Exploiting the benefit of S0 → T1 excitation in triplet-triplet annihilation upconversion to attain large anti-stokes shifts: Tuning the triplet state lifetime of a tris(2,2′-bipyridine) osmium(ii) complex

Article abstract of DOI:10.1039/c7dt04803c

Os(ii) complexes are particularly interesting for triplet-triplet annihilation (TTA) upconversion, due to the strong direct S₀ → T₁ photoexcitation, as in this way, energy loss is minimized and large anti-Stokes shift can be achieved for TTA upconversion. However, Os(bpy)₃ has an intrinsic short T₁ state lifetime (56 ns), which is detrimental for the intermolecular triplet-triplet energy transfer (TTET), one of the crucial steps in TTA upconversion. In order to prolong the triplet state lifetime, we prepared an Os(ii) tris(bpy) complex with a Bodipy moiety attached, so that an extended T₁ state lifetime is achieved by excited state electronic configuration mixing or triplet state equilibrium between the coordination center-localized state (³MLCT state) and Bodipy ligand-localized state (³IL state). With steady-state and time-resolved transient absorption/emission spectroscopy, we proved that the ³MLCT is slightly above the ³IL state (by 0.05 eV), and the triplet state lifetime was prolonged by 31-fold (from 56 ns to 1.73 μs). The TTA upconversion quantum yield was increased by 4-fold as compared to that of the unsubstituted Os(ii) complex.

Full text of DOI:10.1039/c7dt04803c

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Efficient extraction of sulfate from water using
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a Zr-metal–organic
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DOI: 10.1039/C7DT04803C
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ARTICLE
Exploit the Benefit of S0T1 Excitation in Triplet-Triplet
Annihilation Upconversion to Attain Large Anti-Stokes Shifts:
Tuning the Triplet State Lifetime of a Tris(2,2’-Bipyridine)
Osmium(II) Complex
Received 00th January 2018,
Accepted 00th January 2018
DOI: 10.1039/x0xx00000x
Dongyi Liu, Yingjie Zhao, Zhijia Wang, Kejing Xu and Jianzhang Zhao*
www.rsc.org/
Os(II) complexes are particular interesting for triplet-triplet annihilation (TTA) upconversion, due to the strong direct S0T1
photoexcitation, as in this way, energy loss is minimized and large anti-Stokes shift can be achieved for TTA upconversion.
However, Os(bpy)3 has an intrinsic short T1 state lifetime (56 ns), which is detrimental for the intermolecular triplet-triplet
energy transfer (TTET), one of the crucial steps in TTA upconversion. In order to prolong the triplet state lifetime, we
prepared a Os(II) tris(bpy) complex with Bodipy moiety attached, so that an extended T1 state lifetime is resulted by excited
state electronic configuration mixing or triplet state equilibrium between the coordination center-localized state (3MLCT
state) and Bodipy ligand-localized state (3IL state). With steady-state and time-resolved transient absorption/emission
spectroscopies, we proved that the 3MLCT is slightly above the 3IL state (by 0.05 eV), and the triplet state lifetime was
prolonged by 31-fold (from 56 ns to 1.73 s). The TTA upconversion quantum yield was increased by 4-fold as compared to
that of the unsubstituted Os(II) complex.
diacetyl, and ketocoumarin, etc.25 Transition metal complexes
such as Pt(II),26,27 Ir(III),28,29 Ru(II) complexes were also used as
Introduction

triplet photosensitizers.30 33 However, these conventional
Recently triplet photosensitizers have attracted much
photosensitizers suffer from drawbacks such as difficulty to
prepare or purify, loss of ISC upon derivatization (although in
some cases careful functionalization may leave ISC intact) or
weak visible light absorption. Moreover, they share another

attention,1 4 due to the applications of these versatile materials
in photodynamic therapy,2 photocatalysis such as

photocatalytic hydrogen (H2) production,5 7 photoredox

catalytic synthetic organic reactions,8 13 and triplet-triplet
common feature, i.e., the photoexcitation promotes the S0S1

annihilation (TTA) upconversion, etc.14 23 TTA upconversion has
transition, then the ISC occurs and the triplet state (T1 state) of
the photosensitizer is populated, followed by TTET to the triplet
acceptor, and TTA, finally the upconverted fluorescence is
attracted much attention due to its advantages over other
upconversion methods, such as upconversion with two-photon
absorption dyes, or rare earth materials.24 TTA upconversion
requires a triplet photosensitizer for absorbing the excitation
energy and a triplet acceptor for the upconverted emission
(delayed fluorescence). The energy is transferred from the
photosensitizer to the acceptor molecules by intermolecular
triplet-triplet-energy-transfer (TTET) process; then the excited
singlet state of the acceptor will be produced and the

emitted.15 16,34 Due to the large electron exchange energy (J) for
these coplanar
-conjugated triplet photosensitizers, the
energy gap between the S1 state and the T1 state is large (ES1/T1
= 2J), thus the energy loss from S1 to T1 state is large.35
Concerning TTA upconversion, an intrinsic drawback exists with
S0S1 photoexcitation, i.e., the anti-Stokes shift of the
upconverted emission is reduced. Larger anti-Stokes shift is
desired for TTA up-conversion because photons with low
energy can be converted to photons with much higher energy,
for instance, red-to-blue can be resulted. However, TTA up-
conversion with large anti-Stokes shifts were rarely
reported.15,16,34,36

fluorescence from the acceptor can be observed.14 20
Conventional triplet photosensitizers are limited to porphyrin
derivatives (including Zn(II), Pt(II) or Pd(II) complexes),
halogenated xanthane dyes, such as Rose Bengal or Methylene
Blue, as well as some keto compounds, such as benzophenone,
One method to address this drawback is to directly promote
the S0

T1 transition by photoexcitation of the photosensitizer,
a State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian
University of Technology, E-208 West Campus, 2 Ling Gong Rd., Dalian 116024, P.
R. China.
E-mail: zhaojzh@dlut.edu.cn ORCID: orcid.org/0000-0002-5405-6398
† Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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a)
b)
c)
d)
e)
View Article Online
DOI: 10.1039/C7DT04803C
Br
1
Br
N
N
N
N
N
N
N
2
1
L1
h)
g)
f)
I
N
N
HN
N
F
N
N
F
N
N
N
B
O
Cl
B
B
F
F
F
F
L2
4
3
R
Cl
Cl
N
N
N
N
j)
i)
N
Os
N
N
Os
N
R
5
(NH4)2OsCl6
N
N
N
N
N
N
5
N
N
N
N
N
N
N
N
F
N
N
Os
N
Os
N
N
N
N
N
B
N
N
Os
N
F
N
Os(bpy)3
Os-ph
Os-BDP
O
O
N
O
I
I
N
F
N
F
B
N
O
B-1
PBI
Triplet Acceptor
Scheme 1. Synthesis of the Triplet Photosensitizers Os-BDP and the Reference Compounds Os(bpy)3 and Os-ph
.
a Key: (a) Tributyltin chloride, diethyl ether, n-
butyllithium,  °C to RT, N2, 2 h. (b) p-xylene, 2,5-dibrominatedbipyridine, Pd(PPh3)4, 120 °C , N2, 12 h. (c) NEt3, trimethylsilylacetylene, PdCl2(PPh3)2, PPh3, CuI,
reflux, N2, 8 h. (d) THF, tetrabutylammonium fluoride, RT, N2, 3 h. (e) THF/ NEt3, Pd(PPh3)4 , CuI, reflux, N2, 14 h. (f) Dry DCM,CF3COOH, RT, N2, 4.5 h; DDQ, NEt3,
BF3NEt3O, ice bath, RT, N2, overnight. (g) Dry DCM, NIS(1eq.), 0 °C , N2, 1.5 h. (h) THF/ NEt3, PdCl2(PPh3)2, PPh3, CuI, reflux, N2, 8 h. (i) Ethylene glycol, reflux, N2, 45
min. (j) Ethylene glycol, reflux, N2, 5h.
3
thus the anti-Stokes shift can be increased as compared to the the IL state (localized on Bodipy, 1.73
normal practice of S0 S1 excitation. Unfortunately, the properties of the Os(II) complexes were investigated by steady-
photoexcitation of S0 T1 is a strongly forbidden transition for state and time-resolved transient absorption/emission
most chromophores, as such the molar absorption coefficient ( spectroscopies. Such an Os(II) complex containing Bodipy shows
10 M cm ), which is clearly a much longer triplet excited state lifetime (1.73
s), and as a
drawback for TTA upconversion. Recently, Nobuo demonstr- result, the TTA upconversion efficiency was improved by 4-fold.
ated that the weakly allowed S0 T1 transition of Os(II) Our results are useful for the study of the photophysical
s). The photophysical




1
1
value) is extremely small (



complexes can be used to increase the anti-Stokes shift of TTA properties of Os(II) complexes containing organic chromo-
upconversion,37 the anti-Stokes shift was increased to 0.86 eV. phores for electronic configuration mixing, excited state
However, challenge is still present, i.e., the triplet state lifetime inversion, as well as for the development of new triplet
of the Os(II) complex in solution is very short (12 ns),37 which is photosensitizers for TTA upconversion.
detrimental to the TTET (an intermolecular process). A longer T1
state lifetime of the photosensitizer will improve the TTET
efficiency, thus the TTA upconversion efficiency can be
Results and Discussion
improved.
Design and Synthesis of the Compounds
Herein, we prepared a Os(II) complex with an attached
Bodipy chromophore (Scheme 1), to switch the shorter lived
3MLCT state of the reference Os(II) tris(bpy) complex (56 ns) to
The molecular structure design of the new Os(II) complex is
aimed at fully exploring the benefit of S0T1 transition for TTA
upconversion and to attain a triplet excited state with much
2 | Dalton Trans., 2018, 00, 1-9
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ARTICLE
0.8
0.6
0.4
0.2
0.0
longer lifetime. Our strategy is to attach a chromophore with
proper excited state energy levels to the Os(II) coordination
center, thus by transformation of the short-lived 3MLCT state of
View Artibcle Online
Os(bpy)3
Os-ph
Os-BDP
a
0.6
0.4
0.2
0.0
DOI: 10.1039/C7DT04803C
L1
L2
3
Os(II) complex to the ligand localized long-lived IL state, the

triplet state lifetime can be prolonged.38 43 We selected the
Bodipy as chromophore, which is a versatile chromophore for
its strong absorption of visible light, high quantum yield of
fluorescence (repressed non-radiative decay of the excited
300
400
500
600
300 400 500 600 700 800
Wavelength / nm

state), and the feasible derivatization chemistry.44 50
Wavelength / nm
Concerning our particular purpose with the Os(II)
coordination center for its strong photoexcitation induced
S0
T1 transition,33 the Bodipy chromophore is attractive for its
Fig. 1 UVVis absorption spectra of (a) L1 and L2, (b) Os(bpy)3, Os-ph and Os-BDP. c =
1.0  105 M in CH3CN, 25 °C.
proper T1 state energy level (1.67 eV), which matches with the
UVVis Absorption Spectra
T1 state energy level of the Os(II)(bpy)3 coordination center
The UV
Vis absorption spectra of the compounds were studied
(1.91 eV), thus triplet state inversion (3MLCT 3IL), or excited

(Fig. 1). For L1, a moderately intense absorption band at 314 nm
state configuration mixing can result, thus the excited state
lifetime will be extended.
(
= 23300 M cm ) was observed. For L2, absorption at 342

1
1

1

= 18900 M cm ) was observed, moreover, a strong
1
nm (
absorption band at 525 nm (
The synthesis of the complex Os-BDP is based on standard
methods (Scheme 1). An ethynyl moiety was introduced on the
bpy ligand, then Sonogashira coupling reaction with 2-iodo
Bodipy gives the ligand L2. Complexation with the Os(II)
precursor gives the complex Os-BDP with moderate yield
(Scheme 1). Reference Os-Ph containing no Bodipy unit was also

1
1

= 55400 M cm ) was also
observed, which was the feature absorption of the Bodipy
chromophore. For Os(bpy)3, a strong absorption band at 291

1
= 69800 M cm ), a moderate absorption band at 452
1
nm (
nm (
nm (



= 10900 M cm ) and a weak absorption band at 640

1
1
= 2800 M cm ) were observed (Fig. 1b); for Os-Ph
,

1
1
1
prepared (Scheme 1). All the complexes were verified with H
similar absorption bands were also observed (Fig. 1b), these
absorption bands were the feature absorptions of the Os(II)
coordination center, the weak and broad absorption band at
NMR, 13C NMR and HR MS analysis (refer to Supporting
Information).
500

700 nm is due to the S0

T1 transition. For Os-BDP, strong
1.0x106
8.0x105
6.0x105
4.0x105
4x105
3x105
2x105
4x105
c
a
b
N2
Air
N2
Air
N2
Air
3x105
2x105
1x105
0
1x105
0
2.0x105
0.0
500
600
700
800
500
600
700
800
500
600
700
800
Wavelength / nm
Wavelength / nm
Wavelength / nm
Fig. 2 Luminescence emission spectra of (a) Os(bpy)3, (b) Os-ph, (c) Os-BDP
;

ex = 460 nm, c = 1.0

105 M in CH3CN, 25
C.
4
3
2
1
0
2.0
1.5
1.0
0.5
0.0
2.0
a
c
RT
77K
b
RT
77K
1.5
1.0
0.5
0.0
RT
77K
700
750
800
850
700
750
800
850
650
700
750
800
850
Wavelength / nm
Wavelength / nm
Wavelength / nm
Fig. 3 Luminescence emission spectra of (a) Os(bpy)3, (b) Os-ph, (c) Os-BDP at RT compared with those at 77 K, ex = 635 nm, c = 1.0 
105 M in aerated EtOH/MeOH
mixed solvent (4:1, v/v), under N2.
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Table 1. Photophysical Properties of the Compounds
View Article Online
DOI: 10.1039/C7DT04803C
a
b
c
d
Complexes
abs

em
Δ
L (%)e
L (ns) f
[298 K]
54
L (s) f
[77 K]
0.869
T (ns) g
[N2]
56
T (ns) g
[Air]
46
(104 M1cm
6.98/1.09/0.28
6.75/1.0/0.3
)
(nm)
740
779
1
(nm)
Os(bpy)3
Os-ph
Os-BDP
291/452/640
291/435/636
290/525/650
0.85
0.31
0.64
1.19
0.53
0.39
46
0.797
23
21
6.48/4.95/0.25
515/565/778
53 (95%)
732(5%)
0.72
12.37(99.25%)
205.29(0.75%)
 h
1729
255
L1
L2
314
342/525
2.33
1.89/5.54
 h
 h
 h
 h
 h
 h
 h
 h
 h
565
3.8
 h
10 M, 25
C. Singlet oxygen quantum yields (
ex = 497 nm), Os-BDP ex = 545 nm), 25
C. e Luminescence quantum yields (
8-phenyl-4,4-difluoroboradiazaindacene as a standard ( ex = 400 nm, 25
L = 2.7% in CH3CN)60, in CH3CN, C. f Luminescence lifetimes in EtOH/MeOH (4:1,
C. Triplet state lifetimes of the complexes were measured by nanosecond transient absorption (collinear mode) in
ex = 472 nm, c = 5.0 ex = 442 nm, c = 1.0 ex = 502 nm, c = 2.5
106 M), Os-ph 105 M), Os-BDP 106 M), 20 C. h Not applicable.

C. Molar absorption coefficient at absorption maxima. Maxima emission
a
5
b
c
Maximum UV

Vis absorption wavelengths in CH3CN, c = 1.0

105 M, 25


) with Rose Bengal as a standard ( = 0.8 in MeOH), in
L) with 2,6-diiodo-1,3,5,7-tetramethyl-
d
wavelengths in CH3CN, ex = 460 nm, c = 1.0
CH3CN, Os(bpy)3 ex = 496 nm), Os-ph

(
(
(





5
g
v/v, c = 1.0
CH3CN, Os(bpy)3
 
10 M), under N2, 20
(

(

(



1
absorption at 290 nm (
at 650 nm (

= 64800 M1 cm ) and weak absorption solution (for instances, at 77 K). This blue-shiftted emission in

1
1

= 2500 M cm ) were observed, these two frozen matrix is due to the inability of the solvent shell to re-
absorption bands were the feature absorption of the Os moiety, adjust in the solid matrix, 3MLCT state is in charge transfer
meanwhile, a strong absorption band at 525 nm (
cm ) was observed, which is the feature absorption of the as a result, the emission is blue-shifted in the solid matrix.
Bodipy chromophore. The absorption spectrum of Os-BDP is For Os-BDP, interestingly, a narrower emission band was

= 49500 M
feature, as a result the 3MLCT state is less stabilized by solvation,
1

1
not the sum of L2 and Os(bpy)3 concerning the molar observed at 745 nm (Fig. 3c), at 77 K. This emission band is
3
absorption coefficients, although the absorption wavelengths assigned as the IL state localized on the Bodipy entity of the
are similar. It may be due to the -conjugation between the substituted bipy ligand. Previously similar phosphor-rescence
Os(II) coordination center and the Bodipy chromophore. The band of Bodipy ligand in transition metal complexes at low
UV-Vis absorption of the compounds in other solvents were also temperature was reported at 740 nm.52 Based on the result, we
3
studied (see ESI†, Fig. S11).
propose that in RT fluid solution, the MLCT state energy level
3
is higher than the IL state (

E

0.05 eV). This energy gap is
Luminescence Emission Spectra
significantly larger than the thermal energy at 77 K (0.007 eV),
thus there is no state mixing at 77 K for Os-BDP. In other words,
at 77 K, due to the decreased thermal energy, as well as the
higher energy of the 3MLCT (matrix effect), the 3IL state is
sufficiently lower than the 3MLCT state, as a result, the emission
The emission properties of the complexes were studied under
different atmospheres (Fig. 2). For Os(bpy)3 (Fig. 2a), a broad
emission band at 650850 nm (max = 740 nm) was observed.
The luminescence intensity of the structureless emission band
can be quenched by 25 % in air as compared to the aerated
solution. For Os-ph (Fig. 2b), a broad emission band at 650850
nm (max = 779 nm) was observed, the intensity of the
structureless emission band can be quenched by 11 % in air as
compared to the aerated solution. These results indicate that
the excited state lifetime is short, otherwise the quenching of
the phosphorescence will be more significant. For Os-BDP (Fig.
2c), the luminescence intensity of the structureless emission
E
1[MLCT]*
1[BDP]*
2.76 eV
ISC
2.37 eV
3[MLCT] (FC)
ISC
3[MLCT]
band at 650
in air as compared to the aerated solution, however, the
luminescence intensity of a weak emission band at 500 650 nm
850 nm ( max = 778 nm) can be quenched by 33%
3[BDP]*
1.67 eV
1.91 eV
1.72 eV
723 nm

450 nm
has no difference in air as compared to the deaerated solution.
The O2 sensitivity of the emission bands indicates that the
525 nm
650 nm
745 nm
emission of Os-BDP at 500
of Bodipy moiety, the emission band at 650

650 nm is due to the fluorescence
850 nm is the

S0
phosphorescence, based on the drastically different Stokes shift
and the luminescence lifetimes.
The luminescence spectra of the complexes at RT were
compared with those at 77 K (Fig. 3). For Os(bpy)3 and Os-ph
,
Scheme 2. Qualitative Jablonski Diagram for the Photophysical Process of the Os(II)
the emission bands are blue-shifted by 0.02 eV at 77 K as Complexes Exemplified with Os-BDP. Solid lines represent excitation or radiative
processes; dotted lines represent non-radiative processes. Note the 3MLCT
compared to those at RT. This result is reasonable since the
phosphorescence is quenched by the low-lying 3Bodipy* state. IC: internal conversion,
emissive triplet excited states of Os(bpy)3 and Os-ph are 3MLCT
ISC: intersystem crossing, FC: Franck-Condon.
states, which are known to show blue-shifted emission in frozen
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DOI: 10.1039/C7DT04803C
30
25
20
15
10
5
25
20
15
10
5
40
c
a
b
30
20
10
0
Excitation(N2)
Absorption
Excitation(N2)
Absorption
Excitation(N2)
Absorption
0
0
300 400 500 600 700 800
Wavelength / nm
300 400 500 600 700 800
Wavelength / nm
300 400 500 600 700 800
Wavelength / nm
Fig. 4 The normalized UV

Vis absorption and the excitation spectra of (a) Os(bpy)3, (b) Os-ph, (c) Os-BDP. The excitation spectra of Os(
em2 = 750 nm (Os-ph) and em3 = 765 nm (Os-BDP). c = 1.0 C.
105 M in CH3CN, 25
Ⅱ) complexes were recorded
with em1 = 745 nm (Os(bpy)3),





of Os-BDP at 77 K is due to 3IL state, which is different from that Os(bpy)3
of Os(bpy)3 and Os-Ph. According to these information, the 0.39%), and the luminescence quantum yields of Os-ph and Os-
(L = 1.19%), Os-ph (L = 0.53%) and Os-BDP (L =
photophysical processes of the Os(II) compl-exes exemplified BDP were decreased as compared to Os(bpy)3
.
with Os-BDP are shown in Scheme 2.
10000
Comparison of the luminescence excitation spectra and the
b
a
normalized UV
In order to study the intramolecular energy transfer in Os-BDP
the luminescence excitation spectra of the complexes were
Vis absorption spectra
1000
100
10
1000
100
10

L = 53 ns (95%)
L = 54 ns
,

L = 732 ns (5%)
recorded and compared with the normalized UV
spectra (Fig. 4).
Vis absorption
The normalized UVVis absorption spectroscopies and the
photo-luminescence excitation spectroscopies cannot be
completely overlapped in the higher energy region, given the
1
1
10000
1000
100
10
0
500 1000 1500 2000
0
2
4
6
8
10
 / ns

/ s
10000
spectra are normalized to the S0
T1 absorption band. This
c
d
1000
100
10
result indicates that the decay of the higher excited Sn state to
S1 state (or intersystem crossing to the emissive T1 state) has no
unitarian yield (there are most like more than one higher
excited states involved), and there are other non-radiative
decay channels. For Os-BDP (Fig. 4c), the emission wavelength
was set at 765 nm, we found that the absorption of the Bodipy
part at 525 nm is effective to produce the near IR emission at
765 nm. This result indicates efficient energy transfer from the
Bodipy moiety to the Os(II) coordination center, by a singlet
energy transfer, or a triplet energy transfer.53 The three
complexes show similar emission bands at similar wavelengths,
L = 12.37 s (99.25%)
L = 869 ns
L = 205.29 s (0.75%)
1
1
0
500
1000 1500
/ s
0
2
4

6
8
10
/ s

Fig. 5 Luminescence lifetimes decay trace of (a) Os(bpy)3 (em = 715 nm) and (b) Os-BDP
(em = 730 nm) at RT; (c) Os(bpy)3 (em = 705 nm) and (d) Os-BDP (em = 745 nm) at 77 K,
ex = 635 nm, c = 1.0  105 M in aerated EtOH/MeOH (4:1, v/v).

thus all the luminescence were assigned as the T1S0
Luminescence lifetimes at room temperature and 77 K
phosphorescence of the Os(II) coordination center. Previously
the phosphorescence of Bodipy was reported as a narrow,
structured emission band at 730 nm,51 although the
phosphorescence emission wavelength of Bodipy was close to
the phosphorescence of the Os(II) coordination center. The
luminescence of L2 and Os-BDP were compared for optically
The phosphorescence lifetimes of the complexes were
measured with the TCSPC (Fig. 5). Although the three complexes
give similar emission band, the phosphorescence lifetime of Os-
BDP (732 ns, the long-lived component of the biexponential
decay) is drastically different from that of Os(bpy)3 (54 ns) and
3
Os-ph (46 ns). This result indicates that the emissive MLCT
matched solutions (see ESI†, Fig. S3a). The fluorescence of L2 is
state of Os-BDP is significantly perturbed by another state, or
electronic configuration mixing, most pro-bably by the 3IL state
localized on the Bodipy ligand. The comparison of the
phosphorescence of Os-BDP at room temperature and 77 K
indicates that the 3MLCT state lies above
drastically quenched in Os-BDP, most likely by the heavy atom
effect of Os, i.e. ISC effect. It was also found that the
phosphorescence of Os-ph and Os-BDP were decreased as
compared to Os(bpy)3 (see ESI†, Fig. S13b). The luminescence
quantum yields of the complexes were also studied (Table 1),
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DOI: 10.1039/C7DT04803C
0.01
0.00
0.005
0.000
c
a
0.04
b
0 ns
......
-0.01
-0.02
-0.03
-0.04
0.02
0.00
126.8 ns
-0.005
-0.010
-0.015
s


...

380 ns
......
0 ns
s
-0.02
400 450 500 550 600
Wavelength / nm
400 450 500 550 600 650
Wavelength / nm
400
500
600
Wavelength / nm
0.04
0.03
0.02
0.01
0.00
0.05
0.00
0.03
e
f
d


T = 21 ns (Air)
T = 23 ns (N2)
0.00
-0.03
-0.06
-0.05
-0.10
-0.15

T = 255 ns (Air)
T = 1730 ns (N2)


T = 46 ns (Air)
T = 56 ns (N2)




-0.01
800 1000 1200 1400
/ ns
750 800 850 900 950 1000
/ ns
4
6
8 10 12 14 16 18
/ s



Fig. 6 Transient absorption spectra of (a) Os(bpy)3, ex = 480 nm, c = 3.0  105 M; (b) Os-ph, ex = 480 nm, c = 5.0  105 M; (c) Os-BDP, ex = 502 nm, c = 2.5  106 M in aerated and
deaerated CH3CN. Triplet lifetime decay trace of (d) Os(bpy)3, ex = 472 nm, c = 5.0  106 M; (e) Os-ph, ex = 442 nm, c = 1.0  105 M; (f) Os-BDP, ex = 502 nm, c = 2.5  106 M in
CH3CN, 25 C.
the 3IL state by only 0.05 eV (Fig. 3 and Scheme 2). The donor absorbance, Δ values of 85%, 31% and 64% were
luminescence lifetimes of the complexes at 77 K were also observed for Os(bpy)3
determined (Fig. 5). The lifetimes of Os(bpy)3 and Os-ph were respectively (Table 1).
extended by ca. 17-fold by decreasing the temperature from RT
, Os-ph and Os-BDP in CH3CN,
to 77 K, indicating the emissive triplet states are similar for both Nanosecond Transient Absorption Spectroscopy
complexes. For Os-BDP (Fig. 5b and Fig. 5d), however, the
In order to investigate the triplet excited state of the complex-
phosphorescence lifetimes increased by ca. 233-fold/280-fold
by decreasing the temperature, which extended from 0.05
es, the nanosecond transient absorption (ns TA) spectroscopi-
es of Os(bpy)3 Os-Ph and Os-BDP are studied(Fig. 6), and trip-
,
s/0.732
s (RT) to 12.37
s/205.29 s (77 K). It should be noted
let lifetimes were presented in Table 1.
that the 12.73
s is the slow limit because it is the instrument
Upon 472 nm pulsed laser photoexcitation, a weak bleaching
band at 460 nm was observed for Os(bpy)3 (Fig. 6a). The lifetime
of Os(bpy)3 was very short, it was determined as 56 ns (under
N2 atmosphere), and a weak positive absorption band at 430 nm
was observed for Os-ph (Fig. 6b), the lifetime of Os-ph was also
very short, it was determined as 23 ns (in N2 saturated solution).
Upon 502 nm pulsed laser photoexcitation, a bleaching band
at 503 nm was observed for Os-BDP (Fig. 6c). This band overlaps
response function (IRF). This result indicates that the property
of the emissive triplet state changed significantly by changing
the temperature and it is in agreement with the postulates that
the emissive state of Os-BDP at RT is 3MLCT, but inversion of the
3
triplet state energy levels (3MLCT vs. IL states) occurs at 77 K,
and it is the 3IL state at 77 K. Long-lived triplet excited state of
Bodipy were observed with Ir(III) complexes at 77 K (4.5 ms),51,54
as well as Ru(II) complexes (339 ms).52 The significantly shorter
triplet state lifetime in Os-BDP as compared to that of the Ir(III)
and Ru(II) complexes may be due the more significant heavy
with the transient absorption band in the range of 450 nm
nm. The excited state absorption (ESA) profile is the typical
T1 Tn absorption of the Bodipy triplet excited state. Thus, the
555


atom effect of Os atoms than Ir and Ru atoms.33,55 57 The
detected triplet excited state of Os-BDP is localized on the
Bodipy ligand. However, the triplet state localization on the
Os(II) coordination center cannot be excluded. The lifetime of
Os-BDP was determined as 1.73 s (N2, excited at 502 nm),
which is much longer than Os(bpy)3 (56 ns).
Interestingly, we found that the triplet state lifetime is not
excitation wavelength-dependent (see ESI † , Fig. S19). For
instance, selective excitation either into the Bodipy moiety
biexponential character of the decay curves of Os-BDP were
observed at RT and 77 K, but the exact reason for these
biexponential decay is unclear.
To verify the efficiency of the triplet state yields of the triplet
photosensitizers Os(bpy)3
,
Os-ph and Os-BDP, the singlet
Δ) of the triplet photosensitizers
oxygen (1O2) quantum yields (

were studied. With selective photoexcitation at the energy
6 | Dalton Trans., 2018, 00, 1-9
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(excited at 502 nm) or the Os(II) coordination center (excited at studied (Fig. 8). The KSV value of Os-BDP is ca. 5-fold for Os(bpy)3
,
View Article Online
DOI: 10.1039/C7DT04803C
650 nm), gives very similar triplet state lifetimes of 1.73
1.21 s (see ESI†, Fig. S19), respectively. This result indicates a
fast intra-molecular energy transfer.
Based on the lifetimes, we estimated the equilibrium
constant of the 3MLCT/3IL state in Os-BDP 58
s vs ca. 3.5-fold for Os-ph (Table 2).

300
200
100
0
300
200
100
0
.
Os(bpy)3
Os-ph
Os-BDP
Os(bpy)3
Os-ph
Os-BDP
b
a
1
1
1


（1 - ）
(1)
(2)

BDP
MLCT

1 -
kf

keq


kb
500
600
700
800
500
600
700
800
Wavelength / nm
Wavelength / nm

corresponds to the fractions of the excited BDP-like triplets,

Fig. 7 Upconversion with Os(bpy)3, Os-ph and Os-BDP as triplet photosensitizers and PBI
as triplet acceptor, excited by a 635 nm laser (continuous wave, 300 mW cm2). (a)
Emission of the complexes alone with a 635 nm laser excitation. (b) Upconversion
emission of the mixtures of the photosensitizers and PBI upon selective excitation of
photosensitizers with a 635 nm laser. c[Photosensitizers] = 1.0  104 M and c[PBI] = 2.5
 103 M. In deaerated DCM, 25 °C.
is the lifetime decay of metal complexes, where MLCT and BDP

correspond to the time constants for the decays of the excited
Os(II)(bpy)3 coordination center and BDP ligand. keq is the
equilibrium constant and kf is the forward energy transfer and
kb is the backward energy transfer rate constant. For the system
at room temperature, we approximate the BDP as 100
s and

MLCT as 60 ns, then based on eq. (1) and (2), was calculated as

0.96, the keq = 24. This result means that the equilibrium
population is predominantly (96%) in favor of the BDP
chromophore (3IL state), not the Os(II) coordination center
(3MLCT state). Similarly, we estimated the equilibrium at 77 K
with eq. (1) and (2), with approximation of BDP =10 ms (77 K)
and MLCT = 800 ns (77 K). The keq was calculated as 250. Thus at
77 K, the triplet state is basically a 3IL state. This conclusion is in
agreement with the spectroscopic studies, for instance the
observation of the BDP-localized signal in the nanosecond
transient absorption spectroscopy. However, the 3MLCT lies
only slightly higher than 3IL state (by 0.05 eV), thus the decay of
3
the IL state is fast via the drain channel, i.e., the short-lived
Fig. 8 Stern-Volmer plots generated from luminescence lifetime (L) quenching of
Os(bpy)3, Os-ph and Os-BDP measured as a function of the concentration of quencher
(PBI). Luminescence lifetimes (L) were measured by excitation at ex = 635 nm,
c[photosensitizers] = 1.0  104 M in deaerated dichloromethane, 20 °C.
3MLCT state of the Os(II) coordination center.
Triplet-Triplet Annihilation Upconversion
Since we extended the triplet state lifetimes of the Os(II)
complexes, the complexes described herein were used as triplet
photosensitizers for another triplet-triplet energy transfer
(TTET) process, i.e., TTA upconversion (Fig. 7). A 635 nm cw-
laser was used as excitation source. Based on the T1 state
energy levels, we used PBI as triplet acceptor/emitter (ET1 = 1.2
eV, Scheme 1). For the photo-sensitizers alone, no emission in
the range of 550 nm was observed (Fig. 7a). In the presence of
Os-BDP, however, significant upconverted emission at 550 nm
was observed (Fig. 7b), which is much stronger than that of
Os(bpy)3 or Os-Ph. The upconversion quantum yield with Os-
BDP (1.2%) is much higher than that of the Os(bpy)3 (0.3%) or
Os-ph (0.17%). It should be noted that the triplet state lifetimes
of the three Os(II) complexes play a major role for the variation
of the upconversion quantum yields. In order to study the TTET
efficiency of TTA upconversion, quenching the luminescence
lifetime of the Os() complexes by triplet acceptor PBI was
Table 2. Upconversion-Related Parameters of the Os(II) Complexes
Sensitizers
UC
(%) a
0.30
0.17
1.20
Ksv
)
303.7
411.1
14568.0
τL
kq
(109M1 s
3.43
(M
(ns) c
88.5
)
1
b
1 d
Os(bpy)3
Os-ph
Os-BDP
71.6
1301.7
5.74
11.2
a Upconversion quantum yields were measured with B-1 as the standard (F = 0.101 in
DCM), ex = 635 nm, c[Photosensitizers] = 1.0  10 M and c[PBI] = 2.5  10 M. In

4
3
b
aerated DCM, 20 °C. Stern-Volmer quenching constants (Ksv) for the luminescence
lifetime of Os() complexes, quenched by PBI. c Luminescence lifetimes of Os(bpy)3, Os-
10
M
in aerated
4
ph and Os-BDP, ex
dichloromethane, 20 °C. Bimolecular quenching constants (kq), Ksv = kqτ0, τ0 is the
=
635 nm, c[photosensitizers]= 1.0

d
luminescence lifetime of photosensitizers without quencher.
Conclusions
In summary, in order to fully exploit the benefit of direct S0T1
photoexcitation of the Os(bpy)3 complex (bpy = 2,2’-bipyridine)
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to reduce the energy loss for the S1

T1 intersystem crossing of 100:10:1, v/v/v). The solvent was removed under reduced
View Article Online
DOI: 10.1039/C7DT04803C
the normal triplet photosensitizers, the intrinsic short T1 state pressure, a small amount of CH3CN:H2O = 1:1 (v/v) mixture was
lifetime (56 ns) of Os(bpy)3 has to be prolonged, otherwise the added to dissolve the solid completely, then saturated NH4PF6
intermolecular triplet-triplet-energy-transfer efficiency is low. solution was added dropwise. The suspension was filtered to
To this end, a Bodipy moiety was attached to the bpy ligand of remove insoluble inorganic salts and the solid was washed with
the Os(bpy)3 coordination framework, to establish an excited water. A dark-green solid (50 mg, 47.6%) was afforded. 1H NMR
states equilibrium to extend the triplet lifetimes. With steady- (400 MHz, CD3CN) δ 8.58–8.44 (m, 6H), 7.99–7.81 (m, 6H), 7.75
state and time-resolved transient absorption spectroscopies, (d, J = 5.8 Hz, 1H), 7.64 (dd, J = 17.1, 8.3 Hz, 5H), 7.47 (ddd, J =
we proved the energy transfer from Bodipy moiety to the Os(II) 22.9, 16.2, 7.7 Hz, 4H), 7.38–7.26 (m, 6H). 13C NMR (126 MHz,
coordination center. Based on the phosphorescence emission CD3CN) δ 164.27, 164.15, 163.76, 163.69, 157.82, 157.64,
wavelength at room temperature and 77 K, we propose the 156.63, 156.41, 156.36, 156.15, 156.08, 155.87, 144.30, 143.17,
3MLCT state lies slightly higher than the Bodipy localized 3IL 142.58, 141.29, 139.96, 137.11, 136.92, 135.34, 134.17, 133.38,
state by 0.05 eV. With this molecular structure design and thus 132.32, 130.67, 130.38, 129.90, 129.74, 129.48, 129.25, 127.53,
the T1 state lifetime was extended from the 56 ns of the un- 126.54, 122.64, 114.19, 101.80, 88.93, 70.01, 69.98, 48.03, 6.11,
substituted Os(II) complex to 1.73 s. With the Os(II) complex 5.95, 5.78, 5.62, 5.45, 5.37, 5.29, 5.21, 5.12. ESI-HRMS:
containing Bodipy moiety, triplet-triplet annihilation quantum [(M
yield was increased to 1.2 %, as compared to 0.3 % of the [(M
reference Os(II) complex. The anti-Stokes shift is 0.55 eV. Our


2PF6)2+] cal., m/z =380.0995, found, m/z = 380.0999;
PF6)+] cal., m/z = 905.1632, found, m/z = 905.1653.
Synthesis of Os-BDP. Under N2, L2 (21 mg, 0.042 mmol) and 5 (26
results are useful for exploitation the novel S0T1
mg, 0.045 mmol) were added to ethylene glycol (5 mL), bu-
bbled with N2 for 20 min and refluxed for 4 h. The mixture was
cooled to room temperature. The crude product was purified
with column chromatography (CH3CN:H2O:KNO3 (saturated w-
ater solution) = 100:10:1, v/v/v). The solvent was removed
under reduced pressure, a small amount of CH3CN:H2O = 1:1
(v/v) mixture was added to dissolve the solid completely, then,
saturated NH4PF6 solution was added drop-wise. The suspen-
sion was filtered to remove insoluble inorganic salts and the
solid was washed with water. A dark-red solid (15 mg, 27.6%)
photoexcitation, as well as for achieving large anti-Stokes shift
for TTA upconversion.
Experimental Section
Analytical Measurements
All the chemicals used in synthesis are analytically pure and
were used as received. Solvents were dried and distilled before
used for synthesis. The synthesis of compounds 1-5 and L2 were
reported elsewhere.52,59
1
was afforded. H NMR (500 MHz, CD3CN) δ 8.54–8.40 (m, 6H),
7.94–7.80 (m, 6H), 7.73 (d, J = 5.3 Hz, 1H), 7.68–7.54 (m, 8H),
7.39–7.28 (m, 7H), 6.26 (s, 1H), 2.56 (s, 3H), 2.52 (s, 3H), 1.45 (d,
J = 3.7 Hz, 3H), 1.39 (s, 3H). 13C NMR (126 MHz, CD3CN) δ 158.59,
158.54, 158.50, 158.16, 157.21, 151.51, 150.88, 150.75, 150.62,
150.58, 150.46, 137.31, 137.00, 136.96, 136.93, 136.87, 136.82,
133.64, 129.15, 129.09, 127.79, 127.74, 127.70, 127.66, 127.57,
124.55, 124.38, 124.33, 124.19, 124.16, 123.70, 123.02, 116.99,
90.27, 90.22, 54.01, 26.35, 26.31, 13.81, 13.59, 12.26, 11.92.
Synthesis of Os(bpy)3. Under N2, 2,2’-bipyridine (8.0 mg, 0.05
mmol) and
5 (29 mg, 0.05 mmol) were added to ethylene gly-
col (8 mL), bubbled with N2 for 20 min and refluxed for 5 h. The
mixture was cooled to room temperature, the solvent was
removed under reduced pressure. Then saturated NH4PF6
solution was added dropwise, and the suspension was stirred
for 15 min and then filtered to remove insoluble inorganic salts.
The solution was evaporated to dryness under reduced
pressure to obtain a dark-green solid. The crude product was
further purified by column chromatography (aluminium oxide,
DCM:MeOH, 100:0 to 90:10, v/v) to afford a dark-green solid
(28.0 mg, 58.3%). 1H NMR (500 MHz, d6-DMSO) δ 8.83 (d, J = 8.2
Hz, 1H),7.97 (dd, J = 11.6, 4.2 Hz, 1H), 7.66 (t, J = 13.4 Hz, 1H),
7.43 (t, J = 6.3 Hz, 1H). 13C NMR (126 MHz, CD3CN) δ 211.79,
164.26, 156.24, 156.04, 143.23, 142.46, 133.42, 133.28, 129.87,
129.71, 122.61, 73.08, 43.98, 35.49, 35.20, 34.01, 28.90, 27.99,
18.64, 15.66, 6.11, 5.94, 5.78, 5.61, 5.53, 5.45, 5.37, 5.28, 5.21,
ESI-HRMS: [(M

2PF6)2+] cal., m/z = 503.1565, found, m/z

PF6)+] cal., m/z = 1151.2772, found, m/z =
=503.1566; [(M
1151.2786.
Acknowledgements
We thank the NSFC (21473020, 21673031, 21273028, 21421005,
21761142005 and 21603021), the Fundamental Research Funds
for the Central Universities (DUT16TD25, DUT15ZD224,
DUT2016TB12) for financial support.
5.12. ESI-HRMS: [(M

2PF6)2+] cal., m/z = 330.0839, found, m/z

PF6)+] cal., m/z = 805.1319, found, m/z =
= 330.0859; [(M
805.1323.
References
1
2
3
Samuel G. Awuahab and Y. You, RSC Adv., 2012,
11169 11183.
A. Kamkaew, S. H. Lim, H. B. Lee, L. V. Kiew, L. Y. Chung and K.
Burgess, Chem. Soc. Rev., 2013, 42, 77 88.
J. Zhao, K. Xu, W. Yang, Z. Wang and F. Zhong, Chem. Soc. Rev.,
2015, 44, 8904 8939.
2,
Synthesis of Os-ph. Under N2, L1 (26 mg, 0.1 mmol) and 5 (57 mg,

0.1 mmol) were added to ethylene glycol (10 mL), bubbled with
N2 for 20 min and refluxed for 7 h. The mixture was cooled to
room temperature. The crude product was purified with column
chromatography (CH3CN:H2O:KNO3 (saturated water solution) =


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4
5
6
7
8
9
J. Zhao, W. Wu, J. Sun and S. Guo, Chem. Soc. Rev., 2013, 42
5323 5351.
F. Wang, W.-G. Wang, X.-J. Wang, H.-Y. Wang, Ch.-H. Tung, L.-
Z. Wu, Angew. Chem. Int. Ed., 2011, 50, 3193 3197.
F. Gärtner, S. Denurra, S. Losse, A. Neubauer, A. Boddien, A.
Gopinathan, et al, Chem. Eur. J., 2012, 18, 3220 3225.
J. I. Goldsmith, W. R. Hudson, M. S. Lowry, T. H. Anderson, and
S. Bernhard, J. Am. Chem. Soc., 2005, 127, 7502 7510.
D. P. Hari and B. K nig, Angew. Chem. Int. Ed., 2013, 52, 4734
4743.
,
39 G. Ragazzon, P. Verwilst, Sergey A. Denisov, A. Credi, G.

Jonusauskasc and Nathan D. McClenaghan, CheVmie.wCAortimclemOunlnin.e,
DOI: 10.1039/C7DT04803C
2013, 49, 91109112.

40 A. Harriman, M. Hissler, A. Khatyr and R. Ziessel, Chem.
Commun., 1999, 735 736.
41 D. S. Tyson, J. Bialecki and F. N. Castellano, Chem. Commun.,
2000, 2355 2356.
42 N. D. McClenaghan, Y. Leydet, B. Maubert, M. T. Indelli, S.
Campagna, Coord. Chem. Rev., 2005, 249 1336 1350.
43 Y. Feng, J. Cheng, L. Zhou, X. Zhou and H. Xiang, Analyst, 2012,
137, 4885 4901.
44 R. Ziessel and A. Harrimanb, Chem. Commun., 2011, 47
611 631.
45 G. Ulrich, R. Ziessel, and A .Harriman, Angew. Chem. Int. Ed.,
2008, 47, 1184 1201.
46 D. Frath, J. Massue, G. Ulrich, and R. Ziessel, Angew. Chem. Int.
Ed., 2014, 53, 2290 2310.
47 A. Loudet and K. Burgess, Chem. Rev., 2007, 107, 4891
14 Tanya N. Singh-Rachford, Felix N. Castellano, Coord. Chem. 48 Shuichi Suzuki, Masatoshi Kozaki, Koichi Nozaki, Keiji Okada
Rev., 2010, 254, 2560 2573. 49 S. Suzuki, M. Kozaki, K. Nozaki, K. Okada, J. Photochem.
15 P. Ceroni, Chem. Eur. J., 2011, 17, 9560 Photobio. C: Photochem. Rev., 2011, 12, 269 292.
16 J. Zhao, S. Ji and H. Guo, RSC Adv., 2011, 50 H. Lu, J. Mack, Y. Yang and Z. Shen,Chem. Soc. Rev., 2014, 43
17 A. Monguzzi, R. Tubino, S. Hoseinkhani, M. Campioneb and F. 4778 4823.
Meinardi, Phys. Chem. Chem. Phys., 2012, 14, 4322 4332. 51 S. G. Awuahab and Y. You, RSC Adv., 2012,
18 Y. C. Simon and C. Weder , J. Mater. Chem., 2012, 22 52 A. A. Rachford, R. Ziessel, T. Bura, P. Retailleau, and Felix N.
20817 20830. Castellano, Inorg. Chem., 2010, 49, 3730 3736.
19 C. Ye, L. Zhou, X. Wang and Z. Liang, Phys. Chem. Chem. Phys., 53 W. Wu, J. Sun, X. Cui and J. Zhao, J. Mater. Chem. C, 2013,
2016, 18, 10818 10835. 4577 4589.
20 J. Zhou, Q. Liu, W. Feng, Y. Sun, and F. Li, Chem. Rev. 2015, 54 Z. Kostereli, T. Ozdemir, O. Buyukcakir, and Engin U. Akkaya,
115, 395 465. Org. Lett., 2012, 14, 3636 3639.
21 Z. Xun, Y. Zeng, J. Chen, T. Yu, X. Zhang, G. Yang, and Y. Li, 55 J. Sun, F. Zhong, X. Yi, and J. Zhao, Inorg. Chem., 2013, 52
Chem. Eur. J., 2016, 22,8654 8662. 6299 6310.
22 P. Duan, N. Yanai , H. Nagatomi, and N. Kimizuka, J. Am. Chem. 56 S. Amemori, Y. Sasaki, N. Yanai, and N. Kimizuka, J. Am. Chem.
Soc., 2015, 137, 1887 1894. Soc., 2016, 138, 8702 8705.
23 P. Duan, N. Yanai, Y. Kurashiga, and N. Kimizuka, Angew. Chem. 57 S. Diring, B. Ventura, A. Barbieri and R. Ziessel, Dalton Trans.,





ö


J. Xuan and W-J Xiao, Angew. Chem. Int. Ed., 2012, 51, 6828


6838.
,
10 L. Shi and W-J Xia, Chem. Soc. Rev., 2012, 41, 7687

7697.

11 D. Ravelli, M. Fagnoni and A. Albini, Chem. Soc. Rev., 2013, 42
97 113.
12 S. Fukuzumi and K. Ohkuboa, Chem. Sci., 2013,
13 C. K. Prier, D. A. Rankic, and D. W. C. MacMillan,Chem. Rev.,
2013, 113 (7), 5322 5363.
,


4
, 561574.


4932.


9564.
, 937

1

950.
,


2, 1116911183.
,


1
,




,





Int. Ed., 2015, 54, 7544
24 M. Haase and H. Schäfer, Angew. Chem. Int. Ed., 2011, 50
5808 5829.
25 J. Zhao, W. Wu, J. Sun and S. Guo, Chem. Soc. Rev., 2013, 42
5323 5351.
26 F. N. Castellano, I. E. Pomestchenko, E. Shikhova, F. Hua,
Maria L. Muro, N. Rajapakse, Coord. Chem. Re., 2006, 250
1819 1828.
27 J. A. Gareth Williams, Top. Curr. Chem., 2007, 281: 205
28 Y. You and W. Nam, Chem. Soc. Rev., 2012, 41, 7061 7084.
29 L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura, F. Barigelletti,
Top. Curr. Chem., 2007, 281: 143 203.
30 S. Campagna, F. Puntoriero, F. Nastasi, G. Bergamini, and
V. Balzani, Top. Curr. Chem., 2007, 280: 117 214.
31 V. Fernández-Moreira, Flora L. Thorp-Greenwood and
Michael P. Coogan, Chem. Commun., 2010, 46, 186 202.
32 Y. Feng, J. Cheng, L. Zhou, X. Zhou and H. Xiang, Analyst, 2012,
137, 4885 4901.
33 Y. Chi and P.-T. Chou, Chem. Soc. Rev., 2007, 36, 1421
34 T. N. Singh-Rachford, F. N. Castellano, Coord. Chem. Rev.,
2010, 254, 2560 2573.

7549.
2012, 41, 1309013096.
,
,
58 S. A. Denisov, Y. Cudré, P. Verwilst, G. Jonusauskas, M. Marín-

Suareź, J. F. Fernandez-Sáncheź, E. Baranoff, and N. D.
McClenagha, Inorg. Chem., 2014, 53, 26772682.

59 E. M. Kober, J. V. Caspar, B. P. Sullivan, and T. J. Meyer, Inorg.
Chem., 1988, 27, 4587
60 J. Sun, F. Zhong, X. Yi, and J. Zhao, Inorg. Chem., 2013, 52
6299 631.
4598.
,
,



268.






1431.

35 N. J. Turro, V. Ramamurthy, J. C. Scaiano, Principles of
Molecular Photochemistry: An Introduction; University
Science Books: Sausalito, CA, 2009.
36 T. N. Singh-Rachford, A. Nayak, M. L. Muro-Small, S. Goeb, M.
J. Therien, and F. N. Castellano, J. Am. Chem. Soc., 2010, 132
,
14203

14211.
37 S. Amemori, Y. Sasaki, N. Yanai, and N. Kimizuka, J. Am. Chem.
Soc., 2016, 138, 8702

8705.
38 M. T. Indelli, M. Ghirotti, A. Prodi, C. Chiorboli, F. Scandola, N.
D. McClenaghan, F. Puntoriero, and S. Campagna, Inorg.
Chem., 2003, 42, 54895497.
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DOI: 10.1039/C7DT04803C
Table of Contents Entry
Exploit the Benefit of S0→T1 Excitation in Triplet-Triplet Annihilation Upconversion
to Attain Large Anti-Stokes Shifts: Tuning the Triplet State Lifetime of a Tris(2,2’-
Bipyridine) Osmium(II) Complex
Dongyi Liu, Yingjie Zhao, Zhijia Wang, Kejing Xu and Jianzhang Zhao*
The triplet state lifetime of Os(bpy)3 complex showing strong S0→T1 absorption was prolonged 30-fold
by attachment of Bodipy Chromophore.
1