Synthesis, crystal structure and piezoelectric property of noncentrosymmetric compound with betti base

Article abstract of DOI:10.1002/cjoc.201090261

The molten reaction of 2-naphthol, 2-hydroxybenzaldehyde and tetrahydropyrrole at about 120 °C yields 1-[(2-hydroxyphenyl)(pyrrolidin-1-yl)-methyl]naphthalen-2-ol, whose co-crystal (1) with 2-naphthol was characterized by X-ray single crystal diffraction,

Full text of DOI:10.1002/cjoc.201090261

FULL PAPER
Synthesis, Crystal Structure and Piezoelectric Property of
Noncentrosymmetric Compound with Betti Base†
Zhang, Yuan(张媛)
Ye, Qiong*(叶琼)
Han, Mengting(韩梦婷)
Xiong, Rengen*(熊仁根)
Ordered Matter Science Research Center, Southeast University, Nanjing, Jiangsu 211189, China
The molten reaction of 2-naphthol, 2-hydroxybenzaldehyde and tetrahydropyrrole at about 120 ℃ yields
1-[(2-hydroxyphenyl)(pyrrolidin-1-yl)-methyl]naphthalen-2-ol, whose co-crystal (1) with 2-naphthol was charac-
terized by X-ray single crystal diffraction, XRPD and IR. Compound 1 crystallizes in a noncentrosymmetric space
group (Fdd2) with unit cell dimensions of a＝2.9395(9) nm, b＝3.468(3) nm, c＝0.8013(8) nm, V＝8.170(13) nm3,
α＝β＝γ＝90.0° and Z＝8 [at 293(2) K]. The piezoelectric measurement result shows compound 1 is piezoelectri-
cally active material with d33 value of ca. 6.2 pC/N. Temperature- and frequency-dependent dielectric constant of
compound 1 were measured and showed no distinct dielectric anomaly, which suggest no phase transition within
the measured temperature range (100—410 K).
Keywords Betti base, noncentrosymmetric space group, piezoelectric behavior, dielectric constant
Introduction
interesting hydrogen-bonding interactions.20,21
Betti bases, which generally possess an asymmetric
carbon center or a chiral center, are a class of com-
pounds formed by the condensation reaction of corre-
sponding 2-naphthol, amine and aldehyde.22-25 Most of
Betti-type compounds obtained from racemic material
always crystallize in centrosymmetric space groups.26 In
our effort to prepare this class of compounds, we have
found that the combination of proper naphthol, amine
and aromatic aldehyde can give rise to crystallization of
acentric structures, which offers the prospect of inter-
esting physical properties above mentioned. Therefore,
Betti base will be a good candidate for piezoelectric
material. Herein, we report the synthesis, characteriza-
tion, piezoelectric and dielectric properties of a noncen-
trosymmetric 2-naphthol co-crystal 1 with Betti base
(1-[(2-hydroxyphenyl)(pyrrolidin-1-yl)methyl]naphthal-
en-2-ol) as shown in Eq. 1.
Supramolecular chemists have been interested in the
design and control of organic crystals packing arrange-
ments in crystal engineering field so as to search inter-
esting material with useful properties,1-5 such as ferro-
electric, nonlinear optical (especially second harmonic
generation) and piezoelectric activity. Piezoelectric ma-
terial, which can generate an electric field or electric
potential in response to applied mechanical strain, is
particularly desirable and has been widely used as
solid-state batteries, sensors, actuators and electrome-
chanical transducers.6 At present the most commonly
used piezoelectric material operating at high tempera-
ture is quartz (SiO2). Although it displays high resistiv-
ity and practically temperature-independent properties,
the piezoelectric coefficients are relatively low (d11＝
2.3 pC/N),7 which encourages us to search for the good
piezoelectric material with thermal stability and high
piezoelectric coefficients.
Piezoelectric property is only found in noncentro-
symmetric bulk material or polar crystals in crystallogra-
phy.8-14 Although controlling over the packing arrange-
ments of molecules through the employment of rational
design principles has taken progress in organic and inor-
ganic-organic hybrid material field,15-19 crystal engineer-
ing does not develop to the stage where a desired struc-
ture or crystal symmetry can be ensured. However, some
successful examples certified noncentrosymmetric crys-
tals can be reached by introducing chiral compound or
Experimental
Spectroscopic measurements
Infrared (IR) spectra of solid compound in KBr pel-
lets were recorded on a Shimadzu model IR-60 spec-
*
E-mail: yeqiong@seu.edu.cn; xiongrg@seu.edu.cn
Received June 9, 2010; revised and accepted August 27, 2010.
Project supported by the Natural Science Foundation of Jiangsu Province (No. BK2008286).
† Dedicated to the 60th Anniversary of Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Chin. J. Chem. 2010, 28, 1533— 1537
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Zhang et al.
FULL PAPER
trometer. Melting points were obtained with an electro-
thermal instrument without correction. The X-ray pow-
der diffraction data were obtained on a Rigaku X-ray
powder diffractionmeter D/MAX 2000/PC. The crystal
structures were determined by Rigaku SCX mini dif-
fractometer at room temperature. The piezoelectric co-
efficients were obtained from a ZJ-6A Quasi-Static
tester at room temperature. Dielectric constant and di-
electric loss measurements were performed on the sam-
ple of title crystal compound along c axis by using
automatic impedance TongHui2828 Analyzer.
piezoelectric coefficient dijk is a third rank tensor com-
ponent, the last suffixes jk denote six components of the
second-rank tensor. Couples of indices, 11, 12, 33, 23,
31 and 22 can be written as 1, 2, 3, 4, 5 and 6, so it
changes to Di＝dinσ permitting the matrix din expres-
n
sion of the piezoelectric coefficients to be given by
d11 d12 d13 d14 d15 d16
⎡
⎢
⎢
⎤
⎥
⎥
d21 d22 d23 d24 d25 d26
d31 d32 d33 d34 d35 d36
(2)
⎢
⎣
⎥
⎦
X-ray measurements
Dielectric constant measurements
X-ray diffraction data of compound 1 were collected
on a Rigaku SCX mini diffractionmeter using Mo Kα
radiation (λ＝0.71073 Å). The structure was solved by
direct methods with SHELXS-97 and refined by full
matrix least squares on F2 with SHELXL-97.27 All
non-hydrogen atoms were refined with anisotropic
thermal parameters. Hydrogen atoms were added theo-
retically and refined with riding model and fixed iso-
tropic thermal parameters. The CIF file of the structure
is deposited to CCDC database and has the CCDC
number 752595.
Dielectric constant and dielectric loss measurements
were performed on the crystal sample of compound 1
along c axis. The measuring AC voltage was 1 V. The
crystal with thickness of 0.620 mm and area of 16.290
mm2 is deposited with carbon conducting glue to use for
dielectric investigation. The samples have been placed
inside a dielectric cell whose capacitance were meas-
ured with different frequencies and temperatures. The
dielectric constant and dielectric loss have been calcu-
lated using Eqs. 3 and 4.
cd
Synthesis
ε'＝
(3)
(4)
Aε0
1-((2-hydroxyphenyl)(pyrrolidin-1-yl)methyl)na-
phthalen-2-ol A dry 100 mL flask was charged with
2-hydroxybenzaldehyde (10 mmol), 2-naphthol (10
mmol) and tetrahydropyrrole (10 mmol). The mixture
was stirred at 120 ℃ for 10 h and then 95% ethanol
(15 mL) was added. After heating under reflux for 1h,
the precipitate was filtrated out and washed with 95%
ethanol (5 mL) for 3 times and purified by recrystalliza-
tion from dichloromethane to give target product.＋Yield
68%, m.p. 182—184 ℃; MS (ESI) m/z: 320.2 (M ).
High quality colorless block single crystal 1 is ob-
tained by vaporing tetrahydrofuran solution with
2-naphthol (1 mmol) and Betti base 1-[(2-hydroxyph-
enyl)(pyrrolidin-1-yl)methyl]naphthalen-2-ol (2 mmol)
at room temperature for 1 week. IR (KBr) ν: 3410 (m)
3304 (m), 2956 (m), 2822.7 (m), 1609 (s), 1455.3 (m),
1377.4 (w), 1333.3 (m), 1087.5 (m), 819.6 (s), 753.7 (m)
ε''＝ε' tanδ
where d is the thickness, A is the area of the sample. The
frequency-dependent dielectric was measured with fre-
quency of 200 Hz to 1 MHz at room temperature, while
the temperature-dependent dielectric was measured
from 100 to 410 K.
Results and discussion
Molecule structures
Single crystals of compound 1 were obtained from
tetrahydrofuran solution with 2-naphthol (1 mmol) and
Betti
base
1-[(2-hydroxyphenyl)(pyrrolidin-1-yl)-
－1
methyl]naphthalen-2-ol (2 mmol) at room temperature
as described in experiment part. The molecule structure
and atom numbering of compound 1 are shown in Fig-
ure 1. The asymmetric unit of compound 1 consists of
one crystallographically independent Betti base and a
half 2-naphthol. The investigated compound crystallizes
in Fdd2 space group. IR, X-ray powder diffraction
(XRD) spectroscopy, and mass spectrometry confirmed
its formation. The bond lengths and angles are within
their normal ranges. Some important distances and an-
gles of hydrogen bonding interactions are listed in Table
1, which are comparable to the standard H-bond dis-
tance. The rings of naphthol A [C(1)—C(10)] and ben-
zene B [C(12)—C(17)] in Betti base molecule are pla-
nar and the dihedral angle between them is 74.18(5)°.
cm . Anal. calcd for C52H50N2O5 (1): C 79.77, H 6.44,
N 3.58; found C 79.69, H 6.46, N 3.61. Crystal data for
1: C52H50N2O5, Mr＝782.94, orthorhombic, Fdd2, a＝
2.9395(9) nm, b＝3.468(3) nm, c＝0.8013(8) nm, V＝
8.170(13) nm3, α＝β＝γ＝90.0° and Z＝8 [at 293(2) K],
－3
Dc＝1.273 Mg•m , R1＝0.0913, wR2＝0.2123, T＝
－1
293(2) K, µ＝0.81 cm .
Piezoelectric constant measurements
The direct piezoelectric coefficient can be measured
by the equation of Di＝dijkσ , where Di is the generated
jk
piezoelectric charge, σ is the applied stress. To deter-
jk
mine the piezoelectric coefficient, dijk, the generated
piezoelectric charge Di must be measured as external
stress while σ is applied to the sample. Although the
jk
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Chin. J. Chem. 2010, 28, 1533— 1537

Synthesis, Crystal Structure and Piezoelectric Property of Noncentrosymmetric Compound
Figure 1 Perspective structure of the title compound.
Table 1 Geometrical parameters of hydrogen bonds in com-
pound 1 [distances in Å and angles in (°)]
Figure 2 (a) Projection of compound 1, hydrogen atoms are
omitted for clarity. 2-Naphthol filled the annulus space con-
structed by four neighboring Betti base molecules to form chan-
nel structure along c axis. (b) A view of the 1D chain constructed
by Betti base in compound 1.
D—H…A
D—H H…A ∠DHA D…A
O(1)—H(1A)…N(1)a
O(2)—H(2A)…O(1)a
C(11)—H(11A)…O(2)a
C(13)—H(13A)…O(1)a
C(26)—H(26A)…O(2)b
a x, y, z＋1; b x＋1, y, z.
0.9604 1.7441 138.14 2.542
0.9599 1.6412 154.22
2540
0.9787 2.2800 109.56 2.766
0.9301 2.5594 135.75 3.290
0.9306 2.4890 154.73 3.354
purity of 1 (Figure 3). The little difference in reflection
intensities between the simulated and experimental pat-
terns was due to the variation in preferred orientation
for the powder sample during collection of the experi-
mental XRD data.
The packing structure of compound 1 can be well
understood by separated to Betti base and 2-naphthol
parts. For Betti base part, intramolecular [O(1) —
H(1A)…N(1)] and intermolecular [O(2)—H(2A)…O(1)]
hydrogen bonding interactions among nitrogen atoms of
the tetrahydropyrrole, oxygen atoms of 2-naphthole and
2-hydroxybenzne rings result in the formation of a 1D
H-bond donor-acceptor chain along c direction as
shown in Figure 2b. For the arrangement of Betti base
and 2-naphthol molecules in three-dimensional space,
four Betti base molecules surround one 2-naphthol cen-
ter to form an annulus coordination environment. That
is, four neighboring Betti base molecules on ab plane
form a bowl-like structure and the 2-naphthole molecule
occupies the bowl space. All of these bowls filled with
2-naphthole pack together to extend along c axis as
shown in Figure 2a. Owing to the interpenetration of
Betti base molecules, two closest 2-naphthol molecules
are far away from each other. Almost no π-π interac-
tions existed between two closed 2-naphthol molecules,
and the distance between two closest 2-naphthol rings is
8.0254(0.0113) Å. It needs to note that 2-naphthol
molecule shows orientation disordered and the dihedral
angle of naphthol rings separately from Betti base and
2-naphthol molecule is 75.67(0.45) Å. As a result, the
asymmetric structure and chiral center of Betti base as
well as strong intra- and intermolecular hydrogen bond-
ing interactions between neighboring Betti base lead to
the acentric crystallization of compound 1.
Figure 3 Powder X-ray diffraction pattern of compound 1,
where the lower line is single crystal diffraction simulated pat-
tern.
Piezoelectric result
The piezoelectric effect is strongly related to the
crystal symmetry. Except the noncentrosymmetric point
groups O(432) which do not exhibit a piezoelectric ef-
fect, nearly all other crystals belonging to the remaining
20 non-centrosymmetric point groups exhibit the piezo-
electric effect.28 Compound 1 crystallizes in a chiral
space group Fdd2. The space groups Fdd2 is associated
with the polar point group C2v, which belongs to 20
non-centrosymmetric point groups, so compound 1
should exhibit the piezoelectric effect in theory. Ex-
perimental results indicate that it does display piezo-
electric behavior.
XRPD patterns of compound 1
Compound 1 was characterized by X-ray powder
diffraction (XRPD) at room temperature. The XRPD
pattern of 1 matches very well with the structural simu-
lation of its single crystal, which indicated the phase
Material from the symmetry class C2v point group
has 5 mutually independent non-zero piezoelectric coef-
ficients, the matrix in expression of the piezoelectric
Chin. J. Chem. 2010, 28, 1533— 1537
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Zhang et al.
FULL PAPER
coefficients is given by Eq. 5
0
0
0
0
0
0
0
d24
0
d15
0
0
0
0
⎡
⎢
⎢
⎤
⎥
⎥
(5)
⎢
⎣
⎥
⎦
d31 d32 d33
0
We preliminarily studied piezoelectric coefficient d33
of single crystal sample of 1. The piezoelectric coeffi-
cient d33 can be obtained from ZJ-6A Quasi-Static tester.
At room temperature, the measurement result of single
crystal sample indicates that 1 is piezoelectrically active
material with a d33 value of approximately 6.2 pC/N,
obviously it is much larger than that of quartz (2.3 pC/N)
but significantly smaller than that of practically useful
BaTiO3 (300—2500 pC/N) at room temperature.29 The
result should provide a basis for future piezoelectric
device design.
Figure 5 The temperature-dependent dielectric constant along c
axis at 1 MHz by using a single crystal of compound 1.
The temperature dependence of the dielectric con-
stant (real part, ε') as estimated from the gradient at a
frequency of 1 MHz indicates that dielectric constant ε'
shows small change. It increases smoothly from 4.5 to
8.3 for 1 within the measured temperature range, which
could be owing to the low dielectric loss (ε'') behavior.
Meanwhile, such a feature would support the presence
of a space charge polarization relaxation process rather
than a temperature process. The dielectric constant of
compound 1 as a function of temperature indicates that
the permittivity is basically temperature-independent
and no dielectric anomaly observed, suggesting that this
compound should be not real ferroelectric or there may
be no distinct phase transition occurred within the
measured temperature range.
Dielectric result
Compound 1 is fortunate to crystallize in one of po-
lar point groups, which are necessary for ferroelectric
crystals. Dielectric properties are investigated to check
whether compound 1 is ferroelectric or not, because
generally ferroelectric crystals show ferroelectric-
paraelectric phase transition and dielectric anomaly.
Compound 1 crystallizes in Fdd2, so we measured the
dielectric constant along c axis, which is polar axis and
perpendicular to 1D H-bond interaction chain. Fre-
quency- and temperature-dependent dielectric meas-
urement results are shown in Figures 4 and 5. The fre-
quency-dependent dielectric was measured with fre-
quency of 200 Hz to 1 MHz at room temperature, while
the temperature-dependent dielectric was measured
from 100 to 410 K. From Figure 4, the fre-
quency-dependent dielectric measurement results show
that the dielectric constant decreases smoothly with in-
creasing frequency and attains saturation at higher fre-
quencies.
Conclusions
Compound 1 crystallizes in an acentric space group
Fdd2. Experimental results indicate that it is piezoelec-
trically active compound. Dielectric measurements re-
veal that the dielectric constant of the compound 1 in-
creases with temperature increasing and decreases with
frequency increasing. In contrast to piezoelectric and
SHG-active materials which are noncentrosymmetric,
ferroelectric behavior is limited to crystals that belong
to one of the 10 polar point groups (C1, C2, Cs, C2v, C4,
C4v, C3, C3v, C6, C6v). The product has a polar point
group and accordingly has the potential to display ferro-
electric behavior. However, compound 1 is not a real
ferroelectric compound or there may be no distinct
phase transition occurred within the measured tempera-
ture range, because its dielectric constant is almost
temperature-independent and no dielectric anomaly ob-
served. The present results provide strong encourage-
ment that crystallization of racemic compounds has the
potential to yield noncentrosymmetric products by in-
troduction of chiral or asymmetric compound and inter-
esting H-bond interactions. Thus it opens a new avenue
to explore functional molecule-based materials.
Figure 4 The frequency-dependent dielectric constant at fre-
quency range of 200 Hz to 1 MHz at ca. 20.0 ℃ for compound
1.
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Synthesis, Crystal Structure and Piezoelectric Property of Noncentrosymmetric Compound
15 Xiong, R.-G.; Xue, X.; Zhao, H.; You, X.-Z.; Abrahams, B.
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