48H34F12N8P2PtRu·H2O: C 43.45, H 2.73, N 8.44; found: C 43.52,
H 2.77, N 8.83.
Synthesis of 2,3-Di(2-pyridyl)-5-phenylpyrazine (dpppzH)
A solution of 2,2’-pyridil (1.70 g, 8.0 mmol) and 1-phenylethylenediamine
(1.10 g, 8.0 mmol) in EtOH (40 mL) was heated at reflux for 20 h under
a nitrogen atmosphere. After cooling to RT, the mixture was opened to
air and stirred for a further 3 days. The resulting yellow precipitate was
collected and purified by flash column chromatography on silica gel
(CH2Cl2/EtOAc/NH4OH, 20:80:0.2) to give dpppzH as a yellow solid
(1.55 g, 63% yield). 1H NMR (400 MHz, CDCl3): d=7.23 (m, 2H), 7.50–
7.54 (m, 3H), 7.76–7.84 (m, 3H), 8.02 (d, J=7.8 Hz, 1H), 8.17 (d, J=
7.0 Hz, 2H), 8.38 (dd, J=15.0, 4.8 Hz, 2H), 9.11 ppm (s, 1H); 13C NMR
(100 MHz, CDCl3): d=122.79, 123.08, 124.13, 124.32, 127.19, 129.05,
130.04, 135.99, 136.44, 136.61, 139.52, 148.51, 148.77, 150.23, 150.34,
151.32, 157.06, 157.29 ppm; MS (EI): m/z: 309 [MꢁH]+, HRMS (EI): m/z
calcd for C20H13N4: 309.1139 [MꢁH]+; found: 309.1144.
Spectroscopic Measurements
Absorption spectra were obtained on a TU-1810DSPC spectrometer
(Beijing Purkinje General Instrument Co. Ltd.) at RT in MeCN in a con-
ventional quartz cell (path length: 1 cm). Emission spectra were recorded
on a F-380 spectrofluorimeter (Tianjin Gangdong Sic. & Tech Develop-
ment Co. Ltd.), with a red-light-sensitive R928F photomultiplier tube.
Samples for the emission measurements were placed in quartz cuvettes
(path length: 1 cm). Luminescence quantum yields were determined by
Synthesis of [(bpy)2Ru
(PF6)2 (12+
ACHTUNGTRENNUNG(dpppzH)]ACHTGNUTRENNUNG )
To a solution of dpppzH (62 mg, 0.20 mmol) in ethylene glycol (10 mL)
was added cis-[Ru(bpy)2Cl2]·2H2O (104 mg, 0.20 mmol) and the mixture
(PF6)2 in degassed MeCN as a standard (f=5.9%).[27]
using [RuACTHNUGTRNENUG(bpy)3]ACHTUNGTRENNUGN
The excited-state lifetime was determined on a Hamamatsu Quantaurus-
Tau under ambient conditions at RT.
ACHTUNGTRENNUNG
was heated under microwave irradiation for 30 min (375 W). After cool-
ing to RT, excess KPF6 (aq) was added. The resulting precipitate was col-
lected and purified by flash column chromatography on silica gel
(MeCN/H2O/aq. KNO3, 150:10:1) to give complex 12+ as a red solid
(140 mg, 64% yield). 1H NMR (400 MHz, CD3CN): d=7.22 (d, J=
8.3 Hz, 1H), 7.28 (t, J=6.2 Hz, 1H), 7.43–7.53 (m, 7H), 7.65–7.67 (m,
2H), 7.69 (d, J=5.5 Hz, 1H), 7.73 (d, J=5.4 Hz, 1H), 7.78–7.83 (m, 4H),
8.06–8.15 (m, 8H), 8.51 (d, J=7.2 Hz, 2H), 8.53 (d, J=8 Hz, 2H),
8.65 ppm (d, J=4.6 Hz, 1H); 13C NMR (100 MHz, CD3CN): d=125.77,
125.82, 125.99, 126.23, 127.10, 128.50, 128.79, 128.82, 129.06, 129.16,
129.22, 130.56, 132.92, 135.04, 137.99, 139.57, 139.59, 139.67, 139.73,
139.76, 142.45, 151.10, 151.23, 152.77, 152.87, 152.99, 153.40, 153.50,
153.66, 155.46, 156.84, 157.60, 157.86, 158.11, 158.27, 158.31 ppm; MS
(MALDI): m/z: 869.0 [MꢁPF6]+, 724.1 [Mꢁ2PF6]+; elemental analysis
calcd [%] for C40H30F12N8P2Ru2·H2O: C 46.57, H 3.11, N 10.86; found:
C 46.22, H 3.23, N 10.78.
X-ray Crystallography
X-ray diffraction data were collected on a Rigaku Saturn 724 diffractom-
eter with a rotating anode (MoKa radiation, 0.71073 ꢁ) at 173 K. The
structure was solved by using direct methods with SHELXS-97[28] and re-
fined with Olex2.[29] The structure shown in Figure 1 was generated by
using Olex2.
Electrochemical Measurements
All cyclic voltammetry (CV) measurements were recorded on
a CHI620D potentiostat with a one-compartment electrochemical cell
under a nitrogen atmosphere. All of the measurements were recorded in
0.1m Bu4NClO4 in indicated solvents at a scan rate of 100 mVsꢁ1. The
working electrode was a glassy carbon electrode with a diameter of
0.3 mm. The electrode was polished prior to use with 0.05 mm alumina
and thoroughly rinsed with water and acetone. A large-area platinum
wire coil was used as the counter electrode. All potentials are referenced
to a Ag/AgCl electrode in a saturated aqueous solution of NaCl without
regard for the liquid-junction potential.
(PF6)3 (23+
Synthesis of [(bpy)2RuACHTUNGTRENNUNG(dpppz)RuACHTUNGTREG(NNUN Mebip)]ACHNTUGTRENNUGN )
To a solution of [(Mebip)RuCl3][19] (27.0 mg, 0.050 mmol) in dry acetone
(15 mL) was added AgOTf (78.0 mg, 0.30 mmol) and the mixture was
heated at reflux for 2 h under a nitrogen atmosphere. After cooling to
RT, the generated AgCl precipitate was removed by filtering through
a pad of Celite. The filtrate was concentrated under reduced pressure.
The above-prepared monoruthenium complex 12+ (51.0 mg, 0.050 mmol),
DMF (10 mL), and tBuOH (10 mL) were added to the residue. The re-
sulting mixture was heated at reflux under a nitrogen atmosphere for
a further 24 h. The solvent was removed under reduced pressure. The res-
idue was dissolved in MeOH (1 mL), followed by the addition of excess
aqueous KPF6. The resulting precipitate was collected and purified by
flash column chromatography on silica gel (MeCN/H2O/aq. KNO3,
150:10:3), followed by anion exchange with KPF6, to give complex 23+ as
a deep purple solid (20.0 mg, 25% yield). MS (MALDI): m/z: 1307.2
[Mꢁ2PF6ꢁH]+, 1163.2 [Mꢁ3PF6]+, 1005.1 [Mꢁ3PF6ꢁbpy]+; elemental
Computational Methods
All calculations were implemented in the Gaussian 09 program.[30] Wave-
functions were expanded in the LANL2DZ basis set with effective core
potentials[31] and the electron-exchange correlation was described by
using the B3LYP hybrid functional.[32] Solvation effects in MeCN were in-
cluded by using the conductor-like polarizable continuum model
(CPCM) with united-atom Kohn–Sham (UAKS) radii.[33] All orbitals
were computed at an isovalue of 0.03 ebohrꢁ3
.
Chem. Asian J. 2013, 8, 1504 – 1513
1511
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
Campagna, G. Denti, V. Balzani, J. Am. Chem. Soc. 1999, 121,
10081.
Acknowledgements
[7] a) M. I. Bruce, Angew. Chem. 1977, 89, 75; Angew. Chem. Int. Ed.
Engl. 1977, 16, 73; b) M. E. van der Boom, D. Milstein, Chem. Rev.
2003, 103, 1759; c) Y. Chi, P.-T. Chou, Chem. Soc. Rev. 2010, 39, 638;
d) G. van Koten, D. Milstein, Organometallic Pincer Chemistry,
Topics in Organometallic Chemistry, Vol. 40, Springer, Heidelberg,
2013.
This work was supported by the National Natural Science Foundation of
China (91227104, 21002104, 212210017, and 21271176), the National
Basic Research 973 Program of China (2011CB932301), the Scientific
Research Foundation for Returned Overseas Chinese Scholars, the State
Education Ministry of China, and the Institute of Chemistry at the Chi-
nese Academy of Sciences (100 Talent Program, CMS-PY-201230).
[8] a) Y. You, S. Y. Park, Dalton Trans. 2009, 1267; b) Z.-q. Chen, Z.-q.
Bian, C.-H. Huang, Adv. Mater. 2010, 22, 1534; c) M. Polson, M.
Ravaglia, S. Fracasso, M. Garavelli, F. Scandola, Inorg. Chem. 2005,
44, 1282; d) A. J. Wilkinson, A. E. Goeta, C. Foster, J. A. G. Wil-
liams, Inorg. Chem. 2004, 43, 6513; e) Y.-C. Zhu, L. Zhou, H.-Y. Li,
Q.-L. Xu, M.-Y. Teng, Y.-X. Zheng, J.-L. Zuo, H.-J. Zhang, X.-Z.
You, Adv. Mater. 2011, 23, 4041.
[1] a) J.-P. Sauvage, J.-P. Collin, J.-C. Chambron, S. Gulllerez, C. Cou-
dret, Chem. Rev. 1994, 94, 993; b) U. S. Schubert, C. Eschbaumer,
Angew. Chem. 2002, 114, 3016; Angew. Chem. Int. Ed. 2002, 41,
2892; c) J.-P. Collin, P. Laine, J.-P. Launay, J.-P. Sauvage, A. Sour, J.
Chem. Soc. Chem. Commun. 1993, 434; d) J. Bolger, A. Gourdon, E.
Ishow, J.-P. Launay, J. Chem. Soc. Chem. Commun. 1995, 1799; e) P.
Bonhote, A. Lecas, E. Amouyal, Chem. Commun. 1998, 885; f) A.
Gourdon, J.-P. Launay, Inorg. Chem. 1998, 37, 5336; g) E. Ishow, A.
Gourdon, J.-P. Launay, C. Chiorboli, F. Scandola, Inorg. Chem. 1999,
38, 1504; h) A. L. Sauers, D. M. Ho, S. Bernhard, J. Org. Chem.
2004, 69, 8910; i) C. N. Carlson, C. J. Kuehl, R. E. Da Re, J. M.
Veauthier, E. J. Schelter, A. E. Milligan, B. L. Scott, E. D. Bauer,
J. D. Thompson, D. E. Morris, K. D. John, J. Am. Chem. Soc. 2006,
128, 7230; j) D. M. D’Alessandro, P. H. Dinolfo, M. S. Davis, J. T.
Hupp, F. R. Keene, Inorg. Chem. 2006, 45, 3261; k) S. Singh, N. R.
de Tacconi, N. R. G. Diaz, R. O. Lezna, J. M. Zuniga, K. Abayan,
F. M. MacDonnell, Inorg. Chem. 2011, 50, 9318.
[2] a) B. Ulgut, H. D. AbruÇa, Chem. Rev. 2008, 108, 2721; b) P. J. Low,
Dalton Trans. 2005, 2821; c) M. Akita, T. Koike, Dalton Trans. 2008,
3523; d) N. Tuccitto, V. Ferri, M. Cavazzini, S. Quici, G. Zhavnerko,
A. Licciardello, M. A. Rampi, Nat. Mater. 2009, 8, 41; e) J.-W. Ying,
I. P.-C. Liu, B. Xi, Y. Song, C. Campana, J.-L. Zuo, T. Ren, Angew.
Chem. 2010, 122, 966; Angew. Chem. Int. Ed. 2010, 49, 954.
[3] a) R. M. Leasure, W. Ou, J. A. Moss, R. W. Linton, T. J. Meyer,
Chem. Mater. 1996, 8, 264; b) S. Bernhard, J. I. Goldsmith, K.
Takada, H. D. AbruÇa, Inorg. Chem. 2003, 42, 4389; c) C.-J. Yao, Y.-
W. Zhong, H.-J. Nie, H. D. AbruÇa, J. Yao, J. Am. Chem. Soc. 2011,
133, 20720; d) C.-J. Yao, J. Yao, Y.-W. Zhong, Inorg. Chem. 2012, 51,
6259.
[9] a) C. Coudret, S. Fraysse, J.-P. Launay, Chem. Commun. 1998, 663;
b) S. H. Wadman, J. M. Kroom, K. Bakker, M. Lutz, A. L. Spek,
G. P. M. van Klink, G. van Koten, Chem. Commun. 2007, 1907; c) J.-
P. Djukic, J.-B. Sortais, L. Barloy, M. Pfeffer, Eur. J. Inorg. Chem.
2009, 817; d) B. D. Koivisto, K. C. D. Robson, C. P. Berlinguette,
Inorg. Chem. 2009, 48, 9644; e) M. Jꢃger, A. Smeigh, F. Lombeck,
H. Gçrls, J.-P. Collin, J.-P. Sauvage, L. Hammarstrçm, O. Johanns-
son, Inorg. Chem. 2010, 49, 374; f) S. H. Wadman, J. M. Kroon, K.
Bakker, R. W. A. Havenith, G. P. M. van Klink, G. van Koten, Orga-
nometallics 2010, 29, 1569; g) W.-W. Yang, L. Wang, Y.-W. Zhong, J.
Yao, Organometallics 2011, 30, 2236; h) C.-J. Yao, R.-H. Zheng, Q.
Shi, Y.-W. Zhong, J. Yao, Chem. Commun. 2012, 48, 5680.
[10] a) W. Lu, B.-X. Mi, M. C. W. Chan, Z. Hui, C.-M. Che, N. Zhu, S.-T.
Lee, J. Am. Chem. Soc. 2004, 126, 4958; b) P. Shao, Y. Li, J. Yi,
T. M. Pritchett, W. Sun, Inorg. Chem. 2010, 49, 4507; c) A. Hofmann,
L. Dahlenburg, R. van Eldik, Inorg. Chem. 2003, 42, 6528; d) T.-C.
Cheung, K.-K. Cheung, S.-M. Peng, C.-M. Che, J. Chem. Soc. Dalton
Trans. 1996, 1645; e) J. Ni, X. Zhang, Y.-H. Wu, L.-Y. Zhang, Z.-N.
Chen, Chem. Eur. J. 2011, 17, 1171.
[11] a) C.-J. Yao, Y.-W. Zhong, J. Yao, J. Am. Chem. Soc. 2011, 133,
15697; b) L.-Z. Sui, W.-W. Yang, C.-J. Yao, H.-Y. Xie, Y.-W. Zhong,
Inorg. Chem. 2012, 51, 1590.
[12] C.-J. Yao, L.-Z. Sui, H.-Y. Xie, W.-J. Xiao, Y.-W. Zhong, J. Yao,
Inorg. Chem. 2010, 49, 8347.
[13] a) M. Beley, J.-P. Collin, R. Louis, B. Metz, J.-P. Sauvage, J. Am.
Chem. Soc. 1991, 113, 8521; b) J.-P. Sutter, D. M. Grove, M. Beley,
J.-P. Collin, N. Veldman, A. L. Spek, J.-P. Sauvage, G. van Koten,
Angew. Chem. 1994, 106, 1359; Angew. Chem. Int. Ed. Engl. 1994,
33, 1282; c) C. Patoux, J.-P. Launay, M. Beley, S. Chodorowski-
Kimmers, J.-P. Collin, S. James, J.-P. Sauvage, J. Am. Chem. Soc.
1998, 120, 3717; d) P. Steenwinkel, D. M. Grove, N. Veldman, A. L.
Spek, G. van Koten, Organometallics 1998, 17, 5647; e) S. Fraysse, C.
Coudret, J.-P. Launay, J. Am. Chem. Soc. 2003, 125, 5880; f) M. Ga-
gliardo, C. H. M. Amijs, M. Lutz, A. L. Spek, R. W. A. Havenith, F.
Hartl, G. P. M. van Klink, G. van Koten, Inorg. Chem. 2007, 46,
11133.
[4] a) W.-Y. Wong, C.-L. Ho, Acc. Chem. Res. 2010, 43, 1246; b) S.
Diring, R. Ziessel, F. Barigelletti, A. Barbieri, B. Ventura, Chem.
Eur. J. 2010, 16, 9226; c) S. Goeb, A. De Nicola, R. Ziessel, C. Saba-
tini, A. Barbieri, F. Barigelletti, Inorg. Chem. 2006, 45, 1173;
d) A. C. Benniston, A. Harriman, P. Li, C. A. Sams, J. Am. Chem.
Soc. 2005, 127, 2553.
[5] a) C. R. Arana, H. D. AbruÇa, Inorg. Chem. 1993, 32, 194; b) L. M.
Vogler, B. Scott, K. J. Brewer, Inorg. Chem. 1993, 32, 898; c) R. Ru-
minski, J. Kiplinger, T. Cockroft, C. Chase, Inorg. Chem. 1989, 28,
370; d) L. M. Vogler, K. J. Brewer, Inorg. Chem. 1996, 35, 818;
e) C. M. Hartshorn, N. Daire, V. Tondreau, B. Loeb, T. J. Meyer,
P. S. White, Inorg. Chem. 1999, 38, 3200; f) D. M. Dattelbaum, C. M.
Hartshom, T. J. Meyer, J. Am. Chem. Soc. 2002, 124, 4938; g) N.
Chanda, B. Sarkar, S. Kar, J. Fiedler, W. Kaim, G. K. Lahiri, Inorg.
Chem. 2004, 43, 5128; h) S. Flores-Torres, G. R. Hutchison, L. J.
Stoltzberg, H. D. AbruÇa, J. Am. Chem. Soc. 2006, 128, 1513.
[6] a) C. H. Braunstein, A. D. Baker, T. C. Strekas, H. D. Gafney, Inorg.
Chem. 1984, 23, 857; b) R. Sahai, L. Morgan, D. P. Rillema, Inorg.
Chem. 1988, 27, 3495; c) G. Denti, S. Campagna, L. Sabatino, S. Ser-
roni, M. Ciano, V. Balzani, Inorg. Chem. 1990, 29, 4750; d) S. Serro-
ni, G. Denti, S. Campagna, A. Juris, M. Ciano, V. Balzani, Angew.
Chem. 1992, 104, 1540; Angew. Chem. Int. Ed. Engl. 1992, 31, 1493;
e) M. M. Richter, K. J. Brewer, B. J. Yoblinski, M. Stathis, T. F.
Guarr, Inorg. Chem. 1992, 31, 1594; f) M. M. Richter, K. J. Brewer,
Inorg. Chem. 1993, 32, 2827; g) S. Serroni, A. Juris, S. Campagna, M.
Venturi, G. Denti, V. Balzani, J. Am. Chem. Soc. 1994, 116, 9086;
h) V. Balzani, S. Campagna, G. Denti, A. Juris, S. Serroni, M. Ven-
turi, Acc. Chem. Res. 1998, 31, 26; i) M. Marcaccio, F. Paolucci, C.
Paradisi, S. Roffia, C. Fontanesi, L. J. Yellowlees, S. Serroni, S,
[14] a) Y.-W. Zhong, S.-H. Wu, S. E. Burkhardt, C.-J. Yao, H. D. AbruÇa,
Inorg. Chem. 2011, 50, 517; b) S.-H. Wu, S. E. Burkhardt, Y.-W.
Zhong, H. D. AbruÇa, Inorg. Chem. 2012, 51, 13312.
[15] S.-H. Wu, S. E. Burkhardt, J. Yao, Y.-W. Zhong, H. D. AbruÇa,
Inorg. Chem. 2011, 50, 3959.
[16] S.-H. Wu, H. D. AbruÇa, Y.-W. Zhong, Organometallics 2012, 31,
1161.
[17] a) J. Fabian, H. Makazumi, M. Matsuoka, Chem. Rev. 1992, 92,
1197; b) G. Qian, Z. Y. Wang, Chem. Asian J. 2010, 5, 1006.
[18] a) S. Shatzmiller, S. Bercovici, Liebigs Ann. Chem. 1992, 1005;
b) L. M. Hryhorczuk, J. C. Bailar, Jr., Inorg. Chem. 1985, 24, 3367;
c) L. Maier, P. J. Diel, Phosphorous Sulfur Silicon Relat. Elem. 1995,
107, 245.
[19] W.-W. Yang, Y.-W. Zhong, S. Yoshikawa, J.-Y. Shao, S. Masaoka, K.
Sakai, J. Yao, M.-a. Haga, Inorg. Chem. 2012, 51, 890.
[20] a) S. L. James, M. Younus, P. R. Raithby, J. Lewis, J. Organomet.
Chem. 1997, 543, 233; b) M. Hissler, J. E. McGarrah, W. B. Connick,
D. K. Geiger, S. D. Cummings, R. Eisenberg, Coord. Chem. Rev.
Chem. Asian J. 2013, 8, 1504 – 1513
1512
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Yu-Wu Zhong et al.
2000, 208, 115; c) M. Hissler, W. B. Connick, D. K. Geiger, J. E.
McGarrah, D. Lipa, R. J. Lachicotte, R. Eisenberg, Inorg. Chem.
2000, 39, 447; d) V. W.-W. Yam, K. H.-Y. Chan, K. M.-C. Wong,
B. W.-K. Chu, Angew. Chem. 2006, 118, 6315; Angew. Chem. Int. Ed.
2006, 45, 6169; e) J. B. Seneclauze, P. Retailleau, R. Ziessel, New J.
Chem. 2007, 31, 1412.
[28] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112.
[29] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H.
Puschmann, J. Appl. Crystallogr. 2009, 42, 339.
[30] Gaussian 09 (RevisionA.2), M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgom-
ery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,
N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Na-
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wallingford
CT, 2009.
[21] Crystallographic data for [2]ACTHNUTGREN(GNU PF6)3: C61H46F18N13P3Ru2; Mw =
1598.16; monoclinic; space group P21/c; a=11.673(3), b=17.288(5),
c=38.114(11) ꢁ; a=90.00, b=98.880(3), g=90.008; U=7599(4) ꢁ3;
T=173 K; Z=4; 16004 reflections measured; MoKa radiation (l=
0.71073 ꢁ); final R indices R1 =0.0981, wR2 =0.2634; R indices (all
data) R1 =0.1167, wR2 =0.2746. CCDC 936001 contains the supple-
mentary crystallographic data for [2]ACTHNUGTRNEG(UN PF6)3. This data can be ob-
tained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data request/cif.
[22] a) P. Reveco, R. H. Schmehl, W. R. Cherry, F. R. Fronczek, J. Selbin,
Inorg. Chem. 1985, 24, 4078; b) S. H. Wadman, M. Lutz, D. M.
Tooke, A. L. Spek, F. Hartl, R. W. A. Havenith, G. P. M. van Klink,
G. van Koten, Inorg. Chem. 2009, 48, 1887; c) S. K. Padhi, K.
Tanaka, Inorg. Chem. 2011, 50, 10718; d) Y.-M. Zhang, J.-Y. Shao,
C.-J. Yao, Y.-W. Zhong, Dalton Trans. 2012, 41, 9280.
[23] S. Ott, M. Borgstrçm, L. Hammarstrçm, O. Johansson, Dalton
Trans. 2006, 1434.
[24] S. Zhao, S. M. Arachchige, C. Slebodnick, K. J. Brewer, Inorg.
Chem. 2008, 47, 6144.
[31] a) T. H. Dunning, P. J. Hay in Modern Theoretical Chemistry, Vol. 3
(Ed.: H. F. Schaefer), Plenum, New York, 1976, p. 1; b) P. J. Hay,
W. R. Wadt, J. Chem. Phys. 1985, 82, 270; c) W. R. Wadt, P. J. Hay, J.
Chem. Phys. 1985, 82, 284; d) P. J. Hay, W. R. Wadt, J. Chem. Phys.
1985, 82, 299.
[25] a) A. Juris, V. Balzani, S. Campagna, G. Denti, S. Serroni, G. Frei,
H. U. Gꢄdel, Inorg. Chem. 1994, 33, 1491; b) F. Puntoriero, S. Serro-
ni, A. Licciardello, M. Venturi, A. Juris, V. Ricevuto, S. Campagna,
J. Chem. Soc. Dalton Trans. 2001, 1035; c) T. L. Easun, W. Z. Alsin-
di, M. Towrie, K. L. Ronayne, X.-Z. Sun, M. D. Ward, M. W.
George, Inorg. Chem. 2008, 47, 5071; d) Y. Fan, L.-Y. Zhang, F.-R.
Dai, L.-X. Shi, Z.-N. Chen, Inorg. Chem. 2008, 47, 2811.
[26] a) M. Kobayashi, S. Masaoka, K. Sakai, Angew. Chem. 2012, 124,
7549; Angew. Chem. Int. Ed. 2012, 51, 7431; b) M. Schulz, M. Kar-
nahl, M. Schwalbe, J. G. Vos, Coord. Chem. Rev. 2012, 256, 1682.
[27] K. Nakamaru, Bull. Chem. Soc. Jpn. 1982, 55, 1639.
[32] a) A. D. Becke, J. Chem. Phys. 1993, 98, 5648; b) C. Lee, W. Yang,
R. G. Parr, Phys. Rev. B 1988, 37, 785.
[33] a) A. Klamt, G. Schꢄꢄrmann, J. Chem. Soc. Perkin Trans. 2 1993,
799; b) J. Andzelm, C. Kçlmel, A. Klamt, J. Chem. Phys. 1995, 103,
9312; c) V. Barone, M. Cossi, J. Phys. Chem. A 1998, 102, 1995;
d) M. Cossi, N. Rega, G. Scalmani, V. Barone, J. Comput. Chem.
2003, 24, 669; e) Y. Takano, K. N. Houk, J. Chem. Theory Comput.
2005, 1, 70.
Received: March 12, 2013
Published online: May 2, 2013
Chem. Asian J. 2013, 8, 1504 – 1513
1513
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim