Columnar metallomesogens derived from unsymmetrical pyrazoles

Article abstract of DOI:10.1016/j.tet.2008.11.080

The synthesis and mesomorphism for two series of unsymmetrical pyrazoles and their nickel(II) complexes were described. This is the first example of nickel complexes exhibiting columnar phase. The derivatives with two alkoxy chains exhibited smectic A or

Full text of DOI:10.1016/j.tet.2008.11.080

Tetrahedron 65 (2009) 1130–1139
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Columnar metallomesogens derived from unsymmetrical pyrazoles
Shih-Yu Chou a, Chun-Jung Chen a, Shao-Ling Tsai a, Hwo-Shuenn Sheu b,
,
Gene-Hsiang Lee c, Chung K. Lai a
*
a Department of Chemistry, National Central University, Chung-Li 32054, Taiwan, ROC
b National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan, ROC
c Instrumentation Center, National Taiwan University, Taipei 10660, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and mesomorphism for two series of unsymmetrical pyrazoles and their nickel(II) com-
plexes were described. This is the first example of nickel complexes exhibiting columnar phase. The
derivatives with two alkoxy chains exhibited smectic A or smectic C phases; however, all derivatives with
four alkoxy chains formed hexagonal columnar phases. In contrast, all nickel(II) complexes 1a formed
hexagonal columnar phases. The crystal and molecular structures of 1-(4-propyloxyphenyl)-2-(3-(4-
propyloxyphenyl)-1H-pyrazol-5-yl)ethanone were determined, and it crystallizes in the triclinic space
group P-1. The overall molecular shape is considered as rod-shaped. The pyrazole and one phenyl ring
were coplanar, however, they were not coplanar with other phenyl ring by a dihedral angle of ca. 66.2ꢀ. A
Received 25 September 2008
Received in revised form 18 November 2008
Accepted 26 November 2008
Available online 30 November 2008
dimeric structure formed by an intermolecular H-bond (2.11 Å) and a weak p–p interaction (3.51 Å) was
observed, which was probably attributed to the formation of the mesophase. The XRD experiments
confirmed their structures of the mesophases.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
bioinorganic chemistry.3,4 They are electron-deficient or electron
acceptors, therefore, a local dipole of donor-to-acceptor (D–A) in-
The interest in metallomesogens1 or metal-containing liquid
crystals (MCLCs) has been extensively expanded during past years.
Modern synthetic knowledge allows researchers to access tailor-
made materials with predictable properties, particularly in the
field of liquid crystalline materials. More and more examples1,2
with particular structures and/or novel physical properties were
obtained by incorporation of a metal ion or metal ions into an
organic fragment. The coordination geometry of the central ion is
often important in determining the mesogenic materials since it
often alters the overall molecular shape. Metal ions, for example,
d9-Cu2þ, d8-Ni2þ, or d1-VO2þ with square-planar coordination (SP)
were used the most; however, metal ions with tetrahedral (Td) or
octahedral2 (Oh) coordination were relatively lesser. In addition, use
teraction was easily induced within molecules or between mole-
cules. Interest in such systems stems from their diverse structures
and known chemistry. Two nitrogen atoms on the pyrazole ring are
often capable of binding to metal ions (i.e., M1þ and M2þ). Two
bonding modes are feasible. One N atom can donate an electron
lone pair to metal ions, leaving the pyrazolic –NH as a free group,
and this type of bonding is particularly efficient with M2þ ions. On
the other hand, the other N atom can be deprotonated (pyrazolate
anion) with a base, binding to M1þ ions. This type of pyrazole anion,
important as a bichelating ligand, was often applied to generate
complexes with an exo-bidentate structure.4a,5 Most of structures
with divalent metal ions formed were of ML2 and metal ions used
were dominantly first-row transition-metal ions. However, trinu-
clear pyrazolate complexes formed by monovalent coinage metal,6
such as Cu1þ, Ag1þ, and Au1þ, were also prepared. Some of neutral
metal complexes7 having fluorinated ligands are of particular
interest as emitting materials for molecular light-emitting devices
(MOLEDs). Fluorination facilitated thin-film fabrication process and
also the presence of a closed-shell transition metal should enhance
the phosphorescence efficiency. Some copper(I) complexes with
trinuclear8 [Cu(dmpz)]3 or tetranuclear9 structures [Cu(dppz)]4
were found to be useful catalysts on organic reactions.
of paramagnetic (Cu2þ, Mn2þ, and VO2þ) or diamagnetic ions (Cu1þ
,
Pd1þ, and Rh1þ) might alter the magnetic behavior of the metal-
lomesogenic materials. Metallomesogens obtained often have
properties quite distinct from their precursors, such as meso-
morphism, color, magnetic behavior, and other physical properties.
Metallomesogens might be generated from non-mesogenic
precursors, and vice versa. Pyrazoles,3 cataloged as heterocyclic
ligands, have been widely applied in inorganic, organometallic, and
By contrast, known examples of mesogenic pyrazoles and
derived metallomesogens10 were relatively rare. Most reported
structures were mononuclear, whereas, a few examples of dinuclear
* Corresponding author. Tel.: þ886 3 4259207; fax: þ886 3 4277972.
E-mail address: cklai@cc.ncu.edu.tw (C.K. Lai).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.11.080

S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
1131
and trinuclear complexes were also known. More examples were
2. Results and discussions
2.1. Synthesis
prepared and studied since the first example containing 3,5-di-
substituted phenylpyrazole11 exhibiting SmA and SmC phases was
reported in 1992. Among them, rhodium(I) and palladium(II) are
used the most to generate the metallomesogens. These two metal
ions were all d8 electronic configurations and square-planar pre-
ferred in coordination geometry. A nonmesogenic ZnL2Cl2 (L¼3,5-
bis(p-decyloyphenyl)pyrazole)12 was reported, and the mesophase
was improved by a structural modification of ligand.13 Crystallo-
graphic data on other similar pyrazole related zinc complexes14
showed that zinc centers were all tetrahedral. Metal center with
a tetrahedral geometry resulted in an unfavorable angle between
central cores, precluding the formation of mesomorphism. The zinc
complex also exhibited fluorescence properties.13 A few square-
planar Rh1þ complexes, such as [RhCl(CO)2(HpzR)],15a [Rh-
The synthetic pathways followed to prepare compounds 1–4 are
summarized in Scheme 1. All precursors 3 were prepared according
to the literature procedures19a,20 using cross-Claisen condensation
reactions. The further condensation reactions of 1,3,5-triketones
and hydrazine monohydrate in refluxing absolute ethanol pro-
duced the pyrazole derivatives 2 as off-white solids with a yield of
ca. 65–84%. All compounds were characterized by 1H, 13C NMR
spectroscopy, mass spectroscopy, and elemental analysis. The
solubility in CDCl3 for some of pyrazole derivatives was poor, so
their 13C NMR spectra were not possibly obtained. Three tautomers
for pyrazoles 2 are structurally possible. On the 1H NMR spectra,
(
m
-pzR)(CO)2]2,15b [Rh(
m
-pzPP)(COD)]216a and [Rh(
m
-pzbp)(COD)]2,16a
only two characteristic peaks at d 6.37–6.61 and d 4.29–4.57,
assigned to pyrazole-H (–CHC]N) and keto-H (–CH2CO) were
observed, however, the pyrazole-H (–NH) often occurred at ca.
and [Rh(Cl(NBD)(HpzR))]16b containing substituted pyrazoles
with long-chained substituents were found to be mesogenic.
Palladium(II) fragments, PdCl217a–c and Pd(
h
3-C3H5)þ17d,e were also
d
11.60–12.60 was not observed. In contrast, two other character-
istic peaks at 5.80 and 6.20 assigned to olefinic methane-H
(–CH]C) of 1,3,5-triketones 3 were also disappeared. On the other
hand, the observation of one peak at ca.
193.6 on 13C NMR spectra
used to generate metallomesogens, [PdCl2(pzRpy)] and [Pd(h3
-
-
d
d
C3H5)(HpzR)2]þBFꢁ4 . Example of bimetallomesogens, [Pd(h3
18
C3H5)(
m
-pzR)]2 containing bridged 3,5-disubstituted pyrazolate
d
ligands was reported. Most of mesogenic pyrazoles and their related
metallomesogens exhibited smectic phases. However, a few exam-
ples of pyrazole-derived metallomesogens formed by mononuclear-
Cu1þ, Rh1þ, and trinuclear-Au1þ complexes19 exhibiting columnar
phases were also prepared and studied.
assigned to keto –CH2C]O confirmed the isomer 2 as the most
stable structure among three isomers. Also a persistent solution in
CDCl3 did not show an apparent change on 1H NMR spectrum. The
further reactions of pyrazole 2a with NiCl2 in refluxing C2H5OH/THF
produced the nickel complexes 1a. The structure of nickel
complexes was tentatively proposed as drawn due to a lack of
single crystallographic analysis. Nickel atom was coordinated as
square-planar geometry to two nitrogen atoms with lone electron
pairs, leaving the other two nitrogen atoms as free amine-HH. The
similar reactions with CuCl2 to prepare copper complexes were not
successful for an unknown reason.
In this work, we describe herein the preparation and mesomor-
phic studies of two new series of heterocyclic pyrazoles 2a,2b and
their nickel complexes 1a. These compounds showed a strong chain
density dependence on the formation of the mesomorphic proper-
ties. All derivatives 2b with two alkoxy chains exhibited smectic A or
smectic C phase, however, other series of derivatives 2a with four
alkoxy chains formed hexagonal columnar phases (Colh). In contrast,
all nickel(II) complexes 1a displayed hexagonal columnar phases.
Similar compounds, 3,5-di(4-n-alkoxyphenyl)pyrazoles 5a have
been previously prepared and also their mesomorphic properties
studied. TheyallexhibitedenantiotropicsmecticA, Cor/andXphases
over a wide range of temperatures. Crystallographic data indicated
that the H-bonding was probably attributed to the formation in such
systems. On the other hand, a series of compounds 4 with a similar
structure was also prepared in order to understand the effect of
H-bonding in this type of pyrazole ligands. A dimeric structure,
supported by crystallographic data formed by an intermolecular
H-bondingwasalsoobserved,whichmightfacilitatetheformationof
themesophases. Thisis thefirstexample ofnickelcomplexes derived
from pyrazoles exhibiting hexagonal columnar (Colh) phases.
2.2. The X-ray single crystallographic data
A single crystals of the non-mesogenic pyrazole 2b (n¼3) suit-
able for crystallographic analysis were obtained by slow vapor-
ization from CH3Cl at room temperature and their structures
resolved. Figure 1 shows the molecular structure with the atomic
numbering schemes. Table 1 lists their crystallographic and struc-
tural refinement data for the molecule. The overall molecular shape
of crystal was considered as a linear structure with a length of ca.
21.15 Å. The central pyrazole ring and phenyl rings were coplanar;
however, they were not coplanar to the other phenyl ring. A di-
hedral angle of 66.2ꢀ was measured. Unsurprisingly, an in-
termolecular H-bond between O4 and H2 atoms was observed, and
the distance was measured by ca. 2.11 Å. The distance between N1
and N2 atoms (see Table 2) was 1.356 Å, similar to other known
pyrazole. The bond length of 1.218 Å (C5–O1 atom) and its bond
angle of 121.3ꢀ (:C1–C5–C4) supported the structure 2 (not 20 or
200) as the most stable tautomers. The carbonyl group was existent
with a free C]O moiety. In the unit cell, molecules were packed
with a head-to-head arrangement. Such dimeric structure facili-
tated a better packing both in the solid or/and the liquid crystal
state. However, intermolecular H-bonding was not observed. On
RO
RO
OR
OR
N
NH
O
Cl Ni Cl
O
HN
N
RO
RO
OR
OR
other hand, a
in Figure 2.
p–p interaction of 3.51 Å was also observed, as shown
1a R = CnH2n+1; n = 12, 14, 16
RO
OR
X
2.3. Mesomorphic properties
X
The mesomorphic behavior of compounds 1–4 was studied by
differential scanning calorimetry (DSC), polarizing optical micros-
copy (POM), and powder X-ray diffractometry (XRD). The phase
transitions and thermodynamic data for compounds 1–4 are
N
NH
5a; X = H
5b; X = OC14H29

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S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
O
X
OR
H2n+1CnO
X = H; R = CH3
X = OCnH2n+1; R = C2H5
a
O
OH OH
N
O
O
X
X
c
X
X
H2n+1CnO
OCnH2n+1
OCnH2n+1
H2n+1CnO
3a X = OCnH2n+1
3b X = H
4 X = H; n = 6, 7, 8, 12
H2n+1CnO
X
OCnH2n+1
X
b
N
NH
O
N
NH O
d
X
X
Cl Ni Cl
O
HN
N
H2n+1CnO
OCnH2n+1
X
X
H2n+1CnO
OCnH2n+1
2a X = OCnH2n+1; n = 6, 8, 10, 12, 14, 16
2b X = H; n = 6, 8, 10, 12, 14, 16
1a X = OCnH2n+1; n = 12, 14, 16
Scheme 1. Reactions and conditions: (a) Acetone (0.5 equiv), NaH (6.0 equiv), refluxing in dimethoxyethane, 48 h, 72–89%; (b) N2H4$H2O (10.0 equiv), refluxing in ethanol, 12 h, 65–
84%. (c) NH2OH$HCl (1.1 equiv), refluxing in ethanol, 12 h, 70–76%; (d) NiCl2 (0.55 equiv), refluxing in ethanol/THF, 24 h, 92-95%.
N
NH
O
HN
N
OH
N
NH OH
2
2'
2''
Figure 1. An ORTEP plot for compound 2b (n¼3) with the numbering scheme, and the thermal ellipsoids of the non-hydrogen atoms are drawn at the 50% probability level.
summarized in Tables 3 and 4. The mesomorphic results indicated
that the formation of mesophases in pyrazolate compounds 2 was
strongly dependent of alkoxy chain density. All compounds 2b with
two alkoxy chains displayed enantiotropic smectic A or smectic C
phase; however, all compounds 2a with four alkoxy chains formed
enantiotropic columnar phases. Among compounds 2b only de-
rivative with shorter chains (n¼6) exhibited SmA phase and all
other compounds with longer chains (n¼8, 10, 12, 14, 16) formed
SmC phase. A slight decrease both in the melting temperatures and
clearing temperatures accompanying an increase in the alkoxy
chain length was observed. However, the temperature range of
SmA or SmC phase was between 13.7 ꢀC (n¼6) and 33.3 ꢀC (n¼10)
on heating process. The pyrazolate derivative n¼10 has the widest
temperature range of SmC phase. Under the optical microscope,
a typical fan-shaped texture with homeotropic domain for SmA or
without homeotropic area for SmC phases, respectively, was
observed upon slow cooling from their isotropics, as shown in
Figure 3. A series of pyrazoles 5a with similar structures was pre-
viously prepared and studied. These compounds exhibited N, SmA,
SmC ,or/and SmX phases depending the carbon chain lengths.
However, all compounds 2b, particularly with the lower carbon
chain length have both lower clearing temperatures, i.e., 198 ꢀC (5a,
n¼6)>165 ꢀC (2b, n¼6) and narrower temperature range, i.e.,
39.5 ꢀC (5a, n¼6)>11.3 ꢀC (2b, n¼6) of mesophases than those of
compound 5a. This lowering in clearing temperatures might be
attributed to the ketonate group (–CH2C]O) group next to the
pyrazolate ring in 2b. The ketonate –CH2C]O group was found not
coplanar to the pyrazolate ring (i.e., see discussion in single crystal
data), which tended to reduce the intermolecular interaction both
in crystal and mesogenic states.
The mesomorphic behavior was distinctive when the total alk-
oxy chains’ numbers increased to four in compound 2a. Under the

S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
1133
Table 1
Table 3
Crystal and refinement data for compound 2b (n¼3)
The phase transitionsa and temperatures of compounds 2a,2b
Compound
Empirical formula
Formula weight
T/K
2b (n¼3)
C23H26N2O3
378.46
Compound
151.3 (32.2)
118.8 (29.2)
165.0 (9.69)
160.1 (10.4)
Cr
Cr
SmA
SmC
I
I
2b; n ¼ 6
150(2)
Crystal system
Space group
a/Å
b/Å
c/Å
Triclinic
P-1
142.7 (42.0)
112.7 (39.0)
131.7 (60.4)
109.0 (60.4)
132.2 (60.7)
109.5 (55.6)
134.9 (57.8)
111.5 (57.3)
133.0 (88.6)
116.0 (88.4)
68.1b
167.6 (11.9)
163.4 (11.5)
165.1 (13.2)
160.7 (12.1)
163.0 (11.3)
157.8 (10.9)
159.0 (9.34)
151.0 (7.74)
152.5 (12.5)
148.1 (11.7)
8
7.6828(5)
11.4540(7)
22.2399(14)
90.630(2)
97.405(2)
94.267(2)
1935.0(2)
4
10
Cr
Cr
SmC
SmC
I
I
ꢀ
ꢀ
a
/
b
/
ꢀ
/
g
12
U/Å3
Z
F(000)
808
1.299
Cr
Cr
Cr
SmC
SmC
Colh
I
I
I
14
Dc/Mg mꢁ3
Crystal size/mm3
Range for data collection/ꢀ
Reflections collected
Data, restraints, parameters
Independent reflections
Final R1, wR2
0.40ꢂ0.32ꢂ0.05
0.92–27.50
25,735
8854/0/507
8854 [R(int)¼0.0508]
0.0728, 0.1614
16
68.8(2.65)
64.2 (2.63)
2a; n ¼ 6
45.5b
63.3b
52.3b
65.2b
54.1b
62.5b
79.9 (2.91)
74.8 (2.81)
8
Cr
Colh
I
Table 2
Selected bond distances [Å] and angle [ꢀ] for compound 2b (n¼3)
91.3 (3.04)
86.1 (2.95)
10
Cr
Cr
Colh
Colh
I
I
Bond distances
N(1)–N(2)
N(1)–C(1)
C(2)–C(3)
C(1)–C(12)
C(4)–C(5)
1.356(3)
1.331(3)
1.364(3)
1.469(3)
1.515(3)
N(2)–C(3)
C(1)–C(2)
O(1)–C(5)
C(3)–C(4)
1.348(3)
1.407(3)
1.218(3)
1.499(3)
92.3(3.13)
89.0(3.12)
89.4(3.31)
12
14
43.9b
45.2 (11.2)
Cr
Cr
Colh
Colh
I
I
Bond angles
86.1(3.16)
82.4 (6.30)
28.5 (28.3)
62.7 (44.3)
C(1)–N(1)–N(2)
N(1)–C(1)–C(2)
C(3)–C(2)–C(1)
N(2)–C(3)–C(4)
C(3)–C(4)–C(5)
O(1)-C(5)-C(4)
104.15(18)
111.10(19)
105.6(2)
122.2(2)
114.49(18)
121.3(2)
C(3)–N(2)–N(1)
N(1)–C(1)–C(12)
N(2)–C(3)–C(2)
C(2)–C(3)–C(4)
O(1)–C(5)–C(6)
C(6)–C(5)–C(4)
112.92(18)
120.30(19)
106.21(19)
131.6(2)
120.9(2)
117.81(19)
16
79.7 (1.80)
47.4 (67.4)
a
n¼The carbon numbers of alkoxy chains, Cr¼crystal, SmA¼smectic A,
SmC¼smectic C, Colh¼hexagonal columnar phase, I¼isotropics.
b
Obtained by optical microscope.
Symmetry transformations used to generate equivalent atoms.
Table 4
The phase transitionsa and temperatures of compounds 1a and 4
Compound
116.2 (4.20)
112.8 (4.57)
108.0 (1.30)
104.2 (1.56)
103.8 (40.0)
60.2 (18.9)
SmA
I
4; n ¼ 6
SmC
Cr
118.9 (9.93)
114.5 (9.02)
85.1 (22.7)
53.8 (18.5)
Cr
SmC
I
7
124.2 (12.2)
119.5 (11.7)
82.2 (23.4)
52.8 (19.3)
8
Cr
Cr
SmC
SmC
I
I
133.9 (14.6)
129.3 (14.2)
79.1 (23.3)
69.6 (32.0)
12
Figure 2. A side view of the molecular packings in the unit cell was shown. The
molecular length (C46–C043¼ca. 21.25 Å), intermolecular H-bonding (ca. 2.110 Å), and
108.3b
78.0b
117.1 (8.37)
113.9 (7.37)
a
p–p interaction (ca. 3.51 Å) were shown.
1a; n ¼ 12
Cr
Cr
Colh
Colh
I
I
115.2b
89.1b
132.8 (4.54)
129.1 (4.31)
optical polarized microscope, they melted into viscous phases upon
slow heating, and a typical pseudo-focal conics or fan-shaped
texture (shown in Fig. 4) with homeotropic behavior was observed
on cooling from their isotropic states. This type of texture was
characteristic of hexagonal columnar (Colh) phases. On the DSC
analysis, these compounds all exhibited two enantiotropic transi-
tions, crystal-to-columnar (Cr/Colh) and columnar-to-isotropic
(Colh/I). The clearing temperature slightly increased with side
14
110.3b
87.6b
128.4 (5.85)
125.3 (5.10)
16
Cr
Colh
I
a
n¼The carbon numbers of alkoxy chains, Cr¼crystal, SmA¼smectic A,
SmC¼smectic C, Colh¼hexagonal columnar phase, I¼isotropics.
b
Obtained by optical microscope.

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S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
Figure 4. Optical textures observed by compounds 2a. Top plate: Colh phase (n¼12) at
86.0 ꢀC, and bottom plate: Colh phase (n¼6) at 65.0 ꢀC.
Figure 3. Optical textures observed by compounds 2b. Top plate: SmC phase (n¼12) at
150 ꢀC and bottom plate: SmA phase (n¼6) at 155 ꢀC.
chain length of derivatives n¼6, 8, 10, 12 and then decreased with
derivatives n¼14, 16. The temperature range of the columnar
12) exhibited SmC phase only (Fig. 5). The overall molecular shapes
of compounds 4 are considered as rod-shaped, slightly bent struc-
tures with a bending angel equal to 154–165ꢀ, similar to those of
pyrazoles. The melting temperature decreased with carbon chain
length, i.e., Tm¼103.8 ꢀC (n¼6) >Tm¼79.1 ꢀC (n¼12), however, the
clearing temperature increased with carbon chain length, i.e.,
Tcl¼116.2 ꢀC (n¼6)<Tcle¼133.9 ꢀC (n¼12). The clearing temperature
was slightly lower by ca. 29.1 ꢀC (n¼12) to 48.8 ꢀC (n¼6) than those
of compound 2b, which might be attributed to the absence of
H-bonding. On the other hand, the temperature range of mesophase
in compounds 4 was slightly wider than those in compounds 2b.
Upon coordinated to Ni2þ ion, a more discotic molecule result-
ing from nickel complexes 1a (n¼12, 14, 16) were formed. The
formation of columnar phases was often found to depend crucially
on the side chain density. On the other hand, the side chain density
required for the columnar phases was strongly dependent on the
size or the flexibility of the core center, i.e., the larger size or the
more rigid is the core group, and more side chain density is often
needed. The overall molecular shape of compounds 1a is consid-
ered as discotic or round, and eight alkoxy chains appended were
enough to form a stable columnar phase. Thermal data were shown
in Table 2. All derivatives formed enantiotropic hexagonal co-
lumnar phases (Colh), and two typical transitions of crystal-to-co-
lumnar and columnar-to-isotropic were observed on DSC analysis.
The melting temperatures were only observed by optical micro-
scope. On the other hand, all clearing temperatures were highly
phases also increased with carbon number, i.e.,
D
T¼0.7 ꢀC
(n¼6)<16.6 ꢀC (n¼8)<26.1 ꢀC (n¼10)<29.8 ꢀC (n¼12)<44.2 ꢀC
(n¼14), and reached to
D
Tmax¼44.2 ꢀC for derivative n¼14. In-
terestingly, the overall molecular shape of compounds 2a was not
round or a disc-shaped. On the other hand, the overall molecular
shape of a monomeric molecule was in fact considered as half-disc-
shaped. Most of columnar phases reported were formed by mole-
cules with six or eight side chains. A complementary structure was
proposed to be made by two correlated monomeric molecules. Two
combined half-disc-shaped molecules gave a total number of eight
alkoxy side chains, which were then enough to form a columnar
phase. The formation of columnar phases in compounds 2a
was probably attributed to the dimeric structure formed via
intermolecular H-bonding. The dimeric structure formed by
H-bonding was observed in other pyrazolate system.
In order to understand the effect of possible H-bonding on the
formation of mesophase in such calamite pyrazolate derivatives,
a series of heterocyclic isoxazoles 4 was also prepared and meso-
morphic properties compared. All compounds 4 are structurally
similar to compounds 2; however, H-bonding is not possibly in-
duced in compounds 4. Thermal data indicated that compounds 4
were all mesogenic. The derivative with shorter alkoxy chains (n¼6)
formed SmA at higher temperature and SmC phase at lower tem-
perature, and all other derivatives with longer side chains (n¼7, 8,

S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
1135
Figure 6. Optical textures observed by compounds 1a. Top plate: Colh phase (n¼14) at
125.0 ꢀC and bottom plate: Colh phase (n¼12) at 110.0 ꢀC.
Figure 5. Optical textures observed by compounds 4. Top plate: SmC phase (n¼12) at
100.0 ꢀC and bottom plate: SmC phase (n¼6) at 100.0 ꢀC.
higher than those their ligand derivatives 2a by 24.0 ꢀC (n¼12) to
46.0 ꢀC (n¼16) due to a larger and more rigid core. The temperature
range of columnar phases was slightly narrower than those of their
homologues 2a. The Colh phase was also characterized by optical
polarized microscope. A typically pseudo-focal-conic texture (see
Fig. 6) with linear birefringent defects on slowly cooling from the
isotropic liquid was clearly observed. This observed texture also
accompanied by a large area of homeotropic domain is often
characteristic for hexagonal columnar phases. In contrast to com-
pound 2a, the columns in hexagonal phases in compounds 1a were
formed by stacking single molecule (monomeric structure, shown
in Fig. 7). The powder XRD results confirmed the structure of the
mesophase as Colh phase. For example, compounds 2a (n¼12) and
1a (n¼12) both have a similar lattice constant in magnitude of
34.32 Å and 33.82 Å, respectively. The lattice constants were quite
consistent with proposed model of a monomeric and dimeric
structure formed in compounds 1a and 2a, respectively.
diffraction peak was stronger for SmC phase than that for SmA
phase. For example, the derivative n¼6 gave a diffraction at d 28.7 Å
at 130 ꢀC, in contrast, two other derivatives n¼10 and n¼12 dis-
played a strong reflection of d 33.04 Å at 145 ꢀC and d 37.21 Å at
150 ꢀC, respectively. These observed d-spacings were all shorter
than those of molecular lengths calculated by MM2 model, which
indicated the alkoxy chains of the molecules were probably
interdigitated in the mesophase. Compound 4 (n¼6) also gave
a diffraction peak of d 24.47 Å at 109 ꢀC and d 24.08 Å at 96 ꢀC. These
types of diffraction pattern corresponded to Miller indices 001 in
layer structures of SmA and SmC phases, shown in Figure 8. How-
ever, other diffraction peaks of higher orders indexed as 002, 003,
and others were notobserved. On the other hand, the compounds 2a
(n¼12, 14) and 1a (n¼12, 14, 16) exhibited different diffraction pat-
terns. All these compounds displayed the diffraction pattern of
a two-dimensional hexagonal lattice, with one stronger peak and
two weaker peaks. These are characteristic of columnar phases with
a d-spacing ratio of 1, (1/3)1/2, and (1/4)1/2, corresponding to Miller
indices; 10, 11, and 20, respectively. For example, a diffraction pat-
tern with a d-spacing at 31.90 Å,18.44 Å,16.03 Å and a broad diffuse
peak (4.59 Å) at wide-angle region was observed for compound 2a
(n¼14) and this diffraction pattern corresponded to a hexagonal
columnar arrangement (see Fig. 9). This pattern corresponds to an
intercolumnar distance or lattice constant (i.e., a parameter of the
hexagonal lattice) of 36.7 Å. All compounds 1a gave similar diffrac-
tion patters as compounds 2a. Interestingly, the lattice constants of
2.4. Variable temperature XRD diffraction
Variable-temperature powder XRD diffraction was conducted to
confirm the structure of the mesophases. A summary of the dif-
fraction peaks and lattice constants for compounds 1, 2, and 4 is
listed in Table 5. For compound 2b (n¼6, 10, 12), only one strong
diffraction peak at lower angle was observed, which corresponded
to a layer structure of SmA or SmC phase. The relative intensity of the

1136
S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
OR
OR
OR
O
RO
O
RO
RO
OR
RO
N
NH
N
N
N
N
H
Cl Ni Cl
H
HN
N
OR
OR
OR
OR
RO
RO
RO
RO
O
O
2a
1a
Figure 7. Schematic representation of proposed structures for the formation of columnar phases in compounds 2a and 1a. The dashed line in 2a is an intermolecular H-bonding.
Table 5
Variable-temperature XRD diffraction data for compounds 1a, 2a,2b, and 4
Compound
Mesophase/ꢀC
SmA (130 ꢀC)
Lattice constant/Å
d-Spacing/Å obsd
28.70 (30.08a)
Miller indices
001
2b (n¼6)
d
2b (n¼10)
2b (n¼12)
4 (n¼6)
SmC (145 ꢀC)
SmC (150 ꢀC)
d
d
33.04 (41.06a)
37.21 (47.43a)
001
001
SmA (109 ꢀC)
SmC (96 ꢀC)
d
d
24.47 (30.08a)
24.08 (30.08a)
001
001
2a (n¼12)
2a (n¼14)
Colh (80 ꢀC)
a¼34.32
a¼36.70
29.72 (29.72)
4.56
100
halo
Colh (80 ꢀC)
31.90 (31.90)
18.44 (18.42)
16.03 (15.95)
4.59
10
11
20
halo
1a (n¼12)
1a (n¼14)
Colh (104 ꢀC)
Colh (120 ꢀC)
a¼33.82
a¼35.76
29.29 (29.29)
16.93 (16.91)
4.61
10
11
halo
30.97 (30.97)
17.89 (17.88)
15.57 (15.48)
4.60
10
11
20
halo
1a (n¼16)
Colh (115 ꢀC)
a¼37.44
32.42 (32.42)
18.70 (18.72)
16.23 (16.21)
4.64
10
11
20
halo
a
Molecular length estimated by MM2 model.
two compounds 2a and 1a were quite similar in value, indicating
that the size or the diameter of the columns formed in hexagonal
columnar phases was approximately equal.
thermographs were carried out on a Mettler DSC 822 and calibrated
with a pure indium sample. All phase transitions are determined by
a scan rate of 10.0ꢀ/min. Optical polarized microscopy was carried
out on Zeiss Axioplan 2 equipped with a hot stage system of Mettler
FP90/FP82HT. Elemental analyses were performed on a Heraeus
CHN-O-Rapid elemental analyzer. The powder diffraction data were
collected from the Wiggler-A beamline of the National Synchrotron
Radiation Research Center (NSRRC) with the wavelength of
3. Conclusions
A new series of unsymmetrical pyrazoles 2a,2b and their nick-
el(II) complexes 1a were prepared and mesomorphic properties
investigated. All compounds formed mesomorphic behavior. Nickel
ion preferred the square-planar coordination, which favored the
molecular packings. A dimeric structure formed by intermolecular
H-bonding was used to induce the formation of the mesophases in
such system. Other metal complexes might be prepared in future.
1.3263 Å. Diffraction patterns were recorded in q/2q geometry with
step scans normally 0.02ꢀ in 2
q
¼1–10ꢀ stepꢁ1 sꢁ1 and 0.05ꢀ in
2q
¼10–25ꢀ stepꢁ1 sꢁ1 and a gas flow heater was used to control the
temperature. The powder samples were charged in Lindemann
capillary tubes (80 mm long and 0.01 mm thick) from Charles
Supper Co. with an inner diameter of 1.0 mm.
4. Experimental
4.1. General
4.2. 1,5-Bis(3,4-bis(dodecyloxy)phenyl)pentane-1,3,5-trione
(3a; n[12)
All chemicals and solvents were reagent grade from Aldrich
Chemical Co., and all solvents were dried by standard techniques.
1H and 13C NMR spectra were measured on a Bruker DRS-200. DSC
Yellow powder, yield 60%. 1H NMR (CDCl3):
–CH3, 12H), 1.23–1.84 (m, –CH2, 80H), 4.02 (t, J¼4.2 Hz, –CH2, 8H),
d
0.85 (t, J¼6.45 Hz,

S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
1137
20000
15000
10000
5000
0
50000
33.04 Å
31.90 Å
40000
30000
20000
10000
18.44 Å
16.03 Å
4.59 Å
20
0
5
10
15
20
25
5
10
15
2 Theta
25
30
12000
10000
8000
6000
4000
2000
0
60000
50000
40000
30000
20000
30.97 Å
28.7 Å
17.89 Å
15.57 Å
10000
0
5
10
15
20
25
4.60 Å
Figure 8. The powder X-ray diffraction patterns for compounds; 2b (n¼10, top plot) at
145.0 ꢀC and 2b (n¼6, bottom plot) at 130.0 ꢀC.
5
10
15
2 Theta
20
25
30
[5.88 (s), 6.20 (s)] (OCCHCO, 2H), [6.84 (d), 7.40 (d), 7.53 (d), 7.60
(d)] (ArH, 6H), [14.84 (s), 16.06 (s)] (COH, 2H). 13C NMR (CDCl3):
Figure 9. The powder X-ray diffraction patterns for compounds; 2a (n¼14, top plot) at
80.0 ꢀC and 1a (n¼14, bottom plot) at 120.0 ꢀC.
d
14.09, 22.69, 26.01, 29.02, 29.09, 29.14, 29.24, 29.38, 29.64,
31.93, 50.14, 69.05, 69.23, 69.39, 95.51, 96.19, 111.61, 112.05, 112.16,
112.58, 112.79, 120.21, 121.44, 123.99, 126.25, 126.69, 129.29,
148.94, 149.00, 152.42, 153.35, 154.14, 173.43, 183.21, 188.64, 192.50,
193.00.
154.02, 194.24. Anal. Calcd for C65H110N2O5: C, 78.10; H, 11.09.
Found: C, 77.90; H, 11.04.
4.5. 1-(3,4-Bis(hexyloxy)phenyl)-2-(3-(3,4-bis(hexyloxy)-
4.3. 1,5-Bis(4-(dodecyloxy)phenyl)pentane-1,3,5-trione
phenyl)-1H-pyrazol-5-yl)ethanone (2a; n[6)
(3b; n[12)
White powder, yield 68%. 1H NMR (CDCl3):
d
0.92 (t, J¼2.4 Hz,
Yellow powder, yield 68%. 1H NMR (CDCl3):
d
0.84 (t, J¼6.6 Hz,
–CH3, 12H), 1.35–1.85 (m, –CH2, 32H), 4.00 (t, J¼3.15 Hz, –CH2, 8H),
4.34 (s, –CH2C, 2H), 6.45 (s, –CH–CN, 1H), [6.85 (d), 7.29 (d), 7.54 (d),
–CH3, 6H), 1.23–1.78 (m, –CH2, 40H), 3.98 (t, J¼3.3 Hz, –CH2, 4H),
[5.88 (s), 6.20 (s)] (OCCHCO, 2H), [J¼1.5 Hz, 6.91 (d), J¼0.9 Hz, 7.77
(d), J¼9 Hz, 7.96 (d)] (ArH, 8H), [14.84 (s), 16.06 (s)] (COH, 2H). 13C
7.59 (d)] (ArH, 6H). 13C NMR (CDCl3):
d 13.91, 22.50, 25.60, 28.90,
29.00, 29.16, 31.47, 31.51, 36.46,68.92, 69.10, 69.17, 102.26, 111.26,
111.43, 112.44, 113.65, 118.36, 123.48, 123.83, 128.86, 142.53, 147.94,
148.86, 149.27, 153.86, 194.68. Anal. Calcd for C41H62N2O5: C, 74.28;
H, 9.43. Found: C, 74.56; H, 9.56.
NMR (CDCl3):
d 13.98, 22.56, 25.85, 28.98, 29.03, 29.23, 29.46,
29.52, 31.80, 50.21, 53.24, 68.14, 68.22, 95.19, 95.90, 114.05, 114.31,
125.77, 126.18, 128.04, 128.92, 129.10, 130.90, 131.16, 132.15, 161.99,
162.85, 163.57, 170.48, 173.20, 182.50, 184.46, 189.19, 192.32, 192.62,
193.11.
4.6. 1-(3,4-Bis(octyloxy)phenyl)-2-(3-(3,4-bis(octyloxy)-
4.4. 1-(3,4-Bis(dodecyloxy)phenyl)-2-(3-(3,4-
phenyl)-1H-pyrazol-5-yl)ethanone (2a; n[8)
bis(dodecyloxy)phenyl)-1H-pyrazol-5-yl)ethanone (2a; n[12)
White powder, yield 70%. 1H NMR (CDCl3):
d
0.84 (t, J¼6.3 Hz,
White powder, yield 78%. 1H NMR (CDCl3):
d
0.84 (t,
–CH3, 12H), 1.24–1.79 (m, –CH2, 48H), 3.96 (t, J¼5.25 Hz, –CH2, 8H),
J¼6.45 Hz, –CH3, 12H), 1.22–1.78 (m, –CH2, 80H), 3.98 (t, J¼6.3 Hz,
–CH2, 8H), 4.57 (s, COCH2C]C, 2H), 6.61 (s, ]CH–C]N, 1H), [6.85
(d), 7.38 (d), 7.51 (d), 7.67 (d)] (ArH, 6H). 13C NMR (CDCl3):
4.29 (s, –CH2C, 2H), 6.39 (s, –CH–CN, 1H), [6.79 (d), 7.17 (d), 7.49 (d),
7.56 (d)] (ArH, 6H). 13C NMR (CDCl3):
d 13.97, 22.57, 25.94, 28.96,
29.07, 29.18, 31.73, 36.13, 68.94, 69.16, 69.28, 102.70, 111.30, 111.49,
112.45, 113.62, 118.76, 123.45, 128.78, 142.54, 147.80, 148.90, 149.27,
153.95, 194.00. Anal. Calcd for C49H78N2O5: C, 75.92; H, 10.14.
Found: C, 76.12; H, 10.11.
d
14.09, 22.69, 26.05, 29.07, 29.18, 29.38, 29.48, 29.67, 31.93,
36.32, 69.03, 69.24, 69.35, 102.61, 111.55, 112.51, 113.73, 118.74,
123.08, 123.55, 128.87, 142.66, 147.87, 148.98, 149.42, 149.72,

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S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
4.7. 1-(3,4-Bis(decyloxy)phenyl)-2-(3-(3,4-
bis(decyloxy)phenyl)-1H-pyrazol-5-yl)ethanone (2a; n[10)
4.30 (s, –CH2C, 2H), 6.37 (s, –CH–CN, 1H), [J¼3.0 Hz, 6.88 (d),
J¼8.40 Hz, 7.52 (d), J¼9.00 Hz, 7.96 (d)] (ArH, 8H). 13C NMR (CDCl3):
d
13.05, 21.60, 24.92, 24.99, 28.20, 28.26, 28.32 30.76, 35.66, 67.04,
White powder, yield 75%. 1H NMR (CDCl3):
d
0.85 (t, J¼6.0 Hz,
67.29, 101.22, 113.3, 113.75, 122.43, 125.93, 127.86, 129.92, 141.62,
146.80, 158.27, 162.48, 193.66. Anal. Calcd for C33H46N2O3: C, 76.41;
H, 8.94. Found: C, 76.11; H, 9.03.
–CH3, 12H), 1.24–1.80 (m, –CH2–, 64H), 3.98 (t, J¼5.4 Hz, –CH2, 8H),
4.33 (s, –CH2C, 2H), 6.45 (s, –CH–CN, 1H), [6.81 (d), 7.30 (d), 7.49 (d),
7.56 (d)] (ArH, 6H). 13C NMR (CDCl3):
d 14.08, 22.68, 26.04, 29.06,
29.17, 29.36, 29.46, 29.61, 31.92, 36.27, 69.02, 69.23, 69.34, 102.70,
111.55, 112.51, 113.70, 118.78, 123.55, 128.87, 142.65, 147.87, 148.39,
148.97, 149.42, 154.01, 194.17. Anal. Calcd for C57H94N2O5: C, 77.15;
H, 10.68. Found: C, 77.42; H, 10.68.
4.13. 1-(4-Decyloxyphenyl)-2-(3-(4-decyloxyphenyl)-1H-
pyrazol-5-yl)ethanone (2b; n[10)
White powder, yield 71%. 1H NMR (CDCl3):
d
0.85 (t, J¼6.0 Hz,
–CH3, 6H), 1.40–2.14 (m, –CH2, 32H), 3.94 (t, J¼7.35 Hz, –CH2, 4H),
4.32 (s, –CH2C, 2H), 6.38 (s, –CH–CN, 1H), [J¼1.8 Hz, 6.89 (d),
J¼8.4 Hz, 7.53 (d), J¼8.1 Hz, 7.97 (d)] (ArH, 8H). 13C NMR (CDCl3):
4.8. 1-(3,4-Bis(tetradecyloxy)phenyl)-2-(3-(3,4-bis(tetra-
decyloxy)phenyl)-1H-pyrazol-5-yl)ethanone (2a; n[14)
d
13.91, 22.48, 25.85, 29.37, 31.71, 68.16, 102.30, 114.20, 114.66,
White powder, yield 72%. 1H NMR (CDCl3):
d
0.84 (t, J¼6.0 Hz,
126.72, 126.97, 130.77, 131.97, 147.64, 159.35, 194.20. Anal. Calcd for
C37H54N2O3: C, 77.31; H, 9.47. Found: C, 77.30; H, 9.58.
–CH3, 12H), 1.22–1.78 (m, –CH2, 96H), 3.98 (t, J¼6.75 Hz, –CH2, 8H),
4.46 (s, –CH2C, 2H), 6.58 (s, –CH–CN, 1H), [6.82 (d), 7.34 (d), 7.46 (d),
7.59 (d)] (ArH, 6H). 13C NMR (CDCl3):
d 14.09, 22.68, 26.05, 29.06,
4.14. 1-(4-Tetradecyloxyphenyl)-2-(3-(4-tetradecyloxyphenyl)-
1H-pyrazol-5-yl)ethanone (2b; n[14)
29.17, 29.37, 29.68, 29.72, 31.93, 36.23, 69.05, 69.25, 69.39, 111.58,
112.53, 113.72, 118.81, 122.91, 123.52, 128.86, 149.00, 149.44, 149.83,
154.06, 194.11. Anal. Calcd for C73H126N2O5: C, 78.86; H, 11.42.
Found: C, 78.93; H, 11.43.
White powder, yield 72%. 1H NMR (CDCl3):
d
0.85 (t, J¼6.6 Hz,
–CH3, 6H), 1.23–1.69 (m, –CH2, 48H), 3.97 (t, J¼6.9 Hz, –CH2, 4H),
4.32 (s, –CH2C, 2H), 6.38 (s, –CH–CN, 1H), [J¼7.2 Hz, 6.90 (d),
J¼7.5 Hz, 7.52 (d), J¼9.3 Hz, 7.98 (d)] (ArH, 8H). Anal. Calcd for
C45H70N2O3: C, 78.67; H, 10.27. Found: C, 78.38; H, 10.26.
4.9. 1-(3,4-Bis(hexadecyloxy)phenyl)-2-(3-(3,4-
bis(hexadecyloxy)phenyl)-1H-pyrazol-5-yl)ethanone
(2a; n[16)
White powder, yield 68%. 1H NMR (CDCl3):
d
0.84 (t, J¼6.45 Hz,
4.15. 1-(4-Hexadecyloxyphenyl)-2-(3-(4-hexadecyloxyphenyl)-
1H-pyrazol-5-yl)ethanone (2b; n[16)
–CH3, 12H), 1.23–1.82 (m, –CH2, 112H), 4.03 (t, J¼8.7 Hz, –CH2, 8H),
4.57 (s, –CH2C, 2H), 6.61 (s, –CH–CN, 1H), [6.87 (d), 7.47 (d), 7.51 (d),
7.67 (d)] (ArH, 6H). Anal. Calcd for C81H142N2O5: C, 79.48; H, 11.69.
Found: C, 79.45; H, 11.70.
White powder, yield 75%. 1H NMR (CDCl3):
d 0.84 (t, –CH3, 6H),
1.22–1.82 (m, –CH2, 56H), 3.96 (t, J¼7.05 Hz, –CH2, 4H), 4.32 (s,
–CH2C, 2H), 6.38 (s, –CH–CN, 1H), [J¼7.2 Hz, 6.90 (d), J¼6.9 Hz, 7.53
(d), J¼7.8 Hz, 7.97 (d)] (ArH, 8H). Anal. Calcd for C49H78N2O3: C,
79.19; H, 10.58. Found: C, 78.91; H, 10.59.
4.10. 1-(4-Dodecyloxyphenyl)-2-(3-(4-dodecyloxyphenyl)-1H-
pyrazol-5-yl)ethanone (2b; n[12)
4.16. Nickel complexes of 1-(3,4-bis(dodecyloxy)phenyl)-2-(3-
(3,4-bis(dodecyloxy)phenyl)-1H-pyrazol-5-yl)ethanone
(1a; n[12)
To a solution of 1,5-bis(4-(dodecyloxy)phenyl)pentane-1,3,5-
trione (5.0 g, 7.87 mmol) dissolved in absolute ethanol (45 mL)
was added hydrazine monohydrate (0.43 g, 8.66 mmol), and the
mixture was refluxed for 2 h under nitrogen atmosphere. The
ethanol was removed under vacuum. The off-white residue was
then purified by recrystallization from THF/MeOH. The product
was isolated as white powder with a yield of 75%. 1H NMR
To a solution of 1-(3,4-bis(dodecyloxy)phenyl)-2-(3-(3,4-bis-
(dodecyloxy)phenyl)-1H-pyrazol-5-yl)ethanone (0.400 g, 0.400 mmol)
dissolved in 20 mL ethanol was added nickel(II) chloride. The so-
lution was refluxed for 24 h. The solution was concentrated to
dryness, and the residue was purified by recrystallization from THF/
CH3OH. The product was isolated as light green solids. Yield 70%.
Anal. Calcd for C130H220N4O10NiCl2: C, 73.35; H, 10.42; N,
2.63. Found: C, 73.99; H, 10.75; N, 2.61. Compound 1a (n¼14).
Anal. Calcd for C146H252N4O10NiCl2: C, 74.52; H, 10.79; N, 2.38.
Found: C, 74.59; H, 10.95; N, 2.38. Compound 1a (n¼16). Anal.
Calcd for C162H284N4O10NiCl2: C, 75.49; H, 11.11. Found: C, 75.34;
H, 11.02.
(CDCl3):
d
0.85 (t, J¼6.75 Hz, –CH3, 6H), 1.23–1.80 (m, –CH2, 40H),
3.97 (t, J¼4.2 Hz, –OCH2, 4H), 4.32 (s, –CH2C, 2H), 6.39 (s, –CH–CN,
1H), [J¼1.5 Hz, 6.89 (d), J¼8.4 Hz, 7.54 (d), J¼8.4 Hz, 7.97 (d)] (ArH,
8H). Anal. Calcd for C41H62N2O3: C, 78.05; H, 9.90. Found: C, 77.74;
H, 9.86.
4.11. 1-(4-Hexyloxyphenyl)-2-(3-(4-hexyloxyphenyl)-1H-
pyrazol-5-yl)ethanone (2b; n[6)
White powder, yield 70%. 1H NMR (CDCl3):
d 0.85 (t, –CH3, 6H),
1.32–1.78 (m, –CH2, 16H), 3.94 (t, J¼4.05 Hz, –OCH2, 4H), 4.30 (s,
4.17. 1-(4-(Dodecyloxy)phenyl)-2-(3-(4-(dodecyloxy)phenyl)-
isoxazol-5-yl)ethanone (4; n[12)
–CH2C, 2H), 6.37 (s, –CH–CN, 1H), [J¼3.60 Hz, 6.87 (d), J¼6.90 Hz,
7.54 (d), J¼1.80 Hz, 7.98 (d)] (ArH, 8H). 13C NMR (CDCl3):
d 13.98,
22.56, 25.61, 25.67, 29.01, 29.17, 31.05, 31.56, 36.44, 68.06, 68.30,
102.59, 114.03, 114.33, 122.65, 127.22, 128.81, 130.92, 142.57, 147.63,
159.58, 163.52, 194.15. Anal. Calcd for C29H38N2O3: C, 75.29; H, 8.28.
Found: C, 75.13; H, 8.43.
To a solution of 1,5-bis(4-(dodecyloxy)phenyl)pentane-1,3,5-
trione (5.0 g, 7.87 mmol) dissolved in 35 mL of absolute ethanol
was added hydroxylamine hydrochloride (0.6 g, 8.66 mmol) under
nitrogen atmosphere. The solution was gently refluxed for 2 h. The
solution was then stirred at room temperature for 12 h. The solvent
was removed under reduced pressure, and the product isolated
as white powder was obtained after recrystallization from THF/
4.12. 1-(4-Octyloxyphenyl)-2-(3-(4-octyloxyphenyl)-1H-
pyrazol-5-yl)ethanone (2b; n[8)
MeOH. Yield 75%. 1H NMR (CDCl3):
1.24–1.77 (m, –CH2, 40H), 3.98 (t, J¼4.5 Hz, –CH2, 4H), [4.31, 4.40]
(s, –CH2C, 2H), [6.41, 6.50] (s, –CH–CN, 1H), [J¼8.7 Hz, 6.92 (d),
d
0.85 (t, J¼6.75 Hz, –CH3, 6H),
White powder, yield 71%. 1H NMR (CDCl3):
–CH3, 6H), 1.25–1.78 (m, –CH2, 24H), 3.92 (t, J¼7.35 Hz, –CH2, 4H),
d
0.85 (t, J¼6.45 Hz,

S.-Y. Chou et al. / Tetrahedron 65 (2009) 1130–1139
1139
J¼1.2 Hz, 7.67 (d), J¼2.4 Hz, 7.99 (d)] (ArH, 8H). 13C NMR (CDCl3):
Giroud-Godquin, A. M.; Maitlis, P. M. Angew. Chem., Int. Ed. Engl. 1991, 30, 375–
402; (f) Giroud-Godquin, A. M. Coord. Chem. Rev. 1998, 178, 1485–1499.
2. (a) Seredyuk, M.; Gaspar, A. B.; Ksenofontov, V.; Galyametdinov, Y.; Kusz, J.;
Guu¨tlich, P. J. Am. Chem. Soc. 2008, 130, 1431–1439; (b) Zheng, H.; Swager, T. M.
J. Am. Chem. Soc. 1994, 116, 761–762; (c) Trzaska, S. T.; Hsu, H. F.; Swager, T. M.
J. Am. Chem. Soc. 1999, 121, 4518–4519; (d) Cardinaels, T.; Ramaekers, J.; Guillon,
D.; Donnio, B.; Binnemans, K. J. Am. Chem. Soc. 2005, 127, 17602–17603.
3. Trofimenko, S. Chem. Rev. 1972, 72, 497–509.
d
14.10, 22.68, 25.96, 29.06, 29.16, 29.34, 29.57, 29.63, 31.91, 36.15,
36.60, 68.17, 68.36, 98.82, 101.35, 114.42, 114.51, 114.83, 120.05,
121.34, 127.38, 128.16, 128.83, 131.00, 160.68, 163.65, 166.36, 170.22,
193.35. Anal. Calcd for C41H61NO4: C, 77.93; H, 9.73. Found: C, 78.14;
H, 9.76.
4. (a) Trofimenko, S. Prog. Inorg. Chem. 1986, 34, 115–210; (b) Niedenzu, K.;
Trofimenko, S. Top. Curr. Chem. 1986, 131, 1–37.
4.18. 1-(4-(Hexyloxy)phenyl)-2-(3-(4-(hexyloxy)phenyl)-
isoxazol-5-yl)ethanone (4; n[6)
5. (a) La Monica, G.; Ardizzoia, G. A. Prog. Inorg. Chem. 1997, 46, 151–238; (b) Ei-
genbrot, C. W., Jr.; Raymond, K. N. Inorg. Chem. 1982, 21, 2653–2660; (c) Ro¨ttger,
D.; Erker, G.; Grehl, M.; Fro¨lich, R. Organometallics 1994, 13, 3897–3902.
6. (a) Rasika Dias, H. V.; Palehepitiya Gamage, C. S.; Keltner, J.; Diyabalanage,
H. V. K.; Omara, I.; Eyobo, Y.; Dias, N. R.; Roehr, N.; McKinney, L.; Poth, T. Inorg.
White powder, yield 61%. 1H NMR (CDCl3):
d 0.88 (t, –CH3, 6H),
1.31–1.76 (m, –CH2, 16H), 3.98 (t, J¼7.8 Hz, –CH2, 4H), [4.30, 4.38] (s,
´
Chem. 2007, 46, 2979–2987; (b) Mohamed, A. A.; Perez, L. M.; Fackler, J. P. Inorg.
Chim. Acta 2005, 358, 1657–1662; (c) Kishimura, A.; Yamashita, T.; Aida, T. J. Am.
Chem. Soc. 2005, 127, 179–183; (d) Dias, H. V. R.; Diyabalanage, H. V. K.; Eldabaja,
M. G.; Elbjeirami, O.; Rawashdeh-Omary, M. A.; Omary, M. A. J. Am. Chem. Soc.
2005, 127, 7489–7501; (e) Dias, H. V. R.; Diyabalanage, H. V. K. Polyhedron 2006,
25, 1655–1661; (f) Grimes, T.; Omary, M. A.; Dias, H. V. R.; Cundari, T. R. J. Phys.
Chem. A 2006, 110, 5823–5830; (g) Dias, H. V. R.; Diyabalanage, H. V. K.;
Gamage, C. S. P. Chem. Commun. 2005, 1619–1621.
7. (a) Wang, Z.; Abernethy, C. D.; Cowley, A. H.; Jones, J. N.; Jones, R. A.;
Macdonald, C. L. B.; Zhang, L. J. Organomet. Chem. 2003, 666, 35–42; (b) Guzei,
I. A.; Baboul, A. G.; Yap, G. P. A.; Rheigold, A. L.; Schlegel, B.; Winter, C. H. J. Am.
Chem. Soc. 1997, 119, 3387–3388.
8. (a) Ehlert, M. K.; Rettig, S. J.; Storr, A.; Thompson, R. C.; Trotter, J. Can. J. Chem.
1990, 68, 1444–1449; (b) Ardizzoia, G. A.; Cenine, S.; Monica, G. L.; Masciocchi,
N.; Maspero, A.; Moret, M. Inorg. Chem. 1998, 37, 4284–4292.
9. (a) Ardizzoia, G. A.; Cenine, S.; Monica, G. L.; Masciocchi, N.; Moret, M. Inorg.
Chem. 1994, 33, 1458–1463; (b) Kavlakoglu, E.; Elmali, A.; Elerman, Y.; Svoboda,
I. Polyhedron 2002, 21, 1539–1545.
–CH2C, 2H), [6.41, 6.50] (s, –CH–CN, 1H), [J¼8.7 Hz, 6.92 (d), J¼9 Hz,
7.66 (d), J¼9 Hz, 7.98 (d)] (ArH, 8H). 13C NMR (CDCl3):
d 13.94, 22.51,
25.57, 25.62, 28.96, 29.07, 31.46, 31.50, 36.10, 68.12, 98.74, 101.29,
114.36, 114.46, 114.78 120.00, 127.33, 128.77, 130.96, 158.84, 160.62,
163.59, 170.15, 193.31. Anal. Calcd for C29H37NO4: C, 75.13; H, 8.04.
Found: C, 75.34; H, 8.06.
4.19. 1-(4-(Heptyloxy)phenyl)-2-(3-(4-(heptyloxy)phenyl)-
isoxazol-5-yl)ethanone (4; n[7)
White powder, yield 62%. 1H NMR (CDCl3):
d 0.86 (t, –CH3, 6H),
1.28–1.57 (m, –CH2, 20H), 3.99 (t, J¼7.8 Hz, –CH2, 4H), [4.30, 439]
(s, –CH2C, 2H), [6.41, 6.50] (s, –CH–CN, 1H), [J¼8.7 Hz, 6.92 (d),
J¼8.7 Hz, 7.66 (d), J¼9.0 Hz, 7.98 (d)] (ArH, 8H). 13C NMR (CDCl3):
10. (a) Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J. V.; Pinilla, E.; Torres, M. R.
J. Organomet. Chem. 2006, 691, 765–778; (b) Torralba, M. C.; Campo, J. A.; Heras,
d
13.95, 22.48, 25.81, 28.93, 29.06, 31.07, 31.64, 34.06, 36.05,
´
J. V.; Bruce, D. W.; Cano, M. Dalton Trans. 2006, 3918–3926; (c) Barbera, J.;
36.49, 68.07, 68.25, 98.70, 101.24, 114.31, 114.41, 114.73, 119.95,
127.28, 128.06, 128.72, 130.90, 158.79, 162.24, 163.54, 170.10,
193.25. Anal. Calcd for C31H41NO4: C, 75.73; H, 8.41. Found: C,
75.84; H, 8.46.
Elduque, A.; Gime´nez, R.; Lahoz, F. L.; Lo´ pez, J. A.; Oro, L. A.; Serrano, J. L.;
Villacampa, B.; Villalba, J. Inorg. Chem. 1999, 38, 3085–3092.
11. Barbera´, J.; Cativiela, C.; Serrano, J. L.; Zurbano, M. M. Liq. Cryst.1992, 11, 887–897.
12. Diez-Barra, E.; Hoz, A. d. l.; Sa´nchez-Migallo´n, A.; Tejeda, J. Heterocycles 1992,
34, 1365–1373.
13. Gime´nez, R.; Manrique, A. B.; Uriel, S.; Barbera´, J.; Serrano, J. L. Chem. Commun.
2004, 2064–2065.
14. (a) Bouwman, E.; Driessen, W. L.; Graaff, R. A. G.; deReedijk, J. Acta Crystallogr.,
Sect. C 1984, 40, 1562–1563; (b) Bovio, B.; Cingolani, A.; Bonati, F. Z. Anorg. Allg.
Chem. 1992, 610, 151–156.
4.20. 1-(4-(Octyloxy)phenyl)-2-(3-(4-(octyloxy)phenyl)-
isoxazol-5-yl)ethanone (4; n[8)
15. (a) Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J. V.; Pinilla, E.; Torres, M. R.
J. Organomet. Chem. 2001, 633, 91–104; (b) Torralba, M. C.; Cano, M.; Campo,
J. A.; Heras, J. V.; Pinilla, E.; Torres, M. R. J. Organomet. Chem. 2002, 654, 150–161.
16. (a) Canom, N.; Heras, J. V.; Maeso, M.; Alvaro, M.; Fernfindez, R.; Pinilla, E.;
Campo, J. A.; Monge, A. J. Organomet. Chem. 1997, 534, 159–172; (b) Lo´pez, C.;
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Monge, A. J. Organomet. Chem. 1996, 511, 115–127.
White powder, yield 60%. 1H NMR (CDCl3):
d 0.86 (t, –CH3, 6H),
1.26–1.78 (m, –CH2, 24H), 3.96 (t, J¼3.3 Hz, –CH2, 4H), [4.30, 438] (s,
–CH2C, 2H), [6.41, 6.50] (s, –CH–CN, 1H), [J¼9.0 Hz, 6.92 (d),
J¼8.7 Hz, 7.65 (d), J¼6.3 Hz, 7.98 (d)] (ArH, 8H). 13C NMR (CDCl3):
d
13.94, 22.50, 25.82, 25.86, 28.93, 29.07, 29.16, 31.65, 36.00, 68.03,
17. (a) Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J. V.; Pinilla, E. Z. New Cryst.
Struct. 2005, 220, 615–616; (b) Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J.
V.; Pinilla, E.; Torres, M. R. Inorg. Chem. Commun. 2002, 5, 887–890; (c) Mayoral,
M. J.; Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J. V. Inorg. Chem. Commun.
2003, 6, 626–629; (d) Torralba, M. C.; Cano, M.; Go´mez, S.; Campo, J. A.; Heras,
J. V.; Perles, J.; Ruiz-Valero, C. J. Organomet. Chem. 2003, 682, 26–34;
(e) Torralba, M. C.; Cano, M.; Campo, J. A.; Heras, J. V.; Pinilla, E.; Torres, M. R.
Inorg. Chem. Commun. 2006, 9, 1271–1275.
68.22, 98.70, 101.22, 114.28, 114.37, 114.70, 119.92, 127.24, 128.02,
128.70, 130.86, 158.77, 160.54, 163.50, 170.06, 193.19. Anal. Calcd for
C33H45NO4: C, 76.26; H, 8.73. Found: C, 76.11; H, 8.85.
Acknowledgements
18. Henslee, G. H.; Oliver, J. D. J. Cryst. Mol. Struct. 1977, 7, 137–146.
19. (a) Lin, H. D.; Lai, C. K. J. Chem. Soc., Dalton Trans. 2001, 2383–2387; (b) Barbera´,
J.; Elduque, A.; Gime´nez, R.; Oro, L. A.; Serrano, J. L. Angew. Chem., Int. Ed. 1996,
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L. A.; Serrano, J. L. Inorg. Chem. 1998, 37, 2960–2967; (e) Kim, S. J.; Kang, S. H.;
Park, K. M.; Kim, H.; Zin, W. C.; Choi, M. G.; Kim, K. Chem. Mater. 1998, 10, 1889–
We thank the National Science Council of Taiwan, ROC (NSC 96-
2113-M-008-MY2 and NSC 96-2752-M-008-010-PAE) in generous
support of this work.
References and notes
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