A highly sensitive and selective visible-light excitable luminescent probe for singlet oxygen based on a dinuclear ruthenium complex

Article abstract of DOI:10.1039/c6dt04813g

A dinuclear Ru(ii) complex of [(bpy)₂Ru(H₂ipaip)Ru(bpy)₂]Cl₄ {bpy = 2,2′-bipyridine, H₂ipaip = 2-(9-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)anthracen-10-yl)-1H-imidazo[4,5-f][1,10]phenanthroline} is newly synthesized and characterized. Singlet oxygen sensing and ground- and excited-state acid-base properties of this complex are studied. The results indicated that the complex acted as a highly sensitive and selective luminescent probe for singlet oxygen (¹O₂) in neutral and alkaline aqueous media under visible light excitation at 458 nm, resulting in 5.2- and 7.6-fold emission enhancement, respectively. This probe has advantages of visible light excitation, low singlet oxygen detection limits of 2.7-3.1 nM and high water solubility, thus holding great potential for applications in biological systems.

Full text of DOI:10.1039/c6dt04813g

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PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
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a Zr-metal–organic
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A highly sensitive and selective visible-light excitable
luminescence probe for singlet oxygen based on a dinuclear
ruthenium complex
Received 00th January 20xx,
Accepted 00th January 20xx
a,b
a
a
a,*
DOI: 10.1039/x0xx00000x
Hong-Ju Yin, Yan-Ju Liu, Jie Gao and Ke-Zhi Wang
www.rsc.org/
A dinuclear Ru(II) complex of [(bpy)
2
Ru(H
2
ipaip)Ru(bpy)
2
]Cl
4
{bpy = 2,2′-bipyridine, H
is
2
ipaip = 2-(9-(1H-imidazo[4,5-
newly synthesized and
f][1,10]phenanthrolin-2-yl)anthracen-10-yl)-1H-imidazo[4,5-f][1,10]phenanthroline}
characterized. Singlet oxygen sensing and ground- and excited-state acid-base properties of this complex are studied. The
1
results indicated that the complex acted as a highly sensitive and selective luminescence probe for singlet oxygen ( O
2
) in
neutral and alkaline aqueous media under visible light excitation at 458 nm, resulting in 5.2- and 7.6-fold emission
enhancement, respectively. This probe that has advantages of visible light excitation, low singlet oxygen detection limits of
2
.7-3.1 nM and high water solubility, holds great potential for applications in biological systems.
1
2,13
luminescence at1270 nm,
frequently yielded equivocal
1
1
. Introduction
results. The absorption spectrophotometric detection of O2
was also reported, e.g. by monitoring a reduction of
1
The Singlet oxygen ( O
2
), the lowest excited state of the
absorption intensity of 9,10-diphenylanthracene at 335 nm
1
caused by specific reaction with O
dioxygen molecule, has aroused much interest as a biological
and chemical oxidant for biological and environmental
1
systems. In the biological systems, it is considered to be an
2
to form a thermostable
1
4
endoperoxide. However, this method is restricted by its low
sensitivity in the absorbance measurement. The
important toxic species in vivo since it can oxidize various kinds
1
of biological molecules such as DNA, proteins, and lipids.
1
-3 chemiluminescence and photoluminescence
5
8-10,16-23
could be
1
2
highly sensitive, cost effective and non-invasive to detect O .
1
A highly selective chemiluminescence probe for O
Furthermore, it plays a key role in the induction of gene
4
expression, the cell signaling cascade, changes of the
2
based on a
5
mitochondrial membrane pore transition, and the bactericidal
reactive anthracene fluorophore grafted with an electron-rich
1
5
6
response of certain antibodies . On the other hand, the
tetrathiafulvalene unit was also reported. However, this
probe is unsuitable for use in some biosystems due to its poor
water solubility. Nagano’s group reported two anthracene-
containing xanthenes for ultraviolet-excitable sensitive
1
artificial photochemical generation of O
2
has been used to
destroy malignant cancer cells or tissues as a cancer treatment
7
protocol in photodynamic photochemotherapy.
1
Due to the significant importance of O
,8
1
16,17
.
fluorescence probing of O
2
These probes suffer from UV
2
in photobiological and
excitation, and their usefulness at lower pH where the
photochemical processes, the stable and highly selective and
1
nonfluorescent endoperoxides are formed by reaction with
1
sensitive probes for
2
O have attracted much interest, and
1
8-23
2
O . In recent decades, significant progress has been made by
several methods for detecting O
2
have been developed.
emission at 1270 nm is a
noninvasive and specific method, but the weak signals caused
3
+
3+
Yuan’s group on Eu and Tb chelate-based O
1
1
2
luminescence
The direct monitoring of
O
2
1
8-21
probes.
These probes were demonstrated to have
1
advantages of higher water solubility, sensitivity and large
Stokes shift. However, these probes need ultraviolet light
excitation, which limits their applications in biosystems. We
by the lower
2
O emission efficiency, make quantitative
1
detection of very small amounts of
1
impossible in any medium. Although indirect detection of O
2
O by this method
1
1
2
I
have reported a visible light excitable Re complex-based highly
by chemical analysis of its reaction products was reported to
1
be specific and much more sensitive than detection of the O
sensitive and selective luminescence probe Re(CO)
3
Cl(aeip)
2
{
[
aeip
=
2-(anthracen-9-yl)-1-ethyl-imidazo[4,5-f]
22
1
1,10]phenanthroline} for O
2
,
which may be preferable for
biological application as it minimizes cell damage in view of its
the visible excitation. The probe is the first example of
1
transition-metal-complex-based O
2
luminescence probe with
1
visible light excitation. However, its water solubility and O
2
sensing sensitivity still need further improvements. The other
transition metal complexes such as Ru(II) or Ir(III) polypyridyl
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1
complexes etc. have been well known for their intriguing used in order to avoid photosensitized formation of O
2
that is
2
3-25
24 1
optical sensing capacity,
paid on these metal complexes in this regard . In the present generated from the H
work, we report on visible light excitable singlet oxygen or from the H /MoO
Hydroxyl radical (·OH) was generated in the Fenton system
however, little attention has been self-trapped by the Ru(II) complex.
2
O was chemically
2
6
34
2 2
O /NaOCl system in the neutral buffer
2
–
35,36
2
O
2
4
system in the alkaline buffer
.
II
luminescence sensing properties based on a new dinuclear Ru
complex (see Scheme 1).
3
7
from ferrous ammonium sulfate and hydrogen peroxide.
solutions were obtained by direct dilution of
commercially available hydrogen peroxide with the neutral
2 2
H O
2
0
–
buffer or the alkaline buffer. Peroxynitrite (ONOO ) was
synthesized from sodium nitrite and H , and the solution
was treated with MnO to eliminate the excess H . The
2
. Materials and Methods
2 2
O
2
8-30
9
,10-Anthracenedicarboxaldehyde,
3
1,10-phenanthroline-
32
2
–
2 2
O
1
concentration of ONOO was determined by measuring the
absorbance at 302 nm with a molar extinction coefficient of
2 2 2
5,6-dione, and cis-[Ru(bpy) Cl ]·2H O (bpy = 2,2′-bipyridine)
were synthesized according to the literature methods.
–
670 M cm .
1
–1 38,39
1
Synthesis of 2-(9-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-
2.3. Physical measurements
yl)anthracen-10-yl)-1H-imidazo[4,5-f][1,10]phenanthroline
Emission spectra were obtained with Cary Eclipse EL07033804
Spectrofluorimeter. Absorption spectra were measured on a
GBC Cintra 10e UV/Vis spectrophotometer. All pH
measurements were performed with a pH-3c digital pH-meter
(
H
2
ipaip)
This was synthesized according to a modified synthetic method
3
3
for an analogous compound. Briefly, a solution of 9,10-
anthracenedicarboxaldehyde (78 mg, 0.33 mmol), 1,10-
phenanthroline-5,6-dione (140 mg, 0.66 mmol), and
ammonium acetate (500 mg, 5.4 mmol) in 20 ml glacial acetic
acid was refluxed for 6 h. After cooling to room temperature,
the reaction mixture was added into 100 mL water, and was
neutralized with ammonia. The yellow solid precipitated was
collected by filtration, washed with methanol and vacuum
dried. The product was not subject to further purification and
was directly used for following synthesis due to its poor
solubility in common organic solvents.
(
Shanghai Lei Ci Device Works, Shanghai, China) with a
1
combined glass-calomel electrode. H NMR spectra were
obtained on a Bruker DRX-400 spectrometer. Positive-ion
Matrix-assisted laser desorption/ionization-time of flight
(MALDI-TOF) mass spectrum was obtained using an API Q-star
pulsar I/oMALDI/QQ-TOF mass spectrometer. Elemental
analyses were performed on a Vario EL elemental analyzer.
Synthesis of [(bpy)
2
Ru(H
2
ipaip)Ru(bpy)
ipaip (31 mg, 0.05 mmol) and
O (52 mg, 0.1 mmol) in 10 ml ethylene glycol 3.1.
. Upon cooling to room characteristics and acid-base properties
2 4
]Cl
3
. Results and discussion
A
suspension of H
2
Ru(bpy)
2
Cl
2
·2H
2
Synthesis,
characterization,
common
spectral
was refluxed for 12 h under N
temperature, the solution was filtered, and a 4-fold excess of
saturated sodium perchlorate aqueous solution was added. A according to Scheme 2. Briefly, H
2
II
The binuclear Ru complex was readily synthesized
ipaip was first prepared via a
2
red precipitation was collected by filtration. The crude product condensation reaction between 1,10-phenanthroline-5,6-
was purified by column chromatography on silica gel, and was dione and anthracene-9,10-dicarbaldehyde in acetic acid
eluted with dichloromethane/methanol (25:1, v/v). The red solvent in the presence of ammonium acetate as nitrogen
solid product was further purified by recrystallization from source. The condensation product is only sparingly soluble in
acetonitrile/ether to afford a red crystalline solid (0.045 g, common organic solvents, making further purification
5
6.9% yield). Anal. Calc. for C80
H
54Cl
4
N
16Ru
2
•4CH
3
CN•18.5H
2
O: impossible. However, direct reaction of
Cl ·2H O in ethylene glycol at reflux and subsequent
) δ/ppm: 9.20 (d, J = 7.4 Hz, 2H), silica gel column chromatography purification proved to be
.03 (d, J = 6.9Hz, 2H), 8.91 (d, J = 8.3 Hz, J = 12.0 Hz, 8H), smooth in reasonable yield with satisfactory purity as
2
H ipaip with
C, 50.79; H, 4.99; N, 13.46%. Found: C, 50.56; H, 4.84; N, 13.35. Ru(bpy)
2
2
2
1
H NMR (400 MHz, DMSO-d
6
9
8
5
1
2
1
.25 (t, J = 8.0 Hz, 4H), 8.16 (m, 8H), 7.97 (s, 8H), 7.91 (d, J = evidenced by elemental analysis, and H NMR (see Fig. S1a†)
.4 Hz, 4H), 7.72 (d, J = 5.5 Hz, 4H), 7.64 (m, 8H), 7.43 (s, 4H). and positive-ion MALDI-TOF mass spectroscopy. The
－
4+
1
Anal. Calc. for MALDI-TOF MS: m/z = 360.3 ([M-4Cl ] ); integrated intensities of the proton resonance signals in the H
－ 4+
Found: m/z 360.9 ([M-4Cl ] ).
2 2 2 4
NMR spectrum of [(bpy) Ru(H ipaip)Ru(bpy) ]Cl corresponds
to 54 protons, being in agreement with the anticipation.
2
.3. Reactions of [(bpy)
oxygen species (ROS)
All the reactions were carried out in 50 mM Tris-HCl buffer active and exchange quickly between the two nitrogen atoms
2
Ru(H
2
ipaip)Ru(bpy)
2
]Cl
4
with reactive However, the proton resonances for NH of the two imidazole
2
rings of H ipaip were not observed, because the protons are
4
0
of pH 7.00 or 50 mM carbonate buffer of pH 10.5 with fixed Ru of each imidazole ring. The mass spectrum (see Fig. S1b†)
1
complex concentrations (5.00
μ
M
for
O
2
sensing showed that a peak was seen at m/z 360.9, consistent with a
- 4+
sensing selectivity theoretical value of m/z 360.3 for ([M-4Cl ] ). The
1
experiments, and 1.67 μM for
O
2
experiments) for 15 min at room temperature. The freshly experimental data of elemental analysis well coincides with
prepared and Ar-bubbled Ru(II) complex solutions should be the theoretical ones. UV-Vis absorption spectra (Fig. S2†) of
2
| J. Name., 2012, 00, 1-3
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the complex in pH 7.0 or 10.4 show typical metal (Ru(II))-to- formed quantitatively by the reaction of two
2 2
H O
2
-
21,35,36
ligand (bpy and H
absorption (λmax
dominant absorption features of anthryl moiety over 350-400 absorption and emission spectrophotometric titration
2
ipaip or ipaip ) charge transfer (MLCT) molecules)
in neutral and alkaline buffer respectively
4
-1
-1
II
=
460 nm, ε = 3.2 ×10 M ˖cm ) and with the bimetallic Ru complex, were monitored by UV-Vis
4
-1
-1
nm (
intensity of the dinuclear complex approximately doubles that clearly shown in Fig. 2, successive additions of O
of analogous mononuclear complex of [Ru (bpy) (aip)](ClO gradual decreases in anthryl moiety-based intraligand π-π
bpy = 2,2′-bipyridine, aip = 2-(9-anthryl)-1H-imidazo[4,5- absorption bands at 356, 375 and 395 nm until almost
ε = 2.7 × 10 M ˖ cm ). As anticipated, the absorption techniques, and the results are shown in Fig. 2 and Fig. 3. As
1
2
caused
2
4 2
)
{
3
3
f][1,10]phenanthroline}. Ground- and excited-state acid-base disappearance, indicating that the Ru(II) complex acted as a
1
properties of the complex were studied by UV-Vis
2
O trap to form endoperoxide as shown in Scheme 4. It is
spectrophotometric pH titration techniques. UV-Vis absorption noteworthy that the MLCT band also experienced such
1
spectra of the dimetallic complex showed less sensitive pH- intensity reduction as O
2
was successively added, indicating
induced spectral changes (see Fig. 1) than previously reported that the anthryl moiety, in addition to bpy, is surely involved in
II
wo
mononuclear
analogous
Ru(II)
complexes
of the MLCT process. As shown in Fig. 3, the binuclear Ru
3
3
1
{Hpip = 2- complex in the absence of O , is very weakly luminescent as
[
Ru(bpy)
2
(aip)](ClO
4
)
2
and [Ru(bpy)
2
(Hpip)](ClO
4
)
2
2
4
phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (Hpip)} . Upon excited with visible light at 458 nm, because the anthryl
1
3
increasing pH from 0.10 to 3.50, the absorption intensities for moiety that has a triplet state lying below emitting MLCT
2
+
the bands at ~280 and ~340 nm were reduced, and those at state of [Ru(bpy)
2
(ip)] core, effectively quenches the MLCT
~
460 nm were increased with appearance of an isosbestic emitting state through exchange triplet–triplet intramolecular
37
II
point at 445 nm; in contrast, further increases in pH from 6.20 energy transfer, as revealed in analogous Ru complexes.
II
to 13.0 slightly decayed the absorption intensities at
460 nm, but enhanced those at 340 nm with appearance of remarkably enhanced in the presence of
an isosbestic point at 375 nm. Two ground-state ionization neutral and alkaline buffers by the maximum emission
constants of pKa1 = 2.40 ± 0.07 and pKa2 = 8.18 ± 0.06 were intensity enhancement factors (I/I ) of 5.4 and 7.6 respectively
obtained by nonlinear sigmoidal fit of the data in the insets of due to the termination of triplet–triplet intramolecular energy
Fig. 1a and Fig. 1b, which are reasonable as compared to pK transfer caused by the endoperoxide formation, similarly to
values previously reported for mononuclear analogous previously reported anthryl group-containing
~280 and However, the emission of the Ru complex (λem = 610 nm) was
1
~
~
2
O in both the
0
a
1
O
2
optical
1
4,16,18-23
complexes [(bpy)
2
Ru(aip)](ClO
4
)
2
(pKa1 =1.27 ± 0.03, pKa2
2+
=
=
sensors. As shown in Fig. 4, calibration curves for the
1
determination of O in both the neutral and alkaline buffers
2
3
.69 ± 0.08) and [Ru(bpy) (Hpip)] (pKa1 = 2.32 ± 0.07, pKa2
3
8
2
4
0
1
2
8.50 ± 0.03). These two acid ionization constants observed as expressed in plots of logI vs. log [ O ], show good linearity
1
for the dinuclear complex can be ascribed to two di- with equations of logI = 3.56 + 0.328lg [ O
2
] (n = 15, r = 0.986)
] (n = 15, r = 0.993) respectively.
Fig. S3†, pH-dependent emission spectra can be deconvoluted To investigate the reaction specificity of [Ru (bpy) (H ipaip)]Cl
2
, the reactions of the Ru complex with several ROS ( O ,
1
deprotonated processes as described in Scheme 3. As shown in and logI = 3.82 + 0.403log [ O
2
2
4
2
4
1
II
1
into
three
independent
excited-state to O
2
−
protonation/deprotonation processes, which are in sharp ·OH, H
2 2
O , and ONOO ) were also examined in the two buffers,
contrast to two ground-state ones. This is probably arisen from and the results are shown in Fig. 5. Compared with the
excited-state conformational changes as compared to the remarkably increase in emission intensity after the reaction of
1
ground-state one. Upon increasing pH from 0.0 to 7.0, a [(bpy)
hypsochromic shift by 12 nm in emission maxima and emission emission
enhancement by a factor of 1.6 were elicited. The increases in [(bpy) Ru(H
2
Ru(H
2
ipaip)Ru(bpy)
intensities
2
]Cl
4
with
after
with ONOO , ·OH, and H
2
O , the changes in the
the
reaction
of
in
−
2
2
ipaip)Ru(bpy)
2
]Cl
4
2
O
2
pH from 7.0 to 10.25 resulted in a bathochromic shift by 6 nm the concentration of 0.53 µM for 15 min were very small,
and emission intensity reduction by a factor of 1.5; further which is attributed to the specific reactivity of the anthracene
1
rises in pH from 10.25 to 12.75 almost unaltered emission unit toward O
15-17
2
.
Thus, we can conclude that the binuclear
1
II
energy but induced a small intensity increase by 0.3 folds. The Ru complex is a specific luminescence probe for
O
2
in
1
above-mentioned three-step emission spectral changes can be aqueous media. The values of O
2
detection limit (DL) of the
II
due to one excited-state di-deprotonation/di-protonation binuclear Ru complex in the neutral and alkaline media,
processes in the acidic range and two excited-state mono- calculated as the concentrations corresponding to three-fold
deprotonation/mono-protonation processes in the basic standard deviations of the background signal, are 3.12 nM and
range, as depicted in Scheme S4†. By nonlinear sigmoidal fit of 2.7 nM, respectively. The luminescence properties of the
II
1
the data in the insets of Fig. S3a-c†, three excited-state acid binuclear Ru complex and some representative
*
O
2
ionization constant values were roughly derived to be pKa1
=
luminescence probes are compared in Table 1. As seen in
Table 1, since the complex we studied here is soluble in water,
*
.02 ± 0.07, pKa2 = 8.12 ± 0.06 and pKa3 = 11.7 ± 0.1.
*
3
1
2
it could be applied as O sensor in fully aqueous systems
1
.2. Detection of O
3
2
with [Ru
2
(bpy)
4
(H
2
ipaip)]Cl
4
as a probe in including biosystems, while most of previously reported
aqueous buffer
probes have to be used in organic solvents. The DL values
1
2 2 4 2 4
Reactions of O that was in-situ generated by the NaOCl- observed for [Ru (bpy) (H ipaip)]Cl are ~20-fold lower than a
3
2
2-
-H
35,36
1
systems (one O
H
2
O
2
and MoO
4
2
O
2
2
molecule can be DL value of 76 nM of the DAET probe by chemiluminescence
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1
7
3+
3+
method and lower than the Eu - and Tb -complex-based
6
Jr, P. Wentworth, L. Jones, A. Wentworth, X. Zhu, N. Larsen,
I. Wilson, X.Xu, W. Goddard III, K. Janda and A. Eschenmoser,
Science, 2001, 293, 1806.
S. Nonell and S. Braslavsky, Meth. enzy., 2000, 319, 37.
X. Q. Chen, F. Wang, J. Y. Hyun, T. W. Wei, J. Qiang, X. T. Ren,
I. Shin and J. Yoon, Chem. Soc. Rev., 2016, 45, 2976.
N. Soh, Anal. Bioanal. Chem., 2006, 386, 532.
1
8-21
I
and the Re complex
luminescence probes (2.8~10.8 nM)
Re(CO) Cl(aeip) {where aeip
3
=
2-(anthracen-9-yl)-1-ethyl-
7
8
imidazo[4,5-f][1,10]phenanthroline}reported by us (4.9 nM),
even much less than a DL value of 170 nM previously reported
2+ 26
(An-bpy)] ,
for an analogous Ru(II) complex of [Ru(bpy)
2
9
II
indicating that the Ru complex is a highly sensitive
10 X. Q. Chen, X. Z. Tian, I. Shin and J. Yoon, Chem. Soc. Rev.,
2011, 40, 4783.
1
1
2
luminescence probe for O . The excitation wavelength for the
II
binuclear Ru complex is within the visible region (458 nm),
1 T. Keszthelyi, D. Weldon, T. Andersen, T. Poulsen, K.
Mikkelsen and P. Ogilby, Photochem. Photobio., 1999, 70
531.
which means it is preferable for biological application as a
result of minimal cell damage, while almost the excitation 12 J. Wassell, S.Davies, W. Bardsley and M. Boulton, J. Bio.
Chem., 1999, 274, 23828.
wavelengths used by previously reported probes are within
1
3 A. Morita, T. Werfel, H. Stege, C. Ahrens, K. Karmann, M.
Grewe, S. Grether-Beck, T. Ruzicka, A. Kapp and L. Klotz, J.
Exper. Med., 1997, 186, 1763.
the ultraviolet region (316~390 nm).
1
4 M. J. Steinbeck, A. U. Khan, M. J. Karnovsky, J. Biol. Chem.,
1992, 267, 13425.
15 X. H. Li, G. X. Zhang, H. M. Ma, D. Q. Zhang, J. Li and D. B.
4
. Conclusions
Ⅱ
A new anthryl moiety-containing dinuclear Ru complex is
Zhu, J. Am. Chem. Soc., 2004, 126, 11543.
6 N. Umezawa, K. Tanaka, Y. Urano, K. Kikuchi, T. Higuchi and
T. Nagano, Angew. Chem. Int. Ed., 1999, 38, 2899.
7 K. Tanaka, T. Miura, N. Umezawa, Y. Urano, K. Kikuchi, T.
Higuchi and T. Nagano, J. Am. Chem. Soc., 2001, 123, 2530.
synthesized and characterized. This complex can rapidly react
1
with O
1
1
1
1
2
2
to from its endoperoxides, resulting in remarkable
changes in emission and UV-vis absorption spectra in both
1
neutral and alkaline buffers. The detections of
2
O by
8 B. Song, G. Wang and J. Yuan, Chem. Commun., 2005, 28
553.
,
monitoring the linear dependence of the emission intensities
1
on O concentrations in the neutral and the alkaline buffers
2
3
9 B. Song, G. L. Wang, M. Q. Tan and J. L. Yuan, New J. Chem.,
2005, 29, 1431.
0 B. Song, G. L. Wang, M. Q. Tan and J. L. Yuan, J. Am. Chem.
Soc., 2006, 128, 13442.
21 M. Q. Tan, B. Song, G. L. Wang and J. L. Yuan, Free Radic.
Biol. Med. 2006, 40, 1644.
2 Y. J. Liu and K. Z. Wang, Eur. J. Inorg. Chem., 2008, 33, 5214.
were found to be very sensitive with very low detection limits
of 3.1 and 2.7 nM respectively, which are favorably compared
1
to previously reported O
2
luminescence sensors. Moreover,
1
the dinuclear complex exhibited high selectivity to
2
O as
compared to its responses to the other reactive oxygen species
−
2
, and ONOO . Still another, the dinuclear 23 M. Ji, W. H. Wu, W. T. Wu, P. Song, K. L. Han, Z. G. Wang, S. S.
1
of O , ·OH, H O
2 2 2
Liu, H. M. Guo and J. Z. Zhao, J. Mater. Chem., 2010, 20, 1953.
4 J. Z. Zhao, W. H. Wu, J. F. Sun and S. Guo, Chem. Soc. Rev.,
complex has advantages of high water solubility, visible light
excitation and pH insensitivity of its UV-vis absorption spectra.
The above-mention characteristics make the dinuclear
complex promising for practical application as luminescent
singlet oxygen sensor in biological systems.
2
2
2
013, 42, 5323.
5 M. J. Li, Z. H. Lin, X. D Chen and G. N. Chen, Dalton Trans.,
014, 43, 11745.
2
26 Z. Q. Ye, B. Song, Y. J. Yin, R. Zhang and J. L. Yuan, Dalton
Trans., 2013, 42, 14380.
2
2
2
7 S. Das, S. Karmakar, S. Mardanya and S. Baitalik, Dalton
Trans., 2014, 43, 3767.
8 D. Ryu, E. Park, D. S. Kim, S. H. Yan, J. Y. Lee, B. Y. Chang and
K. Y. Ahn, J. Am. Chem. Soc., 2008, 130, 2394.
9 H. S. Kim, H. S. Moon and D. O. Jang, Superamol. Chem.,
Acknowledgements
The authors thank the National Natural Science Foundation of
China (21541010 and 20971016), Program for Changjiang
Scholars and Innovative Research Team in University, Key
Laboratory of Radiopharmaceuticals, Ministry of Education,
the Fundamental Research Funds for the Central Universities
2
006, 18, 97.
3
3
0 B. H. Klanderman, J. Org. Chem., 1996, 31, 2618.
1 K. Kloc, J. Mlochowski and Z. Szulc, J. Prakt. Chem., 1977, 319
959.
,
(
2014KJJCB08) and Analytical and Measurements Fund of 32 B. P. Sullivan, D. J. Salmon and T. J. Meyer, Inorg. Chem.,
1
978, 17, 3334.
3 M. J. Han, L. H. Gao and K. Z. Wang, New J. Chem., 2006, 30
08.
4 A. M. deleteHeld, D. J. Halko and J. K. Hurst, J. Am. Chem.
Soc., 1978, 100, 5732.
5 J. M. Aubry and B. Cazin, Inorg. Chem., 1988, 27, 2013.
Beijing Normal University are greatly acknowledged.
3
3
3
2
Notes and references
36 V. Nardello, S. Bogaert, P. L. Alsters and J. M. Aubry,
Tetrahedron Lett., 2002, 43, 8731.
1
2
3
4
C. Schweitzer and R. Schmidt, Chem. Rev. 2003, 103, 1685.
R. K. Schneider, Sens. Actuators B, 2003, , 82.
M. J. Davies, Biochem. Biophy. Res. Comm., 2003, 305, 761.
S. W. Ryter and R. M.Tyrrell, Free. Rad. Bio. Med., 1998, 24,
3
3
3
7 G. J. Wilson, W. H. F. Sasse and A. W. H. Mau, Chem. Phys.
Lett., 1996, 250, 583.
8 K. Setsukinai, Y. Urano, K. Kakinuma, H. J. Majima and T.
Nagano, J. Biol. Chem., 2003, 278, 170.
9 S. Miyamoto, G. R. Martinez, A. P. B. Martins, M.H.G.
9
1520.
C. Beghetto, C. Renken, O. Eriksson, G. Jori, P. Bernardi and
F. Ricchelli, Eur. J. Biochem., 2000, 267, 5585.
5
Medeiros and P. D. Mascio, J. Am. Chem. Soc., 2003, 125
4
,
510.
4
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4
0 L. F. Tan, H. Chao, Y. J. Liu, H. Li, B. Sun and L. N. Ji, Inorg. 41 J. Gao, Z. P. Wang, C. L. Yuan, H. S. Jia and K. Z. Wang,
Chim. Acta, 2005, 358, 2191. Spectrochim. Acta A, 2011, 79, 1815.
This journal is © The Royal Society of Chemistry 20xx
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Figure, Scheme and Table captions
Fig. 1. Changes in the UV-vis absorption spectra of [Ru (bpy) (H ipaip)]Cl upon increasing pH from 0.10 to 3.50 (a)
2
4
2
4
and from 6.20 to 13.0 (b).
1
Fig.2. Changes in UV-visible spectra of [Ru
2
(bpy)
4
(H
2
ipaip)]Cl
4
(5.00 µM) upon successive reactions with O
2
1
generated (a) from the H
2
O
2
/NaOCl (10 mM) system in 50 mM Tris-HCl buffer of pH 7.00 ([ O
2
] = 0∼4.35 mM), and
1
(
b) from the H /Na MoO
2
O
2
2
4
(10 mM) system in 0.1 M carbonate buffer of pH 10.5 ([ O
2
] = 0∼1.05 mM).
2 4 2 4
Fig.3. Changes in emission spectra (λex = 458 nm) of the [Ru (bpy) (H ipaip)]Cl (5.00 µM) upon successive
1
1
additions of O
2
generated (a) from the H
2
O
2
2
/NaOCl (10 mM) system in 50 mM Tris-HCl buffer of pH 7.00 ([ O ] =
1
0
0
∼4.35 mM), and (b) from the H O /Na MoO (10 mM) system in 0.1 M carbonate buffer of pH 10.5 ([ O ] =
2
2
2
4
2
1
∼1.05 mM). Inset: plots of emission intensity at 609 nm vs. concentrations of O
2
.
1
Fig.4. Calibration curves for detection of O
2
derived from the luminescence intensities at 609 nm for
2 4 2 4
[Ru (bpy) (H ipaip)]Cl (5.00 µM) in (a) neutral and (b) alkaline media.
2 4 2 4
Fig.5. Luminescence intensities of [Ru (bpy) (H ipaip)]Cl (1.67 µM) reacted with different reactive oxygen species
([ROS] = 0.53 μM) in (a) 50 mM Tris-HCl buffer of pH 7.00, and (b) 0.1 M carbonate buffer of pH 10.5.
SCHEME TITLES.
Scheme 1. Molecular structure of [(bpy) Ru(H ipaip)Ru(bpy) ] .
4
+
2
2
2
2 2 2 4
Scheme 2. The synthetic route to [(bpy) Ru(H ipaip)Ru(bpy) ]Cl .
4
+
Scheme 3. Ground-state protonation/deprotonation processes of [(bpy)
2
2 2
Ru(H ipaip)Ru(bpy) ] .
4
+
1
2 2 2 2
Scheme 4. The reaction of [(bpy) Ru(H ipaip)Ru(bpy) ] with O .
Table 1
1
The comparisons of O
2
luminescent detection parameters of excitation wavelength (
λ
ex), detection limit (DL) and
emission intensity (quantum yield) enhancement factor.
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4
+
2 2 2
Scheme 1. Molecular structure of [(bpy) Ru(H ipaip)Ru(bpy) ] .
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Journal Name
2 2 2 4
Scheme 2. The synthetic route to [(bpy) Ru(H ipaip)Ru(bpy) ]Cl .
8
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4
+
2 4 2
Scheme 3. Ground-state protonation/deprotonation processes of [Ru (bpy) (H ipaip)] .
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Journal Name
4
+
1
2 2 2 2
Scheme 4. The reaction of [(bpy) Ru(H ipaip)Ru(bpy) ] with O .
1
0 | J. Name., 2012, 00, 1-3
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Fig. 1. Changes in the UV-vis absorption spectra of [(bpy) Ru(H ipaip)Ru(bpy) ]Cl upon
2
2
2
4
increasing pH from 0.10 to 3.50 (a) and from 6.20 to 13.0 (b).
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Fig.2. Changes in UV-visible spectra of
[
(bpy)
reactions with O
system in 50 mM Tris-HCl buffer of pH 7.00 ([ O
and (b) from the H /Na MoO (10 mM) system in 0.1 M
carbonate buffer of pH 10.5 ([ O
2
Ru(H
2
ipaip)Ru(bpy)
2
]Cl
4
(5.00 µM) upon successive
1
2
generated (a) from the H
2 2
O
1
/NaOCl (10 mM)
2
] = 0~4.35 mM),
2
O
2
2
4
1
2
] = 0~1.05 mM).
1
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Fig.3. Changes in emission spectra (λ = 458 nm) of
ex
the [(bpy)
successive additions of O
/NaOCl (10 mM) system in 50 mM Tris-HCl buffer
2
Ru(H
2
ipaip)Ru(bpy)
2
]Cl
4
(5.00 µM) upon
1
2
generated (a) from the
2 2
H O
1
of pH 7.00 ([ O
2
] = 0∼4.35 mM), and (b) from the
H O /Na MoO (10 mM) system in 0.1 M carbonate
2
2
2
4
1
buffer of pH 10.5 ([ O ] = 0∼1.05 mM). Inset: plots of
2
1
emission intensity at 609 nm vs. concentrations of O
2
.
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1
2
Fig.4. Calibration curves for detection of O derived from the
luminescence intensities at 609 nm for
[(bpy)
2 2 2 4
Ru(H ipaip)Ru(bpy) ]Cl (5.00 µM) in (a) neutral and (b)
alkaline media.
1
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Fig.5. Luminescence intensities of
(bpy) Ru(H ipaip)Ru(bpy) ]Cl (1.67 µM) reacted with
[
2
2
2
4
different reactive oxygen species ([ROS] = 0.53 μM) in (a)
0 mM Tris-HCl buffer of pH 7.00, and (b) 0.1 M carbonate
5
buffer of pH 10.5.
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Table 1
Journal Name
1
The comparisons of O
2
luminescent detection parameters of excitation wavelength (
λ
ex), detection limit (DL) and
emission intensity (quantum yield) enhancement factor.
Compound
λex
DL
I/I0
(Φ
/Φ0
)
Ref
(
nm)
(nM)
[
a]
[c]
[c]
DAET
390
335
335
316
410
76
–(54)
[17]
[18]
[20]
[21]
[22]
3
+[a]
[b]
[b]
ATTA-Eu
MTTA-Eu
2.8
11(17.0)
3
+[a]
[b]
[b]
3.8
–(15.3)
–(22.8)
3
+[a]
[b]
[b]
PATA-Tb
10.8
10.5
[
b]
[b]
Re(CO) Cl(aeip)
3.4(18.5)
3
[
c]
[c]
4
.9
4.3(8.0)
2
+
[b]
[b]
[
[
[
Ru(bpy)
2
(An-bpy)]
460
458
170
22(7.7)
[26]
4
+
[b]
[b]
[c]
(bpy) Ru(H ipaip)Ru(bpy) ]
2.7
5.2(7.6)
7.6(8.8)
This
2
2
2
work
[
c]
3
.1
a] DAET = 4,5-dimethylthio-4'-[2-(9-anthryloxy)ethylthio]tetrathiafulvalene; ATTA = [4'-(9-anthryl)-2,2':6',2''-
terpyridine-6,6''-diyl] bis(methylenenitrilo)tetrakis (acetic acid); MTTA = [4'-(10-methyl-9-anthryl)-2,2':6',2''-
terpyridine-6,6''-diyl]bis(methyl-enenitrilo)tetrakis(acetic acid); PATA = N,N,N',N'-[2,6-bis(3'-aminomethyl-1'-
pyrazolyl)-4-(9''-anthryl)pyridine]tetrakis(acetic acid); aeip = 2-(anthracen-9-yl)-1-ethyl-imidazo[4,5-
f][1,10]phenanthroline; An-bpy = 4-(anthracen-9-yl)-2,2'-bipyridine.
[b] pH =10.2. [c] pH = 7.2.
1
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A highly sensitive and selective visible-light excitable luminescence probes for singlet oxygen
based on a dinuclear ruthenium complex
Hong-Ju Yin, Yan-Ju Liu, Jie Gao, and Ke-Zhi Wang
A water-soluble dinuclear Ru(II) complex acts as visible-light excitable luminescence probes for
1
2
O with low detection limits of 2.7-3.2 nM and high selectivity over other reactive oxygen
species in both the neutral and basic media.