Synthesis and structure of supramolecular compound with ethyl 2-(4-aminophenoxy)acetate based on 18-crown-6

Article abstract of DOI:10.1002/cjoc.201200807

The title ammonium compound ethyl 2-(4-aminophenoxy)acetate (C ₁₀H₁₃NO₃, I) and its crown ether inclusion complex {[(C₁₀H₁₄NO₃)·(18-crown-6)] ⁺[PF₆]^-, II} (

Full text of DOI:10.1002/cjoc.201200807

COMMUNICATION
DOI: 10.1002/cjoc.201200807
Synthesis and Structure of Supramolecular Compound with
†
Ethyl 2-(4-Aminophenoxy)acetate Based on 18-Crown-6
Wang, Wenxiang(王文祥)
Sun, Suwen(孙素文)
Xiong, Rengen*(熊仁根)
Ordered Matter Science Research Center, Southeast University, Nanjing, Jiangsu 211189, China
The title ammonium compound ethyl 2-(4-aminophenoxy)acetate (C10
H13NO
3
, I) and its crown ether inclusion
＋
－
complex {[(C10
H
14NO
3
)•(18-crown-6)] [PF ] , II} (18-crown-6＝1,4,7,10,13,16-hexaoxacyclo-octadecane) were
6
1
synthesized. The ammonium compound I was determined by H NMR, IR and ESI-MS techiniques. X-ray crystal-
lography reveals that compound I crystallizes in the triclinic system with space group of P-1, all the atoms in I are
almost coplanar except H, and N—H…O hydrogen bonds lead to the formation of one dimensional chain. The ro-
tator-stator-like compound II was crystallizes in the centrosymmetric monoclinic system with space group of P21/c.
The supramolecular was formed via N—H…O hydrogen-bond interactions. Temperature-dependent dielectric con-
stants of compound II were measured.
Keywords solid-phase synthesis, crystal structure, crown ether, phase transition
[
11]
Introduction
anion-activated catalysis.
It is therefore vital to de-
sign and synthesize novel crown ether complexes and to
explore their various properties.
Owing to their widespread applications in resonators,
filters, and other key components in microwave com-
munication systems, much attention has been devoted to
the preparation of suitable materials displaying excellent
As one part of our continuing studies on crown
[12-16]
ethers-based dielectric-ferroelectric materials,
we
[1,2]
report here the synthesis (Scheme 1), structural charac-
terization of the title ammonium compound and its
crown ether inclusion complex.
dielectric constant.
The temperature-dependent di-
electric response, especially in relatively high frequency
range, is very useful in searching for phase transitions
[3,4]
materials.
There are only a limited number of mate-
rials which approximately meet the stringent dielectric
constant requirements. While there have been a variety
Scheme 1 Synthesis of the compounds I and II
[
5,6]
O
O
O
of studies on pure inorganic compounds,
examples
OH
on supramolecular compounds (which would possess
the preponderant properties of both inorganic and or-
ganic compounds) as dielectric materials have remained
a significant challenge.
O
O
K2CO3
Fe/NH Cl
4
acetone
Br
NO2
NO2
Great deals of interest were devoted to crown ethers
due to their ability to form non covalent and hydrogen-
bonded complexes with ammonium cations. Charge
transfer and hydrogen-bonded interactions of crown
ethers play an important role in various template, recog-
nition and complexation phenomena in supramolecular
O
O
O
O
O
O
O
O
O
O
O
O
-
PF
6
[
7,8]
chemistry.
Crown ether’s complexation process can
O
+
O
O
O
O
NH
accelerate salt solubility and anion reactivity in
nonaqueous solvents, enabling their potential applica-
tion in fields of mediated ion transport, molecular rec-
3
HPF , MeOH
6
NH2
O
I
[
9]
[10]
II
ognition, self-assembly,
crystal engineering and
*
E-mail: xiongrg@seu.edu.cn
Received August 8, 2012; accepted September 4, 2012.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201200807 or from the author.
Dedicated to the 80th Anniversary of Chinese Chemical Society.
†
Chin. J. Chem. 2012, 30, 1957—1961
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1957

Wang, Sun & Xiong
COMMUNICATION
Experimental
(m), 1670 (s), 1512 (s), 1452 (w), 1352 (w), 1247 (s),
－
1
1
103 (m), 962 (m), 840 (s), 617 (w), 557 (w) cm .
Materials and instruments
Anal. calcd for C22 PF : C 43.64, H 6.33, N 2.31,
H38NO
9
6
Commercially available reagents were used as re-
ceived without further purification. Infrared spectra
were taken on a Bruker Vector 22 spectrophotometer as
F 18.83, P 5.12, O 23.78; found C 43.62, H 6.36, N
2.29.
－
1
X-ray crystallography
KBr pellets in the 4000—400 cm region. Elemental
analysis (C, N, and H) was performed with a
Perkin-Elmer 2400 elemental analyzer. The H NMR
spectrum was obtained with a Bruker Am-300 spec-
X-ray diffraction experiment was carried out using a
Rigaku SCX mini diffractometer with Mo Kα radiation
(λ＝0.71073 Å). Resolution of the detector is 13.6612
1
－
1
trometer operating at 300 MHz using CDCl
3
as solvent
pixels•mm . Data collection, cell refinement and data
[
17]
at room temperature. The crystal structures were deter-
mined by a Rigaku SCX mini diffraction meter. Dielec-
tric capacitance and dielectric loss measurements were
performed with pure compounds powder using an
automatic impedance TongHui2828 Analyzer.
reduction: CrystalClear 1.4.0.
The structure was
solved by direct methods and refined by the full-matrix
2
method based on F using the SHELXL97 software
[18]
package. All non-hydrogen atoms were refined aniso-
tropically, all H atoms were placed in geometrically
idealized positions and constrained to ride on their par-
ent atoms. The crystal data and some details of the
structure determination are summarized in Table 1.
Crystallographic data for the structure reported here
have been deposited with the Cambridge Crystallo-
graphic Data Centre (Deposition No. CCDC-890243,
890244). The data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/perl/catreq.cgi (or from the
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; Fax:
0044-1223-336033; e-mail: deposit@ccdc.cam. ac.uk).
Preparation of substituted benzyl ammonium I
To a solution of 4-nitrophenol (6.95 g, 0.05 mol) in
5
0 mL of acetone was added potassium carbonate (7.59
g, 0.055 mol). The mixture was refluxed for 30 min
with stirring. 8.5 g (0.051 mol) of ethyl 2-bromoacetate
and 0.2 g of KI were added and the mixture was re-
fluxed for 10 h. When the reaction finished by TLC
monitoring, heating was stopped and the mixture was
dumped into the ice water with violent stirring. The
mixture was filtered and washed with cold water, dried
in air, pale yellow ethyl 2-(4-nitrophenoxy) acetate was
obtained. The product was used for next step without
further purification.
Dielectric constant measurements
Because of the difficulty in obtaining large crystals,
the powderpressed pellets of compound II were used in
dielectric studies of capacitance and dielectric loss fac-
tor measurements. The measuring AC voltage was 1 V.
The pressed-powder sheet deposited with carbon con-
ducting glue was used for dielectric studies. The sam-
ples have been placed inside a dielectric cell whose
temperature-dependent dielectric constants were meas-
ured.
5
.35 g of NH Cl was added to the solution of 5.625 g
4
(
0.025 mol) of ethyl 2-(4-nitrophenoxy) acetate in 20
mL of 50% ethanol. The mixture was refluxed for 30
min with stirring, then 4.2 g (0.075 mol) of Fe powder
was added separately and the mixture was refluxed for
another 1 h. The mixture was hot filtered and the filter
cake was washed with hot water. Red crystal product of
compound I was obtained after the filtrate was cooled to
1
room temperature. H NMR (300 MHz, CDCl ) δ:
Results and Discussion
3
1
4
6
3
.28—1.32 (m, 3H, CH ), 3.37 (s, 2H, NH ), 4.23—
3 2
Upon condensation of 4-nitrophenol with ethyl
.30 (m, 2H, O-CH -C), 4.55 (s, 2H, OC-CH ), 6.64—
2
2
2
-bromoacetate, the use of KI remarkably shortened the
.67 (m, 2H, ArH), 6.76—6.80 (m, 2H, ArH); IR ν:
448 (w), 3346 (w), 2978 (w), 2908 (w), 1749 (s), 1626
reaction time. The ratio of ethanol and water is the
critical factor in the reduction reaction of the iron pow-
der, and 50% gives the best result. The infrared spec-
trum of compound I exhibits the characteristic peaks at
(
s), 1512 (s), 1442 (m), 1384 (m), 1332 (m), 1277 (s),
217 (m), 1088 (w), 1024 (w), 821 (s), 794 (w), 601 (w)
cm ; ESI-MS m/z: 196.40 [M＋H ]. Anal. calcd for
: C 61.53, H 6.71, N 7.18; found C 61.49, H
.76, N 7.15.
1
－
1
＋
－
1
3
448 and 3346 cm , which are assigned to the ν(NH ).
2
－
Strong peak at 1749 cm refers to the ν(C＝O), weak
peaks at 2978 and 2908 cm refer to the ethyl in ester
group. The H NMR and ESI-MS spectra for the com-
10 3
C H13NO
6
1
－
1
1
Synthesis of the complexes II
Compound I (2 mmol, 0.39 g) and 18-crown-6 (2
mmol, 0.528 g) were dissolved in methanol (20 mL),
followed by hexafluorophosphate (2 mL). Single crys-
tals of II suitable for X-ray diffraction analysis were
obtained via slow evaporation from the methanol solu-
tion at room temperature over one week. Yield 62%
pound I are consistent with the theoretical values.
Single crystals of II were grown by a standard
evaporation method of a mixed solution of ethyl
2-(4-aminophenoxy)acetate, hexafluorophosphate and
3
18-crown-6 in CH OH at room temperature. In the in-
frared spectrum of compound II, characteristic peak of
－
1
(
based on compound I). IR ν: 3446 (w), 2916 (w), 1753
hexafluorophosphate appears at 840 cm .
1958
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Chin. J. Chem. 2012, 30, 1957—1961

Synthesis and Structure of Supramolecular Compound with Ethyl 2-(4-Aminophenoxy)acetate
Table 1 Summary of crystallographic data for compounds I and II
I
II
Molecular formula
Formular weigh
Crystal system
Space group
Temperature/K
a/Å
C
10
H
13NO
3
22 9 6
C H38NO PF
195.21
Triclinic
P-1
605.5
Monoclinic
P2 /c
1
298
170(2)
12.540(8)
14.585(8)
16.573(9)
90.00
8.3456(17)
b/Å
10.630(2)
c/Å
11.977(2)
α/(°)
101.13(3)
β/(º)
91.88(3)
108.100(12)
90.00
γ/(º)
104.20(3)
3
V/Å
1007.1(3)
2881(3)
4
Z
4
－
Calculated density/(Mg•m )
3
1.288ꢀ
1.396
F(000)
416
1272
Crystal size/mm
h, k, l (min, max)
Completeness
0.37×0.32×0.24
(－10, 10); (－13, 13); (－15, 15)
99.4% (to è＝27.48°)
1.008
0.33×0.24×0.20
(－16, 16); (－18, 18); (－18, 18)
99.7% (to è＝27.44°)
1.096
2
GOF on F
a
Final R indices [I＞2σ(I)]
R ＝0.0612, wR ＝0.1413
R ＝0.0812, wR ＝0.2112
1
2
1
2
a
R indices (all data)
R ＝0.1377, wR ＝0.1732
1 2
R ＝0.1009, wR ＝0.2312
1
2
－
Largest diff. peak and hole/(e•Å )
3
0.163 and －0.164
1.026 and －0.919
a
2
2 2
2
1/2
1 o c o 2 o c o
R ＝Σ|F |－|F ||/ΣF |; wR ＝{Σw(F －F ) }/Σw(F )}} .
As shown in Figure 1, compound I is composed of
two same molecules (a and b) in each asymmetric unit.
Nearly all the atoms of each molecule are in the same
plane except H atoms. The mean deviation to the least
square plane of molecular a is 0.0407 and 0.0655 Å of
molecular b. The two molecules are almost coplanar
with dihedral angles of 5.9°. Intramolecular and inter-
molecular N—H…O hydrogen bonds lead to the forma-
tion of one dimensional chain (Figure 2).
Figure 2 Packing diagram for compound I, viewing along a
axis.
－
ether molecule and one PF
6
anion (Figure 3). Atom
F(3) shows somewhat disorder. The ether O atoms are
nearly coplanar: O(4), O(6) and O(8) are located above
the mean O-atom plane and O(3), O(5) and O(7) atoms
below the plane. Supramolecular rotators were assem＋-
bled between protonated aromatic amines (C10
14 3
H O N)
and 18-crown-6 via hydrogen-bonding interaction. The
+
—
NH3 moiety interacts with the six oxygen atoms of
crown ethers by six N—H…O hydrogen bonds (Table
). The distances between the N atom and the three O
Figure 1 Asymmetric unit for compound I.
2
The asymmetric unit of compound II contains one
substituted benzyl ammonium cation, one 18-crown-6
atoms above the mean O-atom plane in the crown ether
are short [2.843(3), 2.826(3), and 2.895(3) Å from
Chin. J. Chem. 2012, 30, 1957—1961
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1959

Wang, Sun & Xiong
COMMUNICATION
o
Table 2 Hydrogen bonded geometry, distances (Å) and angles ( ) in compounds I and II
D—H…A
d(D—H)
0.86
d(H…A)
2.63
d(D…A)
3.321(3)
3.125(3)
3.295(3)
3.170(3)
θ(D—H…A)
138.3
N(2)—H(2C)…O(4)#1
N(2)—H(2C)…O(5)#1
N(1)—H(1C)…O(1)
N(1)—H(1C)…O(2)
0.86
2.33
153.1
I
0.86
2.61
136.9
0.86
2.41
147.2
N(1)—H(1A)…O(3)
N(1)—H(1B)…O(4)
N(1)—H(1B)…O(5)
N(1)—H(1C)…O(6)
N(1)—H(1C)…O(7)
N(1)—H(1A)…O(8)
0.89
0.89
0.89
0.89
0.89
0.89
2.34
2.01
2.42
2.01
2.35
2.08
2.995(4)
2.843(3)
3.024(3)
2.826(4)
2.939(3)
2.895(3)
130.7
154.9
125.1
152.2
123.7
151.4
II
Symmetry code: #1: x＋1, y, z－1.
Table 3 Selected distances (Å) and angles (°) for compounds I
and II
I
II
O(1)—C(3)
1.381(3) P(1)—F(3)
1.410(3) P(1)—F(4)
1.324(3) P(1)—F(1)
1.448(3) P(1)—F(6)
1.381(3) P(1)—F(2)
1.411(3) P(1)—F(5)
1.334(3) O(9)—C(4)
1.448(3) O(9)—C(7)
1.200(3) O(1)—C(8)
1.192(3) O(2)—C(8)
1.388(3) O(2)—C(9)
1.399(3) O(3)—C(15)
1.383(3) O(6)—C(21)
1.544(3)
1.569(3)
1.574(3)
1.585(3)
1.595(2)
1.605(2)
1.374(3)
1.425(3)
1.200(4)
1.332(4)
1.479(4)
1.416(4)
1.442(5)
86.84(19)
88.5(3)
O(1)—C(6)
O(3)—C(7)
O(3)—C(8)
O(4)—C(12)
O(4)—C(15)
O(6)—C(16)
O(6)—C(17)
O(5)—C(16)
C(7)—O(2)
Figure 3 The interactions between the title ammonium com-
pound and a crown ether molecule in compound II. Dashed lines
indicate hydrogen bonds.
C(19)—N(2)
N(1)—C(20)
C(14)—C(20)
C(3)-O(1)-C(6)
C(7)-O(3)-C(8)
N(1) to O(4), O(6) and O(8), respectively], indicating
strong dipolar attractions. Comparatively below the
mean O-atom plane the distances are longer [2.995(4),
117.76(17) F(4)-P(1)-F(6)
116.30(19) F(3)-P(1)-F(1)
3
.024(3), 2.939(3) Å from N(1) to O(3), O(5) and O(7),
C(12)-O(4)-C(15) 117.44(18) F(6)-P(1)-F(2)
C(16)-O(6)-C(17) 115.69(19) F(3)-P(1)-F(4)
91.27(14)
95.7(3)
respectively]. The C—N bonds of the aromatic amines
cation are almost perpendicular to the mean plane of the
crown-ether O atoms. Atom N(1) of the aromatic
amines cation is 0.8405(25) Å out of the plane. The long
tail of the benzyl ammonium, unlike co-planer molecu-
lar of compound I, was bending along co-planer of O
atoms from crown ether.
C(3)-C(2)-C(1)
C(2)-C(3)-O(1)
O(1)-C(3)-C(4)
O(5)-C(16)-C(15)
O(6)-C(16)-C(15)
O(1)-C(6)-C(7)
O(4)-C(12)-C(13)
O(4)-C(12)-C(11)
121.0(2) O(9)-C(7)-C(8)
115.3(2) C(4)-O(9)-C(7)
125.5(2) C(8)-O(2)-C(9)
111.9(2)
117.8(2)
114.2(3)
126.1(2) C(16)-O(4)-C(17) 111.1(3)
109.7(2) C(12)-O(8)-C(13) 113.1(3)
107.60(18) O(5)-C(18)-C(17) 108.4(3)
115.4(2) O(4)-C(16)-C(15) 109.7(3)
125.7(2) O(7)-C(22)-C(21) 108.1(3)
－
The PF6 anions are present as counter-ions to the
＋
supramolecular [(C H O N•(18-crown-6))] . The P—
10
14
3
F bond lengths range from 1.544(3) Å to 1.605(2) Å.
The adjacent F-P-F bond angles range from 86.84(19)°
to 95.7(3)° (Table 3). Owing to the obvious differences
of the P—F distances and the F-P-F angles, the geome-
try of the anion could be regarded as a distorted octahe-
dral (Figure 4).
It is known that thermally actived molecular rotations
can arise striking dielectric response. Temperature-
1960
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 1957—1961

Synthesis and Structure of Supramolecular Compound with Ethyl 2-(4-Aminophenoxy)acetate
underway.
Conclusions
The title ammonium compound ethyl 2-(4-amino-
phenoxy)acetate and its crown ether-based supramo-
lecular structures have been synthesized successfully,
by introducing the organic ammonium and 18-crown-6
as the combination of cation. This approach allows us to
modulate the assembled molecule structures, and thus to
obtain many useful properties. Temperature-dependent
dielectric constants of compound II were also tested,
suggesting no phase transition during the measured
temperature range, probably because the molecular rota-
tion is frozen at the temperature.
Figure 4 Packing diagram in the ac plane for compound II.
Acknowledgement
dependent dielectric constant of compound II was tested
to systematically investigate the possibility of ferroelec-
tric phase transitions. As shown in Figure 5, the real part
This work was supported by the National Natural
Science Foundation of China (No. 21071030) and Jiang-
su Province (No. BK2010425).
(ε
1
) of dielectric constant of compound II at a frequency
of 1 MHz indicates that ε remains small change; it in-
creases smoothly from 1.5 to 3.5 within the measured
1
temperature range, together with the dielectric loss (ε /ε )
1
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Chin. J. Chem. 2012, 30, 1957—1961
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1961