Structural insights into the aggregation-induced emission mechanism of naphthalene diimide solids

Article abstract of DOI:10.1016/j.dyepig.2017.06.044

Naphthalene diimides (NDIs) are an interesting class of electron-poor organic dyes but with weak emissions that limit their applications. Recently several examples have demonstrated that self-assembly of such weak emissive NDIs into some special aggregates could enhance their emissions. However, a detailed emission mechanism remains unexplored due to the lack of structural evidences. In order to go deep into the emissive mechanism and in turn guide material design, it is necessary to learn the molecular arrangement in the aggregates. For this purpose, in this paper we used a crystal engineering strategy to explore the structure-property relationships between the molecular packing and emissive properties of NDI derivatives in crystalline state, which revealed that the small slipped cofacial π-π stacking of NDI cores in the solid states answered for their enhanced emission behaviors. This observation has an extensive applicability and practical significance for design of NDI based aggregation-induced emission materials.

Full text of DOI:10.1016/j.dyepig.2017.06.044

Accepted Manuscript
Structural insights into the aggregation-induced emission mechanism of naphthalene
diimide solids
Xin Fang, Hua Ke, Lei Li, Mei-Jin Lin
PII:
S0143-7208(17)30982-8
10.1016/j.dyepig.2017.06.044
DYPI 6065
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 28 April 2017
Revised Date: 14 June 2017
Accepted Date: 15 June 2017
Please cite this article as: Fang X, Ke H, Li L, Lin M-J, Structural insights into the aggregation-
induced emission mechanism of naphthalene diimide solids, Dyes and Pigments (2017), doi: 10.1016/
j.dyepig.2017.06.044.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
The structure-property relationship studies of naphthalene diimide (NDI) crystals revealed that the small slipped cofacial π-π
stacking of NDI cores answered for their enhanced emission behaviors.

ACCEPTED MANUSCRIPT
Structural Insights into the Aggregation-Induced Emission Mechanism of
Naphthalene Diimide Solids
*
Xin Fang, Hua Ke, Lei Li and Mei-Jin Lin
State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, China,
3
50116, E-mail: meijin_lin@fzu.edu.cn, Tel: 0086 591 2286 6143
Abstract: Naphthalene diimides (NDIs) are an interesting class of electron-poor organic dyes but with weak emissions
that limit their applications. Recently several examples have demonstrated that self-assembly of such weak emissive
NDIs into some special aggregates could enhance their emissions. However, a detailed emission mechanism remains
unexplored due to the lack of structural evidences. In order to go deep into the emissive mechanism and in turn guide
material design, it is necessary to learn the molecular arrangement in the aggregates. For this purpose, in this paper we
used a crystal engineering strategy to explore the structure-property relationships between the molecular packing and
emissive properties of NDI derivatives in crystalline state, which revealed that the small slipped cofacial π-π stacking
of NDI cores in the solid states answered for their enhanced emission behaviors. This observation has an extensive
applicability and practical significance for design of NDI based aggregation-induced emission materials.
Keywords: naphthalene diimides; aggregation-induced emission; single-crystal structure; π-π interaction; solid-state
emission
1
. Introduction
Most organic π-conjugated dyes show high fluorescence in their dilute solutions but become weakly luminescent
[
1]
in the solid state due to the formation of less emissive aggregative species. However, the ideal luminescent materials
-
1 -

ACCEPTED MANUSCRIPT
must possess a high solid-state luminescence efficiency, because organic devices such as organic light-emitting diodes
[
2]
(
OLEDs) and lasers are only able to function in a film or crystalline state. Consequently increasing attention has been
[
3]
[4]
[5]
paid to enhancing the solid-state luminescence of such materials. Tang, Park and others in the past few years have
reported several material systems exhibiting aggregation-induced emission (AIE) properties.
Rylene diimides are an attractive class of organic dyes owing to their outstanding optical (absorptive and emissive),
[
6]
electronic (n-type semiconducting), and light fastness properties. Similar to common π-conjugated dyes, those with
[
7]
[8]
[9]
extended aromatic cores, such as perylene, terrylene, and quaterrylene diimides, are highly emissive when
dissolved in good solvents but become faintly luminescent when aggregated in poor solvents, a film or crystalline state.
On the contrary, naphthalene diimides (NDIs) with limited aromatic cores are less emissive either in organic solvents or
[
10]
in the solid state. A common strategy to enhance the emission of the latter is the incorporation of donor groups (e.g.
alkyamino or aryamino groups) into their parents through the core substitutions, which indeed improve fluorescence
[
11]
quantum yields in organic solvents but not in the solid states. Encouragingly, recently several research groups have
observed that the self-assembly of less emissive NDIs into some special aggregates (nanoparticles or gels) could
[
12]
enhance their emissions, which have been attributed to the formation of aggregation excimers. However, a detailed
emission mechanism remains unexplored due to the lack of structural evidences.
In order to go deep into the emissive mechanism and in turn guide materials design, it is necessary to learn the
molecular arrangement of two individual molecules in such aggregates. For this purpose, herein we use a crystal
engineering strategy to explore the structure-property relationships between the molecular packing and emissive
properties of naphthalene diimide derivatives in crystalline state. To rationally control the π-π stacking of NDIs in solid
states, three 2, 6-diphenoxy-substituted NDIs with phenyl (NDI 1 in Fig. 1a), isopropyl (NDI 2) or methyl moieties
-
2 -

ACCEPTED MANUSCRIPT
(NDI 3) at both ortho positions of phenoxy substituents have been designed, which is mainly in consideration of that
the introduction of such tweezers-shaped substituents are possible to bite the NDI scaffold perpendicularly and thus the
cofacial π-π stacking of NDI cores is anticipated to be slipped. Moreover, the size of the ortho-moieties should play a
critical role for the degree of π-contacts of NDI cores in solid state. As expected, the single-crystal structure studies
indicated that NDIs 1-3 possessed different molecular arrangements in solid states, which led to totally diacritical
solid-state emissive properties. Interestingly, only the aggregates of NDIs adopting a slipped cofacial π-π stacking with
a small inclined-angle (a small slipped cofacial π-π stacking, Fig. 1b) have been found to exhibit aggregation-induced
emission (AIE) properties. This observation has an extensive applicability and practical significance for design NDI
AIE materials.
2
. Experimental
2
.1 Materials and measurements
1
,4,5,8-Naphthalenetetracarboxylic dianhydride (95%), pentan-1-amine (95%), 2,6-diisopropylphenol (97%),
2
,6-diphenylphenol (99%), potassium carbonate (99%), oleum (50% SO ), acetic acid (AcOH, 99.5%),
3
N-methyl-2-pyrrolidone (NMP, 99.5%), dichloromethane (DCM, 99.5%) and petroleum ether (PE, 60~90°C) were
obtained from commercial suppliers. All chemicals and reagents were used as received unless otherwise stated. Column
chromatography was performed using silica gel (Si60, mesh size 150 µm from Sinopharm Chemical Reagent Co, Ltd.).
NMR spectra were recorded with a Bruker Avance 400 MHz NMR spectrometer. Chemical shifts are given in parts per
1
million (ppm) and referred to TMS as internal standard. H coupling constants J are given in Hertz (Hz). ESI mass
spectra were recorded on a LCQ Fleet from Thermo Fisher Scientific.
®
All the solvents used for the spectroscopic measurements were of spectroscopic grade (Alfa Aesar ) and were used
-
3 -

ACCEPTED MANUSCRIPT
without further purification. The UV/Vis spectra were recorded on a Perkin-Elmer Lambda 900 spectrometer and
corrected against the reference solution. The fluorescence spectra were recorded with an Edinburgh FL-FS 920 TCSPC
instrument. All fluorescence measurements were performed under ambient conditions and corrected against
photomultiplier and lamp intensity. Solid state absorption spectra were determined by Perkin-Elmer Lambda 900
spectrometer with an integrating sphere. Absolute fluorescence quantum yields were Edinburgh FL-FS 920 TCSPC
instrument with an integrating sphere.
2
.2 Synthesis
Synthesis of 4: A solution of dibromoisocyanuric acid (DBI) (1.47g, 5.1mmol) in oleum (30mL, 50% SO ) was
3
added at RT to a solution of 1,4,5,8-naphthalenetetracarboxylic dianhydride (1.43g, 5.0mmol) in oleum (30mL,
0%SO3) over a course of 1h. The resulting mixture was stirred at 60°C for 6h and then cautiously poured into crushed
5
ice (200g).The mixture was diluted with water (200mL). The precipitate was collected on a Buchner funnel, washed
with water and methanol, and dried at 90°C, leading to a bright yellow solid (2.10g, yield 90%). The crude Product 4
was used for the next step without further purification.
Synthesis of 5: A mixture of compound 4 (2.13g, 5.0mmol), pentan-1-amine (1.05g, 12mmol), and acetic acid
(
50mL) was stirred at 130°C for 2h under Ar protection. Upon cooling to RT, the mixture was poured into 200mL cold
water, filtrated, and washed with water and methanol. After drying, the resulting reddish solid was purified by column
1
chromatography (DCM/PE = 1/1), leading to compound 5 as a yellow solid (1.07g, 38% yield). H NMR (CDCl , 400
3
13
MHz, 298 K): δ = 9.01 (s, 2H), 4.34-4.12 (m, 4H), 1.77 (s, 4H), 1.43 (s, 4H), 1.31 (s, 4H), 0.95 (s, 6H); C NMR
(
CDCl , 100 MHz, 298K):160.77, 139.07, 128.33, 127.82, 125.37, 124.20, 41.62, 29.17, 27,58, 22.37, 13.96. MS (ESI):
3
+
calculated for [M+H] of 3, 565.27, found, 565.09.
-
4 -

ACCEPTED MANUSCRIPT
Synthesis of NDI 1: A mixture of compound 5 (0.57g, 1.0mmol), 2,6-diisopropylphenol (0.53g, 3mmol),
potassium carbonate (0.40mg, 4.6mmol) and NMP (50mL) was stirred at 150°C for 12h under Ar protection. After
being cooled to room temperature, the reaction mixture was slowly dropped into 250 mL of 1N HCl under stirring,
filtrated, and washed with water and methanol. After drying, the crude product was purified by column
1
chromatography (DCM/PE = 1/1) and afforded 0.35g of NDI 1 as a yellow solid. Yield: 45%. H NMR (CD Cl , 400
2
2
MHz, 298 K): δ = 7.91 (s, 2H), 7.43-4.37 (m, 6H), 4.13-4.17 (m, 4H), 3.05-2.94 (dt, J= 13.7, 6.8Hz, 4H), 1.77-1.70 (m,
1
3
4
1
2
H), 1.42-1.41 (d, J= 3.5Hz, 8H), 1.28-1.12 (dd, J= 55.6, 6.8 Hz, 24H), 0.95-0.92(t, J= 6.6 Hz, 6H); C NMR (CD Cl ,
2 2
00 MHz, 298K):161.90, 160.59, 159.70, 147.72, 141.02, 127.44, 127.08, 125.08, 124.34, 120.31, 110.63, 40.50, 29.25,
-
7.57, 27.45, 23.90, 22.36, 22.26, 13.74. MS (ESI): calculated for [M+e] of NDI 1, 758.43, found, 758.27.
1
Synthesis of NDI 2: The synthesis of NDI 2 is similar to NDI 1. NDI 2 is an orange solid (38% yield). H NMR
(
3
CDCl , 400 MHz, 298 K): δ = 7.60-7.59 (d, J= 8.5 Hz, 10H), 7.51-7.46 (m, 6H), 7.17-7.13(t, J= 7.5 Hz, 8H),
13
7
.10-7.06(t, J= 7.3 Hz, 4H), 4.06-4.02 (m, 4H), 1.68-1.63 (m, 4H), 1.44-1.35 (m, 8H), 0.96-0.93(t, J= 6.9 Hz, 6H); C
NMR (CDCl
3
, 100 MHz, 298K): 161.90, 160.14, 157.96, 147.31, 136.90, 135.56, 130.98, 129.38, 128.02, 127.52,
+
1
8
26.97, 126.17, 123.38, 120.67, 110.55, 40.42, 29.21, 27.65, 22.46, 14.04. MS (ESI): calculated for [M+H] o f NDI 2,
95.37, found, 895.38.
1
Synthesis of NDI 3: The synthesis of NDI 3 is similar to NDI 1. NDI 2 is an orange solid (45% yield). H NMR
(
CDCl , 400 MHz, 298 K): δ = 7.97 (s, 2H), 7.19 (s, 6H), 4.36–4.02 (m, 4H), 2.18 (s, 12H), 1.75 (s, 4H), 1.41 (s, 8H),
3
1
3
0
1
.92 (t, J = 5.9 Hz, 6H); C NMR (CDCl , 100 MHz, 298K): δ = 162.12, 160.77, 159.06, 150.23, 130.60, 129.64,
3
+
27.66, 126.46, 124.46, 120.44, 110.78, 40.89, 29.32, 27.67, 22.36, 16.30, 14.03. MS (ESI): calculated for [M+H] o f
NDI 2, 647.30, found, 647.37.
-
5 -

ACCEPTED MANUSCRIPT
2
.3 X-ray crystallography study
Single crystals of NDI 1-3 suitable for X-ray diffraction analysis were obtained by dissolving each of these
compounds in a solvent mixture (CH Cl /EtOH = 40:10), followed by slow evaporation of the solvents. Crystal data for
2
2
all three compounds were collected on a Rigaku R-AXIS RAPID IP diffractometer with Mo K (λ = 0.71073 Å) at 173
α
K. The structures were solved using direct methods, refined with the SHELX software package and expanded using
Fourier techniques. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were assigned to idealized
positions and were included in structure factors calculations. Crystal data and the structure refinements are summarized
in Table 1. In addition, crystallographic data have been deposited with the Cambridge Crystallographic Data Center as
supplementary publication number CCDC 1510093 for NDI 1, CCDC 1510095 for NDI 2 and CCDC 1510094 for NDI
3
. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
3
. Results and discussions
3
.1. Synthesis
The synthetic process of NDIs 1-3 is similar to the syntheses of perylene dimides bearing the similar substituents.
As deposited in Scheme 1, in the presence of potassium carbonate, nucleophilic substitution of two bromine atoms
[
13]
of core-dibrominated 5 by excess anions of 2, 6-dimethylphenol, 2, 6-diisopropylphenol and 2, 6-diphenylphenol
afforded the highly soluble diphenoxyl NDIs 1-3 in yields of 38%, 45% and 45%, respectively. It is worth pointing out
that an increasing steric hindrance of isolated substituents of phenol, for example, using 2, 6-di-tert-butylphenol,
[
14]
however, have reported to result in two carbon nucleophilic substituted and mono-debrominated products insteadly.
1
The chemical structures of NDIs 1-3 were assigned by H NMR spectra and ESI mass spectra (for details and crystal
-
6 -

ACCEPTED MANUSCRIPT
data, see Supporting Information) as well as by single-crystal X-ray diffraction analysis.
3
.2. Single-crystal structural descriptions
Upon slow evaporation of solutions of three PBIs in a solvent mixture of CH Cl and C H OH in a volume ratio of
2
2
2
5
4
0/10 at room temperature, respectively, Single crystals of NDIs 1-3 (red prism) suitable for X-ray diffraction analysis
were obtained after several days. The structural study unequivocally confirms the diphenyl ether structures of three
NDIs bearing two phenoxyl groups perpendicularly biting to the NDI core to hinder their cofacial π-stacking. However,
as expected from the design principle mentioned above, due to the different size of the ortho-moieties, they possessed
different crystal constants (space group of P-1 for NDI 1, P2 /n for NDI 2, and Pbca for NDI 3) and molecular
1
arrangements (for details, see Supporting Information). Among them, the patent cores in NDI 1 and NDI 2 crystals are
slip-stacked in a parallel displaced packing pattern (Fig. 2 and 3), while those in NDI 3 are perpendicular to each other
with an edge-to-face arrangement (Fig. 4).
In the single-crystal structure of NDI 1, the bulky phenyl moieties at both ortho positions of perpendicular
phenoxy substituents efficiently shield the NDI scaffold (Fig. 2a), thus isolating it from the environment and
prohibiting any π-contacts between neighbouring NDI units (Fig. 2c), which is further guaranteed that the structural
properties of the NDI scaffolds are not distorted (Fig. 2b). To evaluate the degree of a NDI scaffold, the twist angle
between the averaged naphthalene plane (C1-C8 in Fig. 1a) and averaged imide plane (four C=O groups and two N
atoms) have been applied in the past with consistent outcome, i.e. a twist angles of ∼3.72º for 2, 6-dichloro-NDIs and
[
15]
∼
10.21º for 2,3,6,7-tetrachloro-NDIs . For NDI 1, the twist angle between the involved naphthalene plane and imide
plane is 0.28°, indicating it is an almost planar π-scaffold. As mentioned above, also because of the bulky phenyl
moieties, the single crystal of NDI 1 exhibits a close interplanar spacing of 6.36Å and a slipping angle of 32.91º
-
7 -

ACCEPTED MANUSCRIPT
between the stacks (Fig. 2c).
For the NDI 2, due to the isopropyl moieties at the ortho positions of phenoxy substituents not large enough to
totally obstruct the π-contacts between neighbouring NDI units, it adopts a slip-stacked face -to-face packing model
with a π-overlap area of around half imide unit (Fig. 3c). In the packing, the distances between two close NDI units are
around 3.64Å and the slipping angles between two close NDI centres and NDI N-N axis are around 32.52º. The
formation of such slipped cofacial π-π stacking will be manifested in its UV/Vis absorption and fluorescence emission
properties in solid state (see below). Also because of the π-contacts, the π-conjugated backbones of NDI 2 are slightly
distorted, which is much different from those of NDI 1. The twist angle between the averaged naphthalene plane and
averaged imide plane is around 6.22º (Fig. 3b).
The original intention of NDI 3 with two small methyl groups at the ortho positions of phenoxy substituents was
to enhance the π-contacts in the parallel displaced molecular arrangements. However, the crystal structure of NDI 3
exhibits an edge-to-face T-shaped arrangement (Fig. 4c) in spite of several crystallization attempts. Obviously, the
formation of such unexpected packing is related to the introduction of the small methyl groups, which not only prevent
cofacial π-π stacking, but also produce several new intermolecular contacts, such as C=O…H hydrogen bonds (dC=O
=
3
.36Å, dO…H = 2.53Å) between imide units and methyl groups from two neighbouring molecules, CH…π interactions
(
(
dC…π = 3.60Å, dH…π = 2.72Å) between pentyl groups in imide units and two neighbouring electron-deficient π systems
Fig. 4c). Moreover, the strengths of the latter are stronger than those of the potential π-overlaps. As a result, NDI 3
with smaller substituents shows a remarkably different molecular packing in its single crystal compared to those of
NDI 1 and NDI 2. For the π-scaffold of NDI 3, owing to the intermolecular contacts with the surrounding molecules,
e.g. the formation of C=O…H hydrogen bonds, it is also distorted with a twist angles of ∼6.37º between the averaged
-
8 -

ACCEPTED MANUSCRIPT
naphthalene plane and imide plane, close to that of NDI 2 (Fig. 4b).
3
.3. Optical properties
The different structural properties revealed, particularly different molecular arrangement, for NDIs 1-3 are also
reflected in their solid-state UV/Vis absorption and fluorescence properties. Fig. 5 shows the solid-state UV/Vis diffuse
reflectance spectra (DRS) and fluorescence spectra of NDIs 1-3 crystals at room temperature. In comparison to the
UV/Vis spectra of NDIs 1-3 in solution (absorption maximum at ca. 456 nm, 455nm, and 457nm for NDIs 1-3 in
dichloromethane, respectively, see Supporting Information), their DRS shows a close absorption maximum at ca.
4
49nm, 435nm, and 452nm, which are shifted hypsochromically by ca. 7 nm, 20nm, and 5nm for NDIs 1-3,
respectively. The most remarkable feature of the DRS is, however, the loss of vibronic fine structure for all three NDIs
and the very intensive absorption from ultraviolet 200nm to visible range ca. 700nm, 600nm and 800nm, respectively,
for NDIs 1-3. Together with the structural information revealed above, the blue-shift of solid-state DRS of NDIs 1-3
can mainly be attributed to the reduced interactions between organic solvents and NDI cores in the crystals than in
solutions, which is consistent with the phenomena that the DRS of NDI 2 drop more sharply in the long wavelength
side than those of NDI 1 and 3. Similar as the solvation effects, the NDI skeletons in the latter are partially surrounded
by the substituents of the neighbouring molecules, while those in NDI 2 mainly are contacted by the partial π-overlaps.
In line with the absorption spectra, the fluorescence spectrum of NDI 2 exhibits a sharp band at 511nm, while
those of NDI 1 and 3 show a relatively broad and bathochromic band with almost the same emission maximum at
5
78nm (Fig. 5b). More importantly, the quantum yield (Φ ) of NDI 2 is much enhanced (∼7%) in comparison to that in
F
solutions (close to 0%), while those of NDI 1 and 3 could not be measured. Clearly, the enhanced emission of NDI 2 is
related to close π-π stacking in the solid state (the distances of the neighbouring two NDI skeletons is 3.64Å) because
-
9 -

ACCEPTED MANUSCRIPT
only it possesses such a structural feature. A combination of the fact that unsubstituted NDIs with fully or largely
[
11]
cofacial π-stacks are always non-emissive, a conclusion that the slipped cofacial π-π stacking with a small π-overlap
(
or small inclined-angle) plays a key role for the aggregation-induced emission of NDI solids, can be reached logically.
[
16]
Moreover, this speculation can also be rationalized by molecular exciton theory. At the small inclined-angle, the
neighbouring two NDIs adopt a J-type aggregation pattern, and thus their optical transition from the ground state to the
lower energy excitonic state is no longer forbidden, which leads to the photoluminescence observed. Unfortunately, the
[
17]
extended experiments by mixing NDIs 1-3 in nonpolar solvents (e.g. methylcyclohexane and n-hexane)
revealed
that no similar AIE phenomena have been observed, even by standing for two weeks, which indicated no similar
J-aggregates formed in such nonpolar solvents as in crystalline state. Furthermore, due to the stability of NDIs 1-3
crystals, neither obvious solid-state UV/Vis absorption nor fluorescence changes have been observed for all three
[
18]
crystals by the mechanochromic pathways (e.g. grinding, fuming and heating) . However, this does not affect the
[
12]
logical conjecture that the molecular arrangements of the reported NDI solids with AIE properties
should also be
J-aggregated. This observation has an extensive applicability and practical significance for design NDI AIE materials.
4
. Conclusions
In summary, we have reported that the syntheses, single-crystal structures and optical properties of three 2,
6
-diphenoxy-substituted NDIs with methyl, isopropyl or phenyl substituents at both ortho positions of the phenoxy
substituents, which revealed that the small slipped cofacial π-π stacking of NDI cores in the solid states was
demonstrated to answer for their enhanced emissions. We envision that this observation will contribute not only to
design of NDI based AIE materials but also be used towards effective development of other novel AIE materials.
5
. Acknowledgements
-
10 -

ACCEPTED MANUSCRIPT
We thank Prof. Jun-Dong Wang and Prof. Chang-Cang Huang for useful discussions. This work has been
supported by National Natural Science Foundation of China (21572032) and Program for New Century Excellent
Talents in Fujian Province University.
6
. References
[
1] Birks J. B., Photophysics of Aromatic Molecules, Wiley, London, 1970;
Tang C. W., Vanslyke S. A., Organic electroluminescent diodes, Appl. Phys. Lett., 1987, 51
Jares-Erijman E. A., Jovin, T. M., FRET imaging, Nat. Biotechnol., 2003, 21: 1387-1395;
: 913-915;
Saigusa H., Lim E. C., Excited-state dynamics of aromatic clusters: correlation between exciton interactions and excimer
formation dynamics, J. Phys. Chem., 1995, 99: 15738-15747.
[2] Hecht S., Frechet J. M. J., Dendritic Encapsulation of Function: Applying Nature's Site Isolation Principle from Biomimetics to
Materials Science, Angew. Chem., Int. Ed., 2001, 40: 74-91;
Chen L., Xu S., McBranch D., Whitten D., Tuning the Properties of Conjugated Polyelectrolytes through Surfactant
Complexation, J. Am. Chem. Soc., 2000, 122: 9302-9303;
Taylor P. N., O’Connell M. J., McNeill L. A., Hall M. J., Aplin R. T., Anderson H. L., Insulated Molecular Wires: Synthesis of
Conjugated Polyrotaxanes by Suzuki Coupling in Water, Angew. Chem., Int. Ed., 2000, 39: 3456-3460.
[
3] Hu R., Leung N. L. C., Tang B. Z., AIE macromolecules: syntheses, structures and functionalities, Chem. Soc. Rev., 2014, 43
494-4562;
Hong Y., Lam J. W. Y., Tang B. Z., Aggregation-induced emission, Chem. Soc. Rev., 2011, 40: 5361-5388;
:
4
Kwok R. T. K., Leung C. W. T., Lam J. W. Y., Tang B. Z., Biosensing by luminogens with aggregation-induced emission
characteristics, Chem. Soc. Rev., 2015, 44: 4228-4238.
[4] Gierschner J., Park S. Y., Luminescent distyrylbenzenes: tailoring molecular structure and crystalline morphology, J. Mater.
Chem. C, 2013,
Seo J., Chung J. W., Kwon J. E., Park S. Y., Photoisomerization-induced gel-to-sol transition and concomitant fluorescence
switching in a transparent supramolecular gel of a cyanostilbene derivative, Chem. Sci., 2014, : 4845-4850;
1: 5818-5832;
5
-
11 -

ACCEPTED MANUSCRIPT
An B.-K., Kwon S.-K., Jung S.-D., Park S. Y., Enhanced Emission and Its Switching in Fluorescent Organic Nanoparticles, J.
Am. Chem. Soc., 2002, 124: 14410-14415.
[
5] Zhang Y., Li D., Li Y., Yu J., Solvatochromic AIE luminogens as supersensitive water detectors in organic solvents and highly
efficient cyanide chemosensors in water, Chem. Sci., 2014,
Shao A., Guo Z., Zhu S., Zhu S., Shi P., Tian H., Zhu W., Insight into aggregation-induced emission characteristics of
red-emissive quinoline-malononitrile by cell tracking and real-time trypsin detection, Chem. Sci., 2014, : 1383-1389;
Yoshii R., Hirose A., Tanaka K., Chujo Y., Functionalization of Boron Diiminates with Unique Optical Properties: Multicolor
Tuning of Crystallization-Induced Emission and Introduction into the Main Chain of Conjugated Polymers, J. Am. Chem. Soc.
014, 136: 18131-18139
5: 2710-2716;
5
,
2
Würthner F., Kaiser T. E., Saha-Möller C. R., J-Aggregates: From Serendipitous Discovery to Supramolecular
Engineering of Functional Dye Materials, Angew. Chem., Int. Ed., 2011, 50: 3376-3410.
[6] Zhan X., Facchetti A., Barlow S., Marks T. J., Ratner M. A., Wasielewski M. R., Marder S. R., Rylene and Related Diimides
for Organic Electronics, Adv. Mater., 2011, 23: 268-284;
Würthner F., Saha-Möller C. R., Fimmel B., Ogi S., Leowanawat P., Schmidt D., Perylene Bisimide Dye Assemblies as
Archetype Functional Supramolecular Materials, Chem. Rev., 2016, 116: 962-1052;
Kobaisi M. A., Bhosale S. V., Latham K., Raynor A. M., and Bhosale S. V., Functional Naphthalene Diimides: Synthesis,
Properties, and Applications, Chem. Rev., 2016, 116: 11685-11796.
[7] Cho J.-W., Yoo H., Lee J.-E., Yan Q., Zhao D., Kim D., Intramolecular Interactions of Highly π-Conjugated Perylenediimide
Oligomers Probed by Single-Molecule Spectroscopy, J. Phys. Chem. Lett., 2014,
Sivamurugan V., Kazlauskas K., Jursenas S., Gruodis A., Simokaitiene J., Grazulevicius J. V., Valiyaveettil S., Synthesis and
Photophysical Properties of Glass-Forming Bay-Substituted Perylenediimide Derivatives, J. Phys. Chem. B, 2010, 114
782-1789.
8] Mais S., Tittel J., Basché T., Bräuchle C., Göhde W., Fuchs H., Müller G., Müllen K., Terrylenediimide:ꢀ A Novel Fluorophore
for Single-Molecule Spectroscopy and Microscopy from 1.4 K to Room Temperature, J. Phys. Chem. A, 1997, 101
435-8440;
5: 3895-3901;
:
1
[
:
8
-
12 -

ACCEPTED MANUSCRIPT
Bullock J. E., Vagnini M. T., Ramanan C., Co D. T., Wilson T. M., Dicke J. W., Marks T. J., Wasielewski M. R., Photophysics
and Redox Properties of Rylene Imide and Diimide Dyes Alkylated Ortho to the Imide Groups, J. Phys. Chem. B, 2010, 114
794-1802.
:
1
[
9] Adachi M., Nagao Y., Design of Near-Infrared Dyes Based on π-Conjugation System Extension 2. Theoretical Elucidation of
Framework Extended Derivatives of Perylene Chromophore, Chem. Mater., 2001, 13: 662-669;
Quante H., Müllen K., Quaterrylenebis(dicarboximides), Angew. Chem., Int. Ed. Engl. 1995, 34, 1323-1325.
10] Bhosale S.V., Jani C.H., Langford S.J., Chemistry of naphthalene Diimides, Chem. Soc. Rev., 2008, 37: 331-342;
Würthner F., Stolte M., Naphthalene and perylene diimides for organic transistors, Chem. Commun., 2011, 47: 5109-5115;
Sakai N., Mareda J., Vauthey E., Matile S., Core-Substituted Naphthalenediimides, Chem. Commun., 2010, 46: 4225-4237.
[
[11] Röger C., Würthner F., Core-Tetrasubstituted Naphthalene Diimides: Synthesis, Optical Properties, and Redox Characteristics,
J. Org. Chem., 2007, 72: 8070-8075;
Würthner F., Ahmed S., Thalacker C., Debaerdemaeker T., Core Substituted Naphthalene Bisimides: New Fluorophors with
Tunable EmissionWavelength for FRET Studies, Chem. Eur. J., 2002, 8: 4742-4750;
Bhosale S. V., Kalyankar M. B., Bhosale S. V., Langford S. J., Reid E. F., Hogan C. F., The synthesis of novel core-substituted
naphthalene diimides via Suzuki cross-coupling and their properties, New J. Chem., 2009, 33: 2409-2413.
[12] Bell T. D. M., Bhosale S. V., Forsyth C. M., Hayne D., Ghiggino K. P., Hutchison J. A., Jani C. H., Langford S. J., Lee M.
A.-P., Woodward C. P., Melt-induced fluorescent signature in a simple naphthalenediimide, Chem. Commun., 2010, 46
881-4883;
:
4
Kumar M., George S. J., Spectroscopic probing of the dynamic self-assembly of an amphiphilic naphthalene diimide exhibiting
reversible vapochromism, Chem. Eur. J., 2011, 17: 11102-11106;
Basak S., Nanda J., Banerjee A., Assembly of naphthalenediimide conjugated peptides: aggregation induced changes in
fluorescence, ChemCommun., 2013, 49: 6891-6893;
Jana P., Maity S. K., Bera S., Ghorai P. K., Haldar D., Hierarchical self-assembly of naphthalene bisimides to fluorescent
microspheres and fluoride sensing, CrystEngComm, 2013, 15: 2512-2518;
-
13 -

ACCEPTED MANUSCRIPT
Basak S., Nandi N., Baral A., Banerjee A., Tailor-made design of J- or H-aggregated naphthalenediimide-based gels and
remarkable fluorescence turn on/off behaviour depending on solvents, ChemCommun., 2015, 51: 780-783;
Choudhury P., Das K., Das P. K., L-Phenylalanine-Tethered, Naphthalene Diimide-Based, Aggregation-Induced,
Green-Emitting Organic Nanoparticles, Langmuir, 2017, 33: 4500-4510.
[13] Lin M. J., Jiménez Á. J., Burschka C., Würthner F., Bay-substituted perylene bisimide dye with an undistorted planar scaffold
and outstanding solid state fluorescence properties, ChemCommun., 2012, 48: 12050-12052;
Jiménez Á. J., Lin M. J., Burschka C., Becker J., Settels V., Engels B., Würthner F., Structure–property relationships for
1
,7-diphenoxy-perylene bisimides in solution and in the solid state, Chem. Sci., 2014, 5: 608-619.
[14] Lin M. J., Fimmel B., Radacki K., Würthner F., Halochromic Phenolate Perylene Bisimides with Unprecedented NIR
Spectroscopic Properties, Angew. Chem. Int. Ed., 2011, 50: 10847-10850.
Fang X., Guo M. D., Weng L. J., Chen Y. , Lin M. J., Cooperative effect of anion-π and electrostatic interactions in NIR
absorbing phenolate naphthalene diimide conjugates, Dyes Pigments, 2015, 113: 251–256.
[
15] Oh J. H., Suraru S.-L., Lee W.-Y., Könemann M., Höffken H. W., Röger C., Schmidt R., Chung Y., Chen W.-C., Würthner F.,
Bao Z., High-performance air-stable n-type organic transistors based on core-chlorinated naphthalene tetracarboxylic diimides,
Adv. Funct. Mater., 2010, 20: 2148-2156.
[
16] Kasha M., Rawls H. R., Ashraf El-Bayoumi M., The exciton model in molecular spectroscopy, Pure Appl. Chem., 1965, 11
71-392;
:
3
Würthner F., Chen Z., Dehm V., Stepanenko V., One-dimensional luminescent nanoaggregates of perylene bisimides, Chem.
Commun., 2006, 73: 1188-1190.
[
17] Bhosale S. V., Jani, C. H., Lalander, C. H., Langford, S. J., Nerush, I., Shapter, J. G., Villamainac D., Vauthey E.,
Supramolecular construction of vesicles based on core-substituted naphthalene diimide appended with triethyleneglycol motifs,
Chem. Commun., 2011,47: 8226-8228;
Bhosale S. V., Jani, C. H., Lalander, C. H., Langford, S. J., Solvophobic control of core-substituted naphthalene diimide
nanostructures, Chem. Commun., 2010, 46: 973-975.
[18] Rananaware A., La D. D., Bhosale S. V., Aggregation-induced emission of a star-shape luminogen based on
cyclohexanehexone substituted with AIE active tetraphenylethene functionality, RSC Adv., 2015, 5: 56270-56273;
-
14 -

ACCEPTED MANUSCRIPT
Salimimarand, M., La D. D., Kobaisi M. A., Bhosale S. V., Flower-like superstructures of AIE-active tetraphenylethylene
through solvophobic controlled self-assembly, Sci. Rep., 2017, 7: 42898
-
15 -

ACCEPTED MANUSCRIPT
Table captions and Schemes, Figures:
Table 1 Crystal data and structure refinement parameters for NDIs 1-3
Scheme 1 Synthesis of NDIs 1-3: i) DBI, oleum, 333K, 6h, 90%; ii) pentan-1-amine, Ar, AcOH, 403K, 5h, 38%;
iii) K CO , Ar, 423K, 12h
2
3
Fig. 1 Chemical structures of NDIs 1-3 (a, top); and schematic diagram of J-aggregated pattern of NDI 2 in solid
state (b, bottom).
Fig. 2 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 1 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted in all views, and phenoxy substituents were omitted in (c).
Fig. 3 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 2 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted in all views, and phenoxy substituents were omitted in (c).
Fig. 4 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 3 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted.
Fig. 5 Solid-state UV/Vis diffuse reflectance spectra (solid line) and fluorescence spectra (dashed line) of NDI 1 (red),
2
(black) and 3(blue) at room temperature.
-
16 -

ACCEPTED MANUSCRIPT
Table 1 Crystal data and structure refinement parameters for NDIs 1-3
Compound reference
NDI 1
NDI 2
NDI 3
Chemical formula
C
48
H
58
N
2
O
6
C
60
H
50
N
2
O
6
40 42 2 6
C H N O
Formula Mass
758.96
895.02
Triclinic
646.76
Crystal system
Monoclinic
12.498(3)
6.4885(13)
26.168(5)
90.00
Orthorhombic
13.733(3)
9.4889(19)
24.899(5)
90.00
a/ Å
b/ Å
c/ Å
α/°
9.5475(19)
11.602(2)
12.509(3)
64.24(3)
83.95(3)
78.19(3)
1221.3(4)
173(2)
P-1
β/°
102.35(3)
90.00
90.00
γ/°
90.00
3
Unit cell volume/ Å
2073.0(7)
173(2)
3244.6(12)
173(2)
Pbca
Temperature/K
Space group
P2 /n
1
No. of formula units per unit cell, Z
No. of reflections measured
No. of independent reflections
2
1
4
16518
4771
10077
25448
5373
3739
R
int
0.0375
0.0557
0.1234
0.0594
0.1255
1.174
0.0357
0.0660
0.1789
0.0744
0.1852
1.061
0.0672
0.0759
0.1483
0.0795
0.1499
1.305
a
Final R values (I > 2σ(I))
1
2
b
Final wR(F ) values (I > 2σ(I))
Final R values (all data)
1
2
Final wR(F ) values (all data)
2
Goodness of fit on F
a
b
2
2 2
2
1/2
R
1
= Σ||F
o
| − |F
c
||/Σ|F
o
|. wR
2
o c o
= [Σw(F − F ) /Σw(F )] .
-
17 -

ACCEPTED MANUSCRIPT
Scheme 1:
Scheme 1 Synthesis of NDIs 1-3: i) DBI, oleum, 333K, 6h, 90%; ii) pentan-1-amine, Ar, AcOH, 403K, 5h, 38%; iii)
K CO , Ar, 423K, 12h.
2
3
-
18 -

ACCEPTED MANUSCRIPT
Figure 1
Fig. 1 Chemical structures of NDIs 1-3 (a, top); and schematic diagram of J-aggregated pattern of NDI 2 in solid state
b, bottom)
(
-
19 -

ACCEPTED MANUSCRIPT
Figure 2:
Fig. 2 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 1 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted in all views, and phenoxy substituents were omitted in (c).
-
20 -

ACCEPTED MANUSCRIPT
Figure 3:
Fig. 3 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 2 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted in all views, and phenoxy substituents were omitted in (c).
-
21 -

ACCEPTED MANUSCRIPT
Figure 4:
Fig. 4 Molecular structure in front view (a) and side view (b), as well as the packing (c) of NDI 3 in the single crystals
as determined by single crystal X-ray analysis at 298 K. Red, blue, and black balls represent O, N, and C atoms,
respectively. For clarity, hydrogen atoms were omitted.
-
22 -

ACCEPTED MANUSCRIPT
Figure 5:
Fig. 5 Solid-state UV/Vis diffuse reflectance spectra (solid line) and fluorescence spectra (dashed line) of NDI 1 (red),
(black) and 3(blue) at room temperature.
2
-
23 -

ACCEPTED MANUSCRIPT
Highlights
1.
2.
3.
The aggregation of weak emissive naphthalene diimides clould lead to an enhanced emissive behaviours.
The structure-property relationships of the aggregations has been explored by single-crystal X-ray analyses.
The small slipped cofacial π-π stacking of naphthalene diimides in the solid states was demonstrated to answer
for their enhanced emissions.
4
.
This observation has an extensive practical significance for design of naphthalene diimide based emission
materials