BODIPY triads triplet photosensitizers enhanced with intramolecular resonance energy transfer (RET): Broadband visible light absorption and application in photooxidation

Article abstract of DOI:10.1039/c3sc52323c

Resonance energy transfer (RET) was used to enhance the light absorption in triad triplet photosensitizers to access strong and broadband absorption in visible region (from 450-750 nm). This strategy was demonstrated by preparation of (BODIPY)₂-diiodo-aza-BODIPY triad (B-2) and (carbazole-styryl BODIPY)₂-diiodo-aza-BODIPY triad (B-3), in which the energy donor (BODIPY or styryl-BODIPY) and the energy acceptor (aza-BODIPY, also as the spin converter) parts were connected by click chemistry. Both the energy donors and the energy acceptors show strong absorption in the visible spectral region, but at different wavelengths, therefore the triads show broadband absorption in visible spectra region, e.g. the two major absorption bands of B-3 are located at 593 nm and 683 nm, with ε up to 220 000 M^-1 cm^-1 and 81 000 M^-1 cm^-1, respectively. For comparison, a reference compound with only diiodo-aza-BODIPY as the light-harvesting unit was prepared (B-1), which shows only one major absorption band in visible spectral region. Fluorescence studies indicated intramolecular energy transfer for these BODIPY hybrids, a conclusion which is supported by the femtosecond time-resolved transient absorption spectroscopy. Nanosecond transient absorption spectra show that triplet excited states of the dyad and the triad are localized on the iodo-aza-BODIPY part. The compounds were used as triplet photosensitizers for singlet oxygen (¹O₂) mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability of the new triplet photosensitizers are more efficient than the mono-chromophore based triplet photosensitizers. The molecular design rationale of these RET-enhanced multi-chromophore triplet photosensitizer is useful for development of efficient triplet photosensitizers and for their applications in photocatalysis, photodynamic therapy, photovoltaics and upconversion.

Full text of DOI:10.1039/c3sc52323c

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EDGE ARTICLE
Bodipy triads triplet photosensitizers enhanced with intramolecular
resonance energy transfer (RET): broadband visible light absorption
and application in photooxidation
Song Guo,a Lihua Ma,a Jianzhang Zhao,a* Betül Küçüköz,b Ahmet Karatay,b Mustafa Hayvali,c* H. Gul
5
Yaglioglub and Ayhan Elmalib
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Resonance energy transfer (RET) was used to enhance the light absorption in triad triplet photosensitizers
to access strong and broadband absorption in visible region (from 450 nm – 750 nm). This strategy was
10 demonstrated by preparation of (Bodipy)2-diiodo-Aza-Bodipy triad (B-2) and (carbazole-styryl Bodipy)2-
diiodo-Aza-Bodipy triad (B-3), in which the energy donor (Bodipy or styryl-Bodipy) and the energy
acceptor (aza-Bodipy, also as the spin converter) parts were connected by Click chemistry. Both the
energy donors and the energy acceptors show strong absorption in the visible spectral region, but at
different wavelength, therefore the triads show broadband absorption in visible spectra region, e.g. the
15 two major absorption bands of B-3 are located at 593 nm and 683 nm, with ε up to 220 000 M-1 cm-1 and
81 000 M-1 cm-1, respectively. For comparison, a reference compound with only diiodo-Aza-Bodipy as
the light-harvesting unit was prepared (B-1), which shows only one major absorption band in visible
spectral region. Fluorescence studies indicated intramolecular energy transfer for these Bodipy hybrids, a
conclusion which is supported by the femtosecond time-resolved transient absorption. Nanosecond
20 transient absorption spectra show that triplet excited states of the dyad and the triad are localized on the
iodo-aza-Bodipy part. The compounds were used as triplet photosensitizers for singlet oxygen (1O2)
mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability of the new triplet
photosensitizers are more efficient than the mono-chromophore based triplet photosensitizers. The
molecular design rationale of these RET-enhanced multi-chromophore triplet photosensitizer is useful for
25 development of efficient triplet photosensitizers and for their applications in photocatalysis,
photodynamic therapy, photovoltaics and upconversion.
panchromic photoexcitation, the application of these molecular
1. Introduction
50 arrays as triplet photosensitizer was not studied.23-26
Triplet photosensitizers have attracted much attention owing to
the applications in photodynamic therapy (PDT),1-7
30 photocatalysis,8-11 photovoltaics,12 and more recently the triplet-
Energy donor and energy acceptor were widely used to
construct fluorescence resonance energy transfer (FRET, more
precisely, RET), or the through-bond energy transfer (TBET)
molecular assembles.27-36 However, this strategy was never used
55 for preparation of triplet photosensitizers. Recently Bodipy-Aza-
Bodipy dyads and triads were reported,31,35,37 and the
intramolecular RET energy transfer and electron transfer were
studied. However, without iodination, these Bodipy arrays do not
produce any triplet excited state.35 Iodo-aza-Bodipy compounds
60 were reported as triplet photosensitizers.3 No auxiliary visible
light-absorbing chromophores were attached to the diiodo aza-
Bodipy part, thus the molecular structures can be categorized to
the conventional mono-chromophore based triplet photosensitizer.
Recently we prepared Bodipy-iodo-Bodipy dyads based on the
65 RET effect, but the narrow absorption band is still limited to
green region.36d Therefore, much room is left to fully explore the
RET-based new molecular design strategy to acess broadband
absorbing triplet photosensitizers.
triplet
annihilation
upconversion.13-18
Typical
triplet
photosensitizers include transition metal complexes,19 porphyrins,
iodo- or bromo-chromophores, such as iodo-Bodipy, or C60-
organic chromophore compounds.6,715,16 The common feature of
35 these conventional triplet photosensitizers is that the molecular
structure is based on uni-chromophore profile.6,7,20-22 As a result,
usually there is only one major absorption band in the visible
spectral region for these triplet phtoosensitizers. This character is
detrimental for application of the triplet photosensitizers,
40 especially when a broadband excitation light source was used,
such as solar light.13 Therefore, triplet photosensitizer with
broadband absorption in visible spectral region, or panchromatic
absorption, is highly desired. However, no such triplet
photosensitizers have been reported.1-7 For example, the seminal
45 works on iodo-Bodipy triplet photosensitizers demonstrated
promising results,2-7 but these triplet sensitizers are all based on
mono-chromophore profile.2-7 Although some molecular arrays
were reported with triplet excited state populated upon
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In order to overcome the above challenges, herein we
spectroscopy, as well as DFT/TDDFT calculations.
prepared Bodipy/aza-Bodipy based molecular arrays that show 10 Intramolecular energy transfer from the Bodipy energy donor to
View Article Online
DOI: 10.1039/C3SC52323C
converter) was observed. The triplet photosensitizers were used
for photooxidation of 1,5-dihydroxylnaphthalene to produce
juglone.3,38-41 Our results may be useful for future development of
panchromatic absorption in visible region, with the triplet excited
state of the molecular arrays were populated upon photoexcitation.
In this case the production of nonemissive triplet excited state,
rather than luminescence, was enhanced by the RET effect. The
the aza-Bodipy energy acceptor (at the same time, the spin
5
photophysical properties of the molecular arrays were studied 15 a new triplet photosensitizers which are enhanced with the
with steady-state and femtosecond/nanosecond time-resolved intramolecular RET effect.
Br
N3
OH
O
O
Br
H
N3
OH
O
O
N
f
e
N
c
20
25
30
35
40
45
50
55
d
N
a
b
CHO
CHO
CHO
5
4
6
2
1
3
CHO
7
8
9
N3
O
N3
O
O
O
NO2
O
O
k
g
j
i
h
N
F
N
O
O
B
N
N
O
OH
F
B
14
15
F
F
12
11
13
10
N
N
B
I
I
N
F
N
F
N
N
N
I
I
N
N
F
N
HN
l
m
N
N
F
n
o
B
B
O
O
F
F
N
N
N
O
O
O
O
O
O
N
16
m
17
N
N
18
B-1
O
O
q
p
N
N
B
I
I
I
I
N
F
N
N
F
N
F
B
F
O
N
O
N
O
N
O
N
N
N
N
N
N
N
N
N
O
O
O
O
B-3
B-2
N
N
B
N
B
N
F
N
N
F
F
B
F
N
N
B
F
F
F
F
N
N
60 Scheme 1 Preparation of Bodipy/aza-Bodipy triad as triplet photosensitizers (B-1, B-2 and B-3): (a) anhydrous K2CO3, 1,2-dibromoethane, dry ethanol,
Ar, 70 ºC, 30 min; (b) NaN3, DMF, 100 ºC, 10 hr; (c) NaH, n-Butyl bromide, DMF, rt, 2 h; (d) POCl3/DMF, rt, 3 h, 60 ºC, 6 h; (e) anhydrous K2CO3, 1,2-
dibromoethane, dry ethanol, Ar, 70 ºC; (f) NaN3, DMF, 100 ºC, 10 h; (g) 2, 4-dimethylpyrrole, TFA, anhydrous CH2Cl2, rt, 12 h; DDQ, BF3 ⋅ Et2O, 12 h;
(h) 3-carbaldehyde, acetic acid, piperidine, microwave irradiation, 5 min; (i) propargyl bromide, anhydrous K2CO3, dry DMF, Ar, rt, 4 h; (j) Benzaldehyde,
absolute ethyl alcohol, 10% sodium hydroxide solution, rt, 3 hours; (k) nitromethane, diethylamine, methanol, refluxed, 18 h; (l) ammonium acetate,
65 absolute butanol, refluxed, 24 h; (m) BF3⋅OEt2, diisopropylethylamine, rt, 20 h; (n) NIS, mixture (3:1) of chloroform and acetic acid, 30 ºC, 12 h; (o)
compound 3, sodium ascorbate, CuSO4, rt, Ar, 24 h; (p) compound 10, sodium ascorbate, CuSO4, rt, Ar, 24 h; q) compound 11, sodium ascorbate, CuSO4,
rt, Ar, 20 h.
2
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was used to evaluate the intramolecular energy transfer for the
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FRET molecular arrays.31a,34,50-53 Furthermore, we found that the
2. Results and Discussions
DOI: 10.1039/C3SC52323C
fluorescence of the aza-Bodipy 17 was also quenched in
compound 18, indicates that the heavy atom effect is significant
60 (two iodine atoms were attached at the π-core of aza-Bodipy).3-6
2.1. Molecular Design and Synthesis
The triplet photosensitizers are based on Bodipy chromophore,
owing to its good photophysical properties, such as strong
absorption of visible light (large molecular absorption
coefficients ε), high fluorescence quantum yield and good
photostability.32-33,42-44 The unsubstituted Bodipy showing
absorption at 500 nm, which is used as energy donor in B-2
10 (Scheme 1). Aza-Bodipy is known to show much longer
absorption wavelength, e.g. the energy level of its S1 excited state
is lower than the S1 state of the normal Bodipy, thus aza Bodipy
was used as the intramolecular energy acceptor.3-4,6,35,45 Iodo-
substitution is attached at te π-core of aza-Bodipy, thus the
15 energy acceptor unit acts at the spin converter to produce the
triplet excited state. The energy donor and the energy acceptor
were connected by the Click chemistry (Huisgen cycloaddition
reaction). In B-3, the styryl Bodipy was used as the energy
donor.46-47 B-1 was also prepared as a reference compound, in
20 which only one visible light-absorbing chromophore was used.
All the compounds were obtained with moderate to satisfactory
yields.
5
500
a
400
b
400
300
200
100
0
300
200
100
0
17
18
10
65
B-2
500 550 600 650
Wavelength / nm
700 750 800 850
Wavelength / nm
70
Fig.
2 Fluorescence emission spectra of Bodipys and the triplet
photosensitizers. The emission spectra of (a) B-2 and 10, λex = 490 nm
and (b) 17 and 18, λex = 660 nm (c = 1.0×10-5 M in toluene 20 °C).
The solvent-dependency of the UV/Vis absorption and
75 fluorescence emission of the compounds were also studied (see
ESI†). Generally the UV/Vis absorption and emission of the
compounds are dependent on the solvents. For example, the B-1
gives weaker emission in acetonitrile than that in toluene.
However, there is no clear trend in the solvent-dependency of the
80 emission of the compounds.
The intramolecular energy transfer of the triplet
photosensitizers was also evaluated with the luminescence
lifetime of the residual fluorescence of energy donor compared to
the free energy donor.54 The fluorescence lifetime of the energy
85 donor was reduced as compared to that of the reference
compounds (Table 1).
Recently, Akkaya et al. proposed that it is more appropriate to
compare the fluorescence excitation spectra with the UV/Vis
absorption spectra to evaluate the intramolecular energy transfer
90 efficiency of the triplet photosensitizers, than using the
conventional method of fluorescence quenching of the energy
donor.35,37 For B-1, the excitation spectrum is superimposable to
the UV/Vis absorption spectrum (Fig. 3). For B-2, however, the
normalized fluorescence excitation is weaker in the range of 450
95 nm − 550 nm, indicates inefficient intramolecular energy transfer.
The intramolecular energy transfer efficiency with excitation in
the 450 nm − 550 nm, where the energy donor give the strong
2.2 UV/Vis absorption and fluorescence spectra
Reference compound 10 shows the typical UV/Vis absorption of
25 the Bodipy chromophore at 504 nm (ε = 82000 M-1 cm-1).42 The
aza-Bodipy B-1 shows intense absorption at 683 nm (ε = 73000
M-1 cm-1).4 Triad B-2 shows strong absorption at both 504 nm (ε
= 165000 M-1 cm-1) and 683 nm (ε = 71000 M-1 cm-1). UV/Vis
absorption spectrum of B-2 is the sum of 10 and B-1 (note there
30 are two Bodipy chromophore in B-2). Therefore, there is no
significant interaction between the aza-Bodipy and the Bodipy
chromophores in B-2 at the ground state.30,35 Similar results were
observed for B-3 and B-1. Previously iodo-Bodipy or iodo aza-
Bodipy were prepared as triplet photosensitizers, but those triplet
35 photosensitizers are not based on multi-chromophores profile, as
a result only one major absorption band was observed in visible
spectral region.2-3,5-7,48-49
The fluorescence of the compounds was studied (Fig. 2 and
ESI†, Fig. S33). The fluorescence of the Bodipy or the styryl-
40 Bodipy energy donor were substantially quenched in the triplet
photosensitizers B-2 and B-3. Usually this quenching effect
2.4
1.0
2.5
2.0
1.5
1.0
0.5
0.0
B-1
B-2
B-3
a
100
b
0.8
0.6
0.4
0.2
1.8
45
Absorption
Excitation
Absorption
I
1.2
I
Excitation
0.6
105
50
0.0
0.0
500
600
λ / nm
700
500 600
λ / nm
700
400
500
600
700
Wavelength / nm
Fig. 3 Normalized UV/Vis absorption and fluorescence excitation spectra:
Fig.1 UV/Vis absorption spectra of B-1, B-2 and B-3 (c = 1.0×10-5 M in
55 toluene, 20°C).
110 (a) B-1 (λem = 750 nm); (b) B-2 (λem = 760 nm) (c = 1.0 × 10-5 M in
toluene, 20 °C).
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Chemical Science
Page 4 of 12
absorption, is generally in the range of 40−50 %. This
conclusion is in stark contrast to the evaluation based on the
fluorescence quenching effect, a typical method used in the
carbazole-styryl Bodipy energy donor.3,41,55 This conclusion was
supported by the spin density surface analysis of the triplet
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photosensitizers (see later section).56 Previously we reported
DOI: 10.1039/C3SC52323C
literatures to evaluate the FRET efficiency. Similar 60 Bodipy-iodo-Bodipy dyads with triplet state distributed on both
5
intramolecular energy transfer was observed for B-3 (ESI†, Fig.
S43). It should be pointed out that similar excitation spectra were
found for a dyad based on un-iodinated Bodipy-aza-Bodipy.35 We
propose the inefficient intramolecular energy transfer is due to
the intramolecular electron transfer.35 One piece of evidence is
the energy donor and the energy acceptor.36d
2.4 Femtosecond transient difference absorption spectroscopy:
singlet state energy transfer
In order to study the singlet energy transfer in B-2 and B-3
65 upon photoexcitation, femtosecond time-resolved transient
absorption spectroscopy was studied (Fig. 5 and Fig. 6).
10 the reduced fluorescence lifetime, as well as the triplet excited
state lifetime of the iodo-aza-Bodipy parts in the triads compared
to that of B-1 (Table 1).
The UV-Vis absorption spectra of B-2 and B-3 do not change
upon monochromatic light irradiation (see ESI †, Fig. S44).
15 Moreover, we observed high singlet oxygen quantum yield for B-
Bleaching band at 505 nm was observed instantly upon
photoexcitation with femtosecond pulsed laser (Fig. 5a). The
bleaching is due to the depletion of the ground state of the Bodipy
70 chromophore (intramolecular energy donor). The fast component
of the decay may be due to vibrational relaxation (k = 1.7×1011 s-
1). The slow decay kinetic is assigned as the decay of the singlet
excited state of compound 10 (τ = 3.5 ns. Fig. 5b), which is close
to the results with the luminescence method (4.2 ns, Table 1). The
75 decay profile of compound 10 (observation of a fast and a slow
component for the decay upon femtosecond pulsed laser
excitation) is similar to a recently reported Bodipy compound.35
2
and B-3, therefore, we propose that the cis-trans
photoisomerization of the C=C bonds in B-2 and B-3 is not
significant.
2.3 Nanosecond transient difference absorption spectra
20 In order to study the triplet excited state of the triplet
photosensitizers, the nanosecond time-resolved transient
difference absorption spectra of the compounds were studied (Fig.
4).3,6,35 Upon pulsed laser excitation, bleaching band at 678 nm
was observed for B-1. Transient absorption bands in the 350 nm
25 − 600 nm region were observed. These features are similar to a
reported iodo-aza Bodipy compound.3,6 The lifetime of the
transient species was determined as 7.2 μs, which was greatly
quenched in aerated solution (τ < 20 ns). Therefore, the transient
species observed was attributed to the triplet excited state. Similar
30 transient spectrum was observed for B-2 (Fig. 4c) and B-3 (see
ESI†, Fig. S51). Interestingly, no bleaching bands at 504 nm or
593 nm were observed, therefore, we conclude that the triplet
state is localized on the aza Bodipy part, not on the Bodipy or the
0.0
0.00
80
-0.2
2000 ps
-0.03
-0.4
62 ps
Δ A
11.5 ps
4.31 ps
1.88 ps
1.07 ps
-0.6
-0.06
-0.09
-0.8
-1.0
85
b
a
0
1000 2000 3000
Time / ps
500
600
700
800
Wavelength / nm
Fig. 5 (a) Femtosecond transient absorption spectra of compound 10 upon
90 femtosecond pulsed laser excitation at λex = 504 nm in toluene with
several time delays between 1 and 2000 ps. (b) Decay profile at λ = 505
nm. 20 °C.
0.08
0.06
35
a
b
0.04
0.04
b
τ = 7.2 μs
0.0
0.00
0.00
27.1 μs
95
0.02
21.6 μs
...
0 μs
-0.3
2000 ps
62 ps
11.5 ps
4.40 ps
1.83 ps
1.03 ps
-0.04
-0.03
40
505 nm
680 nm
0.00
-0.6
-0.9
-0.08
400 500 600 700 800
Wavelength / nm
0
10
Time / μs
20
30
-0.06
-0.09
a
100
0.06
0.04
0.02
0.00
c
0.05
0.00
0
10 20 30 40 50
Time / ps
500 600 700 800
Wavelength / nm
d
45
Fig. 6 (a) Femtosecond time-resolved transient difference absorption
spectra of dyad B-2 upon laser pulsed excitation (λex = 504 nm) in toluene;
105 (b) Decay profile of at 505 and 680 nm. 20 °C.
20.1 μs
18.5 μs
...
τ = 5.5 μs
-0.05
-0.10
0 μs
50
The femtosecond transient absorption spectra of the dyad B-2
were studied (Fig. 6). Similar to compound 10, significant
bleaching band at 506 nm appeared immediately after the
photoexcitation. Then the bleaching decreased and a new
110 bleaching band at 680 nm developed concomitantly. This change
is attributed to the singlet state energy transfer from Bodipy to the
iodo aza-Bodipy part. The energy transfer rate constant was
400 500 600 700 800
Wavelength / nm
0
10
Time / μs
20
30
Fig. 4 Nanosecond time-resolved transient difference absorption spectra
of (a) B-1 and (c) B-2. The decay curves are (b) B-1 at 430 nm and (d) B-
55 2 at 430 nm, respectively. After pulsed excitation at 355 nm (c = 2.0×10-5
M in deaerated toluene, 20 °C).
4
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Chemical Science
Table 1 Photophysical parameters of the organic triplet photosensitizers and the reference compounds.
View Article Online
DOI: 10.1039/C3SC52323C
a
n
ε b
0.73
λem
714
ΦF (%) c
0.21 f
τF / ns d
0.12 j
τT / μs e
7.2(4.8)
5.5(3.7)
4.1
ΦET
k
ET/×1010 s-1 m
λabs
683
l
l
−
−
B-1
B-2
B-3
10
11
17
18
a
504/683
593/683
504
1.65/0.71
2.20/0.81
0.82
520/714
610/714
520
0.53 g/0.15 f
0.16h /0.22 f
64.2
2.23i / 0.06 j
3.04k /0.04 j
4.20
2.1
1.1
46.9%
34.3%
l
l
l
−
−
−
l
l
l
593
1.00
610
78.3
4.63
−
−
−
l
l
l
688
0.83
716
48.3
3.58
−
−
−
l
l
680
0.84
711
0.28
0.46
4.2
−
−
In toluene (1.0×10-5 M). In nm. Molar absorption coefficient. 105 M-1 cm-1. Fluorescence quantum yields. In CH2Cl2. Fluorescence lifetimes in
b
c
d
e
f
5 toluene. Triplet state lifetimes, measured by transient absorption. In toluene. The values in parenthesis are measured in CH3CN. λex = 660 nm. λem
=
683 nm. g λex = 480 nm, λem = 504 nm. h λex = 570 nm, λem = 610 nm. i λex = 470 nm, λem = 504 nm. λex = 670 nm, λem = 683 nm. k λex = 405 nm, λem = 610
j
nm.. Not applicable. m Steady-state approach based on change in fluorescent lifetime, kET = (1/τ) −(1/τo), τo and τ are the unquenched and quenched
l
n
lifetimes, respectively. The energy transfer efficiency calculated with the change of the fluorescence lifetime of donor. ΦET = 1−(τ/τo), τ o and τ are the
unquenched and quenched lifetimes, respectively. 20 °C.
10
calculated as kET = (4.3±0.3)×1010 s-1 by monitoring the
development of the bleaching band at 680 nm. This value is close
to the result for FRET dyad with Bodipy-aza-Bodipy dyad,30b,35
and it is in agreement with the fluorescence quenching studies
photophysics of the dyad triplet photosensitizers can be
rationalized by the DFT/TDDFT calculations.
The DFT cacluation show that the HOMO and HOMO−1
molecular orbitals are localized on the two different Bodipy units
15 (kET = 2.1×1010 s-1. Table 1). These results indicate that the 50 in B-2. Based on the molecular structure, these two orbitlas
singlet energy transfer was not hampered by the iodination of the
energy acceptor (aza-Bodipy). Femtosecond transient absorption
of B-3 was also studied and faster energy transfer rate constants
were obtained, kET = (5.1±0.4)×1011 s-1, respectively (see ESI†,
should be degeneralized, i.e. the energy level of the two
molecular orbitals should be the same. Indeed the energy level of
both HOMO and HOMO−1 is −5.40 eV. Thus the DFT
calculation can be verified. The same is true for the molecular
20 Fig. S53). This faster energy transfer is tentatively attributed to 55 orbitals of LUMO+1 and LUMO+2. These two MOs are
the better spectra overlap of the energy donor/acceptor in B-3.
localized on the different Bodipy units in B-2, but the energy
levels are fully degenerated (both are −2.40 eV). Same results
were obtained for B-3. The HOMO/HOMO−1 are with energy of
−4.88 eV, and the LUMO+1/LUMO+2 are with energy level of
60 −2.42 eV.
2.5 DFT calculations on the triplet photosensitizers
The geometry of the triplet photosensitizers was optimized
with the DFT theory, and the UV/vis absorption, the fluorescence
25 and the triplet excited states were calculated with the time-
dependent DFT (TDDFT) method.
The spin density surfaces of the triplet photosensitizers B-1 −
B-3 were calculated (Fig. 7). All the spin density surfaces are
localized on the iodo aza-Bodipy moieties, thus the triplet state of
30 the triplet photosensitizers are localized on the iodo Aza-Bodipy
parts, which are in agreement with the femtosecond and the
nanosecond transient absorption spectra (Fig. 4 and Fig. 6) and
the DFT/TDDFT calculations (Fig. 8 and Table 2).
65
B-1
B-2
The geometry of the singlet excited states of B-2 were also
35 optimized. S1 and S2 are charge transfer states. S3 state is
localized on iodo aza-Bodipy, which supports the fact that iodo-
aza Bodipy is the energy acceptor (Fig. 8 and Table 2). The triplet
excited state of B-2 was also calculated. T1 is localized on iodo
Aza-Bodipy moiety, which is in full agreement with the
40 nanosecond time-resolved transient absorption spectra (Fig. 4).
Furthermore, the T2 and T3 states are localized on the two energy
donor Bodipy moieties, which are degenerated (the two triplet
excited states share the same energy level, Table 2). This result is
in agreement with the chemical structure of B-2. Similar results
45 were found for B-3 (see ESI†, Fig. S56). Therefore, the
B-3
70
Fig. 7 Spin density surface of B-1 − B-3. Calculated at B3LYP/3-
21G/genecp/LanL2DZ level with Gaussian 09W.
2.6 Application in photooxidation mediated by singlet oxygen
75 (1O2)
In order to evaluate the efficacy of these broadband-absorbing
triplet photosensitizers, photooxidation catalyzed by the triplet
photosensitizers are studied. The photooxidation was mediated
with 1O2, which was produced by the photosensitizing of O2 in the
80 presence of the triplet photosensitizers upon visible light
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Chemical Science
Page 6 of 12
Table 2 Selected electronic excitation energies (eV) and corresponding oscillator strengths (f), main configurations and CI coefficients of theVlioeww-Alyrtiincgle Online
electronically excited states of B-2. Based on the optimized ground state geometries and the optimized S state geometries. Calculated at
DOI: 10.1039/C3SC52323C
1
TDDFT//B3LYP/LanL2DZ level.a
Electronic transition
S0→S1
TDDFT//B3LYP/6-21G(d)
Energyb
f c
Composition d CIe
UV/Vis abs.
1.93 eV / 643 nm
0.0000
H→L
0.7071
S0→S2
S0→S3
S0→S5
1.93 eV / 643 nm
2.10 eV / 591 nm
2.52 eV / 492 nm
0.0000
0.7159
0.2213
H−1→L
H−2→L
H−5→L
H−4→L
H−5→L
H−4→L
H−1→L+1
H→L+2
H→L
H−1→L
H−2→L
H−1→L
H−2→L
H→L+2
0.7071
0.7025
0.3660
0.6014
0.5988
0.3634
0.5365
0.4315
0.7071
0.7071
0.6999
0.1174
0.6934
0.7084
S0→S6
2.66 eV / 466 nm
3.03 eV / 409 nm
0.1784
0.7454
S0→S16
Fluorescence
S1→S0
S2→S0
S3→S0
1.35 eV / 918 nm
1.60 eV / 774 nm
2.01 eV / 618 nm
0.0000
0.0000
0.6600
Triplet excited states S0→T1
S0→T2
1.20 eV / 1132 nm
1.61 eV / 768 nm
0.0000
0.0000
S0→T3
1.61 eV / 768 nm
0.0000
H−1→L+1
0.7085
5
a Calculated by TDDFT//B3LYP/genecp. FL stands for fluorescence. b Only selected low-lying excited states are presented. c Oscillator strength. d
stands for HOMO and L stands for LUMO. Only the main configurations are presented. e CI coefficients are in absolute values.
H
10
15
20
25
30
35 Fig. 8 Selected frontier molecular orbitals involved in the excitation and the singlet/triplet excited states of B-2. CT stands for conformation
transformation. The left column is UV/Vis absorption (based on the ground state geometry), the middle column is the fluorescence emission (based on the
S1 state geometry) and the right column is the triplet excited state (based on the ground state geometry). For clarity, only the selected excited states were
presented. The calculations are at the B3LYP/genecp/LanL2DZ level using Gaussian 09W.
6
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Chemical Science
3.0
2.0
1.0
0.0
3.0
It should be pointed out that the apparent photooxidation
kinetics are affected by many factors, such as the matching of the
View Article Online
DOI: 10.1039/C3SC52323C
a
b
40 min
...
2 min
0 min
2.0
5
40 min
...
...
2 min
0 min
0 min
...
...
60 absorption of triplet photosensitizers with the irradiation light
source (xenon lamp). Therefore we compared the radiance
spectrum of the xenon lamp used in the study and the UV-Vis
absorption spectra of the triplet photosensitizers (ESI †, Fig. S49).
Different match between the UV-Vis absorption spectra and the
65 lamp profile was observed. Photo-induced intramolecular
electron transfer may be also responsible for the detrimented
photosensitizing ability of B-3. In order to confirm the
intramolecular energy transfer in B-2 and B-3, and to prove the
effect of RET, the photooxidation of the triplet photosensitizers
70 are compared with monochromatic light excitation (ESI †, Fig.
S48).
1.0
40 min
0.0
400
600
800
300 400 500 600 700
Wavelength / nm
Wavelength / nm
10
3.0
0.0
d
Ir-1
c
40 min
...
-0.2
-0.4
-0.6
-0.8
2.0
...
MB
B-3
TPP
2 min
0 min
15
1.0
Table 3 Pseudo-first-order kinetics parameters, 1O2 generation quantum
efficiencies and yields of Juglone for the photooxidations of DHN using
compound B-1, B-2, B-3, TPP, MB and (ppy)2Ir(Phen) (Ir-1) as triplet
75 photosensitizers.
B-1
6
B-2
8
0.0
400
600
800
0
2
4
10
Wavelength / nm
Time / min
20
Fig. 9 UV-vis absorption spectral change for the photooxidation of DHN
using (a) B-1, (b) B-2, (c) B-3 as the singlet oxygen (1O2) photosensitizer.
(d) Plots of ln(Ct/C0) vs. irradiation time (t) for the photooxidation of
DHN with different sensitizers. c [sensitizers] = 1.0 × 10-5 M; [DHN] =
25 1.0 × 10-4 M (light intensity: 17 mW/cm2. CH2Cl2/CH3OH=9/1; 20 °C).
c
k
obs /min-1
0.081
0.093
0.056
0.070
0.038
0.013
vi/10-5 M min-1a
Yield/%b
84.8
87.2
89.7
90.5
76.2
44.3
ττ/μs
7.2
5.5
4.1
TPP 82.5
ΦΔ
B-1
0.810
0.68 d
d
B-2
B-3
0.930
0.560
0.700
0.381
0.125
0.69
0.58 d
0.62 e
0.57e
−
excitation. 1,5-dihydroxylnaphthalene (DHN) was used as the 1O2
scavenger and juglone was produced,3,38-41 which can be used as
intermediates for preparation of bioactive compounds.58
MB
Ir-1
51.9
0.88
a Initial rate of DHN consumption. b Yield of Juglone after reaction for 35
min. c Quantum yield of singlet oxygen (1O2). d with methylene blue (MB)
as standard (ΦΔ = 0.57), λex = 675 nm. e Literature values.41,60
Upon broadband excitation with xenon lamp, the absorption of
30 DHN at 301 nm decreased and the absorption of the product
juglone at 427 nm increased (Fig. 9). The decrease of the
absorption at 301 nm can be followed to monitor the kinetics of
the photooxidation.38 For all the new triplet photosensitizers, the
change of the absorption at 301 nm is substantial, indicated the
35 significant consumption of DHN with the photosensitizing effect
of the triplet photosensitizers. Furthermore, no decrease was
observed for the absorption of the triplet photosensitizers,
indicated that the photostability of the triplet photosensitizers are
satisfactory. The photosensitizing ability of the conventional
40 triplet photosensitizers, such as TPP, MB and Ir(ppy)2(phen)[PF6]
(Ir-1) were also studied for comparison.38 All these conventional
triplet photosensitizers are based on mono-chromophore
structural profile. For Ir-1, the change of the absorption at 301
nm is small, indicated non-efficient photosensitizing due to the
45 weak absorption of the normal cyclometalated Ir(III) complexes
in visible region.59
The photosensitizing ability of the triplet photosensitizers can
be quantitatively compared by plotting the ln(Ct/C0) against the
irradiation time (Fig. 9).38 The results show that B-2 is more
50 efficient than B-1, thus demonstrated that panchromatic
absorption of triplet photosensitizer B-2 makes the triplet
photosensitizer more efficient. For B-3, however, the
photosensitizing ability is less efficient compared to B-1, which is
attributed to the non-efficient intramolecular energy transfer.
55 Notably the new triplet photosensitizers are generally more
efficient than the conventional triplet photosensitizers such as
TPP, MB and Ir-1.
80
85
90
0.9
a
B-1
b
0.95
0.8
B-1
B-3
0.90
0.85
0.7
0.6
B-2
0
10
20
Time / s
30
40
0
10 20 30 40
Time / s
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
B-1
B-3
LED
B-1
B-2
LED
Emission
c
d
Emission
400 500 600 700 800
Wavelength / nm
500
600
700
Wavelength / nm
Fig. 10 Singlet oxygen (1O2) generation with photoexcitation at the
absorption of the energy donor of the dyad triplet photosensitizers.
95 Absorbance decrease of DPBF with time in the presence of
photosensitizers: (a) B-1 and B-2. Photoirradiated with blue LED (light
power density at the photoreactor: 0.35 mW/cm2); (b) B-1 and B-3,
Photoirradiated with orange LED (light power density at the photoreactor:
0.42 mW/m2). Normalized UV/Vis absorption and LED emission spectra:
100 (c) UV/Vis absorption spectra of B-1, B-2 and the emission spectrum of
the green LED; (d) UV/Vis absorption spectra of B-1, B-2 and the
emission spectrum of orange LED. c = 1.0 × 10-5 M, 20 °C.
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In order to study the effect of the intramolecular RET on the
the present molecular dyads and the conventional FRET dyads is
photooxidation efficiency, the dyad and triad photosensitizers 55 that the energy acceptors of the present triads are nonfluorescent,
View Article Online
DOI: 10.1039/C3SC52323C
intersystem crossing (ISC) of the energy acceptor is efficient so
that triplet excited state is produced. For the new triplet
photosensitizers we prepared, both the energy donor and the
were photoirradiated at the absorption wavelength of the energy
donor, and the photooxidation was compared with the reference
triplet photosensitizer B-1, which is without the RET energy
funnelling effect (Fig. 10). For example, a blue LED (emission in
due to the heavy atom effect of iodine. On the other hand, the
5
465 − 470 nm, Fig. 10c) was used for the photooxidation with B- 60 energy acceptor give strong visible light absorption, but at
1 and B-2 as the triplet photosensitizer. Both B-1 and B-2 give
strong absorption at 683 nm (due to aza-Bodipy unit, Fig. 10c).
10 However, B-2 gives strong absorption in the range 460−505 nm,
but B-1 show no strong absorption in this region. As a result, the
different wavelength, thus broadband absorption was observed.
Conventional triplet photosensitizers, such as the porphyrin or
iodo-/bromochromophore, contain only one light-harvesting
chromophore, thus there is only one major absorption band in
photooxidation with B-2 is more efficient with B-1 as the triplet 65 visible region. Singlet energy transfer from the energy acceptor to
photosensitizer (Fig. 10a). Similarly, a yellow LED (emission in
the region 590 − 595 nm) was used for photoirradiation of B-3,
15 which gives strong absorption at the yellow LED emission band.
B-1 shows only one absorption band at 595−720 nm. The results
energy donor (iodo aza-Bodipy) occurs, in turn triplet excited
state was produced. The photophysical properties and the energy
transfer of the triplet photosensitizers were studied by
fluorescence quenching, fluorescence excitation spectra,
demonstrated that photooxidation of B-3 are much more efficient 70 femtosecond and nanosecond time-resolved transient absorption
than that of B-1 (Fig. 10b). Therefore, the FRET effect of the
triplet photosensitizers are useful for improvement of the
20 performance of photosensitizing.
spectroscopy, as well as DFT/TDDFT calculations. The
panchromatic visible light-absorbing triplet photosensitizers were
used for singlet oxygen (1O2) mediated photooxidation, with 1,5-
dihydroxylnaphthalene (DHN) as the 1O2 scavenger. The
75 photosensitizing ability of the broadband absorbing triplet
photosensitizers is improved compared to the reference triplet
photosensitizers and the conventional triplet photosensitizers that
are based on monochromophore profile. Our broadband
absorbing triplet photosensitizers based on the RET effect is a
80 new method for designing organic triplet photosensitizers to
access predictable ISC, and to enhance the absorption of visible
light. These results will be useful for the development of new
triplet photosensitizers and for the application of these
compounds in photocatalysis and photophysical studies.
Donor
Acceptor
Photocatalytic Reaction
OH
1(*Bod- AzaBod)
1O2
1(Bod-*AzaBod)
3(Bod-*AzaBod)
RET
O
O
DHN
OH
O
25
ISC
− H2O
3O2
OH
3.03 eV
409 nm
2.01 eV
618 nm
1.20 eV
1132 nm
O
E
OH
Juglone
GS
HO
Scheme 2 Jablonski diagram of photophysics of the Aza-Bodipy compounds and
85 4. Experimental section
30 the application for photooxidation. Exemplified with B-2 as the triplet
photosensitizer. E is energy. GS is ground state (S0). 1(*Bod-AzaBod) is singlet
excited state localized on Bodipy, and 1(Bod-*AzaBod) is singlet excited state
localized on Aza-Bodipy. RET is Resonance Energy Transfer. ISC is intersystem
crossing. 3(Bod-*Aza-Bod) is the triplet excited state localized on Aza-Bodipy. Bod
35 stands for Bodipy.
4.1. Materials
All the chemicals used in synthesis are analytical pure and were
used as received. UV/Vis absorption spectra were measured with
Agilent 8453 UV/visible spectrophotometer. Fluorescence spectra
90 were recorded on Shimadzu RF-5301PC spectrofluorometer.
Luminescence lifetimes were measured on
luminescence lifetime spectrometer (Edinburgh Instruments, UK).
a
OB920
The photophysical processes involved in the triplet
photosensitizers upon photoexcitation are summarized in Scheme
2. Both the energy donor and the energy acceptor can be excited
upon irradiation with visible light. The intramolecular energy
40 transfer from the Bodipy to the iodo aza-Bodipy occurred. In turn
the ISC of the iodo-Bodipy takes place, thus the triplet state of
the aza-Bodipy part is populated. Note the backward triplet
energy transfer from the iodo-aza-Bodipy to the unsubstituted
Bodipy is impossible, due to the much higher T1 state energy
45 level of the unsubstituted Bodipy (1.65 eV) than the aza-Bodipy
part (1.20 eV).
4.2. Synthesis
Synthesis of 10. Under N2 atmosphere, a solution of compound 9
95 (859.5 mg, 4.5 mmol) and 2,4-dimethylpyrrole (2.0 mL, 945 mg,
9.0 mmol) in dry CH2Cl2 (100 mL) was stirred at RT. Under ice-
cooling condition, trifluoroacetic acid ( 0.1 mL) was added into
the mixture. The mixture was stirred at RT over night. A solution
of DDQ (1.02 g, 4.5 mmol) in THF (40 mL) was added, then the
100 mixture was stirred at RT for 7 h. Triethylamine (13.5 mL) was
added into the mixture dropwise with ice bath cooling, then the
mixture was stirred for 0.5 h. BF3⋅Et2O (13.5 mL) was added
dropwise. The reaction mixture was stirred over night. The
solution was concentrated under reduced pressure and the
105 residual was poured into water (200 mL), the mixture was stirred
for 24 h. The mixture was extract with CH2Cl2 and the organic
layer was dried over anhydrous MgSO4. The solvent was
evaporated under reduced pressure. The crude product was
purified using column chromatography (silica gel, CH2Cl2:hexane
3.0 Conclusion
In conclusion, broadband absorbing organic triplet
photosensitizers were designed based on the intramolecular
50 resonance energy transfer (RET) effect, with Bodipy or styryl-
Bodipy as the intramolecular energy donor and the bisiodo aza-
Bodipy as the energy acceptor (also as the spin converter, so that
the triplet excited state can be produced). The difference between
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1
= 1:1, v/v) to give 3 as red power. Yield: 214.5 mg (11.6%). H
(0.024 mmol, 5.8 mg) were added and the mixture was stirred at
RT for 24 h. Then the reaction mixture was washed with water
and extracted with CHCl3. The organicDpOhI:a1s0e.1w03a9s/Cd3riSeCd52o3v2e3rC
NMR (400 MHz, CDCl3): 7.21 (d, 2H, J = 12.0 Hz), 7.04 (d, 2H,
J = 8.0 Hz), 5.98 (s, 2H,), 4.21 (t, 2H, J = 8.0Hz), 3.66 (t, 2H, J =
View Article Online
8.0Hz), 2.55 (s, 6H), 1.43 (s, 6H). TOF HRMS ESI+: m/z calcd 60 Na2SO4 and evaporated to dryness. The product was purified by
5
for [C21H22BF2N5O+H]+: 409.1995; found: 409.1862.
column chromatography (silica gel, CH2Cl2/CH3OH, 80:1, v/v) to
1
afford deep blue solid. Yield: 28.0 mg (33.2%). H NMR (400
Synthesis of 11. Compound 6 (69 mg, 0.3 mmol) was dissolved
in dry DMF (5 mL). Then compound 10 (109.8 mg 0.3 mmol)
was added, followed by acetic acid (10 drops) and piperidine (10
drops). The mixture was subjected to microwave irradiation (5
10 min, 150 °C) under Ar atmosphere. Then the solution was poured
into ice/water mixture and extracted with CH2Cl2. The organic
layer was dried over Na2SO4 and evaporated to dryness, the
mixture was purified by column chromatography (silica gel, ethyl
acetate/hexanes, 1/15, v/v) to give blue solid. Yield: 42 mg (22.1
MHz, CDCl3): 7.79−7.76 (m, 6H), 7.68 (d, 4H, J = 8.2 Hz),
7.44−7.42 (m, 8H), 7.16 (d, 4H, J = 9.4 Hz), 7.06 (d, 4H, J = 10
65 Hz), 6.96 (d, 4H, J = 7.0 Hz), 5.96 (s, 4H), 5.28 (d, 4H, J = 6.7
Hz), 4.81 (t, 4H, J = 4.1Hz), 4.44 (t, 4H, J = 6.7Hz), 2.54 (s, 12H),
1.39 (s, 12H). 13C NMR (100 MHz, CDCl3) δ 160.39, 158.45,
155.58, 148.21, 143.23, 141.45, 130.87, 128.27, 124.43, 121.36,
115.22, 114.29, 83.11, 66.40, 62.14, 56.52, 50.00, 31.12, 29.87,
70 16.87,
14.84.
HRMS
(MALDI):
m/z
calcd
for
[C80H68N13O4F6B3I2]+: 1675.3790; found: 1675.3795.
1
15 %). H NMR (400 MHz, CDCl3): 8.29 (s, 1H), 8.17 (d, 1H, J =
7.8 Hz), 7.78−7.70 (m, 2H), 7.48 (t, 2H, J = 8.3 Hz), 7.40 (t, 2H,
J = 8.8 Hz), 7.28−7.22 (m, 3H), 7.06 (d, 1H, J = 8.7 Hz), 6.67 (s,
1H), 6.00 (s, 1H), 4.31 (t, 2H, J = 7.1 Hz), 4.22 (t, 2H, J = 5.0
Synthesis of B-3. The synthesis procedure is similar to that of B-
1. To the solution of compound 11 (0.11 mmol, 75 mg) in a 6:1:1
mixture of CHCl3, EtOH and water (8 mL), compound 18 (0.041
Hz), 3.67 (t, 2H, J = 5.0Hz), 2.63 (s, 3H), 1.91−1.83 (m, 2H), 75 mmol, 35.2 mg), sodium ascorbate (0.0474mmol, 9.4 mg),
20 1.51 (s, 3H), 1.45 (s, 3H), 1.42−1.38 (m, 2H), 0.96 (t, 3H, J =
7.4Hz). HRMS (MALDI): m/z calcd for [C38H37N6OF2B]+:
642.3090; found: 642.3065.
CuSO4 (0.0236 mmol, 5.8 mg) were added and the mixture was
stirred at RT for 20 h. Then the reaction mixture was washed with
water and extracted with CHCl3. The organic phase was dried
over Na2SO4 and evaporated to dryness. The product was purified
80 by column chromatography (silica gel, CH2Cl2/CH3OH, 70:1,v/v)
to afford deep blue solid. B-3: Yield: 23.0 mg (26.1%). 1H NMR
(400 MHz, CDCl3): 8.25 (s, 2H), 8.15 (d, 2 H, J = 7.5 Hz),
7.79−7.69 (m, 14 H), 7.48−7.34 (m, 16 H), 7.14 (d, 4 H, J = 6.2
Hz), 7.07 (d, 4 H, J = 4.7 Hz), 6.95 (d, 4 H, J = 6.0 Hz), 6.60 (s, 2
85 H), 5.96 (s, 2 H), 5.24 (s, 4 H), 4.76 (s, 4 H), 4.38 (s, 4 H), 4.28 (t,
4 H, J = 5.6 Hz), 2.61 (s, 6 H), 1.87−1.83 (m, 4 H), 1.41−1.36 (m,
16 H), 0.94 (t, 6 H, J = 7.3Hz). 13C NMR (100 MHz, CDCl3) δ
160.42, 158.39, 154.21, 153.93, 145.17, 141.02, 138.51, 129.93,
127.72, 123.42, 120.51, 114.29, 109.22, 66.47, 62.20, 50.09,
90 43.13, 29.86, 29.52, 20.68, 15.18, 14.80, 14.03. HRMS (MALDI):
m/z calcd for [C80H68N13O4F6B3I2]+: 2141.6199; found:
2141.6350..
Synthesis of 18. Under Ar atmosphere, compound 17 (100 mg,
0.36 mmol) and NIS (100 mg, 0.36 mmol) was mixed in CHCl3/
25 CH3COOH (20 mL), the solution was stirred over night at 30 ºC.
The reaction mixture was washed with sodium thiosulphate
followed by sodium bicarbonate solution. Then the aqueous
mixture was extracted with CHCl3. The solvent was removed
under reduced pressure and the mixture was purified by column
30 chromatography (silica gel, dichloromethane/hexanes, 1/1, v/v) to
give red solid. Yield: 42.2 mg (60.3%). 1H NMR (400 MHz,
CDCl3): 7.80−7.77 (m, 4H), 7.68 (d, 4H, J = 8.8 Hz), 7.44−7.42
(m, 6H), 7.04 (d, 4H, J = 8.9 Hz), 4.74 (d, 4H, J = 2.4 Hz), 2.56 (t,
2H,
J
=
2.4 Hz). HRMS (MALDI): m/z calcd for
35 [C38H24N3O2F2BI2]+: 857.0019; found: 856.9991.
Synthesis of B-1. To the solution of compound 3 (0.14 mmol, 23
mg) in a mixture of CHCl3, EtOH and water (6:1:1, v/v, 6 mL),
compound 18 (0.035 mmol, 30 mg), sodium ascorbate (0.0237
mmol, 4.7 mg), CuSO4 (0.0118 mmol, 2.9 mg) were added and
40 the mixture was stirred at RT for 24 h. Then the reaction mixture
was washed with water and extracted with CHCl3. The organic
phase was dried over anhydrous Na2SO4 and evaporated to
dryness. The product was purified by column chromatography
(silica gel, CH2Cl2/CH3OH, 50:1, v/v) to afford deep blue solid.
45 Yield: 25.0 mg (60.3%). 1H NMR (400 MHz, CDCl3): 7.80−7.78
(m, 4H), 7.70 (d, 4H, J = 8.5 Hz), 7.44−7.42 (m, 6H), 7.30−7.28
(m, 6H), 7.07 (d, 4H, J = 7.9 Hz), 6.99−6.95 (m, 2H), 6.88 (d, 4H,
J = 8.7 Hz), 5.25 (s, 4H), 4.77 (d, 4H, J = 4.9 Hz), 4.37 (t, 4H, J =
Femtosecond transient difference absorption spectroscopy.
The ultrafast wavelength dependent pump probe spectroscopy
95 measurements were performed by using Ti:Sapphire laser
amplifier-optical parametric amplifier system (Spectra Physics,
Spitfire Pro XP, TOPAS) and commercial setup (Spectra Physics,
Helios). Pulse duration was measured as 100 fs. Wavelengths of
the pump beam were chosen according to the absorption spectra
100 of BODIPY unit as 504 nm for samples B-2 and compound 10.
592 nm excitation was used for B-3 and B-4. White light
continuum was used as a probe beam.
Nanosecond time-resolved transient difference absorption
spectroscopy. Nanosecond time-resolved transient difference
5.7Hz). 13C NMR (100 MHz, CDCl3) δ 160.47, 159.77, 148.19, 105 absorption spectra were recorded on a LP 920 laser flash
50 145.18, 132.53, 130.88, 129.64, 128.05, 124.21, 114.37, 78.23,
76.21, 56.03, 31.14. HRMS (MALDI): m/z calcd for
[C54H42N9O4F2BI2]+: 1183.1510; found: 1183.1545.
photolysis spectrometer (Edinburgh Instruments, Livingston, UK).
The sample solution were purged with N2 or Ar for 30 min before
measurements were taken. The samples were excited with a 355
nm or 532 nm nanosecond pulsed laser and the transient signals
110 were recorded on a Tektronix TDS 3012B oscilloscope.
Synthesis of B-2. The synthesis procedure is similar to that of B-
1. To the solution of compound 10 (0.14 mmol, 58 mg) in a 6:1:1
55 mixture of CHCl3, EtOH and water (12 mL), compound 18 (0.05
mmol, 43 mg), sodium ascorbate (0.047 mmol, 9.4 mg), CuSO4
Photooxidation details. A CH2Cl2/MeOH (9:1, v/v) mixed
solvent containing DHN (2.0 × 10-4 M) and triplet photosensitizer
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(5 mol % vs. DHN) was added into a round bottom flask (25 mL).
The solution was then irradiated using a 35 W xenon lamp
through a cut off filter (0.72 M NaNO2 aqueous solution, which is
transparent for light with wavelength > 385 nm). UV/Vis
absorption spectra were recorded at intervals of 2–5 min. The
consumption of DHN was monitored by the decrease of the UV
absorption at 301 nm, and the concentration of DHN was
calculated based on its molar extinction coefficient (ε = 7664 M-1
cm-1). The Juglone production was monitored by an increase in
View Article Online
5
10 the absorption at 427 nm. The concentration of juglone was
calculated by using its molar absorption coefficient (ε = 3811 M-1
cm-1 at 427 nm), and the yield of juglone was obtained by
dividing the concentration of Juglone with the initial
concentration of DHN.
† Electronic Supplementary Information (ESI) available: molecular
65 synthesis and structure characterization data, UV/Vis absorption and
emission spectra and photoxidation details. See DOI: 10.1039/b000000x/.
1 J. P. Celli, B. Q. Spring, I. Rizvi, C. L. Evans, K. S. Samkoe, S. Verma,
15
The 1O2 quantum yields (ΦΔ) of the photosensitizers were
calculated with Methylene Blue trihydrate (MB) at standard (ΦΔ
= 0.57 in DCM). Air saturated DCM was obtained by bubbling
air for 15 min. The absorbance of the 1O2 scavenger 1,3-
diphenylisobenzofuran (DPBF) was adjusted around 1.0 in air
B. W. Pogue and T. Hasan, Chem. Rev., 2010, 110, 2795–2838.
70 2 Y. Cakmak, S. Kolemen, S. Duman, Y. Dede, Y. Dolen, B. Kilic, Z.
Kostereli, L. T. Yildirim, A. L. Dogan, D. Guc and E. U. Akkaya,
Angew. Chem. Int. Ed., 2011, 50, 11937–11941.
3 N. Adarsh, M. Shanmugasundaram, R. R. Avirah and D. Ramaiah,
20 saturated dichloromethane. Then, the photosensitizer was added
to cuvette and photosensitizer’s absorbance was adjusted around
0.2−0.3. The cuvette was irradiated with monochromatic light at
the peak absorption wavelength for 10 seconds. Absorbance was
measured for several times after each irradiation. The slope of
25 absorbance maxima of DPBF at 414 nm versus time graph for
each photosensitizer were calculated. Singlet oxygen quantum
yield (ΦΔ) were calculated according to a modified equation:
Chem. Eur. J., 2012, 18, 12655–12662.
75 4 A. Gorman, J. Killoran, C. O’Shea, T. Kenna, W. M. Gallagher and D.
F. O’Shea, J. Am. Chem. Soc., 2004, 126, 10619–10631.
5 T. Yogo, Y. Urano, Y. Ishitsuka, F. Maniwa and T. Nagano, J. Am.
Chem. Soc., 2005, 127, 12162–12163.
6 N. Adarsh, R. R. Avirah and D. Ramaiah, Org. Lett., 2010, 12, 5720–
80
5723.
7 (a) S. G. Awuahab and Y. You, RSC. Adv., 2012, 2, 11169–11183; (b)
A. Kamkaew, S. H. Lim, H. B. Lee, L. V. Kiew, L. Y. Chungc and K.
Burgess. Chem. Soc. Rev., 2013, 42, 77–88; (c) F. Schmitt, J.
Freudenreich, N. P. E. Barry, L. Juillerat-Jeanneret, G. Süss-Fink and
B. Therrien. J. Am. Chem.Soc., 2012, 134, 754−757; (d) Y. You and
W. Nam, Chem. Soc. Rev., 2012, 41, 7061–7084; (e) J. Zhao, W. Wu,
J. Sun and S. Guo, Chem. Soc. Rev., 2013, 42, 5323–5351.
ksam
kref
F
ref
Φsam = Φref ×
×
30
(Eq. 1)
F
85
sam
Where ‘sam’ and ‘ref’ designate the photosensitizers and ‘MB’
respectively. k is the slope of difference in change in absorbance
8 J. Xuan and W. Xiao, Angew. Chem. Int. Ed., 2012, 51, 6828–6838.
9 S. Lalevée, M. Peter, F. Dumur, D. Gigmes, N. Blanchard, M. Tehfe, F.
35 of DPBF (414 nm) with the irradiation time, F is the absorption
correction factor, which is given by F = 1−10−O.D. (O. D. is the
optical density of the samples at the irradiation wavelength).
90
Savary and J. P. Fouassier, Chem. Eur. J., 2011, 17, 15027–15031.
10 M. Rueping, R. M. Koenigs, K. Poscharny, D. C. Fabry, D. Leonori
and C. Vila, Chem. Eur. J., 2012, 18, 5170–5174.
DFT calculations. The geometries of the compounds were
optimized using density functional theory (DFT) with B3LYP
40 functional and 3-21G basis set. There are no imaginary
frequencies for all optimized structures. The spin density surfaces
of the dyads were calculated at the B3LYP/3-21G/LanL2DZ level.
The UV/vis absorption, the fluorescence wavelength and the
triplet state energy levels were calculated with the time-
45 dependent DFT (TDDFT) method. All these calculations were
performed with Gaussian 09W.61
11 Q. Liu, Y. Li, H. Zhang, B. Chen, C. H. Tung and L. Z. Wu, Chem.
Eur. J., 2012, 18, 620–627.
95 12 Y. Ooyama and Y. Harima, Eur. J. Org. Chem., 2009, 2903–2934.
13 S. Baluschev, V. Yakutkin, T. Miteva, Y. Avlasevich, S. Chernov, S.
Aleshchenkov, G. Nelles, A. Cheprakov, A. Yasuda, K. Müllen and G.
Wegner, Angew. Chem. Int. Ed., 2007, 46, 7693 –7696.
14 H. Chen, C. Hung, K. Wang, H. Chen, W. S. Fann, F. Chien, P. Chen,
100
T. J. Chow, C. Hsu and S. Sun, Chem. Commun., 2009, 4064–4066.
15 (a) T. N. Singh-Rachford and F. N. Castellano, Coord. Chem. Rev.,
2010, 254, 2560–2573; (b) J. Zhao, S. Ji and H. Guo, RSC. Adv., 2011,
1, 937–950.
Acknowledgement
16 (a) C. C. Hofmann, S. M. Lindner, M. Ruppert, A. Hirsch, S. A.
Haque, M. Thelakkat and J. Köhler, J. Phys. Chem. B., 2010, 114,
9148–9156; (b) C. C. Hofmann, S. M. Lindner, M. Ruppert, A. Hirsch,
S. A. Haque, M. Thelakkatb and J. Köhler, Phys. Chem. Chem. Phys.,
2010, 12, 14485–14491; (c) D. Huang, J. Zhao, W. Wu, X. Yi, P.
Yang and J. Ma, Asian J. Org. Chem., 2012, 1, 264–273; (d) P.Yang,
W. Wu, J. Zhao, D. Huang and X. Yi, J. Mater. Chem., 2012, 22,
20273–20283; (e) L. Y. Chiang, P. A. Padmawar, J. E. Rogers-Haley,
G. So, T. Canteenwala, S. Thota, L.-S. Tan, K. Pritzker, Y.-Y. Huang,
S. K. Sharma, D. B. Kurup, M. R. Hamblin, B. Wilsone and A. Urbas,
J. Mater. Chem., 2010, 20, 5280–5293; (f) A. N. Amin, M. E. El-
Khouly, N. K. Subbaiyan, M. E. Zandler, S. Fukuzumi and F.
We thank the NSFC (20972024, 21073028 and 21273028), the 105
Royal Society (UK) and NSFC (China-UK Cost-Share Science
50 Networks, 21011130154), Science Foundation Ireland (SFI E.T.S.
Walton Program 11/W.1/E2061) and Ministry of Education
110
(SRFDP-20120041130005) for financial support.
Notes and references
115
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Chemical Science
D’Souza, Chem. Commun., 2012, 48, 206–208; (g) Y. Zhong, L. Si, H.
He and A. G. Sykes, Dalton Trans., 2011, 40, 11389–11395; (h) H.
65
Puntoriero, S. Campagna and R. Ziessel, Chem. Eur. J., 2013, 27,
8900–8912.
He, L. Si, Y. Zhong and M. Dubey, Chem. Commun., 2012, 48, 1886–
1888.
31 (a) O. A. Bozdemir, S. Erbas-Cakmak, O. O. Ekiz, A.VDieawnAaratinclde EO.nlUin.e
DOI: 10.1039/C3SC52323C
Akkaya, Angew. Chem. Int. Ed., 2011, 50, 10907–10912; (b) M.
5 17 P. Ceroni, Chem. Eur. J., 2011, 17, 9560–9564.
Suresh, A. K. Mandal, E. Suresh and A. Das, Chem. Sci., 2013, 4,
2380–2386; (c) C. Y.-S. Chung and V. W.-W. Yam, Chem. Sci., 2013,
4, 377–387; (d) H.-Y. Shiu, M.-K. Wong and C.-M. Che, Chem.
Commun., 2011, 47, 4367–4369.
70
18 (a) A. Monguzzi, M. Frigoli, C. Larpent, R. Tubino and F. Meinardi,
Adv. Funct. Mater., 2012, 22, 139–143; (b) Y. C. Simon and C.
Weder, J. Mater. chem., 2012, 22, 20817–20830.
32 A. C. Benniston and G. Copley, Phys. Chem. Chem. Phys., 2009, 11,
19 (a) B.-S. Du, C.-H. Lin, Y. Chi, J.-Y. Hung, M.-W. Chung, T.-Y. Lin,
4124–4131.
10
G.-H. Lee, K.-T. Wong, P.-T. Chou, W.-Y. Hung and H.-C. Chiu,
Inorg. Chem., 2010, 49, 8713–8723; (b) B. Minaev, H. Ågren and F.
De Angelis, Chem. Phys., 2009, 358, 245–257; (c) E. Jansson, B.
Minaev, S. Schrader and H. Ågren. Chem. Phys., 2007, 157–167; (d)
S. Fantacci and F. De Angelis, Coord. Chem. Rev., 2011, 255, 2704–
2726; (e) A. M. Soliman, M. Abdelhameed, E. Zysman-Colman and P.
D. Harvey, Chem. Commun., 2013, 49, 5544–5546.
75 33 R. Ziessel and A. Harriman, Chem. Commun., 2011, 47, 611–631.
34 Y. Zhao, Y. Zhang, X. Lv, Y. Liu, M. Chen, P. Wang, J. Liu and W.
Guo, J. Mater. Chem., 2011, 21, 13168–13171.
15
35 M. E. El-Khouly, A. N. Amin, M. E. Zandler, S. Fukuzumi and F.
D'Souza, Chem. Eur. J., 2012, 18, 5239–5247.
20 M. C. DeRosa and R. J. Crutchley, Coord. Chem. Rev., 2002, 233–234,
80 36 (a) G. Liang, L. Wang, Z. Yang, H. Koon, N. Mak, C. K. Chang and B.
Xu, Chem. Commun., 2006, 5021–5023; (b) Y. Wu and W. Zhu,
Chem .Soc. Rev., 2013, 42, 2039–2058 ; (c) Z. Guo, W. Zhu and H.
Tian, Chem. Commun., 2012, 48, 6073–6084; (d) C. Zhang, J. Zhao,
S. Wu, Z. Wang, C. W. Wu, J. Ma, S. Guo and L. Huang, J. Am.
351–371.
21 A. O’Connor1, W. M. Gallagher, A. T. Byrne and A. E. O’Connor,
20
Photochem. Photobiol., 2009, 85, 1053–1074.
22 (a) M. Ke, S. Yeung, W. Fong, D. K. P. Ng and P. Lo, Chem. Eur. J.,
2012, 18, 4225–4233; (b) D. Peceli, H. Hu, D. A. Fishman, S.
Webster, O. V. Przhonska, V. V. Kurdyukov, Y. L. Slominsky, A. I.
Tolmachev, A. D. Kachkovski, A. O. Gerasov, A. E. Masunov, D. J.
Hagan and Eric W. Van Stryland, J. Phys. Chem. A, 2013, 117,
2333−2346.
85
Chem. Soc., 2013, 135, 10566−10578.
37 Z. Kostereli, T. Ozdemir, O. Buyukcakir and E. U. Akkaya, Org. Lett.,
2012, 14, 3636–3639.
25
38 S. Takizawa and R. Aboshi and S. Murata, Photochem. Photobiol. Sci.,
2011, 10, 895–903.
23 M. T. Whited, P. I. Djurovich, S. T. Roberts, A. C. Durrell, C. W.
Schlenker, S. E. Bradforth and M. E. Thompson, J. Am. Chem. Soc.,
2011, 133, 88–96.
90 39 J. Sun, J. Zhao, H. Guo and W. Wu, Chem. Commun., 2012, 48, 4169–
4171.
40 Y. Liu and J. Zhao, Chem. Commun., 2012, 48, 3751–3753.
30 24 Y. Rio, W. Seitz, A. Gouloumis, P. Vázquez, J. L. Sessler, D. M.
Guldi and T. Torres, Chem. Eur. J., 2010, 16, 1929–1940.
41 L. Huang, X. Yu, W.Wu and J. Zhao, Org. Lett., 2012, 14, 2594–2597.
42 G. Ulrich, R. Ziessel and A. Harriman, Angew. Chem. Int. Ed., 2008,
25 D. I. Schuster, K. Li, D. M. Guldi, A. Palkar, L. Echegoyen, C.
Stanisky, R. J. Cross, M. Niemi, N. V. Tkachenko and H.
Lemmetyinen, J. Am. Chem. Soc., 2007, 129, 15974–15982.
95
47, 1184 – 1201.
43 L. Gai, H. Lu, B. Zou, G. Lai, Z. Shen and Z. Li, RSC. Adv., 2012, 2,
35 26 (a) A. Eggenspiller, A. Takai, M. E. El-Khouly, K. Ohkubo, C. P.
Gros, C. Bernhard, C. Goze, F. Denat, J. Barbe and S. Fukuzumi, J.
Phys. Chem. A., 2012, 116, 3889−3898; (b) V. Bandi, K. Ohkubo, S.
Fukuzumi and F. D’Souza, Chem. Commun., 2013, 49, 2867−2869;
(c) R. Voloshchuk, D. T. Gryko, M. Chotkowski, A. I. Ciuciu and L.
8840–8846.
44 (a) T. Cheng, T. Wang, W. Zhu, X. Chen, Y. Yang, Y. Xu and X. Qian,
Org. Lett., 2011, 13, 3656–3659; (b) B. Wang, P. Li, F. Yu, P. Song,
X. Sun, S. Yang, Z. Lou and K. Han, Chem. Commun., 2013, 49,
1014–1016, (c) G. K. Vegesna, S. R. Sripathi, J. Zhang, S. Zhu, W.
He, F.-T. Luo, W. J. Jahng, M. Frost and H. Liu, ACS Appl. Mater.
Interfaces, 2013, 5, 4107−4112.
100
40
45
50
Flamigni, Chem. Eur. J., 2012, 18, 14845−14859.
27 (a) C. Wan, A. Burghart, J. Chen, F. Bergstrōm, L. Johansson, M. F.
Wolford, T. GyumKim, M R. Topp, R. M. Hochstrasser and K.
Burgess, Chem. Eur. J., 2003, 9, 4430–4441; (b) R. Bandichhor, A. D.
Petrescu, A. Vespa, A. B. Kier, F. Schroeder and K. Burgess, J. Am.
Chem. Soc., 2006, 128, 10688−10689; (c) G.-S. Jiao, L. H. Thoresen,
T. G. Kim, W. C. Haaland, F. Gao, M. R. Topp, R. M. Hochstrasser,
M. L. Metzker and K. Burgess, Chem. Eur. J., 2006, 12, 7816–7826.
45 A. Palma, M. Tasior, D. O. Frimannsson, T. T. Vu, R. Méallet-Renault
105
and D. F. O’Shea, Org. Lett., 2009, 11, 3638–3641.
46 M. Baruah, W. Qin, C. Flors, J. Hofkens, R. A. L. Vallée, D. Beljonne,
M. V. Auweraer, W. M. D. Borggraeve and N. Boens, J. Phys. Chem.
A, 2006, 110, 5998–6009.
28 (a) A. Coskun and E. U. Akkaya, J. Am. Chem. Soc., 2006, 128,
14474–14475; (b) S. Kolemen, O. A. Bozdemir, Y. Cakmak, G. Barin,
S. Erten-Ela, M. Marszalek, J.-H. Yum, S. M. Zakeeruddin, M. K.
Nazeeruddin, M. Grätzelc and E. U. Akkaya, Chem. Sci., 2011, 2,
949–954.
47 J. Shao, H. Guo, S. Ji and J. Zhao, Biosens. Bioelectron., 2011, 26,
110
3012–3017.
48 S. Duman, Y. Cakmak, S. Kolemen, E. U. Akkaya and Y. Dede, J.
Org. Chem., 2012, 77, 4516−4527.
29 (a) X. Zhang, Y. Xiao and X. Qian, Org.Lett., 2008, 10, 29–32; (b) M.
Yuan, X. Yin, H. Zheng, C. Ouyang, Z. Zuo, H. Liu and Y. Li, Chem.
Asian J., 2009, 4, 707–713; (c) H.-Y. Shiu, M.-K. Wong, C.-M. Che,
Chem. Commun., 2011, 47, 4367–4369; (d) G. Chen, F. Song, J.
Wang, Z. Yang, S. Sun, J. Fan, X. Qiang, X. Wang, B. Dou, X. Peng.
Chem. Commun., 2012, 48, 2949–2951; (e) X. Zhang, J. Yu, Y. Rong,
F. Ye, D. T. Chiu, K. Uvdal. Chem. Sci., 2013, 4, 2143–2151; (f) M.
Suresh, A. K. Mandal, E. Suresh, A. Das. Chem. Sci., 2013, 4, 2380–
2386; (g) M.-C. Hsieh, C.-H. Chien, C.-C. Chang, T.-C. Chang, J.
Mater. Chem. B, 2013, 1, 2350–2357.
49 S. G. Awuah, J. Polreis, V. Biradar and Y. You, Org. Lett., 2011, 13,
3884–3887.
55
60
115 50 H. Yu, Y. Xiao, H. Guo and X. Qian, Chem. Eur. J., 2011, 17, 3179–
3191.
51 Y. Du, L. Jiang, J. Zhou, G. Qi, X. Li and Y. Yang, Org. Lett., 2012,
14, 3052–3055.
52 V. A. Azov, A. Schlegel and F. Diederich, Angew. Chem. Int. Ed.,
120
2005, 44, 4635–4638.
30 (a) F. Puntoriero, F. Nastasi, S. Campagna, T. Bura and R. Ziessel,
Chem. Eur. J., 2010, 16, 8832–8845; (b) T. Bura, F. Nastasi, F.
53 O. A. Bozdemir, M. D. Yilmaz, O. Buyukcakir, A. Siemiarczuk, M.
Tutasd and E. U. Akkaya, New J. Chem., 2010, 34, 151–155.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 11

Chemical Science
Page 12 of 12
54 S. Acikgoz, G. Aktas, M. N. Inci, H. Altin and A. Sanyal, J. Phys.
Chem. B, 2010, 114, 10954–10960.
View Article Online
DOI: 10.1039/C3SC52323C
55 W. Wu, J. Zhao, J. Sun and S. Guo, J. Org. Chem., 2012, 77,
5305−5312.
5 56 K. Hanson, A. Tamayo, V. V. Diev, M. T. Whited, P. I. Djurovich and
M. E. Thompson, Inorg. Chem., 2010, 49, 6077–6084.
57 (a) C. Adamo and D. Jacquemin, Chem. Soc. Rev., 2013, 42, 845–56.
(b) A. D. Quartarolo, N. Russo and E. Sicilia, Chem. Eur. J., 2006, 12,
6797–6803; (c) D. Kand, P. K. Mishra, T. Saha, M. Lahiri and P.
10
Talukdar, Analyst, 2012, 137, 3921–3924; (d) H. Guo, Y. Jing, X.
Yuan, S. Ji, J. Zhao, X. Li and Y. Kan; Org. Biomol. Chem., 2011, 9,
3844–3853; (e) J. Shao, H. Sun, H. Guo, S. Ji, J. Zhao, W. Wu, X.
Yuan, C. Zhang and T. D. James, Chem. Sci., 2012, 3, 1049–1061.
58 J. Benites, J. A. Valderrama, K. Bettega, R. C. Pedrosa, P. B. Calderon
15
and J. Verrax, E. J. Med. Chem., 2010, 45, 6052–6057.
59 L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura and F. Barigelletti,
Top. Curr. Chem., 2007, 281, 143–203.
60 R Schmidt and E Afshari, J. Phys. Chem., 1990, 94, 4377–4378.
61 Gaussian 09, Revision A.1, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P.
Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A.
Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E.
Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand,
K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi,
M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V.
Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O.
Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L.
Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J.
J. Dannenberg, S. Dapprich, A. D. Daniels, Farkas, J. B. Foresman, J.
V. Ortiz, J. Cioslowski and D. J. Fox, Gaussian, Inc., Wallingford CT,
2009.
20
25
30
35
12
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Journal Name, [year], [vol], 00–00
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