Solid-State Emissive Diaminomaleimide Dimers and a Polymer – Syntheses, Structures and Optical Properties

Article abstract of DOI:10.1002/ejoc.201900195

Among solid-state emissive maleimide dyes, aminomaleimide dyes are attracting much attention due to the variety of emission colors and functions. We recently reported 3,4-diaminomaleimides, which show photoluminescence (PL) at long wavelengths (> 600 nm) despite their simple structures. In this work, 3,4-diaminomaleimides were connected through a phenylene linker to form p- or m-linked dimers. The PL properties were affected by the linking positions as well as the introduced amino groups. In addition, polymerization was conducted, and the emission color of the obtained polymer was dependent on the morphology.

Full text of DOI:10.1002/ejoc.201900195

DOI: 10.1002/ejoc.201900195
Full Paper
Solid-State Emission
Solid-State Emissive Diaminomaleimide Dimers and a Polymer –
Syntheses, Structures and Optical Properties
Hiroaki Imoto,[a] Ryosuke Fujii,[a] and Kensuke Naka*[a]
Abstract: Among solid-state emissive maleimide dyes, amino- phenylene linker to form p- or m-linked dimers. The PL proper-
maleimide dyes are attracting much attention due to the ties were affected by the linking positions as well as the
variety of emission colors and functions. We recently reported introduced amino groups. In addition, polymerization was
3,4-diaminomaleimides, which show photoluminescence (PL) at conducted, and the emission color of the obtained polymer was
long wavelengths (> 600 nm) despite their simple structures. In dependent on the morphology.
this work, 3,4-diaminomaleimides were connected through a
Introduction
microwave assistance[4a] or one-pot process,[3b] aminomale-
imide dyes are now promising luminescent dyes for practical
use. It is known that the emission colors of maleimide dyes are
drastically affected by the substituents at the 3- and 4-posi-
tions.[1a] Thioether and aryl groups are introduced to realize
various emission color of arylaminomaleimides (Scheme 1b).
Furthermore, Tang and Wang reported alkylaminomaleimides
as highly emissive dyes in 2017 and 2019, respectively
(Scheme 1c). Eventually, we have developed 3,4-diaminomale-
imide dyes to attain longer emission wavelength (> 600 nm) by
utilizing quite simple components; they are composed of a few
kinds of elements and minimal aromatic rings without fused
ring structures (Scheme 1d).[3f] Compared with most of the aryl-
aminomaleimide dyes, which show blue-to-green emission,
these 3,4-diaminomaleimide dyes are suitable for applications
such as bio-probes; an emission spectrum should be located in
the first biological window (650–900 nm).
Maleimide is today a notable class of luminophores,[1–4] while
it has been recognized as an important building block of bio-
active molecules.[5] Luminescent maleimide dyes having various
emission colors and advanced functions have been attained,
e.g., metal sensors,[1a] wavelength conversion dyes,[1g] and lumi-
nescent polymers.[2] It is worth noting that their structures are
simple and composed of simple element compositions; mainly
C, H, N, and O. Therefore, they generally need only facile syn-
thetic procedures and cheap reagents to save the production
costs.
On the other hand, photophysical properties of the male-
imide dyes have been often examined in solutions, though
solid-state emission is crucial for practical applications. This is
because most organic luminescent dyes suffer from aggrega-
tion-caused quenching (ACQ); they exhibit no or very weak
emission in the solid states even if intense emission is observed
in solutions. In this context, we assumed that solid-state-emis-
sive maleimide dyes contribute to the progress of the field of
organic luminescent materials.
Recently, aminomaleimide dyes have been developed by
us[3] and other researchers[4] as solid-state emissive dyes. In
2012, we reported the first examples of aggregation-induced
emission (AIE) active aminomaleimide dyes (Scheme 1a).[3a]
Their emissions are quenched in solutions due to non-radiative
deactivation via molecular motions. On the contrary, these
molecular motions are frozen in aggregation states, and ACQ is
circumvented by restriction of π–π interactions thanks to inter-
molecular hydrogen bond networks, resulting in intense emis-
sion. Since the synthetic procedures have been improved by
[a] Faculty of Molecular Chemistry and Engineering, Graduate School of
Science and Technology, Kyoto Institute of Technology,
Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
E-mail: kenaka@kit.ac.jp
URL: http://www.cis.kit.ac.jp/~kenaka/index_eng.html
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.201900195.
Scheme 1. Chemical structures of luminescent aminomaleimide dyes.
1 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Full Paper
Diaminomaleimides are emerging luminescent dyes as de- peratures at which the samples lost 5 wt.-% from the original
scribed above, and the structure-properties relationships are mass (Td5) were measured: Td5 = 233 °C (3), 328 °C (5), 282 °C
still unknown. Therefore, our next challenge is the expansion of (7), 339 °C (9). The p-toluidino groups contributed to the en-
molecular structures of diaminomaleimide dyes by dimerization hancement of the thermal stability, while the m- and p-linker
or polymerization for understanding the structures and proper- gave relatively little difference.
ties in their assembled states. In this work, maleimide dimers
linked through the imide groups were synthesized. Substituents
at the 3,4-positions and p- or m-linkers affected the optical
properties of the resulting dyes. In addition, m-linked monomer
was prepared, and polycondensation and post-functionalization
offered a diaminomaleimide polymer. This is the first study on
the synthesis and luminescent properties of multiple-amino-
maleimide dyes.
Single crystals of 3, 7, and 9 were obtained for X-ray crystal-
lography.[6] First, the planarity of the dimers was estimated by
the interplanar angles (θint) between the mean planes of the
two maleimide rings and that of the phenylene linker (Figure 1).
p-Linked dimer 3 adopted the twisted structure (θint = 52.07°),
compared with m-linked dimers 7 and 9 (θint = 30.32° (7), 38.72°
(9)). The twisted p-linking was inefficient to expand the conju-
gated system, and thus the bathochromic shifts of the emission
wavelength from the monomeric diaminomaleimide dyes (10
and 11) were little observed in these dimers (vide infra). Sec-
ond, the geometry of the nitrogen atoms of the morpholino
groups was investigated because the contribution of the lone
pair to the conjugated systems affects the optoelectronic prop-
erties of the dimers. For this end, the geometry was evaluated
by the total bond angles around the nitrogen atoms (θtotal) as
shown in Figure 2. In the cases of 3 and 7, two of the nitrogen
Results and Discussion
Syntheses of Dimers
Phenylene-linked 3,4-diaminomaleimide dimers were synthe-
sized as shown in Scheme 2; p- (3 and 5) and m-phenylene (7
and 9) linkers were employed. Dichloromaleic anhydride 1 was
dimerized through imidation with p- and m-phenylenediamines
to produce 2 and 6, respectively. The reaction of 2 with excess
amounts of morpholine gave tetramorpholino-maleimide dimer
3. Instead of morpholine, 2.5 equivalent of p-toluidine was
treated with 2 to obtain chloro-p-toluidino-maleimide dimer 4
and then addition of excess amounts of morpholine gave mor-
pholino-p-toluidino-maleimide 5. The same protocol was ap-
plied to m-linked intermediate 6 to give 7 and 9.
atoms in the dyes adopt trigonal pyramidal structures (θtotal
=
p-Type dimers 3 and 5 were less soluble in organic solvents
than m-type dimers 7 and 9. The linear structures of 3 and 5
probably offered higher crystallinity than the bent ones of 7
and 9. Thermogravimetric analysis (TGA) was carried out to
evaluate thermal stability of the dyes (Figure S22), and the tem-
Figure 1. Average interplanar angles between mean planes of the maleimide
rings and those of the phenylene linkers of (a) 3 and (b) 7 and 9.
Scheme 2. Syntheses of 3,4-diaminomaleimide dimers.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
2
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
343.93° (3), 342.08° (7)), whereas the other two adopt trigonal lowed; the transition energy (ΔE) and oscillator strength (f)
planar structures (θtotal = 355.30° (3), 358.48° (7)). The former were 432.17 nm and 0.0351, respectively. The HOMO was delo-
two nitrogen atoms less contributed to the conjugated systems calized along the conjugated system, whereas the LUMO was
than the latter. The nitrogen atoms of the morpholino groups in located at the maleimide rings, corresponding to the reported
9 possess trigonal planar structures (θtotal = 353.2° and 352.66°), N-arylmaleimides.[3b,3e,3f] In the cases of 5, 7, and 9, the similar
which are beneficial for the expansion of the conjugated sys- results were observed (Figure S17). The ΔE values of 5
tem.
(514.50 nm) and 9 (499.00 nm) were significantly lower than
those of 3 (432.17 nm) and 7 (407.55 nm) because the conjuga-
tion systems of 5 and 9 were expanded via the p-toluidino
groups. This result corresponds to the experimental observation
in the UV/Vis absorption spectra. The HOMO (or HOMO-1) levels
were raised by the expansion of the conjugation lengths via the
p-toluidino groups in 5 and 9, while there were no significant
differences in the LUMO (or LUMO+1) levels because of the lo-
calization at the maleimide rings.
Table 2. Frontier orbitals, energies, and oscillator strength of electronic transi-
tions.[a]
Dye
Frontier orbitals[b] [eV]
ΔE[c] [nm]
f[d]
3
5
7
HOMO (–5.89 eV) → LUMO (–2.39 eV)
HOMO (–5.43 eV) → LUMO (–2.42 eV)
HOMO-1 (–6.11 eV) → LUMO (–2.39 eV)
HOMO (–6.05 eV) → LUMO+1 (–2.39 eV)
HOMO-1 (–5.51 eV) → LUMO (–2.43 eV)
HOMO (–5.47 eV) → LUMO (–2.43 eV)
432.17
514.50
407.55
0.0351
0.0614
0.0346
Figure 2. Total bond angles around the nitrogen atoms of the morpholino
groups of (a) 3, (b) 7, and (c) 9.
9
499.00
0.0856
Optical Properties
[a] Structures were based on the optimization by DFT calculations (B3LYP/6-
31G+(d,p)). [b] Frontier orbitals responsible for electronic transitions esti-
mated by DFT calculations (B3LYP/6-31G+(d,p)). [c] Transition energies, and.
[d] Oscillator strengths estimated by TD-DFT calculations (B3LYP/6-31G+(d,p)).
Optical properties of the dimers and reported monomers are
summarized in Table 1. The UV/Vis absorption spectra (Figure
S18) were measured in dichloromethane (CH2Cl2) solutions (c =
1 × 10–4 M). The longest absorption maxima (λabs) of dimers 3
(418 nm), 5 (453 nm), 7 (417 nm), and 9 (454 nm) were similar
to those of monomers 10 (410 nm) and 11 (447 nm). Expansion
of the conjugated systems was restricted by the twisted
p-linking or the m-linking as described above. Dimers with
p-toluidino groups (5 and 9) showed longer λabs than those of
3 and 7 because the p-toluidino groups effectively expand the
conjugation length.
Figure 3. HOMO and LUMO of 3 depicted by DFT calculations (B3LYP/6-
31G+(d,p)).
Photoluminescence (PL) properties (Figure S20) were exam-
ined in solutions, solid states, and composite films with
poly(methyl methacrylate) (PMMA). Unfortunately, PMMA com-
posite film of 5 failed to be fabricated because of the poor
solubility of 5 in organic solvents such as chloroform, dichloro-
methane, THF, etc. Overall, the emission maxima (λem) were red-
shifted from the PMMA composites to the solutions, and quan-
tum yields (Φ) were enhanced in the PMMA films. Structural
relaxation, which was restricted in the PMMA matrices, was al-
lowed in the solutions, resulting in the red-shifted emission. It
is also probable that non-polar and rigid PMMA matrix contrib-
uted to the blue-shifted emission because the electronic transi-
tions responsible for the emission have charge transfer charac-
Table 1. Optical properties.
[a]
[b]
Dye
[nm]
[nm] (Φ)
λabs
λem
(ε [L/mol cm])
Solution[c]
Solid
In PMMA[d]
592 (0.13)
3
5
7
9
418 (9600)
453 (6300)
417 (8700)
454 (9000)
410 (3000)
447 (3600)
624 (0.03)
614 (0.02)
611 (0.06)
612 (0.02)
609 (0.11)
609 (0.01)
625 (0.04)
643 (0.02)
595 (0.11)
613 (0.004)
593 (0.10)
609 (0.28)
[f]
–
592 (0.16)
595 (0.12)
10[e]
11[e]
–
–
[g]
[g]
[a] Longest absorption maxima in CH2Cl2 solutions (c = 1.0 × 10–4 M).
[b] Emission maxima (excited at excitation maxima). [c] CH2Cl2 solutions (c =
1.0 × 10–5 M). [d] PMMA composite films with 5 wt.-% of dyes. [e] Cited from
ref.[3f]. [f] Not measured. [g] Not reported.
To understand the electronic properties, the frontier orbitals ter. On the other hand, the molecular motions in the solutions
and electronic transitions were evaluated by density functional deactivated the excitons through a non-radiative pathway,
theory (DFT) and time-dependent DFT (TD-DFT) calculations while these motions were frozen in the PMMA matrices to en-
(B3LYP/6-31G+(d,p)), respectively (Table 2).[7] As a representa- hance the emission efficiencies. Additionally, the lower energy
tive example, the frontier orbitals responsible for the electronic gap in the solutions may enhance non-radiative deactivation,
transition in 3 are described in Figure 3. The electronic transi- leading to the lower emission efficiency compared with that in
tion between the highest occupied molecular orbital (HOMO) the PMMA matrix. As a representative example, we measured
and the lowest unoccupied molecular orbital (LUMO) was al- emission lifetime (τ) of 7, which showed intense emission in
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
3
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
both solution and solid states (Figure S21); τ = 3.72 ns (solution)
In the cases of 5 and 9, which contain p-toluidino and mor-
and 6.18 ns (solid). Thus, we concluded that the emission of the pholino groups, the emission wavelengths were red-shifted and
dyes is fluorescence.
emission efficiencies were lowered in solutions and solid states,
compared with their PL properties in PMMA matrices. The X-ray
crystallography of 9 implied that intermolecular π–π interac-
tions form in the solid state probably due to the relatively pla-
nar p-toluidino groups (Figure 5); the p-toluidino groups inter-
act to the neighboring conjugated systems with the distances
of 3.262(5) Å –3.464(4) Å.
The PL properties of 3 in the solution and solid state were
similar; the quantum yields were lower and the emission wave-
lengths were longer compared with those in the PMMA com-
posite film. The results of X-ray crystallography revealed that
the phenylene linker is insulated by the steric hindrance of the
four morpholino groups, enabling the free rotation even in the
solid state (Figure 4a). That is, the excitons of 3 can be deacti-
vated via non-radiative pathways due to molecular motions in
both solution and solid states. The PL properties of 3 were
measured at 77 K to estimate the state in which molecular mo-
tions are frozen (Figure S19). The emission was blue-shifted
(λem = 602 nm), and the quantum yield was enhanced (Φ =
26 %). This result supports the idea that the longer emission
wavelength and the lower quantum yields in solution and solid
states were attributed to the molecular motions.
Figure 5. Molecular packing and intermolecular π–π interactions of 9 based
on the X-ray crystallography.
Investigation on a Polymer
For further investigation as practical materials, we examined
polymer synthesis (Scheme 3). 4,4′-Diaminodiphenyl ether
(DDE) was selected as a comonomer to obtain main-chain type
polymers. Although we initially tried copolymerization of 2 and
DDE, insoluble precipitates generated. This is probably because
of high crystallinity of the rod-like structure of the resulting
polymer. On the other hand, copolymerization of 6 and DDE
gave soluble polymer 12 thanks to the zig-zag structure
through the m-linking. Size exclusion chromatography (SEC)
showed a unimodal peak for 12 when the reaction was per-
formed at room temperature, suggesting that no cross-linking
occurred. On the other hand, when the reaction temperature
was raised to 110 °C, shoulder peaks due to cross-linking were
observed in the SEC chart (Figure 6a). The NMR spectroscopy
also indicates that the polymerization successfully proceeded
(Figure 6b). Excess amounts of morpholine were added to 12
to produce diaminomaleimide polymer 13. After the post-
functionalization, the original signals due to 12 completely dis-
appeared, and the signals due to the morpholino groups were
observed in the 1H-NMR spectrum of 13. The molecular weight
Figure 4. Molecular packings of 3 and 7 based on the X-ray crystallography.
On the contrary to p-linked dimer 3, m-linked dimer 7
showed more intense emission with shorter wavelength in the
solid state (λem = 595 nm, Φ = 11 %) than that in a solution
(λem = 611 nm, Φ = 6 %). The luminescent center of 7 was
insulated by the four morpholino groups similar as in 3, but
the phenylene linker cannot rotate because of the m-linking
structure (Figure 4b), meaning that the molecular motions of 7
are locked in the solid state. This is why the PL properties of 7
in the solid state were similar to those in the PMMA composite
films (λem = 592 nm, Φ = 16 %).
Scheme 3. Synthesis of diaminomaleimide polymer 13.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
4
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
of 13 estimated by the SEC decreased from that of 12, though studies elucidated the structure-properties relationships of the
no decomposition was detected by the NMR and SEC measure- diaminomaleimide dimers. In the solid state, the emission of 3
ments. This is probably because the incorporation of many was quenched via non-radiative deactivation due to the free
amino groups into the polymer chain promoted absorption to rotation of the p-phenylene linker. On the other hand, the rota-
the stationary phase to delay the elution time.
tion of the phenylene linker of 7 was locked because of the m-
linking structure, and the insulated luminescent center inten-
sively emitted. The intermolecular π–π interaction formed by
the p-toluidino groups probably lowered the emission efficien-
cies of 5 and 9 in their solid states. In addition, m-phenylene-
bismaleimide tetrachloride 6 can be used as a monomer. Nota-
bly, no cross-linking was observed, but post-modification with
morpholine was attained. The present study expands the
knowledge on the molecular design of luminescent materials
based on maleimide dyes.
Experimental Section
1. Materials
Toluene, triethylamine, ethyl acetate, hexane, methanol, THF, mor-
pholine, dichloromethane, m-phenylenediamine, chloroform, 4,4′-
diaminodiphenyl ether (DDE) were purchased from Nacalai Tesque,
Inc. Dichloro maleic anhydride (1), p-toluidine, p-phenylenediamine,
dimethysulfoxide, acetic acid, 4-methyltetrahydropyran (MTHP), dis-
tilled water, silica gel (Wakogel C-200), and magnesium sulfate an-
hydrous (MgSO4) were purchased from Wako Pure Chemical Indus-
try, Ltd. Poly(methyl methacrylate) (average Mw ~350,000 by GPC)
was purchased from Sigma Aldrich. All commercially available
chemicals were used without any purification.
Figure 6. (a) SEC traces (1.0 mL/min in THF) of 12 (reaction temperature, t =
110 °C and r.t.) and 13. (b) 1H-NMR (400 MHz in [D6]DMSO) of DDE, 6, 12,
and 13.
The optical properties of polymer 13 were examined; the
absorption spectrum was measured in a CH2Cl2 solution (c =
1.0 × 10–4 M per unit), and the PL spectra were measured in the
states of the pristine solids just after reprecipitaion, cast films
from a chloroform solution state, and 1 wt.-% PMMA composite.
The emission color and efficiency were dependent on the states
of the samples (Figure 7), though X-ray diffraction analysis
showed broad signals in all cases (Figure S23). This is probably
because morphologies of the polymers determined intermolec-
ular interactions between the luminescent centers, resulting in
the different PL properties.
2. Instruments
1H (400 MHz) and 13C (100 MHz) nuclear magnetic resonance (NMR)
spectra were recorded on a Bruker DPX-400 spectrometer (Bruker
Biospin GmbH, Rheinstetten, Germany) in CDCl3 using Me4Si as an
internal standard. The following abbreviations are used: s, singlet;
d, doublet; t, triplet; m, multiplet. High-resolution mass spectra
(HRMS) were obtained on a JEOL JMS-SX102A spectrometer. UV/Vis
spectra were recorded on a JASCO spectrophotometer V-670 KNN.
Emission and excitation spectra were obtained on an FP-8500
(JASCO), and absolute PL quantum yields (Φ) were determined us-
ing a JASCO ILFC-847S; the quantum yield of quinine sulfate refer-
ence was 0.52, which is in agreement with the literature value.[8]
Emission lifetimes were measured using Quantaurus-Tau (Hama-
matsu Photonics). Powder X-ray diffractions (PXRD) were recorded
on a Rigaku RAXIS RAPID II imaging plate area detector using
monochromated Cu-Kα radiation by rotating samples along the ꢀ-
axis and transformed to 2θ-I plot by software.
3. X-ray crystallographic data for single crystalline products
The single crystal was mounted on a nylon loop. Intensity data
were collected at room temperature on a Rigaku XtaLAB mini with
graphite monochromated Mo-Kα radiation. Readout was performed
in the 0.073 mm pixel mode. The data were collected at room tem-
perature to a maximum 2θ value of 55.0°. Data were processed by
Crystal Clear.[9] An empirical absorption correction[10] was applied.
The data were corrected for Lorentz and polarization effects. The
structure was solved by direct method[11] and expanded using Fou-
rier techniques. The non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were refined using the riding model. The
final cycle of full-matrix least-squares refinement on F2 was based
on observed reflections and variable parameters. All calculations
Figure 7. PL spectra (exited at excitation maxima) and photographs (excited
at 365 nm) of polymer 13 as pristine solid, cast film, and PMMA composite.
Conclusions
In summary, we synthesized four diaminomaleimide dimers and
one polymer to investigate the structures and emission proper-
ties of diaminomaleimides in their assembly states. The amino
groups and linking positions affected the packing structures in
the solid states to vary the PL properties as well as the solubility
and thermal stability. X-ray crystallography and computational were performed using the CrystalStructure[11] crystallographic soft-
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
ware package except for refinement, which was performed using
SHELXL2013.[12] Crystal data and more information on X-ray data
collection are summarized in Tables S1–3.
ane (250 mL) at 0 °C to obtain yellow solids of 6 (2.67 g, 6.58 mmol,
81 %). 1H NMR (CDCl3, 400 MHz): δ = 7.60 (t, J = 8.1 Hz, 1H), 7.50
(t, J = 1.8 Hz, 1H), 7.45 (q, J = 5.0 Hz, 2H) ppm; 13C NMR (CDCl3,
100 MHz): δ = 161.5, 133.8, 131.5, 130.1, 125.3, 122.5 ppm.
4. Synthetic procedure and characterization data
m-Phenylenebis(dimorpholino maleimide) (7).
p-Phenylenebismaleimide tetrachloride (2).
A mixture of 6 (0.303 g, 0.746 mmol) and morpholine (8 mL,
91.8 mmol) was heated under reflux condition for 16 h. The volatiles
were removed in vacuo. The residue was extracted with dichloro-
methane, and the solution was washed with water. The organic
layer was dried with MgSO4, and the solution was filtered. After
removal of the solvent, the residue was subjected to column chro-
matography over silica gel (eluent: hexane/ethyl acetate = 1:1). The
obtained products were recrystallized from dichloromethane, ethyl
acetate, and hexane to give orange crystals of 7 (0.0623 g,
0.102 mmol, 14 %). 1H NMR (CDCl3, 400 MHz): δ = 7.46 (t, J = 8.1 Hz,
1H), 7.38 (t, J = 2.0 Hz, 1H), 7.30 (d, J = 1.0 Hz, 1H), 7.28 (d, J =
1.0 Hz, 1H), 3.75 (t, J = 4.7 Hz, 16H), 3.56 (t, J = 4.7 Hz, 16H) ppm;
13C NMR (CDCl3, 100 MHz): δ = 166.7, 131.9, 128.9, 126.0, 124.3,
123.0, 67.2, 48.9 ppm; HRMS (FAB) calcd. for C30H36N6O8 [M]+:
608.2595, found 608.2595.
To a toluene solution (10 mL) of 1 (1.01 g, 6.05 mmol) was added
an acetic acid solution (30 mL) of p-phenylenediamine (0.261 g,
2.41 mmol) dropwise. After refluxing for 2 h, dark yellow precipi-
tates were generated. The collected precipitates were washed with
methanol to obtain 2 (0.911 g, 2.24 mmol, 93 %). The solubility of
2 was too low to conduct NMR spectroscopy and mass analysis.
Anal. calcd. for C14H4Cl4N2O4: C 41.42, H 0.99, N 6.90; found C 41.57,
H 1.16, N 7.01.
p-Phenylenebis(dimorpholino maleimide) (3).
A mixture of 2 (0.251 g, 0.618 mmol) and morpholine (10 mL,
115 mmol) was heated under reflux for 24 h. The volatiles were
removed in vacuo. The residue was extracted with chloroform, and
the solution was washed with water. The organic layer was dried
with MgSO4, and the solution was filtered. After removal of the
solvent, the residue was washed with methanol, and then subjected
to recrystallization from dichloromethane and methanol to obtain
m-Phenylenebis(chloro-p-toluidino-maleimide) (8).
A THF solution (20 mL) of 6 (0.301 g, 0.746 mmol) and p-toluidine
(0.164 g, 1.53 mmol) was heated under reflux condition for 2 h. The
volatiles were removed in vacuo. The residue was extracted with
ethyl acetate and THF, and the solution was washed with water. The
organic layer was dried with MgSO4, and the solution was filtered.
After removal of the solvents, the products were washed with tolu-
ene to obtain yellow solids of 8 (0.344 g, 0.628 mmol, 84 %). 1H
NMR (CDCl3, 400 MHz): δ = 7.62 (t, J = 1.9 Hz, 1H), 7.56 (q, J =
8.0 Hz, 1H), 7.47–7.45 (m, 2H), 7.22 (d, J = 4.1 Hz, 4H), 7.18 (s, 2H),
7.12 (d, J = 4.2 Hz, 2H), 2.38 (s, 6H) ppm; 13C NMR (CDCl3, 100 MHz):
δ = 166.0, 164.9, 136.7, 136.5, 132.8, 132.1, 129.54, 129.49, 124.2,
124.0, 122.0, 93.6, 21.0 ppm; HRMS (FAB) calcd. for C28H20Cl2N4O4
[M]+: 546.0862, found 547.0944.
1
red crystals (0.120 g, 0.197 mmol, 32 %). H NMR (CDCl3, 400 MHz):
δ = 7.38 (s, 4H), 3.76 (t, J = 4.7 Hz, 16H), 3.57 (t, J = 4.7 Hz, 17H)
ppm; 13C NMR (CDCl3, 100 MHz): δ = 166.8, 130.2, 126.2, 126.0, 67.2,
48.9 ppm; HRMS (FAB) calcd. for C30H36N6O8 [M]+: 608.2595, found
608.2607.
p-Phenylenebis(chloro-p-toluidino-maleimide) (4).
A DMSO solution (10 mL) of 2 (0.301 g, 0.741 mmol) and p-toluidine
(0.198 g, 1.85 mmol) was heated at 120 °C for 4 h. After cooling
to room temperature, yellow precipitates were generated, and the
collected solids were washed DMSO and methanol to obtain 4
1
(0.184 g, 0.336 mmol, 45 %). H NMR (CDCl3, 400 MHz): δ = 9.96 (s,
2H), 7.52 (s, 4H), 7.20 (d, J = 4.1 Hz, 4H), 7.14 (d, J = 4.1 Hz, 4H),
2.31 (s, 6H) ppm. The solubility of 4 was too low to conduct 13C-
NMR spectroscopy and mass analysis. Anal. calcd. for C28H20Cl2N4O4:
C 61.44, H 3.68, N 10.24; found C 61.33, H 3.71, N 10.13.
m-Phenylenebis(morpholino-p-toluidino-maleimide) (9).
A mixture of 8 (0.300 g, 0.548 mmol) and morpholine (10 mL,
115 mmol) was heated under reflux condition for 24 h. The volatiles
were removed in vacuo. The residue was extracted with dichloro-
methane, and the solution was washed with water. The organic
layer was dried with MgSO4, and the solution was filtered. After
removal of the solvent, the residue was subjected to column chro-
matography over silica gel (eluent: hexane/ethyl acetate = 7:3). The
obtained products were recrystallized from dichloromethane, ethyl
acetate, and hexane to give red crystals of 9 (0.0650 g, 0.100 mmol,
p-Phenylenebis(morpholino-p-toluidino-maleimide) (5).
A mixture of 4 (0.120 g, 0.186 mmol) and morpholine (5 mL,
57.4 mmol) was heated under reflux condition for 16 h. The volatiles
were removed in vacuo. The residue was extracted with dichloro-
methane, and the solution was washed with water. The organic
layer was dried with MgSO4, and the solution was filtered. After
removal of the solvent, the residue was washed with methanol, and
then subjected to recrystallization from chloroform and methanol
to obtain red crystals of 5 (0.020 g, 0.0308 mmol, 17 %). 1H NMR
(CDCl3, 400 MHz): δ = 7.47 (s, 4H), 7.13 (d, J = 4.2 Hz, 4H), 6.81 (d,
J = 4.1 Hz, 4H), 6.14 (s, 2H), 3.52 (t, J = 4.6 Hz, 8H), 3.34 (t, J = 4.6 Hz,
8H), 2.33 (s, 6H) ppm. The solubility of 5 was too low to conduct
13C-NMR spectroscopy. HRMS (FAB) calcd. for C36H36N6O8 [M]+:
648.2696, found 648.2704.
1
18 %). H NMR (CDCl3, 400 MHz): δ = 7.54–7.48 (m, 2H), 7.39–7.36
(m, 2H), 7.13 (d, J = 4.1 Hz, 4H), 6.81 (d, J = 4.2 Hz, 4H), 6.15 (s, 2H),
3.51 (t, J = 4.6 Hz, 8H), 3.32 (t, J = 4.6 Hz, 8H), 2.33 (s, 6H) ppm; 13C
NMR (CDCl3, 100 MHz): δ = 167.6, 167.2, 137.5, 132.2, 131.8, 129.5,
129.1, 123.8, 122.8, 122.2, 118.6, 117.0, 66.8, 48.4, 20.7 ppm. Melting
point: 225.5–226.7 °C.
Polymer 12.
A THF solution (50 mL) of 6 (1.00 g, 2.46 mmol), DDE (0.493 g,
2.46 mmol), and triethylamine (0.503 g, 4.97 mmol) was stirred at
room temperature for 3 h. The volatiles were remove in vacuo, and
the residue was washed with mixed solvent (methanol/water = 7:3).
m-Phenylenebismaleimide tetrachloride (6).
To an MTHP solution (30 mL) of 1 (3.02 g, 18.1 mmol) was added
an acetic acid solution (90 mL) of m-phenylenediamine (0.885 g,
8.18 mmol) dropwise. After refluxing for 3 h, the volatiles were re- The remaining solids were subjected to reprecipitation from a THF
moved in vacuo. The residue was extracted with ethyl acetate, and
the solution was washed with 10 % aqueous solution of sodium
carbonate. The organic layer was dried with MgSO4, and the solu-
tion was filtered. The solvent was removed in vacuo, and the residue
was subjected reprecipitation from a THF solution (15 mL) to hex-
solution (15 mL) to water (250 mL) to obtain yellow solids of 12
(1.21 g, 81 %). H NMR (CDCl3, 400 MHz): δ = 10.00 (br, 2H), 7.65–
7.61 (br, 1H), 7.47–7.45 (br, 3H), 7.29–7.27 (br, 4H), 7.08–7.06 (br, 4H)
ppm; 13C NMR (CDCl3, 100 MHz): δ = 166.5, 164.7, 154.6, 139.3,
132.8, 132.5, 129.7, 126.6, 125.2, 120.0, 118.8, 92.3 ppm.
1
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[3] a) T. Kato, K. Naka, Chem. Lett. 2012, 41, 1445; b) K. Kizaki, H. Imoto, T.
Kato, K. Naka, Tetrahedron 2015, 71, 643; c) H. Imoto, K. Kizaki, S. Watase,
K. Matsukawa, K. Naka, Chem. Eur. J. 2015, 21, 12105; d) H. Imoto, K.
Kizaki, K. Naka, Chem. Asian J. 2015, 10, 1698; e) H. Imoto, K. Nohmi, K.
Kizaki, S. Watase, K. Matsukawa, S. Yamamoto, M. Mitsuishi, K. Naka, RSC
Adv. 2015, 5, 94344; f) H. Imoto, R. Fujii, K. Naka, Eur. J. Org. Chem. 2018,
2018, 837.
[4] a) M. Boominathan, V. Sathish, M. Nagaraj, N. Bhuvanesh, S. Muthusubra-
manian, S. Rajagopal, RSC Adv. 2013, 3, 22246; b) Q. Zhu, Z. Ye, W. Yang,
X. Cai, B. Z. Tang, J. Org. Chem. 2017, 82, 1096; c) Y. Xie, J. T. Husband,
M. Torrent-Sucarrat, H. Yang, W. Liu, R. K. O'Reilly, Chem. Commun. 2018,
54, 3339; d) Z. Yang, Y. Guo, S.-L. Ai, S.-X. Wang, J.-Z. Zhang, Y.-X. Zhang,
Q.-C. Zou, H.-X. Wang, Mater. Chem. Front. ahead of print (https://doi.org/
10.1039/c8qm00559a).
[5] a) Y. Arai, T. Kontani, T. Koizumi, J. Chem. Soc., Perkin Trans. 1 1994, 15;
b) E. J. Corey, M. A. Letavic, J. Am. Chem. Soc. 1995, 117, 9616; c) B. M.
Trost, L. S. Kallander, J. Org. Chem. 1999, 64, 5427; d) M. Oikawa, S. Sasaki,
M. Sakai, Y. Ishikawa, R. Sakai, Eur. J. Org. Chem. 2012, 2012, 5789.
[6] CCDC 1891545 (for 3), 1891544 (for 7), and 1891546 (for 9) contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data Cen-
tre.
Polymer 13.
A THF solution (5 mL) of 12 (0.101 g), triethylamine (0.0390 g,
0.385 mmol), morpholine (0.318 g, 3.65 mmol) was heated under
reflux condition for 16 h. The volatiles were removed in vacuo. The
residue was extracted with chloroform, and the solution was
washed with water. The organic layer was dried with MgSO4, and
the solution was filtered. The solvent was removed in vacuo, and
the residue was subjected to reprecipitation from a THF solution
(10 mL) to hexane (200 mL) at 0 °C to obtain orange solids of 13
1
(0.101 g, 76 %). H NMR ([D6]DMSO, 400 MHz): δ8.23 (br, 2H), 7.57–
7.53 (br, 1H), 7.35–7.33 (br, 3H), 6.91–6.81 (br, 8H), 3.42–3.40 (br,
10H), 3.30–3.27 (br, 8H) ppm; 13C NMR (CDCl3, 100 MHz): δ = 167.6,
167.0, 135.6, 132.2, 129.1, 123.8, 129.1, 120.4, 119.9, 119.2, 118.2,
116.3, 66.8, 48.4 ppm.
5. Fabrication of cast films
A chloroform solution (1.6 mL) of PMMA (100 mg) and a dye was
prepared. The solution was drop-casted onto the silicon wafer, and
dried at room temperature for 3 h.
[7] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Na-
katsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.
Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A.
Montgomery Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Broth-
ers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghava-
chari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega,
J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski,
G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö.
Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09,
Revision C.01, Gaussian, Inc., Wallingford CT, 2009.
[8] Fluorescence Measurements, Application to bioscience, Measurement
method, Series 3. Spectroscopical Society of Japan, Academic Publica-
tion Center.
[9] CrystalClear: Data Collection and Processing Software, Rigaku Corporation
(1998–2014). Tokyo 196–8666, Japan.
[10] SIR2011: M. C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G. L. Cascar-
ano, C. Giacovazzo, M. Mallamo, A. Mazzone, G. Polidori, R. Spagna, J.
Appl. Crystallogr. 2012, 45, 357.
Acknowledgments
We thank Prof. M. Shimizu and Mr. M. Mineyama of Kyoto Insti-
tute of Technology for emission lifetime measurements.
Keywords: Solid-state emission · Density functional theory
calculation · Fluorescence · X-ray diffraction
[1] a) B. K. Kaletaş, R. M. Williams, B. König, L. D. Cola, Chem. Commun. 2002,
776; b) H.-C. Yeh, W.-C. Wu, C.-T. Chen, Chem. Commun. 2003, 404; c) C.-
W. Chiu, T. J. Chow, C.-H. Chuen, H.-M. Lin, Y.-T. Tao, Chem. Mater. 2003,
15, 4527; d) L. Ding, H.-Z. Ying, Y. Zhou, T. Lei, J. Pei, Org. Lett. 2010, 12,
5522; e) M. E. Jang, T. Yasuda, J. Lee, S. Y. Lee, C. Adachi, Chem. Lett.
2015, 44, 1248; f) H. Sakai, T. Kubota, J. Yuasa, Y. Araki, T. Sakanoue, T.
Takenobu, T. Wada, T. Kawai, T. Hasobe, J. Phys. Chem. C 2016, 120, 7860;
g) Z. Mahmood, J. Zhao, J. Org. Chem. 2016, 81, 587; h) J. Wang, R.
Zheng, H. Chen, H. Yao, L. Yan, J. Wei, Z. Lin, Q. Ling, Org. Biomol. Chem.
2018, 16, 130; i) N. Venkatramaiah, G. D. Kumar, Y. Chandrasekaran, R.
Ganduri, S. Patil, ACS Appl. Mater. Interfaces 2018, 10, 3838.
[2] a) Q. Peng, Z. Lu, Y. Huang, M. Xie, D. Xiao, D. Zou, J. Mater. Chem. 2003,
13, 1570; b) T.-Z. Liu, Y. Chen, Polymer 2005, 46, 10383; c) Z. Lin, Y.-D.
Lin, C.-Y. Wu, P.-T. Chow, C.-H. Sun, T. J. Chow, Macromolecules 2010, 43,
5925; d) K. Onimura, M. Matsushima, K. Yamabuki, T. Oishi, Polym. J.
2010, 42, 290; e) M. Nakamura, K. Yamabuki, T. Oishi, K. Onimura, J.
Polym. Sci., Part A J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4945.
[11] CrystalStructure 4.1: Crystal Structure Analysis Package, Rigaku Corpora-
tion (2000–2014). Tokyo 196–8666, Japan.
[12] SHELXL2013: G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
Received: February 5, 2019
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Solid-State Emission
Several solid-state emissive diamino-
maleimide dimers and a polymer were
synthesized. The derivatives show
photoluminescence at long wave-
length emission up to 643 nm.
H. Imoto, R. Fujii, K. Naka* .............. 1–8
Solid-State Emissive Diaminomale-
imide Dimers and a Polymer – Syn-
theses, Structures and Optical Prop-
erties
DOI: 10.1002/ejoc.201900195
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim