Piezochromic luminescence behaviors of two new benzothiazole-enamido boron difluoride complexes: Intra- and inter-molecular effects induced by hydrostatic compression

Article abstract of DOI:10.1039/c5cc01902h

Two new propeller-shaped benzothiazole-enamide boron difluoride complexes exhibiting piezochromic luminescence upon mechanical grinding or hydrostatic compression were prepared. The two analogues displayed the red shift in luminescence under high pressure, while compound 2 with ICT effects showed a more sensitive piezochromic response at low pressure (<1.5 GPa). The different piezochromic luminescence behaviors of these compounds were investigated. This journal is

Full text of DOI:10.1039/c5cc01902h

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Z. Liu, X. Wang,
Q. Liu, H. Yan, M. Yao, Q. Zhang, S. Gong and W. He, Chem. Commun., 2015, DOI:
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/C5CC01902H
Journal Name
RSCPublishing
COMMUNICATION
Piezochromic Luminescent Behaviors of Two New
Benzothiazole-enamido Boron Difluoride Complexes:
Intra- and Inter-molecular Effects Induced by
Hydrostatic Compression
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
Xiaoqing Wang,a Qingsong Liu,a Hui Yan,a Zhipeng Liu,*,a Mingguang Yao,*,b
Qingfu Zhang,a Shuwen Gong,a and Weijiang He*,c
DOI: 10.1039/x0xx00000x
www.rsc.org/
piezochromic luminescent behavior of the two compounds upon
compression/decompression implied that the compressionꢀpromoted
intramolecular charge transfer (ICT) instead of the intermolecular
interaction contributed largely to the PLM nature of compound 2.
Two new propeller-shaped benzothiazole-enamide boron
difluoride complexes exhibiting the piezochromic luminescence
upon mechanical grinding or hydrostatic compression were
prepared. The two analogues displayed the red shifts in
luminescence under high pressure, while compound 2 with ICT
effect showed a more sensitive piezochromic response at low
pressure (<1.5 GPa). The different piezochromic luminescence
behaviors of these compounds were investigated.
Piezochromic luminescent materials (PLMs) which change
their luminescence upon the mechanical grinding/shearing or
hydrostatic compression are attracting great interests owing to
their promising potential as memory devices, sensors and
switches.[1] As the PLMs of novel structures were being
developed, the different mechanisms for their piezochromic
luminescent behaviours such as phase transformation of
aggregation,[2] excimer formation or dissolution,[3] and
pressureꢀinduced chemical changes were proposed based on
their luminescence alteration stimulated by the mechanical
grinding and shearing.[4] Moreover, the piezochromic
luminescent response of new PLM systems upon high
hydrostatic compression have been reported,[5] and this
controllable stimulation is more helpful to understand these
PLMs.
Chart 1. Chemical structures of compounds
1 and 2.
Compounds 1 and 2 were synthesized via a threeꢀstep procedure
shown in Scheme S1 (See details in SI). Their threeꢀringꢀfused πꢀ
conjugated skeleton (parent aromatic plane, D) was constructed via
the boron coordination of the benzothiazoleꢀenamide derived ligand.
Three phenyl groups (A, B and C) were tethered to ring D to form a
propellerꢀshaped structure. Both 1 and 2 were expected to display
high efficient solidꢀstate emission due to the restricted
intramolecular rotation of phenyl rings A, B, and C in the solid state.
The two N,Nꢀdimethylamino groups were decorated to phenyl rings
B and C in 2 as the electronꢀdonating group to explore the ICT effect
on the piezochromic luminescence, considering the intrinsic
electronꢀwithdrawing nature of boron difluoride complexes. The TDꢀ
DFT calculations using the crystal structure of compound 2 showed
that its HOMOs were mainly delocalized on the B and C phenyl
rings, while its LUMOs were mainly delocalized on the D ring,
supporting the ICT nature of compound 2 (Figure S11).
The propellerꢀshaped πꢀconjugated molecules are among the most
6]
frequently adopted structures to devise PLMs.[3dꢀe,
These
compounds display high efficient emission in the solid state due to
aggregationꢀinduced emission,[6] and the pressureꢀinduced structure
or packing alteration was proposed for their piezochromic
luminescence. Besides the grindingꢀinduced piezochromic
luminescence, both Yamaguchi and Tian have reported the
hydrostatic pressureꢀstimulated piezochromic luminescence of the
In CH2Cl2, compound 1 showed the absorption (λabs) and
luminescence maxima (λem) at 395 (ε
= 34200 Mꢀ1cmꢀ1) and 460 nm,
propellerꢀshaped
πꢀconjugated
molecules,
and
the
respectively; while those for compound 2 were 409 (ε
= 43800 Mꢀ
tetrathiazolythiopheneꢀ and anthraceneꢀderived luminophores upon
hydrostatic compression displayed the redꢀshifted emission.[5a,b]
These studies also showed that the hydrostatic compression is a more
effective and controllable means to explore piezochromic effect of
the propellerꢀshaped πꢀconjugated molecules. Herein, two new
propellerꢀshaped benzothiazoleꢀenamido boron difluoride complexes
(1 and 2, Chart 1) were reported as the new class of PLMs, in which
compound 2 bears two additional N,Nꢀdimethylamino groups. The
1cmꢀ1) and 492 nm (Figure S1ꢀ2 and Table S1). The longer λabs and
λem of 2 can be attributed to its ICT effect from the N,Nꢀdimethyl
group of phenyl rings B and C to phenyl ring D, in which the boron
difluoride coordination endows ring
D with the electronꢀ
withdrawing nature. Both compounds 1 and 2 displayed very weak
fluorescence with the quantum yields (φf) lower than 0.01 in organic
solvents of low viscosity such as hexane, toluene and CH2Cl2 (Figure
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 1

ChemComm
Page 2 of 4
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C5CC01902H
higher amorphization of compound 2 probably lead to changes in
packing, allowing a more planar structure and perhaps better dipoleꢀ
dipole intermolecular interactions which lead to a large red shift of
the fluorescence.[6]
1). However, their φf in solvents of highꢀviscosity such as glycerol,
were significantly enhanced to 0.46 (1, λem, 458 nm) and 0.10 (2, λem,
522 nm). This viscosityꢀdependent fluorescence suggested that the
nonꢀradiative relaxation of the excited luminophore via
intramolecular rotation of phenyl rings A, B and C was impeded by
the higher solvent viscosity, which is the typical luminescence
behavior of AIE compounds.[6g,7] Solvent substitution with the
viscous solvent did not induce any obvious luminescence shift for
compound 1, while a distinct bathochromic shift from 478 nm (in
hexane) to 522 nm (in glycol) was observed for compound 2 (Figure
1b), suggesting compound 2 is an ICT luminophore. Considering the
propellerꢀshaped structure and the additional N,Nꢀdimethylamino
groups in 2, the high polarityꢀinduced bathochromic luminescence
shift of 2 could be ascribed to the promoted ICT effect in 2 other
than the excimer formation.
The piezochromic luminescence of the two compounds was
further investigated by compression with the hydrostatic pressure
created by a diamond anvil cell (DAC) up to ~11 GPa. For
compound 1, as shown in Figure 3a, no distinct change in the
luminescence can be observed in the pressure range from 1
atmospheric pressure to 1.13 GPa. The distinct luminescence
decrease was observed only after pressure above 1.47 GPa, and the
luminescence band became asymmetric due to the emergence of a
shoulder on its right side. Further increment of pressure led to a
gradual red shift and intensity decrease of the luminescence. The
luminescence spectrum recorded at 8.3 GPa showed one broad and
significantly weakened band centered at 554 nm. The luminescence
maximum of the band was shifted to 571 nm at 10.84 GPa. In the
following decompression process, the distinct splitted luminescence
band appeared again in the pressure range from 4.23 to 0.07 GPa
(Figure 3b). The dual bands observed in the luminescence spectra
implied an additional excited species besides the excited 1, and the
excimer formed upon hydrostatic compression might be the origin
for the additional luminescence band. Compared with the symmetric
singleꢀbanded luminescence spectrum at 1.13 GPa in the
compression process, the dualꢀbanded luminescence spectrum at
0.07 GPa in the decompression process suggested that the
luminescence recovery upon decompression was distinctly delayed
due to the dimer formed at high hydrostatic pressure. On the other
hand, the more obvious dual band luminescence spectra found in the
decompression process than those found upon compression
suggested the delayed recovery of the compound in the
decompression process.
1000
1100
(a)
1000
900
800
700
600
500
400
300
200
100
0
(b)
Toluene
Toluene
CH3CN
CH3CN
800
600
400
200
0
CH2Cl2
CH2Cl2
DMF
DMF
Glycol
Ethanol
Glycerol
Hexane
THF
Glycol
Ethanol
Glycerol
Hexane
THF
500
550
600
650
400
450
500
550
Wavelength (nm)
Wavelength (nm)
Figure 1. Luminescence spectra of compounds
1
(a, 10–5 M) and (b, 10–5 M) in
2
hexane, toluene, CH2Cl2, THF, CH3CN, DMF, ethanol, ethylene glycol and glycerol.
The absorption band of compounds 1 and 2 in the solid state
disclosed the λabs of 406 nm (1) and 414 nm (2), which were slightly
bathochromic shifted from those in solutions. The two compounds
showed the strong luminescence bands centered at 473 nm (1) and
518 nm (2), respectively, and the corresponding φf were 0.60 (1) and
0.27 (2), much higher than those in normal organic solvents (<0.01)
(Figure S3 and Table S1). There is no distinct luminescence shift for
both 1 and 2 when compared with their luminescence in solvents
such as CH2Cl2 and THF. The blocked intramolecular rotation due to
the crystal matrix led to the luminescence enhancement in the solid
powder state. [6g,7]
(a)
(b)
8.83 GPa
6.4 GPa
4.23 GPa
2.31 GPa
0.99 GPa
0.07 GPa
1 atm
0.7 GPa
1.13 GPa
1.47 GPa
2.06 GPa
2.93 GPa
3.88 GPa
5.16 GPa
5.92 GPa
6.9 GPa
8.3 GPa
9.88 GPa
10.84 GPa
Compression
Decompression
425 450 475 500 525 550 575 600
Wavelength (nm)
420 450 480 510 540 570 600 630 660
Wavelength (nm)
(d)
(c)
Compression
8.31GPa
1 atm
5.76GPa
3.03GPa
0.19GPa
1 atm
0.53 GPa
1.07 GPa
2.17 GPa
3.05 GPa
4.07 GPa
5.3 GPa
6.18 GPa
7.33 GPa
8.13 GPa
9.19 GPa
10.34 GPa
Decompression
450 500 550 600 650 700
Wavelength (nm)
450
500
550
600
650
700
Wavelength (nm)
Figure 3. Luminescence spectra of compounds
recorded in the compression and and the following decompression
processes ( and ).
1 (a and b) and 2 (c and d)
Figure 2.
ground and CH2Cl2 fumed, λex, 414 nm. (
and the CH2Cl2-fumed ground powder under UV light (365 nm).
(
a
) Normalized luminescence spectra of solid compound
2, after being
(
a
c)
b) Photographs of the ground powder of
b
d
2
As to compound 2, the gradual bathochromic shift of its
luminescence band was observed with the concomitant intensity
decrease upon hydrostatic compression (Figure 3c). The
luminescence maximum was gradually redꢀshifted from 520 nm at
ambient pressure to 645 nm at 10.34 GPa. All the changes in the
compression process were reversible upon decompression, and the
luminescence spectra of 2 recovered back to the original one when
the pressure turned back to the ambient pressure (Figure 3d).
Different from compound 1, all the luminescence spectra of
compound 2 determined in the compression/decompression cycle
showed only one luminescence band, suggesting no new excited
species was formed in this process.
Both compounds
1
and
2
displayed the redꢀshifted
luminescence upon being ground with a pestle for 20 min.
Compound 2 showed a distinct luminescence shift from 518 to 582
nm, and the green yellow emitting powder turned into orange
(Figure 2). However, the bathochromic shift of 1 was only 8 nm
(Figure S4). In addition, the luminescence decrease was also
observed for both compounds. Fuming the ground powder with
CH2Cl2 vapor led to the luminescence recovery for both 1 and 2. All
these indicated that both compounds were piezochromic compounds.
In addition, the grinding led to distinct changes in their powder Xꢀ
ray diffraction (XRD) patterns (Figure S5). All the diffraction peaks
of compound 1 were weakened, while the peaks for 2 displayed the
more significant weakening and broadening. Grindingꢀinduced
The profiles for the hydrostatic compression/decompression
cycle based on the luminescence wavenumber at different
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 3 of 4
Journal Name
ChemComm
View Article Online
COMMUNICATION
DOI: 10.1039/C5CC01902H
pressures were investigated. For compound 1, its wavenumber
hydrogen bonding system and intermolecular C–H···π interaction
constructed the 3D network, which fixed their propeller
conformation and blocked the nonꢀradiative relaxation via blade
rotation and excimer formation, favoring their AIE in solid state.
With the crystal structures of compounds 1 and 2, their molecular
packing modes were optimized preliminary by the density functional
theory (DFT) simulation at 1.5 and 4.0 GPa using CASTEP program
and GGAꢀPBE function.[5a,8] The results demonstrated that both
compounds 1 and 2 adopted two conformations, I and II upon
compression (Figure S13–S20). In conformation I, the dihedral
angles of phenyl rings A, B and C with ring D decreased obviously
upon compression (Table S2–5), displaying the tendency of coꢀ
planation of rings A, B, C and D, and the higher pressure led to more
planar structure. Similar tendency was also observed for
remained unchanged in the pressure range from ambient to 1.13
GPa, and the small red shifts of 11 and 21 nm at 1.47 GPa and
2.06 GPa, were observed respectively (Figure 4a). Its
wavenumber was decreased in the subsequent compression to
10.84 GPa. The initial following decompression from 10.84 to
2.31 GPa displayed a slightly lower increasing rate of
wavenumber than the decreasing rate at the same pressure. The
enhanced increasing rate was observed after decompression to
2.31GPa.
The distinct hysteresis loop observed in the
delayed
compression/decompression cycle suggested
a
recovery of luminescence upon decompression and the poor
reversibility of the compressionꢀinduced piezochromic effect.
The pressureꢀdependent intermolecular interaction, probably
the enhanced
π–π intermolecular interaction by high pressure conformation II. At 1.5 GPa, the packing mode showed that both
might be the origin. In contrast, an almost linear decrease of compounds took the more planar structures than those at ambient
wavenumber with the pressure was disclosed for compound 2,
and the following decompression procedure from 10.34 GPa
disclosed an inverse process with a similar rate, implying the
pressure, favoring the weak intermolecular C–H···F and C–H···π
interactions, while no π–π interaction was observed (Figure S14 and
S16). At 4.0 GPa, the two luminophores became more planar than
those at 1.5 GPa, and π–π intermolecular interaction was observed in
the simulated packing modes. In addition, the π–π interaction in
compound 1 was much stronger than that in compound 2 (Figure
S18 and Figure S20), which is consistent with the observation of the
distinct hysteresis loop of compound 1.
piezochromic effect of
2 was of excellent reversibility in the
studied pressure range (Figure 4b). No hysteresis was observed
for the compression/decompression cycle, suggesting the weak
intermolecular interaction in compound
2
even upon
compression, which favored the quick relaxation of
wavenumber upon decompression. Such a reversibility of
piezochromic effect even upon compression at 10 GPa is
worthy to be noted in the chemistry of piezochromism.
Compared with the negligible piezochromic effect of
With the piezochromic behaviors and simulated molecular
packing modes, it is proposed that the coꢀplanation of the propeller
structures upon compression is essential for the piezochromic
luminescent behaviors of both compounds. Considering the donorꢀ
acceptor structure of 2, it is expected that the compressionꢀinduced
molecule coꢀplanation promotes the intramolecular CT effect from
N,Nꢀdimethyl amino group to ring D, resulting in the luminescence
bathochromic shift and intensity decrease (Figure 5b). [6g,9] Since no
more excited species was induced in the compression/decompression
cycle, only one luminescence band was observed. For compound 1,
the compressionꢀinduced coꢀplanation leads to the strong πꢀπ
compound
1 at low pressure, compound 2 showed more distinct
λem shift in the pressure range from ambient pressure to 2.17
GPa (Figure S6). The red shifts of λem at 0.53 GPa, 1.07 GPa
and 2.17 GPa are 21, 26 and 42 nm, respectively. The higher
piezochromism sensitivity of
2 than 1 at low compression
pressure indicated that compound
practical applications.
2
was more desirable for
intermolecular interaction, which favors not only the excimer
1.2x105
1.2x105
1.2x105
1.1x105
1.1x105
1.1x105
1.1x105
1.1x105
1.0x105
1.0x105
1.0x105
9.8x104
9.6x104
[10]
1.4x105
1.3x105
1.3x105
1.2x105
1.1x105
1.1x105
formation but also the luminescence quenching.
Therefore the
(a)
(b)
dual band luminescence (excimer and monomer bands) was
observed accompanying with the intensity decrease. The negligible
luminescence change of compound 1 upon compression at low
pressure should be originated from the absence of πꢀπ intermolecular
interaction at low pressure. For compound 2, the contribution of
intermolecular π–π interaction for the piezochromic response at very
high pressure cannot be excluded currently, yet the absence of
hysteresis loop suggests the intermolecular interaction is limited.
D
e
-
c
o
m
p
r
e
s
s
C
i
o
o
n
m
p
r
e
Decompression
Compression
s
s
i
o
n
0
2
4
6
8
10
12
0
2
4
6
8
10
12
Pressure (GPa)
Pressure (GPa)
Figure 4. Hydrostatic compression/decompression profiles of compounds 1 (a)
and ) based on the luminescence wavenumber at different hydrostatic
2 (b
pressures according to Figure 3
The crystal structures of compounds 1 and 2 determined by Xꢀray
diffraction showed that both compounds took the similar propeller
conformation (Figure S7 and S9), and boron coordination adopted a
typical tetrahedral geometry to form N^Nꢀchelating sixꢀmembered
ring D. In this propeller conformation, the phenyl rings A, B and C
act as three blades, while the benzothiozole motif and ring D form a
large aromatic system as the parent plane. The dihedral angles of this
parent plane with the neighboring A, B and C rings are 72.03°,
65.60° and 61.00° in 1, and 73.63°, 73.56° and 83.16° in 2,
respectively. Multiple weak intermolecular hydrogen bonds such as
F1···H21–C21 (3.36 Å), F3···H2–C2 (3.55 Å), F4···H2–C2 (3.18
Å), F3···H48–C48 (3.35 Å) in 1, and F1···H30–C30 (3.42 Å),
F2···H17–C17 (3.41 Å) in 2, were found (Figure S8 and S10).
Although weak intermolecular C–H···π interactions were detected in
1 and 2 (~3.6 Å), the π–π interaction between the aromatic systems
was not observed due to the steric hindrance of the three blades. The
Figure 5. Proposed mechanism of the piezochromic behaviors for
A
1 (a) and 2 (b).
, the electron-withdrawing motif; D, the electron-donating group.
Conclusions
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 3

ChemComm
Page 4 of 4
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C5CC01902H
In summary, two new propellerꢀshaped benzothiazoleꢀenamide
boron difluoride complexes have been synthesized, which
demonstrated the piezochromic luminescence upon mechanical
grinding or hydrostatic compression but behaved differently due to
their structures. Both 1 and 2 exhibited the distinct redꢀshifted
luminescence at high pressure, while compound 2 bearing two N,Nꢀ
dimethyl amino groups showed more sensitive piezochromic
response at low pressure (<1.5 GPa) compared with compound 1.
Compound 1 showed the dual band luminescence and the distinct
hysteresis loop during the compression/decompression process,
while compound 2 always showed a single band luminescence and
no hysteresis. The compressionꢀinduced luminophore coꢀplanation
led to the distinct enhancement of πꢀπ intermolecular interaction in
compound 1 or intramolecular CT effect in compound 2, which were
proposed to be responsible for their different piezochromic
luminescence. The enhanced πꢀπ intermolecular interaction favored
the excimer formation, resulting in the dual band luminescence
(excimer and monomer luminescence) of compound 1. This study
implied that the pressureꢀdependent πꢀπ intermolecular interaction
and intramolecular CT effect were efficient to induce the
piezochromic luminescence. The distinct piezochromic effect of 2 at
low compression pressure implied that the propellerꢀshaped AIE
luminophore with ICT effect should be a valuable strategy to design
PLMs of high sensitivity.
Dong, Z. Liu, Z. Bo and B. Z. Tang, Adv. Mater. 2011, 23, 3261. (e)
G. Zhang, J. Lu, M. Sabat and C. Fraser, J. Am. Chem. Soc. 2010,
132, 2160. (f) Y. Sagara, S. Yamane, T. Mutai, K. Araki and T. Kato,
Adv. Funct. Mater. 2009, 19, 1869. (g) R. H. Pawle, T. E. Haas,
Müller, and S. W. Thomas III, Chem. Sci. 2014,
5
, 4184.
3
(a) C. Lowe and C. Weder, Adv. Mater. 2002, 14
,
1625. (b) Y. Sagara
and T. Kato, Angew. Chem. Int. Ed. 2008, 47, 5175. (c) Y. Sagara
and T. Kato. Agew. Chem. Int. Ed. 2011, 50, 9128. (d) J. Kunzelman
and M. Kinami, B. R. Crenshaw, J. D. Protasiewicz and C. Weder,
Adv. Mater. 2008, 20, 119. (e) N. Mizoshita, T. Tani and S. Inagaki,
Adv. Mater. 2012, 24, 3350. (f) M. Teng, X. Jia, X. Chen, Z. Ma and
Y. Wei, Chem. Commun.2011, 47, 6078.
4
(a) M.ꢀJ. Teng,, X.ꢀR. Jia,, X.ꢀF. Chen and Y. Wei, Angew. Chem.,
Int. Ed. 2012, 51, 6398. (b) S. Perruchas, X. F. L. Goff, L. Maron, I.
Maurin, F. Guillen, A. Gracia, T. Gacoin and J.ꢀP. Boilot, J. Am.
Chem. Soc. 2010, 132, 10967. (c) S. M. Kwon, S.ꢀJ. Yoon, J.
Gierschner and S. Y. Park, Adv. Mater. 2012, 24, 5487. (d) D. A.
Davis, A. Hamilton, J. Yang, L. D. Cremar, D. V. Gough, S. L.
Potisek, M. T. Ong, P. V. Braun, T. J. Martínez, S. R. White, J. S.
Moore and N. R. Sottos, Nature 2009, 459, 68.
5
(a) K. Nagura, S. Saito, H. Yusa, H. Yamawaki, H. Fujihisa, H. Sato,
Y. Shimoikeda and S. Yamaguchi, J. Am. Chem. Soc. 2013, 135
,
M. Yao would like to thank Prof. B. Zou, Dr. K. Wang, W. Zhang
and Y. Dai for their help in the HP luminescent measurements. This
work was supported by the Natural Science Foundation of China
(21301085), the Natural Science Foundation of Shandong Province
(ZR2011BQ010)
10322. (b), Y. Dong B. Xu, J. Zhang, X. Tan, L. Wang, J. Chen, H.
Lv, S. Wen, B. Li, L. Ye, B. Zou and W. Tian, Angew. Chem. Int. Ed.
2012, 51, 10782. (c) C. M. Martin, S. Guha, M. Chandrasekhar, H. R.
Chandrasekhar, R. Guentner, P. S. Freitas and U. Scherf, Physical
Rev. B 2003, 68, 115203. (d) P. L. Gentili, M. Nocchetti, C. Miliani
and G. Favaro, New. J. Chem. 2004, 28, 379.
Notes and references
a
a
6
(a) J. Wang, J. Mei, R. Hu, J. Z. Sun, A. Qin and B. Z. Tang, J. Am.
Chem. Soc. 2012, 134, 9956. (b) R. Li, S. Xiao, Y. Li, Q. Lin, R.
Institute of Functional Organic Molecules and Materials, School of
Chemistry and Chemical Engineering, School of Material Science and
Engineering, School of Pharmacy, Liaocheng University, Hunan Road
No. 1, Liaocheng 252000, People’s Republic of China; Eꢀmail:
chliuzp@163.com;
Zhang, J. Zhao, C. Yang, K. Zou, D. Li and T. Yi, Chem. Sci. 2014,
5,
3922. (c) J. Luo, L. Li, Y. Song and J. Pei, Chem. Eur. J. 2011, 17
,
10515. (d) H. Li, X. Zhang, Z. Chi, B. Xu, W. Zhou, S. Liu, Y.
Zhang and J. Xu, Org. Lett. 2011, 13, 556. (e) J. Mei, J. Wang, A.
Qin, H. Zhao, W. Yuan, Z. Zhao, H. H. Y. Sung, C. Deng, S. Zhang,
b
State Key Lab of Superhard Materials, Jilin University, Changchun
130012, People’s Republic of China; Eꢀmail: yaomg@jlu.edu.cn;
c
I. D. Williams, J. Sun and B. Z. Tang, J. Mater. Chem. 2011, 22
,
State Key Laboratory of Coordination Chemistry, Coordination
4290. (f) C. Ma, B. Xu, G. Xie, J. He, X. Zhou, B. Peng, L. Jiang, B.
Xu, W. Tian, Z. Chi, S. Liu, Y. Zhang and J. Xu, Chem. Commun.
2014, 50, 7374. (g) J. Mei, Y. Hong, J. W. Y. Lam, A. Qin, Y. Tang
and B. Z. Tang, Adv. Mater. 2014, 26, 5429.
Chemistry Institute, School of Chemistry and Chemical Engineering,
Nanjing University, Hankou Road No. 22, Nanjing 210093, People’s
Republic of China; Eꢀmail: heweij69@nju.edu.cn.
7
(a) J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu, H. S.
Kwok, X. Zhan, Y. Liu, D. Zhu and B. Z. Tang, Chem. Commun.
2001, 1740. (b) Y. Hong, J. W. Y. Lam and B. Z. Tang, Chem.
Commun. 2009, 4332. (c) J. Liu, J. W. Y. Lam and B. Z. Tang, Chem.
Rev. 2009, 109, 5799. (d) Y. Hong, J. W. Y. Lam and B. Z. Tang,
Chem. Soc. Rev. 2011, 40, 5361.
†
Electronic Supplementary Information (ESI) available: Experimental
details, structures, absorption, luminescence, DFT calculations and NMR
spectra. See DOI: 10.1039/c000000x/
1
2
(a) Y. Sagara and T. Kato, Nat. Chem. 2009, 1, 605. (b) A. L. Balch,
Angew. Chem., Int. Ed. 2009, 48, 2641. (c) Z. Chi, X. Zhang, B. Xu,
X. Zhou, C. Ma, Y. Zhang, S. Liu and J. Xu, Chem. Soc. Rev. 2012,
41, 3878. (d) Y. Sagara, T. Komatsu, T. Ueno, K. Hanaoka, T. Kato
and T. Nagano, J. Am. Chem. Soc. 2014, 136, 4273.
8
9
(a) S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip, M. I. J.
Probert, K. Refson and M. C. Payne, Kristallogr. Z. 2005, 220, 567.
(b) J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett. 1996,
77, 3865.
(a) Ito, H. Saito, T. Oshima, N. Kitamura, N. Ishizaka, S. Hinatsu, Y.
Wakeshima, M. Kato, M. Tsuge and K. M. Sawamura, J. Am. Chem.
Soc. 2008, 130, 10044. (b) S.ꢀJ. Yoon, J. W. Chung, J. Gierschner, K.
S. Kim, M.ꢀG. Choi, D. Kim and S. Y. Park, J. Am. Chem. Soc. 2010,
132, 13675. (c) Y. Sagara, T. Mutai, I. Yoshikawa and K. Araki, J.
Am. Chem. Soc. 2007, 129, 1520. (d) X. Luo, J. Li, C. Li, L. Heng, Y.
T. Youshihara, S. I. Druzhinin and K. A. Zachariasse, J. Am. Chem.
Soc. 2004, 126, 8535.
10 C. Kitter, Introduction to Solid State Physics, Wiley, New York, 1996.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012