N-Bridged Annulated BODIPYs: Synthesis of Highly Fluorescent Blueshifted Dyes

Article abstract of DOI:10.1002/asia.201700584

A series of novel BODIPY dyes has been prepared through the introduction of an N-bridged annulated meso-phenyl ring at one of the β-positions of the BODIPY core. An unusual blueshift of the main spectral bands is observed, since the fusion of a meso-substituent results in a marked relative destabilization of the LUMO. The greater rigidity of the ring-fused structure leads to very high fluorescence quantum yields. The position of the main spectral bands can be fine-tuned by introducing electron withdrawing and donating groups onto the meso-phenyl ring.

Full text of DOI:10.1002/asia.201700584

CHEMISTRY
AN ASIAN JOURNAL
www.chemasianj.org
Accepted Article
Title: N-Bridged Annulated BODIPYs: Synthesis of Highly Fluorescent
Blue-shifted Dyes
Authors: Hua Lu, Yanping Wu, John Mack, XuQiong Xiao, Zhifang Li,
and Zhen Shen
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Asian J. 10.1002/asia.201700584
Link to VoR: http://dx.doi.org/10.1002/asia.201700584
A Journal of
A sister journal of Angewandte Chemie
and Chemistry – A European Journal

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
N-Bridged Annulated BODIPYs: Synthesis of Highly Fluorescent
Blue-shifted Dyes
Yanping Wu, John Mack, Hua Lu,* Xuqiong Xiao, Zhifang Li, and Zhen Shen
Abstract: A series of novel BODIPY dyes has been prepared
through the introduction of an N-bridged annulated meso-phenyl ring
at one of the -positions of the BODIPY core. An unusual blue shift
of the main spectral bands is observed,since the fusion of a meso-
substituent results in a marked relative destabilization of the LUMO.
The greater rigidity of the ring-fused structure leads to very high
fluorescence quantum yields. The position of the main spectral
bands can be fine-tuned by introducing electron withdrawing and
donating groups onto the meso-phenyl ring.
region, only a few meso-heteroatom substituted BODIPYs
have exhibited a hypsochromic shift of the main spectral
bands so that blue region emission is observed.[7] Core-
modification is another strategy that has been used to form
difluoroboron complexes which exhibit blue region emission,
but this type of dye does not retain the conventional
BODIPY core, which causes the favorable photophysical
properties of this family of dyes.[8] Herein, we report the
synthesis of a series of novel meso, β-annulated N-bridged
BODIPY dyes, which exhibit highly unusual spectroscopic
properties that can be readily rationalized through a
comparison of spectroscopic data with the results of
theoretical calculations.
Boron dipyrromethene (BODIPY) dyes are a well-known
class of fluorophores, that have been widely used as laser
dyes, fluorescent labels in fluorescence imaging and
indicator dyes in sensor applications in recent decades.[1]
In recent years, the number of papers published on the
synthesis and properties of these dyes has been rapidly
growing. The key advantages offered by BODIPYs are
their high photostabilities and advantageous spectroscopic
properties, as well as their facile synthesis and structural
versatility.[2] Most of the recent research on BODIPYs has
focused on structural modifications that result in red-shifts
of the absorption and emission band maxima, such as, 1)
aryl, ethynylaryl and styryl substitution at the 1-, 3-, 5-,
and/or 7-positions, 2) aromatic ring fusion, 3) replacing the
meso-carbon atom with an aza-nitrogen atom to form an
aza-BODIPY dye, or combinations thereof,[3] and
dimerization.[4]
The fusion of polycyclic aromatic compounds to the meso-
and β-positions of BODIPY provides another more rarely
used strategy for shifting the main spectral bands to the far-
red of the visible region and the near infrared (NIR).[5]
Reports on this type of structural modifications are relatively
few in number and have involved only the use of Se and Te
bridging atoms, which have red-shifted spectral bands.[6]
To the best of our knowledge, the introduction of an N-
bridging atom at one of the β-positions has not been
reported previously. Although it is well known that the
wavelengths of the band maxima of the absorption and
fluorescence bands can be fine-tuned so that they lie
anywhere from the green region of the visible to the NIR
Scheme 1. Synthesis and molecular structures of a series of meso, β-
annulated N-bridged BODIPYs. Reagents and conditions: I) TFA, CH2Cl2, rt, 1
h; II) DDQ, rt, 30 min; III) Et3N, BF3∙Et2O, rt, 30 min; IV) PPh3, o-DCB, 150°C,
24 h.
Precursors 1a-f were prepared through the TFA-
catalyzed
condensation
reaction
of
ortho-nitro-
benzaldehyde with pyrrole, oxidized dipyrromethanes with
DDQ, and complexed with BF3 under base condition. The
ortho-nitro group on the meso-phenyl substituent has been
used to form a C−N bond via an intramolecular reductive
cyclization approach that is referred to as a Cadogan
reaction.[9] The N-bridged meso-annulated BODIPYs were
isolated in overall yields of 26−50%. All of the target
compounds were unambiguously characterized by high-
resolution mass spectrometry, 1H and 13C NMR
spectroscopy.
Single-crystal X-ray structures were obtained for 2a, 2c, 2d
and 2f (Figure. 1). Conventional BODIPY dyes typically contain
a planar indacene plane. When substituents are introduced at
the neighboring 1,7-positions, the meso-aryl ring lies in a near
orthogonal manner to the BODIPY core. In contrast, the
structures of 2c, 2d and 2f have near planar conformations
because the meso-phenyl ring is annulated at one of the β-
positions of the fluorophore core. The average root-mean-
square (rms) deviations are 0.0241, 0.0358 and 0.0546 Å for 2c,
[a]
Y. Wu, Dr. H. Lu, Dr. X. Xiao, Dr. Prof. Z. Li,
Key Laboratory of Organosilicon Chemistry and Material
Technology, Ministry of Education, Hangzhou Normal University,
Hangzhou, 311121, P. R. China,
E-mail: hualu@hznu.edu.cn
[b]
[c]
Dr. J. Mack,
Department of Chemistry, Rhodes University, Grahamstown 6140,
South Africa.,
Dr. Prof. Z. Shen,
State Key Laboratory of Coordination Chemistry, Nanjing National
Laboratoryof Microstructures, Nanjing University, Nanjing, 210093,
P. R China.,
Supporting information for this article is given via a link at the end
of the document.
This article is protected by copyright. All rights reserved.

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
2d and 2f, respectively (Figure. 1). 2a adopts a slightly distorted
conformation, since the pyrrole ring deviates from the mean
plane (phenyl-pyridyl pyrrole rings) with an average dihedral
angle of 8.5°, due to crystal packing effects caused by co-
crystallization with triphenylphosphine oxide that is formed by
the oxidation of triphenylphosphine during the ring fusion
reaction (Scheme 1). In all four structures, the B–N2 bond is
slightly longer than the B–N1 bond due to the molecular
asymmetry. The N3–C3 and N3–C4 bond lengths lie in the
1.34−1.36 Å range, which is consistent with the values for a
double bond and an intervening single bond, which has some
double bond character.
F2···H16–C16, O1···H18–C18, and C–H···π interactions (Figure
S1 in the Supporting Information).
Figure 2. Absorption and emission spectra of BODIPYs 2a-f in DCM, (λ
=
ex
430 nm).
The photophysical properties of 2a-f were studied in toluene,
dichloromethane, THF and acetonitrile to obtain detailed
information about the effect of structures that are
conformationally locked through meso-phenyl substitution at the
β-positions, Table S1. As shown in Figure 2, in dichloromethane,
the incorporation of an N-bridged annulated meso-phenyl ring
results in a blue-shift of the absorption and emission band
relative to those of conventional BODIPY dyes. Broadening of
the main absorption band, which can be assigned as the main
electronic band of the S0–S1 transition, is observed. The
changes to the electronic structure that result in the observed
blue shift have no effect on the morphology of the absorption
band. A shoulder observed at shorter wavelength can be
ascribed to a 0–1 vibrational band in a similar manner to the
spectra of conventional BODIPY dyes.[3] Broader and much
weaker bands are observed in the UV region, which can be
attributed to transitions to the S2 or S3 excited states (Figure 3).
Although no emission is observed in the solid state, it should be
noted that similar UV-visible absorption properties were
observed for 2c in poly(methyl methacrylate) (PMMA) thin films
(Supporting information, Figure S8).
Figure 1. X-ray crystal structures of 2a (top, left), 2c (top, right), 2d (bottom,
left) and 2f (bottom, right). Both the top view and a perspective along the y-
axis that runs through the boron and meso-carbon atoms. The thermal
ellipsoids are scaled to the 30% probability level. Hydrogen atoms and solvent
molecule are omitted for clarity in both views. Selected bond lengths (Å):
B1−N1 1.537(3), B1−N2 1.548(2), C3−N3 1.346(2), C4−N3 1.372(2) for 2a.
B1−N1 1.523(7), B1−N2 1.534(6), C3−N3 1.340(5), C4−N3 1.367(5) for 2c.
(Å): B1−N1 1.534(3), B1−N2 1.545(3), C3−N3 1.350(3), C4−N3 1.363(2), C13-
Cl1 1.730(2) for 2d. B1−N1 1.531(3), B1−N2 1.547(3), C3−N3 1.343(2),
C4−N3 1.369(2), C13-O1 1.356(2) for 2f.
Intermolecular π–π interactions are observed with distances
of 3.654, 3.647 and 3.747 Å for 2a, 2c and 2f, respectively. In
addition to these interactions, multiple short interatomic contacts
are found within the crystal structures of 2c and 2f. These are
not observed in the case of 2d, since a solvent molecule lies
between neighboring π-chromophores. Short intermolecular
interactions with the solvent are still observed, however, such as
The effect of introducing different substituents on the
N-bridged fused meso-phenyl ring has been investigated.
The introduction of an electron donating methoxy group at
the para-position of the meso-phenyl ring to form 2f results
in a blue shift of 18 nm for the main spectral band relative to
the analogous band of 2a in toluene. The observed
This article is protected by copyright. All rights reserved.

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
angular nodal patterns of the HOMOs and LUMOs of selected meso-annulated
BODIPYs and the parent meso-phenyl-BODIPY model compound 3. The
HOMO−LUMO gap values are highlighted with red diamonds and are plotted
against a secondary axis. Calculations were performed at the CAM-B3LYP/6-
31G(d) level of theory in an acetonitrile solvation environment.
absorption band maxima of 2a-f depend on the polarity of
the solvent, with a hypsochromic shift of ca. 17 nm when
the solvent polarity changes on moving from the relatively
non-polar toluene to more highly polar acetonitrile.
A
similar trend is observed in the emission band maxima
(Table S1 in the Supporting Information).
Table 2 provides the predicted trends in the lowest-
energy transitions for 2a-f, and the deprotonated species.
A marked blue-shift is predicted for the main spectral bands
Table 1. Spectroscopic properties of 2a-2f in dichloromethane at 298K.
b
c
e
Δνa
ΦF
τF
krd
knr
of 2a-f relative to that of the parent meso-phenyl-BODIPY
Figure 3 shows key trends associated with the frontier
molecular orbitals of 2a 2c and 2f and the parent meso-
3.
abs
em
nm
nm
cm‒1
ns
108 s‒1
108 s‒1
2a
2b
2c
2d
2e
2f
458
464
467
478
486
488
914
975
921
0.99
0.82
0.87
4.71
4.90
5.00
2.10
1.67
1.74
0.02
0.37
0.26
,
phenyl-BODIPY
frontier orbitals of 2a
of
entire chromophore.
destabilization of LUMO and HOMO relative to the
analogous MOs of . There is a greater destabilization of
3
.
The angular nodal patterns of the
,
2c and 2f differ markedly from those
461
462
446
485
486
471
1074
1069
1190
0.99
0.98
0.99
5.11
6.24
5.81
1.94
1.57
1.70
0.02
0.03
0.02
3
, and there are significant MO coefficients across the
This results in significant
a
[a] Stokes-shift. [b] fluorescence quantum yield. [c] fluorescence half-
lifetime. [d] radiative rate constant. [e] non-radiative rate constant.
3
the LUMO, since the LUMO has a large MO coefficient at
the meso-carbon, which is the point of attachment for the
fused pyridine ring that is introduced, but this atom lies on a
nodal plane in the HOMO. This means that there is an
increase in the magnitude of the HOMO−LUMO gap (Figure
3), and hence there is a blue-shift of the absorption band
In all of the solvents investigated, the fluorescence
quantum yields of 2a-f are relatively high, in a similar
manner to classical BODIPY dyes,3 with values as high as
1.00 in non-polar toluene. This is probably related to the
enhanced structural rigidity that is introduced when a meso-
phenyl ring is fused at one of the neighboring β-pyrrole
positions of the BODIPY core. The fluorescence decay
profiles of 2a-f could be described with a single-exponential
fit with fluorescence lifetimes in the 4.40–6.75 ns range in
all of the solvents investigated. Only minor solvatokinetic
effects are observed in the rate of decay constants. As
expected, the non-radiative decay constants are very small
and significantly lower than those that have been reported
previously for non-bridged BODIPY.[10]
wavelength relative to that of
since most other structural modifications that have been
reported for BODIPYs tend to result in relative
3 (Table 2). This is unusual,
a
destabilization of the HOMO or stabilization of the LUMO
and hence in a narrowing of the HOMO−LUMO gap.[3] The
fine tuning of the max values through changes to the meso-
aryl ring can also be readily explained. The introduction of
an electron donating methoxy group to form 2f further
destabilizes the LUMO relative to 2a, since there is a large
MO coefficient at the para-position of the meso-phenyl ring.
In contrast, there is almost no effect on the HOMO because
the methoxy group is attached at an angular nodal plane.
In order to investigate the influence of structural
modifications on the spectroscopic and electronic properties,
density functional theory (DFT) was used to carry out
ground-state geometry optimizations by using the B3LYP
functional and 6-31G(d) basis sets of the Gaussian 09
Table 2. Calculated excited wavelength (
the related wave functions of meso-annulated BODIPYs 2a-f and the
parent meso-phenyl-BODIPY model compound in acetonitrile
), oscillator strengths () and
software package,[11] for 2a-f and for
a
series of
deprotonated species. The polarized continuum model
(PCM) was used to provide an acetonitrile solvation
environment. The CAM-B3LYP functional was preferred for
use in time-dependent density functional theory (TD-DFT)
calculations, since it contains a long range correction that
provides more accurate results for transitions with charge
transfer character.[12]
3
calculated by using the CAM-B3LYP functional with 6-31G(d) basis sets
and the PCM.
State[a]

cal [nm][b]

exp [nm][c]
 [d]
Wavefunction [e]
neutral BODIPY compounds
3
S1
S1
S1
S1
S1
S1
S1
410
390
396
397
393
397
386
503[3]
451
457
460
454
456
439
0.51
0.48
0.47
0.46
0.48
0.45
0.48
H  L (95%)
H  L (97%)
H  L (97%)
H  L (97%)
H  L (97%)
H  L (97%)
H  L (97%)
2a
2b
2c
2d
2e
2f
deprotonated anion species
2a
2b
2c
2d
2e
2f
S1
S1
S1
S1
S1
S1
370
371
376
376
377
367
---
---
---
---
---
---
0.36
0.34
0.33
0.34
0.33
0.36
H  L (96%)
H  L (96%)
H  L (96%)
H  L (96%)
H  L (96%)
H  L (96%)
[a] Excited state. [b] Calculated absorption wavelength in acetonitrile. [c]
Experimental absorption wavelength in toluene. [d] Oscillator strength. [e] MOs
involved in the transitions, H = HOMO, L = LUMO.
The pH dependence properties of the absorption and
fluorescence bands were analyzed through the sequential
Figure 3. Partial molecular orbital energy diagram showing the energies and
This article is protected by copyright. All rights reserved.

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
Scheme 2. The structure change of fluorophore after addition of TEA and TFA.
addition of Et3N (TEA) to a MeCN solution of 2a (Figure 4).
Upon addition of TEA, new bands are observed at 420 and
350 nm in the absorption spectrum, and there is a marked
decrease of the intensity at 451 nm. An isosbestic point is
observed at 425 nm, which is consistent with the
quantitative formation of a deprotonated species. In a
similar manner, there is a stepwise blue shift of the
emission band at 472 nm along with a decrease in intensity.
A new blue-shifted emission band is observed at 437 nm,
along with an isosbestic point at 462 nm. This results in a
change in the color of the fluorescence emission from cyan
to blue (Figure 4). Upon addition of trifluoroacetic acid
(TFA), the deprotonated species recovers its original colour
and fluorescence properties. No concentration dependence
is observed in the emission spectrum of 2a (Supporting
information, Figure S9), and the same trends are observed
in the absorption spectra upon addition of increasing
concentrations of TEA to a dilute solution of 2a (1 ×10−6 M)
in MeCN (Supporting information, Figure S10), so
aggregation effects do not contribute significantly to the
observed spectral properties.
A series of novel BODIPY dyes has been synthesized
through the introduction of an N-bridged annulated meso-
phenyl ring at one of the
blue shift of the main spectral bands is observed, since the
fusion of a meso-substituent at one of the neighboring
-positions of the BODIPY core. A

-
position carbons results in a marked relative destabilization
of the LUMO and hence an increase in the HOMO−LUMO
gap. The position of the main spectral bands can be
successfully fine-tuned in the blue region by introducing
electron withdrawing and donating groups onto the meso-
phenyl ring, thus extending access for the use of the
BODIPY chromophore in applications to a wider portion of
the optical spectrum, since the favorable photophysical
properties that are typically reported for this class of dye are
retained. For example, the greater rigidity of the ring-fused
structure leads to very high fluorescence quantum yield
across a wide range of organic solvents with differing
polarity values. The pH dependence of the emission
properties due to deprotonation of the N-bridging atom
could also potentially be used to form ratiometric probes in
The spectroscopic properties can be explained based
on a comparison with the results of TD-DFT calculations,
which predict a marked blue-shift of the main spectral band
upon deprotonation of the N-bridging atom to form an
anionic species (Table 2). There is a marked blue-shift of
the main bands in the absorption and emission spectra,
non-aqueous media
.
Acknowledgements
since a phenyl-pyridyl-pyrrole fused-ring -system is formed
(Scheme 2) when the N-bridging atom is sp2 hybridized and
this results in a further relative destabilization of the LUMO.
Financial support was provided by the National Natural
Science Foundation of China (no. 21471042) to LH, the
National Research Foundation of South Africa through a
CUSR grant (uid: 93627) to JM, and a China-South Africa
joint research program (CS08-L07 and uid: 95421).
Keywords: BODIPY• Blue shift • Dyes/Pigments • Photophysical
Properties
[1] a) A. B. Descalzo, H.-J. Xu, Z. Shen and K. Rurack, Ann. N.Y. Acad. Sci.
2008, 1130, 164-171; b) A. Loudet and K. Burgess, Chem. Rev. 2007,
107, 4891-4932; c) G. Ulrich, R. Ziessel and A. Harriman, Angew. Chem.
Int. Ed. 2008, 47, 1184-1201; d) N. Boens, V. Leen and W. Dehaen,
Chem. Soc. Rev. 2012, 41, 1130-1172.
[2]
a) A. Kamkaew, S. H. Lim, H. B. Lee, L. V. Kiew, L. Y. Chung and K.
Burgess, Chem. Soc. Rev. 2013, 42, 77-88; b) T. Kowada, H. Maeda
and K. Kikuchi, Chem. Soc. Rev. 2015, 44, 4953-4972; c) H. Lu, J. Mack,
T. Nyokong, N. Kobayashi and Z. Shen, Coord. Chem. Rev. 2016, 318,
1-15.
Figure 4. Absorption and emission spectra of 2a (10−5 M) in MeCN upon
addition of increasing concentrations of Et3N (0−10 equiv). λex = 400 nm.
Pictures showing the fluorescence change that is caused by the addition of
TEA and TFA upon excitation at 365 nm using a UV lamp (bottom).
[3] H. Lu, J. Mack, Y. Yang, Z. Shen, Chem. Soc. Rev. 2014, 43, 4778-4823.
[4] a) W. Pang, X. F. Zhang, J. Zhou, C. Yu, E. Hao and L. Jiao, Chem.
Commun. 2012, 48, 5437-5439; b) A. B. Nepomnyashchii, M. Bröring, J.
Ahrens and A. J. Bard, J. Am. Chem. Soc. 2011, 133, 19498-19504; c)
M. T. Whited, N. M. Patel, S. T. Roberts, K. Allen, P. I. Djurovich, S. E.
Bradforth and M. E. Thompson, Chem. Commun., 2012, 48, 284-286; d)
Y. Hayashi, S. Yamaguchi, W. Y. Cha, D. Kim and H. Shinokubo, Org.
Lett. 2011, 13, 2992-2995; e) 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; f) X. Cui, A.
Charaf-Eddin, J. Wang, B. Le Guennic, J. Zhao and Denis Jacquemin. J.
Org. Chem. 2014, 79, 2038-204; g) A. Wakamiya, T. Murakamib and S.
Yamaguch, Chem. Sci. 2013, 4, 1002-1007.
[5] C. Jiao, K.-W. Huang and J. Wu, Org. Lett. 2011, 13, 632-635.
[6]
S. T. Manjare, J. Kim, Y. Lee and D. G. Churchill, Org. Lett. 2014, 16,
This article is protected by copyright. All rights reserved.

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
520-523.
Li, Z. Shen and H. Lu, J. Mater. Chem. C. 2016, 4, 4668-4674; f) S.
Shimizuꢀ, A. Murayama, T. Haruyama, T. Iino, S. Mori, H. Furutaꢀ and N.
Kobayashi,ꢀChem. Eur. J., 2015, 21, 12996-13003.
[7]
a) C. F. A. Gomez-Duran, I. Garcia-Moreno, A. Costela, V. Martin, R.
Sastre, J. Banuelos, F. Lopez Arbeloa, I. Lopez Arbeloa and E. Pena-
Cabrera, Chem. Commun. 2010, 46, 5103-5105; b) J. Bañuelos, V.
Martín, C. F. A. Gómez-Durán, I. J. A. Córdoba, E. Peña-Cabrera, I.
García-Moreno, Á. Costela, M. E. Pérez-Ojeda, T. Arbeloa and Í. L.
Arbeloa, Chem. Eur. J. 2011, 17, 7261-7270; c) C. A. Osorio-Martínez, A.
Urías-Benavides, C. F. A. Gómez-Durán, J. Bañuelos, I. Esnal, I. López
Arbeloa and E. Peña-Cabrera, J. Org. Chem. 2012, 77, 5434-5438; d) R.
I. Roacho, A. Metta-Magaña, M. M. Portillo, E. Peña-Cabrera and K. H.
Pannell, J. Org. Chem. 2013, 78, 4245-4250. e) M. Liras, J. Bañuelos
Prieto, M. Pintado-Sierra, F. López Arbeloa, I. García-Moreno, Á.
Costela, L. Infantes , R. Sastre and F. Amat-Guerri, Org. Lett. 2007, 9,
4183-4186.
[9]
a) P. J. Bunyan, J. I. G. Cadogan, J. Chem. Soc. 1963, 42; b) J. I. G.
Cadogan, M. Cameron-Wood, R. K. Mackie, R. J. G. Searle, J. Chem.
Soc. 1965, 4831.
[10]
a) M. Kollmannsberger, K. Rurack, U. Resch-Genger and J. Daub, J.
Phys. Chem. A. 1998, 102, 10211-10220; b) W. Qin, T. Rohand, W.
Dehaen, J. N. Clifford, K. Driesen, D. Beljonne, B. Van Averbeke, M. Van
derAuweraer, N. Boens, J. Phys. Chem. A, 2007, 111, 8588–8597; c) Z.
Shen, H. Röhr, K. Rurack, H. Uno, M. Spieles, B. Schulz, G. Reck and N.
Ono, Chem. Eur. J., 2004, 10, 4853-4871; d) K. Rurack, M.
Kollmannsberger and J. Daub, Angew. Chem., Int. Ed. 2001, 40, 385–
387.
[8]
a) H. Liu, H. Lu, J. Xu, Z. Liu, Z. Li, J. Mack and Z. Shen, Chem.
Commun. 2014, 50, 1074-1076; b) X. Wang, H. Liu, J. Cui, Y. Wu, H. Lu,
J. Lu, Z. Liu and W. He, New J. Chem. 2014, 38, 1277-1283; c) H. Liu, H.
Lu, Z. Zhou, S. Shimizu, Z. Li, N. Kobayashi and Z. Shen, Chem.
Commun. 2015, 51, 1713-1716; d) Y. Wu, H. Lu, S. Wang, Z. Li and Z.
Shen, J. Mater. Chem. C. 2015, 3, 12281-12289; e) Y. Wu, S. Wang, Z.
[11] M. J. Frisch, et al., Gaussian 09, see ESI for full reference and a detailed
description of the computational methods.
[12] Z.-L. Cai, M. J. Crossley, J. R. Reimers, R. Kobayashi, R. D. Amos, J.
Phys. Chem. B. 2006, 110, 15624-15632.
This article is protected by copyright. All rights reserved.

10.1002/asia.201700584
Chemistry - An Asian Journal
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
A series of novel meso, β-annulated
N-bridged BODIPY dyes were
designed, which exhibit an unusual
blue shift of the main spectral bands
with very high fluorescence quantum
yields.
Yanping Wu, John Mack, Hua Lu,
Xuqiong Xiao, Zhifang Li and Zhen
Shen
Page No. – Page No.
N-Bridged Annulated
BODIPYs: Synthesis of Highly
Fluorescent Blue-shifted Dyes
This article is protected by copyright. All rights reserved.