The enhanced π-π Interactions in metallomesogens

Article abstract of DOI:10.1016/j.tet.2015.09.006

Two new series of mesogenic palladium complexes 1a-b derived from salicylaldimines containing phenyl or naphenyl moiety were prepared, characterized and their mesomorphic properties investigated. Two single crystallographic structures of mesogenic 1a (n=4

Full text of DOI:10.1016/j.tet.2015.09.006

Tetrahedron 71 (2015) 8649e8660
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Tetrahedron
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The enhanced
pep
interactions in metallomesogens
y
*
Ta-Ming Liu, Kuan-Ting Lin, Fu-Joun Li, Gene-Hsiang Lee , Ming-Chou Chen ,
Chung K. Lai
*
Department of Chemistry, National Central University, & Center for Nano Science Technology, UST, Chung-Li 32054, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2015
Received in revised form 29 August 2015
Accepted 3 September 2015
Available online 16 September 2015
Two new series of mesogenic palladium complexes 1aeb derived from salicylaldimines containing
phenyl or naphenyl moiety were prepared, characterized and their mesomorphic properties investigated.
Two single crystallographic structures of mesogenic 1a (n¼4) and nonmesogenic 1b (n¼3) were de-
termined by X-ray analysis; both crystals crystallize in a triclinic space group P1. The geometry at both
palladium atoms was nearly square planar. All Schiff bases 2aeb and palladium complexes 1aeb ex-
hibited mesomorphic properties. However, the formation of mesophases was sensitive to terminal
naphthalyl and phenyl group. Compounds 2a formed N or/and SmC phases and compounds 2b exhibited
N or/and SmC phases. In contrast, palladium complexes 1a formed N or N/SmC phases and complexes 1b
exhibited N, N or/and SmC phases. Compounds 1b have a higher clearing temperature than those of 1a
Keywords:
Metallomesogens
Salicladimines
Smectic
by a
D
Tcl¼35.4ꢀ14.8 ꢁC. An improved mesomorphic behavior observed in compounds 1b was attributed
Nematic
to the H-bonds and pep interaction.
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
metallomesogens11e13 IeII (Fig. 1) were previously prepared and
their mesomorphic properties studied. Complexes Ia, IIa formed
smectic phases, while complexes Ib, IIb exhibited columnar phases.
A phase change was often possible by altering their length-to-
width ratios (or aspect ratios) of the prepared molecules. How-
ever, a lack of single crystallographic data of particular molecules
was not able to allow us to understand its microscopic information
on the formation of observed mesophases.
In this work, two new series of mesogenic palladium complexes
derived from salicylaldimines were prepared, characterized and
their mesomorphic properties were studied. Two single crystallo-
graphic structures of mesogenic 1a (n¼4) and nonmesogenic 1b
(n¼3) were determined by X-ray analysis in order to understand
the relationship of structure-property. A terminal moiety contain-
ing naphthalyl and phenyl groups was incorporated to enhance
their intermolecular interactions. Single crystallographic data in-
Novel metallomesogens1e3 generated by incorporation of metal
ions into organic moieties have been successfully applied during
the past decades. Metal ions played an important role in the
resulting mesomorphic properties, and metallomesogens might be
obtained by non-mesogenic organic ligands. In contrast, the me-
somorphic properties may be totally lost upon incorporation of
a metal ion. A precise prediction of phase behavior has not been
feasible. One of the major challenges in the design of mesogenic
materials is to understand the molecular interaction induced in the
liquid crystal states. This is particularly crucial in the field of
mesogenic materials. Too strong or too weak an interaction force
often resulted in the formation of a solid or liquid state. On the
other hand, the study of structure-property relationship is needed
since they often provide much microscopically and/or macroscop-
ically useful information in the formation of mesophases.
dicated that CHep or/and pep interactions were responsible to the
Salicylaldimines4e8 were probably one of the most ligands
employed to generate metallomesogenic materials due to their
synthetic versatilities and abilities to the transition metal ions.
When structures were properly designed, some such derivatives
formation of mesophases. Compounds 2a formed N or/and SmC
phases, and compounds 2b exhibited N or/and SmC phases. In
contrast, palladium complexes 1a formed N, or/and SmC phases
and complexes 1b exhibited N, N and SmC phases.
were highly
p
-conjugated systems, useful in catalytic, photo-
few similar
physical and supramolecular applications.9,10
A
2. Results and discussion
2.1. Synthesis and characterization
* Corresponding authors. Tel.: þ886 0 3 4259207; fax: þ886 0 3 4277972; e-mail
All Schiff bases 2aeb and palladium complexes 1aeb were
summarized in Scheme 1 and Scheme 2. The compounds 2aeb
address: cklai@cc.ncu.edu.tw (C.K. Lai).
y
Instrumentation Center, National Taiwan University, Taipei 10660, Taiwan, ROC.
http://dx.doi.org/10.1016/j.tet.2015.09.006
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

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T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
X
O
X
RO
RO
O
N
M
N
OR
X
N
M
N
OR
O
O
O
O
X
X
RO
RO
OR
O
O
OR
X
Ia; X = H
Ib; X = OR
IIa; X = H
IIb; X = = OR
Fig. 1. The structures of known metallomesogens.
were similarly prepared from our previous procedures. The con-
densation reactions of appropriate 4-formyl-3-hydroxyphenyl 4-
(dodecyloxy)benzoate or 4-formyl-3-hydroxyphenyl 6-(dodecy-
loxy)-2-naphthoate and 3,4-dialkoxyphenylamines in refluxing
ethanol gave the compounds 2a and 2b, respectively. Both com-
pounds isolated as yellow solids were obtained after re-
crystallization from THF/CH3OH. The 1H and 13C NMR spectroscopy
in CDCl3 were used to characterize all intermediates. For instance,
2.2. Single crystal structures of palladium complexes derived
from (E)-4-(((3,4-dibutoxy phenyl)imino)methyl)-3-
hydroxyphenyl-4-(dodecyloxy)benzoate and (E)-4-(((3,4-
dipropoxyphenyl)imino)methyl)-3-hydroxyphenyl-2-
naphthoate
In order to understand the correlation between the molecular
structures and the formation of mesophases, two single crystals of
palladium complexes 1a (n¼4) and 1b (n¼3) were obtained and
their single crystallographic data were investigated. Light orange
crystals suitable for X-ray diffraction analysis were slowly grown
from CH2Cl2 at room temperature. Fig. 2 shows the molecular
structures with the atomic numberings, and Table 1 listed the
crystallographic and structural refinement data for the two
molecules.
two characteristic singlet peaks occurred at
d 8.57e8.59 and
13.63e13.78 ppm, assigned for imineeCH]N and phenoliceOH
groups were observed for compounds 2a. In contrast, these two
singlet peaks were slightly shifted to
d
8.59e8.60 and
13.37e13.72 ppm for compounds 2b. The phenolic peak eOH was
barely observed due to the formation of intramolecular H-bonds
with imineeN groups. The palladium complexes were obtained by
the reactions of appropriate palladium (II) acetate in refluxing
ethanol. The palladium complexes were isolated as lighteorange
compounds and the elemental analysis was used to confirm the
purity of the metal complexes.
The crystal 1b crystallizes in the triclinic space group p1, with
ꢀ
ꢀ
ꢀ
a¼9.1373 (1) A, b¼10.9230 (1) A, c¼13.5756 (2) A, and Z¼1. The
geometry at palladium center is nearly square planar. The two
angles of N (1)ePdeO (1)# and N (1)ePdeO are of 88.99 (5)ꢁ and
91.01 (5)ꢁ, which show almost an ideal angle of 90ꢁ expected for
a square-planar geometry. The overall structure of 1b was twisted
ꢀ
and the molecular length was 26.9 A (atoms C15eC15). The two
dihedral angles of ca. w84.9ꢁ (defined with N1eO1ePdeO1eN1
and C19eC24) and ca. w76.3ꢁ (with N1eO1ePdeO1eN1 and
naphthalene ring) were larger than those of crystal 1a. The larger
O
C12H25
O
OH
dihedral angles were probably attributed to intramolecular CHe
p
interactions and intermolecular H-bonds in the crystal 1a. In con-
trast, the crystal 1a crystallizes in the triclinic space group p1, with
a
ꢀ
ꢀ
ꢀ
a¼9.1762 (2) A, b¼10.2898 (2) A, c¼21.4015 (5) A, and Z¼1. The
geometry at palladium center is also slightly twisted square planar.
The two angles of N (1)ePdeO (1)# and N (1)ePdeO are of 88.42
(5)ꢁ and 91.58 (5)ꢁ. The overall structure of 1a was not planar and
O
O
RO
RO
NH2
C12H25
O
O
OH
ꢀ
also twisted. The molecular length was ca. 54.6 A (C32eC32). Two
dihedral angles of 60.9ꢁ and 53.5ꢁ between the core plane
(N1eO1ePdeO1eN1) and left phenyl (C15eC20) and right phenyl
rings (C9eC14) were measured. Important bond distances and
bond angles of two crystals are given in Table 2.
b
O
O
C12H25
O
A weak intramolecular CHep interaction, shown in Fig. 3, with
ꢀ
N
OR
OR
a length of 3.69 A was observed in crystal 1a, whereas, there was no
intramolecular interaction in crystal 1b. On the other hand, a few
intermolecular forces were observed in both crystal lattices; H-
2a
c
OH
bonds, CHep interaction and offset pep interaction. Fig. 4 showed
O
C12H25
O
OR
the intermolecular H-bonds in both crystal 1a, all with a length
ranged in 2.64e2.67 A. Compared to crystal 1a, no intramolecular
O
ꢀ
N
OR
force in crystal 1b was observed. This might be the reason why
crystal 1b has a larger dihedral angle. In fact, compounds 1b have
improved mesomorphic behavior than compounds 1a.
In contrast, intermolecular interactions in crystal 1b were also
observed. On the same layer, molecules were orderly arranged by
O
Pd
N
O
RO
O
O
OC12H25
RO
1a
ꢀ
H-bonds (H24A . O2¼2.52 A) and HePd bonds (H10A
.
Scheme 1. Reactions and reagents. (a) 2,4-Dihydroxybenzaldehyde (1.0 equiv), DCC,
DMAP in dry CH2Cl2, 24 h, 40%. (b) 3,4-dialkoxy-1-amino benzene (1.0 equiv),
CH3COOH (drops) in C2H5OH, 24 h, 75%. (c) Pd(OAc)2 (0.5 equiv), refluxing in C2H5OH,
2 h, 80%.
ꢀ
Pd¼2.81 A). On the above and below layers, molecules were
interacted by intermolecular CHe interaction (CeH27A
¼3.94 A). This probably was the reason why the phenyl ring
p
.
ꢀ
p

T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
8651
RO
RO
RO
RO
NO2
HO
C12H25
O
O
d
O
a
OH
OH
b
e
c
C12H25
O
O
O
RO
RO
NH2
HO
HO
O
f
OH
C12H25
O
O
O
N
OR
2b
g
OH
OR
C12H25
O
O
OR
O
N
OR
O
Pd
N
O
RO
O
O
RO
1b
OC12H25
Scheme 2. Reactions and reagents. (a) C12H25Br (2.1 equiv), KOH (1.1 equiv), refluxing in C2H5OH/H2O, 48 h, 88%. (b) 2,4-Dihydroxybenzaldehyde (1.0 equiv), DCC, DMAP in dry
CH2Cl2, 24 h, 62%. (c) RBr (2.1 equiv), KOH/KI, refluxing in acetone, 48 h, 80%. (d) HNO3 (1.2 equiv), H2SO4 (drops), stirred in CH2Cl2, 24 h, 86%. (e) H2NNH2 (1.2 equiv), Pd/C
(0.1 equiv), refluxing in C2H5OH, 24 h, 82%. (f) CH3COOH (drops), refluxing in C2H5OH, 24 h, 78%. (g) Pd(OAc)2 (0.5 equiv), refluxing in C2H5OH, 2 h, 75%.
Fig. 2. Two ORTEP plots are shown. The thermal ellipsoids of the non-hydrogen atoms are drawn at the 50% probably level. Top plot: 1a (n¼4), and a molecular length (C32eC32)¼
ꢀ
ꢀ
ꢀ
54.6 A, molecular width (C4eC17)¼7.56 A, molecular aspect ratio¼7.22. Bottom plot: compounds 1b (n¼3), and a molecular length (C15eC15)¼26.9 A, molecular width (C4eC17)¼
ꢀ
6.60 A, molecular aspect ratio¼4.08.
(C19wC24) was almost perpendicular to the core plane
(N1eO1ePdeO1eN1), which was favorable to the formation of
mesomorphic properties (see Table 3). However, when the phenyl
groups were extended to corresponding naphthalyl groups, from Ia
were mesogenic and exhibited nematic/smectic C or smectic C
phases. Their clearing temperatures remained at Tcl¼104.5e114.1 ꢁC
on the heating process, and the mesophase temperature decreased
slightly with carbon chain lengths;
D
Tmesophase¼42.7 (n¼4)>22.5
to Ib, the stronger
pe
p
interactions might not be the only param-
(n¼12)>11.8 ꢁC (n¼16) on the cooling process. All derivatives 2a
exhibited a monotropic behavior. Under optical microscope they all
exhibited typical Schlieren textures of four or/and two brushes
(Fig. 6). Furthermore, the nematic phase showed slightly homeo-
tropic domains, whereas, the smectic C phases showed no home-
otropic textures. The transition enthalpies of N-to-Iso transitions
eter. The aspect ratio between flexible alky chains and the rigid
cores was also changed. Fig. 5 showed the molecular arrangements
in 1a (n¼4) and 1b (n¼3).
2.3. Mesomorphic behavior
were relatively small,
D
H¼0.82e1.17 kJ/mol. On the other hand, all
The liquid crystalline behavior of ligands 2aeb were character-
ized and studied by differential scanning calorimetry (DSC) and
polarized optical microscope (POM). The phase transitions and
thermodynamic data are summarized in Table 4. All compounds 2a
derivatives 2b exhibited improved mesomorphic properties. The
shorter derivative (n¼3) showed monotropic smectic C phases,
while all other compounds 2b (n¼7, 8, 10, 12, 14, 16) showed
enantiotropic behavior. The four shorter derivatives (n¼3, 7, 8, 10)

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T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
Table 1
Crystallographic and experimental data for compounds 1a (n¼4) and 1b (n¼3)
Compds
1a (n¼4)
80H108N2O12Pd
1396.08
150 (1)
0.71073
1b (n¼3)
C60H56N2O10Pd
1071.47
150 (1)
0.71073
Empirical formula
Formula weight
T/K
C
ꢀ
Wavelength/A
Crystal system
Space group
Triclinic
P1
Triclinic
P1
ꢀ
a/A
9.1762 (2)
10.2898 (2)
21.4015 (5)
93.7538 (10)
98.2746 (11)
111.4061 (11)
1846.44 (7)
1
9.1373 (1)
10.9230 (1)
13.5756 (2)
85.8894 (8)
86.5565 (7)
66.8850 (8)
1242.20 (3)
1
ꢀ
b/A
ꢀ
c/A
ꢁ
ꢁ
a
/
b
/
ꢁ
/
g
3
ꢀ
U/A
Z
F (000)
744
1.256
556
1.432
Dc/Mg mꢀ3
Crystal size/mm3
Range for data collection/ꢁ
Reflection collected
Data, restraints, parameters
Independent reflection
Final R1, wR2
0.40ꢂ0.40ꢂ0.17
1.94e27.5
26,162
8440/0/430
8440 [Rint¼0.0464]
0.0342, 0.0785
0.40ꢂ0.22ꢂ0.10
1.50e27.5
23,978
5703/0/332
5703 [Rint¼0.0362]
0.0304, 0.0776
Table 2
Crystallographic and experimental data for compounds 1a and 1b
Compds
1a (n¼4)
1b (n¼3)
PdeO (1)
PdeO(1)#1
PdeN(1)
PdeN(1)#1
O(1)eC(7)
N(1)eC(1)
C(1)eC(2)
N(1)ePdeO(1)#
N(1)ePdeO(1)
N(1)#ePdeO(1)#
N(1)#ePdeO(1)
O(1)ePdeO(1)#
N(1)#ePdeN(1)
C(7)eO(1)ꢀPd
1.980 (10)
1.980 (10)
2.027 (13)
2.027 (13)
1.310 (18)
1.300 (2)
1.431 (2)
88.42 (5)
91.58 (5)
91.58 (5)
88.42 (5)
180.0 (8)
180.0 (9)
126.9 (10)
1.978 (12)
1.978 (12)
2.014 (15)
2.014 (15)
1.306 (2)
1.298 (2)
1.437 (2)
88.99 (5)
91.01 (5)
91.01 (5)
88.99 (5)
180.0 (8)
180.0 (14)
124.3 (11)
Fig. 3. Top plots: two intramolecular CHe
p
interactions in crystal 1a (n¼4); the dis-
ꢀ
tances between CeH27A .
p
were ca. 3.69 A. Bottom plots: a correlated structure
ꢀ
ꢀ
induced by intermolecular H-bonds H17A . O1¼2.64 A and H16A . O3¼2.67 A, ob-
served in 1a.
(n¼16), and they also slightly decreased with carbon lengths;
Tcl¼195.2 (n¼4)>147.8 (n¼12)>138.1 ꢁC (n¼16) on heating process.
On the other hand, the mesophase temperatures were ranged from
D
Tmesophase¼47.6 (n¼4)>28.2 (n¼10)>16.5 ꢁC (n¼16) on the cool-
ing process. The mesophase were identified as nematic and smectic
C phases. Under microscope, a focalꢀconic or Schlieren texture, as
characteristic textures of nematic or smectic C phases was ob-
served. In contrast, all complexes 1b showed enantiotropic be-
havior (Fig. 7), and they all have higher clearing temperatures than
Symmetry transformations used to generate equivalent atoms. #1ꢀx, ꢀy, ꢀz.
showed both nematic and smectic C phases, whereas, all other
longer derivatives (n¼12, 14, 16) exhibited only smectic C phases.
The clearing temperatures were all slightly higher than those of
those of complexes 1a by
D
Tcl¼35.4 (n¼8)ꢀ14.8 ꢁC (n¼14). The
clearing temperature decreased with carbon length, Tcl¼255.2
derivatives 2a by ca.
temperature range of mesophases for derivatives 2b were slightly
D
Tcl¼17.1 (n¼16)e30.0 ꢁC (n¼8). However, the
(n¼3)ꢀ159.0 ꢁC (n¼14). Interestingly, the temperature range of
compounds 1b,
DTmesophase¼64.6 (n¼16)e135.2 (n¼8) on the
wider than those of compounds 2a, ca. at
D
Tmesophase¼62.5 (n¼3)ꢀ
cooling process was much wider than those of compounds 1a
(Fig. 8). This wider mesophase temperature in compounds 1b over
27.2 ꢁC (n¼16) on cooling process. A larger core size incorporated
with a naphthalene group in compounds 2b than that of com-
pounds 2a was apparently favorable to the formation of meso-
than 1a might be attributed to the enhanced
pep interactions
resulted from incorporated naphthalene groups. The central core
size and geometry structure at palladium atom in both compounds
phases. More
by naphthalene moiety was attributed to the better mesomorphic
properties. An enthalpy of
mol for N/Iso and SmC/N (or SmC/Iso) were obtained. A similar
textures for nematic and smectic was observed under optical
microscope.
pep or CHep interactions induced or/and enhanced
1a and 1b were similar, however, the more
pep interactions fa-
DH¼0.40e1.53 and
D
H¼3.02e8.25 kJ/
vored the molecular packing in solid or LC states, facilitating or/and
stabilizing the formation of the mesophases. The typical textures
described as Schlieren domains for nematic and smectic C phases
were also confirmed. The geometry at palladium atoms in both
complexes 1aeb was close to perfect square plane However,
a slightly twisted structure and a larger dihedral angle in crystal 1b
than those of 1a were obviously more favorable to stabilize the
mesophases.
The thermal stability of compounds 1e2 (all n¼10) was also
performed by thermogravimetric analyses (TGA) under nitrogen
atmosphere, shown in Fig. 9. All four compounds showed good
thermal stability at a temperature below ca. T¼331.7 ꢁC, with
Palladium complexes derived from compounds 2aeb were
prepared and studied. All Pd compounds 1aeb were truly meso-
genic (see Table 5). Compound 1a (n¼3) was the only one, kineti-
cally unstable, showing monotropic nematic phase. All complexes
1a have much higher clearing temperatures than those their ligand
precursors 2a by
D
Tcl¼85.5 (n¼4)>41.8 (n¼10)>32.1 ꢁC (n¼16),
which was due to their larger sizes or more rigids cores. The
clearing temperature were ranged from Tcl¼195.2 (n¼4)ꢀ138.1 ꢁC

T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
8653
Fig. 4. A correlated structure induced by intermolecular H-bonds, HePd bonds and the intermolecular CHe
p
interactions observed viewed from different axes in 1b (n¼3). Top
ꢀ
ꢀ
ꢀ
plot: CeH27A .
p¼3.94 A, and bottom plot: H24A . O2¼2.52 A, H10A . Pd¼2.81 A.
ꢀ
Table 3
broad halo peak appeared at ca. 4.49 and 4.80 A was observed for
two compounds. All molecules were tilted arranged in smectic
phases. The molecular lengths of compounds 2a (n¼10) and 2b
A summary of molecular interactions observed in 1a (n¼4) and 1b (n¼3)
Compds
CHe interactions
No. of Hebonds
1a (n¼4)
CeH6A .
2
1b (n¼3)
CeH27A .
1
ꢀ
ꢀ
ꢀ
ꢀ
(n¼10) were estimated as 45.6 A and 48.1 A, respectively, by MM2
model. This might indicate that all molecules were tilted or/and the
alkoxy carbon chains were interdigitated in SmC phases.
On the other hand, both palladium complexes 1aeb (n¼10)
formed enantiotropic nematic at higher temperature and smectic
phases at lower temperature. On XRD plots, a similar diffraction
pattern with a d-spacing of 29.9 A at 150 C, and 28.2 A and 14.1 A at
140 ꢁC for compound 1a (n¼10) was obtained, which were assigned
as a nematic and a smectic of indices 001, and 002. A slightly longer
p
p
¼3.69 A
p
¼3.69 A
ꢀ
ꢀ
Bond distance, angles O1eH17A¼2.64 A
O2eH24A¼2.52 A
:C17eH17AeO1¼154.9ꢁ :C24eH24AeO2¼162.2ꢁ
ꢀ
O3eH16A¼2.67 A
:C16eH16AeO3¼145.6ꢁ
ꢀ
HePd bondings
d
PdeH10A¼2.81 A
ꢁ
ꢀ
ꢀ
ꢀ
a relative thermal stability of 1a>2a>1b>2b. The decomposition
temperatures for a 5% weight loss were listed in Table 6. The relative
order of decomposition temperature of compounds was not quite
consistent with the DSC data (Tcl¼1b>1a>2b>2a) of these two
compounds. The clearing temperature of compound 1b (n¼10) was
the highest at Tcl¼184.1 ꢁC, whereas, the compound 2a was the
lowest clearing temperature at Tcl¼114.1 ꢁC among the series.
ꢀ
d-spacing in nematic (w29.9 A) was expected than that in layered
structure (w28.2 A) due to tilted molecular arrangements in SmC
phase. Further, a diffraction pattern with a d-spacing of 29.9 A at
ꢀ
ꢀ
ꢁ
ꢁ
ꢀ
ꢀ
170 C, and 28.9 A and 14.4 A at 145 C for compound 1b (n¼10) was
ꢀ
obtained. A broad halo peak appeared at ca. 4.72 and 4.63 A was
observed for two these compounds. The intensities of diffraction
peaks in nematic phases were all much weaker than those in
smectic phases.
2.4. Powder X-ray diffractions and packing arrangements
Variable-temperature powder XRD diffraction experiments
were performed to confirm the structure of the mesophases of four
compounds 2aeb (n¼10) and 1aeb (n¼10), and a summary of
diffraction data was listed in Table 7. For example, for compounds
2a (n¼10) at 100 ꢁC a diffraction pattern with one strong peak at
3. Conclusions
Two new series of mesogenic palladium complexes 1aeb de-
rived from salicylaldimines containing terminal phenyl or naphenyl
moiety were prepared, characterized and their mesomorphic
properties were investigated. Two single crystallographic struc-
tures of compounds 1a (n¼4) and 1b (n¼3) were determined by X-
ray analysis. The formation of mesomorphic properties in palla-
dium complexes was found to be sensitive to the intermolecular
interactions of CHep interactions and H-bonds. All Schiff bases
2aeb and palladium complexes 1aeb exhibited mesomorphic
properties. Compounds 1b have a higher clearing temperature than
ꢀ
30.9 A was observed, as shown in Fig. 10. One diffraction peak at
lower angles was typically characteristics of layer structures ob-
served for a SmC phase. A diffraction peak of nematic phase for
compound 2b (n¼10) at higher temperature was not possible due
to its quite narrow range (ca.
D
TN¼2.8 ꢁC) of mesophase tempera-
ture. In contrast, a slightly larger d-spacing of 32.1 A at 130 ꢁC, as
ꢀ
expected for larger or longer structures of compound 2b (n¼10). A

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T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
Fig. 5. Molecular arrangements in 1a (n¼4) and 1b (n¼3).
those of 1a by a
D
Tcl¼35.4e14.8 ꢁC. Both H-bonds and/or
p
e
p
in-
compounds of 1,2-dialkoxybenzenes, 3,4-dialkoxynitrobenzenes
and 3,4-dialkoxyaminobenzenes were prepared by literatures’
procedures.
teractions might be quite important factors in inducing the meso-
morphic properties observed in such type of metallomesogens.
Future work might focus more on other transition metals.
4.2. 1,2-Bis(dodecyloxy)benzene
4. Experimental section
White needle crystal, yield 80%. 1H NMR (CDCl3):
ꢀCH3), 1.26e1.86 (m, 40H, ꢀCH2), 3.98 (t, 4H, ꢀOCH2), 6.88 (s, 4H,
AreH). 13C NMR (CDCl3):
14.10, 22.68, 26.05, 29.36, 29.67, 31.92,
69.24, 114.07, 120.96, 149.22.
d 0.88 (t, 6H,
4.1. General materials and methods
d
All chemicals and solvents were reagent grade from Aldrich
Chemical Co., and solvents were dried by standard techniques. 1H
and 13C NMR spectra were measured on a Bruker DRSꢀ300. DSC
thermographs were carried out on a Mettler DSCꢀ822 and cali-
brated with a pure indium sample. All phase transitions are de-
4.3. 1,2-Bis(dodecyloxy)-4-nitrobenzene
Pale yellow cotton-like crystal, yield 86%. 1H NMR (CDCl3):
d 0.88
a
scan rate of 10.0 ꢁC/min. Optical polarized
(t, 6H, ꢀCH3), 1.24e1.88 (m, 40H, ꢀCH2), 4.12 (t, 4H, ꢀOCH2), 6.79
termined by
(d, 1H, AreH, J¼7.88 Hz), 7.66 (s, 1H, AreH), 7.78 (d, 1H, AreH,
microscopy was carried out on Zeiss Axioplan 2 equipped with
a hot stage system of Mettler FP90/FP82HT. The UVevis absorption
and fluorescence spectra were obtained using a Jasco Vꢀ530 and
Hitachi Fꢀ4500 spectrometer. Elemental analyses were performed
on a Heraeus CHNeOeRapid elemental analyzer. The powder dif-
fraction data were collected from the WigglerdA beam line of the
National Synchrotron Radiation Research Center (NSRRC) with
a wavelength of 1.3263 A. 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. The
J¼7.83 Hz). 13C NMR (CDCl3):
d 14.12, 22.76, 25.89, 28.76, 29.47,
29.59, 30.89, 69.38, 108.21, 111.24, 117.58, 140.99, 148.67, 155.86.
4.4. 3,4-Bis(dodecyloxy)aniline
White pellet crystals, yield 82%. 1H NMR (CDCl3):
d 0.85 (t, 6H,
ꢀCH3), 1.26e1.79 (m, 40H, ꢀCH2), 3.56 (s, 2H, ꢀNH2), 3.89 (t, 4H,
ꢀOCH2), 6.23 (d, 1H, AreH, J¼4.66 Hz), 6.34 (s, 1H, AreH), 6.78 (d,
1H, AreH, J¼5.68 Hz).

T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
8655
Table 4
The phase transition temperatures and the enthalpiesa of compounds 2
4.5. 6-(Dodecyloxy)-2-naphthoic acid
isolated as white solids was purified by column chromatography
(SiO2) eluting with hexane. Yield 62%. 1H NMR (CDCl3):
d 0.86e0.90
The solution of 6-hydroxy-2-naphthaoic acid (5.0 g, 0.027 mol)
and KOH (3.0 g, 0.053 mol) was gently heated in 100 mL of C2H5OH/
H2O (10/1) for 30 min under nitrogen atmosphere. The solution was
then added 1-bromododecane (13.92 g, 0.056 mol), and the mix-
ture was refluxed for 24 h. The solution was neutralized with dilute
1.0 M HCl to pH equal to 6.0. The white solids were collected. The
products isolated as white crystals were obtained after recrystal-
(t, 3H, ꢀCH3, J¼6.73 Hz), 1.27e1.56 (m, 12H, ꢀCH2), 1.83e1.86 (m,
2H, ꢀCH2), 4.08e4.10 (t, 2H, ꢀOCH2, J¼6.54 Hz), 6.91 (s, 1H, AreH),
6.93e6.96 (d, 1H, AreH, J¼8.46 Hz), 7.15 (s, 1H, AreH), 7.20e7.22 (d,
1H, AreH, J¼8.93 Hz), 7.60e7.62 (d, 1H, AreH, J¼8.44 Hz),
7.77e7.79 (d, 1H, AreH, J¼8.68 Hz), 7.85e7.87 (d, 1H, AreH,
J¼8.93 Hz), 8.08e8.10 (d, 1H, AreH, J¼8.64 Hz), 8.65 (s, 1H, AreH).
13C NMR (CDCl3):14.11, 22.67, 26.10, 29.15, 29.25, 29.37, 31.83, 68.28,
106.48, 110.94, 114.18, 118.68, 120.33, 123.51,126.00, 127.16, 127.75,
131.04, 132.06, 134.98, 137.86, 157.93, 159.70, 163.25, 164.48, 195.50.
lized from CH2Cl2/CH3OH. Yield 88%. 1H NMR (CDCl3):
d 0.85e0.90
(t, 3H, ꢀCH3), 1.29e1.50 (m, 12H, ꢀCH2), 1.83e1.85 (m, 2H, ꢀCH2),
4.08e4.11 (t, 2H, ꢀOCH2), 7.14 (s, 1H, AreH), 7.18e7.20 (d, 1H, AreH,
J¼8.94 Hz), 7.23 (s, 1H, AreH) 7.73e7.75 (d, 1H, AreH, J¼8.68 Hz),
7.83e7.85 (d, 1H, AreH, J¼8.92 Hz), 8.04e8.06 (d, 1H, AreH,
4.7. (E)-4-(((3,4-Bis(dodecyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n[12)
J¼8.89 Hz), 8.59 (s, 1H, AreH). 13C NMR (CDCl3):
d 13.91, 22.55,
26.05, 29.15, 29.28, 29.35, 31.75, 68.30, 106.72, 119.97, 121.29,
124.16, 126.05, 126.85,127.85, 130.95, 131.80, 137.75, 159.51.
The mixture of 4-formyl-3-hydroxyphenyl 6-(dodecyloxy)-2-
naphthoate (0.55 g, 1.15 mmol) and 3,4-bis(dodecyloxy)aniline
(0.53 g, 1.15 mmol) was dissolved in 15 mL of hot absolute ethanol.
A few drops of glacial acetic acid were added to the mixture. Then
the solution was gently refluxed for 24 h. The solution was cooled
and the solids were collected. The product isolated as yellow solids
were obtained after recrystallization from THF/CH3OH. Yield 85%.
4.6. 4-Formyl-3-hydroxyphenyl 6-(dodecyloxy)-2-naphthoate
Under nitrogen atmosphere, the solution 6-(dodecyloxy)-2-
naphthoic acid (2.00 g, 6.0 mmol), DCC (1.51 g, 7 mmol) and 2,4-
dihydroxybenzoaldehyde (0.84 g, 6.0 mmol) was dissolved in
100 mL of dry THF, and the mixture was stirred at ice-bath tem-
perature for 30 min. The solution was then added and DMAP
(0.89 g, 7 mmol) stirred at room temperature for 24 h. The solids
were filtered off, and the solution was concentrated. The product
1H NMR (CDCl3):
d
0.87 (m, 9H, ꢀCH3), 1.25e1.47 (m, 48H, ꢀCH2),
1.78 (m, 6H, ꢀCH2), 1.83 (m, 6H, ꢀOCH2CH2), 4.01 (m, 4H, ꢀOCH2),
4.09 (t, 2H, ꢀOCH2, J¼6.45 Hz), 6.88 (m, 4H, AreH), 6.97 (s, 1H,
AreH), 7.16 (s, 1H, AreH), 7.21 (d, 1H, AreH, J¼11.25 Hz), 7.44 (d, 1H,
AreH, J¼8.98 Hz), 8.11 (d, 1H, AreH, J¼8.32 Hz), 8.12 (s, 1H, N]

8656
T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
Table 5
The phase transition temperatures and the enthalpiesa of compounds 1
Fig. 6. Optical textures observed. N phase at 109 ꢁC by 2a (n¼8, top left), SmC phase at 100 ꢁC by 2a (n¼8, top right), N phase at 138 ꢁC by 2b (n¼8, bottom left), SmC phase at 129 ꢁ
2b (n¼8, bottom right).
C

T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
8657
Fig. 7. Optical textures observed. N phase at 150 ꢁC by 1a (n¼8, top left), and SmC phase at 125 ꢁC 1a (n¼8, top right). N phase at 180 ꢁC by 1b (n¼8, bottom left) and SmC phase at
100 ꢁC by 1b (n¼8, bottom right).
100
1b (n = 10)
1a (n = 10)
2b (n = 10)
2a (n = 10)
75
50
25
0
100
200
300
400
500
600
700
o
Temperature ( C)
Fig. 9. The TGA thermographs of compounds 1e2 (all n¼10) under nitrogen gas at
a heating rate of 10.0 ꢁC minꢀ1
.
Table 6
The decomposition temperaturesa of compounds 1e2 (all n¼10) by TGA analysis
Compds
Tdec (ꢁC)
2b (n¼10)
2a (n¼10)
1b (n¼10)
1a (n¼10)
331.7
341.7
339.2
350.8
a
Temperatures taken with a 5% weight loss under nitrogen atmosphere.
CeH), 8.16 (s, 1H, AreH), 13.37 (s, 1H, AreOH). 13C NMR (CDCl3):
d
14.13, 22.71, 26.05, 26.07, 26.14, 29.17, 29.28, 29.32, 29.36, 29.38,
29.41, 29.45, 29.60, 29.62, 29.66, 29.68, 29.73, 31.94, 68.26, 69.41,
69.61, 106.46, 107.39, 110.63, 112.99, 124.02, 126.01, 127.06, 127.80,
Fig. 8. Bar graphs showing the phase behavior of compounds 1e2. All temperatures
were taken on the cooling process.

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T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
Table 7
2000
Detailed indexation by powder X-ray diffractionsa for compounds 1e2
Compd
Mesophases/temp. (ꢁC) d-Spacing obs. (Calcd.) Miller indices
29.9
1500
1000
500
0
2b (n¼10) SmC at 130
2a (n¼10) SmC at 100
1b (n¼10) N at 170
SmC at 135
32.07 (32.07)
4.60 (br)
30.89 (30.89)
4.49 (br)
29.92 (29.92)
4.69 (br)
28.89 (28.89)
14.42 (14.44)
4.66 (br)
29.92 (29.92)
4.72 (br)
28.24 (28.24)
14.07 (14.12)
4.63 (br)
001
Halo
001
Halo
Halo
001
002
4.7
Halo
1a (n¼10) N at 150
Halo
001
002
SmC at 140
0
10
20
30
2 theta
Halo
a
Temperature taken on the cooling process.
12000
8000
4000
0
28.9
131.03, 131.88, 132.06, 134.98, 137.73, 148.67, 149.87, 154.67, 159.70,
162.57,163.25, 164.95. Anal. Calcd for C65H94N2O6: C, 78.30; H, 9.75;
N, 1.52. Found: C, 78.40; H, 9.74; N, 1.33.
14.4
4.7.1. (E)-4-(((3,4-Dipropoxyphenyl)imino)methyl)-3-hydroxyphenyl
6-(dodecyloxy)-2-naphthoate 2b (n¼3). Yellow solid, yield 72%. 1H
NMR (CDCl3):
d
0.87 (t, 3H, ꢀCH3, J¼6.90 Hz), 1.05 (m, 6H, ꢀCH3),
1.26e1.37 (m, 16H, ꢀCH2), 1.49 (m, 2H, ꢀCH2), 1.85 (m, 6H, ꢀCH2),
3.98 (m, 4H, ꢀOCH2), 4.09 (t, 2H, ꢀOCH3, J¼6.54 Hz), 6.88 (m, 4H,
AreH), 6.93 (s, 1H, AreH), 7.16 (s, 1H, AreH), 7.2 (d, 1H, AreH,
J¼9.20 Hz), 7.42 (d, 1H, AreH, J¼8.41 Hz), 7.78 (d, 1H, AreH,
J¼8.66 Hz), 7.86 (d, 1H, AreH, J¼9.00 Hz), 8.10 (d, 1H, AreH,
J¼8.02 Hz), 8.60 (s, 1H, ꢀN]CH), 8.67 (s, 1H, AreH), 13.72 (s, 1H,
4.7
0
10
20
30
2 theta
AreOH) 13C NMR (CDCl3):
d 0.50, 10.52, 14.14, 22.62, 22.65, 26.11,
29.17, 29.37, 29.42, 29.60, 29.63, 29.63, 29.66, 29.68, 31.94, 66.26,
70.86, 71.10, 106.46, 107.46, 110.62, 113.01, 114.22, 117.30, 120.21,
124.12, 126.11, 127.06, 127.79, 131.03, 131.88, 132.09, 137.72, 148.61,
149.81, 154.61, 159.55, 159.57, 162.56, 164.98. Anal. Calcd for
29.9
1500
1000
500
0
C
65H94N2O6: C, 75.53%; H, 8.00; N, 2.10. Found: C, 75.71; H, 7.85; N,
1.86.
4.7.2. (E)-4-(((3,4-Bis(heptyloxy)phenyl)imino)methyl)-3-
4.69
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n¼7). Yellow solid,
yield 80%. 1H NMR (CDCl3):
d
0.89 (m, 9H, ꢀCH3),1.27e1.32 (m, 28H,
ꢀCH2), 1.49 (m, 6H, ꢀOCH2), 1.83 (m, 6H, ꢀCH2), 4.02 (m, 4H,
ꢀOCH2), 4.11 (t, 2H, ꢀOCH2, J¼6.55 Hz), 6.87 (m, 4H, AreH), 6.93 (s,
1H, AreH), 7.17 (s, 1H, AreH), 7.14 (d, 1H, AreH, J¼6.30 Hz), 7.40 (d,
1H, AreH, J¼8.45 Hz), 7.77 (d, 1H, AreH, J¼8.15 Hz), 7.86 (d, 1H,
AreH, J¼8.95 Hz), 8.11 (d, 1H, AreH, J¼8.50 Hz), 8.59 (s, 1H, ꢀN]
CeH), 8.69 (s, 1H, AreH), 13.71 (s, 1H, AreOH). 13C NMR (CDCl3):
0
10
20
30
2 theta
12000
8000
4000
0
d
13.94, 13.95, 22.53, 22.60, 29.09, 29.16, 29.27, 29.35, 29.41, 29.52,
28.2
29.54, 29.57, 29.60, 31.77, 31.86, 68.32, 68.62, 69.88, 76.69, 76.94,
77.19, 106.73, 107.93, 110.55, 112.86, 117.37, 120.11, 124.23, 126.07,
127.00, 127.89, 130.96, 131.79, 132.74, 137.73, 141.78, 148.86, 150.13,
154.10, 159.59, 162.60, 164.84. Anal. Calcd for C65H94N2O6: C, 76.98;
H, 8.92; N, 1.80. Found: C, 77.04; H, 9.06; N, 2.26.
14.1
4.7.3. (E)-4-(((3,4-Bis(octyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n¼8). Yellow solid,
yield 82%. 1H NMR (CDCl3):
d
0.88 (m, 9H, ꢀCH3), 1.28e1.45 (m,
32H, ꢀCH2), 1.49 (m, 6H, ꢀCH2CH3), 1.85 (m, 6H, ꢀCH2), 4.03 (m,
4H, ꢀOCH2), 4.11 (t, 2H, ꢀOCH2, J¼6.53 Hz), 6.86 (m, 4H, AreH),
6.93 (s, 1H, AreH), 7.12 (s, 1H, AreH), 7.22 (d, 1H, AreH, J¼6.35 Hz),
7.39 (d, 1H, AreH, J¼8.45 Hz), 7.77 (d, 1H, AreH, J¼8.65 Hz), 7.86 (d,
1H, AreH, J¼8.95 Hz), 8.12 (d, 1H, AreH, J¼8.62 Hz), 8.59 (s, 1H,
ꢀN]CeH), 8.67 (s, 1H, AreH), 13.67 (s, 1H, AreOH). 13C NMR
4.63
0
10
20
30
2 theta
Fig. 10. The powder X-ray diffractions (from top to bottom plot) by compounds: 1a
(n¼10) at 170 ꢁC and 1b (n¼10) at 135 ꢁC, 1a (n¼10) at 150 ꢁC and 1a (n¼10) at 140 ꢁ
C
(CDCl3):
d 13.94, 22.59, 26.03, 26.96, 29.16, 29.21, 29.26, 26.33,
when cooled from above their clearing temperatures.
29.41, 29.52, 29.54, 29.57, 31.78, 31.86, 68.33, 69.64, 69.91, 106.73,

T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
8659
107.96, 110.55, 112.85, 113.15, 114.85, 117.38, 120.11, 124.24, 126.07,
127.00, 130.96, 131.78, 132.74, 137.74, 141.80, 148.86, 152.14, 154.70,
159.59, 159.61, 162.59, 164.83. Anal. Calcd for C65H94N2O6: C, 77.28;
H, 9.10; N, 1.73. Found: C, 77.05; H, 8.81; N, 2.51.
C65H94N2O6: C, 77.28; H, 10.08; N, 1.61. Found: C, 76.82; H, 10.32; N,
1.41.
4.8.1. (E)-4-(((3,4-Dibutoxyphenyl)imino)methyl)-3-hydroxyphenyl
4-(dodecyloxy) benzoate 2a (n¼4). Yellow solid, yield 85%. 1H NMR
4.7.4. (E)-4-(((3,4-Bis(decyloxy)phenyl)imino)methyl)-3-
(CDCl3):
d
0.86 (t, 3H, ꢀCH3, J¼5.68 Hz), 0.98 (m, 6H, ꢀCH2),
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n¼10). Yellow
1.00e1.25 (m, 12H, ꢀCH2), 1.49e1.52 (m, 6H, ꢀCH2), 1.82 (m, 6H,
ꢀCH2), 4.02 (m, 2H, ꢀOCH2), 6.79 (d, 1H, AreH, J¼8.30 Hz), 6.86 (m,
4H, AreH), 6.95 (d, 2H, AreH, J¼8.80 Hz), 7.38 (d, 2H, AreH, 8.11,
J¼8.45 Hz), 8.11 (d, 1H, AreH, J¼8.75 Hz), 8.58 (s, 1H, ꢀN]CeH),
solid yield 82%. 1H NMR (CDCl3):
d
0.88 (m, 9H, ꢀCH3), 1.28e1.45
(m, 40H, ꢀCH2),1.49 (m, 6H, ꢀCH2CH3),1.84 (m, 6H, ꢀCH2), 4.03 (m,
4H, ꢀOCH2), 4.11 (t, 2H, ꢀOCH2, J¼6.53 Hz), 6.88 (m, 4H, AreH), 6.93
(s, 1H, AreH), 7.14 (s, 1H, AreH), 7.40 (d, 1H, AreH, J¼8.31 Hz), 7.76
(d, 1H, AreH, J¼8.18 Hz), 7.86 (d, 1H, AreH, J¼9.01 Hz), 8.12 (d, 1H,
AreH, J¼8.48 Hz), 8.60 (s, 1H, ꢀN]CeH), 8.67 (s, 1H, AreH), 13.67
13.78 (s, 1H, AreOH). 13C NMR (CDCl3):
d 13.04, 13.91, 14.15, 19.26,
22.72, 26.00, 29.11, 29.38, 29.61, 29.66, 31.32, 31.36, 31.94, 68.37,
69.06, 69.31,107.43, 110.56, 112.97, 114.16, 114.35, 117.27, 121.24,
132.37, 132.86, 141.71, 148.56, 149.81, 149.81, 154.58, 162.48, 163.69,
164.43. Anal. Calcd for C65H94N2O6: C, 74.38; H, 8.58; N, 2.17. Found:
C, 74.21; H, 8.39; N, 1.92.
(s, 1H, AreOH). 13C NMR (CDCl3):
d 13.96, 22.61, 26.04, 26.06, 29.16,
29.28, 29.35, 29.38, 29.53, 29.58, 31.86, 68.32, 69.13, 69.89, 106.72,
107.90, 110.57, 112.89, 113.14, 114.81, 120.12, 124.22, 126.08, 127.61,
127.88, 139.97, 131.80, 132.78, 137.74, 141.67, 148.87, 150.14, 159.59,
162.62,164.83. Anal. Calcd for C65H94N2O6: C, 77.83; H, 9.45; N,1.62.
Found: C, 77.81; H, 9.53; N, 1.49.
4.8.2. (E)-4-(((3,4-Bis(octyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 4-(dodecyloxy) benzoate 2a (n¼8). Yellow solid,
yield 82%. 1H NMR (CDCl3):
d
0.85 (m, 9H, ꢀCH3, J¼5.68 Hz),
4.7.5. (E)-4-(((3,4-Bis(tetradecyloxy)phenyl)imino)methyl)-3-
1.28e1.34 (m, 32H, ꢀCH2), 1.46 (m, 6H, ꢀCH2), 1.82 (m, 6H, ꢀCH2),
4.01 (m, 6H, ꢀOCH2), 6.79 (d, 1H, AreH, J¼8.01 Hz), 6.86 (m, 4H,
AreH), 6.95 (d, 2H, AreH, J¼8.88 Hz), 7.38 (d, 1H, AreH, J¼8.43 Hz),
8.11 (d, 2H, AreH, J¼8.8 Hz), 8.58 (s, 1H, ꢀN]CeH), 13.77 (s, 1H,
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n¼14). Yellow
solid, yield 81%. 1H NMR (CDCl3):
d
0.87 (m, 9H, ꢀCH3), 1.26e1.36
(m, 56H, ꢀCH2),1.47 (m, 6H, ꢀCH2), 1.83 (m, 6H, ꢀCH2), 4.03 (m, 4H,
ꢀOCH2), 4.11 (t, 2H, ꢀOCH2, J¼6.45 Hz), 6.88 (m, 4H, AreH), 6.92 (s,
1H, AreH), 7.17 (s, 1H, AreH), 7.22 (d, 1H, AreH, J¼10.28 Hz), 7.40
(d, 1H, AreH, J¼8.43 Hz), 7.77 (d, 1H, AreH, J¼8.16 Hz), 7.86 (d, 1H,
AreH, J¼8.98 Hz), 8.12 (t, 1H, AreH, J¼8.58 Hz), 8.59 (s, 1H, ꢀN]
CeH), 8.67 (s, 1H, AreH), 13.60 (s, 1H, AreOH). 13C NMR (CDCl3):
AreOH). 13C NMR (CDCl3):
d 14.08, 14.17, 22.50, 22.72, 26.32, 28.28,
28.67, 30.02, 30.12, 30.38, 30.58, 30.62,30.66, 30.68, 31.94, 69.32,
69.34, 69.62, 07.38, 110.5, 122.82, 114.15, 117.36, 121.78, 133.36,
133.80, 140.44,149.57,149.80,154.63,159.72,162.52,163.32, 164.85.
Anal. Calcd for C65H94N2O6: C, 76.05; H, 9.44; N, 1.85. Found: C,
75.89; H, 9.15; N, 1.50.
d
0.93, 13.95, 22.60, 26.03, 26.04, 29.16, 29.27, 29.28, 29.33, 29.35,
29.38, 29.52, 29.54, 29.58, 29.60, 26.45, 31.87, 68.32, 69.63, 69.90,
106.72, 107.93, 110.55, 112.86, 113.14, 114.84, 117.37, 120.11, 124.23,
126.07, 127.00, 127.89, 130.97, 131.77, 132.74, 137.73, 141.78, 148.78,
148.86, 150.14, 154.71, 159.60, 162.60, 164.84. Anal. Calcd for
4.8.3. (E)-4-(((3,4-Bis(decyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 4-(dodecyloxy) benzoate 2a (n¼10). Yellow solid,
yield 75%. 1H NMR (CDCl3):
d
0.87 (m, 9H, ꢀCH3),1.25e1.34 (m, 40H,
C
65H94N2O6: C, 78.72; H, 10.01; N, 1.43. Found: C, 78.70; H, 9.98; N,
ꢀCH2),1.48 (m, 6H, ꢀCH2),1.82 (m, 6H, ꢀCH2), 4.03 (m, 6H, ꢀOCH2),
6.80 (d, 1H, AreH, J¼8.57 Hz), 6.86 (m, 4H, AreH), 6.95 (d, 2H,
AreH, J¼8.82 Hz), 7.37 (d, 1H, AreH, J¼8.44 Hz), 8.11 (d, 2H, AreH,
J¼8.80 Hz), 8.58 (s, 1H, ꢀN]CeH), 13.76 (s, 1H, AreOH). 13C NMR
2.00.
4.7.6. (E)-4-(((3,4-Bis(hexadecyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 2b (n¼16). Yellow
(CDCl3): d 14.14, 22.71, 26.00, 29.11, 29.28, 29.33, 29.38, 29.45,
solid, yield 81%. 1H NMR (CDCl3):
d
0.87 (m, 9H, ꢀCH3), 1.26e1.34
29.58, 29.61, 31.94, 37.69, 69.63, 107.40, 110.57, 112.98, 114.17, 117.25,
159.56, 162.49, 163.70, 164.40. Anal. Calcd for C65H94N2O6: C, 76.71;
H, 9.78; N, 1.72. Found: C, 76.58; H, 9.75; N, 1.59.
(m, 64H, ꢀCH2), 1.50 (m, 6H, ꢀCH2), 1.83 (m, 6H, ꢀOCH2), 4.03 (m,
4H, ꢀOCH2), 4.11 (t, 2H, ꢀOCH2, J¼6.53 Hz), 6.88 (m, 4H, AreH), 6.93
(s, 1H, AreH), 7.17 (s, 1H, AreH), 7.21 (d, 1H, AreH, J¼8.99 Hz), 7.40
(d, 1H, AreH, J¼8.44 Hz), 7.77 (d, 1H, AreH, J¼8.66 Hz), 7.87 (d, 1H,
AreH, J¼8.99 Hz), 8.10 (d, 1H, AreH, J¼8.45 Hz), 8.59 (s, 1H, ꢀN]
CeH), 8.67 (s, 1H, AreH), 13.65 (s, 1H, AreOH). 13C NMR (CDCl3):
4.8.4. (E)-4-(((3,4-Bis(tetradecyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 4-(dodecyloxy)benzoate 2a (n¼14). Yellow solid,
yield 86%. 1H NMR (CDCl3):
d
0.88 (m, 9H, ꢀCH3, J¼5.75 Hz),
d
13.95, 22.60, 26.04, 29.16, 29.27, 29.34, 29.36, 29.38, 29.52, 29.54,
1.27e1.36 (m, 56H, ꢀCH2), 1.47 (m, 6H, ꢀCH2), 1.82 (m, 6H, ꢀOCH2),
4.03 (m, 6H, ꢀOCH2), 6.80 (d, 1H, AreH, J¼8.35 Hz), 6.87 (m, 4H,
AreH), 6.95 (d, 2H, AreH, J¼8.74 Hz), 7.37 (d, 1H, AreH, J¼8.45 Hz),
8.11 (d, 2H, AreH, J¼8.73 Hz), 8.58 (s, 1H, ꢀN]CeH), 13.76 (s, 1H,
AreOH). 13C NMR (CDCl3): 13.96, 22.60, 25.95, 26.04, 29.10, 29.36,
29.39, 29.49, 29.52, 29.58, 29.61, 29.65, 31.88, 68.41, 69.62, 69.89,
107.92, 110.51, 112.87, 113.12, 114.42, 114.82, 117.26, 121.48, 132.23,
132.69, 141.79, 148.84, 150.13, 154.71, 159.60, 163.73, 164.25. Anal.
Calcd for C65H94N2O6: C, 77.79; H, 10.34; N, 1.51. Found: C, 77.64; H,
10.48; N, 1.46.
29.58, 29.60, 29.65, 31.87, 66.32, 69.64, 69.90, 106.73, 107.94, 110.56,
112.86, 113.14, 114.84, 117.37, 120.11, 124.24, 126.07, 127.00, 130.96,
131.78, 132.74, 137.73, 141.76, 148.86, 150.14, 154.71, 159.60, 162.60,
164.83. Anal. Calcd for C65H94N2O6: C, 79.10; H, 10.25; N, 1.36.
Found: C, 78.96; H, 10.26; N, 1.22.
4.8. (E)-4-(((3,4-Bis(dodecyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 4-(dodecyloxy)benzoate 2a (n[12)
Yield 78%. 1H NMR (CDCl3):
d
0.87 (m, 9H, ꢀCH3), 1.26e1.35 (m,
48H, ꢀCH2), 1.46 (m, 6H, ꢀCH2), 1.81 (m, 6H, ꢀCH2), 4.03 (m, 6H,
ꢀOCH2), 6.80 (d, 1H, AreH, J¼8.41 Hz), 6.86 (m, 4H, AreH), 6.95 (d,
2H, AreH, J¼8.81 Hz), 7.37 (d, 1H, AreH, J¼8.42 Hz), 8.11 (d, 2H,
4.8.5. (E)-4-(((3,4-Bis(hexadecyloxy)phenyl)imino)methyl)-3-
hydroxyphenyl 4-(dodecyloxy)benzoate 2a (n¼16). Yellow solid,
yield 88%. 1H NMR (CDCl3):
d
0.86 (m, 9H, ꢀCH3),1.24e1.34 (m, 64H,
AreH, J¼8.80 Hz), 8.57 (s, 1H, ꢀN]CeH), 13.76 (s, 1H, AreOH). 13
C
ꢀCH2),1.46 (m, 6H, ꢀCH2),1.80 (m, 6H, ꢀCH2), 4.01 (m, 6H, ꢀOCH2),
6.79 (d, 1H, AreH, J¼8.51 Hz), 6.84 (m, 4H, AreH), 6.88 (d, 2H,
AreH, J¼8.35 Hz), 7.39 (d, 1H, AreH, J¼8.50 Hz), 8.11 (d, 2H, AreH,
J¼8.89 Hz), 8.59 (s, 1H, ꢀN]CeH), 13.77 (s, 1H, AreOH). 13C NMR
NMR (CDCl3):
d 13.94, 2.59, 22.70, 25.94, 26.02, 26.16, 29.09, 29.26,
29.28, 29.37, 29.48, 29.51, 29.63, 29.68, 31.86, 31.93, 68.24, 68.42,
69.63, 69.90, 106.44, 107.93, 110.51, 110.65, 112.29, 113.13, 114.43,
114.84, 120.15, 126.11, 127.01, 131.00, 131.82, 132.30, 132.67, 141.80,
148.83, 150.12, 159.62, 162.54, 163.41, 163.74, 164.11. Anal. Calcd for
(CDCl3): d 14.14, 22.71, 25.99, 26.05, 29.10, 29.27, 29.31, 29.37, 29.39,
29.46, 29.57, 29.60, 29.67, 29.69, 29.74, 31.94, 68.37, 69.36, 69.62,

8660
T.-M. Liu et al. / Tetrahedron 71 (2015) 8649e8660
107.38, 110.58, 112.96, 114.15, 114.35, 114.45, 117.26, 121.24, 132.38,
132.48,132.79,134.94,141.44,148.56,149.80,149.80,154.53,159.56,
162.49, 163.69, 164.44. Anal. Calcd for C65H94N2O6: C, 78.24; H,
10.57; N, 1.43. Found: C, 78.05; H, 10.44; N, 2.16.
4.10.1. Palladium complex of (E)-4-(((3,4-dibutoxyphenyl)imino)
methyl)-3-hydroxyphenyl 4-(dodecyloxy)benzoate 1a (n¼4). Yellow
orange solid, yield 72%. Anal. Calcd for C80H108N2O12Pd: C, 68.82; H,
7.80. Found: C, 68.82; H, 7.49.
4.9. Palladium complexes of (E)-4-(((3,4eBis(dodecyloxy)
phenyl)imino)methyl)-3-hydroxyphenyl 6-(dodecyloxy)-2-
naphthoate 1b (n[12)
4.10.2. Palladium complex of (E)-4-(((3,4-bis(octyloxy)phenyl)imino)
methyl)-3-hydroxy phenyl 4-(dodecyloxy)benzoate 1a (n¼8). Yellow
orange solid, yield 72%. Anal. Calcd for C96H140N2O12Pd: C, 71.15; H,
8.71. Found: C, 70.69; H, 8.99.
The mixture of 6-dodecyloxynaphthalene-2-carboxylic acid-4-
[(3,4-didodecyloxyphenyl imino)methyl]-3-hydroxyphenyl ester
(0.49 g, 5.11ꢂ10ꢀ4 mol) and Pd(OAc)2 (0.054 g, 2.43ꢂ10ꢀ4 mol)
dissolved in 25 mL absolute ethanol was refluxed for 24 h. The
solution was concentrated under reduced pressure, and the prod-
ucts isolated as golden yellow solids were obtained after recrys-
tallized from CH2Cl2/CH3OH. Yield 81%. Anal. Calcd for
4.10.3. Palladium complex of (E)-4-(((3,4-bis(decyloxy)phenyl)imino)
methyl)-3-hydroxy
(n¼10). Yellow orange solid, yield 78%. Anal. Calcd for
104H156N2O12Pd: C, 72.09; H, 9.07. Found: C, 71.79; H, 9.22.
phenyl
4-(dodecyloxy)benzoate
1a
C
4.10.4. Palladium complex of (E)-4-(((3,4-bis(tetradecyloxy)phenyl)
imino)methyl)-3- hydroxyphenyl 4-(dodecyloxy)benzoate 1a
(n¼14). Yellow orange solid, yield 83%. Anal. Calcd for
120H188N2O12Pd: C, 73.64; H, 9.81. Found: C, 73.70; H, 9.80.
C
120H176N2O12Pd: C, 74.10; H, 9.03; N. Found: C, 74.26; H, 9.03.
MSyFAB: calcd for [M]þ, C120H176N2O12Pd,1944.23; found 1944.23.
C
4.9.1. Palladium complex of (E)-4-(((3,4-dipropoxyphenyl)imino)
methyl)-3-hydroxy
(n¼3). Yellow orange solid, yield 73%. Anal. Calcd for
84H104N2O12Pd: C, 70.06; H, 7.28; N, 1.95. Found: C, 69.99; H, 7.25;
phenyl
6-(dodecyloxy)-2-naphthoate
1b
4.10.5. Palladium complex of (E)-4-(((3,4-bis(hexadecyloxy)phenyl)
imino)methyl)-3- hydroxyphenyl 4-(dodecyloxy)benzoate 1a
(n¼16). Yellow orange solid, yield 81%. Anal. Calcd for
C128H204N2O12Pd: C, 74.29; H, 9.94. Found: C, 74.04; H, 9.81.
C
N, 1.32.
4.9.2. Palladium complex of (E)-4-(((3,4-bis(heptyloxy)phenyl)imino)
methyl)-3-hydroxy
(n¼7). Yellow orange solid, yield 70%. Anal. Calcd for
100H136N2O12Pd: C, 72.15; H, 8.24; N, 1.68. Found: C, 71.12; H, 8.33;
phenyl
6-(dodecyloxy)-2-naphthoate
1b
Acknowledgements
C
We thank the Ministry of Science and Technology, Taiwan, ROC
(MOST 103-2113-M-008-002) for generous support of this work.
N, 2.34.
4.9.3. Palladium complex of (E)-4-(((3,4-bis(octyloxy)phenyl)imino)
methyl)-3-hydroxy
(n¼8). Yellow orange solid, yield 65%. Anal. Calcd for
104H144N2O12Pd: C, 72.59; H, 8.44; N,1.63. Found: C, 72.60; H, 8.55;
phenyl
6-(dodecyloxy)-2-naphthoate
1b
References and notes
C
1. Donnio, B.; Guillon, D.; Deschenaux, R.; Bruce, D. W. In Comprehensive Co-
ordination Chemistry II; McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford (,
2003; pp 357e627.
N, 1.52.
2. (a) Molochko, V. A.; Rukk, N. S. Russ. J. Coord. Chem. 2000, 26, 829e846; (b)
Binnemans, K.; Gorller-Walrand, C. Chem. Rev. 2002, 102, 2303e2346; (c)
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Chem. Commun. 2011, 14, 606e612; (b) Bhattacharjee, C. R.; Das, G.; Mondal, P.;
Prasad, S. ,K.; Rao, D. S. S. Liq. Cryst. 2011, 38, 615e623.
4.9.4. Palladium complexes of (E)-4-(((3,4-bis(decyloxy)phenyl)im-
ino)methyl)-3-hydroxyphenyl
(n¼10). Yellow orange solid, yield 69%. Anal. Calcd for
112H160N2O12Pd: C, 73.39; H, 8.80; N, 1.53. Found: C, 73.64; H, 9.05;
6-(dodecyloxy)-2-naphthoate
1b
C
N, 2.27.
5. (a) Mocanu, A. S.; Ilis, M.; Dumitrascu, F.; Ilie, M.; Circu, V. Inorg. Chim. Acta
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D.; Paul, M. K.; Francis, T. Liq. Cryst. 2009, 36, 409e423; (d) Caruso, U.; Diana, R.;
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1915e1920.
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4.9.5. Palladium complexes of (E)-4-(((3,4-bis(tetradecyloxy)phenyl)
imino)methyl)-3-hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 1b
(n¼14). Yellow orange solid, yield 75%. Anal. Calcd for
C
128H192N2O12Pd: C, 74.73; H, 9.41; N, 1.36. Found: C, 75.04; H, 9.31;
N, 2.18.
4.9.6. Palladium complexes of (E)-4-(((3,4-bis(hexadecyloxy)phenyl)
imino)methyl)-3-hydroxyphenyl 6-(dodecyloxy)-2-naphthoate 1b
(n¼16). Yellow orange solid, yield 77%. Anal. Calcd for
C
136H208N2O12Pd: C, 75.29; H, 9.66; N, 1.29. Found: C, 75.22; H,
9.62; N, 1.10.
4.10. Palladium complex of (E)-4-(((3,4-bis(dodecyloxy)phe-
nyl)imino)methyl)-3-hydroxy phenyl 4-(dodecyloxy)benzoate
1a (n[12)
12. (a) Chakraborty, L.; Chakraborty, N.; Laskar, A. R.; Paul, M. K.; Rao, N. V. S. J. Mol.
Struc 2011, 1002, 135e144; (b) Jung, B. M.; Huang, Y. D.; Chang, J. Y. Liq. Cryst.
2010, 37, 85e92.
Yellow orange solid, yield 80%. Anal. Calcd for C112H172N2O12Pd:
C, 72.91; H, 9.40; N. Found: C, 72.63; H, 9.47. MSyFAB: calcd for
[M]þ, C112H172N2O12Pd, 1844.19; found 1844.21.
13. Prajapati, A. K.; Bonde, N. Liq. Cryst. 2006, 33, 1189e1197.