Self-recognition behavior of novel frameworks containing both urea and carboxylate anion motifs

Article abstract of DOI:10.1016/j.tet.2017.09.036

Molecular recognition based on hydrogen bond interaction plays a significant role in supramolecular self-assembly. In this work, we successfully developed a class of novel frameworks containing a urea in the recognition site and a carboxylate anion in the

Full text of DOI:10.1016/j.tet.2017.09.036

Tetrahedron 73 (2017) 6386e6391
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Self-recognition behavior of novel frameworks containing both urea
and carboxylate anion motifs
Zhiqiang Xu 1, Haojie Ge 1, Xie Han, Sheng Hua Liu, Xiang-Gao Meng**, Jun Yin*
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Molecular recognition based on hydrogen bond interaction plays a significant role in supramolecular self-
assembly. In this work, we successfully developed a class of novel frameworks containing a urea in the
recognition site and a carboxylate anion in the guest unit. The self-recognition model based on the
interaction between urea and carboxylate anion could induce the molecules to assemble into a highly
organized form. The crystal structures showed that they assembled in highly ordered two-dimensional
architectures. The optical properties showed that the position of carboxylate anion on the diphenyla-
cetylene backbone had an obvious influence on optical properties. The self-recognition strategy is useful
for the construction of highly ordered self-assembled architectures.
Received 24 August 2017
Received in revised form
16 September 2017
Accepted 19 September 2017
Available online 21 September 2017
Keywords:
Supramolecular
Self-recognition
Urea
© 2017 Elsevier Ltd. All rights reserved.
Carboxylate anion
Crystal
Optical properties
1. Introduction
ordered self-assembled structures through the intermolecular
NeH/O hydrogen bond between two urea motifs, as illustrated in
Over recent decades, supramolecular self-assembly has devel-
oped into one of the most fascinating topics in supramolecular
chemistry and a great deal of effort has been made in the design
and construction of novel supramolecular architectures. These ar-
chitectures assemble through many non-covalent intermolecular
Fig. 1A. The hydrogen bond interaction is usually employed as the
main driving force in the design of synthetic receptors for anion
recognition.24 Over past few decades, urea has been widely applied
as a hydrogen bond donor in the recognition of anions.25e29 For
example, numerous studies have shown that urea can bind to ac-
etate by forming two NeH/O hydrogen bonds in an 8-member
ring, similar to the 6-member ring formed in the self-assembling
process shown in Fig. 1B.30e35
It is possible that the interaction between urea and the
carboxylate anion could also be used as an alternative model in self-
assembly when the urea unit and the carboxylate anion are both
installed on a molecule. Based on this self-recognition concept, we
reported two novel building blocks that both contain a urea in the
recognition site and a carboxylate anion in the guest unit. The
crystal structures indicated that these building blocks could form
two different highly ordered two-dimensional architectures. When
the urea unit and carboxylate unit were located in the plane of the
diphenylacetylene backbone, the molecule presented a parallel
wave-shaped two-dimensional architecture with an intersection
angle of 110ꢀ. When the urea unit was installed on the para-
position of phenylacetylene unit and the carboxylate unit was
installed on the meta-position of another phenylacetylene unit, the
interactions, such as hydrogen bonding,
p-p interaction, van der
Waals forces, hydrophobic effect, ionic interactions and coordina-
tive interactions.1e12 Supramolecular self-assembly based on
hydrogen bond interaction is considered to be one of the most
versatile strategies for the construction of highly ordered self-
assembling architectures due to many options for hydrogen bond
donors and acceptors.13e22
Urea is a popular building block that has been widely applied in
self-assembling materials.23 The NH on the urea unit can be used as
a hydrogen bond donor while the carbonyl group can play the role
of hydrogen bond acceptor.
Therefore, molecules containing the urea unit can form highly
* Corresponding author.
** Corresponding author.
E-mail addresses: mengxianggao@mail.ccnu.edu.cn (X.-G. Meng), yinj@mail.
ccnu.edu.cn (J. Yin).
molecule showed
a twisted wave-shaped two-dimensional
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.tet.2017.09.036
0040-4020/© 2017 Elsevier Ltd. All rights reserved.

Z. Xu et al. / Tetrahedron 73 (2017) 6386e6391
6387
compounds 1a and 1b. Single crystals of compounds 1a and 1b
suitable for crystallographic analysis were grown by slow evapo-
ration of methanol (Fig. 2). Crystal structure analysis indicates that
1a and 1b were crystallized in the non-centrosymmetric ortho-
rhombic Fdd2 and monoclinic P21/c space group, respectively. In
both their asymmetric units, there are each one host urea de-
rivatives anion and one counter cation N(t-Bu)4. According to their
crystal structures, the recognition of urea units and carboxylate
moieties play an important role in the crystal packing.43e45 The
bond lengths and angles of 1a and 1b are listed, and the crystal data
and structural refinements of 1a and 1b are summarized in
Tables S1e5.
Fig. 1. The schematic representation of the self-assembly of two urea groups (A) and
the binding mode between urea and acetate groups (B).
architecture with an intersection angle of ca. 124ꢀ. It was worth
mentioning that the different angle between the urea-based phe-
nylacetylene backbone and carboxylate group affected the self-
assembling behavior.
As shown in Fig. 2, due to a steric effect from the carboxylate
group, the molecular conformations in 1a and 1b differ from each
other largely. For instance, i) the central benzene ring in 1a make
two dihedral angles of 11.20(2)ꢀ and 8.97(2)ꢀ with the two neigh-
boring phenyl groups. However, the two angles in 1b are 23.67(2)ꢀ
and 9.77(2)ꢀ, indicating an apparent molecular non-planarity in 1b.
ii) As for the often generated intermolecular R22(8) hydrogen-bond
motif between a urea and a carboxylate group, the urea was twisted
away from the carboxylate group by 9.50(2)ꢀ in 1a. In comparison, a
large angle of 42.26(2)ꢀ was resulted in 1b due to a steric effect
from the carboxylate.
In their crystal packing, the arrangement of the urea and
carboxylate groups of 1a and 1b show that they could form well-
organized, multi-dimensional architectures by using the
hydrogen bonding as the driving force (Figs. 3e4). According to the
crystal structure of compound 1a, the molecules possessed two
2. Results and discussion
2.1. Synthesis
The synthetic route for the preparation of compounds 1a and 1b
is outlined in Scheme 1. The deprotection of 4-((trimethylsilyl)
ethynyl)aniline 2 formed intermediate 3, according to previous
literature.36 Subsequently, the terminal alkyne 3 was subjected to
the palladium-catalyzed Sonogashira coupling reaction with 4a and
4b,37e39 affording respective compounds 5a and 5b in yields of
84e88%. Next, 5a and 5b were reacted with isocyanatobenzene 6
for 12 h at room temperature to form respective urea 7a and 7b in
good yields.40 The urea-based carboxylic acids 8a and 8b were
obtained by the hydrolysis of 7a and 7b under alkaline conditions.
Subsequent transformation from carboxylic acid to carboxylate
anion was performed to give target molecules 1a and 1b in the
yields of 52e54%, respectively.
intermolecular NeH/O hydrogen bonds (dN
¼ 2.713(3) Å/
…
O
2.896(3) Å), forming an R22(8) hydrogen-bonded ring and resulting
in the one-dimensional chain along the [0e13] direction by glide-
plane symmetry operation (Fig. 3A). Each [0e13] hydrogen-
bonding chain may be connected to another by CeH/O interac-
tion or Coulomb electrostatic interactions between the anionic and
cationic ions. As for two neighboring groups of 1D chain, regular
quadrilateral grids were formed between them. For compound 1b,
similar R22(8) hydrogen-bonded motif consisted of two intermo-
lecular NeH/O hydrogen bonds (dN2 … O2 ¼ 2.779(2) Å and dN3 …
All of the intermediate and target molecules were well charac-
terized by standard spectroscopic techniques such as NMR spec-
troscopy and mass spectrometry.
¼ 2.847(2) Å, symmetry code: x, 3/2 - y, z - 1/2) could be found to
O3
2.2. Crystal structures of 1a and 1b
mainly stabilize the [001] chain (Fig. 3B). It is worthy mentioned
that the donor plane (H2/N2/C7/N3/H3) twisted away from the
carboxylate plane (O2/C21/O3,1 - x, 2 - y, - z) with an dihedral angle
of 39.0(2)ꢀ, which should be resulted by a steric hindrance of the
benzene ring.46 Adjacent [001] chains were linked together by one
The solid-state structure is very significant for the investigation
of the self-assembling behavior in supramolecular systems.41,42
Great efforts were expended to obtain single crystals of
Fig. 2. Top view of the single crystal structures of 1a (A) and 1b (B). For clarity, the
Scheme 1. Synthetic route of compounds 1a and 1b.
tetrabutylammonium cations were both omitted in them.

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Z. Xu et al. / Tetrahedron 73 (2017) 6386e6391
Fig. 3. One-dimensional R22(8) hydrogen-bonded chains in crystal packing of com-
pounds 1a (A) and 1b (B). Hydrogen bonds are shown as green dashed lines. Symmetry
codes: I ¼ 1/4-x, y-1/4, 3/4 þ z; II ¼ x, 3/2-y, z-1/2. For clarity, the tetrabutyl ammonium
cations were omitted.
weak CeH/O interaction (dH4 … O2 ¼ 2.505(2) Å symmetry code: 1
- x, 2 - y, - z), forming the 2D layer structure parallel to the (100)
plane (Fig. 4B). Further analysis between these layer structures
indicates one small CeH …
atom and acetylene
worth mentioning that in crystal of 1b, larger grid between two
groups of 1D hydrogen-bonded chains were also shaped which
should be ascribed to the meta-sited carboxylate group.
p interaction exists between the C26
system (dH26 … centroid ¼ 2.926(2) Å). It was
p
Fig. 5. The intermolecular CeH/O interaction of compound 1a (A) and 1b (B) (The
tetrabutylammonium salts were omitted for clarity).
As for the cations in 1a and 1b, they are both hydrogen-bonded
anchored to the carboxyl oxygen of the urea group by a non-
classical intermolecular CeH/O interaction (Fig. 5) and the ge-
ometries of CeH/O hydrogen bonds for 1a and 1b are listed
(Tables S3e4). In both the crystal structure, the N(t-Bu)4 cations
effectively inhibit a pure urea tape formation based on a six-
membered hydrogen bonded ring. In one word, even the different
molecular conformation and crystal packing in 1a and 1b, the
hetero R22(8) hydrogen motif should be the main driving force in
the molecular self-recognition.
2.3. Optical properties of 1a and 1b
The optical properties of 1a and 1b were investigated by UV/vis
absorption and fluorescence spectrometry based on our previous
works.47e54 As seen in Fig. 6, compounds 1a and 1b showed well-
resolved absorption bands in the UV region with maximum ab-
sorption around at 310 nm in acetonitrile solution. Compared to the
absorption spectra in solution, the thin film sample of 1a revealed a
broader absorption band along with a red-shift of approximately
15 nm (Fig. 6A). However, Compound 1a showed nearly identical
fluorescence spectra (350e600 nm) between solution and thin film
with a maximum emission at 425 nm. In comparison to compound
1a, the emission of compound 1b displayed an obvious blue shift in
solution and in the solid state. These results suggest that the
different assembly and aggregation can affect their fluorescence
manners.
Subsequently, the concentration-dependence of compounds 1a
and 1b in UVevis absorption and fluorescence spectrometry was
investigated in acetonitrile solution. When the concentration of 1a
was increased (0.01e100 mM), the maximum absorption at 310 nm
(ε ¼ 1.00 ꢁ 104 Mꢂ1 cmꢂ1) distinctly increased (Fig. S3). A similar
phenomenon was observed in the UVevis absorption spectra of 1b
(ε ¼ 3.84 ꢁ 104 Mꢂ1 cmꢂ1) (Fig. S4). The fluorescence emission of 1a
at 440 nm gradually increased, and the maximum emission blue-
shifted to 425 nm along with an enhancement of fluorescence in-
tensity when the concentration of 1a was increased past 5 mM, as
presented in Fig. 7A. Similarly, the fluorescence emission of 1b at
435 nm gradually increased with increasing concentration and
accompanied the blue-shift observed when the concentration of 1b
was above 1
mM (Fig. 7B). Interestingly, when the concentration of
1b was over 30
mM, the fluorescence intensity began to decrease
with increasing concentration (Fig. 7C). More probably, a higher
concentration of compound 1b led to the aggregation and the
fluorescence decrease probably due to the self-bleaching or self-
quenching.55e57 These results suggested that the position of
carboxylate anion on the diphenylacetylene backbone had an in-
fluence on optical properties.
Fig. 4. Part of the crystal packing views of compound 1a (A) and 1b (B) showing the
grid formation between two adjacent two-dimensional layer structures. For clarity, the
tetrabutyl ammonium cations were omitted.

Z. Xu et al. / Tetrahedron 73 (2017) 6386e6391
6389
Fig. 6. Normalized UVevis absorption and photoluminescence spectra of (A) 1a and
(B) 1b in MeCN (10 M) and in thin film.
m
2.4. Theoretical calculation
Consequently, to gain a better insight into the relationship of
structure with excited state, the structures and frontier molecular
orbital profiles of 1a and 1b were carried out by using time-
dependent density functional theory (TD-DFT) calculations at the
B3LYP/6-31G* level in a suite of the Gaussian 09 program. Details of
the optimized structures and molecular orbital were shown in
Fig. 8. Their absorption spectra and the molecular orbital containing
the main electronic transitions with the largest oscillator strength
have been given (Fig. 8). As shown, compound 1a presented a
planar conjugated backbone. The HOMO coefficient was nearly
distributed over the whole molecule while its LUMO was pre-
dominantly located in the urea-based diphenylacetylene-carbox-
ylate moiety. And an intense S0eS1 transition was predicted at
around 352 nm with the largest oscillator strength of 1.8957 and
contribution of 70% from HOMO to LUMO transition (Table S6 and
Fig. S5). For compound 1b, the HOMO orbital was almost assigned
to the whole molecule whereas the electron density of the LUMO
orbital was largely distributed over the urea-based phenylacetylene
backbone, implying that it involved in an electron transfer from
benzo-urea scaffold to phenylacetylene moiety as well as com-
pound 1a. The S0eS1 excitation was predicated to be the dominant
transition with a maximum wavelength of 341 nm, the largest
oscillator strength of 1.7828 and contribution of 70% from HOMO to
LUMO (Table S6 and Fig. S5). Observations obtained from the TD-
DFT implied that compounds 1a and 1b were fluorescent, which
was well in agreement with the experimental findings. More,
compound 1a showed a narrower energy band gap (3.94 eV) in
comparison to compound 1b (4.07 eV), probably due to the effect of
Fig.
(0.01
(30 mMe100 m
7. The
fluorescence spectra
M) (A) and 1b with various concentration (0.01
M) (C) in MeCN solution. (lex ¼ 315 nm, slit: 5/5 nm).
of
1a with
various
concentration
m
Me100
m
mMe30 mM) (B) and
different position of carboxylate anion on the molecular backbone.
3. Conclusions
In summary, two novel building blocks containing both a
recognition site urea and a carboxylate anion were reported, and
their self-recognition behavior and optical properties were inves-
tigated. Their crystal structures showed that they could form the
well-organized, two-dimensional architectures through the self-
recognition driving force and their configuration were closely
related to the position of the urea group and carboxylate anion on
the diphenylacetylene backbone. The optical properties indicated
that the position of the carboxylate anion on the diphenylacetylene
backbone had an obvious influence on the optical properties and a

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Z. Xu et al. / Tetrahedron 73 (2017) 6386e6391
the commands ‘DFIX’ and ‘ISOR’ were used to constrain some
related bond lengths and thermal factors.
4.3. Spectroscopic measurements
The UVevis absorption and fluorescence spectra were measured
on U-3310 UV Spectrophotometer and Fluoromax-P luminescence
spectrometer (HORIBA JOBIN YVON INC.), respectively. The width of
both excitation and emission slits were set at 5 nm, and the step
and dwell time were set at 5.00 nm and 0.6 s, respectively.
4.4. Synthesis
4.4.1. Synthesis of 5a
To a solution of 3 (117 mg, 1.0 mmol), methyl 4-iodobenzoate
(288 mg, 1.1 mmol), Pd(PPh3)2Cl2 (21 mg, 0.03 mmol), and CuI
(5 mg, 0.03 mmol) in the mixture of THF (20 mL) and triethylamine
(20 mL) was added under a nitrogen atmosphere. After being stir-
red at 70 ꢀC for 6 h, the solvent was removed under reduced
pressure. The residue was purified by silica gel column chroma-
tography with dichloromethane/petroleum ether (1:2, v/v) as the
eluent to afford the pure product 5a (221 mg, 0.88 mmol) as a light
brown powder in 88% yield. 1H NMR (400 MHz, CDCl3):
Fig. 8. Frontier molecular orbital profiles of 1a and 1b based on TD-DFT calculations at
the B3LYP/6-31G* level by using the Gaussian 09 program.
higher concentration was required to induce the aggregation and
the fluorescence decrease when the carboxylate anion was located
on the meta-position of urea-based diphenylacetylene backbone.
Our research provides a simple and effective strategy to construct
highly ordered supramolecular architectures by through self-
recognition. It is expected that this self-recognition system will
be useful for the design and construction of more complicated
supramolecular systems in the future.
d
(ppm) ¼ 7.99 (d, J ¼ 8.0 Hz, 2H, Ph-H), 7.54 (d, J ¼ 8.0 Hz, 2H, Ph-
H), 7.35 (d, J ¼ 8.0 Hz, 2H, Ph-H), 6.65 (d, J ¼ 8.0 Hz, 2H, Ph-H), 3.92
(s, 3H, CH3), 3.87 (s, 2H, NH2).
4.4.2. Synthesis of 5b
The synthesis of 5b was similar to 5a. Light brown powder, 84%
yield. 1H NMR (400 MHz, CDCl3):
d
(ppm) ¼ 8.17 (s, 1H, Ph-H), 7.95
(d, J ¼ 8.0 Hz, 1H, Ph-H), 7.66 (d, J ¼ 8.0 Hz, 1H, Ph-H), 7.40 (t,
J ¼ 8.0 Hz, 1H, Ph-H), 7.35 (d, J ¼ 8.0 Hz, 2H, Ph-H), 6.65 (d,
J ¼ 8.0 Hz, 2H, Ph-H), 3.93 (s, 3H, CH3), 3.85 (s, 2H, NH2). 13C NMR
4. Experimental
(100 MHz, CDCl3):
d
(ppm) ¼ 166.1, 146.4, 135.0, 132.6, 132.0, 129.8,
128.1, 128.0, 123.9, 114.3, 111.6, 90.7, 85.9, 51.8. MS (EI) m/z: calcd for
16H13NO2 251.09, found 251.24.
4.1. Materials and instrumentation
C
All manipulations were carried out under an argon atmosphere
by using standard Schlenk techniques, unless otherwise stated. All
commercials were used as received without further purification. 1H
and 13C NMR spectra were collected on American Varian Mercury
Plus 400 spectrometer (400 MHz) in DMSO-d6, CD3OD and CDCl3
with tetramethylsilane (TMS) as an internal standard. The UVevis
absorption and fluorescence spectra were measured on U-3310 UV
Spectrophotometer and Fluoromax-P luminescence spectrometer
(HORIBA JOBIN YVON INC.), respectively. Mass spectra were
measured in the EI mode or MALDI mode. The X-ray crystal-
structure determinations were obtained on a Bruker APEX DUO
CCD system. The theoretical calculation in the present studies were
performed at the B3LYP/6-31G* level by using the Gaussian 09
program.
4.4.3. Synthesis of 7a
To a solution of 5a (251 mg, 1.0 mmol), isocyanatobenzene
(142 mg,1.2 mmol) in dry DCM (50 mL) was added under a nitrogen
atmosphere. After the resulting solution was heated to reflux and
stirred for 12 h, the solvent was removed under reduced pressure.
The residue was purified by silica gel column chromatography with
dichloromethane/petroleum ether (3:1, v/v) as the eluent to afford
the pure compound 7a (111 mg, 0.3 mmol) as a white crystalline
solid in 76% yield. 1H NMR (400 MHz, DMSO-d6):
d
(ppm) ¼ 9.01 (s,
1H, NH), 8.81 (s, 1H, NH), 7.98 (d, J ¼ 8.0 Hz, 2H, Ph-H), 7.66 (d,
J ¼ 8.0 Hz, 2H, Ph-H), 7.58e7.49 (m, 4H, Ph-H), 7.46 (d, J ¼ 8.0 Hz,
2H, Ph-H), 7.29 (t, J ¼ 8.0 Hz, 2H, Ph-H), 6.99 (t, J ¼ 8.0 Hz,1H, Ph-H),
3.87 (s, 3H, CH3). 13C NMR (100 MHz, DMSO-d6)
d
(ppm) ¼ 170.8,
157.4, 146.0, 144.5, 137.6, 136.5, 134.5, 133.9, 132.6, 127.6, 123.4,
123.1, 119.5, 98.1, 92.6, 57.4. MS (EI) m/z: calcd for C23H18N2O3
370.13, found 370.40.
4.2. X-ray diffraction (XRD) crystallography
Single-Crystal of 1a and 1b are both too slim to be collected
normally, giving their good data sets. In details, crystal 1a was
4.4.4. Synthesis of 7b
collected on a Bruker Apex (II) Duo diffractometer using I
source (
¼ 1.54178 Å). Crystal of 1b was done using the graphite
monochromated Mo-Ka (
¼ 0.71073 Å) radiation at ambient
mS-Cu
The synthesis of 7b was similar to 7a. White solid, 82% yield. 1H
l
NMR (400 MHz, DMSO-d6):
d
(ppm) ¼ 8.92 (s, 1H, NH), 8.75 (s, 1H,
l
NH), 8.04 (s, 1H, Ph-H), 7.95 (d, J ¼ 8.0 Hz, 1H, Ph-H), 7.80 (d,
J ¼ 8.0 Hz, 1H, Ph-H), 7.59 (d, J ¼ 8.0 Hz, 1H, Ph-H), 7.52 (s, 4H, Ph-
H), 7.46 (d, J ¼ 8.0 Hz, 2H, Ph-H), 7.30 (t, J ¼ 8.0 Hz, 2H, Ph-H), 6.98
(t, J ¼ 8.0 Hz, 1H, Ph-H), 3.88 (s, 3H, CH3). 13C NMR (100 MHz,
temperature. Empirical absorption correction was applied for them.
The structures were solved by direct methods and refined by the
full-matrix least-squares methods on F2 using the SHELX-97 soft-
ware. All non-hydrogen atoms were refined an-isotropically. All of
the hydrogen atoms were placed in the calculated positions. For 1b,
the same carbon atoms were treated as disorder. In the refinement,
DMSO-d6):
d
(ppm) ¼ 168.1, 154.9, 143.3, 142.1, 138.1, 135.0, 134.2,
132.8, 132.0, 131.4, 126.0, 124.7, 121.0, 120.6, 117.2, 93.5, 89.7, 55.0.
MS (EI) m/z: calcd for C23H18N2O3 370.13, found 370.37.

Z. Xu et al. / Tetrahedron 73 (2017) 6386e6391
6391
4.4.5. Synthesis of 8a
research funds of CCNU from the colleges' basic research and
operation of MOE (CCNU16A02004).
To a solution of 7a (111 mg, 0.3 mmol) in THF (20 mL) was added
1 M NaOH aqueous solution (15 mL) under a nitrogen atmosphere.
After the resulting solution was stirred at 60 ꢀC for 12 h, the reac-
tion mixture was cooled to room temperature. Then the solution
was acidified to a pH of 2 using 6 M HCl and extracted with ethyl
acetate (4 ꢁ 80 mL). The organic layer was washed with H2O
(30 mL), dried with anhydrous sodium sulfate and concentrated in
vacuum. The residue was recrystallized from DCM/hexane to afford
the pure product 8a (90 mg, 0.25 mmol) as a light brown powder in
Appendix A. Supplementary data
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.tet.2017.09.036.
References
84% yield. 1H NMR (400 MHz, DMSO-d6):
d
(ppm) ¼ 10.51 (s, 1H),
€
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NMR (100 MHz, CD3SOCD3):
d
(ppm) ¼ 171.5, 157.1, 145.7, 144.3,
137.3, 136.2, 135.1, 134.5, 133.7, 133.0, 127.0, 122.3, 123.0, 119.5, 97.7,
92.7. MS (EI) m/z: calcd for C22H16N2O3 356.12, found 356.61.
4.4.6. Synthesis of 8b
The synthesis of 8b was similar to 8a. Light brown powder, 78%
yield. 1H NMR (400 MHz, CD3SOCD3):
d 8.93 (s, 1H, NH), 8.76 (s, 1H,
NH), 8.03 (s, 1H, Ph-H), 7.94 (d, J ¼ 8.0 Hz, 1H, Ph-H), 7.77 (d,
J ¼ 8.0 Hz,1H, Ph-H), 7.55 (t, J ¼ 4.0 Hz, 1H, Ph-H), 7.48e7.54 (m, 4H,
Ph-H), 7.46 (d, J ¼ 8.0 Hz, 2H, Ph-H), 7.29 (t, J ¼ 8.0 Hz, 2H, Ph-H),
6.99 (t, J ¼ 8.0 Hz, 1H, Ph-H). 13C NMR (100 MHz, CD3SOCD3):
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8038e8155.
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17. Seki T, Lin X, Yagai S. Asian J Org Chem. 2013;2:708e724.
18. G1owacki ED, Irimia-Vladu M, Bauer S, Sariciftci NS. J Mater Chem B. 2013;1:
3742e3753.
d
(ppm) ¼ 169.3, 154.9, 143.2, 142.1, 137.8, 135.0, 134.4, 134.0, 131.8,
131.7, 131.5, 125.8, 124.7, 121.0, 120.6, 117.3, 93.3, 89.9. MS (EI) m/z:
calcd for C22H16N2O3 356.12, found 356.36.
19. Lee S, Flood AH. J Phys Org Chem. 2013;26:79e86.
20. Zhao X, Li ZT. Chem Commun. 2010;46:1601e1616.
4.4.7. Synthesis of 1a
To a solution of 8a (53 mg, 0.15 mmol) in dry methanol (20 mL)
was added a solution of 0.8 M Bu4NOH (0.50 mL, 0.40 mmol) in dry
methanol (40 mL) dropwise over 2 h. After the resulting solution
was stirred at room temperature for 12 h, the solvent was removed
under reduced pressure. The residue was recrystallized from DCM
to afford the pure product 1a (47 mg, 0.08 mmol) as a light brown
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powder in 52% yield. 1H NMR (400 MHz, CD3OD):
d
(ppm) ¼ 7.85 (d,
J ¼ 8.0 Hz, 2H, NH), 7.45e7.38 (m, 6H, Ph-H), 7.35 (d, J ¼ 8.0 Hz, 2H,
Ph-H), 7.21 (t, J ¼ 8.0 Hz, 2H, Ph-H), 6.94 (t, J ¼ 8.0 Hz, 1H, Ph-H),
3.10e3.19 (m, 8H, NeCH2), 1.57 (dt, J ¼ 16.0, 8.0 Hz, 8H, CH2), 1.33
(dd, J ¼ 16.0, 8.0 Hz, 8H, CH2), 0.94 (t, J ¼ 8.0 Hz, 12H, CH3). The
solubility of 1a was not good, so it was hard to get its 13C NMR.
MALDI-TOF: MS m/z 357.20 [M - Bu4Nþ þ 2Hþ]þ; calcd exact mass
597.39.
ꢁ
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ꢁ
ꢁ
ꢁ
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33. Jimenez MB, Alcazar V, Pelaez R, Sanz F, Fuentes de Arriba AL, Caballero MC.
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ꢁ
ꢁ
36. Marques-Gonzalez S, Yufit DS, Howard JA, et al. Dalton Trans. 2013;42:
338e341.
4.4.8. Synthesis of 1b
The synthesis of 1b was similar to 1a. Light brown powder, 54%
37. Ou YP, Jiang C, Wu D, et al. Organometallics. 2011;30:5763e5770.
38. Wu D, Zhang H, Liang J, et al. J Org Chem. 2012;77:11319e11324.
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yield. 1H NMR (400 MHz, CD3OD):
d
(ppm) ¼ 8.06 (s, 1H, NH), 7.90
(d, J ¼ 8.0 Hz, 1H, NH), 7.52 (d, J ¼ 8.0 Hz, 1H, Ph-H), 7.45e7.50 (m,
4H, Ph-H), 7.43 (d, J ¼ 8.0 Hz, 2H, Ph-H), 7.35 (t, J ¼ 8.0 Hz, 1H, Ph-
H), 7.28 (t, J ¼ 8.0 Hz, 2H, Ph-H), 7.02 (t, J ¼ 4.0 Hz, 1H, Ph-H),
3.18e3.25 (m, 8H, NeCH2), 1.64 (dd, J ¼ 16.0, 8.0 Hz, 8H, CH2),
1.40 (dd, J ¼ 16.0, 8.0 Hz, 8H, CH2), 1.01 (t, J ¼ 8.0 Hz, 12H, CH3). The
solubility of 1b was not good, so it was hard to get its 13C NMR.
MALDI-TOF: MS m/z 357.19 [M - Bu4Nþ þ 2Hþ]þ; calcd exact mass
597.39.
12703e12709.
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Acknowledgements
The authors acknowledge financial support from National Nat-
ural Science Foundation of China (21676113, 21402057, 21472059);
Youth Chen-Guang Project of Wuhan (2016070204010098). Sup-
ported by the 111 Project B17019 and the Ministry-Province Jointly
Constructed Base for State Key Lab-Shenzhen Key Laboratory of
Chemical Biology, Shenzhen; Supported by self-determined
57. Chen WY, Young LJ, Lu M, et al. Nano Lett. 2017;17:143e149.