Molecular Engineering for the Development of a Discotic Nematic Mesophase and Solid-State Emitter in Deep-Blue OLEDs

Article abstract of DOI:10.1021/acs.joc.1c00742

A unique strategy for the attainment of a discotic nematic (ND) mesophase is reported consisting of a central benzene core to which are attached two 4-alkylphenyl and two 4-pentylbiphenyl moieties diagonally via alkynyl linkers. The rotational nature and

Full text of DOI:10.1021/acs.joc.1c00742

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Article
Molecular Engineering for the Development of a Discotic Nematic
Mesophase and Solid-State Emitter in Deep-Blue OLEDs
Joydip De, Rohit Ashok Kumar Yadav, Rahul Singh Yadav, Santosh Prasad Gupta, Mayank Joshi,
Angshuman Roy Choudhury, Jayachandran Jayakumar, Jwo-Huei Jou, Chien-Hong Cheng,
and Santanu Kumar Pal*
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ABSTRACT: A unique strategy for the attainment of a discotic
nematic (ND) mesophase is reported consisting of a central benzene
core to which are attached two 4-alkylphenyl and two 4-
pentylbiphenyl moieties diagonally via alkynyl linkers. The rotational
nature and incompatibility of unequal phenylethynyl units led to the
disruption of π−π interactions within cores that aids to the
realization of ND phase and favors high solid-state emission. When
used in OLEDs, compounds act as an efficient solid-state pure deep-blue emitter with Commission Internationale de L’Eclairage
(CIEx,y) coordinates of (0.16, 0.07).
INTRODUCTION
■
Molecular shape is the most important factor that controls the
self-organization of the molecules into liquid crystalline (LC)
phases. For instance, π-conjugated flat aromatic cores lead to
the formation of columnar phases in discotic LCs due to strong
core−core interactions.1 However, the realization of nematic
phases formed by discotic molecules (so-called discotic
nematic (ND) phases) requires flexibility in the molecular
structure to disrupt the intercore interactions. In this direction,
limited examples are reported in the literature which include
triphenylene, naphthalene, truxene, perylene, anthraquinone,
and hexa- or penta-alkynylbenzene based systems.2 Differing
from these, herein, we have developed a unique strategy to
achieve discotic nematogens by utilizing X-shaped molecules
(Figure 1). Such a molecular structure was synthesized
previously; however, they failed to show mesomorphism. For
example, Ehlers et al. synthesized a molecule with central
benzene core connected to four 4-pentylphenyl as rigid arms
via alkynyl linkers, which appears as a red-brown liquid.3
Interestingly, the use of four 4-pentylbiphenyl as flexible side
linkers to the same core forms a pale yellow solid crystal as
reported by Sekine and co-workers.4 Motivated by these prior
reports, we sought to observe any mesomorphism using the
combination of 4-alkylphenyl and 4-pentylbiphenyl moieties
through alkynyl linkers to the benzene core (Figure 1).
Interestingly, using the present strategy, we observed the
formation of ND mesophases. We believe that the incompat-
ibility of the two unequal side arms to the core is likely
responsible for improper packing to the realization of the ND
mesophase.
Figure 1. Comparison of the present molecular design and state of the
material along with its earlier reports.3,4
light-emitting materials which are hugely scarce in the area of
organic light-emitting diodes (OLEDs). OLEDs have recently
gained an immense level of attention due to their widespread
application, from small portable devices to flat-panel full-color
displays and solid-state lighting sources.6 To date, pure deep-
blue OLEDs are very rare in comparison to their red and green
complements.7 In general, most commercial OLEDs rely on
vacuum-sublimed devices rather than solution-processed ones.
Received: March 30, 2021
Published: May 6, 2021
Another important feature of such types of multiynes is that
they emit in the blue region.5 Hence, they can also act as blue-
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a
Scheme 1. Synthesis of Derivatives of 1
a
Reagents and conditions: (i) 3,4-Dihydro-2H-pyran (DHP), pyridinium p-toluenesulfonate (PPTS), r.t., 12 h. (ii) Pd(PPh3)4, CuI, PPh3, dry
Et3N/dry piperidine (2.8:1), 90 °C, 18 h. (iii) p-Toluenesulfonic acid (p-TsOH), dichloromethane/methanol (2.3:1), r.t., 12 h. (iv)
Trifluoromethanesulfonic anhydride (Tf2O), piperidine, dichloromethane, r.t., 12 h. (v) Pd(PPh3)2Cl2, CuI, PPh3, Et3N (dry), 90 °C, 18 h. Yield of
1: 68−70%.
While the performance of vacuum-sublimed OLEDs is
unrivalled at present, the process is both costly and material-
wasteful.8 In addition, it is also expensive to fabricate large-area
pixels given the size of the evaporator.9 However, the solution-
processed fabrication of OLEDs such as using ink-jet printing
technology could address the underlying limitations of the
vacuum-sublimation technique.10 In this context, using LC
molecules consisting of peripheral alkyl chains not only makes
them easily solution-processable but also allows for fine-tuning
of their central chromophoric part which could serve as a
source of pure deep-blue light emission in OLEDs. In this
direction, we have synthesized ND compounds 1.1 and 1.2 and
used them as a solid-state emitter material in solution-
processable OLEDs. Interestingly, 1.1 showed excellent
performance with a maximum external quantum efficiency
(EQEmax) of 4.0%, and high-quality pure deep-blue emission
with CIEx,y coordinates of (0.16, 0.07), matching closely with
the National Television System Committee (NTSC) and
High-Definition Television (HDTV) standards.11
asymmetric unit. Although a −C5H11 chain is attached to the
aromatic terminals (C15 and C28) of the molecule, these
chains have different conformations (Table S2). There are two
sets of molecules in the unit cell: One set is marked as red (all
the atoms are red), and other set is marked as blue (all the
atoms are blue) (Figure 2b). These two sets of molecules are
oriented differently in the lattice. The molecules in the red set
are parallel to each other and the molecules in the blue set are
parallel to each other. The interplanar distance is 7.39 Å in
both the set of molecules. The planes are drawn through the
central aromatic ring of the red set of molecules and the blue
set of molecules (Figure 2c). This figure clearly indicates that
the red molecules are parallel to one another and that blue
molecules are parallel to one another and the planes through
the set of blue molecules and the planes through the set of red
molecules intersect at an angle of 64.5°. The same is shown as
a scheme in the Figure 2d. This arrangement of molecules
further favors to attain the LC state at high temperature (vide
infra).
The thermal behavior of 1.1 and 1.2 was characterized by
thermogravimetric analysis (TGA), differential scanning
calorimetry (DSC) and polarizing optical microscopy
(POM). Both the compounds (1.1 and 1.2) exhibited good
thermal stability as seen from Figure S33. In DSC (Figure
S34a, Table S3), compound 1.1 showed two transitions on
heating: One at 179.1 °C (ΔH = 33.0 kJ/mol) corresponds to
the crystal to mesophase, and another at 187.2 °C (ΔH = 1.2
kJ/mol) relates to mesophase to isotropic transition. On
cooling, it also exhibited two transitions. Under POM, 1.1
shows schlieren texture (Figure 3a) upon cooling form
isotropic, indicating its nematic LC character of the
mesophase.5a,12 Compound 1.2 exhibited phase transitions
similar to those observed for 1.1 (Figures S34b and S35, Table
S3).
RESULTS AND DISCUSSION
■
The synthetic route of compounds 1.1 and 1.2 is provided in
Scheme 1. Detailed synthesis and structural characterization of
1.1−1.2 are outlined in the Experimental Section and the
Figures S1−S31. Compound 1.1 was found to produce bright
yellow colored crystals when crystallized from hexane solvent
at room temperature. The structure of this compound was
solved and refined using single-crystal X-ray diffraction data at
100 K in monoclinic unit cell (a = 29.617(2) Å, b = 5.9768(4)
Å, c = 33.630(3) Å, β = 115.121(10)°, V = 5390.0(8) Å3), C2/
c space group with Z = 4 (Z′ = 0.5) (CCDC 2047919, Table
S1). The inversion center of the molecule (Figures 2a and
S32) was found to coincide with the crystallographic center of
inversion; hence, half of the molecule was found in the
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Figure 2. (a) ORTEP of the molecule with 50% probability ellipsoid; asymmetric unit (gray) is shown with the atom numbering scheme and the
symmetry generated part of the molecule 1.1 is shown in yellow (H atoms are excluded for clarity). (b) Packing diagram of the molecule 1.1
viewed down the b-axis. (c) Parallel planes drawn through the red molecules and through the blue molecules of 1.1 are shown here in the packing
diagram viewed down the c-axis. (d) Schematic representation of arrangement of the molecules of 1.1.
Figure 3. (a) POM micrograph of 1.1 at 135.8 °C upon cooling from isotropic liquid (crossed polarizer X 200). (b) XRD pattern of 1.1 at 150 °C
(upon cooling) along with the d-spacing in the small and wide-angle regime. (c) Schematic representation of the discotic nematic phase of 1.1
where the compound is modeled as the disc.
Furthermore, the quantitative study of compounds 1.1 and
1.2 in the nematic phase is detailed by small- and wide-angle
X-ray scattering (SAXS/WAXS) experiments as summarized
below. The X-ray diffraction (XRD) pattern of 1.1 (Figure 3b)
shows one narrow and one broad peak in the small- and wide-
angle regions, respectively. The observed d-spacing of the
small-angle peak is 24.52 Å which appears due to the average
interdisc distance parallel to the disc plane and corresponds to
the approximated diameter of the discotic unit. Moreover, the
observed d-spacing of the wide-angle peak is 5.17 Å which
mainly originated from the liquidlike correlation of the molten
chains. Thus, the mesophase of 1.1 is ND in nature. The
correlation length for the small-angle peak (with a d-spacing of
24.52 Å) is 26.38 Å, which corresponds to about one
correlated disc unit along disc plane, whereas for the wide-
angle peak (with a d-spacing of 5.17 Å) the correlation length
is 8.64 Å, which reflects about two correlated alkyl chains. This
is very much suitable for the nematic phase. The XRD pattern
corresponds to the nematic phase of the 1.2 is very similar to
that of 1.1 and analyzed in a similar way (Figure S36). The
compound 1.1 can be modeled as disc which leads to forming
discotic nematic phase (Figure 3c).
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The photophysical characteristics of 1.1 and 1.2 were
studied by UV−vis and fluorescence spectroscopy (Figure S37
and S38 and Table S4). Both the compounds exhibited blue
emission in solution as well as in the solid state. Furthermore,
to study the impact of solvent polarity on the photophysical
behavior of 1.1 and 1.2, we have performed absorption and
emission spectroscopy in various solvents. From Figures S39
and S40, we observed that both the compounds (1.1 and 1.2)
showed very negligible change in absorption spectra, whereas
they showed a weak positive solvatochromism effect in the
emission spectra (Table S5). This can be attributed to the
symmetrical molecular structures of 1.1 and 1.2, which are also
evidenced from the single-crystal X-ray diffraction data analysis
(vide supra).
Compound 1.1 and 1.2 exhibited HOMO/LUMO at
−5.51/−3.45 eV and −5.48/−3.44 eV, respectively, as
determined from their electrochemical characteristics, meas-
ured by cyclic voltammetry (Figure S41 and Table S6).
Furthermore, to visualize the electronic distribution of frontier
molecular orbitals of 1.1 and 1.2, density functional theory
(DFT) calculation was performed. It revealed that both
HOMO and LUMO are spatially distributed at the alternate
positions of the molecules (1.1 and 1.2), having contributions
from the central as well as peripheral aromatic rings (Figure
S42).
Table 1. Electroluminescence Properties of Solution-
Processed OLED Devices Based on Emitters 1.1 and 1.2
Doped with CBP Host at 1.0 wt %
turn-on
voltage
PEmax/CEmax/EQE
CIE
Lmax
a
mabx
c
emitter
(V)
(lm W−1/cd A−1/%)
1.5/2.1/4.0
coordinates
(cd/m2)
1.1
1.2
3.2
3.1
(0.16, 0.07)
(0.16, 0.07)
1098
1202
1.4/1.6/2.9
a
b
Voltage (luminance >1 cd m−2). Maximum power efficiency
(PEmax), current efficiency (CEmax), luminance (Lmax), and external
c
quantum efficiency (EQEmax). CIE coordinates at 100 cd m−2.
was measured by atomic force microscopy (AFM) in tapping
mode. From AFM, the root means square (RMS) roughness of
CBP:1.1 and CBP:1.2 film was recorded as 0.6 and 0.9 nm,
respectively, indicating good miscibility (homogeneity phase)
between emitters and the CBP host.13 The representative AFM
image of CBP:1.1 film is shown in Figure S43.
The normalized EL spectra, current density−voltage−
luminance (J−V−L), current efficiency−luminance−power
efficiency (CE−L−PE) characteristics of the 1.1 and 1.2
based OLED devices are shown in Figure 4b−d, and
performances are summarized in Tables 1 and S7 and Figures
S44 and S45. Figure 4b displays the EL spectra of the 1.1- and
1.2-based OLEDs. The deep-blue emissive devices display the
EL peak at 420 nm which is consistent with their optical band
gap energies and manifest closely with the PL spectra of the
film.
Noticeably, both devices present low turn-on voltage
(luminance > 1 cd/m2) in the range of 3.1−3.2 V which can
be rationalized by well-matched energy levels of the
compounds with the host and leads to favorable charge
injection, migration, and recombination. The presented CIE
results of the devices are much close to the CIE coordinates of
(0.14, 0.08) enjoined by the NTSC and HDTV standards.11
The 1.1-based device demonstrated excellent performance
with a maximum external quantum efficiency (EQEmax) of
4.0%, a maximum luminance (Lmax) of 1098 cd/m2, and
particularly high-quality pure deep-blue emission with CIE
coordinates of (0.16, 0.07). The EQE can still remain at 3.1%,
even at a brightness of 100 cd/m2 (Figure S46). In contrast,
the 1.2 device shows an EQEmax of 2.9%, a Lmax of 1202 cd/m2,
and a maximum current efficiency (CEmax) of 1.6 cd/A. The
photoluminescence quantum yield (PLQY, ΦPL) of 1.1 and
1.2 in doped films were 85.11 and 79.31%, respectively,
recorded using an integrating sphere under a N2 atmosphere,
consistent with the aforementioned results. In particular, it is
also noteworthy that the triplet energy (ET) of the compounds
is smaller than that of CBP host, which favorably enables
effective host−guest energy/exciton transfer and hence a better
device performance. The recorded ET of compounds 1.1 and
1.2 are 2.38 and 2.28 eV, respectively. The better OLED
performance of 1.1 is consistent with the small energy transfer
barrier (0.17 eV) with CBP (2.55 eV) that ensures efficient
harvesting of excitons with favorable charge balance and energy
transfer in the devices.14
Encouraged by the excellent thermostability and photo-
physical properties of compounds 1.1 and 1.2, the electro-
luminescence (EL) properties were assessed in multilayer
solution-processed OLEDs with the configuration of ITO/
PEDOT:PSS (40 nm)/CBP: x wt % 1.1 or 1.2 (x = 0.5, 1.0,
3.0, and 5.0) (20 nm)/TPBi (35 nm)/LiF (1 nm)/Al (150
nm). The energy level alignment diagram of the studied
devices is displayed in Figure 4a, and the performances are
Figure 4. (a) Schematic energy-level diagram. (b) Normalized EL
spectra (inset shows blue emission and CIE plot). (c) Current
density−voltage−luminance (J−V−L) and (d) current efficiency−
luminance−power efficiency (CE−L−PE) performance plots of 1.1-
and 1.2-based OLED devices (doped with CBP host at 1.0 wt %).
To have further insight into the energy transfer process,
transient photoluminescence (PL) decay characteristics were
studied, as shown in Figure S47. The fluorescence lifetimes of
the CBP:1.1 (1.0 wt %) and CBP:1.2 (1.0 wt %) systems
exhibit a single exponential decay with a lifetime of 2.22 and
2.18 ns, respectively. Understanding the potential for efficient
exciton generation, we measured the theoretical exciton
summarized in Tables 1 and S7. The presence of long side
chains in compounds 1.1 and 1.2 renders their better solubility
in organic solvents and allows the OLED devices to be
solution-processable along with the good miscibility within the
CBP host matrix to form a homogeneous emissive layer. The
topography image of CBP:1.1 and CBP:1.2 films (at 1.0 wt %)
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31.0, 30.4, 25.4, 22.6, 18.4(6), 18.4(4), 14.1. HRMS (ESI) m/z: (M +
H)+ calcd for C42H51O4 619.3787. Found 619.3793.
utilization efficiency (EUE), which was calculated by employ-
ing the equation; EQE = γ·ηout·ΦPL·EUE,15 where γ is the
charge balance factor (in the case of perfect charge balance, γ =
1) and ηout is the out-coupling efficiency (0.2−0.3). A high
EUE of 23.5% is achieved in the case of 1.1, indicating a high
degree of exciton participation in the radiative transition
process. On the other hand, 1.2 exhibited a comparatively low
EUE of 19.5%, which is in agreement with the OLED
performance.
Compound 4.2. Compound 4.2 was synthesized by following same
procedure as used in synthesizing 4.1. It was purified by column
chromatography (silica gel, hexane/ethyl acetate) to give the product
1
as yellow solid in 73% yield (1.84 g) from 1.7 g of 5. H NMR (400
MHz, CDCl3): δ 7.43 (d, J = 7.96 Hz, 4H), 7.25 (s, 2H), 7.16 (d, J =
8.00 Hz, 4H), 5.51 (b, 2H), 4.07−4.01 (m, 2H), 3.66−3.63 (m, 2H),
2.61 (t, J = 7.70 Hz, 4H), 2.17−2.09 (m, 2H), 2.05−1.97 (m, 2H),
1.93−1.85 (m, 2H), 1.77−1.68 (m, 4H), 1.64−1.59 (m, 6H), 1.35−
1.28 (m, 12H), 0.88 (t, J = 6.56 Hz, 6H). 13C{1H} NMR (100 MHz,
CDCl3): δ 152.1(8), 152.1(2), 143.5, 131.5, 128.6, 120.7, 120.5,
120.4, 115.5, 115.4, 97.4, 97.2, 95.0, 85.4(5), 85.4(3), 61.8, 36.0, 31.8,
31.3, 30.4, 29.0, 25.4, 22.7, 18.4(7), 18.4(5), 14.2. HRMS (ESI) m/z:
(M + H)+ calcd for C44H55O4 647.4100. Found 647.4083.
Compound 3.1. In the presence of p-toluenesulfonic acid (281.53
mg, 1.48 mmol), compound 4.1 (915.88 mg, 1.84 mmol) was stirred
in DCM/methanol (50:22 mL) for 18 h. Then the reaction mixture
was diluted with distilled water and extracted with DCM. The
extracted organic layer was dried over anhydrous sodium sulfate. The
extracted organic layer was concentrated in rotary evaporator and
then was purified by column chromatography (silica gel, hexane/ethyl
acetate) to get the product as yellow-brown solid in 90% yield (600
mg). 1H NMR (400 MHz, CDCl3): δ 7.45 (d, J = 7.76 Hz, 4H), 7.19
(d, J = 7.80 Hz, 4H), 7.01 (s, 2H), 5.50 (s, 2H), 2.63 (t, J = 7.70 Hz,
4H), 1.66−1.60 (m, 4H), 1.37−1.30 (m, 8H), 0.89 (t, J = 6.56 Hz,
6H). 13C{1H} NMR (100 MHz, CDCl3): δ 150.0, 144.5, 131.7,
128.8, 119.2, 116.6, 111.6, 98.1, 82.4, 36.0, 31.5, 31.0, 22.6, 14.1.
HRMS (ESI) m/z: (M + H)+ calcd for C32H35O2 451.2637. Found
451.2640.
CONCLUSION
■
In conclusion, we have developed a unique strategy for the
synthesis of a discotic nematic liquid crystal. The discotic
molecules exhibited blue emission in solution as well as in the
solid state. Upon application in solution-processable OLEDs as
an emitter, compound 1.1 showed pure deep-blue emission
with a maximum EQE of 4.0% and CIE coordinate of (0.16,
0.07) which is very close to NTSC and HDTV standards. The
present study opens a platform to the development of new
discotic nematic materials for their utility in optoelectronic
devices.
EXPERIMENTAL SECTION
■
Measurements and Characterization. The instrumental details
for structural characterization (NMR, HRMS, and FT-IR), thermal
characterization (polarized optical microscopy (POM), thermogravi-
metric analysis (TGA), differential scanning calorimetry (DSC), X-ray
diffraction (XRD)), photophysical studies (UV−vis and fluores-
cence), electrochemical (cyclic voltammetry), and electrolumines-
cence (OLEDs) characterization are similar to those mentioned in
our previous papers.13
Compound 3.2. Compound 3.2 was synthesized by following same
procedure as that used in synthesizing 3.1. It was purified by column
chromatography (silica gel, hexane/ethyl acetate) to give the product
1
as yellow-brown solid in 86% yield (636.36 mg) from 1 g of 4.2. H
NMR (400 MHz, CDCl3): δ 7.45 (d, J = 8.16 Hz, 4H), 7.19 (d, J =
8.16 Hz, 4H), 7.01 (s, 2H), 5.49 (s, 2H), 2.63 (t, J = 7.70 Hz, 4H),
1.65−1.60 (m, 4H), 1.35−1.31 (m, 12H), 0.89 (t, J = 6.78 Hz, 6H).
13C{1H} NMR (100 MHz, CDCl3): δ 150.0, 144.5, 131.7, 128.8,
119.2, 116.7, 111.6, 98.1, 82.4, 36.1, 31.8, 31.3, 29.0, 22.7, 14.2.
HRMS (ESI) m/z: (M + H)+ calcd for C34H39O2 479.2950. Found
479.2935.
Synthesis Details. Compound 5. In a 10 mL single-necked
round-bottomed flask (RBF), 2,5-dibromobenzene-1,4-diol (2 g, 7.46
mmol) and 3,4-dihydro-2H-pyran (2.68 mL, 29.37 mmol) were mixed
and stirred for 12 h in the presence of pyridinium p-toluenesulfonate
(13.40 mg, 0.05 mmol). After that, the reaction mixture was extracted
with dichloromethane (DCM) from a mixture of DCM/water. Then,
the extracted organic layer was dried over anhydrous sodium sulfate.
After concentrating, it was purified by column chromatography (silica
gel, hexane/ethyl acetate) to give the product as a beige amorphous
Compound 2.1. Compound 3.1 (400 mg, 0.89 mmol) was added
to dry DCM (40 mL) and degassed for 15 min. Pyridine (0.32 mL,
3.99 mmol) was then added, and the solution was cooled to 0 °C. To
the cooled solution was added dropwise trifluoromethanesulfonic
anhydride (0.50 mL, 2.66 mmol), and the mixture was warmed to
room temperature and kept for 24 h. The mixture was quenched with
10% aqueous HCl. The reaction mixture was then diluted with
distilled water and extracted with DCM. The combined DCM extracts
were washed with water and dried over anhydrous sodium sulfate.
After concentrating, the product was purified by column chromatog-
raphy (neutral alumina, hexane/ethyl acetate) to give the product as
1
solid in 92% yield (2.98 g). H NMR (400 MHz, CDCl3): δ 7.35 (s,
2H), 5.37 (b, 2H), 3.89 (t, J = 10.84 Hz, 2H), 3.64−3.61 (m, 2H),
2.07−1.82 (m, 6H), 1.75−1.60 (m, 6H). 13C{1H} NMR (100 MHz,
CDCl3): δ 148.7, 121.3, 112.2, 97.6, 61.9, 30.2, 25.2, 18.3. HRMS
(ESI) m/z: (M + Na)+ calcd for C16H20Br2NaO4 458.9606. Found
458.9595.
Compound 4.1. In a 100 mL two-necked RBF, compound 5 (1.70
g, 3.89 mmol) was dissolved in dry Et3N/piperidine (40/15 mL)
under N2 atmosphere. To this solution were added Pd(PPh3)4 (73.95
mg, 0.064 mmol), CuI (27.48 mg, 0.144 mmol), and PPh3 (36.73 mg,
0.140 mmol) at room temperature. Then 1-ethynyl-4-pentylbenzene
(1.72 g, 10 mmol) was added dropwise under a N2 atmosphere. The
mixture was refluxed at 90 °C (oil bath) for 18 h with stirring under
nitrogen atmosphere. The reaction mixture was then cooled,
quenched with 5 M aqueous HCl, diluted with distilled water, and
extracted with DCM. The combined DCM extracts were washed with
water and dried over anhydrous sodium sulfate. The reaction mixture
was dried in rotary evaporator and then was purified by column
chromatography (silica gel, hexane/ethyl acetate) to give the product
as a dark-yellow semisolid in 75% yield (1.82 g). 1H NMR (400 MHz,
CDCl3): δ 7.43 (d, J = 7.92 Hz, 4H), 7.25 (s, 2H), 7.16 (d, J = 8.00
Hz, 4H), 5.51 (b, 2H), 4.07−4.01 (m, 2H), 3.66−3.63 (m, 2H), 2.61
(t, J = 7.72 Hz, 4H), 2.15−2.08 (m, 2H), 2.03−1.99 (m, 2H), 1.93−
1.86 (m, 2H), 1.74−1.68 (m, 4H), 1.65−1.60 (m, 6H), 1.36−1.30
(m, 8H), 0.89 (t, J = 6.66 Hz, 6H). 13C{1H} NMR (100 MHz,
CDCl3): δ 152.1(8), 152.1(1), 143.5, 131.5, 128.6, 120.7, 120.5,
120.4, 115.5, 115.4, 97.4, 97.2, 95.0, 85.4(4), 85.4(3), 61.7, 36.0, 31.5,
1
bright yellow solid in 82% yield (520.24 mg). H NMR (400 MHz,
CDCl3): δ 7.52−7.50 (m, 6H), 7.21 (t, J = 7.92 Hz, 4H), 2.63 (t, J =
7.72 Hz, 4H), 1.66−1.59 (m, 4H), 1.37−1.28 (m, 8H), 0.90 (t, J =
6.62 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3): δ 148.1, 145.4,
132.0, 128.8, 126.1, 120.3, 119.9, 118.5, 117.1, 100.7, 80.9, 36.1, 31.5,
31.0, 22.6, 14.1. 19F NMR (376.4 MHz, CDCl3): δ −73.30. IR (Neat
film, KBr): νmax/cm−1 2958.6, 2924.3, 2873.3, 2857.0, 2222.3, 1521.0,
1489.0, 1428.7, 1401.4, 1244.6, 1215.6, 1209.3, 1139.0, 1122.7, 907.5,
850.0, 794.3, 733.5, 666.3, 604.7, 514.6, 465.2. HRMS (ESI) m/z: (M
+ H)+ calcd for C34H33F6O6S2 715.1623. Found: 715.1613.
Compound 2.2. Compound 2.2 was synthesized by following same
procedure that as used in synthesizing 2.1. It was purified by column
chromatography (silica gel, hexane/ethyl acetate) to give the product
as bright yellow solid in 86% yield (467.08 mg) from 350 mg of 3.2.
1H NMR (400 MHz, CDCl3): δ 7.52−7.50 (m, 6H), 7.21 (t, J = 8.12
Hz, 4H), 2.63 (t, J = 7.70 Hz, 4H), 1.65−1.55 (m, 4H), 1.37−1.25
(m, 12H), 0.89 (t, J = 6.64 Hz, 6H). 13C{1H} NMR (100 MHz,
CDCl3): δ 148.1, 145.5, 132.0, 128.8, 126.1, 120.3, 119.8, 118.5,
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Article
117.1, 100.7, 80.9, 36.1, 31.8, 31.2, 29.0, 22.7, 14.2. 19F NMR (376.4
MHz, CDCl3): δ −73.29. IR (Neat film, KBr): νmax/cm−1 2959.6,
2927.4, 2873.0, 2856.2, 2223.0, 1521.4, 1489.4, 1427.7, 1402.3,
1244.4, 1214.7, 1208.0, 1139.7, 1123.4, 910.0, 850.8, 826.1, 729.4,
666.5, 604.2, 514.5, 465.6. HRMS (ESI) m/z: (M + H)+ calcd for
C36H37F6O6S2 743.1936. Found 743.1923.
AUTHOR INFORMATION
Corresponding Author
■
Santanu Kumar Pal − Department of Chemical Sciences,
Indian Institute of Science Education and Research (IISER)
Mohali, Knowledge City, Manauli 140306, India;
orcid.org/0000-0003-4101-4970; Email: skpal@
iisermohali.ac.in, santanupal.20@gmail.com
Compound 1.1. In a 100 mL two-necked RBF was added dry
triethylamine (50 mL), and the flask was purged with N2 gas for 20
min. Then, Pd(PPh3)2Cl2 (147.40 mg, 0.21 mmol), CuI (20 mg,
0.105 mmol), PPh3 (27.61 mg, 0.105 mmol), compound 2.1 (350 mg,
0.49 mmol), and 4-ethynyl-4′-pentyl-1,1′-biphenyl16 (486.78 mg, 1.96
mmol) were added sequentially in the solvent-filled RBF, and the flask
was purged with N2 gas for 20 min. The reaction mixture was refluxed
at 90 °C (oil bath) for 36 h. After cooling the reaction mixture to
room temperature, the solvent was removed by rotary evaporation.
Then, organic layer was extracted by performing the dichloromethane
(DCM)/water extraction. The DCM extracts were dried over
anhydrous sodium sulfate. After concentrating, the target material
(1.1) was purified by using column chromatography (neutral alumina,
hexane) to get the product as yellow solid in 70% yield (312.38 mg).
1H NMR (600 MHz, CDCl3): δ 7.77 (s, 2H), 7.62 (dd, J = 24.33 Hz,
8.31 Hz, 8H), 7.53 (dd, J = 19.56 Hz, 8.04 Hz, 8H), 7.27 (d, J = 8.04
Hz, 4H), 7.18 (d, J = 8.04 Hz, 4H), 2.67−2.62 (m, 8H), 1.69−1.61
(m, 12H), 1.37−1.34 (m, 12H), 0.92−0.89 (m, 12H). 13C{1H} NMR
(126 MHz, CDCl3): δ 144.1, 142.8, 141.5, 137.7, 134.9, 132.3, 131.8,
129.1, 128.7, 127.0(3), 127.0(1), 125.5, 125.4, 121.7, 120.3, 95.9,
95.5, 88.4, 87.2, 38.3, 36.1, 35.7, 31.6(9), 31.6(2), 31.3(9), 31.3(0),
Authors
Joydip De − Department of Chemical Sciences, Indian Institute
of Science Education and Research (IISER) Mohali,
Knowledge City, Manauli 140306, India; orcid.org/0000-
0002-3195-2608
Rohit Ashok Kumar Yadav − Department of Materials
Science and Engineering, National Tsing Hua University,
Hsinchu 30013, Taiwan
Rahul Singh Yadav − Department of Chemical Sciences,
Indian Institute of Science Education and Research (IISER)
Mohali, Knowledge City, Manauli 140306, India
Santosh Prasad Gupta − Department of Physics, Patna
University, Patna 800005, India
Mayank Joshi − Department of Chemical Sciences, Indian
Institute of Science Education and Research (IISER) Mohali,
Knowledge City, Manauli 140306, India; orcid.org/0000-
0003-2463-4967
Angshuman Roy Choudhury − Department of Chemical
Sciences, Indian Institute of Science Education and Research
(IISER) Mohali, Knowledge City, Manauli 140306, India;
orcid.org/0000-0002-4018-0451
Jayachandran Jayakumar − Department of Chemistry,
National Tsing Hua University, Hsinchu 30013, Taiwan;
orcid.org/0000-0003-3135-1535
Jwo-Huei Jou − Department of Materials Science and
Engineering, National Tsing Hua University, Hsinchu 30013,
Taiwan; orcid.org/0000-0002-9413-0206
Chien-Hong Cheng − Department of Chemistry, National
Tsing Hua University, Hsinchu 30013, Taiwan;
orcid.org/0000-0003-3838-6845
31.0, 29.8, 22.7, 22.6, 14.1(9), 14.1(7). IR (Neat film, KBr): νmax
/
cm−1 3028.3, 2954.8, 2928.3, 2870.1, 2856.3, 2205.7, 1688.9, 1604.1,
1515.7, 1499.8, 1465.7, 1407.8, 1378.3, 1276.1, 1261.4, 1187.6,
1109.2, 1018.4, 1004.8, 970.7, 895.8, 826.5, 810.6, 764.4, 749.7.
HRMS (MALDI) m/z: (M + H)+ calcd for C70H71 911.5556. Found
911.5526.
Compound 1.2. Compound 1.2 was synthesized by following same
procedure as that used in synthesizing 1.1. It was purified by column
chromatography (neutral alumina, hexane) to give the product as
1
yellow solid in 68% yield (300 mg) from 350 mg of 2.2. H NMR
(600 MHz, CDCl3): δ 7.77 (s, 2H), 7.62 (dd, J = 24.63 Hz, 8.25 Hz,
8H), 7.53 (dd, J = 19.8 Hz, 8.04 Hz, 8H), 7.27 (d, J = 8.04 Hz, 4H),
7.18 (d, J = 7.98 Hz, 4H), 2.67−2.62 (m, 8H), 1.67−1.60 (m, 8H),
1.38−1.30 (m, 20H), 0.92−0.87 (m, 18H). 13C{1H} NMR (126
MHz, CDCl3): δ 144.1, 142.8, 141.5, 137.7, 134.9, 132.3, 131.8,
129.1, 128.7, 127.0(3), 127.0(1), 125.5, 125.3 121.7, 120.0, 95.9, 95.5,
88.4, 87.2, 36.1, 35.7, 31.8, 31.6, 31.3(5), 31.3(1), 29.1, 22.7(5),
22.7(1), 14.2, 14.1. IR (Neat film, KBr): νmax/cm−1 3207.7, 2954.7,
2927.0, 2869.6, 2856.0, 2205.1, 1687.8, 1603.7, 1514.4, 1498.0,
1465.3, 1407.3, 1377.5, 1268.4, 1256.9, 1189.8, 1115.2, 1004.2, 969.3,
896.1, 826.24, 808.4, 764.6, 750.4. HRMS (MALDI) m/z: (M + H)+
calcd for C72H75 939.5869. Found 939.5837.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.joc.1c00742
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
S.K.P., J.D. acknowledge Project File Nos. CRG/2019/
000901/OC, and (09/947(0220)/2019/EMR-I), respectively.
We thank NMR, HRMS, SAXS/WAXS, and all departmental
facilities at IISER Mohali. We sincerely thank Dr. Manisha
Devi for critical reading of the manuscript.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.1c00742.
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