Pure Organic Room Temperature Phosphorescence from Excited Dimers in Self-Assembled Nanoparticles under Visible and Near-Infrared Irradiation in Water

Article abstract of DOI:10.1021/jacs.9b00859

Pure organic room temperature phosphorescence (RTP) has unique advantages and various potential applications. However, it is challengeable to achieve organic RTP under visible and near-infrared (NIR)-light excitation, especially in aqueous solution. Herei

Full text of DOI:10.1021/jacs.9b00859

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Article
Pure Organic Room Temperature Phosphorescence
from Excited Dimers in Self-Assembled Nanoparticles
under Visible and Near-Infrared Irradiation in Water
Xiao-Fang Wang, Hong-Yan Xiao, Peng-Zhong Chen, Qing-Zheng
Yang, Bin Chen, Chen-Ho Tung, Yu-Zhe Chen, and Li-Zhu Wu
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.9b00859 • Publication Date (Web): 03 Mar 2019
Downloaded from http://pubs.acs.org on March 3, 2019
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Pure Organic Room Temperature Phosphorescence from
Excited Dimers in Self-Assembled Nanoparticles under Visible
and Near-Infrared Irradiation in Water
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Xiao-Fang Wang,[ Hongyan Xiao,
Chen-Ho Tung,
a,b]
[a,b]
Peng-Zhong Chen, Qing-Zheng Yang,[c] Bin Chen,[a,b]
[c]
[a,b]
[a,b]
[a,b]
Yu-Zhe Chen, * and Li-Zhu Wu *.
[a] Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and
Chemistry, Chinese Academy of Sciences Beijing 100190, China.
[b] School of Future Technology, University of Chinese Academy of Sciences Beijing 100049, P. R. China.
[c] Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal
University, Beijing 100875, China.
Supporting Information Placeholder
ABSTRACT: Pure organic room temperature phosphorescence (RTP) has unique advantages and various potential applications.
However, it is challengeable to achieve organic RTP under visible and near-infrared (NIR)-light excitation, especially in aqueous
solution. Herein we assemble difluoroboron β-diketonate compounds to form organic nanoparticles (NPs) in water. The
resulting NPs are able to show efficient RTP, effective uptake and bright imaging of HeLa cells under both visible and NIR-light
excitation. More strikingly, spectroscopic study, X-ray diffraction and DFT calculation reveal the efficient RTP in organic NPs is
originated from dimers in their excited states. The multiple interactions and intermolecular charge transfer in the dimer
structures are of significance in promoting the production of dimer triplet excited states and suppressing the nonradiative
decays to boost the RTP under visible and NIR-light irradiation in water.
However, organic molecules with large π-conjugation that
have the ability to absorb visible light are easy to decay
INTRODUCTION
Room temperature phosphorescence (RTP) from pure
organic compounds has triggered tremendous research
efforts owing to their unique generation processes, long
nonradiatively through excited states and thereby resulting
1
0
in poor radiative performance.
Although molecular
interactions such as strong coupling in H-aggregates,
halogen bonding and intermolecular electronic coupling
1
lifetime and low cost. However, production of RTP from
pure organic molecules is difficult because of the inefficient
intersystem crossing (ISC) from singlet to triplet excited
state, the spin-forbidden radiative transitions from triplet
excited state to singlet ground state (phosphorescence), easy
nonradiative relaxation from low-lying triplet excited states
and collisional quenching by oxygen. Over the past several
3
a, 8b, 11, 12
have been introduced to improve RTP in solid state,
it is yet to illustrate the emissive species of RTP in-depth,
especially at supramolecular level for self-assembled organic
compounds.
2
years, two approaches have been put forward to obtain RTP
3
from organic molecules: (1) introduction of heavy atom, or
4
aromatic carbonyl groups to facilitate ISC and therefore
5
radiative phosphorescence; (2) use of host-guest doping,
6
7
polymerization, metal-organic framework coordination,
8
and rigid crystal formation to restrict the vibration of
organic molecules and suppress the nonradiative decay.
Following these approaches, most RTP are currently
achieved in solid state under ultraviolet (UV) light excitation.
It is realized that bulk solid organic materials cannot be
dispersed in aqueous solution to penetrate in cell
Scheme 1. The molecular structures of compounds H-
9
membrane. Meanwhile, UV light has much phototoxicity
2 2 2
NpCzBF , Br-NpCzBF and I-NpCzBF ; General Jablonski
diagram illustrating the production of visible and NIR light
triggered RTP from the exquisite dimer in NPs.
and lower penetrability for cell and tissues. Visible and near-
infrared (NIR) light are ideal alternative excitation light.
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Herein, we present the first example of bright RTP under
visible and NIR light irradiation in water. Our design is based
on difluoroboron β-diketonate compounds (BF bdk) (H-
NpCzBF , Br-NpCzBF and I-NpCzBF , Scheme 1), in which
difluoroboron is expected to act as an electron-accepting
group and carbazole as a strong electron-donating unit. The
intramolecular/intermolecular charge transfer from the
donor to the acceptor is anticipated to shift the absorption to
hydrodynamic diameters of the NPs determined by dynamic
light scattering (DLS) measurements (Figure 1a and S3).
These NPs remained stable in water even after storage for 2
weeks at room temperature (Figure S4).
2
2
2
2
Importantly, the NPs exhibited intense RTP under visible
light excitation in aqueous solution. Phosphorescence
spectra were recorded by gated measurement with a delay
time of 0.1 ms after excitation. Taken BrNPs as an example,
upon visible light irradiation at 470 nm, the emission spectra
of BrNPs in aqueous solution display fluorescence centered
2
visible light region. Moreover, BF bdk derivatives possess
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13
large two-photon absorption (TPA) cross sections, it is
therefore possible to achieve RTP via two-photon NIR light
excitation. As mentioned above, the introduction of bromine
(Br) and iodine (I) on naphthalene is capable of facilitating
spin-orbital coupling to enhance the ISC rate, thereby
populating the triplet excited states. To our delight, the
assembled organic nanoparticles (NPs) of the three
compounds show RTP in water under visible and NIR-light
excitation at ambient conditions. More importantly, for the
first time, we identify that the efficient RTP in these
assemblies is derived from the dimer pair in excited state
at 620 nm (τ
F
= 9.25 ns) and phosphorescence centered at
6
36 nm (τ = 27.6 μs) at ambient condition. The redshift
P
emission and long lifetime further confirmed the
phosphorescence characteristics. Similar phosphorescence
P P P
spectra of HNPs (λ = 625 nm, τ = 29.0 μs) and INPs (λ =
628 nm, τ = 17.2 μs) with BrNPs under ambient conditions
P
were observed (Figure 1c-d, and Table 1). Owing to the
stronger heavy atom effect of iodine over bromine, less
intense fluorescence and shorter lifetimes of INPs (τ = 3.03
F
ns) than those of BrNPs
2
rather than from the monomer of BF bdk itself. The results
presented not only provide a new model for in-depth
understanding of the RTP emissive species, but also extend
the RTP from solid state under UV light excitation to
aqueous solution under visible and NIR-light excitation.
RESULTS AND DISCUSSION
Difluoroboron β-diketonate derivatives were readily
synthesized by a two-step reaction from acetyl carbazole
1
derivatives and naphthoic acid methyl esters (Scheme S1). H
13
and C NMR spectroscopy, HR-MS and single-crystal X-ray
diffraction revealed their structures with high purity (See
Supporting Information for details). The compounds
displayed visible absorption peak centered at ~455 nm (with
-1
-1
ε over 70000 M cm ) (Figure 1b). The bathochromic shifts of
fluorescence over 80 nm with increasing solvent polarity
from toluene to methanol suggest the intramolecular charge
transfer (ICT) character of (X)-NpCzBF
2
type molecules
1
4
Figure 1. (a) SEM image of BrNPs. (b) Normalized UV
absorption spectra of (X)-NpCzBF in THF (black line) and
(
Figure S1 and Table S1-3). Their self-assembled organic
2
nanoparticles were prepared by nanoprecipitation method in
solvent/antisolvent medium upon sonication.15 By adjusting
the ratio of THF/water, well-dispersed assembled NPs of H-
HNPs, BrNPs, INPs (red line). (c) Phosphorescence decays of
HNPs, BrNPs and INPs under ambient conditions. (d)
Normalized fluorescence spectra of (X)-NpCzBF
room temperature (black line, c = 10 μM), phosphorescence
spectra of (X)-NpCzBF in 2-MTHF at 77 K (blue line) and
2
in THF at
NpCzBF
2
(HNPs), Br-NpCzBF
2
(BrNPs) and I-NpCzBF
2
(
INPs) in aqueous solution were obtained (See Supporting
2
Information for details). The XRD of the NPs showed typical
amorphous patterns (Figure S2). The average diameters of
the HNPs, BrNPs and INPs observed by scanning electron
microscopy (SEM) are approximately 105, 85 and 110 nm,
respectively. They are slightly smaller than the average
RTP spectra of HNPs, BrNPs, INPs. (λex = 470 nm, delayed
time: 0.1 ms, c = 1 mM) (red line).
Table 1. The lifetime and quantum yield of the three compounds in THF, as powder and nanoparticles.
compound
THF
Powder
NPs
a
b
τFa
φc
λFa
λPa
τFa
τPa
φc
λFa
λPa
a
τPa
d
φc
λ
F
λ
P
τ
F
τ
P
nm) (nm) (ns)
(
%) (nm) (nm) (ns) (ms) (%) (nm) (nm)
(ns)
(μs)
(μs)
(%)
(
H-NpCzBF
Br-NpCzBF
I-NpCzBF
2
523
533
530
556
570
574
3.49 41.0
2.56 26.0
2.29 24.0
631
558
556
640 37.10 0.13 36.2
610
620
622
625
636
628
25.54 29.0 51.6 23.1
9.25 27.6 34.5 6.5
2
647
655
1.21
0.58 25.9
7.4
2
0.83 0.56
3.03
17.2 25.9 3.6
[a] at rt under air; [b] at 77 K; [c] Total photoluminescence quantum yield at rt under air; [d] at rt under nitrogen.
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were observed. Not surprisingly, the phosphorescence
intensity and lifetime of NPs were enhanced dramatically
after purging with nitrogen (Figure S5 and Table 1).
condition. To shed more light on the RTP, we compared the
fluorescence spectra of the compounds in NPs with those in
THF and solid state at room temperature. Notably, HNPs,
BrNPs and INPs exhibited largely red-shifted, broad and
structureless fluorescence, which were totally different from
those of the monomer in THF (523, 533 and 530 nm) (Figure
We also achieved RTP of HNPs, BrNPs and INPs under
NIR excitation. The (X)-NpCzBF
maximal emission by femtosecond laser excitation among
80-820 nm (Figure S6). Upon excitation at 820 nm, these
2
were found to reach
1
d and S9). The emission color changed from THF to NPs
7
were evidenced by eye when irradiated by hand-held 365 nm
UV light (Figure S10). Moreover, their fluorescence lifetimes
NPs in aqueous solution emit brightly with the similar band
shape and position as the emissions excited by 470 nm. After
purging with nitrogen, the emission intensity of RTP was
greatly enhanced (Figure S7). The quadratic dependence
between the laser powers and emission intensities
demonstrate the two-photon excitation process (Figure 2a-b
and S8). With the simple and water-dispersible NPs, cellular
imaging experiment was performed to examine the potential
applications of the NPs in bioimaging by a confocal laser
scanning microscopy (CLSM). The confocal images of HeLa
cells after incubation with BrNPs for 4 h are shown in Figure
1
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(
τ
F
= 25.54, 9.25, and 3.03 ns) were much longer than those in
THF solutions (τ = 3.49, 2.26 and 2.29 ns) (Figure S11). The
F
largely red-shifted fluorescence spectra and long lifetimes of
the NPs suggest the possible formation of new emissive
1
6, 17
species.
were red-shifted greatly as compared with that of monomer
in THF, indicating that the associated BF bdk chromophores
at the ground states might be responsible for the new
The excitation spectra of the fluorescence in NPs
2
1
8
emissive
species
(Figure
S12a).
Besides,
the
phosphorescence profiles of the NPs were different from
those of three compounds in dilute solution of 2-
methyltetrahydrofuran (2-MTHF) at 77 K. The typical
2
. Emissions in green (500-550 nm) and red (570-620 nm)
channels upon excitation by a 488 nm laser and an 820 nm
femtosecond pulsed laser light were observed respectively,
indicating that the NPs passed across the cell membrane and
entered in the cell cytoplasm. Clearly, the two-photon
excitation allows for using the RTP of self-assembled
nanoparticles in biological system by NIR light irradiation,
which possesses lower phototoxicity and higher penetrability
for cells and tissues.
monomeric phosphorescence of BF
2
bdk (556, 570 and 574
) in 2-MTHF
nm for H-NpCzBF , Br-NpCzBF , I-NpCzBF
2
2
2
shifted to lower energy by about 54-69 nm for NPs at room
temperature (Figure 1d, S13 and Table 1), further suggesting
that the RTP of the NPs is originated from the associated
molecules rather than from the isolated molecules. Possibly
due to the same reason, solid powder of these three
compounds exhibited very similar RTP as those of NPs (H-
NpCzBF
nm, τ = 0.53 ms; I-NpCzBF
Figure S14). It is worth noting that this kind of emission
2
: λ
P
= 640 nm, τ
P
= 0.13 ms; Br-NpCzBF
2 P
: λ = 647
P
2
: λ = 655 nm, τ = 0.56 ms)
P
P
(
could only be obtained in NPs and solid powder as no
phosphorescence was detectable even at very high
concentration of (X)-NpCzBF
Single-crystal structures of Br-NpCzBF
were obtained and revealed that the adjacent molecules are
in close proximity. As shown in Figure 3, Br-NpCzBF and I-
NpCzBF adopt compact head-to-tail anti-parallel
2
in THF (Figure S12b).
2
and I-NpCzBF
2
2
2
arrangement and exhibit strong multiple interactions in the
spatially isolated dimers in crystal structure. Strong
interlayer interaction between naphthyl and carbazole group
(
3.365 and 3.346 Å) in the dimeric structures, taking Br-
NpCzBF as example, were evidenced by their short
distances. The dihedral angle between two molecules in (X)-
NpCzBF dimers are close to 0°. In these dimers, NPs lock the
2
2
molecular conformation, restrict the molecular vibration and
decrease oxygen quenching, thus reducing the nonradiative
transition of triplet excitons to boost RTP under ambient
condition (Tables S4).
Figure 2. (a) The emission spectra of BrNPs excited at 470
nm (black line) and 820 nm (red line). (b) The emission
spectra and the logarithmic plots of the emission integral of
BrNPs at different excitation intensities (mW) by an 820 nm
femtosecond pulsed laser light. (c-h) Confocal luminescence
images of HeLa cells incubated with BrNPs (c = 1 μM in
water). The excitation wavelengths were 488 nm (c, d) and
The excited-state transition configuration calculation of
the monomeric and dimeric structures of Br-NpCzBF
2
and I-
NpCzBF derived from single-crystal structures were carried
2
out based on TD-DFT method with B3LYP functional and 6-
31G* (LANL2DZ for I) basis set (See Supporting Information
8
20 nm (f, g), respectively. (e) Bright field image of HeLa
3a, 4d, 19, 20
for details, Figure 3 and Table S5-8).
For isolated
cells corresponding to (c) and (d). (h) Bright field image of
(
X)-NpCzBF molecule, obvious intramolecular charge
2
HeLa cells corresponding to (f) and (g). Scale bar: 10 μm.
transfer from carbazole to dioxaborine ring were observed in
their
The observation of RTP in the NPs are in sharp contrast
with the absence of phosphorescence in THF under ambient
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Figure 3. The intermolecular packing in Br-NpCzBF
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(a) and I-NpCzBF (b) crystal; the energy levels of monomer and dimer of
Br-NpCzBF (a) and I-NpCzBF (b) based on TD-B3LYP/6-31G* calculations.
2
2
transition configurations and isosurfaces of the highest
occupied molecular orbital (HOMO) and the lowest
unoccupied molecular orbital (LUMO). In the dimeric
structures, however, a new intermolecular charge transfer
from an occupied orbital of one to the vacant orbital of
neighboring molecule was observed instead (Figure S15). The
dimers, which can act as energy trap and collect all the
excited energy from excited molecules, would increase the
ISC channels between S and T states, decrease the ΔEST, and
enable multiple intermolecular interactions for the
occurrence of efficient RTP in the NPs. No RTP was observed
in the NPs prepared by carbazole derivative under similar
condition, supporting the important role of multiple
interactions and intermolecular charge transfer of (X)-
2 2
dipole moments for Br-NpCzBF and I-NpCzBF dimer were
calculated to be 13.15 and 12.78 Debye respectively, which
were enhanced dramatically compared with their isolated
monomers (9.59 and 9.80 Debye), suggesting the presence of
intermolecular charge transfer in the dimer structures.
Significantly, the energy level of the singlet and triplet
excited state in the dimer decreased dramatically as
compared with isolated monomer, thus resulting in
significant intermolecular ISC channels and enhanced ISC
2
NpCzBF in dimer structures (Figure S16).
CONCLUSION
In summary, we have developed self-assembled organic
nanoparticles from difluoroboron β-diketonate compounds
in water, which show bright RTP, effective uptake and bright
imaging of HeLa cells under both visible and NIR-light
excitation. Spectroscopic analysis, DFT calculation and single
crystal structure analysis demonstrate the RTP in NPs is
originated from the dimeric excited states of the compounds.
The multiple interactions and intermolecular charge transfer
in the dimeric structures are effective in facilitating the ISC
and reducing nonradiative decays, thus boosting RTP of the
NPs. This is the first study, to the best of our knowledge, to
expand pure organic RTP to visible and NIR light excitation
in aqueous solution. A simple dimer formation strategy
demonstrated here not only opens a window for in-depth
understanding the nature of RTP from self-assembled pure
organic compounds, but also allows for the development of
bright RTP from pure organic phosphors under visible and
NIR light irradiation for practical applications in aqueous
media.
process. In the monomer structure of Br-NpCzBF
is merely one minor transition contribution from S
→ T ) for ISC transition, while there are two major ISC
channels (S →T , T ) observed in the dimer structures (Table
S5-S6). Furthermore, the calculated energy gap between the
lowest singlet and triplet excited state of dimer (Br-NpCzBF
ΔEST = 0.32 eV; I-NpCzBF : ΔEST = 0.31 eV) were considerably
smaller than those of the monomers (Br-NpCzBF : ΔEST
.67 eV; I-NpCzBF : ΔEST = 0.62 eV). According to the
2
, e.g., there
1
to T (S
4
1
4
1
3
5
2
:
2
2
=
0
2
perturbation theory, the decreased energy gap would favor
the spin-orbit coupling between singlet-triplet states in the
dimer structures, thus leading to increased radiative rate
6a, 21, 22
constant from T
1
0
to S .
Most recently, Shuai and Peng
23
et al proposed a pair of molecular descriptors (γ and β),
related to the portion of (n, π*) transition and (π, π*)
transition of molecular orbitals in lowest-lying singlet and
triplet excited state, to precisely characterize RTP efficiency
and lifetime through computational calculations. Taking all
aforementioned into account, excitation to the singlet
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
2
excited state of (X)-NpCzBF can be followed by the
formation of a stabilized dimer excited states with the nearby
preorganized ground state molecule. These lower energy
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Publications
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Experimental details, synthetic and preparation details, cell
culture, calculations, single crystal data and others (PDF)
D.; Lu, F.; Wang, J.; Hu, W.; Cao, X. M.; Ma, X.; Tian, H. Amorphous
metal-free room-temperature phosphorescent small molecules with
multicolor photoluminescence via a host-guest and dual-emission
strategy. J. Am. Chem. Soc. 2018, 140, 1916. (c) Ventura, B.; Bertocco,
A.; Braga, D.; Catalano, L.; d’Agostino, S.; Grepioni, F.; Taddei, P.
Luminescence properties of 1,8-naphthalimide derivatives in
solution, in their crystals, and in co-crystals: toward room-
temperature phosphorescence from organic materials. J. Phys. Chem.
C 2014, 118, 18646. (d) Kuila, S.; Rao, K. V.; Garain, S.; Samanta, P.;
Das, S.; Pati, S. K. George, S. J. Aqueous phase phosphorescence:
ambient triplet harvesting of purely organic phosphors via
supramolecular scaffolding. Angew. Chem. Int. Ed. 2018, 57, 17115. (e)
Ono, T.; Taema, A.; Goto, A.; Hisaeda, Y. Switching of monomer
fluorescence, charge-transfer fluorescence, and room-temperature
AUTHOR INFORMATION
Corresponding Author
*chenyuzhe@mail.ipc.ac.cn; *lzwu@mail.ipc.ac.cn
Notes
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The authors declare no competing financial interests.
ACKNOWLEDGMENT
Financial support from the National Natural Science
Foundation of China (21871280 and 21525206), the Ministry of
Science and Technology of China (2017YFA0206903), the
Strategic Priority Research Program of the Chinese Academy
of Sciences (XDB17000000), the Key Research Program of
Frontier Sciences of the Chinese Academy of Sciences
phosphorescence induced by aromatic guest inclusion in a
supramolecular host. Chem. Eur. J. 2018, 24, 17487.
(6) (a) Zhang, G.; Palmer, G. M.; Dewhirst, M. W.; Fraser, C. L. A
dual-emissive-materials design concept enables tumour hypoxia
imaging. Nat. Mater. 2009, 8, 747. (b) Chen, X.; Xu, C.; Wang, T.;
Zhou, C.; Du, J.; Wang, Z.; Xu, H.; Xie, T.; Bi, G.; Jiang, J.; Zhang, X.;
Demas, J. N.; Trindle, C. O.; Luo, Y.; Zhang, G. Versatile room-
temperature-phosphorescent materials prepared from N-substituted
naphthalimides: emission enhancement and chemical conjugation.
Angew. Chem. Int. Ed. 2016, 55, 9872. (c) Kwon, M. S.; Yu, Y.;
Coburn, C.; Phillips, A. W.; Chung, K.; Shanker, A.; Jung, J.; Kim, G.;
Pipe, K.; Forrest, S. R.; Youk, J. H.; Gierschner, J.; Kim, J. Suppressing
(
QYZDY-SSW-JSC029), K. C. Wong Education Foundation
are gratefully acknowledged. The authors thank Dr. Ye Tian
TIPC) for providing HeLa cells, Prof. Yong Chen (TIPC) for
(
his helpful discussions.
molecular
phosphorescence of metal-free organic materials. Nat. Commun.
015, 6, 8947. (d) Ma, X.; Xu, C.; Wang, J.; Tian, H. Amorphous pure
motions
for
enhanced
room-temperature
REFERENCES
2
(
1) (a) Xu, S.; Chen, R.; Zheng, C.; Huang, W. Excited state
organic polymers for heavy-atom-free efficient room-temperature
phosphorescence emission. Angew. Chem. Int. Ed. 2018, 57, 10854. (e)
Tao, S.; Lu, S.; Geng, Y.; Zhu, S.; Redfern, S. A. T.; Song, Y.; Feng, T.;
Xu, W.; Yang, B. Design of metal-free polymer carbon dots: a new
class of room-temperature phosphorescent materials. Angew. Chem.
Int. Ed. 2018, 57, 2393. (f) Ogoshi T, T. H., Kakuta T, Yamagishi T-A,
Taema A, Ono T, Sugimoto M, Mizuno, M. Ultralong room-
temperature phosphorescence from amorphous polymer poly
(styrene sulfonic acid) in air in the dry solid state Adv. Funct. Mater.
modulation for organic afterglow: materials and applications. Adv.
Mater. 2016, 28, 9920. (b) Baroncini, M.; Bergamini, G.; Ceroni, P.
Chem.
Commun.
Rigidification
or
interaction-induced
phosphorescence of organic molecules. 2017, 53, 2081. (c) Forni, A.;
Lucenti, E.; Botta, C.; Cariati, E. Metal free room temperature
phosphorescence from molecular self-interactions in the solid state.
J. Mater. Chem. C 2018, 6, 4603. (d) Mukherjee, S.; Thilagar, P.
Recent advances in purely organic phosphorescent materials. Chem.
Commun. 2015, 51, 10988. (e) Chen, P.-Z.; Chen, Y.-Z.; Tung ,C.-H.;
Yang, Q.-Z. A simple strategy to construct amorphous metal-Free
room temperature phosphorescent and multi-color materials.
ChemPhysChem 2018, 19, 2131.
2
018, 28, 1707369. (g) Jiang, K.; Zhang, L.; Lu, J.; Xu, C.; Cai, C.; Lin,
H. Triple-mode emission of carbon dots: applications for advanced
anti-counterfeiting. Angew. Chem. Int. Ed. 2016, 55, 7231. (h). Wu, H.;
Chi, W.; Chen, Z.; Liu, G.; Gu, L.; Bindra, A. K.; Yang, G.; Liu, X.;
Zhao, Y. Achieving amorphous ultralong room temperature
phosphorescence by coassembling planar small organic molecules
with polyvinyl alcohol. Adv. Funct. Mater. 2018, 1807243.
(
2) Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Principles of
Molecular Photochemistry: An Introduction; University Science Books:
Mill Valley, CA, 2009.
(
3) (a) Yang, Z.; Mao, Z.; Zhang, X.; Ou, D.; Mu, Y.; Zhang, Y.;
(
7) Yang, X.; Yan, D. Long-afterglow metal–organic frameworks:
Zhao, C.; Liu, S.; Chi, Z.; Xu, J.; Wu, Y.-C.; Lu, P.-Y.; Lien, A.; Bryce,
M. R. Intermolecular electronic coupling of organic units for efficient
persistent room-temperature phosphorescence. Angew. Chem. Int.
Ed. 2016, 55, 2181. (b) Mao, Z.; Yang, Z.; Mu, Y.; Zhang, Y.; Wang, Y.
F.; Chi, Z.; Lo, C. C.; Liu, S.; Lien, A.; Xu, J. Linearly tunable emission
colors obtained from a fluorescent-phosphorescent dual-emission
compound by mechanical stimuli. Angew. Chem. Int. Ed. 2015, 54,
reversible guest-induced phosphorescence tunability. Chem. Sci.
2
016, 7, 4519.
(8) (a) Yuan, W. Z.; Shen, X. Y.; Zhao, H.; Lam, J. W. Y.; Tang, L.;
Lu, P.; Wang, C.; Liu, Y.; Wang, Z.; Zheng, Q.; Sun, J. Z.; Ma, Y.;
Tang, B. Z. Crystallization-induced phosphorescence of pure organic
luminogens at room temperature. J. Phys. Chem. C. 2010, 114, 6090.
(
b) Bolton, O.; Lee, K.; Kim, H. J.; Lin, K. Y.; Kim, J. Activating
6270.
efficient phosphorescence from purely organic materials by crystal
design. Nat. Chem. 2011, 3, 205. (c) Yang, J.; Zhen, X.; Wang, B.; Gao,
X.; Ren, Z.; Wang, J.; Xie, Y.; Li, J.; Peng, Q.; Pu, K.; Li, Z. The
influence of the molecular packing on the room temperature
phosphorescence of purely organic luminogens. Nat. Commun. 2018,
9, 840. (d) Wang, J.; Gu, X.; Ma, H.; Peng, Q.; Huang, X.; Zheng, X.;
Sung, S. H. P.; Shan, G.; Lam, J. W. Y.; Shuai, Z.; Tang, B. Z. A facile
strategy for realizing room temperature phosphorescence and single
molecule white light emission. Nat. Commun. 2018, 9, 2963. (e)
Wang, J.; Wang, C.; Gong, Y.; Liao, Q.; Han, M.; Jiang, T.; Dang, Q.;
Li, Y.; Li, Q.; Li, Z. Bromine-substituted fluorene: molecular
structure, Br-Br interactions, room-temperature phosphorescence,
and tricolor triboluminescence. Angew. Chem. Int. Ed. 2018, 57, 16821.
(
4) (a) Xue, P.; Sun, J.; Chen, P.; Wang, P.; Yao, B.; Gong, P.;
Zhang, Z.; Lu, R. Luminescence switching of a persistent room-
temperature phosphorescent pure organic molecule in response to
external stimuli. Chem. Commun. 2015, 51, 10381. (b) Lee, D.; Ma, X.;
Jung, J.; Jeong, E. J.; Hashemi, H.; Bregman, A.; Kieffer, J.; Kim, J. The
effects of extended conjugation length of purely organic phosphors
on their phosphorescence emission properties. Phys. Chem. Chem.
Phys. 2015, 17, 19096. (c) Zhao, W.; He, Z.; Lam, Jacky, W. Y.; Peng,
Q.; Ma, H.; Shuai, Z.; Bai, G.; Hao, J.; Tang, B. Z. Rational molecular
design for achieving persistent and efficient pure organic room-
temperature phosphorescence. Chem. 2016, 1, 592.
(
5) (a) Hirata, S.; Totani, K.; Zhang, J.; Yamashita, T.; Kaji, H.;
Marder, S. R.; Watanabe, T.; Adachi, C. Efficient persistent room
temperature phosphorescence in organic amorphous materials
under ambient conditions. Adv. Funct. Mater. 2013, 23, 3386. (b) Li,
(
f) Wei, J.; Liang, B.; Duan, R.; Cheng, Z.; Li, C.; Zhou, T.; Yi, Y.;
Wang, Y. Induction of strong long-lived room-temperature
phosphorescence of N-phenyl-2-naphthylamine molecules by
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 7
1
2
3
4
5
6
7
8
9
1
1
1
1
1
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1
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2
2
2
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4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
confinement in a crystalline dibromobiphenyl matrix. Angew. Chem.
microrods. Angew. Chem. Int. Ed. 2008, 47, 7301. (b) Zhang, K. D.;
Tian, J.; Hanifi, D.; Zhang, Y.; Sue, A. C.; Zhou, T. Y.; Zhang, L.; Zhao,
Int. Ed. 2016, 55, 15589. (g) Narushima, K.; Kiyota, Y.; Mori, T.;
Hirata, S.; Vacha, M. Suppressed triplet exciton diffusion due to
small orbital overlap as a key design factor for ultralong-lived room-
temperature phosphorescence in molecular crystals. Adv. Mater.
2019, 1807268. (h) Huang, L.; Chen, B.; Zhang, X.; Trindle, C. O.;
Liao, F.; Wang, Y.; Miao, H.; Luo, Y.; Zhang, G. Proton-activated “off–
on” room-temperature phosphorescence from purely prganic
thioethers. Angew. Chem. Int. Ed. 2018, 57,16046.
X.; Liu, Y.; Li, Z. T. Toward
a single-layer two-dimensional
honeycomb supramolecular organic framework in water. J. Am.
Chem. Soc. 2013, 135, 17913. (c) Song, Q.; Jiao, Y.; Wang, Z.; Zhang, X.
Tuning the Energy Gap by Supramolecular Approaches: Towards
Near-Infrared Organic Assemblies and Materials. Small 2016, 12, 24.
(16) (a) Sun, X.; Zhang, X.; Li, X.; Liu, S.; Zhang, G. A mechanistic
investigation of mechanochromic luminescent organoboron
materials. J. Mater. Chem. 2012, 22, 17332. (b) Bilen, C. S.; Harrison,
N.; Morantz, D. J. Unusual room temperature afterglow in some
crystalline organic compounds. Nature 1978, 271, 235.
(17) Situ, B.; Gao, M.; He, X.; Li, S.; He, B.; Guo, F.; Kang, C.; Liu,
S.; Yang, L.; Jiang, M.; Hu, Y.; Tang, B. Z. A two-photon AIEgen for
simultaneous dual-color imaging of atherosclerotic plaques. Mater.
Horiz. 2019, DOI: 10.1039/c8mh01293h.
(18) (a) Chen, Y.-Z.; Wang, X.-F.; Tian, Y.; Guo, W.-J.; Wu, M.;
Wu, L.-Z.; Tung, C.-H.; Yang, Q.-Z.; Niu, Z. Filamentous virus
oriented pyrene excimer emission and its efficient energy transfer. J.
Photochem. Photobiol. A-Chem. 2018, 355, 32. (b) Liu, H.; Yao, L.; Li,
B.; Chen, X.; Gao, Y.; Zhang, S.; Li, W.; Lu, P.; Yang, B.; Ma, Y.
Excimer-induced high-efficiency fluorescence due to pairwise
anthracene stacking in a crystal with long lifetime. Chem. Commun.
2016, 52, 7356. (c) Tung, C.-H.; Wang, Y. Lipophobic effects on
photochemical and photophysical behavior of molecules with polar
chains in nonpolar solvents. Evidence for intermolecular aggregation
and self-coiling. J. Am. Chem. Soc. 1990, 112, 6322. (d) Yan, N.; Xu, Z.;
Diehn, K. K.; Raghavan, S. R.; Fang, Y.; Weiss, R. G. How do liquid
mixtures solubilize insoluble gelators? Self-assembly properties of
pyrenyl-linker-glucono gelators in tetrahydrofuran-water mixtures. J.
Am. Chem. Soc. 2013, 135, 8989. (e) Liu, F.-W.; Niu, L.-Y.; Chen, Y.;
Ramamurthy, V.; Wu, L.-Z.; Tung, C.-H.; Chen, Y.-Z.; Yang, Q.-Z. A
phosphorescent platinum (II) bipyridyl supramolecular polymer
based on quadruple hydrogen bonds. Chem. Eur. J. 2016, 22, 18132.
(19) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria,G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A. Jr.; Vreven, T.;
Kudin, K.; Burant, J. C. Gaussian 09, revision E. 01; Gaussian, Inc.:
Wallingford, CT, 2013.
(20) (a) Wang, Y.; Cong, L.; Li, H.; Shi, Y. TDDFT study of twisted
intramolecular charge transfer and intermolecular double proton
transfer in the excited state of 4'-dimethylaminoflavonol in ethanol
solvent. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2015, 137, 913. (b)
Yang, J.; Gao, X.; Xie, Z.; Gong. Y.; Fang, M.; Peng, Q.; Chi, Z.; Li, Z.
Elucidating the excited state of mechanoluminescence in organic
luminogens with room-temperature phosphorescence. Angew. Chem.
Int. Ed. 2017, 56, 15299.
(21) Lower, S. K., Elsayed, M. A. The triplet state and molecular
electronic processes in organic molecules. Chem. Rev. 1966, 66, 199.
(22) Li, J. A.; Zhou, J.; Mao, Z.; Xie, Z.; Yang, Z.; Xu, B.; Liu, C.;
Chen, X.; Ren, D.; Pan, H.; Shi, G.; Zhang, Y.; Chi, Z. Transient and
persistent room-temperature mechanoluminescence from a white-
light-emitting AIEgen with tricolor emission switching triggered by
light. Angew. Chem. Int. Ed. 2018, 57, 6449.
(
9) (a) Fateminia, S. M. A.; Mao, Z.; Xu, S.; Yang, Z.; Chi, Z.; Liu,
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
B. Organic nanocrystals with bright red persistent room-temperature
phosphorescence for biological applications. Angew. Chem. Int. Ed.
2
017, 56, 12160. (b) Wu, H.; Zhou, Y.; Yin, L.; Hang, C.; Li, X.; Ågren,
H.; Yi, T.; Zhang, Q.; Zhu, L. Helical self-assembly-induced singlet–
triplet emissive switching in a mechanically sensitive system. J. Am.
Chem. Soc. 2017, 139, 785. (c) Zhen, X.; Tao, Y.; An, Z.; Chen, P.; Xu,
C.; Chen, R.; Huang, W.; Pu, K. Ultralong phosphorescence of water-
soluble organic nanoparticles for in vivo afterglowimaging. Adv.
Mater. 2017, 29, 1606665. (d) Fateminia, S. M.; Wang, Z.; Goh, C. C.;
Manghnani, P. N.; Wu, W.; Mao, D.; Ng, L. G.; Zhao, Z.; Tang, B. Z.;
Liu, B. Nanocrystallization: a unique approach to yield bright organic
nanocrystals for biological applications. Adv. Mater. 2017, 29,
1
604100.
10) Wohlgenannt, M.; Vardeny, Z. V. Spin-dependent exciton
formation rates in π-conjugated materials. J. Phys.: Condens. Matter.
(
2
003, 15, 83.
(11) (a) An, Z.; Zheng, C.; Tao, Y.; Chen, R.; Shi, H.; Chen, T.;
Wang, Z.; Li, H.; Deng, R.; Liu, X.; Huang, W. Stabilizing triplet
excited states for ultralong organic phosphorescence. Nat. Mater.
2
015, 14, 685. (b) Lucenti, E.; Forni, A.; Botta, C.; Carlucci, L.;
Giannini, C.; Marinotto, D.; Pavanello, A.; Previtali, A.; Righetto, S.;
Cariati, E. Cyclic triimidazole derivatives: intriguing cases of multiple
emissions and RT ultralong phosphorescence. Angew. Chem. Int. Ed.
2
017, 56, 16302. (c) Gu, L.; Shi, H.; Gu, M.; Ling, K.; Ma, H.; Cai, S.;
Song, L.; Ma, C.; Li, H.; Xing, G.; Hang, X.; Li, J.; Gao, Y.; Yao, W.;
Shuai, Z.; An, Z.; Liu, X.; Huang, W. Dynamic ultralong organic
phosphorescence by photoactivation. Angew. Chem. Int. Ed. 2018, 57,
8425.
(
12) Fu, H.; Xiao, L. Enhanced room-temperature
phosphorescence through intermolecular halogen/hydrogen-
bonding. Chem. Eur. J. 2019, 25, 714.
(
13) (a) Cogné-Laage, E.; Allemand, J.-F.; Ruel, O.; Baudin, J.-B.;
Croquette, V.; Blanchard-Desce, M.; Jullien, L. Diaroyl (methanato)
boron difluoride compounds as medium-sensitive two-photon
fluorescent probes. Chem. Eur. J. 2004, 10, 1445. (b) Chen, P.-Z.;
Wang, J.-X.; Niu, L.-Y.; Chen, Y.-Z.; Yang, Q.-Z. Carbazole-containing
difluoroboron β-diketonate dyes: two-photon excited fluorescence in
solution and grinding-induced blue-shifted emission in the solid
state. J. Mater. Chem. C 2017, 5, 12538.
(
14) (a) Meier, H. Conjugated oligomers with terminal donor-
acceptor substitution. Angew. Chem. Int. Ed. 2005, 44, 2482. (b)
Chen, P.-Z.; Weng, Y.-X.; Niu, L.-Y.; Chen, Y.-Z.; Wu, L.-Z.; Tung, C.-
H.; Yang, Q.-Z. Light-harvesting systems based on organic
nanocrystals to mimic chlorosomes. Angew. Chem. Int. Ed. 2016, 55,
(23) Ma, H.; Peng, Q.; An, Z.; Huang, W.; Shuai, Z. Efficient and
long-lived room-temperature organic phosphorescence: theoretical
descriptors for molecular designs. J. Am. Chem. Soc. 2019, 141, 1010.
2
759.
15) (a) Zhao, Y. S.; Xu, J.; Peng, A.; Fu, H.; Ma, Y.; Jiang, L.; Yao, J.
Optical waveguide based on crystalline organic microtubes and
(
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