Core cross-linked micelle-based nanoreactors for efficient photocatalysis

Article abstract of DOI:10.1002/asia.201300668

Stable nanoscale cross-linked polymer micelles containing Ru complexes (Ru-CMs) were prepared from monomethoxy[poly(ethylene glycol)]-block-poly(L- lysine) (MPEG-PLys) and [(bpy)₂Ru(fmbpy)](PF₆)₂ (bpy=bipyridine, fmbpy=5-formy-5′-methyl-2,2′-bipyridine). To stabilize the micelles, bifunctional glutaraldehyde was used as a cross-linker to react with the free amino groups of the PLys block. After that, the Ru-CMs showed very good stability in common solvents. The Ru-CMs showed photocatalytic activity and selectivity in the oxidation of sulfides that were as high as those of the well-known [Ru(bpy)₃(PF₆)₂] complex, because the micelles were swollen in the methanol-sulfide mixture. Moreover, because of the nanoscale size of the particles and their high stability, the Ru-CM photocatalysts can be readily recovered by ultrafiltration and reused without loss of photocatalytic activity. This work highlights the potential of using cross-linked micelles as a platform for developing highly efficient heterogeneous photocatalysts for a number of important organic transformations. Stuck in the micelle with you: Stable nanoscale cross-linked polymer micelles loaded with Ru complexes (i.e., Ru-CMs) are prepared and used as highly efficient visible-light photocatalysts for the oxidation of sulfides. MPEG-PLys=monomethoxy[poly(ethylene glycol)]-block-poly(L-lysine), bpy=bipyridine, fmbpy =5-formy-5′-methyl-2,2′-bipyridine. Copyright

Full text of DOI:10.1002/asia.201300668

FULL PAPER
DOI: 10.1002/asia.201300668
Core Cross-Linked Micelle-Based Nanoreactors for Efficient Photocatalysis
[
a]
[a]
[b]
[b]
Min Zheng, Zaicheng Sun,* Zhigang Xie,* and Xiabin Jing
Abstract: Stable nanoscale cross-linked
polymer micelles containing Ru com-
plexes (Ru-CMs) were prepared from
stability in common solvents. The Ru-
CMs showed photocatalytic activity
and selectivity in the oxidation of sul-
fides that were as high as those of the
well-known [Ru AHCTUNGERTNNUNG( bpy) ACHTUNGTRNENU(G PF ) ] complex,
3 6 2
because the micelles were swollen in
the methanol–sulfide mixture. More-
over, because of the nanoscale size of
the particles and their high stability,
the Ru-CM photocatalysts can be read-
ily recovered by ultrafiltration and
reused without loss of photocatalytic
activity. This work highlights the poten-
tial of using cross-linked micelles as
a platform for developing highly effi-
cient heterogeneous photocatalysts for
a number of important organic trans-
formations.
monomethoxy
block-poly(l-lysine) (MPEG-PLys) and
(bpy) Ru(fmbpy)](PF ) (bpy=bipyri-
ACHTUNGTRENNUNG[ poly(ethylene glycol)]-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
6 2
dine, fmbpy=5-formy-5’-methyl-2,2’-bi-
pyridine). To stabilize the micelles, bi-
functional glutaraldehyde was used as
a cross-linker to react with the free
amino groups of the PLys block. After
that, the Ru-CMs showed very good
Keywords: micelles · nanoreactors ·
oxidation · photocatalysts · ruthe-
nium
Introduction
by trace amounts of heavy metals but also reduces process-
[3]
ing and waste disposal costs in large-scale production. Or-
ganometallic catalysts loaded on hard frameworks such as
Sunlight can be considered as a sustainable and renewable
energy source for thermal and electrical energy (photovolta-
ic cells). Besides that, photocatalytic organic reactions
driven by visible light are gaining interest from organic
chemists, because of their mild conditions for substrate acti-
vation and the potential to mediate thermodynamically
[4]
mesoporous silica and zeolites are extensively employed.
However, the low dispersibility of inorganic catalysts in an
organic reaction mixture often causes a low conversion rate
of the reaction owing to the heterogeneous interface be-
tween the reactant and the catalyst.
[
1]
uphill reactions by harvesting energy from sunlight. Sever-
Block copolymers (BCPs) can self-assemble into various
kinds of nanoscale aggregates such as spheres, cylinders, and
vesicles by varying the BCP composition, solvent, concentra-
2
3
+
al metal complexes, including Ru
dine) and [Ir
bpy=4,4’-di-tert-butyl-2,2’-bipyridine), have been used as
A
H
U
G
R
N
N
(bpy)
(bpy=2,2’-bipyri-
ACHTUNGTRENNUNG( ppy) ACHTUNGTRENNUNG( dtb-bpy)] (ppy=2-phenylpyridine, dtb-
2
+
[5]
tion, and temperature. Of the aggregates, BCP micelles
[
2]
[6]
photocatalysts for a number of organic transforms. These
photocatalysts display high catalytic activity and selectivity
for many organic reactions as a result of the homogeneous
reaction environment. However, the catalysts are prepared
from precious metals, and as such, the recovery and reuse of
the catalysts are essential and critical for their wide use in
chemical industries. Great effort has been made to develop
reusable heterogeneous photocatalytic systems based on Ru
complexes. The reuse of such heterogeneous photocatalysts
not only eliminates contamination of the organic products
have great potential for use in targeted drug delivery,
[7]
nanoreactors for inorganic materials, mesoporous nano-
[8]
[9]
structured templates, and hybrid composite materials.
However, the dynamic instability of BCP micelles can
hinder their use in such applications. Although the critical
micelle concentration (CMC) of polymer micelles is much
lower than that of small-molecule surfactants, BCP micelles
are still susceptible to disassembly under high dilution con-
[5b]
ditions. A change in the solvent, an increase in tempera-
ture, mechanical stress, and shear force can also lead to
rapid disassembly of BCP micelles. These considerations
have motivated important breakthroughs in the stabilization
of BCP micelles through cross-linking of either their corona
[
a] Dr. M. Zheng, Prof. Dr. Z. Sun
State Key Laboratory of Luminescence and Applications
Changchun Institute of Optics, Fine Mechanics and Physics, CAS
[10]
or cores.
By interchain bonding, cross-linked micelles
3
888 East Nanuhu Road, Changchun, Jilin 130033 (P. R. China)
(CMs) are stable, self-assembled nanostructures that can be
used under harsh conditions. A wide variety of micelle
cross-linking methodologies have been developed, including
E-mail: sunzc@ciomp.ac.cn
[
b] Prof. Dr. Z. Xie, Prof. Dr. X. Jing
State Key Laboratory of Polymer Physics and Chemistry
Changchun Institute of Applied Chemistry, CAS
5
[11]
radical-induced bond formation, photoinduced cycloaddi-
[
12]
[13]
tions,
siloxane condensation,
the use of bifunctional
625 Renmin Street, Changchun Jilin 130022 (P. R. China)
[14]
[10]
cross-linking agents, and many others. CMs can serve as
ideal nanoreactors to incorporate molecular catalytic mod-
ules into highly stable, recyclable, and reusable heterogene-
E-mail: xiez@ciac.jl.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300668.
Chem. Asian J. 2013, 8, 2807 – 2812
2807
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Zaicheng Sun, Zhigang Xie et al.
ous catalysts by taking advantage of their nanoscale size and
their good dispersity in the reaction solution owing to their
monomethoxy
A
H
U
G
R
N
U
G
glycol)]-block-poly ACHTUNGTERNNUN(G l-lysine)
(MPEG-PLys) after deprotection from MPEG-Plys(Z) (Z=
carbobenzyloxy). These amino groups can react with alde-
hyde groups to form C=N bonds through a Schiff base reac-
tion. Given that the number of amino groups (1.00 equiv) is
higher than the number of Ru complexes (0.016 equiv) in
the reaction solution, the Ru complexes are covalently
linked to only a portion of the amino groups on the PLys
block. Then, glutaraldehyde is introduced into the reaction.
Bifunctional glutaraldehyde (0.99 equiv) provides the excess
amount of aldehyde groups for the Schiff base reaction and
causes cross-linking in the PLys block. Because the cross-
linking reaction lowers the hydrophilicity of the PLys block,
the block copolymer self-assembles into nanoscale micelles
with the cross-linked PLys as the core and MPEG as the
corona. The Ru content of the micelles prepared though this
route was determined by inductively coupled plasma mass
spectrometry (ICP-MS) to be 0.67 wt% in the final product.
Covalent attachment of the Ru complex on the PLys block
results in a high local catalyst concentration inside the hy-
drophobic core of the polymeric micelles upon aggregation
in a hydrophilic or aqueous environment, and this is benefi-
cial to increase the reaction rates of catalytic reactions.
Moreover, the cross-linked core layer provides a shield
against metal leaching and catalyst poisoning, which could
facilitate catalyst recovery and recycling. Furthermore,
cross-linking of the core improves the stability of the cata-
lyst, but the permeability of the micelles is retained, which
allows the diffusion of small molecules in and out of the
nanoreactors. As there are many amino groups in intermedi-
ate 1, both blocks are hydrophilic. Intermediate 1 cannot
form micelles in the water/THF mixture, which was deter-
mined by dynamic light scattering (DLS; Figure S1a, Sup-
porting Information). To compare the stabilities of the CMs
with BCP micelles, Ru-NCMs were designed and synthe-
sized starting from MPEG-PLys(Z). Because the amine
groups on the side chain of lysine were protected by benzy-
[15]
outer corona.
In addition, CMs could provide external
shielding against micelle dissociation and catalyst leaching,
which can benefit catalyst recovery and recycling.
In this work, we tried to incorporate Ru complexes into
nanoscale BCP micelles simply through a Schiff base reac-
tion. Further, the cores of the micelles were cross-linked by
bifunctional glutaraldehyde to form cross-linked micelles
loaded with Ru complexes (i.e., Ru-CMs) The resulting Ru-
CMs are highly stable and active in catalyzing the visible-
light-driven oxidation of sulfides. Owing to the existence of
the outer corona of the CMs, the Ru-CMs can disperse into
and swell in the reaction solution very well, so that the sub-
strate can diffuse into the core and the reaction product can
escape from the catalytic center. Therefore, the Ru-CMs ex-
hibit a conversion rate and selectivity that are comparable
to those of homogeneous Ru photocatalysts. Moreover, be-
cause of the nanoscale size of the particles and their high
stability, the Ru-CMs photocatalysts can be readily recov-
ered by ultrafiltration and reused without a decrease in cata-
lytic efficiency.
Results and Discussion
The synthetic routes to Ru-CMs and non-cross-linked
micelles loaded with Ru complexes (Ru-NCMs) are shown
in the Scheme 1. There are free amino groups in
loxycarbonyl groups, the [(bpy) Ru
A
H
U
G
R
N
U
G
ACHTUNGTNERNUNG( PF ) (fmbpy=
6 2
2
5
linked at the end of the main chain. Intermediate 2 can self-
assemble into micelles (i.e., Ru-NCMs) in H O/THF be-
2
cause of the weak hydrophilicity of the PLys(Z) block.
Figure 1a shows the FTIR spectra of the pure block copo-
lymer MPEG-PLys, [(bpy) Ru ACTHUNGTERNNGNU( fmbpy)] ACHTUNGERTNNUNG( PF ) , and the Ru-
6 2
2
CMs. For MPEG-PLys, the absorption peaks at 3270 and
À1
1
625 cm are assigned to stretching and bending vibrations
of the NÀH group of the amine, whereas the band at
À1
1
350 cm is attributed to the stretching vibration of CÀNH.
À1
For [(bpy) Ru
A
H
U
T
E
N
N
(fmbpy)]
A
H
U
G
R
N
N
(PF ) , the peak at 1710 cm corre-
2
6 2
sponds to the stretching vibration of the C=O moiety of the
aldehyde group. After the Schiff base reaction, for the Ru-
CMs, the characteristic bands for the vibrations of the NÀH
group disappeared, and at the same time, another new band
À1
appeared at 1650 cm , which indicates that all of the amine
groups have reacted with the aldehyde groups and that C=N
bonds are formed as the product of the Schiff base reaction.
Scheme 1. Synthesis routes to the Ru-CMs and Ru-NCMs.
The emission spectra of [(bpy) Ru AHCTUNGTERNNUNG( fmbpy)] ACHTNUGTERNNUG(N PF ) and the
2 6 2
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Zaicheng Sun, Zhigang Xie et al.
polymer was completely dissolved in THF. Thus, cross-link-
ing plays a critical role in the formation of the micelles in
addition to maintaining their stability. The particle size of
the Ru-CMs in MeOH, H O, and THF solution determined
2
by DLS (Figure 2b) is 221, 246, and 265 nm, respectively,
and these values are more than two times larger than those
determined by SEM. Because SEM characterizes the sam-
ples in the solid state, shrinkage while the micelles are dried
results in a small particle size, whereas the diameter of the
micelles determined by DLS represents the hydrodynamic
diameter. The much larger apparent size of the particles in
water, methanol, and THF implies that not only the corona
MPEG block but also the core cross-linked PLys block of
the Ru-CMs are in an extended state in the solution. Thus,
the Ru-CMs can be swollen by the solvent. In that case, the
Ru species have enough opportunity to come in contact
with the reactant molecules in solution, and the reaction
product can escape from the catalytic center with ease.
Sulfoxides are important intermediates for the synthesis
of valuable compounds such as pharmaceuticals and other
Figure 1. A) FTIR spectra of MPEG-PLys (i), [(bpy)
ii), and the Ru-CMs (iii); B) emission spectra of [(bpy)
(PF in MeOH (i) the Ru-CMs in MeOH (ii), and the Ru-NCMs in
O (iii) with excitation at 450 nm.
2
Ru
A
H
U
G
R
N
N
6 2
ACHTUNGRTNNGE(U PF )
(
2
ACHTUNGTRENNUNG
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
6 2
)
H
2
Ru-CMs were recorded with excitation at 450 nm (Fig-
ure 1b). The characteristic band of [(bpy) Ru(fmbpy)](PF )
6 2
A
H
U
G
R
N
N
ACHTUNGTRENNUNG
2
3
at 613 nm could be attributed to MLCT (metal-to-ligand
charge transfer) transitions to the GS (ground state). The
bands for the Ru-CMs and Ru-NCMs are at 617 and
6
27 nm, respectively, which are slightly redshifted relative to
that of [(bpy) Ru(fmbpy)](PF ) . These results confirmed
that the conjugation of [(bpy) Ru
[16]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
T
N
T
E
N
N
chemicals. The selective oxidation of sulfides to sulfoxides
is one of the most fundamental processes from a synthetic
2
6 2
AHCTUNGTNERUNG( fmbpy)] CAHTUNGTRENNUNG( PF ) with
6 2
2
[17]
MPEG-PLys does not affect the luminescent properties of
the Ru complexes.
point of view. Herein, we demonstrate the oxidation reac-
tion of sulfides photocatalyzed by the Ru-CMs. The reac-
tions were performed in methanol at room temperature
without any additives. A 24 W household fluorescent lamp
with a highpass filter (l=395 nm) was used as the visible-
light source (400 to 700 nm). The concentration of the sub-
strates was approximately 12.4% (v/v). The molar ratio of
the catalyst (Ru) to substrates was 0.001. The reaction was
stopped after 24 h by ultrafiltration of the mixture, and then
the precipitate was washed with methanol (3ꢁ) and dried
under vacuum. Conversions of the reactions were deter-
The morphology of the micelles was characterized by
using scanning electron microscopy (SEM). Figure 2a shows
the SEM image of the Ru-CMs, which were cast from the
MeOH solution onto a Si wafer. It clearly shows isolated
spherical particles with an average diameter of (72.9Æ
1
mined by H NMR spectroscopy by integrating the signals
of the reactant (d=2.48 ppm) and the product (d=
[18]
2
.74 ppm) in the crude reaction mixtures.
As shown in Table 1 (entry 2), although the molar ratio of
the Ru catalyst to thioanisole was only 0.001, the Ru-CMs
were highly effective photocatalysts for the oxidation of thi-
oanisole, as a conversion of 99% was obtained. No sulfone
Figure 2. A) Scanning electron microscopy images of the Ru-CMs pre-
pared from MeOH dispersion. SEM samples were sputter coated with
1
was detected by H NMR spectroscopy, which demonstrates
the high degree of selectivity of this reaction (Figures S3
and S4, Supporting Information). These results are consis-
gold; B) particle size of the Ru-CMs in MeOH (i), H
determined by DLS.
2
O (ii), and THF ACHUTTGNENRNUG( iii)
[18]
tent with our previous report. The high conversion and se-
lectivity are comparable to those obtained with the use of
2
3
+
12.8) nm. Figure S2 (Supporting Information) shows the
their homogeneous counterparts [Ru
A
H
U
G
R
N
U
G
;
Table 1,
SEM image of a dispersion of the Ru-NCMs in water, and it
also reveals isolated micelle particles with an average diam-
eter of (50.0Æ12.5) nm, because water is a poor solvent for
the PLys(Z) block. To investigate the stability of the Ru-
CMs, the hydrodynamic particle size of the micelles was
characterized by DLS. In water, MeOH, and THF, the Ru-
CMs show clear peaks at approximately 200 nm, and this in-
dicates that the Ru-CMs can survive in polar solvents as
a result of the cross-linked core. However, there are no
clear peaks for MPEG-PLys and MPEG-PLys(Z) in the
THF solution. Consequently, the non-cross-linked block co-
entry 1]. To compare the catalytic reactivities of Ru-CMs
and Ru ACHTUNGTRENN(UNG bpy) , a kinetic study was performed at the same
3
2
+
catalyst loading. Figure S5 (Supporting Information) shows
the conversion yield as a function of reaction time. From
2
3
+
this figure, it can be seen that Ru
A
H
U
G
R
N
U
G
showed higher
catalytic activity in the oxidation of thioanisole and provid-
ed the product in 90% yield after 2 h; in contrast, the Ru-
CMs afforded the sulfoxide in 49% yield in the same
amount of time. For the Ru-CMs, the conversion increased
from 49 to 89.3% as the time was increased from 2 to 8 h.
At a longer reaction time (12 h), the conversion increased
Chem. Asian J. 2013, 8, 2807 – 2812
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Zaicheng Sun, Zhigang Xie et al.
[
a]
Table 1. Photocatalytic aerobic oxidation of sulfides.
of 98% was found, which is comparable to that obtained
with the Ru-CMs. However, the Ru-NCMs catalysts did not
survive the reaction conditions, and they could not be col-
lected by ultrafiltration after a reaction time of 24 h. This
was also proved by DLS measurements. As shown in Fig-
ure S7 (Supporting Information), although the Ru-NCMs
with a diameter of 177 nm as determined by DLS (Fig-
ure S7a, Supporting Information) are stable in H O, the mi-
2
celles collapse in the presence of a mixture of methanol and
thioanisole, and no micelle particles were detected by DLS
(
Figure S7b, Supporting Information). The poor stability of
[
b]
Entry
Catalyst
Substrate
Conv. [%]
the Ru-NCMs limits their use as heterogeneous photocata-
lysts. Therefore, the cross-linked core in the Ru-CMs pro-
vides extra shielding against metal leaching and catalyst poi-
soning, which benefit catalyst recovery and recycling.
A number of control experiments were performed to
demonstrate the heterogeneous and photocatalytic nature of
the reactions. Reactions performed in the dark and those
performed under light in the absence of the Ru-CMs
showed no conversion of thioanisole into methyl phenyl
sulfoxide (Table 1, entries 12 and 13), and only 6% of thioa-
nisole was converted if the reaction was performed under
2
+
1
2
3
4
5
6
7
8
9
Ru
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(bpy)
3
1a
1a
1a
1a
1a
2a
2a
3a
3a
4a
4a
1a
1a
1a
1a
98
99
99
98
98
94
99
60
50
53
58
0
Ru-CMs
Ru-CMs, 1st reuse
Ru-CMs, 2nd reuse
Ru-CMs, 3rd reuse
2
2
2
+
+
+
Ru
Ru-CMs
Ru(bpy)
Ru-CMs
Ru(bpy)
Ru-CMs
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(bpy)
3
3
3
ACHTUNGTRENNUNG
10
11
12
13
14
15
ACHTUNGTRENNUNG
no catalyst with light
no light with Ru-CMs
Ru-CMs under N
Ru-NCMs with light
0
6
98
a protected atmosphere of N (Table 1, entry 14). These re-
2
2
sults indicate that light, the catalyst, and oxygen are essen-
tial for this reaction. In addition, a crossover experiment
was performed to prove the heterogeneity of the Ru-CMs
catalysts. Thioanisole was used in the CMs-catalyzed reac-
tion, and 99% conversion was achieved after 24 h. The Ru-
CMs were then removed by ultrafiltration, and another sub-
strate, methyl p-tolyl sulfide, was added to the supernatant
solution. After the solution was stirred under light for 24 h,
no conversion was observed for the second substrate. This
proved that the supernatant of the Ru-CMs reaction mixture
is inactive in photocatalysis and supports the heterogeneous
nature of the Ru-CMs photocatalysts.
[
a] All of the reactions were run at room temperature for 24 h. [b] Con-
1
versions were determined by H NMR spectroscopy.
slightly to 97.1%, which indicated the reaction was almost
complete. These results show that the Ru-CMs have compa-
2
3
+
rable catalytic activity to Ru
A
H
U
G
R
N
U
G
at reaction times of 12
and 24 h. The possible reason for this result is due to the
heterogeneous nature of the Ru-CMs, and the substrates
have to diffuse into the hydrophobic core of the micelles
and then react with the catalysts. Although the core of the
Ru-CMs is cross-linked by glutaraldehyde, the substrates
and the products are able to diffuse in and out of the mi-
celles smoothly.
Conclusions
We examined the scope of the substrates for the oxidation
reaction catalyzed by the Ru-CMs. Several sulfides were ef-
ficiently oxidized under ambient conditions, and the corre-
sponding sulfoxides were produced with high conversions
In summary, a Ru catalyst was successfully integrated into
nanoscale block copolymer MPEG-PLys micelles. To stabi-
lize the micelles used as nanoreactors, glutaraldehyde was
added to cross-link the core of the micelles. Stable MPEG-
PLys micelles loaded with the Ru catalyst were obtained
and were ready dispersed into normal solvents such as
water, methanol, and THF. The Ru-CMs were shown to be
highly active, recyclable, and reusable heterogeneous photo-
catalysts in the oxidation of sulfides. This work highlights
the potential of using cross-linked micelles as a platform to
develop highly efficient heterogeneous photocatalysts for
a number of important organic transformations.
(
Table 1, entries 6–11). The catalytic reactivity of the Ru-
CMs toward these sulfides is comparable to that of the ho-
2
3
+
mogeneous Ru
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(bpy)
catalyst. Moreover, we also exam-
ined the recyclability of the Ru-CMs catalysts. The Ru-CMs
were readily recovered from the reaction mixtures by simple
ultrafiltration. The recovered catalysts showed no deteriora-
tion in conversion for the oxidation of thioanisole after recy-
cling three times (Table 1, entries 3–5). Furthermore, photo-
luminescent analysis of the supernatant showed no sign of
leaching of the Ru complexes into the solution (Figure S6,
Supporting Information). This was further supported by the
absence of Ru complexes in the supernatants of the Ru-
CMs-catalyzed reaction mixtures, as determined by ICP-MS.
Upon use of the Ru-NCMs as photocatalysts, high reactivity
for the oxidation of thioanisole was observed; a conversion
Chem. Asian J. 2013, 8, 2807 – 2812
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Zaicheng Sun, Zhigang Xie et al.
Experimental Section
Acknowledgements
Materials and General Measurements
Financial support from the National Natural Science Foundation of
China (No. 21201159, 61176016, and 21104075), the China Postdoctoral
Science Foundation Grant (No. 2012M510892), the Science and Technol-
ogy Department of Jilin Province (No. 20121801), and Returnee Startup
Fund of Jilin is gratefully acknowledged. Z.S. thanks the support of the
All reagents were purchased from commercial sources and used without
further treatment, unless indicated otherwise. H NMR spectra were re-
corded at 300 MHz with tetramethylsilane as an internal standard at
1
2
58C with a Bruker AV 300M spectrometer. The morphologies of the mi-
“
Hundred Talent Program” of the Chinese Academy of Sciences (CAS)
celles were measured by scanning electron microscopy (SEM, model
JEOL JXA-840). Size distribution of the micelles was determined by
DLS with a vertically polarized He–Ne laser (DAWNEOS, Wyatt Tech-
nology, USA). Inductively coupled plasma mass spectrometry (ICP-MS,
X series II, Thermoscientific, USA) was used for the quantitative deter-
mination of trace levels of ruthenium. Fluorescence emission spectra
were recorded with a LS-55 fluorophotometer. IR spectra were recorded
with a Vertex 70 FTIR spectrophotometer by using KBr pellets. A YM-3
ultrafiltration apparatus (cut-off Mw=30 kDa, Millipore Co., Bedford,
MA, USA) was used to recover the Ru-CMs in the recycling experiment.
and the Innovation and Entrepreneurship Program of Jilin. Z.X. thanks
the support of the Changchun Institute of Applied Chemistry (CIAC)
through a startup fund.
[
1] a) T. P. Yoon, M. A. Ischay, J. Du, Nat. Chem. 2010, 2, 527; b) S.
Sato, T. Morikawa, S. Saeki, T. Kajino, T. Motohiro, Angew. Chem.
2
010, 122, 5227; Angew. Chem. Int. Ed. 2010, 49, 5101; c) M. L.
Marin, L. Santos-Juanes, A. Arques, A. M. Amat, M. A. Miranda,
Chem. Rev. 2012, 112, 1710.
[
2] a) S. Rau, D. Walther, J. G. Vos, Dalton Trans. 2007, 915; b) C.
Wang, Z. Xie, K. E. deKrafft, W. Lin, ACS Appl. Mater. Interfaces
2012, 4, 2288; c) J. Wang, T. A. White, S. M. Arachchige, K. J.
Brewer, Chem. Commun. 2011, 47, 4451; d) J. W. Tucker, J. D.
Nguyen, J. M. R. Narayanam, S. W. Krabbe, C. R. J. Stephenson,
Chem. Commun. 2010, 46, 4985.
Synthesis of the Ru-CMs
Monomethoxy
l-lysine] [MPEG-PLys(Z)] and monomethoxy
block-poly(l-lysine) (MPEG-PLys) were synthesized according to previ-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[poly(ethylene glycol)]-block-poly[e-(benzyloxycarbonyl)-
AHCTUNGTRENNUNG
[poly(ethylene glycol)]-
ACHTUNGTRENNUNG
[
19]
ous reports. The molecular weights of MPEG and PLys(Z) were deter-
1
mined by H NMR spectroscopy to be 2000 and 3336 Da, respectively
[3] Z. Xie, C. Wang, K. E. deKrafft, W. Lin, J. Am. Chem. Soc. 2011,
133, 2056.
(
Figure S8, Supporting Information). The [(bpy)
2
Ru
A
H
U
G
R
N
U
G
A
H
U
G
R
N
N
(PF
6
)
2
com-
plex was prepared by the reaction of fmbpy with Ru
A
H
U
G
R
N
N
2
2
at 908C
[4] a) J. Qi, J. Chen, G. Li, S. Li, Y. Gao, Z. Tang, Energy Environ. Sci.
2012, 5, 8937; b) L. He, Y. Liu, J. Liu, Y. Xiong, J. Zheng, Y. Liu, Z.
Tang, Angew. Chem. 2013, 125, 3829; Angew. Chem. Int. Ed. 2013,
52, 3741; c) J. Gong, F. Zhou, Z. Li, Z. Tang, Chem. Commun. 2013,
49, 4379; d) J. Du, J. Qi, D. Wang, Z. Tang, Energy Environ. Sci.
2012, 5, 6914.
[
20]
overnight according to literature methods. The structure was confirmed
1
by H NMR spectroscopy (Figure S9, Supporting Information), which
was consistent with the literature. Typically, [(bpy)
2
Ru
6 2
ACHTUNGTRENNUNG( fmbpy)] ACHTUNTGRNNEUG( PF )
(
10 mg, 0.011 mmol) was added to a solution of MPEG-PLys (0.2 g,
0
.69 mmol amino groups) in water/THF (1:1 v/v, 20 mL), and the mixture
was then stirred at room temperature for 12 h. The Ru complex was par-
tially linked on the lysine units of MPEG-PLys through covalent bonds
through a Schiff base reaction. Then, glutaraldehyde (67 mg, 0.67 mmol)
was added to the reaction mixture to cross-link the remaining amino
groups on the lysine block. After stirring overnight, the mixture was dia-
lyzed in water for 12 h (cut-off Mw=3500 Da) to remove any impurities
and small molecules. The lyophilized powders of the cross-linked micelles
loaded with Ru complexes (Ru-CMs) were obtained after freeze drying.
The Ru content of the Ru-CMs was determined by ICP-MS to be
[5] a) S. Fçrster, M. Antonietti, Adv. Mater. 1998, 10, 195; b) J. Rodrꢂ-
guez-Hernꢃndez, F. Chꢄcot, Y. Gnanou, S. Lecommandoux, Prog.
Polym. Sci. 2005, 30, 691.
[6] a) M. L. Adams, A. Lavasanifar, G. S. Kwon, J. Pharm. Sci. 2003, 92,
1343; b) K. Kataoka, A. Harada, Y. Nagasaki, Adv. Drug Delivery
Rev. 2001, 47, 113.
[7] a) K. T. Kim, S. A. Meeuwissen, R. J. M. Nolte, J. C. M. van Hest,
Nanoscale 2010, 2, 844; b) M. J. Monteiro, Macromolecules 2010, 43,
1159; c) D. M. Vriezema, M. C. Aragones, J. A. A. W. Elemans,
J. J. A. A. Cornelissen, A. E. Rowan, R. J. M. Nolte, Chem. Rev.
2005, 105, 1445.
0
.67 wt%, and therefore, it was concluded that the weight percent of the
Ru complex in the Ru-CMs was 6.0%.
[
8] a) D. Zhao, J. Feng, Q. Huo, N. Melosh, G. H. Fredrickson, B. F.
Chmelka, G. D. Stucky, Science 1998, 279, 548; b) C. Liang, K.
Hong, G. A. Guiochon, J. W. Mays, S. Dai, Angew. Chem. 2004, 116,
Synthesis of the Ru-NCMs
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[(bpy)
2 6 2
Ru ACHTUNGTRENNUNG( fmbpy)] ACHTUNGTRENNUNG( PF ) (35 mg, 0.039 mmol) was added to a solution of
5
909; Angew. Chem. Int. Ed. 2004, 43, 5785.
MPEG-PLys(Z) (0.2 g, 0.039 mmol amino groups) in water/THF (1:1 v/v,
[
9] Y. Li, B. S. Lokitz, C. L. McCormick, Angew. Chem. 2006, 118, 5924;
Angew. Chem. Int. Ed. 2006, 45, 5792.
2
1
0 mL; see Scheme 1). The mixture was stirred at room temperature for
2 h and then dialyzed for 12 h (cut-off Mw=3500 Da). The lyophilized
[
10] R. K. OꢅReilly, C. J. Hawker, K. L. Wooley, Chem. Soc. Rev. 2006,
5, 1068.
11] a) K. B. Thurmond, T. Kowalewski, K. L. Wooley, J. Am. Chem. Soc.
996, 118, 7239; b) H. Huang, R. Hoogenboom, M. A. M. Leenen, P.
Guillet, A. M. Jonas, U. S. Schubert, J.-F. Gohy, J. Am. Chem. Soc.
006, 128, 3784.
powders of the Ru-NCMs were obtained after freeze drying. The Ru con-
tent of the Ru-NCMs was determined by ICP-MS to be 1.6 wt%, by
which the weight percent of Ru complex in the Ru-NCMs was calculated
to be 14.3%.
3
[
1
2
Procedure for the Photo-oxidation of Sulfides
[
12] a) Y. Zhao, Macromolecules 2012, 45, 3647; b) S.-I. Yusa, M. Suga-
hara, T. Endo, Y. Morishima, Langmuir 2009, 25, 5258.
Oxidation of thioanisole as an example: A 10 mL vial equipped with
a magnetic stir bar was charged with the Ru-CMs (10 mg, 0.66 mmol,
[13] a) Z. Yang, S. Zheng, W. J. Harrison, J. Harder, X. Wen, J. G. Gelo-
vani, A. Qiao, C. Li, Biomacromolecules 2007, 8, 3422; b) C. Chang,
H. Wei, J. Feng, Z.-C. Wang, X.-J. Wu, D.-Q. Wu, S.-X. Cheng, X.-Z.
Zhang, R.-X. Zhuo, Macromolecules 2009, 42, 4838; c) J. Du, S. P.
Armes, J. Am. Chem. Soc. 2005, 127, 12800.
[14] a) V. Bꢆtꢆn, A. B. Lowe, N. C. Billingham, S. P. Armes, J. Am.
Chem. Soc. 1999, 121, 4288; b) V. Bꢆtꢆn, N. C. Billingham, S. P.
Armes, J. Am. Chem. Soc. 1998, 120, 12135.
0
.001 equiv.), thioanisole (62 mL, 0.5 mmol, 1.0 equiv.), and methanol
(
(
0.5 mL). A 24 W household fluorescent light bulb with a highpass filter
l=395 nm) was used as the visible-light source. The reaction mixture
was stirred at room temperature in air at a distance of approximately
À2
5
cm from the lamp (the irradiance was ꢀ17.5 Wm for the distance).
After 24 h, the reaction was complete, because of its nanoscale size, and
the Ru-CMs could be recovered easily by passing the reaction solution
through an ultrafiltration membrane with a molecular weight cutoff of
[15] a) B. M. Rossbach, K. Leopold, R. Weberskirch, Angew. Chem.
2006, 118, 1331; Angew. Chem. Int. Ed. 2006, 45, 1309; b) Y. Liu, Y.
Wang, Y. Wang, J. Lu, V. PiÇꢇn, M. Weck, J. Am. Chem. Soc. 2011,
133, 14260.
1
3
0000 Da. The H NMR spectrum of the reaction mixture was recorded,
and the integrated area ratio between the signals of the substrate and
product was used to calculate the conversion yields.
Chem. Asian J. 2013, 8, 2807 – 2812
2811
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Zaicheng Sun, Zhigang Xie et al.
[
16] a) M. C. CarreÇo, Chem. Rev. 1995, 95, 1717; b) I. Fernꢃndez, N.
Khiar, Chem. Rev. 2003, 103, 3651.
[19] A. Harada, K. Kataoka, Macromolecules 1995, 28, 5294.
[20] M. Li, C. Zhan, M. Nie, G. Chen, X. Chen, J. Inorg. Biochem. 2011,
105, 420.
[
17] L. Chen, Y. Yang, D. Jiang, J. Am. Chem. Soc. 2010, 132, 9138.
18] a) W. Li, W. Zhang, X. Dong, L. Yan, R. Qi, W. Wang, Z. Xie, X.
Jing, J. Mater. Chem. 2012, 22, 17445; b) W. Li, Z. Xie, X. Jing,
Catal. Commun. 2011, 16, 94.
[
Received: May 15, 2013
Published online: August 12, 2013
Chem. Asian J. 2013, 8, 2807 – 2812
2812
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim