HAPPY Dyes as Light Amplification Media in Thin Films

Article abstract of DOI:10.1021/acs.joc.0c02574

A series of 1H amorphous tri-phenyl pyridine (HAPPY) dyes have been synthesized from luminescent triphenyl-group-containing 2-methyl-6-styryl-substituted-4H-pyran-4-ylidene derivatives in reactions with benzylamine and investigated for suitability as solution-processable light-emitting medium components in thin films for amplified spontaneous emission (ASE). Conversion of a 4H-pyrane ring into a 1H-pyridine fragment enables aggregation-induced emission enhancement (AIEE) behavior in the target products and slightly increases thermal stability, glass transition temperatures, and ASE efficiency with PLQY up to 15% and ASE thresholds as low as 46 μJ/cm2 in neat spin-cast films, although thermal and photophysical properties are mostly dominated by the incorporated electron acceptors. Continued lasing parameter efficiency parameter improvement experiments revealed that no further optimization of HAPPY dyes by doping in polymer matrixes is required as the amplified spontaneous emission thresholds were lowest in pure neat films due to the AIEE phenomenon.

Full text of DOI:10.1021/acs.joc.0c02574

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HAPPY Dyes as Light Amplification Media in Thin Films
Elmars Zarins,* Julija Pervenecka, Elina Misina, Oleksandr Bezvikonnyi, Aivars Vembris, Karlis Balodis,
Dmytro Volyniuk, Juozas V. Grazulevicius, and Valdis Kokars
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ABSTRACT: A series of 1H amorphous tri-phenyl pyridine (HAPPY)
dyes have been synthesized from luminescent triphenyl-group-
containing 2-methyl-6-styryl-substituted-4H-pyran-4-ylidene derivatives
in reactions with benzylamine and investigated for suitability as
solution-processable light-emitting medium components in thin films
for amplified spontaneous emission (ASE). Conversion of a 4H-pyrane
ring into a 1H-pyridine fragment enables aggregation-induced emission
enhancement (AIEE) behavior in the target products and slightly
increases thermal stability, glass transition temperatures, and ASE
efficiency with PLQY up to 15% and ASE thresholds as low as 46 μJ/
cm2 in neat spin-cast films, although thermal and photophysical
properties are mostly dominated by the incorporated electron acceptors.
Continued lasing parameter efficiency parameter improvement experi-
ments revealed that no further optimization of HAPPY dyes by doping in polymer matrixes is required as the amplified spontaneous
emission thresholds were lowest in pure neat films due to the AIEE phenomenon.
The first conversion of 4H-pyran-4-ylidene-fragment-con-
taining compounds into the respective 1H-pyridine-4-ylidene
derivatives was reported by Kato et al.12 in 1960. Nearly 30 years
later, several synthesis possibilities of 2-(4-pyridinyl)indane-1,3-
diones were described:13 (1) condensation of 4-methylpyridine
with ethyl phthalates in the absence of catalyst; (2) oxidative
condensation of N-alkylpyridinium bromides with indane-1,3-
diones; (3) aminolysis of 2-(4H-pyranylidene) indane-1,3-
diones, which was also the method reported previously by
Kato.12 In 2006, Peng et al.14 synthesized fluorescent polymers
with incorporated 1H-pyridine-4-ylidene structural fragments. A
detailed investigation of 4H-pyran-4-ylidene-fragment-contain-
ing compounds with primary and secondary amines15 and well-
defined evidence of 1H-pyridine-4-ylidene derivative chemical
structures by X-ray analysis were reported several years
later.16−18 Recently, several 2,6-bis-styryl-substituted-1H-pyr-
idine-4-ylidene derivatives were successfully synthesized and
reported as materials with aggregation-induced emission
enhancement (AIEE)19 and multicolor switching proper-
ties.18,20−23 Merocyanines are known for their prominent
glass-forming and solid-state emission properties.24 While
many J-aggregates usually exhibit strong fluorescence, the
INTRODUCTION
■
The demonstration of optical trapping and manipulation of
neutral particles by lasers by A. Askhin,1 awarded a Nobel Prize
in physics in 2018, opened new future perspectives for materials
that can be used for laser radiation generation. Organic materials
are good candidates to be applied as the gain medium
components in lasers due to their low-cost production
possibilities, good optical and photochemical stabilities, high
optical quality of gain media, and a wide range of flexibility
through chemical structure modifications.2−4 Among such
materials, a typical gain medium system is composed of blends
of aluminum tris(8-hydoxyquinoline) as a host and 4-(dicyano-
methylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran
(DCM) as a guest.2−8 To increase the gain medium efficiency,
the active lasing components can be doped in a matrix of a host,8
which can also be a polymer.9 The operation principle of lasing
̈
systems based on these materials is a Forster resonance energy
transfer (FRET) from the excited host to the guest dye, which
occurs due to the overlapping of their absorption and emission
bands.2−8 The most notable advantages of this design are a
significant reduction of reabsorption losses, low thresholds, and
a remarkable increase in laser durability.2−4 Such gain media are
usually produced by vacuum deposition,2−8 but several solution-
processable system components also have been introduced.9,10
A number of various DCM derivatives were also synthesized and
investigated for applications in communications, organic light-
emitting diodes (OLED), nonlinear optics (NLO), and organic
solar cells.11 However, in all of those materials, 4H-pyran-4-
ylidene fragment always remained unchanged.
Received: October 29, 2020
Published: January 29, 2021
https://dx.doi.org/10.1021/acs.joc.0c02574
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Scheme 1. Synthesis of 1H-Pyridine Model Compounds from Luminescent 4H-Pyran-4-ylidene Derivatives
examples of a merocyanine H-aggregate exhibiting well-resolved
emission with a longer fluorescence lifetime relative to that of
the monomer was reported recently,25 proving the possibility of
the usage of such kind of derivatives as materials exhibiting
AIEE.26 However, none of these compounds so far were
reported as possible light amplification media.
Herein we report the synthesis of 1H amorphous tri-phenyl
pyridine (HAPPY) dyes from the respective luminescent
triphenyl group containing 2-methyl-6-styryl-substituted-4H-
pyran-4-ylidene derivatives. The results of the investigation of
their thermal, glass-forming, light-emitting, and amplified
spontaneous emission (ASE) properties in solution-processable
thin films are described.
(DCM) with benzylamine did not afford the desired model
compound DE-1 even in trace amounts. NMR and HPLC-MS
analyses indicated successful 4H-pyrane ring conversion into the
1H-pyridine fragment with the additional 1,2-addition of the
benzylamine molecule to the malononitrile electron acceptor
fragment affording compound DE-1* (see Supporting Informa-
tion, pages S10−S16). No amine 1,2-additions to malononitrile
acceptors were observed in literature14,15,21 with similar
chemical structure 4H-pyran-4-ylidene-fragment-containing
molecules and different reactants; however, in this research,
those reaction conditions were not applied.
The chemical shifts in NMR spectra of model compounds ZE-
1 and JE-1 NMR spectra are complex due to the close sterical
interactions of benzyl and 4-(N,N-dimethylaminostyryl) frag-
ments, which slow down rotations between different con-
formations (Scheme 2). Peaks from both conformers are
RESULTS AND DISCUSSION
■
Synthesis of Dyes and Their Characterization. To test
the conversion efficiency and to tune the reaction conditions for
the donor (D)−acceptor (A) group containing 4H-pyran-4-
ylidene derivative conversion into 1H-pyridine-fragment-con-
taining compounds, several model compounds (1−3) have been
synthesized as described previously.28 Benzylamine was selected
to increase the glass transition temperatures and enhance
amorphous structure formation in the solid state of the desired
target products. 1H-Pyridine-fragment-containing model com-
pounds ZE-1 and JE-1 were successfully obtained (Scheme 1) by
a slightly modified synthesis method reported by Kato et al.12
from 4H-pyran-4-ylidene precursors 2 and 3. In contrast to the
research reported previously,15 the reaction of 4-(dicyano-
methylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran
Scheme 2. Conformation Inversions of 1H-Pyridine Model
a
Compounds ZE-1 and JE-1
a
A = the electron withdrawing substituent; see Scheme 1.
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a
Scheme 3. Synthesis of HAPPY Dyes
a
Bis-styryl-4H-pyran-4-ylidene derivatives ZWK-2, JWK-2, MWK-2, and EWK-2 (abbreviation used: WK-2 dyes) were obtained as byproducts in
the synthesis of necessary reactants ZWK-1, JWK-1, MWK-1, and EWK-1 (abbreviation used: WK-1 dyes). Tr is the abbreviation of the
triphenylmethane group.
observed at varying intensities and are dependent on the
incorporated electron acceptor (see Supporting Information,
pages S23−S31). The hydrogen bond formation possibility
between JE-1 molecules is most likely the reason why the S-trans
conformation was dominant.
Table 1. Yields and Thermal Properties of WK-1, WK-2, and
HAPPY Dyes
a
All HAPPY dyes were synthesized in a similar way like model
compounds JE-1 and ZE-1 from the respective 4H-pyran-4-
ylidene derivatives according to known procedures24 and were
obtained in high yields (Scheme 3). S-cis conformation was
dominant for all of the synthesized HAPPY dyes (see Supporting
Information, pages S47−S70). The increased distance between
the molecules of JE-1Tr due to the bulky groups most likely
prevented possible aggregation through hydrogen bonds that
enhances s-trans conformation in JE-1.
Thermal and Glass-Forming Properties. Thermal
characteristics of synthesized HAPPY dyes as well as related
reactants (WK-1 dyes) and their byproducts (WK-2 dyes) are
summarized in Table 1.
Compounds with free N−H groups (JWK-2, JWK-1, and JE-
1Tr) show higher glass transition temperatures due to the
hydrogen bond formation. No additional relations could be
observed from the comparison of thermal characteristics of all
investigated dyes (WK-1, WK-2, and HAPPY). It means that
thermal stabilities and glass transition temperatures of the dyes
are mostly influenced by the incorporated electron acceptor
fragments. Conversion of a 4H-pyrane ring into a 1H-pyridine
fragment in reaction with benzylamine increased thermal
stability and glass transition temperatures of ZE-1Tr, JE-1Tr,
and ME-1Tr; however, the opposite regularity was observed for
EE-1Tr. All of the investigated dyes showed thermal stability of
260 °C and above, good neat-film formation ability by solution-
processing (see Supporting Information, pages S79 and S80),
and glass transition temperatures up to 140 °C. No definite
melting points were observed for synthesized HAPPY dyes,
a
Tg = glass transition temperature. Td = thermal decomposition
temperature at 5% weight loss. Symbols *, +, and are used as
identifiers for WK-1, WK-2, and HAPPY, respectively.
:)
which additionally indicate the formation of amorphous
structures in their solid state.
Photophysical Properties. A 10−30 nm redshift of
absorption and photoluminescence bands of synthesized
HAPPY dyes in neat films (see Figure 2) in relation to their
dichloromethane solutions (Figure 1) indicates slight sensitivity
of photophysical properties of compounds ZE-1Tr, JE-1Tr, ME-
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1Tr, and EE-1Tr to the polarity of the surrounding solvation
environment.
The largest redshift was observed for ZE-1Tr bearing an
indene-1,3(2H)-dione acceptor moiety. The conversion of a
4H-pyrane ring to a 1H-pyridine fragment had a significant
influence on the photophysical properties in the solid state as the
absorption and PL maxima of HAPPY dyes blueshifted by 54−
130 nm (Table 2) in comparison to those of their respective
precursors (WK-1 dyes). WK-2 dyes contain an additional
electron donor fragment, which leads to an even greater redshift
of their absorption and photoluminescence in relation to those
of HAPPY dyes.
Distinct amplified spontaneous emission (ASE) was observed
in three out of four HAPPY dye neat films (JE-1Tr, ME-1Tr, and
EE-1Tr) (Table 2 and Figure 3), while only a small extra peak
Figure 1. Absorption (solid lines) and photoluminescence (dashed
lines) spectra of the solutions of HAPPY dyes in dichloromethane: 1,
EE-1Tr; 2, ME-1Tr; 3, JE-1Tr; 4, ZE-1Tr.
Figure 3. Amplified spontaneous emission of HAPPY dyes in pure thin
films: 1, EE-1Tr; 2, ME-1Tr; 3, JE-1Tr.
appeared in the emission spectra of the ZE-1Tr film, which could
be attributed to the phenomena. The respective precursor ZWK-
1 also showed the lowest threshold energy among WK-1 dyes. It
means that dyes with an indene-1,3(2H)-dione acceptor were
the least effective as materials for light amplification. For an
effective lasing parameter comparison of synthesized dyes,
PLQY and ASE threshold energy should be evaluated together.
Even though WK-1 dye neat films exhibit about 2 times higher
PLQYs (in the case of JWK-1 → JE-1Tr and EWK-1 → EE-1Tr
modifications), obtained HAPPY dyes still showed lower
thresholds. Despite the largest overlap between the absorption
Figure 2. Absorption (solid lines) and photoluminescence (dashed
lines) spectra of neat thin films of HAPPY dyes: 1, EE-1Tr; 2, ME-1Tr;
3, JE-1Tr; 4, ZE-1Tr.
Table 2. Photophysical Properties of Pure Thin Films of WK-1, WK-2, and HAPPY Dyes in Pure Thin Films
compound
λabs, nm
λPL, nm
699;827
fwhmPL, nm
PLQY, %
λASE, nm
fwhmASE, nm
Eth, μJ/cm2
ref
ZWK-2+
ZWK-1*
ZE-1Tr:)
JWK-2+
JWK-1*
JE-1Tr:)
MWK-2+
MWK-1*
ME-1Tr:)
EWK-2+
EWK-1*
EE-1Tr:)
519
498
431
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
300
117
208
165
122
143
135
143
157
145
158
119
2
2
2
2
2
2
2
2
2
2
2
2
1.2M
10.7M
2.8
6.1M
13.7M
5.9
24, 27
24, 27
this work
24, 27
24, 27
this work
this work
this work
this work
this work
this work
this work
668
612
717
673
576
694
702
584
733
701
571
699
603
2
2
18
2
225 20
499;572
514
386
501
491
395
525
523
413
683
603
714
674
615
743
701
614
2
2
2
2
2
2
2
2
15
19
16
20
23
16
21
12
2
2
2
2
2
2
2
2
95 10
76.5 7.6
200.8 20.1
65.2 6.5
64.5 6.4
347.0 34.7
156.0 15.6
46.0 4.6
2.2
11.6
15.1
3.2
9.6
5.1
a
λabs: wavelength of absorption maximum. λPL: wavelength of photoluminescence maximum. PLQY: photoluminescence quantum yield. λASE
:
wavelength of amplified spontaneous emission maximum. fwhm: the full width of half-maximum of PL or amplified spontaneous emission band.
+
Eth: irradiation threshold energy density at which amplified spontaneous emission appears. Symbols *, , and :) are used as identifiers for WK-1,
WK-2, and HAPPY, respectively. M: measured in spin-cast films that were about 10 times thinner than samples reported in ref 24.
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and photoluminescence spectral regions, EE-1Tr has the lowest
ASE excitation threshold energy value: 46 μJ/cm2, which is
approximately three times lower than the ASE excitation
threshold value of its predecessor, EWK-1 (Figure 4).
Figure 4. Emission intensity dependence on irradiation energy density
in the EE-1Tr film.
Threshold energy densities of MWK-1 and ME-1Tr were
nearly the same, but the PLQY was higher for ME-1Tr by about
1.3 times.
ASE properties of several WK-1 and WK-2 dyes were
investigated as described,27 and no such effect was observed in
ZWK-2 and JWK-2 neat films. Surprisingly, the ASE effect was
detected in MWK-2 and EWK-2 films in the infrared (IR)
region. Even though PLQYs in MWK-2 and EWK-2 films were
low and thresholds were relatively high, the efficiency of these
materials is competitive with IR radiation amplifying com-
pounds obtained previously.28,29 The 10 and 20 nm red shift of
EWK-2 and MWK-2 ASE peaks from their photoluminescence
maximum is in accordance with the theoretical statement that
the cross section of the stimulated emission should be larger to
the right side of the photoluminescence maximum.30
Fluorescence lifetimes of all investigated dyes are below 1 ns
(see Supporting Information, pages S89−S93). All of these
results indicate that HAPPY dyes are more promising materials
for light amplification in relation to WK-1 and WK-2 dyes, and
the efficiency increase is mostly dependent on the incorporated
electron acceptor fragment.
To improve the lasing efficiency parameters (PLQY and Eth)
by increasing the distance and disabling interactions between
molecules in the solid state, the three most efficient HAPPY dyes
(JE-1Tr, ME-1Tr, and EE-1Tr) were doped in Zeonex31 matrix.
PLQY increased only slightly (see Supporting Information, page
S94); however, no ASE was observed at all in such host−guest
systems. It may be due to two reasons: low solubility of the
investigated HAPPY dye in Zeonex, which causes emitted light
scattering instead of amplification and a small difference of
refractive index between Zeonex and the glass substrate, which
reduces the waveguide efficiency. Therefore a different
polymer−polyvinylcarbazole (PVK) was used due to proven
suitability in lasing systems.9 PLQY and ASE threshold energy
dependence from doped dye ME-1Tr and EE-1Tr mass/weight
concentrations (wt%) in PVK are shown in Figure 5. While a
clear decrease of PLQY by increasing the dye content in PVK is
clearly seen, no such trend could be established from ASE
threshold energies. Even though low ASE thresholds are
observed at 30 wt % dye ME-1Tr and EE-1Tr content in PVK
Figure 5. ASE threshold energy (top graph) and PLQY (bottom graph)
in ME-1Tr and EE-1Tr dye-doped systems in PVK.
as well as at 70 wt % dye ME-1Tr content in PVK, the lowest
values are still obtained in pure dye films despite a low PLQY
(see Table 2). No ASE was observed in 1 wt % ME-1Tr and 1 wt
%, 5 wt %, 10 wt % EE-1Tr dye-doped PVK films. Increasing dye
ME-1Tr and EE-1Tr concentrations (wt%) in PVK caused a
redshift of the PL maxima wavelength of the respective host−
guest systems (see Supporting Information, pages S85−S87),
like for 4H-pyran-4ylidene-fragment-containing reactants.9,32
However, increasing dye ME-1Tr and EE-1Tr concentrations
(wt%) in PVK caused the blue shift of ASE maxima wavelengths
(see Supporting Information, pages S85−S87), which was the
exact opposite in comparison to reactant host−guest sys-
tems.9,31 Obtained results in PVK matrixes could be explained
by a possible aggregation-induced emission enhancement
(AIEE) phenomenon for HAPPY dyes in neat films.
As the PLQY of the solid films of the investigated HAPPY
dyes were also higher than those of their deoxygenated toluene
solutions (see Supporting Information, page S94), a classical
experiment to test aggregation-induced emission properties was
conducted (see Figure 6).
At 80−90% water content, a remarkable increase of PL
intensity was observed for dye JE-1Tr and ME-1Tr samples. The
reduction of PL intensity at 90−99% water content is apparently
due to the uneven distribution of dye aggregates in a cuvette that
leads to the emitted light scattering. The lowest-energy
absorption bands of dilute THF solutions of all the compounds
(see Figure 91S, page S97) observed at ca. 470 nm was slightly
hypochromically shifted in comparison to the corresponding
bands of the dispersions in the mixtures of THF and water with
99% volume fraction of water. The shift is caused by the different
polarity of the media due to the different dielectric constants of
water and THF, which are 80 and 7.5, respectively. The level-off
tail was observed for the dispersions of the compounds at the
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PLQY several times; however, ASE thresholds were still the
lowest for pure neat films. This observation shows that no
further optimization by doping of laser dyes with AIEE is
required as the most efficient light amplification parameters are
achieved for pure films. Similar results may also be obtainable for
other organic molecules exhibiting ASE and AIEE properties.
EXPERIMENTAL SECTION
■
Unless specifically stated otherwise, all reactions were performed under
ambient conditions. Starting reagents necessary for the synthesis of dyes
were purchased as commercial products from Acros Organics, Sigma-
Aldrich, Fisher Chemical, and Alfa-Aesar and used as received. Where
required, organic solvents and catalysts (pyridine, piperidine, dichloro-
methane, chloroform, triehtylamine) were dried by refluxing with
calcium hydride (or phosphorus pentoxide) and distilled. The 1H NMR
spectra were obtained on a Bruker AVANCE spectrometer, 300 MHz at
298 K. NMR multiplicities are abbreviated as follows: s = singlet, d =
doublet, t = triplet, m = multiplet, br = broad signal. Coupling constants,
J, are given in hertz (Hz). NOESY spectra of 1H-pyridine model
compounds were acquired on a Bruker AVANCE spectrometer, 500
MHz at 298 K. The elemental analyses were obtained with an Euro
Vector EA 300 element analyzer. The purity and the ratio of conformers
were analyzed with Waters Alliance 2695 HPLC equipped with an
XTerra MS C18 5 μm 2.1 mm × 100 mm column (0.2 mL/min flow),
Waters 2996 PDA detector (250−800 nm), and Waters EMD 1000
(ESI) mass spectrometer (cone voltage = 30 V). Gradient elution was
used (0.5% HCOOH buffer in deionized water, MeCN, and CH2Cl2).
The detector is unable to register m/z peaks higher than 1080. Detailed
information about structure characterization (1H NMR spectra and
HPLC-MS analysis) and physical properties of every chemical
substance obtained in this article is available within the associated
Supporting Information. Synthesized WK-1 dyes (ZWK-1, JWK-1,
MWK-1, and EWK-1) and WK-2 dyes (ZWK-2, JWK-2, MWK-2, and
EWK-2) are partly amorphous. Therefore, their melting points are not a
definite way of characterization as those may vary depending on the
content of the amorphous and crystalline forms in the synthesized
batch.
General Method I: Synthesis of 1H-Pyridine Model Com-
pounds and HAPPY Dyes. To a solution of the corresponding 2-
styryl-subsituted-6-methyl-4H-pyran-4-ylidene derivative (0.45 mmol)
in chloroform (10 mL) was added a large excess (20.4 equiv) of
benzylamine (1.0 mL, 9.16 mmol). The reaction mixture was refluxed
for 3 h on an oil bath and then cooled to room temperature. After the
solvent was removed under reduced pressure, ethanol (20 mL) was
added to the obtained slurry, and the suspension was stirred for 1 h at
room temperature. Afforded precipitates were filtered, washed with
cold methanol (10 mL), dried, and then characterized as obtained.
Some compounds were also further purified.
2-(1-Benzyl-2-(4-(dimethylamino)styryl)-6-methylpyridin-4(1H)-
ylidene)-1H-indene-1,3(2H)-dione (ZE-1) was synthesized by general
method I from 2-(2-(4-(dimethylamino)styryl)-6-methyl-4H-pyran-4-
ylidene)-1H-indene-1,3(2H)-dione (2) (0.18 g, 0.470 mmol) and
about 20 equiv of benzylamine (1.0 mL, 9.16 mmol). After the required
workup, 0.09 g (40.5%) of 2-(1-benzyl-2-(4-(dimethylamino)styryl)-6-
methylpyridin-4(1H)-ylidene)-1H-indene-1,3(2H)-dione (ZE-1) as a
yellow-orange powder with an mp of 175 °C was obtained. IR (paraffin
oil) υ, cm−1: 3086, 3066, 3029, 2982, 2944, 2901, 2867, 2811, 1677,
1659, 1627, 1604, 1506, 1464. 1H NMR (CDCl3, 300 MHz): δ 9.14 (s,
1H, major conformer), 8.84 (s, 1H, minor conformer), 8.78 (s, 1H,
minor conformer), 8.71 (s, 1H, major conformer), 7.65−7.61 (m, 2H),
7.52−7.46 (m, 2H), 7.45−7.27 (m, 5H), 7.09−6.90 (m, 3H, major
conformer), 6.69−6.41 (m, 3H), 6.06−6.00 (d, 1H, J = 12.1 Hz, minor
conformer), 5.37 (s, 2H, major conformer), 5.33 (s, 2H, minor
conformer), 3.00 (s, 6H, major conformer), 2.94 (s, 6H, minor
conformer), 2.48 (s, 3H, major conformer), 2.47 (s, 3H, minor
conformer). 13C{1H} NMR (CDCl3, 300 MHz): δ 193.0, 151.3, 150.9,
149.9, 148.3, 140.4, 140.3, 131.8, 129.6, 129.1, 128.4, 125.2, 119.9,
116.5, 113.7, 111.9, 102.9, 52.78, 40.2, 21.0. Anal. Calcd for
Figure 6. PL intensity versus water fraction for the dispersions of JE-
1Tr, ME-1Tr, and EE-1Tr dyes in water/THF mixtures. In all samples,
the molar concentration of dye was kept constant.
wavelengths exceeding 500 nm when the THF fraction was 1%.
This observation indicates the formation of aggregates. Also,
absorption of the dispersions was significantly suppressed when
the water content was high. This observation can be attributed
to the uneven distribution of the aggregates caused by the pure
solubility of the compounds in water.
An increase of PL intensity at 60% water content in the case of
EE-1Tr indicates AIEE at longer distances between molecules in
comparison to ME-1Tr and JE-1Tr. At 80−99% water conten,t
the PL intensity of EE-1Tr decreases rapidly. Possible
explanations for such observations could be attributed to a
gel-like solidification at higher concentrations−a phenomenon
that was first observed by Scheibe et al.33 as well as due to the
additional aggregation quenching that starts to dominate at the
closer distance between molecules. Also, the possibility of cis−
trans isomerization shown in Scheme 2 has to be taken into
account. The emissive behavior of dipolar merocyanine dyes was
interpreted in terms of an energy barrier to a conical
intersection. Nonradiative deactivation of excitation can be
characterized by a return to the reactant minimum or cis−trans
isomerization in polar medium.34 Nevertheless, all three
investigated HAPPY dyes (JE-1Tr, ME-1Tr, and EE-1Tr)
showed AIEE behavior, which could affect the increased light
amplification efficiency in neat films.
CONCLUSIONS
■
Organic donor−acceptor dyes with a 1H-pyridine fragment as
the backbone of the molecule and π-conjugation system can be
conveniently synthesized from the relevant 4H-pyran-4-ylidene
fragment containing luminophores in a one-step reaction with
benzyl-amine and obtained in high yields. However, such
synthesis is unsuccessful if a malononitrile electron acceptor is
used. Conversion of the 4H-pyran-4-ylidene backbone into a
1H-pyridine fragment enables AIEE behavior of the dyes and
slightly increases thermal stability, glass transition temperatures,
and lasing efficiency in most cases. Thermal and photophysical
properties of the synthesized materials were mostly dependent
on incorporated electron acceptors: dyes with 1,3-dimethylpyr-
imidine-2,4,6(1H,3H,5H)-trione and 1,3-diethyl-2-thioxodihy-
dropyrimidine-4,6(1H,5H)-dione fragments showed the highest
efficiency as light amplifiers (with PLQY up to 15% and ASE
thresholds as low as 46 μJ/cm2 for neat films), while compounds
with the 1H-indene-1,3(2H)-dione group were least efficient.
Doping the dyes in the PVK matrix resulted in the increased
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Article
C32H28O2N2: C, 81.33; H, 5.97; N, 5.93. Found: C, 81.15; H, 5.99;
N, 6.02.
(1-benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methylpyridin-
4(1H)-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JE-1Tr) as an
orange amorphous powder was obtained. IR (paraffin oil) υ, cm−1:
3425, 3386, 3168, 3083, 3058, 3025, 2966, 2925, 2877, 2813, 1706,
1657, 1614, 1588, 1526, 1464. 1H NMR (CDCl3, 300 MHz): δ 9.36 (s,
1H, major conformer), 9.36 (s, 1H, major conformer), 9.13 (s, 1H,
minor conformer), 9.06 (s, 1H, minor conformer), 8.95 (s, 1H, major
conformer), 7.69−7.03 (m, 44H), 6.86−6.77 (m, 2H, minor con-
former), 6.64 (d, 1H, J = 12.4 Hz, minor conformer), 6.57 (d, 1H, J =
15.6 Hz, major conformer), 6.44 (d, 2H, J = 8.7 Hz, major conformer),
6.37 (d, 2H, J = 8.9 Hz, minor conformer), 5.43 (s, 2H, major
conformer), 5.29 (s, 2H, minor conformer), 3.57 (s, 4H), 3.26 (s, 4H),
2.53 (s, 3H, major conformer), 2.40 (s, 3H, minor conformer). 13C{1H}
NMR (CDCl3, 300 MHz): δ 165.1, 143.9, 141.3, 129.8, 129.4, 128.6,
127.8, 127.0, 125.2, 122.6, 118.0, 116.9, 112.6, 111.6, 112.6, 111.6,
104.3, 87.1, 70.0, 61.0, 51.0, 21.1. Anal. Calcd for C67H58O5N4: C,
80.54; H, 5.85; N, 5.85. Found: C, 80.29; H, 5.94; N, 5.69.
5-(1-Benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-
pyridin-4(1H)-ylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-tri-
one (ME-1Tr) was synthesized by the general method I from 5-(2-(4-
(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)-
1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (MWK-1) (0.27 g,
0.27 mmol) and benzylamine (1.0 mL, 9.16 mmol). After the required
workup and additional purification by liquid column chromatography
(silica gel, V(triethylamine)/V(ethyl acetate)/V(dichloromethane) =
1:10:40 solvent system), 0.25 g (89%) of 5-(1-benzyl-2-(4-(bis(2-
(trityloxy)ethyl)amino)styryl)-6-methylpyridin-4(1H)-ylidene)-1,3-
dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (ME-1Tr) as a yellow
amorphous powder was obtained. IR (paraffin oil) υ, cm−1: 3079, 3059,
3027, 2964, 2924, 2882, 1696, 1688, 1623, 1601, 1589, 1520, 1479,
1462, 1406. 1H NMR (CDCl3, 300 MHz): δ 9.37 (s, 1H, major
conformer), 9.17 (s, 1H, minor conformer), 9.11 (s, 1H, minor
conformer), 9.00 (s, 1H, major conformer), 7.47−7.01 (m, 42H),
6.86−6.78 (m, 1H, mixture of conformers), 6.64−6.52 (m, 2H, mixture
of conformers), 6.43 (d, 2H, J = 8.5 Hz, major conformer), 6.35 (d, 2H,
J = 8.9 Hz, minor conformer), 6.05 (d, 1H, J = 12.7 Hz, minor
conformer), 5.42 (s, 2H, major conformer), 5.27 (s, 2H, minor
conformer), 3.56 (s, 4H), 3.41 (s, 6H, major conformer), 3.36 (s, 6H,
minor conformer), 3.26 (s, 4H), 2.51 (s, 3H, major conformer), 2.39 (s,
3H, minor conformer). 13C{1H} NMR (CDCl3, 300 MHz): δ 164.4,
155.4, 152.4, 150.4, 149.2, 147.6, 143.9, 140.8, 133.5, 129.7, 129.2,
128.6, 127.8, 127.0, 121.2, 118.4, 113.1, 111.5, 89.6, 87.1, 61.1, 53.2,
51.0, 27.9, 21.2. Anal. Calcd for C69H62O5N4: C, 80.68; H, 6.08; N,
5.45. Found: C, 80.44; H, 6.15; N, 5.52.
5-(1-Benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-
pyridin-4(1H)-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6-
(1H,5H)-dione (EE-1Tr) was synthesized by general method I from 5-
(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-yli-
dene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione
(EWK-1) (0.17 g, 0.17 mmol) and benzylamine (1.0 mL, 9.16 mmol).
After the required workup and additional purification by liquid column
chromatography (silica gel, V(triethylamine)/V(ethyl acetate)/V-
(dichloromethane) = 1:10:40 solvent system), 0.09 g (85%) of 5-(1-
benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methylpyridin-
4(1H)-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-
dione (EE-1Tr) as an orange amorphous powder was obtained. IR
(paraffin oil) υ, cm−1: 3650, 3459, 3051, 3029, 3022, 2987, 2970, 2950,
2929, 2867, 1738, 1728, 1656, 1651, 1619, 1586, 1554, 1521, 1481,
1448, 1420. 1H NMR (CDCl3, 300 MHz): δ 9.31 (s, 1H, major
conformer), 9.17 (s, 1H, minor conformer), 9.11 (s, 1H, minor
conformer), 8.95 (s, 1H, major conformer), 7.47−7.01 (m, 41H),
6.85−6.76 (m, 2H, mixture of conformers), 6.64 (d, 1H, J = 12.4 Hz,
minor conformer), 6.57 (d, 1H, J = 15.7 Hz, major conformer), 6.45 (d,
2H, J = 8.8 Hz, major conformer), 6.36 (d, 2H, J = 9.0 Hz, minor
conformer), 6.06 (d, 1H, J = 12.0 Hz, minor conformer), 5.44 (s, 2H,
major conformer), 5.30 (s, 2H, minor conformer), 4.75−4.59 (m, 4H),
3.55 (m, 4H), 3.26 (m, 4H), 2.54 (s, 3H, major conformer), 2.42 (s, 3H,
minor conformer), 1.42−1.27 (m, 6H). 13C{1H} NMR (CDCl3, 300
MHz): δ 177.0, 162.1, 155.4, 150.8, 149.4, 147.9, 143.9, 141.3, 133.2,
129.8, 129.4, 128.6, 127.8, 127.0, 125.2, 119.6, 112.7, 111.6, 87.00, 61.1,
5-(1-Benzyl-2-(4-(dimethylamino)styryl)-6-methylpyridin-4(1H)-
ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JE-1) was synthesized by
general method I from 5-(2-(4-(dimethylamino)styryl)-6-methyl-4H-
pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (3) (0.16 g,
0.438 mmol) and about 20 equiv of benzylamine (1.0 mL, 9.16
mmol). After the required workup, 0.16 g (80%) of 5-(1-benzyl-2-(4-
(dimethylamino)styryl)-6-methylpyridin-4(1H)-ylidene)pyrimidine-
2,4,6(1H,3H,5H)-trione (JE-1) as a dark-yellow powder with an mp >
300 °C (dec.) was obtained. IR (paraffin oil) υ, cm−1: 3136, 3083, 2956,
2921, 2851, 2804, 1715, 1687, 1663, 1587, 1532, 1463, 1414. 1H NMR
(CDCl3, 300 MHz): δ 9.37 (s, 1H, minor conformer), 9.11 (s, 1H,
major conformer), 9.05 (s, 1H, major conformer), 8.97 (s, 1H, minor
conformer), 7.45−7.34 (m, 5H), 7.08−7.04 (d, 2H, J = 8.0 Hz, minor
conformer), 7.01−6.90 (m, 4H, major conformer), 6.75−6.70 (d, 1H, J
= 12.4 Hz, major conformer), 6.11−6.05 (d, 1H, J = 12.1 Hz, major
conformer), 5.46 (s, 2H, minor conformer), 5.43 (s, 2H, major
conformer), 3.02 (s, 6H, minor conformer), 2.99 (s, 6H, major
conformer), 2.55 (s, 3H, minor conformer), 2.54 (s, 3H, major
conformer). 13C{1H} NMR (DMSO-d6, 300 MHz): δ 165.7, 165.6,
153.9, 151.7, 150.8, 150.7, 150.3, 149.4, 139.5, 137.0, 135.8, 135.2,
130.8, 129.6, 128.2, 126.1, 123.3, 122.1, 120.0, 119.5, 116.2, 115.1,
112.3, 112.1, 87.8, 52.7, 21.6. Anal. Calcd for C27H26O4N3: C, 71.35; H,
5.77; N, 12.33. Found: C, 71.35; H, 5.77; N, 12.33.
Attempted synthesis of 1-benzyl-2-(4-(dimethylamino)styryl)-6-
methylpyridin-4(1H)-ylidene-malononitrile (DE-1) was carried out
by general method I from 2-(4-(dimethylamino)styryl)-6-methyl-4H-
pyran-4-ylidene)malononitrile (1) (0.21 g, 0.693 mmol) and about 20
equiv of benzylamine (1.0 mL, 9.16 mmol). After the required workup,
0.13 g (38%) of N-benzyl-2-(1-benzyl-2-(4-(dimethylamino)styryl)-6-
methylpyridin-4(1H)-ylidene)-2-cyanoacetimidamide (DE-1*) as a
1
yellow amorphous powder with an mp of 209 °C was obtained. H
NMR (CDCl3, 300 MHz): δ 11.19 (s, 1H), 7.57 (d, 1H, J = 15.6 Hz),
7.40 (d, 4H, J = 7.8 Hz), 7.31−7.09 (m, 10H), 6.76 (d, 1H, J = 15.7 Hz),
6.65 (d, 2H, J = 8.5 Hz), 6.23 (s, 1H), 5.83 (s, 1H), 4.90 (s, 2H), 4.81 (s,
2H), 2.93 (s, 6H), 2.19 (s, 3H). 13C{1H} NMR (CDCl3, 300 MHz): δ
157.6, 157.0, 155.2, 150.4, 143.6, 135.1, 133.2, 129.3, 128.4, 128.3,
127.8, 127.7, 126.5, 125.4, 124.1, 112.4, 105.2, 104.1, 103.5, 48.3, 45.2,
40.4, 21.3. Anal. Calcd for C33H33N5: C, 79.33; H, 6.66; N, 14.02.
Found: C, 78.98; H, 6.62; N, 13.70.
2-(1-Benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-
pyridin-4(1H)-ylidene)-1H-indene-1,3(2H)-dione (ZE-1Tr) was syn-
thesized by general method I from 2-(2-(4-(bis(2-(trityloxy)ethyl)-
amino)styryl)-6-methyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-
dione (ZWK-1)24 (0.10 g, 0.11 mmol) and benzylamine (0.5 mL, 4.08
mmol). After the required workup, 0.10 g (86.4%) of 2-(1-benzyl-2-(4-
(bis(2-(trityloxy)ethyl)amino)styryl)-6-methylpyridin-4(1H)-yli-
dene)-1H-indene-1,3(2H)-dione (ZE-1Tr) as an orange amorphous
powder was obtained. IR (paraffin oil) υ, cm−1: 3088, 3060, 3024, 2921,
2851, 1673, 1661, 1629, 1592, 1580, 1532, 1521, 1504, 1463, 1456. 1H
NMR (CDCl3, 300 MHz): δ 9.09 (s, 1H, major conformer), 8.80 (s,
1H, minor conformer), 8.74 (s, 1H, minor conformer), 8.66 (s, 1H,
major conformer), 7.62−7.55 (m, 2H), 7.46−7.41 (m, 2H), 7.39−6.99
(m, 40H), 6.81 (d, 2H, J = 7.8 Hz, major conformer), 6.56 (s, 1H, J =
12.6 Hz, minor conformer), 6.49 (s, 1H, J = 15.6 Hz, major conformer),
6.37 (d, 2H, J = 8.6 Hz, major conformer), 6.29 (d, 2H, J = 8.5 Hz), 5.91
(d, 1H, J = 12.4 Hz, minor conformer), 5.31 (s, 2H, major conformer),
5.17 (s, 2H, minor conformer), 3.56−3,41 (m, 4H), 3.26−3.14 (m,
4H), 2.43 (s, 3H, major conformer), 2.30 (s, 3H, minor conformer).
13C{1H} NMR (CDCl3, 300 MHz): δ 186.1, 183.6, 143.9, 140.4, 128.6,
127.9, 127.8, 127.0, 110.6, 102.7, 66.6, 64.3, 61.0, 60.8, 21.0. Anal.
Calcd for C72H60O4N2: C, 85.01; H, 5.95; N, 2.75. Found: C, 84.75; H,
6.09; N, 3.06.
5-(1-Benzyl-2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-
pyridin-4(1H)-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JE-1Tr)
was synthesized by general method I from 5-(2-(4-(bis(2-(trityloxy)-
ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)pyrimidine-2,4,6-
(1H,3H,5H)-trione (JWK-1)24 (0.16 g, 0.17 mmol) and benzylamine
(0.8 mL, 7.32 mmol). After the required workup, 0.17 g (96.8%) of 5-
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Article
53.5, 51.0, 43.2, 21.2, 12.8. Anal. Calcd for C71H66O4N4S: C, 79.60; H,
6.21; N, 5.23. Found: C, 79.35; H, 6.30; N, 5.36.
1456, 1448, 1428, 1456, 1448, 1428, 1401. 1H NMR (CDCl3, 300
MHz): δ 8.89 (s, 2H), 7.50−7.10 (m, 66H), 6.71 (s, 2H, J = 15.9 Hz),
6.59 (d, 4H, J = 8.6 Hz), 3.66 (m, 8H), 3.42 (s, 6H), 3.36 (m, 8H).
13C{1H} NMR (CDCl3, 300 MHz): δ 164.3, 161.6, 156.6, 151.8, 149.6,
143.9, 137.6, 129.6, 128.6, 127.9, 127.1, 114.7, 111.8, 111.2, 87.1, 61.0,
51.1, 28.0. Anal. Calcd for C111H96O8N4: C, 82.60; H, 6.00; N, 3.47.
Found: C, 82.27; H, 6.05; N, 3.60.
General Method II: Synthesis of 4H-Pyranes 8a−d.24
A
solution of 2,6-dimethyl-4H-pyran-4-one (7)24,35 (10.0 mmol) and
the corresponding active methylene group containing compound A
(10.0 mmol) in acetic anhydride (5.0 mL) was stirred for 3 h at 110−
120 °C on an oil bath and then left overnight to cool to room
temperature. The formed solids were filtered off, washed with cold
methanol (20 mL), and then dried. Obtained products were
characterized and used in the next steps of synthesis without further
purification.
5-(2-(4-(Bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-
4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione
(EWK-1) and 5-(2,6-bis(4-(bis(2-(trityloxy)ethyl)amino)styryl)-4H-
pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-
dione (EWK-2) were synthesized by general method III from 5-(2,6-
dimethyl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-
4,6(1H,5H)-dione (8d) (0.25 g, 0.81 mmol) and 4-(bis(2-(trityloxy)-
ethyl)amino)benzaldehyde (9) (0.55 g, 0.81 mmol). After separation
and purification by flash column chromatography (silica gel,
V(dichloromethane)/V(ethyl acetate) = 10:1 solvent system), 0.27 g
(34%) of 5-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-
pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-
dione (EWK-1) as a dark-red amorphous powder with an mp of 130 °C
was obtained. IR (paraffin oil) υ, cm−1: 3508, 3056, 3024, 2978, 2972,
2928, 2908, 2879, 2474, 2323, 1736, 1668, 1630, 1609, 1593, 1553,
1525, 1490, 1464, 1447, 1440, 1430, 1402. 1H NMR (CDCl3, 300
MHz): δ 8.94 (s, 1H), 8.74 (s, 1H), 7.50−7.10 (m, 33H), 6.67 (d, 1H, J
= 15.8 Hz), 6.56 (d, 2H, J = 8.5 Hz), 4.64 (q, 4H, J = 6.6 Hz), 3.63 (m,
4H), 3.34 (m, 4H), 2.54 (s, 3H), 1.36 (t, 6H, J = 6.6 Hz). 13C{1H}
NMR (CDCl3, 300 MHz): δ 162.6, 159.7, 143.9, 129.7, 128.6, 127.9,
127.3, 127.0, 124.9, 43.4, 20.8, 12.6. Anal. Calcd for C64H59O5N3S: C,
78.26; H, 6.05; N, 4.28. Found: C, 78.07; H, 6.25; N, 4.29.
After flash column chromatography, 0.40 g (30%) of 5-(2,6-bis(4-
(bis(2-(trityloxy)ethyl)amino)styryl)-4H-pyran-4-ylidene)-1,3-dieth-
yl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (EWK-2) as a dark-
violet amorphous powder with an mp of 140 °C was also obtained. IR
(paraffin oil) υ, cm−1: 3609, 3459, 3056, 3032, 3024, 2970, 2926, 2894,
2877, 2486, 2325, 1741, 1718, 1662, 1630, 1584, 1560, 1519, 1490,
1454, 1446, 1429. 1H NMR (CDCl3, 300 MHz): δ 8.91 (s, 2H), 7.50−
7.10 (m, 66H), 6.72 (d, 2H, J = 15.8 Hz), 6.62 (d, 4H, J = 8.4 Hz), 4.70
(q, 4H, J = 6.6 Hz), 3.69 (m, 8H), 3.40 (m, 8H), 1.46 (t, 6H, J = 6.6 Hz).
13C{1H} NMR (CDCl3, 300 MHz): δ 177.4, 162.0, 157.2, 149.8, 143.9,
129.8, 128.6, 127.9, 127.1, 122.7, 144.4, 112.2, 96.0, 87.2, 61.0, 51.1,
43.4, 12.7. Anal. Calcd for C113H100O7N4S: C, 81.85; H, 6.08; N, 3.38.
Found: C, 81.72; H, 6.13; N, 3.53.
2-(2,6-Dimethyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione
(8a), 5-(2,6-dimethyl-4H-pyran-4-ylidene)pyrimidine-2,4,6-
(1H,3H,5H)-trione (8b), 5-(2,6-dimethyl-4H-pyran-4-ylidene)-1,3-
dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (8c), and 5-(2,6-dimeth-
yl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6-
(1H,5H)-dione (8d) were synthesized by general method II, according
to known literature sources.23,35−40
General Method III: Synthesis of Triphenyl Groups Contain-
ing 4H-Pyran-4-ylidene (WK-1 and WK-2) Dyes.24 To a solution of
the corresponding (2,6-dimethyl-4H-pyran-4-ylidene derivative (8a,
8b, 8c, or 8d) (1.00 mmol) and 4-(bis(2-(trityloxy)ethyl)amino)-
benzaldehyde (9) (1.00 mmol) in dry pyridine (5.0 mL) 3 drops of
piperidine were added. The reaction mixture was stirred for 8 h at 90−
100 °C on an oil bath, then cooled to room temperature. The obtained
brownish slurry was poured into 100 mL of ethyl alcohol, and the
afforded precipitates were filtered, washed with 10 mL of cold
methanol, and dried. The obtained mono- (ZWK-1, JWK-1, MWK-1,
and MWK-1 = abbreviated as WK-1 dyes) and bis- (ZWK-2, JWK-2,
MWK-2, and EWK-2 = abbreviated as WK-2 dyes) condensation
products were separated by a flash column chromatography.
2-(2-(4-(Bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-
4-ylidene)-1H-indene-1,3(2H)-dione (ZWK-1) and 2-(2-(4-(bis(2-
(trityloxy)ethyl)amino)styryl)-6-(4-(1,5-bis(trityloxy)pentan-3-yl)-
styryl)-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK-2) as
well as 5-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-
pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JWK-1) and 5-
(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-(4-(1,5-bis(trityloxy)-
pentan-3-yl)styryl)-4H-pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-
trione (JWK-2) were synthesized by general method III, according to
the literature.24
5-(2-(4-(Bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-
4-ylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (MWK-
1) and 5-(2,6-bis(4-(bis(2-(trityloxy)ethyl)amino)styryl)-4H-pyran-
4-ylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (MWK-
2) were synthesized by general method III from 5-(2,6-dimethyl-4H-
pyran-4-ylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione
(8c) (0.25 g, 0.94 mmol) and 4-(bis(2-(trityloxy)ethyl)amino)-
benzaldehyde (9) (0.63 g, 0.94 mmol). After separation and
purification by flash column chromatography (silica gel, V-
(dichloromethane)/V(ethyl acetate) = 12:1 solvent system), 0.30 g
(34%) of 5-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-
pyran-4-ylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione
(MWK-1) as an orange amorphous powder with an mp of 149 °C was
obtained. IR (paraffin oil) υ, cm−1: 3458, 3080, 3056, 3023, 2990, 2970,
2953, 2928, 2881, 2475, 2337, 1737, 1705, 1649, 1637, 1631, 1598,
1529, 1472, 1448, 1429, 1408. 1H NMR (CDCl3, 300 MHz): δ 8.89 (s,
1H), 8.70 (s, 1H), 7.45−7.10 (m, 33H), 6.61 (d, 1H, J = 15.9 Hz), 6.51
(d, 2H, J = 8.7 Hz), 3.58 (t, 4H, J = 5.4 Hz), 3.36 (s, 6H), 3.30 (t, 4H, J =
5.3 Hz), 2.47 (m, 3H). 13C{1H} NMR (CDCl3, 300 MHz): δ 163.4,
163.1, 157.1, 151.7, 149.7, 143.9, 138.2, 129.7, 128.6, 127.8, 127.1,
122.5, 114.0, 111.8, 110.9, 110.5, 87.1, 61.0, 51.1, 28.1, 20.7. Anal.
Calcd for C62H55O6N3: C, 79.38; H, 5.91; N, 4.48. Found: C, 79.15; H,
6.14; N, 4.48.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.0c02574.
Structure characterization data of reactants and inves-
tigated substances; detailed thermal, optical, and photo-
physical characterization experimental details (PDF)
FAIR data, including the primary NMR FID files, for
compounds ZE-1, JE-1, DE-1*, MWK-1, MWK-2, EWK-
1, EWK-2, ZE-1Tr, JE-1Tr, ME-1Tr, and EE-1Tr (ZIP)
AUTHOR INFORMATION
■
Corresponding Author
Elmars Zarins − Institute of Applied Chemistry, Riga Technical
University, Riga LV-1048, Latvia; Institute of Solid State
Physics, University of Latvia, Riga LV-1063, Latvia;
orcid.org/0000-0002-5103-7511;
After flash column chromatography, 0.39 g (27%) of 5-(2,6-bis(4-
(bis(2-(trityloxy)ethyl)amino)styryl)-4H-pyran-4-ylidene)-1,3-dime-
thylpyrimidine-2,4,6(1H,3H,5H)-trione (MWK-2) as a dark-violet
amorphous powder with an mp of 142 °C was also obtained. IR
(paraffin oil) υ, cm−1: 3628, 3493, 3056, 3036, 3025, 2970, 2951, 2941,
2919, 2865, 2343, 1737, 1703, 1643, 1630, 1591, 1555, 1520, 1491,
Email: Elmars.Zarins@rtu.lv
Authors
Julija Pervenecka − Institute of Solid State Physics, University of
Latvia, Riga LV-1063, Latvia
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Article
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Oleksandr Bezvikonnyi − Department of Polymer Chemistry
and Technology, Kaunas University of Technology, Kaunas
51423, Lithuania
Aivars Vembris − Institute of Solid State Physics, University of
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Dmytro Volyniuk − Department of Polymer Chemistry and
Technology, Kaunas University of Technology, Kaunas 51423,
Lithuania; orcid.org/0000-0003-3526-2679
Juozas V. Grazulevicius − Department of Polymer Chemistry
and Technology, Kaunas University of Technology, Kaunas
51423, Lithuania; orcid.org/0000-0002-4408-9727
Valdis Kokars − Institute of Applied Chemistry, Riga Technical
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Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript. E.Z. and J.P. contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work has been supported by the European Regional
Development Fund within the Activity 1.1.1.2 “Post-doctoral
Research Aid” of the Specific Aid Objective 1.1.1 “To increase
the research and innovative capacity of scientific institutions of
Latvia and the ability to attract external financing, investing in
human resources and infrastructure” of the Operational
Program “Growth and Employment” (1.1.1.2/VIAA/1/16/
035). This work was also partially supported by European
Union’s Horizon 2020 Research and Innovation Programme
under the Marie Skłodowska-Curie grant agreement no. 823720.
The Institute of Solid State Physics at the University of Latvia as
the Center of Excellence has received funding from the
European Union’s Horizon 2020 Framework Program H2020-
WIDESPREAD-01-2016-2017-TeamingPhase2 under grant
agreement no. 739508, project CAMART2. We express our
gratitude to Kristine Lazdovica for thermal decomposition
temperature measurements and IR property determination,
Zane Abelniece and Rolands Capars for conducting the
elemental analysis, Vitalijs Rjabovs for assistance with NOESY
spectra acquisition, and Lauma Laipniece for HPLC and MS
analysis.
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