Synthesis and photophysical properties of multilayer emitting π-p-π fluorophores

Article abstract of DOI:10.1016/j.saa.2019.117680

Fluorescence is widely used in biology, medicine, and analytical chemistry. The anthracene framework has received considerable attention for the luminescent molecular design as an attractive building unit. Herein, Luminescent “π-p-π” anthracene crystals with different multilayer stacking modes were conducted by experimental methods and theoretical calculations. It was found that “these anthracene derivatives showed strong fluorescence and stability in both solution and solid-state; A face-to-face π-π stacking arrangement dominated in N⁹,N¹⁰-diphenyl-2,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-diamine (4), while C/N–H … π interactions were observed in the crystal lattice of 2,6-diethynyl-N⁹,N¹⁰-diphenylanthracene-9,10-diamine (5); The excitation processes of S₀→S₁ of 4 and 5 belonged to Localized Excitation; The number of photons emitted could be nearly equal to the number of photons absorbed below 120K”. This study is expected to assist in the design of photonic materials in the field of optical chemistry.

Full text of DOI:10.1016/j.saa.2019.117680

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 227 (2020) 117680
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and photophysical properties of multilayer emitting
p-p-p
fluorophores
a
,
b
,
**
a
c
d, *
Xiaorong Wang
, Sanxiao Zhao , Yin Chen , Jingang Wang
a
College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning Shihua University, Fushun, Liaoning, 113001, China
State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan, 610065, China
State Key Laboratory of Trauma, Burns and Combined Injury, Institute of Combined Injury of PLA, Chongqing Engineering Research Center for
b
c
Nanomedicine, College of Preventive Medicine, Third Military Medical University, Chongqing, 400038, PR China
d
Computational Center for Property and Modification on Nanomaterials, College of Science, Liaoning Shihua University, Fushun, 113001, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 June 2019
Received in revised form
Fluorescence is widely used in biology, medicine, and analytical chemistry. The anthracene framework
has received considerable attention for the luminescent molecular design as an attractive building unit.
Herein, Luminescent “
ducted by experimental methods and theoretical calculations. It was found that “these anthracene de-
rivatives showed strong fluorescence and stability in both solution and solid-state; A face-to-face
p-p-p” anthracene crystals with different multilayer stacking modes were con-
4
October 2019
Accepted 18 October 2019
Available online 20 October 2019
p-p
9
10
stacking arrangement dominated in N ,N -diphenyl-2,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-
diamine (4), while C/NeH … interactions were observed in the crystal lattice of 2,6-diethynyl-
N ,N -diphenylanthracene-9,10-diamine (5); The excitation processes of S /S of 4 and 5 belonged to
p
Keywords:
9
10
0
1
Anthracene
Stacking arrangement
DFT
Luminescence
Excitation
Localized Excitation; The number of photons emitted could be nearly equal to the number of photons
absorbed below 120K”. This study is expected to assist in the design of photonic materials in the field of
optical chemistry.
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
excitation energy of fluorophores is not easily lost in non-radiation
ways; (2). The stacking conjugated system or substituents could
As an attractive building unit, the anthracene framework has
received considerable attention for the luminescent molecular
design of new optical materials [1-2]. Notably, these anthracene
derivatives generated based on organic synthesis show intriguing
luminescent properties and different stacking modes, which have
been widely used in fluorescent coatings, fluorescent pigments,
fluorescent probes, and organic light-emitting diodes [3-4].
Subtle changes in the structure of organic fluorophores can
exert dramatic influences on the crystal stacking mode and
furthermore tune the photophysical properties [5-6]. (e.g., 1).
shift the emission peak [8]. In general, the larger the conjugated
stacking system is or the stronger the electron-donating sub-
stituents (-NH , eOH, eOCH , etc.) are, the higher the HOMO of
2 3
molecules will be and the smaller the energy gap between HOMO
and LUMO will be. When the gap is reduced, the electron-donating
ability of the compound increases, and the electrons are prone to
transit to the excited states. The UV-Vis absorption peak shifts to-
ward the longer wavelength. Due to the Stokes shift [9], the emis-
sion peak is correspondingly located in the longer wavelength.
Thus, changing the structures utilizing organic synthesis is an
effective way for researchers to obtain the materials with multi-
functional properties. Current research on anthracene derivatives
indicates that different structures have different intermolecular
forces, resulting in interesting arrangements with colorful fluo-
rescence properties [10-11]. Therefore, more anthracene de-
rivatives need to be designed and synthesized to investigate the
molecular stacking modes and the photophysical properties which
Anthracene derivatives have an extensive
p conjugation or strong
intramolecular/intermolecular interactions [7]. The increase of
conjugation or the enhancement of intramolecular /intermolecular
interactions will weaken the vibration of molecules so that the
*
Corresponding author.
*
* Corresponding author. College of Chemistry, Chemical Engineering and Envi-
have not been scientifically clarified in detail.
ronmental Engineering, Liaoning Shihua University, Fushun, Liaoning, 113001,
China.
-extended anthracene fluorophores N ,N10-
9
In this study,
p
diphenyl-2,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-diamine
E-mail addresses: wangxiaorong@lnpu.edu.cn (X. Wang), jingang_wang@lnpu.
9
10
(
4) and 2,6-diethynyl-N ,N -diphenylanthracene-9,10-diamine (5)
edu.cn (J. Wang).
https://doi.org/10.1016/j.saa.2019.117680
1386-1425/© 2019 Elsevier B.V. All rights reserved.

2
X. Wang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 227 (2020) 117680
possessing different multilayer structures were designed in the
solid-state (Scheme 1). The Fluorophores involved in this paper
anthraquinone diimine showed nonplanar with a dihedral angle
q
ꢀ
of 151 , leading to the distortion of the skeleton and the difference
1
were
in the longitudinal direction across N atom, thereby creatively
achieving -p- cross conjugation for intramolecular as a whole,
and they also realized or C/NeH$$$ interactions for inter-
p-
p
conjugation in the lateral direction and p-
p
conjugation
in chemical shift of H at each position. Thus, the H NMR spectrums
for 3a-3d were more complicated, which were all consistent with
their molecular symmetry.
p
p
p
-p
p
Crystals of 3b, 4, and 5 suitable for X-ray analysis were obtained
molecular to build different multilayered structures. The synthesis
method was simple and easy, and these anthracene derivatives
showed strong fluorescence and stability in both solution and the
solid-state. Therefore, they could be applied to the fields of fluo-
rescent probes, optical information recording, and organic light-
emitting materials.
2 2
from a hexane/CH Cl mixed solution by the vapor diffusion
method, and all structures were solved and refined using the
Bruker SHELXTL Software Package (Fig. 1). The X-ray data for 4 and
5 revealed that each 2,6-diethynyl-anthracene in monomers
exhibited a coplanar structure. (1) Anthracene derivative of 4 dis-
played
p-p packing arrangements in the crystal lattice, forming a
tetramer with 4-layer packing arrangement as shown in Fig.1B. The
distance between individual molecular planes was approximately
2
. Experimental details
equal, ~3.48 Å, which was a typical face-to-face
p-p stacking, and
from the side view of 4-tetramer under the Cartesian axes in Fig.1B,
the overlap ratio was estimated to be 50% approximately as a
displacement occurred between every two anthracene units [13].
2
,6-dibromo-9,10-anthraquinone (1) and 2-ethynylanthracene-
9
[
2
,10-dione (2) were prepared according to literature procedures
12]. The synthesis procedures of (9Z,10Z)-N ,N -di(4-R-phenyl)-
,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-diimine(3),
9
10
(2) By contrast, a crystal of 5 exhibited a herringbone arrangement
9
10
(Fig. 1C) after the TMS group was removed from 4, wherein the
monomers were arranged in an edge-to-face manner aided by
N ,N -diphenyl-2,6-bis((trimethylsilyl)ethynyl)anthracene-9,10-
9
10
diamine (4) and 2,6-diethynyl-N ,N -diphenylanthracene-9,10-
diamine (5) were given in the supporting information. All flasks
were dried under a flame to eliminate moisture. All solvents were
distilled from appropriate drying agents. All other reagents were
used as received.
CeH$$$
with three adjacent ones through three C/NeH$$$
The distances were 3.03 Å (CeH$$$ ), 3.08 Å (CeH$$$
NeH$$$ ) respectively.
p
interactions [14]. Every monomer of 5 was associated
interactions.
), and 3.15 Å
p
p
p
(
p
To synthesize the target anthracene derivatives, compound 3a-
d was prepared from the precursor 2 [12] in the presence of TiCl
good yields; Compound 4 was the reductive form of 3a, it could be
obtained by using a mild method (Zn dust/ NH Cl); The depro-
tection of 4 with K CO led to 5(Scheme 1). The structures of 3b, 4
and 5 were all confirmed by X-ray crystallography (ESIy). Both 4 and
were strong luminescent in solid-state and solution. All new
4
in
3
. Results and discussion
4
3.1. Optical properties
2
3
Due to the presence of imine bonds which caused charge
transfer during excitation(based on the crystal data of 3b, the C]N
5
1
13
compounds were characterized by H NMR, C NMR, HRMS,
Raman as well as IR. According to the X-ray data of 3b (Fig. 1A), the
Fig. 1. (A): ORTEP representation of 3b,
the 4-phenyl unit with the plane made by the anthraquinone-imine,
b
was the dihedral angle made by the plane of
was the dihedral
q
Scheme 1. Synthesis of 2, 3, 4 and 5. (i) CuI, THF/Et
3
N, Me
3
SiC^CH, Pd(PPh
3
)
2
Cl
CO
2
,
,
angle formed between the average planes of anthracene; (B): The crystal stacking form
(4 layers, side view) of compound 4; (C): The crystal stacking form of 5. H was deleted
for clarity.
ꢀ
65
C, 16 h. (ii) TiCl
4
, DABCO, reflux, 12 h (iii) Zn dust, NH
4
Cl, THF, 5 h. (iv) K
2
3
MeOH/THF (1:1), 12 h.

X. Wang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 227 (2020) 117680
3
ꢀ
bond length of 3b was 1.28, and the dihedral angle
b
was 56
radiation process was increased; That is, the fluorescence intensity
could be enhanced. The fluorescence intensity of 120K was ~5 times
compared to that of 300k. The absolute fluorescence quantum yield
of 300K was 20.1%. As a result, this value could reach ~100% below
120K, that is to say, the number of photons emitted by 4 at low
temperature could be equal to the number of photons absorbed.
The decay curve of 4 applied to the double exponential function
(Fig. 2D) Thus, Compound 4 had two fluorescence lifetimes at
different temperatures as shown in Table 1. As the temperature
decreased, both of the two fluorescence lifetimes increased, but the
proportion of the first lifetime decreased gradually (72%/39%,
300K/80K), and the percentage of the corresponding second
lifetime Increased (28% / 61%, 300K / 80K). Thus, the tempera-
ture had significant effects on the fluorescent properties of this
compound.
reflecting the possible presence of charge transfer), the absorption
band of compound 3 was in the visible range of 360e600 nm, and
larger conjugated system or electron-donating group could cause
the HOMO-LUMO energy gap to become smaller, thus the UV-Vis
absorption spectra of 3b/3c had a certain redshift relative to that
of 3a/3d(Fig. S23). The spectroscopic data were summarized in
Table S4.
The absorption and emission spectra of compounds 4 and 5
were recorded in THF at 298K (Fig. 2). Compound 4 had two main
absorption bands, which were located at 250e340 nm (
88 nm, S / S ) and 410e550 nm ( max 464 nm, S /S ). The
stronger absorption band at 250e340 nm mainly stemmed from
p/ * (N-Ph) and * processes generated by the mono-phenyl
ring; The weaker absorption band of the visible region was attrib-
uted to the -conjugation of 2,6-diethynyl-anthracene over the
l
max
2
0
2
l
0
1
p
p/p
p
The absolute fluorescence quantum yield of 5 at 300K was 24.7%
which was higher than that of 4, and the fluorescence spectrum at
220K, 240K, 260K, 280K, 300 K were shown in Fig. S38 (The trend
was similar as that of 4). Thus, the remove of trimethylsilyl group
and lower temperature could weaken the vibration to increase the
intensity of emission.
entire molecule via the N atom. The emission peak of 4 was
observed at 580 nm in diluted solution (Fig. 2A), and the relative
fluorescence quantum yield was 14.3% using fluorescein (0.1 M
NaOH solution) [15] as a standard (Table 1). We also checked the
emission properties of 4 in different solvents and found it was
insensitive to solvent polarity.
The photophysical properties of 5 were similar to that of 4. The
3.2. Theoretical calculations
absorption peak (S
sion peak was located at 572 nm, which had a small blue shift
10 nm with respect to that of 4 at the same condition (Fig. 2B). This
was because the electron-donating effect did not exist in com-
pound 5 since the trimethylsilyl group was removed. The relative
fluorescence quantum yield of 5 was 18.7%, which was the same
order of magnitude as 4.
At the same time, we found that 4 and 5 exhibited strong
luminescent properties in both solution and solid states. In order to
study the effect of temperature on the fluorescence spectrum, we
measured the fluorescence spectra of 4 at nine temperatures of
0 1
/S ) of 5 appeared at 445 nm, and the emis-
To obtain further insight into photophysical properties at the
molecular level, quantum computations for the optimized struc-
tures in THF and crystal structures in the solid-state were carried
out using Gaussian 16 (Revision A.03) [16] according to the density
functional theory (DFT; CAM-B3LYP) [17] and time-dependent DFT
(TDDFT) [18] methods. 6-31G* basis sets were used for C, H, N, and
O atoms. Frequency calculations were also performed to make sure
that the geometries of ground-state reached the minimum point on
the potential energy surfaces. The calculated absorption spectra
and related MO contributions were obtained from the TDDFT/sin-
glets output file and gaussum 2.2. Multiwfn 3.6(dev) [19] was used
for the analysis of electron excitation.
The energy levels of the highest occupied molecular orbital
(HOMO) and the lowest unoccupied orbital (LUMO) of 3 and 4 are
shown in Fig. 3. The energy level difference of 3 (3.33 eV) was
bigger than that of 4 (2.83 eV). It is inferred that the electrons of 4
are more likely to transit from HOMO to LUMO for a smaller gap,
and its corresponding absorption spectrum should be more red-
shifted. According to the theoretical UV-Vis absorption spectra
from TDDFT (Fig. 3, bottom), the lowest electronic transitions are
mainly composed of HOMO /LUMO, which is located at 387 nm (H
~
8
0K, 100K, 120K, 150K, 180K, 210K, 240K, 270K, and 300K in the
solid-state, and found the effect of temperature on the shape of the
fluorescence spectrum was very small, except that the emission
peak had a blue shift of a few nanometers (575/550 nm), and the
fluorescence intensity increased linearly with the decrease of
temperature (Fig. 2C). When the temperature was lowered, the
molecular vibration was weakened, and the proportion of the non-
radiation process was reduced. Accordingly, the proportion of the
/
L (75%), 0.250) for 3, 436 nm (H / L (97%), 0.246) for 4,
respectively. Hence, the absorption spectrum of 4 has a redshift of
50 nm than that of 3, which is consistent with the experimental
~
results (Fig. 2A, Fig. S23).
Multiwfn 3.6(dev) [19] was used for the analysis of electron
excitation, and the values of D, Sr, H, t, and Ds were summarized in
Table S8.
For the S
0 1
/S excitation of compound 3, the D index was small,
0.83 Å, approximately equal to 60% length of CeC bond, and Ds was
relatively large, ꢁ0.79. Thus, it is judged as a weak Center-
symmetric Charge Transfer Excitation (CCTE).
For the S
and the Sr index was 0.79 (the upper limit is 1.0), equivalent to an
0% perfect coincidence of holes and electrons. Besides, the t index
0 1
/S excitation of 4, the D index was tiny as 0.001 Å,
8
was ꢁ2.23, significantly smaller than 0, which means that there is
no significant separation of holes and electrons. Thus, this transi-
tion is judged as a Localized Excitation (LE). MO147 (HOMO) had an
absolute dominant role for holes, contributing 97.0%, while elec-
trons were mainly composed of MO148 (LUMO) with a contribution
percentage of 97.3%. This also applied to 5 as the two structures for
4 and 5 are very similar.
Fig. 2. (A): Absorption spectra(black), emission spectra(red) of 4 in THF at 298 K; (B):
Absorption spectra(black), emission spectra(red) of 5 in THF at 298 K; (C) Emission
spectra of 4 in solid state at variable temperature; (D): Fluorescence lifetime of com-
pound 4 at variable temperature in solid-state.

4
X. Wang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 227 (2020) 117680
Table 1
Absorption and emission data for 4.
abs[nm] ε [M 1cm ] 298K(THF)
ꢁ
ꢁ1
lem[nm], Ø [%]
t
e
[ns](percentage) (temperature) in solid statec
l
288(110700); 464(13200)
580, 14.3a (THF, 298K)
5
2.55 (39%); 9.77(61%) (80K)
2.37(42%); 9.28(58%) (150K)
75, 20.1b (Solid, 300K)
1
0
.55(54%); 6.55(46%) (230K)
.92(72%); 3.44(28%) (300K)
a
b
c
Relative quantum yields (Ø) were determined based on fluorescein (Ø ¼ 0.95 in 0.1 M NaOH solution), ex ¼ 460 nm.
l
Absolute quantum yields (Ø) were determined by the integrating sphere directly.
lex ¼ 410 nm, the decays were found to be biexponential.
Compound 4 having a face-to-face
converted to Compound 5 with a C/NeH$$$
uration under a weak basic condition. They have been characterized
p-
p
stacking structure could be
p
herringbone config-
1
13
by H and C NMR, HRMS, Raman, IR, X-ray crystallography, pho-
tophysics, and DFT computations (CAM-B3LYP). This information is
important for the design of photonic molecules. Further studies
involving the effects of substituents on fluorescent properties and
p-p stacking configuration and their application to the design of
optical materials are in progress.
Declaration of competing interests
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgment
This research was supported by the 2016 General Project of
Education Department of Liaoning Province (No. L2016003), the
Doctoral Research Fund of Liaoning Science and Technology
Department (No. 20170520158), the Talent Scientific Research Fund
of LSHU (No. 2016XJJ-010), the Opening Funds of Key Laboratory of
Synthetic and Biological Colloids, Ministry of Education, Jiangnan
University (JDSJ2018-05) and the Opening Project of State Key
Laboratory of Polymer Materials Engineering (Sichuan University)
Fig. 3. Top: Frontier MO representations for 3a and 4, the energies are in eV. Bot-
tom:TDDFT computed positions of the 100 first 0e0 electronic transitions in 3a and 4
(
blue lines; F ¼ oscillator strength). The black traces are generated by applying a
-1
thickness of 3000 cm to the bar graph.
(Grant No. sklpme2019-4-24).
To evaluate the interaction energy, 4-tetramer and 5-dimer
aggregates for 4, 5 were investigated respectively by B3LYP/D3
Appendix A. Supplementary data
(
BJ) [20]. The distances between monomers and all the conforma-
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.saa.2019.117680.
tions were kept consistent with the results of crystals. The inter-
action energy (binding energy) was calculated as the energy
difference between n-aggregates and that of n constituting
monomer units by Equation (1).
References
[
1] R. Usman, A. Khan, M. Wang, Y. Luo, W. Sun, H. Sun, C. Du, N. He, Investigation
of charge-transfer interaction in mixed stack donoreacceptor cocrystals to-
ward tunable solid-state emission characteristics, Cryst. Growth Des. 18
DEbind ¼ E(aggregates)-E(every monomer)
(1)
(
2018) 6001e6008.
-
1
The total interaction energy for 4-tetramer is 391 kJ$mol ; thus
[2] H. Liu, L. Yao, B. Li, X. Chen, Y. Gao, S. Zhang, W. Li, P. Lu, B. Yang, Y. Ma,
such a system of 4 was obtained with stabilization energy of
Excimer-induced high-efficiency fluorescence due to pairwise anthracene
8 kJ$mol- per extra unit; while the interaction energy for 5 is
1
stacking in
356e7359.
a crystal with long lifetime, Chem. Commun. 52 (2016)
9
4
7
2 kJ$mol-1 per additional unit.
[
[
3] B. Valeur, Molecular Fluorescence, Digital Encyclopedia of Applied Physics,
2003, pp. 477e531.
4] M. Chen, L. Yan, Y. Zhao, I. Murtaza, H. Meng, W. Huang, Anthracene-based
semiconductors for organic field-effect transistors, J. Mater. Chem. C 6 (2018)
The predicted fluorescence wavelengths for 4 and 5 were
97 nm (2.08 e. v.) and 575 nm (2.16 e. v.) respectively in THF
environment; For the solid-state, the wavelengths were 572 nm of
-tetramer and 547 nm for 5-dimer, which compared reasonably
with the experimental data (580 and 572 nm, Fig. 2). Details of all
DFT and TDDFT calculations were placed in the ESI.
5
7
416e7444.
4
[5] T. Iwanaga, N. Asano, H. Yamada, S. Toyota, Synthesis and photophysical
properties of dinaphtho [2, 3-b: 2’, 3’-i]-dihydrophenazine derivatives, Tet-
rahedron Lett. 60 (2019) 1113e1116.
6] D. Wu, M. Wang, Y. Luo, Y. Zhang, Y. Ma, B. Sun, Tuning the structures and
photophysical properties of 9, 10-distyrylanthrance (DSA) via fluorine sub-
stitution, New J. Chem. 41 (2017) 4220e4233.
[
4
. Conclusions
[7] A.M. Philip, S.K. Manikandan, A. Shaji, M. Hariharan, Concerted interplay of
excimer and dipole coupling governs the exciton relaxation dynamics in
crystalline anthracenes, Chem. Eur J. 24 (2018) 18089e18096.
In conclusion, conjugated anthracene Fluorophores with
[8] Z. Zhang, Y. Zhang, D. Yao, H. Bi, I. Javed, Y. Fan, H. Zhang, Y. Wang, Anthra-
different multilayer structures were synthesized in this work.
cene-arrangement-dependent emissions of crystals of 9-anthrylpyrazole

X. Wang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 227 (2020) 117680
5
derivatives, Cryst. Growth Des. 9 (2009) 5069e5076.
[16] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant,
J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi,
C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador,
J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain,
O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz,
Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng,
A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen,
M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 16, Revision A.03, Gaussian, Inc.,
Wallingford CT, 2016.
[
9] X. Qu, Q. Liu, X. Ji, H. Chen, Z. Zhou, Z. Shen, Enhancing the Stokes’ shift of
BODIPY dyes via through-bond energy transfer and its application for Fe3
þ
-
detection in live cell imaging, Chem. Commun. (J. Chem. Soc. Sect. D) 48
2012) 4600e4602.
(
[
[
[
10] Q. Feng, M. Wang, C. Xu, A. Khan, X. Wu, J. Lu, X. Wei, Investigation of mo-
lecular arrangements and solid-state fluorescence properties of solvates and
cocrystals of 1-acetyl-3-phenyl-5-(9-anthryl)-2-pyrazoline, CrystEngComm
16 (2014) 5820e5826.
11] Y. Gao, H. Liu, S. Zhang, Q. Gu, Y. Shen, Y. Ge, B. Yang, Excimer formation and
evolution of excited state properties in discrete dimeric stacking of an
anthracene derivative: a computational investigation, Phys. Chem. Chem.
Phys. 20 (2018) 12129e12137.
12] X. Wang, D. Fortin, G. Brisard, P.D. Harvey, Drastic tuning of the photonic
properties of «(PushePull) n» trans-bis (ethynyl) bis (tributylphosphine)
platinum (II)-Containing polymers, Macromol. rapid comm. 35 (2014)
[17] R.G. Parr, W. Yang, Density Functional Theory of Atoms and Molecules, Oxford
Univ. Press, Oxford, U.K., 1989.
992e997.
[
[
[
13] S. Hisamatsu, H. Masu, M. Takahashi, K. Kishikawa, S. Kohmoto, Pairwise
packing of anthracene fluorophore: hydrogen-bonding-assisted dimer emis-
sion in solid state, Cryst. Growth Des. 15 (2015) 2291e2302.
14] S.K. Rajagopal, A.M. Philip, K. Nagarajan, M. Hariharan, Progressive acylation
of pyrene engineers solid state packing and colour via CeH/ HeC, CeH/ O
[18] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, An efficient implementation of time-
dependent density-functional theory for the calculation of excitation energies
of large molecules, J. Chem. Phys. 109 (1998) 8218e8224.
[19] T. Lu, Multiwfn Manual, version 3.6(dev), Section 3.21.1, available at: http://
sobereva.com/multiwfn.
[20] S. Grimme, J. Antony, S. Ehrlich, H. Krieg, A consistent and accurate ab initio
parametrization of density functional dispersion correction (DFT-D) for the 94
elements H-Pu, J. Chem. Phys. 132 (2010) 154104.
and
pe
p
interactions, Chem. Commun. 50 (2014) 8644e8647.
15] A.M. Brouwer, Standards for photoluminescence quantum yield measure-
ments in solution (IUPAC Technical Report), Pure Appl. Chem. 83 (2011)
2213e2228.