Synthesis of bis-BN-Naphthalene-Fused Oxepins and Their Photoluminescence including White-Light Emission

Article abstract of DOI:10.1021/acs.joc.9b02594

A series of novel bis-BN-naphthalene-fused oxepin derivatives were synthesized via a Pd-catalyzed tandem reaction from brominated 2,1-borazaronaphthalenes and cis-bis(boryl)alkenes. X-ray crystallographic analysis revealed that bis-BN-naphthalene-fused oxepins feature a planar framework. The electronic and photophysical properties of the novel BN-naphthalene-fused oxepins were investigated by UV-vis and fluorescence spectroscopies and density functional theory (DFT) calculations, which disclosed the distinct electronic and photophysical properties of the analogous hydrocarbon system. Interestingly, dual-fluorescent emissions were observed upon dissolving N-substituted derivatives 10-14 in dimethyl sulfoxide. Tunable emission colors especially for white-light emissions can be achieved by controlling the ratio of solvents, concentration, or temperature using only a single-molecule compound.

Full text of DOI:10.1021/acs.joc.9b02594

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Article
Synthesis of bis-BN-naphthalene-fused Oxepins and
Their Photoluminescence Including White-Light Emission
Dawei Tian, Qian Li, Yifan Zhao, Zijia Wang, Wenbin Li, Shuling
Xia, Siyang Xing, Bolin Zhu, Jianying Zhang, and Chunming Cui
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b02594 • Publication Date (Web): 20 Dec 2019
Downloaded from pubs.acs.org on December 21, 2019
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Synthesis of bis-BN-naphthalene-fused Oxepins and Their
Photoluminescence Including White-Light Emission
a
a
a
a
a
a
Dawei Tian,* Qian Li, Yifan Zhao, Zijia Wang, Wenbin Li, Shuling Xia, Siyang
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a
a
b
b
Xing,* Bolin Zhu,* Jianying Zhang, Chunming Cui*
a
Tianjin Key Laboratory of Structure and Performance for Functional Molecules,
Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry,
Ministry of Education (Tianjin Normal University), College of Chemistry, Tianjin
Normal University, Tianjin 300387, People’s Republic of China.
e-mail: hxxytdw@tjnu.edu.cn; hxxyxsy@tjnu.edu.cn; hxxyzbl@gmail.com
b
State Key Laboratory of Elemento-Organic Chemistry; Cooperative Innovation
Center of Chemical Science and Engineering (Tianjin) Nankai University, Tianjin
3
00071, China
e-mail: cmcui@nankai.edu.cn
R3
R4
R3
R3
N
R4
Pd(OAc)2 (5 mol%)
O
B
O
B
N
R4
N
K CO (4 equiv)
O
B
2
3
B
B
O
O
2
+
H2O (1 equiv)
Br
MeCN, 70 o
R1
R2
C
R1
R2
12 examples 52-87%
Bn
Bn
N
N
O
B
B
DMSO solutions with varying DCM fractions
Abstract. A series of novel bis-BN-naphthalene-fused oxepin derivatives were
synthesized via Pd-catalyzed tandem reaction from brominated
,1-borazaronaphthalenes and cis-bis(boryl)alkenes. X-ray crystallographic analysis
a
2
revealed that bis-BN-naphthalene-fused oxepins feature planar framework. The
electronic and photophysical properties of the novel BN-naphthalene-fused oxepins
were investigated by UV−vis and fluorescence spectroscopy, and DFT calculations,
which disclosed the distinct electronic and photophysical properties from the
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analogous hydrocarbon system. Interestingly, dual-fluorescent emissions were
observed upon dissolving N-substituted derivatives 10-14 in dimethyl sulfoxide.
Tunable emission colors especially for white-light emissions can be achieved by the
control the ratio of solvents, concentration or temperature using only a single
molecule compound.
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INTRODUCTION
Incorporating heteroatoms into polycyclic aromatic hydrocarbons (PAHs) has proven
to be a powerful tool to tune the properties of these functional materials.1
Boron-containing π-conjugated materials have received considerable attention in
recent years due to their unique optical and structural properties that result from the
2
vacant p-orbital of the boron center. In particular, substituting one or more C=C units
in PAHs with isoelectronic B-N units is a promising way to expanding the PAHs
family with distinctively different photophysical/chemical properties from their all
carbon analogues.3-5 The chemistry of BN-PAHs, pioneered by Dewar and
6
7
coworkers, has achieved rapid advances in the past decade. Although significant
progress has been made in azaborine chemistry, the strategies for construction of
BN-polycyclic aromatics are still quite limited and they usually rely on classical
electrophilic borylations performed under harsh conditions or require multiple steps.8
Considering the interesting supramolecular chemistry and electronic properties of
9
higher acenes, simple and efficient synthetic approach to BN heteroaromatics with
large π-conjugated skeleton is highly desirable.
Heteropin has a seven-membered 8π conjugated system including a heteroatom
(X) in the ring system. Dibenzoheteropins (Scheme 1, I) with saddle-shaped
structures are more stable than heteropins. Moreover, dibenzoheteropins such as
dibenzazepin (X = NR), dibenzoxepin (X = O), and dibenzosilepin (X = SiR ) have
2
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been investigated in the development of new organic electronic materials.10,
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Borepin, in which the 6π-electron seven-membered ring is planar and aromatic, is
another class of boron-containing heteropin. A series of annulated borepins (Scheme 1,
II) including π-expanded fused borepins that contain two borepin rings have been
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reported by the groups of Yamaguchi, Piers and Tovar. The fundamental electronic
properties, such as their intriguing fluorescence make them attractive candidates for
organic electronic materials. Recently, Yan and co-workers reported the synthesis of
planar dithienooxadiborepine (Scheme 1, III) and demonstrated that these compounds
1
3
might be used as building block for electron-accepting materials. However, in all
these cases sterically bulky groups are necessary to stabilize the electron deficient
boron center which will prevent intermolecular π–π interaction. In response to these
limitations, Yamaguchi and Piers have demonstrated that enforced planarity could
1
4
stabilize boron-containing π-conjugated materials. In addition, the incorporation of
an adjacent electron-donating atom to the boron center could further stabilize the
boron-containing π-conjugated skeleton. These strategies have been applied to the
synthesis of NBN units containing compounds.15, 16 Moreover, boronate esters have
attracted considerable attention as novel materials for sensors and supramolecular
assemblies.[17] However, because of the lack of suitable synthetic methods, polycyclic
aromatic compounds containing boronate substructures have not been well studied.18
R
B
R
R
O
X
B
B
S
S
X = O, N, SiR2
dibenzoheteropin
dibenzoborepin
dithienooxadiborepine
I
II
III
R
R
N
N
O
B
B
Ar
Ar
this work
IV
Scheme 1 Heteropins discussed in this paper.
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BN-naphthalenes, one of the smallest BN-PAHs, are excellent building blocks
for construction of large functional BN-PAHs. However, the potential of this strategy
in extending the π-conjugation and designing novel BN-polycyclic aromatics with
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improved properties is still relatively unexplored. Herein, we report the effecient
synthesis of unprecedented bis-BN-naphthalene-fused oxepins (Scheme 1, IV) via a
Pd-catalyzed tandem reaction from brominated 2,1-borazaronaphthalenes and
cis-bis(boryl)alkenes. Interestingly, some of these BN-doped π-conjugated
compounds exhibit dual-emission properties in DMSO, and white-light emission can
be generated by controlling the solvent ratio, concentration or temperature with a
single molecule. Since emission bands tend to be generated from the lowest excited
state according to Kasha's rule,20 achieving white-light emission from single
molecules with simple structures is an exciting challenge in synthetic chemistry as
well as in photochemistry and photophysics. This work not only presents a new
strategy for the construction of larger BN-doped π-conjugated compounds, but also
paves a new way for producing single molecular white-light organic compounds.
RESULTS AND DISCUSSION
As mentioned above, BN-naphthalenes are suitable building blocks to construct
large functional BN-PAHs. Molander and co-workers recently reported that
brominated N-alkyl B-aryl 2,1-borazaronaphthalenes undergo a selfarylation reaction
in the presence of a catalytic amount of palladium and base, in which
2
,1-borazaronaphthols and their respective anhydrides could be obtained.21 They
postulated that the substituent on nitrogen is necessary to weak the B-Caryl bond. We
envisioned that the bulky substituent on 3-position will play the same role as one on
nitrogen. Thus, this reaction mode can be used for constructing polycyclic aromatic
compounds containing BN and BO units in one molecule. To test our hypothesis, the
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reaction of
brominated B-phenyl-2,1-borazaronaphthalenes 1a and
cis-bis(boryl)alkene 2a was evaluated initially (Table 1, entry 1). Using Pd(OAc) (5
2
mol %) as catalyst, bis-BN-naphthalene-fused oxepin 3 was obtained in 51% yield
after heating at 70 °C for 10 h in acetonitrile. After extensive screening of catalytic
systems and reaction parameters the isolated yield of compound 3 can be increased to
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4%, and the addition of appropriate amount water in the system can significantly
improve the yield. The structure of 3 was unambiguously confirmed by X-ray single
crystal analysis .
Table 1. Optimization of Reaction Conditionsa
H
H
H
N
N
O
N
Ph
Br
Bpin
Ph
Bpin
Ph
[Pd], base
solvent, 70 o
B
B
B
2
+
C
Ph
Ph
1a
2a
3
Bpin = pinacolatoboryl
yield(%)b
entry
catalyst
base
solvent H O
time
10h
2
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Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(dba)2
PdCl2
K CO3
2
MeCN --
51%
68%
70%
38%
31%
trace
44%
37%
43%
56%
43%
57%
67%
68%
32%
61%
45%
K CO3
MeCN 1.5μL 10h
MeCN 3.0μL 10h
MeCN 0.1mL 10h
MeCN 1.0mL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
2
K CO3
2
K CO3
2
K CO3
2
K CO3
2
K CO3
2
PdCl (dppf) K CO3
2
2
Pd(PPh3)4
K CO3
2
1
1
0
1
PdCl (PPh ) K CO3
2
3 2
2
Pd(OAc)2
K CO3
2
Tol
3.0μL 10h
3.0μL 10h
3.0μL 10h
12
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
K CO3
2
THF
DMF
1
1
3
4
K CO3
2
KOH
MeCN 3.0μL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
MeCN 3.0μL 10h
15
NaOH
1
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6
Cs CO
2
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K CO3
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a
Reaction conditions: 1a (0.36 mmol), 2a (0.18 mmol), Pd(OAc) (5 mol%), base (4
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c
equiv), solvent 3 mL at 70℃ under Ar. Isolated yields. 5 equiv base was used.
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We assumed that the cross coupling reaction will occurred initially to generate
2-phenyl-3-vinyl-2,1-borazaronaphthalene species (Scheme 2, A). The bulky vinyl
substituent on the 3-position led to the phenyl groups on the boron atoms to rotate
such that it is no longer in the same plane with the azaborine, thereby weakening the
B-Cphenyl bond via decreasing the overlaps of the molecular orbitals between the
empty p-orbital on the boron atom and phenyl group. And then Pd/water/base
promoted B-Caryl cleavage with subsequent intramolecular dehydration is very likely
to take precedence. In addition, diphenyl was not found in this reaction. Trace amount
of 2,3-diphenyl-2,1-borazaronaphthalene were obtained in this tandem reaction.
H
N
Ph
Br
B
2
Ph Ph
H
H
N
N
1
a
B
B
[Pd]/H O
[Pd]/base
2
+
Bpin
Ph
BPin
Ph
- 2 C6H6
Ph
Ph
2
a
A
H
H
N
H
OH HO
H
N
N
N
O
B
B
B
B
-
H2O
Ph
Ph
Ph
Ph
B
3
Bpin = pinacolatoboryl
Scheme 2 Proposed mechanism for the formation of 3
.
Single crystals of 3 were achieved from the n-hexane/dichloromethane solution
through slowly evaporating the solvents. It shows a relatively planar main backbone
with a fully zigzag-edged periphery (Figure 1). The largest dihedral angle of 8.65°
was observed among the fused rings. Moreover, the phenyl groups on C9 and C9’
were deviated from the main backbone by 82.78°. The short B-N bond lengths of 3
(
1.414(3) Å) are consistent with those reported for BN-aromatic systems.4f, 4g, 5d In
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addition, the B-C and N-C bond lengths (B-C = 1.535(3), N-C = 1.386(2) Å) in 3 are
noticeably shorter than normal B-C (ca. 1.579(5) Å) and N-C (ca. 1.47 Å) single
2
2
bonds, consistent with the electron delocalization over the C BN core. The sum of
4
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o
the inner angles of C B O seven-membered ring is 899.99 . The B-O bond lengths
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(1.382(3) Å) are comparable to those in arylboronic acids and their esters (1.35-1.38
Å).18d Furthermore, substantial bond length alternations are observed for the
C1-C9-C9’-C1’ bonds. These observations indicated the nonaromativity of C B O
4
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ring. Many weak N-H⋅⋅⋅O intermolecular hydrogen bonds (3.684 Å) and π-π
interactions with the distances of ∼3.670 Å between the neighboring molecules can
be detected in the crystals of 3 (Figure S1).
Figure 1. Molecular structure of 3 with thermal ellipsoids set at 30% probability: top
view (left) and side view (right). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and bond angles (deg): B1−N1 1.414(3), B1−C1 1.535(3),
B1−O1 1.382(3), C1−C9 1.481(3), C9−C9’ 1.372(3); B1−O1−B1 130.6(2),
O1−B1−C1 128.2(2), B1−C1−C9 127.81(17), C1−C9−C9’ 128.72(10).
TD-DFT (RB3LYP/6-31 (d, p)) calculations were performed to investigate the
structure−property relationship of this new bis-BN-naphthalene fused oxepin. Since
the corresponding hydrocarbon analogue 3’ (Figure 2) is not known, the same level
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calculations were performed for 3’ for comparison. A significant geometry difference
can be found in 3’. The optimized structure of 3’ is saddle-shaped, while 3 represent
planar geometry, indicating the significant effects of the BN substitution (Figure S5,
Figure S6). In addition, the HOMO of 3 is 0.53 eV higher than that of 3’ and the
LUMO is 0.16 eV lower in energy (Figure 2). The plots of HOMO and LUMO
orbitals for 3 and 3’ are shown in Figure 2. Although they all are mainly
corresponding to the π orbitals of the central fused rings with negligible contributions
from the peripheral phenyl groups, the noticeable differences between the frontier
orbitals of the two compounds can be seen due to the BN substitution.
Nucleus-independent chemical shift (NICS) calculations (GIAO-B3LYP/6-311+G (d,
p)) of 3 and 3’ were performed to investigate the aromaticity of each ring (Figure 2).
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Remarkably, the aromaticity of the fused peripheral benzo group and C BN ring in 3
4
is significantly reduced in comparison to the corresponding rings in 3’. These
differences may partly due to the partially localized charge on the B
and N atoms due to the polarization of the B-N bond. Notably, the seven-membered
C B O ring in 3 indeed has a positive NICS (1) value of 3.5 ppm, supporting its
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nonaromaticity.
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Figure 2. Calculated NICS (1) values (in ppm, calculated at the
GIAO-B3LYP16-311+G (d. p) Level), and the calculated frontier orbitals and their
energy levels of 3 (up) and its hydrocarbon analogue 3’ (down).
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
The synthesis of 3 prompted us to extend this methodology for the synthesis of
the other derivatives. As shown in Table 2, both electron-donating and electron
withdrawing groups on the phenyl rings of phenyl-substituted cis-bis(boryl)alkenes
(2) were tolerated, furnishing the corresponding products in good to excellent yields.
The molecular structures of 8 has also been determined by single-crystal X-ray
analysis, and the crystal parameters are comparable to those of 3 (Figure S3, Table
S1). In contrast, cis-bis(boryl)alkenes bearing 2-thienyl or ethyl groups is not
effective and the cyclic product was not detected. In addition, N-substituted
BN-naphthalenes also work well in this reaction (10-14). Compounds 3-14 were
obtained as solids by chromatography on silica gel and could be stored in air for
1
several months without any noticeable decomposition, as determined by H NMR
1
13
11
spectra. All compounds have been characterized by H, C, B NMR and HRMS
spectroscopy. Overall, these results denominated that the tandem reaction is useful for
the synthesis of diverse BN-naphthalene fused oxepin derivatives.
Table 2. Synthesis of bis-BN-naphthalene Fused Oxepinsa
R3
R3
N
R4
R3
N
R4
Pd(OAc)2 (5 mol%)
K2CO3 (4 equiv)
R4
O
B
O
B
N
O
B
O
O
B
B
2
+
H2O (1 equiv)
Br
R1
R2
MeCN, 70 o
C
R1
R2
-15
1
a-f
2a-g
3
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1
1
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1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
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3
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5
5
5
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6
R3
R3
H
H
R4
Bn
Bn
R4
N
N
N
N
O
O
N
N
B
B
B
B
O
B
B
R1
R2
R1 = R2 = C6H5, 3 (84%)
R1 = R2 = p-MeC6H4, 4 (60%)
R1 = R2 = m-MeC6H4, 5 (52%)
R1 = R2 = p-MeOC6H4, 6 (83%)
R1 = R2 = p-FC6H4, 7 (60%)
R1 = R2 = p-ClC6H4, 8 (87%)
R3 = C6H5, 10 (69%)
R3 = Bn, 11 (78%)
R3 = nBu, 12 (63%)
R4 = F, 13 (73%)
R4 = Me, 14 (77%)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
R1 = p-CF3C6H4, R2 = p-MeOC6H4, 9 (80%)
a
Reaction conditions: 2.0 equiv of 1, 1.0 equiv of 2, 5 mol% of Pd(OAc) , 4 equiv of
2
o
K CO , 1 equiv of H O, CH CN (3 mL), 70 C, 15 h.
2
3
2
3
Double bromination of 3 can be achieved by the reaction with 2.2 equivalent of
bromine in CH Cl at 0 °C, leading to the dibromination product 15 in quantitive yield
2
2
(
Scheme
3).
The
Suzuki
cross-coupling
reaction
of
15
with
2
-(4-methoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane produced compound 16
and 17 in moderate yield (Scheme 3). It should be mentioned that 10-20 eq of
cross-coupling partners are needed for completeing the conversion. We tried to
screening conditions to generate more effective conditions but failed. The structure of
16 has been confirmed by X-ray single crystal analysis (Figure S4, Table S1). The
regioselectivity of the bromination of 3 is identical with that of 3-substituted
2
,1-borazaronaphthalenes,23 indicating the limited influence to
electronic
distribution in side BN−naphthalene ring by central nonaromatic C B O core. These
4
2
results demonstrated that the diverse BN-PAH derivatives might be accessible
following the synthetic methodologies.
H
H
H
H
N
N
N
N
O
O
B
B
B
B
Ar
Ar
Ph
Ph
Ph
Ph
rBpin
3
uiv A
eq
O3
7
C
,
o C
17 (72%)
a2
,
)4
h3
N
0
20
2
.2 equiv Br2
O
P
H2
d(P HF/
H
H
H
H
N
P
T
N
N
N
20:
1
O
O
B
B
B
B
Br
Ar
Br
Br
10 equiv ArBpin
Pd(PPh3)4, Na2CO3
0:1 THF/H2O, 70 o
C
Ph
Ph
Ph
Ph
2
1
6 (55%)
15
Ar = p-MeOC6H4
Bpin = pinacolatoboryl
Scheme 3. Bromination of 3 and subsequent cross-coupling reaction.
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The most prominent features of the bis-BN-naphthalene-fused oxepins can be
seen in their UV−vis and emission spectra (Table 3, Figure S8). The
bis-BN-naphthalene-fused oxepins 3-17 are fluorescent both in solution and in the
solid state. The absorption and luminescence maxima measured in dichloromethane
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(DCM) and in the solid state are listed in Table 3. The UV−vis spectra of 3-17 in
DCM all exhibited three structured absorption bands in the range of 372−419 nm.
These absorption maxima are significantly red-shifted compared to that reported for
2
4
dibenz[b,f]oxepin (300 nm). In addition, DFT calculation showed that the HOMO
and LUMO energy gap of 3 is 3.33 ev, which is in good agreement with the
experimentally observed one (3.32ev, 374nm). Compounds 3-17 emitted intense blue
luminescence (423−489 nm) and nearly holds mirrorimage relationship with the
absorption bands with the quantum yields (Φ ) ranging from 0.24 to 0.79. The narrow
F
fluorescence maxima ranges indicated that the substituents on the five-ring fused
system had a limited effect on their emission maxima. Compounds 3-17 are also
luminescent in the solid state. Redshifts of the emission maxima and relatively large
Stokes shifts in the solid state compared to their DCM solutions (Table 2, Figure S9)
are generally observed. The Φ of these compounds in the solid state were apparently
F
affected by the substituents on the main backbone, and relatively high Φ values (0.56,
F
0
.64) for 3 and 7 were observed.
Table 3. Absorption and Emission Data for Compounds 3−17 in DCM and in the
Solid State (in Parentheses)
Compounds λmax
λmax
ΦF
Stokes Shift
(cm-1)
(
abs, nm)a
(em, nm)b
(%)c
3
374, 390, 413
426, 451, 480 (498, 520) 79 (56)
739 (4133)
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
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9
1
1
1
374, 391, 412
374, 392, 413
374, 392, 413
374, 391, 413
374, 392, 413
374, 392, 413
380, 397, 419
378, 395, 415
378, 396, 418
372, 391, 412
381, 399, 421
380, 397, 420
380, 397, 419
385, 403, 425
428, 452 (519, 553)
427, 453, 479 (506)
433, 455 (510)
77 (13)
907 (5004)
79 (nd)[d] 794 (4450)
69 (43)
73 (64)
70 (nd)
71 (50)
68 (42)
69 (nd)
1118 (4605)
794 (4052)
794 (4567)
903 (4213)
772 (4487)
895 (4603)
668 (4238)
631 (3219)
711 (2431)
715 (2933)
983 (2858)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
427, 453, 480 (496)
427, 454, 480 (509)
429, 454 (500)
0
1
2
433, 460, 483 (516)
431, 456 (513)
430, 457, 484 (508, 516) 78 (nd)
423, 450, 477 (475, 500) 75 (28)
434, 461, 489 (469, 495) 68 (34)
433, 460, 486 (479, 508) 24 (nd)
13
1
1
4
5
16
437, 463 (476, 506)
445, 471 (478, 509)
57 (nd)
65 (5)
1
7
1058 (2609)
a
-5
b
All experiments were performed in DCM solution at 10 M.
Emission maximum upon excitation at the absorption maximum wavelengths.
-6
c
(Samples were obtained as DCM solution 10 M or grinding crystals) Absolute
quantum yield determined by a calibrated integrating sphere system within ±3%
d
errors. nd = not determined.
The absorption and fluorescence properties of 3-17 were also investigated in
toluene and negligible changes of absorption and fluorescence maxima were observed
(Figure S10). Interestingly, dual-fluorescent emissions were observed when
dissolving N-substituted derivatives 10-14 in dimethyl sulfoxide (DMSO), different
emission colors especially for white-light emissions were observed (Figure 3a). In
addition to the common emission at around 450 nm found for other derivatives, 10-14
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shows another broad emission band located at approximately 550 nm. The Φ for
F
selected compounds in DMSO were comparable to those in DCM (3: 0.68, 10: 0.66,
12: 0.69, 17: 0.73). Other solvents such as tetrahydrofuran, chloroform, dimethyl
formamide, acetone, tetramethylene sulfone were investigated, and only DMSO had
this interesting effect. We speculated that this interesting optical property originated
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
5
from the aggregates between molecules induced by DMSO. This was checked by
measuring the fluorescence dependence on the concentration of 13 (Figure 3b).
Long-wavelength emission around 530 nm decreased remarkably as the decrease of
-5
solution concentration. Using 12 as a prototype, the DMSO solution of 12 (10 M)
presents colloidal behavior, which was verified by the typical Tyndall light-scattering
effect (Figure 4a). Moreover, SEM experiments were carried out to get in detail about
morphologies of 12 in DMSO which showed square particles were formed (Figure
4b).
1.0
-
9
a)
3
3
10 11 12 13 14
10 11 12 13 14
b) 2.4
2.0
3*10
-
9
DMSO
8*10
1*10
1
0
-6
M
-8
-8
-8
-7
0
.8
.6
2
*10
DCM
10-6
5*10
1*10
M
1.6
0
-
6
1
*10
1.2
1*10-5
3
10
-4
0.4
1*10
1
12
1
0.8
0.4
0.0
13
0
.2
.0
14
0
400
500
600
700
400
500
600
700
Wavelength (nm)
Wavelength (nm)
Figure 3. a) Normalized fluorescence spectra of 3, 10-14 in DMSO solutions at 10-6
-6
M and emission pictures of 3, 10-14 in DMSO and DCM solutions (10 M). b)
Concentration-dependent emission spectra of 13 in DMSO.
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9
1
1
1
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2
2
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2
2
2
2
3
3
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3
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0
1
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3
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8
9
0
1
2
3
4
5
6
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8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
-
5
Figure 4. a) Tyndall effect of 12 in DMSO solution (10 M) irradiated with a green
laser beam igure Caption. b) SEM micrographsof 12 self-assembled microstructures
-5
deposited from DMSO solutions at 10 M.
Color-tunable emission could be conveniently achieved using the DMSO/DCM
mixed solvent. Compound 12 were selected to investigate the color-tunable emission
in mixed solvent. As shown in Figure 5a, long-wavelength emission declined with the
increasing of DCM fraction. The Commission Internationale de I’Eclairege (CIE)
color coordinate of the emission spectrum of the pure DMSO solution was calculated
to be (0.35, 0.44), which is at the greenish yellow emission region. When the fraction
of DCM was increased to 30%, luminescent color of the solution gradually turned
white. At this state, the CIE coordinate was calculated to be (0.28, 0.33), which is
very close to the coordinate (0.33, 0.33) of the standard white-light illumination. The
CIE coordinate of the emission spectrum was shifted to (0.15, 0.13), while pure DCM
was used, corresponding to the blue-emitting region in the chromaticity diagram
(
Figure 5b). Moreover, white-light emission could be achieved by other derivatives
such as 10 in pure DMSO (0.30, 0.34) and 11 in DMSO/DCM (DCM = 30%) mixed
system (0.28, 0.31) (see Figures S12 and S13).
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0
10%
%
b)
a) 1.0
2
3
0%
0%
0.8
0.6
0.4
0.2
0.0
40%
50%
100%
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
500
600
700
Wavelength (nm)
Figure 5. a) Fluorescence photographs of DMSO solutions of 12 with varying DCM
-5
fractions (10 M). b) Calculated PL emission color coordinates in the CIE 1931
chromaticity diagram.
Temperature-dependent emission properties were also observed for 12 in DMSO.
The emission was gradually turned from yellow to white as increasing temperature
o
o
from room temperature to 65 C, and then blue when rising to 100 C (see Figures
S15-18). The changes in emission color can be viewed with the naked eye. For a
deeper understanding of the intermolecular interactions, temperature dependent
1
HNMR studies for 12 were carried out in DMSO-d . Two broaden resonances at 5.11
6
o
ppm and 7.26 ppm were observed at 25 C, corresponding to the CH on the benzyl
2
groups and aromatic ring respectively (Figures S15). At increasing temperature to 65
oC, the original broaden signal at 5.11 ppm shifted slightly downfield to 5.13 ppm
with a sharper shape. Broaden signal at 7.26 ppm spited into structured triple peak
(
Figures S16). This trend is even more significant at elevated temperatures (Figures
S17). The original spectrum could be regenerated when the temperature returned to 25
oC (Figures S18). These results indicated that the driving forces for the self-assembly
process not only due to π-π stacking but also intermolecular C-H hydrogen bonding.
CONCLUSIONS
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1
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1
1
2
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2
2
2
2
2
2
2
3
3
3
3
3
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3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
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5
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5
5
5
5
6
In summary, we have succeeded in the synthesis of novel air- and moisture-stable
bis-BN-naphthalene-fused oxepins by Pd-catalyzed tandem reaction of brominated
2,1-borazaronaphthalenes with 1,2-Bis(pinacolatoboryl)alkenes, which represents a
concise and new strategy for constructing large BN-doped π-conjugated compounds.
Unlike it’s carbonaceous analogues, bis-BN-naphthalene-fused oxepins represent a
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
planar geometry. The nonaromaticity of planar C B O seven-membered ring has been
4
2
confirmed by single crystal structure analysis and DFT calculations. These
bis-BN-naphthalene-fused oxepin derivatives are luminescent in both solution and the
solid state with moderate to high quantum yields. Interestingly, dual-fluorescent
emissions were observed upon dissolving N-substituted derivatives 10-14 in DMSO,
and tunable emission colors especially white-light emission can be generated by
controlling the solvent ratio, concentration or temperature with a single molecule. We
believe that this interesting optical property originates from the aggregates between
molecules induced by DMSO.
EXPERIMENTAL SECTION
General Experimental Methods. All solvents were obtained from commercial
sources and were purified according to standard procedures. Oil bath was used as heat
source for all reactions require heating. Purification of products was accomplished by
1
13
11
19
flash chromatography using silica gel (200~300 mesh). The H, C, B and F NMR
spectra were recorded on a 400 MHz NMR spectrometer. Chemical shifts are
1
1
19
referenced against external BF · Et O ( B), and CFCl ( F). HRMS were acquired in
3
2
3
ESI mode with the TOF mass analyzer used. UV-vis absorption spectra were
determined on a Shimadzu UV-1601PC Spectrophotometer. Photoluminescence (PL)
spectra were carried out on a Shimadzu RF-5301 Luminescence Spectrometer.
Quantum yields in solutions were determined with an Edinburgh Analytical
Instruments FL900CD calibrated integrating sphere system. IR spectra were recorded
on a MAGNA-560 spectrometer made by Nicolet Company. The commercially
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available catalysts and reagents were purchased from J&K Scientific. The reaction
schemes for compounds 1, 19 and 2 can be found in the supporting information (SI).
Procedures for the Synthesis of brominated B-phenyl-2,1-borazaronaphthalenes
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
6
1a, 1b, and 1d were synthesized as described in literature. 1c, 1e, and 1f were
prepared according to the process described below. Under argon atmosphere, to a
dichloromethane solution (10 mL) of B-phenyl-2,1-borazaronaphthalenes (1.6 mmol,
1 equiv) was added a solution of Br (1.8 mmol, 1.1 equiv) in dichloromethane (10
2
o
mL) over 30 min at 0 C. After the completion of the dropwise addition, the reaction
mixture was slowly returned to room temperature. The mixture was then suction
filtered over Celite and the solvent was removed in vacuo. The product was purified
by column chromatography on silica gel with dichloromethane/hexanes (1:50).
3
-bromo-1,2-diphenyl-2,1-borazaronaphthalene (1c). 1c was obtained as a white solid
1
(
0.13 g, 51%). H NMR (400 MHz, CDCl ) δ 8.52 (s, 1H), 7.68 (dd, J = 7.8, 1.5 Hz,
3
1H), 7.37–7.29(m, 3H), 7.28–7.27 (m, 1H), 7.25–7.20 (m, 3H), 7.17–7.14 (m, 3H),
13
1
7
1
.09–7.06 (m, 2H), 6.87 (d, J = 8.5 Hz, 1H); C{ H} NMR (101 MHz, CDCl ) δ
3
46.4, 143.3, 141.9, 132.7, 129.2, 129.1, 129.0, 128.6, 127.3, 127.3, 126.8, 125.5,
－
122.1, 118.1; HRMS (ESI) Calcd for C H BBrNO [M+COOH] : 404.0457, found:
2
1
16
2
4
04.0467.
1-benzyl-3-bromo-7-fluoro-2-phenyl-2,1-borazaronaphthalene (1e). 1e was obtained
1
as a white solid (0.52 g, 83%). H NMR (400 MHz, CDCl ) δ 8.33 (s, 1H), 7.53–7.49
3
(m, 1H), 7.35–7.34(m, 2H), 7.25 (s, 2H), 7.27–7.25 (m, 2H), 7.21–7.12 (m, 4H),
1
3
1
6.96–6,85 (m, 4H), 5.17 ( m, 2H); C{ H} NMR (101 MHz, CDCl ) δ 161.9（d, J =
3
2
1
48.5 Hz), 144.8, 140.6, 140.5, 136.6, 130.6, 130.1 (d, J = 10.2 Hz), 127.9, 127.2,
26.6, 126.2, 124.6, 122.4, 109.4 (d, J = 23.7 Hz), 103.1 (d, J = 26.4 Hz), 52.8;
－
HRMS (ESI) Calcd for C H BBrNFO [M+COOH] : 436.0520, found: 436.0527.
2
2
17
2
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6
1
-benzyl-3-bromo-7-methyl-2-phenyl-2,1-borazaronaphthalene (1f). 1f was obtained
1
as a white solid (1.89 g, 92%). H NMR (400 MHz, CDCl ) δ 8.34 (s, 1H), 7.44 (d, J
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
=
7.9 Hz, 1H), 7.35–7.33 (m, 1H), 7.26–7.24 (m, 2H), 7.20–7.10 (m, 4H), 7.04 (s, 1H),
1
3
1
6
1
1
.98–6.94 (m, 3H), 5.21 (s, 2H), 2.22 (s, 3H); C{ H} NMR (101 MHz, CDCl ) δ
3
46.2, 140.3, 139.3, 138.6, 131.7, 129.5, 128.8, 128.0, 127.6, 126.9, 125.7, 124.6,
－
23.5, 117.5, 53.4, 22.3; HRMS (ESI) Calcd for C H BBrNO [M+COOH]
:
2
3
20
2
4
32.0770, found: 432.0762.
Procedures
for
the
Synthesis
of
1
-benzyl-2-phenyl-7-fluoro-2,1-Borazaronaphthalene (19)
To a toluene solution (40 mL) of allylpalladium(II) chloride dimer (37 mg, 0.1
mmol), JohnPhos (60 mg, 0.2 mmol) and t-BuONa (3.7 g, 39 mmol) was added
2
-Bromo-4-fluoro-1-vinylbenzene (3.9 g, 19.5 mmol) and benzylamine (2.5 g, 23.4
o
mmol). The resulting mixture was heated to 100 C for 12 hours. The reaction mixture
was cooled, diluted with Et O (30 mL), and filtered over Celite. The solvent was
2
removed in vacuo and the product was purified by flash column chromatography on
silica gel with dichloromethane/hexanes (1:10). The product 18 was obtained as a
yellow oil (3.42 g, 77%).
1
N-benzyl-5-fluoro-2-vinylaniline (18). H NMR (400 MHz, CDCl ) δ 7.44–7.36 (m,
3
5
H), 7.30–7.26 (m, 1H), 6.78–6.71(m, 1H), 6.51–6.47 (m, 1H), 6.40 (d, J = 11.6 Hz,
1
3
1
1H), 5.64 (d, J = 17.3 Hz, 1H), 5.35 (d, J = 10.9 Hz, 1H), 4.36 (s, 3H); C{ H} NMR
(101 MHz, CDCl ) δ 164.0 (d, J = 243.7 Hz), 146.7 (d, J = 10.7 Hz), 138.6, 132.1,
3
1
28.9, 128.7 (d, J = 10.1 Hz), 127.6, 120.3 (d, J = 2.0 Hz), 116.3, 103.9 (d, J = 21.8
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+
Hz), 98.3 (d, J = 26.3 Hz), 48.3; HRMS (ESI) Calcd for C H FN [M+H] : 228.1189,
1
5
15
found: 228.1189.
To an oven-dried Schlenk bottle with a stir bar was added 18 (8.8 mmol, 1.0
1
1
1
1
1
1
1
1
1
1
2
2
2
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3
3
3
3
4
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4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
equiv), and purged with Ar three times. CPME (20 mL) and toluene (20 mL) were
added, followed by the PhBF K (13.2 mmol, 1.5 equiv ) and SiCl (8.8 mmol, 1.0
3
4
equiv) under Ar. The resulting mixture was heated to 80 °C for 16 hours , and then
cooled to room temperature and diluted with hexanes (35 mL). The reaction mixture
was filtered over Celite and removed in vacuo. The product was purified by column
chromatography on silica gel with dichloromethane/hexanes (1:30). 19 was obtained
as a white solid (1.10 g, 40%).
1
-benzyl-7-fluoro-2-phenyl-2,1-borazaronaphthalene (19). 1H NMR (400 MHz,
CDCl ) δ 8.10 (d, J = 11.4 Hz, 1H), 7.69–7.65 (m, 1H), 7.56–7.53 (m, 2H), 7.36–7.31
3
13
1
(
m, 5H), 7.28–7.26 (m, 1H), 7.15–6.92 (m, 5H), 5.40 (s, 2H); C{ H} NMR (101
MHz, CDCl ) δ 162.9 (d, J = 245.9 Hz), 144.8, 142.6 (d, J = 10.4 Hz), 138.5, 132.5,
3
1
31.7 (d, J = 10.2 Hz), 128.9, 128.2, 127.8, 127.1, 125.7, 124.0 (d, J = 1.8 Hz), 109.4
(
[
d, J =22.9 Hz), 103.8 (d, J = 25.0 Hz), 52.7; HRMS (ESI) Calcd for C H BFNO
2
2
18
2
-
M+COOH] : 358.1415, found: 358.1411.
Procedures for the Synthesis of cis-Bis(boryl)alkenes
27
2
a, 2b, 2d, and 2g were synthesized as described in literature. 2c, 2e, and 2f
were prepared according to the process described below. To a degassed solution of
alkyne (1.0 mmol, 1.1equiv) and bis(pinacolato)diboron (0.9 mmol, 1.0 equiv) in
DMF (5 mL) was added Pt(PPh ) (2.0 mol%). The reaction mixture was heated to 80
3
4
oC for 24 hours. After this time, the reaction was washed with saturated aqueous
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2
2
2
2
2
2
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5
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6
NH Cl, and the aqueous phase is extracted with diethyl ether. The organic phase was
4
dried over MgSO and concentrated under reduced pressure to give the crude products,
4
which were purified by recrystallisation from ethanol.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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0
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2
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4
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6
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8
9
0
(Z)-1,2-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2-di-m-tolylethene (2c). 2c
1
was obtained as a white solid (319 mg, 79%). H NMR (400 MHz, CDCl ) δ 6.94 (t, J
3
=
7.6 Hz, 2H), 6.83 (d, J = 7.5 Hz, 2H), 6.77 (s, 2H), 6.72 (d, J = 7.6 Hz, 2H), 2.14 (s,
1
3
1
6
H), 1.32 (s, 24H); C{ H} NMR (101 MHz, CDCl ) δ 141.2, 136.6, 130.0, 127.2,
3
+
1
26.5, 126.3, 84.0, 24.9, 21.4; HRMS (ESI) Calcd for C H B O [M+H] : 461.3034,
2
8
39
2
4
found: 461.3040.
(Z)-1,2-bis(4-fluorophenyl)-1,2-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)ethan
1
e (2e). 2e was obtained as a white solid (535 mg, 88%). H NMR (400 MHz, CDCl3)
1
3
1
δ 6.89 (dd, J = 8.8, 5.6 Hz, 4H), 6.79 (t, J = 8.8 Hz, 4H), 1.32 (s, 24H); C{ H} NMR
(101 MHz, CDCl ) δ 161.2 (d, J = 245.0 Hz), 136.9 (d, J = 3.4 Hz), 130.8 (d, J = 7.8
3
Hz), 114.5 (d, J = 21.2 Hz), 84.2, 24.9; HRMS (ESI) Calcd for C H B F O
6
2
7
33
2
2
－
[
M+COOH] : 513.2431, found: 513.2429.
(Z)-1,2-bis(4-chlorophenyl)-1,2-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)ethen
1
e (2f). 2f was obtained as a white solid (413 mg, 75%). H NMR (400 MHz, CDCl ) δ
3
1
3
1
7
.08–7.06 (m, 4H), 6.88 – 6.85 (m, 4H), 1.31 (s, 24H); C{ H} NMR (101 MHz,
CDCl ) δ 139.3, 131.9, 130.6, 128.0, 84.3, 24.9; HRMS (ESI) Calcd for
3
-
C H B Cl O [M+COOH] : 545.1840, found: 545.1835.
2
7
33
2
2
6
Typical Procedures for the Synthesis of Compound 3-14.
Under argon atmosphere, to an acetonitrile solution (3 mL) of 1 (0.36 mmol, 2.0
equiv), 2 (0.18 mmol, 1.0 equiv), and Pd(OAc) (5 mol%) was added K CO (0.72
2
2
3
mmol, 4.0 equiv) and water (0.18 mmol, 1.0 equiv). The resulting mixture was heated
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o
to 70 C for 15 hours. After completion of the reaction, the mixture was diluted with
dichloromethane and washed twice with water. The aqueous phase was extracted with
DCM, dried over MgSO , filtered and evaporated in vacuo. The residue was purified
4
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
by flash column chromatography on silica gel (dichloromethane/hexanes, 1:3).
1
3,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (3). 3 was obtained as a
o
11
1
yellow soild in 84% (68 mg). M.p.: > 300 C; B NMR (128 MHz, CDCl ) δ 30.4; H
3
NMR (400 MHz, CDCl ) δ 7.23 (d, J = 7.8 Hz, 2H), 7.13–7.09 (m, 8H), 7.02–6.88 (m,
3
1
3
1
1
1
2H); C{ H} NMR (101 MHz, CDCl ) δ 147.8, 145.0, 144.0, 140.2, 130.8, 130.1,
3
28.6, 127.5, 125.3, 123.9, 120.0, 116.0; HRMS (ESI) Calcd for C H B N NaO
30 22
2
2
+
[M+Na] : 471.1816, found: 471.1820; IR (neat): v = 596, 659, 703, 755, 804, 1025,
095, 1153, 1181, 1229, 1266, 1334, 1425, 1538, 1603, 2962, 3048, 3388 cm-1.
1
1
3,14-di-p-tolyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (4). 4 was obtained as a
o
11
yellow soild in 60% (52 mg). M.p.: 269–271 C; B NMR (128 MHz, CDCl ) δ 30.9;
3
1
H NMR (400 MHz, CDCl ) δ 7.25–7.20 (m, 2H), 7.14 (d, J = 7.4 Hz, 2H), 7.09 (s,
3
2
6
1
H), 6.99 (d, J = 8.0 Hz, 2H), 6.92–6.87 (m, 8H), 6.81 (d, J = 8.0 Hz, 4H), 2.23 (s,
1
3
1
H); C{ H} NMR (101 MHz, (CD ) SO) δ 146.7, 143.3, 141.0, 140.9, 133.7, 130.2,
3 2
29.2, 128.5, 128.1, 123.0, 119.6, 116.6, 20.7; HRMS (ESI) Calcd for C H B N O
3
2
26
2
2
+
[
M] : 476.2231, found: 476.2236; IR (neat): v = 598, 656, 705, 749, 814, 1107, 1180,
-1
1
228, 1268, 1296, 1336, 1426, 1538, 1608, 2369, 3394 cm .
13,14-di-m-tolyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (5). 5 was obtained as a
o
11
yellow soild in 52% (45 mg). M.p.: 231–233 C; B NMR (128 MHz, CDCl ) δ 30.6;
3
1
H NMR (400 MHz, CDCl ) δ 7.26–7.22 (m, 2H), 7.16 (d, J = 6.2 Hz, 4H), 7.01–6.97
3
(m, 4H), 6.92–6.88 (m, 4H), 6.80 (d, J = 7.6 Hz, 2H), 6.74 (d, J = 8.8 Hz, 4H), 2.19 (s,
13
1
6
H); C{ H} NMR (101 MHz, CDCl ) δ 147.7, 144.0, 143.8, 140.2, 136.7, 131.6,
3
1
30.1, 128.5, 127.8, 127.1, 125.8, 124.0, 120.0, 116.0, 21.3; HRMS (ESI) Calcd. for
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
+
C H B N O [M] : 476.2231, found: 476.2230; IR (neat): v = 465, 668, 714, 754,
3
2
26
2
2
-1
1
229, 1271, 1336, 1425, 1542, 1606, 2363, 3022, 3373 cm .
13,14-bis(4-methoxyphenyl)-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (6). 6 was
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
11
obtained as a yellow soild in 83% (76 mg). M.p.: > 300℃; B NMR (128 MHz,
1
CDCl ) δ 30.6; H NMR (400 MHz, CDCl ) δ 7.26–7.21 (m, 2H), 7.15 (d, J = 7.4 Hz,
3
3
2
6
1
H), 7.11 (s, 2H), 7.00 (d, J = 8.0 Hz, 2H), 6.92–6.88 (m, 4H), 6.85–6.83 (m, 4H),
1
3
1
.68–6.66 (m, 4H), 3.75 (s, 6H); C{ H} NMR (101 MHz, CDCl ) δ 156.9, 147.7,
3
44.0, 140.1, 136.7, 131.6, 130.1, 128.5, 123.9, 120.0, 116.0, 112.9, 55.1; HRMS
+
(ESI) Calcd for C H B N O [M] : 508.2130, found: 508.2127; IR (neat): v = 755,
3
2
26
2
2
3
112, 1173, 1234, 1278, 1340, 1428, 1500, 1538, 1608, 2365, 3397 cm-1.
1
1
3,14-bis(4-fluorophenyl)-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (7). 7 was
o
11
obtained as a yellow soild in 60% (52 mg). M.p.: > 300 C; B NMR (128 MHz,
19
1
CDCl ) δ 30.4; F NMR (376 MHz, CDCl ) δ -117.1; H NMR (400 MHz, CDCl ) δ
3
3
3
7
6
1
1
4
.28–7.24 (m, 2H), 7.15 (d, J = 7.6 Hz, 2H), 7.05 (s, 2H), 7.01 (d, J = 8.0 Hz, 2H),
1
3
1
.94–6.81 (m, 12H); C{ H} NMR (101 MHz, CDCl ) δ 160.6 (d, J = 244.5 Hz),
3
47.9, 143.4, 140.2, 139.8 (d, J = 3.6 Hz), 132.1 (d, J = 7.7 Hz), 130.1, 128.9, 123.7,
+
20.2, 116.1, 114.6 (d, J = 21.1 Hz); HRMS (ESI) Calcd for C H B F N O [M] :
3
0
20
2
2
2
84.1730, found: 484.1727; IR (neat): v = 668, 712, 754, 829, 1211, 1271, 1344, 1426,
-1
1498, 1541, 2364, 3409 cm .
3,14-bis(4-chlorophenyl)-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (8). 8 was
1
o
11
obtained as a yellow soild in 87% (81 mg). M.p.: > 300 C; B NMR (128 MHz,
1
CDCl ) δ 31.3; H NMR (400 MHz, CDCl ) δ 7.28–7.24(m, 2H), 7.16 (d, J = 7.6 Hz,
3
3
2
H), 7.14–7.10 (m, 4H), 7.02–7.00 (m, 4H), 6.95–6.91 (m, 4H), 6.88–6.85 (m, 4H);
1
3
1
C{ H} NMR (101 MHz, (CD ) SO) δ 147.4, 143.0, 142.9, 141.6, 132.8, 130.5,
3
2
1
29.9, 129.3, 128.2, 123.3, 120.2, 117.1; HRMS (ESI) Calcd for C H B Cl N O
30 20 2 2 2
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+
[
M] : 516.1139, found: 516.1136; IR (neat): v = 597, 659, 708, 754, 821, 1012, 1089,
-1
1
229, 1270, 1336, 1425, 1481, 1539, 1608, 2366, 3395 cm .
13-(4-methoxyphenyl)-14-(4-(trifluoromethyl)phenyl)-di-2,1-borazaronaphtho[2,3-b:
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
',3'-f]oxepine (9). 9 was obtained as a yellow soild in 80% (78 mg). M.p.:
o
11
19
2
80-282 C; B NMR (128 MHz, CDCl ) δ 31.6; F NMR (376 MHz, CDCl ) δ -62.3;
3 3
1
H NMR (400 MHz, CDCl ) δ 7.39 (d, J = 7.9 Hz, 2H), 7.27–7.24 (m, 2H), 7.17–7.12
3
(
m, 3H), 7.04 (dd, J = 7.8, 20.8 Hz, 4H), 6.94–690 (m, 5H), 6.81 (d, J = 8.4 Hz, 2H),
1
3
1
6
1
.66 (d, J = 8.4 Hz, 2H), 3.73 (s, 3H); C{ H} NMR (101 MHz, CDCl ) δ 157.3,
3
48.2, 148.1, 147.4, 144.0, 142.8, 140.2, 140.1, 135.7, 131.6, 131.0, 130.2, 130.0,
128.8, 127.3 (q, J = 32.2 Hz), 125.7, 124.5 (q, J = 3.6 Hz), 124.3 (q, J = 272.7 Hz),
1
23.8, 123.7, 120.2, 120.1, 116.1, 113.2, 55.1; HRMS (ESI) Calcd for
+
C H B F N O [M] : 546.1898, found: 546.1895; IR (neat): v = 753, 1066, 1111,
3
2
23
2
3
2
2
-1
1166, 1235, 1324, 1427, 1611, 2338, 2366, 3400 cm .
5
,7-dibutyl-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (10). 10 was
o
11
obtained as a yellow soild in 63% (53 mg). M.p.: 231-234 C; B NMR (128 MHz,
1
CDCl ) δ 31.9; H NMR (400 MHz, CDCl ) δ 7.36–7.32 (m, 2H), 7.27 (d, J = 7.6,
3
3
2
1
1
H), 7.15–7.05(m, 8H), 7.00–6.90 (m, 8H), 4.21 (s, 4H), 1.87–1.79 (m, 4H),
1
3
1
.60–1.53 (m, 4H), 1.06 (t, J = 7.3 Hz, 6H); C{ H} NMR (101 MHz, CDCl ) δ
3
47.4, 144.3, 143.8, 141.4, 131.0, 130.9, 128.6, 127.4, 125.2, 124.9, 119.4, 113.7,
+
43.4, 31.7, 20.8, 14.2; HRMS (ESI) Calcd for C H B N O [M] : 560.3170, found:
3
8
38
2
2
5
2
60.3167; IR (neat): v = 595, 699, 740, 1232, 1324, 1348, 1404, 1634, 2365, 2927,
-1
955, 3438 cm .
5,7,13,14-tetraphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (11). 11 was
o
11
obtained as a yellow soild in 69% (58 mg). M.p.: > 300 C; B NMR (128 MHz,
1
CDCl ) δ 30.1; H NMR (400 MHz, CDCl ) δ 7.22–7.09 (m, 14H), 7.03–6.96 (m, 8H),
3
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1
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1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
13
1
6
1
.85–6.81 (m, 6H), 6.10 (d, J = 8.4 Hz, 2H); C{ H} NMR (101 MHz, CDCl ) δ
3
47.8, 144.1, 143.5, 142.0, 130.9, 130.1, 129.6, 128.3, 128.2, 127.5, 126.8, 125.3,
+
123.9, 119.9, 115.9, 100.0; HRMS (ESI) Calcd for C H B N O [M] : 600.2544,
4
2
30
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
found: 600.2541; IR (neat): v = 536, 591, 696, 734, 906, 1070, 1120, 1235, 1296,
-
1
1
5
328, 1402, 1490, 1538, 1585, 2367, 3054, 3435 cm .
,7-dibenzyl-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine (12). 12
o
11
was obtained as a yellow soild in 78% (64 mg). M.p.: > 300 C; B NMR (128 MHz,
1
CDCl ) δ 31.4; H NMR (400 MHz, CDCl ) δ 7.25–7.20 (m, 8H), 7.15–7.11 (m, 9H),
3
3
1
3
1
7
.06–6.94 (m, 11H), 6.87 (t, J = 7.4 Hz, 2H), 5.05 (s, 4H); C{ H} NMR (101 MHz,
CDCl ) δ 147.9, 144.1, 143.9, 141.6, 138.4, 130.9, 130.8, 128.8, 128.5, 127.5, 126.6,
3
+
1
6
25.9, 125.3, 124.8, 119.9, 114.7, 47.3; HRMS (ESI) Calcd for C H B N O [M] :
4
4
34
2
2
28.2857, found: 628.2855; IR (neat): v = 595, 697, 753, 1118, 1231, 1334, 1358,
-1
1410, 1490, 1539, 1605, 2338, 2368, 3433 cm .
5
,7-dibenzyl-3,9-difluoro-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepin
o
11
e (13). 13 was obtained as a yellow soild in 73% (63 mg). M.p.: > 300 C; B NMR
1
9
1
(
128 MHz, CDCl ) δ 31.5; F NMR (376 MHz, CDCl ) δ -110.4; H NMR (400 MHz,
3
3
CDCl ) δ 7.26–7.21(m, 4H), 7.15–6.96 (m, 20H), 6.66–6.58 (m, 4H), 4.95 (s, 4H);
3
1
3
1
C{ H} NMR (101 MHz, CDCl ) δ 162.3 (d, J = 246.3 Hz), 146.2, 142.8, 142.5,
3
1
42.1 (d, J = 10.9 Hz), 136.6, 131.3 (d, J = 10.2 Hz), 129.7, 127.6, 126.5, 125.9,
124.7, 124.4, 120.4, 106.9 (d, J = 23.0 Hz), 100.6 (d, J = 26.2 Hz), 46.5; HRMS (ESI)
+
Calcd for C H B F N O [M] : 664.2669, found: 664.2667; IR (neat): v = 523, 1112,
4
4
32
2
2
2
-1
1
173, 1345, 1414, 1631, 2364, 3437 cm .
5,7-dibenzyl-3,9-dimethyl-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepi
o
11
ne (14). 14 was obtained as a yellow soild in 77% (66 mg). M.p.: 284–286 C; B
1
NMR (128 MHz, CDCl ) δ 30.6; H NMR (400 MHz, CDCl ) δ 7.26–7.19 (m, 4H),
3
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.13–6.97 (m, 20H), 6.76 (s, 2H), 6.69 (d, J = 7.9 Hz, 2H), 4.97 (s, 4H), 2.22 (s, 6H);
1
3
1
C{ H} NMR (101 MHz, CDCl ) δ 146.5, 143.2, 140.7, 138.0, 137.6, 129.9, 129.6,
3
127.4, 126.4, 125.5, 124.9, 124.1, 121.6, 120.2, 113.9, 76.3, 76.0, 75.7, 46.1, 21.1;
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+
HRMS (ESI) Calcd for C H B N O [M] : 656.3170, found: 656.3166; IR (neat): v =
4
6
38
2
2
-1
6
69, 699, 1125, 1232, 1317, 1345, 1406, 1613, 2338, 2367, 3448 cm .
Procedure for Double Bromination of 3
Under argon atmosphere, to a dichloromethane solution (10 mL) of 3 (148 mg,
0
.33 mmol) was added a solution of Br (117 mg, 0.73 mmol) in dichloromethane (10
2
o
mL) over 30 min at 0 C. After the completion of the dropwise addition, the reaction
mixture was slowly returned to room temperature. Solvent was then removed in vacuo
to give 15 as a yellow solid in quantitive yield (178 mg).
2
,10-dibromo-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxepine
(15).
o
11
1
M.p.: > 300 C; B NMR (128 MHz, CDCl ) δ 31.7; H NMR (400 MHz, CDCl ) δ
3
3
7
7
1
.31 (dd, J = 8.6, 2.2Hz, 2H), 7.24 (d, J = 2.1 Hz, 2H), 7.11 (t, J = 7.4 Hz, 4H),
1
3
1
.03–6.98 (m, 4H), 6.92–6.89 (m, 8H); C{ H} NMR (101 MHz, CDCl ) δ 146.7,
3
44.4, 143.4, 138.9, 132.0, 131.3, 130.5, 127.6, 125.6, 125.5, 117.6, 112.3; HRMS
+
(ESI) Calcd for C H B Br N O [M] : 606.0108, found: 606.0105; IR (neat): v = 654,
3
0
20
2
2
2
-1
7
02, 803, 1024, 1094, 1261, 1335, 1434, 2338, 2366, 2962, 3392 cm .
Suzuki cross-coupling reaction of 15 with 4-methoxyphenylboric
To a pressure resistant tube under an atmosphere of Ar was sequentially added 15
(
50 mg, 0.08 mmol), 2-(4-Methoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
188 mg, 0.6 mmol), Na CO (50 mg, 0.48 mmol), Pd(PPh ) (28 mg, 0.024 mmol),
(
2
3
3 4
THF (4 mL) and H O (0.26 mL). The reaction mixture was heated at 80 °C for 20
2
hours. After this time, the reaction mixture was cooled to room temperature, diluted
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with dichloromethane and washed with water. The organic layer was separated, dried
over MgSO and removed in vacuo. The product was purified by flash column
4
chromatography on silica gel with dichloromethane/hexanes (1:2), which is a yellow
solid in 55% yield (28 mg).
0
1
2
3
4
5
6
7
8
9
0
1
2
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8
9
0
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9
0
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2
-bromo-10-(4-methoxyphenyl)-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]
o
11
1
oxepine (16). M.p.: 266–268 C; B NMR (128 MHz, CDCl ) δ 30.8; H NMR (400
3
MHz, CDCl ) δ 7.47–7.42 (m, 3H), 7.31–7.24 (m, 3H), 7.15–7.10 (m, 5H), 7.07–7.00
3
1
3
1
(
m, 3H), 6.97–6.88 (m, 10H), 3.82 (s, 3H); C{ H} NMR (101 MHz, CDCl ) δ 158.7,
3
1
48.3, 146.3, 144.8, 143.7, 143.7, 143.6, 139.1, 139.0, 133.4, 133.1, 131.9, 131.1,
130.7, 127.9, 127.8, 127.6, 127.5, 125.5, 125.5, 125.4, 124.1, 117.6, 116.5, 114.1,
+
1
6
12.2, 55.4; HRMS (ESI) Calcd for C H B Br N O [M] : 632.1442, found:
3
7
27
2
1
2
2
32.1438; IR (neat): v = 707, 1179, 1244, 1283, 1342, 1428, 1514, 1544, 1609, 2363,
-1
3384 cm .
To a pressure resistant tube under an atmosphere of Ar was sequentially added 15
50 mg, 0.08 mmol), 2-(4-Methoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
384 mg, 1.6 mmol), Na CO (52 mg, 0.49 mmol), Pd(PPh ) (29 mg, 0.025 mmol),
(
(
2
3
3 4
THF (2 mL) and H O (0.26 mL).The reaction mixture was heated at 80 °C for
2
4
8h .After this time, the reaction mixture was cooled to room temperature, diluted
with dichloromethane and washed with water. The organic layer was separated, dried
over MgSO and removed in vacuo.The product was purified by flash column
4
chromatography on silica gel with dichloromethane/hexanes(1:1), which is a yellow
solid in 72% yield (39 mg).
2,10-bis(4-methoxyphenyl)-13,14-diphenyl-di-2,1-borazaronaphtho[2,3-b:2',3'-f]oxep
o
11
1
ine (17). M.p.: > 300 C; B NMR (128 MHz, CDCl ) δ 31.7; H NMR (400 MHz,
3
CDCl ) δ 7.47–7.42 (m, 6H), 7.28 (s, 2H), 7.15–7.10 (m, 6H), 7.07–7.00 (m, 4H),
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13
1
6
1
.97–6.90 (m, 10H), 3.81 (s, 6H); C{ H} NMR (101 MHz, CDCl ) δ 158.6, 147.9,
3
44.1, 143.9, 139.2, 133.0, 130.8, 127.8, 127.7, 127.5, 127.4, 125.3, 124.1, 116.4,
+
114.1, 55.3; HRMS (ESI) Calcd for C H B N O [M] : 660.2756, found: 660.2751;
4
4
34
2
2
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
IR (neat): v = 818, 1143, 1178, 1245, 1294, 1340, 1436, 1513, 1608, 2366, 3432 cm-1.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications
website at DOI:10.1021/xxxxxxxxxxxxx.
UV−vis and emission spectra of 3-17
1
Temperature dependent HNMR spectra for 12
DFT calculations details for 3 and 3’
Copies of NMR spectra of all new compounds, and single crystal X-ray data
X-ray crystallography data for compound 3, 8 and 16 (CIF)
AUTHOR INFORMATION
Corresponding Author
E-mail: hxxytdw@tjnu.edu.cn (D. Tian)
hxxyxsy@tjnu.edu.cn (S. Xing),
hxxyzbl@gmail.com (B. Zhu),
cmcui@nankai.edu.cn (C. Cui).
Notes
The authors declare no competingfinancial interest.
ACKOWLEDGEMENTS
This work was supported by the National Natural Science Foundation of China
(
NSFC) (21502141), the Foundation of the Development Program of Future Expert in
Tianjin Normal University (WLQR20170109), the Natural Science Foundation of
Tianjin City (18JCQNJC06700), the Program for Innovative Research Team in
University of Tianjin (TD13-5074).
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