Preparation, characterization and mesomorphic properties of nickel and copper complexes derived from N,N′-bis[3-(3′,4′-dialkoxyphenyl)-3-oxopropenyl] ethylenediamine

Article abstract of DOI:10.1039/a803603i

The preparation, characterization and mesomorphic properties of copper and nickel complexes derived from N,N′-bis[3-(3′,4′-dialkoxyphenyl)-3-oxopropenyl] ethylenediamine are reported. Liquid crystalline behavior for these structurally similar complexes wa

Full text of DOI:10.1039/a803603i

J O U R N A L O F
Preparation, characterization and mesomorphic properties of nickel
and copper complexes derived from N,N∞-bis[3-(3∞,4∞-
dialkoxyphenyl)-3-oxopropenyl]ethylenediamine
Chung K. Lai,* Yung-Shyen Pang and Chun-Hsien Tsai
C H E M I S T R Y
Department of Chemistry, National Central University, Chung-Li, Taiwan, ROC
Received 14th May 1998, Accepted 24th September 1998
The preparation, characterization and mesomorphic properties of copper and nickel complexes derived from N,N∞-
bis[3-(3∞,4∞-dialkoxyphenyl)-3-oxopropenyl]ethylenediamine are reported. Liquid crystalline behavior for these
structurally similar complexes was found to be strongly dependent both on the number of sidechains and metal
centers incorporated. Nickel complexes with four or six alkoxy sidechains exhibited columnar phases. However,
nickel complexes with two alkoxy sidechains and all copper complexes regardless the numbers of the sidechains
were not liquid crystalline. The structure of the mesophases was confirmed as columnar hexagonal (Col ) by powder
h
XRD diffraction. The data that the copper complexes have slightly lower isotropic temperatures than the analogous
nickel complexes suggested that the lack of liquid crystallinity for the copper complexes may be attributed to weaker
molecular interactions. The results also indicated that nickel complexes with four sidechains showed a wider range
of mesophase temperature than complexes with six sidechains.
molecular layers is extremely critical in the formation of
columnar phases since the induction of the mesophase is
mainly controlled by a delicate balance of intermolecular
interactions.
Herein we report the preparation, characterization and
mesomorphic properties of three series of copper and nickel
complex analogues derived from N,N∞-bis[3-(3∞,4∞-dialkoxy-
phenyl)-3-oxopropenyl]ethylenediamine. Of these, nickel com-
plexes 2 and 3 exhibited columnar hexagonal phases, and
copper complexes were not liquid crystalline.
Introduction
Numerous metallomesogenic compounds with unique
geometries and molecular shapes have been generated by
incorporation1 of a metal center or metal centers into organic
moieties. In general the geometry of the complex is often
determined by the metal center incorporated and the organic
chelating ligand, and it can vary from square-planar to tetra-
hedral structures for complexes2 with coordination numbers
of four. Square-planar (i.e. Cu2+, Ni2+, Pd2+, Pt2+, Zn2+)
and square-pyramidal geometries (FeCl2+, VO2+) generally
give rise to liquid crystals, whereas tetrahedral geometries are
often not mesomorphic. Some of these materials have been
extensively studied as potential candidates in terms of appli-
cations and all the related physical properties may originate
from the rich electronic configuration of the metal centers.
Incorporation of a metal center can often induce the
formation of mesophases by a non-mesogenic organic ligand,
and this differentiation in mesomorphic properties is generally
attributed to the change of molecular shape and/or intermol-
ecular interaction. On the other hand the mesomorphic
properties may be totally lost upon incorporation of a metal
ion.
Results and discussion
Synthesis
The synthetic pathways to copper and nickel complexes 1, 2
and 3 are summarized in Scheme 1. The preparation of 4-
alkoxylacetophenones, 3,4-dialkoxyacetophenones and 3,4,5-
trialkoxyacetophenones were via literature procedures.4 The
sodium salts of alkoxylphenyl-3-oxo-3-phenylpropionaldehyde
derivatives were obtained by the Claisen formylation5 reaction
of the appropriate acetophenone, ethyl formate and sodium
metal dispersed in diethyl ether. The isolation of the neutral
forms of alkoxylphenyl-3-oxo-3-phenylpropionaldehydes was
not attempted owing to their relatively low thermal stability.
The ethylenediamine Schiff bases; N,N∞-bis[3-(3∞,4∞-dialkoxy-
phenyl)-3-oxopropenyl]ethylenediamines were obtained as
light yellow solids by reaction of the freshly prepared sodium
salts with ethylenediamine in refluxing dried dichloromethane
in high yields. The reaction9 of Schiff bases with copper()
acetate monohydrate or nickel() acetate tetrahydrate in
In previous studies3 we demonstrated the formation of
mesophases by use of a b-enaminoketonate framework as the
core group in which the better planar core based on b-
enaminoketonato instead of b-diketonato structures was
applied to induce the mesophases. The separation between
H
H
N
O
N
O
refluxing
THF–methanol
produced
the
complexes.
M
Recrystallization twice from ethyl acetate or THF–methanol
gave yellow solids for the nickel complexes and green–gray
solids for copper complexes.
These Schiff base derivatives were characterized by 1H and
13C NMR spectroscopy. Schiff bases can potentially exist
possibly in three different keto–enol tautomeric6 forms; A, B
X
X
Y
Y
RO
OR
and C (Fig. 1). The 1H NMR data in CDCl , e.g., for 5 (n=
3
M = Cu, Ni; R = (CH2)nH
1 X = Y = H
2 X = OR; Y = H
3 X = Y = OR
16) showed three characteristic peaks at d 5.64, 6.75 and 10.19,
assigned to olefinic methine H (KCHLCK), aldehyde H
(KCHLNK) and imine H (KCLNHK). In addition, the prefer-
ence for the tautomeric A structure was also indicated by two
J. Mater. Chem., 1998, 8, 2605–2610
2605

OR
HO
RO
d
RO
O
O
e
c
OR
OR
X
RO
RO
RO
RO
Y
e
e
O
O
O
ONa
f
b
X
X
OR
RO
RO
RO
Y
RO
Y
OH
g
OH
O
O
N
N
N
O
M
HN
O
Y
Y
a
RO
RO
OR
X
X
RO
RO
M = Cu, Ni
1 X = Y = H
2 X = OR; Y = H
3 X = Y = OR
OMe
4 X = Y = H
5 X = OR; Y = H
6 X = Y = OR
O
Scheme 1 Reagents and conditions: a, KOH (2.0 equiv.), refluxing in THF–H O (9/1), 12 h; b, CH Li (1.1 equiv.), stirred in dried THF at 0 °C;
2
3
then at RT, 12 h. c, CH COCl (1.1 equiv.), AlCl (3.0 equiv.), stirred in CH Cl at 0 °C, then at RT, 8 h; d, RBr (1.1 equiv.), K CO (3.0 equiv.),
3
3
2
2
2
3
refluxing in Me CO, 18 h; e, ethyl formate (4.5 equiv.), Na (3.0 equiv.), stirred in Et O at RT, 8 h; f, NH (CH ) NH (0.55 equiv.), CH CO H
(3 drops), refluxing in CH Cl , 12 h; g, M(OAc) (1.1 equiv.); MLCu, Ni, refluxing in THF–CH OH, 12 h.
2
2
2
2 2
2
3
2
2
2
2
3
characterteristic peaks at d 189.63 and 153.73 in the 13C NMR
spectrum. Copper (d9) compounds, which are paramagnetic,
displayed only broad alkoxy signals in the 1H and 13C NMR
spectra. However, the nickel complexes showed sharp signals,
also indicating the diamagnetic configuration. Elemental
analysis confirmed the purity of the complexes.
H
H
H
H
H
O
O
OH
OH
HN
HN
N
N
Mesomorphic properties
H
The liquid crystalline behavior for the metal complexes was
studied by thermal analysis (DSC) and polarized optical
microscopy. Nickel complexes exhibited columnar phases while
copper complexes formed crystalline phases. Phase transitions
and thermodynamic data for these metal complexes were
summarized in Table 1. The nickel complexes 2 and 3 with
four and six alkoxy sidechains exhibited enantiotropic liquid
crystalline behavior, whereas complexes 1 with two sidechains
were not liquid crystalline.
This dependence of sidechain density has been commonly
observed in other columnar phases.4a–c,7c Two transitions of
crystal-to-columnar (KACol) and columnar-to-isotropic
(ColAI) were typically observed in all nickel derivatives. The
molecular shapes of these metal complex are roughly half-
disc, and the correlated columnar mesophases are formed by
shape effects and dative interaction between neighboring com-
plexes. Two molecules rotated by 180° are stacked in an
antiparallel organization7 within columns.
H
H
keto (A)
enol (B)
H
H
H
OH
O
N
HN
H
keto-enol (C)
DSC data showed that the crystal-to-mesophase transitions,
for example, for nickel complexes 2, were observed in the
Fig. 1 Three structures of keto-enol tautomeric forms for
enaminoketone derivatives.
2606
J. Mater. Chem., 1998, 8, 2605–2610

Table 1 Phase behaviora of metal complexes, 1, 2 and 3
n
108.6 (40.0)
1
Ni
Cu
Ni
8
16
8
K
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
,bbb)
65.3 (41.3)
113.5 (85.8)
K
,bbb)
98.0 (85.3)
105.3 (30.4)
K
,bbb)
54.1 (31.4)
100.1 (73.9)
16
10
12
14
16
18
10
12
16
14
16
14
16
K
,bbb)
85.6 (88.1)
110.0 (20.4)
2
K
,bbb)
105.7 (20.9)
57.7 (2.84)
108.5 (13.4)
K
K
K
K
Col
Col
Col
Col
K
,bbb)
,bbb)
h
h
h
h
54.4 (2.64)
105.9 (13.4)
62.9 (6.00)
105.6 (12.0)
,bbb)
,bbb)
58.8 (6.03)
100.1 (11.5)
66.8 (5.90)
100.5 (5.83)
,bbb)
,bbb)
59.3 (6.50)
88.9 (6.40)
73.4 (14.9)
102.1 (7.49)
,bbb)
,bbb)
63.5 (7.25)
93.1 (7.60)
93.9 (40.0)
Cu
,bbb)
60.1 (45.6)
Fig. 2 Bar graph showing the phase behavior of the nickel complexes
(2 and 3); n is the carbon number of the sidechains.
89.6 (36.9)
K
,bbb)
75.7 (57.2)
88.9 (34.1)
sidechains, and only a crystal-to-isotropic (KAI) transition
was observed. Such drastic change in mesomorphic properties
due to incorporation of different metals has also been observed
in other systems,1a and can be due to many factors. The lack
of liquid crystallinity is generally believed to be attributed to
weaker interaction between the copper complexes, and this
suggestion was indicated by the fact that the clearing tempera-
tures of the copper complexes were slightly lower than their
nickel analogues. However, ca. 2–3 times larger enthalpies
were observed for the crystal-to-isotropic transitions in the
copper relative to the nickel complexes.
K
,bbb)
74.0 (34.0)
70.1 (3.55)
75.7 (5.45)
3
Ni
K
K
Col
Col
K
,bbb)
,bbb)
h
h
56.7 (3.71)
66.7 (5.16)
64.5 (1.60)
70.6 (2.13)
,bbb)
,bbb)
50.3 (1.54)
62.5 (2.90)
71.0 (16.5)
Cu
,bbb)
61.3 (16.5)
44.8 (14.5)
K
,bbb)
<20.0
Copper and nickel complexes of similar structures derived
from imineketone derivatives with six alkoxy sidechains
reported by Swager’s group7b were found to form hexagonal
disordered columnar phases. Detailed comparison of DSC
data for these two types of metal complexes showed that all
imineketone-derived complexes had higher isotropic points
and much larger enthalpies (2–4 times) of the crystal-to-
isotropic transitions than iminealdehyde-derived homologues.
These observations were rationalized in that the molecular
interactions in columnar arrangements for imineketone-
derived complexes should be much better or/and stronger
owing to the presence of terminal methyl groups. On the
other hand molecular interactions in iminealdehyde-derived
complexes are much weaker than in imineketone-derived com-
plexes,9 and only little energy was needed to overcome such a
small energy barrier as to pass into the liquid phase upon
heating. These results also indicated that complexes without
terminal tetrahedral methyl groups in iminealdehyde-derived
an Represents the number of carbons in the alkoxy chain. K=crystal
phase; Col =columnar hexagonal phase; I=isotropic. The transition
h
temperatures (°C) and enthalpies (in parenthesis, kJ mol) are
determined by DSC at a scan rate of 10.0 °C min−1.
temperature range 58.0–73.0 °C on heating with the magnitude
of transition enthalpies ranging from 2.84 to 14.9 kJ mol−1,
and isotropic points were all in the range 109.0–101.0 °C with
a relatively large enthalpy (5.83–13.4 kJ mol−1). The relatively
large enthalpies indicated that the mesophases were in a highly
ordered state.8 Similar thermal data were observed for nickel
complexes 3. Increasing the carbon length in the alkoxy
sidechains decreased the clearing temperature, mainly due to
the greater dispersive forces associated with the longer alkoxy
chains. The dependence of mesophase formation on the side-
chain density was also studied. Increasing the sidechain num-
bers of the nickel complexes from four (2) to six (3) increased
the melting temperatures and decreased the clearing tempera-
tures. On the other hand the temperature range of the meso-
phase was decreased from 28.7–51.0 °C for 2 to 5.6–6.1 °C for
3, as shown in Fig. 2. These complexes have clearing tempera-
tures relatively lower than most metallomesogenic complexes.
Under a polarized optical microscope on very slow cooling
from the isotropic point a mosaic texture was observed for a
thin layer of samples between two glass plates, whereas,
textures more like focal-conic with a large area of uniform
homeotropic alignment was observed with thicker samples.
Surprisingly, none of the copper complexes displayed any
mesomorphic properties regardless of the numbers of the
materials preferred to form ordered hexagonal phases (Col
)
ho
over hexagonal disordered phases (Col ) in imineketone-
hd
˚
derived complexes. The core–core distance was 3.68 A (2, M=
Cu, n=12), which is close to stacking distance in imineketone-
˚
derived complexes (3.60 A).7b
The assignment of a columnar hexagonal phase was
confirmed by X-ray powder diffraction data. A summary of
the diffraction peaks and lattice constants for the nickel
complexes 2 and 3 is given in Table 2. For example, as shown
in Fig. 3, nickel complex 2 (n=12) displays a diffraction
pattern of a two-dimensional hexagonal lattice with one intense
˚
peak and two weak peaks at 35.09, 20.34 and 17.49 A at 80 °C.
This type of diffraction pattern is characteristic of a hexagonal
J. Mater. Chem., 1998, 8, 2605–2610
2607

Table 2 Variable-temperature XRD diffraction data for nickel()
complexes 2 and 3
for many disordered Col systems. The temperature depen-
dence of the lattice parameters in liquid crystals was also
h
studied. We found that the low-angle reflection generally
Lattice
d-Spacing/
A
obs. (calc.)
shifted to lower d-spacing at lower temperatures (i.e. d=
˚
spacing/
Miller
indices
˚
˚
˚
40.51 A at 80 °C and d=41.01 A at 104 °C for complex 2; n=
12). The hexagonal lattices are also well correlated with
increasing side chain lengths.
Complex
Mesophase
A
n
12
2
Col
80 °C
40.51
41.01
35.09 (35.09)
20.34 (20.26)
17.49 (17.54)
4.47 (br)
(100)
(110)
(200)
h
h
Conclusion
We have prepared three series of copper and nickel complexes
derived from N,N∞-bis[3-(3∞,4∞-dialkoxyphenyl)-3-oxoprop-
enyl]ethylenediamine. Liquid crystalline behavior was found
to be controlled by sidechain density and/or metal centres
incorporated. Nickel complexes with four or six sidechains
exhibited columnar hexagonal phases, and complexes with
four sidechains showed a much wider range of mesophase
than complexes with six sidechains. However, nickel complexes
with two sidechains and all copper complexes, regardless of
the number of sidechains, were non-mesomorphic. This differ-
ence might be attributed to the greater degree of molecular
interaction in nickel than in copper complexes.
3.68
Col
104 °C
35.52 (35.52)
20.55 (20.51)
17.97 (17.76)
4.53 (br)
(100)
(110)
(200)
3.54
14
16
Col
Col
90 °C
80 °C
42.78
49.32
37.05 (37.05)
21.83 (21.39)
18.64 (18.52)
4.78 (br)
42.71 (42.71)
24.57 (24.66)
21.23 (21.35)
4.63 (br)
(100)
(110)
(200)
h
(100)
(110)
(200)
h
3.89
18
Col
57 °C
49.16
42.57 (42.57)
24.80 (24.58)
21.39 (21.29)
17.53
(100)
(110)
(200)
h
Experimental
All chemicals and solvents were reagent grade from Aldrich
Chemical Co. and used without further purification. The
solvents were dried by standard techniques. 1H and 13C NMR
spectra were measured on a Bruker DRS-200. DSC thermo-
graphs were carried out on a Perkin-Elmer DSC-7 and cali-
brated with a pure indium sample. All phase behaviors are
determined at a scan rate of 10.0 °C min−1. Optical polarized
microscopy was carried out on Nikkon MICROPHOT-FXA
with a Mettler FP90/FP82HT hot stage system. X-Ray powder
diffraction ( XRD) studies were performed on an INEL MPD-
diffractometer with a 2.0 kW Cu-Ka X-ray source equipped
with an INEL CPS-120 position sensitive detector and a
variable temperature capillary furnace with an accuracy of
0.10 °C in the vicinity of the capillary tube. The detector
was calibrated using mica and silicon standards. The powder
samples were charged in Lindemann capillary tubes (80 mm
long and 0.01 mm thickness) from Charles Supper Co. with a
inner diameter of 0.10 or 0.15 mm. The sample was heated
above the isotropic temperature and allowed to stay at that
temperature for 10 min. The sample was then cooled at a rate
of 5.0 °C min−1 to the appropriate temperature and the
diffraction data collected. Elemental analyses for carbon,
hydrogen, and nitrogen were conducted on a Heraeus CHN-
O-Rapid elemental analyzer, and the results are listed in
Table 3. The compounds of 1,2-dialkoxybenzenes, 4-alkoxy-
acetophenones, 3,4-dialkoxyacetophenones, methyl 3,4,5-trial-
koxybenzoate esters, 3,4,5-trialkoxybenzoic acids and 3,4,5-
trialkoxyacetophenones were prepared according to literature
procedures.5,7
4.27 (br)
3.96
38.25 (38.25)
19.16 (19.13)
16.40
4.59 (br)
3.32
40.33 (40.33)
23.30 (23.28)
20.25 (20.16)
4.45 (br)
3
14
16
Col
Col
60 °C
57 °C
44.14
46.57
(100)
(200)
h
(100)
(110)
(200)
h
3.70
4-Hexadecyloxyacetophenone
White crystals, yield 85%. 1H NMR (CDCl ): d 0.83(t, CH ,
Fig. 3 Powder X-ray diffraction pattern of the columnar hexagonal
3
3
phase (Col ) at 80 °C for nickel complexes 2 (n=12).
3H), 1.24–1.81(m, CH , 28H), 2.45(s, COCH , 3H), 3.93(t,
h
2
3
OCH , 2H), 6.84(d, C H , 2H), 7.84(d, C H , 2H). 13C
2
6
4
6 4
NMR (CDCl ): d 13.97, 22.56, 25.87, 26.07, 29.00, 29.25,
29.45, 31.76, 68.10(OCH ), 113.98(C3, C5), 129.99(C2, C6),
130.39(C1), 163.01(C4), 196.37(CLO).
columnar (Col ) phase with a d-spacing ratio of 1, (1/3)1/2
3
h
and (1/4)1/2, corresponding to Miller indices (100), (110) and
2
(200), respectively. This corresponds to an intercolumnar
˚
distance (a parameter of the hexagonal lattice) of 40.51 A.
1,2-Dihexadecyloxybenzene
An additional weak halo peak at medium angle
˚
(d-spacing#4.47 A) was observed for most complexes. The
White crystals, yield 92%. 1H NMR (CDCl ): d 0.83(t, CH ,
3
3
˚
presence of a distinct peak at ca. 3.68 A indicated a relatively
6H), 1.24–1.86(m, CH , 56H), 3.94(t, OCH , 4H), 6.86(s,
2
2
ordered mesophase which is consistent with DSC analysis of
large enthalpies for the columnar-to-isotropic transition. This
peak reflects a more regular period within the columns than
C H , 4H). 13C NMR (CDCl ): d 14.10, 22.68, 26.05, 29.36,
29.44, 29.70, 30.89, 31.92, 69.28, 114.13(C3, C6), 120.98(C4,
C5), 149.24(C1, C2).
6
4
3
2608
J. Mater. Chem., 1998, 8, 2605–2610

Table 3 Elemental analysisa of metal complexes
mixture turned clear and slightly acidic (pH paper).
Ethylenediamine (0.15 g, 0.0025 mol) was added and the mix-
ture was gently refluxed for 24 h. The solution was concen-
trated to give the crude product as a brown solid. Yellow
needles were obtained after recrystallization from dichloro-
methane–methanol (253). Yield 78.0%, mp 98.0 °C. 1H NMR
(CDCl ): d 0.85(t, CH , 12H), 1.13–1.42(m, CH , 104H),
Complex
n
C (%)
H (%)
1
Cu
Ni
8
16
8
67.66 (67.74)
72.10 (72.39)
68.28 (68.26)
72.58 (72.80)
71.72 (71.57)
72.92 (72.98)
74.08 (74.13)
75.18 (75.09)
76.17 (75.90)
71.72 (71.91)
73.38 (73.29)
74.57 (74.42)
75.15 (75.36)
76.24 (76.16)
75.57 (75.42)
76.27 (76.36)
75.86 (75.65)
76.66 (76.57)
7.93 (7.89)
9.42 (9.58)
8.00 (7.76)
9.65 (9.63)
9.87 (9.81)
16
10
12
14
16
18
10
12
14
16
18
14
16
14
16
3
3
2
2
Cu
1.80(t, CH , 8H), 3.37(m, CNCH , 4H), 3.98(t, OCH , 4H),
2
2
2
9.93 (10.27)
10.76 (10.64)
10.92 (10.95)
11.24 (11.22)
9.87 (9.86)
10.17 (10.31)
10.78 (10.68)
10.96 (10.99)
11.30 (11.25)
11.54 (11.32)
11.58 (11.60)
11.69 (11.35)
11.69 (11.63)
4.00(t, OCH , 4H), 5.64(d, COCH, 2H), 6.75(m, CHN, 2H),
2
6.83(d, C H , 2H), 7.36(d, C H , 2H), 7.45(s, C H ,
6
3
6
3
6 3
2H), 10.19(m, CNH, 2H). 13C NMR (CDCl ): d 14.09, 22.67,
3
Ni
26.00, 29.14, 29.35, 29.69, 31.91, 50.21(NCH ), 69.03(OCH ),
2
2
69.16(OCH ),
90.84(CHL),
132.25(C1∞),
112.03(C5∞),
112.17(C2∞),
2
120.78(C6∞),
148.72(C3∞),
151.91(C4∞),
153.73(CLN), 189.63(CLO). IR (thin film): 1636, 1590, 1545,
1516, 1464, 1374, 1335, 1269, 1219 cm−1.
3
Cu
Ni
N,N∞-Bis[3-(4∞-hexadecanoxyphenyl)-3-oxopropenyl]ethyl-
enediamine. Light yellow solid, yield 84%, mp 172.0 °C. 1H
NMR (CDCl ): d 0.85(t, CH , 6H), 1.13–1.40(m, CH , 52H),
aCalculated values in parenthesis.
3
3
2
1.75(t, CH , 8H), 3.34(m, CNCH , 4H), 3.94(t, OCH , 4H),
2
2
2
5.61(d, COCH, 2H), 6.72(m, CHN, 2H), 6.83(d, C H , 4H),
7.77(d, C H , 4H), 10.23(m, CNH, 2H). 13C NMR (CDCl ):
d 14.05, 22.59, 25.94, 29.16, 29.27, 31.74, 50.12(NCH ),
68.03(OCH ),
131.89(C1∞), 153.76(C4∞), 161.63(CLN), 189.53(CLO).
6
4
3,4-Dihexadecyloxyacetophenone
6
4
3
2
White crystals, yield 85%. 1H NMR (CDCl ): d 0.83(t, CH ,
90.71(CHL),
113.89(C3∞),
129.00(C2∞),
3
3
2
6H), 1.24–1.84(m, CH , 56H), 2.52(s, CH , 3H), 3.99(t,
2
6
3
OCH , 4H), 6.82(d, C H , 1H), 7.68(d, C H , 1H), 7.54(s,
2
3
6 3
C H , 1H). 13C NMR (CDCl ): d 13.97, 22.56, 25.87, 26.07,
N,N∞-Bis[3-(3∞,4∞,5∞-trihexadecyloxyphenyl)-3-oxopropenyl]-
ethylenediamine. Light yellow solid, yield 80%, mp 49.0 °C. 1H
NMR (CDCl ): d 0.85(t, CH , 18H), 1.12–1.42(m, CH ,
6
3
3
29.00, 29.25, 29.45, 31.76, 68.10(OCH ), 111.49(C5),
2
112.32(C2), 123.14(C6), 130.40(C1), 148.78(C3), 153.48(C4),
197.73(CLO).
3
3
2
156H), 1.74(t, CH , 12H), 3.39(m, CNCH , 4H), 3.96(t,
2
2
OCH , 12H), 5.61(d, COCH, 2H), 6.77(m, CHN, 2H), 7.06(s,
C H , 4H), 10.25(m, CNH, 2H). 13C NMR (CDCl ): d 14.10,
22.68, 26.09, 29.37, 29.71, 30.32, 31.91, 50.18(NCH ),
2
Methyl 3,4,5-trihexadecyloxybenzoate ester
6
4
3
White solid, yield 92%. 1H NMR (CDCl ): d 0.84(t, CH ,
2
3
3
69.15(OCH ), 73.46(OCH ), 91.02(LCH), 105.80(C2∞, C6∞),
9H), 1.26–1.80(m, CH , 84H), 3.86(s, OCH , 3H), 3.97(t,
2
2
2
3
134.37(C1∞), 141.15(C4∞), 152.82(C3∞, C5∞), 154.04(CLN),
189.80(CLO).
OCH , 6H), 7.25(s, C H , 2H). 13C NMR (CDCl ): d 14.16,
2
6
2
3
22.77, 26.14, 29.35, 29.45, 29.62, 29.72, 29.75, 29.81, 30.41,
32.01, 52.11, 69.22(OCH ), 75.50(OCH ), 108.03(C2, C6),
124.68(C1), 142.43(C4), 152.80(C3, C5), 166.91(COO).
2
2
Copper complexes of N,N∞-bis[3-(3∞,4∞-dihexadecanoxyphenyl)-
3-oxopropenyl]ethylenediamine (general procedures for the
copper complexes)
3,4,5-Trihexadecyloxybenzoic acid
N,N∞-Bis[3-(3∞,4∞-dihexadecanoxyphenyl)-3-oxopropenyl]-
ethylenediamine (0.50 g, 0.40 mmol) dissolved in dichloro-
methane (5.0 ml) was added to a hot methanol solution of
copper() acetate monohydrate (0.038 g, 0.20 mmol). Upon
addition a light brown solid began to appear, and the solution
was gently refluxed for 6 h. The light brown solid was filtered
off, and recrystallized from dichloromethane–methanol to give
a grey–green solid. Yield 72%. IR (thin film):1621, 1599, 1578,
1495, 1466, 1437, 1401, 1383, 1327, 1271, 1231, 1202 cm−1.
Anal. Calc. for C H O N Cu: C, 75.09; H, 10.95. Found:
White solid, yield 83%. 1H NMR (CDCl ): d 0.83(t, CH ,
3
3
9H), 1.24–1.84(m, CH , 84H), 3.97(t, OCH , 6H), 7.29(s,
2
2
C H , 2H). 13C NMR (CDCl ): d 14.10, 22.69, 26.09, 29.38,
6
2
3
29.72, 30.34, 31.93, 69.17(OCH ), 73.54(OCH ), 108.54(C2,
C6), 123.66(C1), 143.08(C4), 152.83(C3,C5), 171.87(COO).
2
2
3,4,5-Trihexadecyloxyacetophenone
White solid, yield 82%. 1H NMR (CDCl ): d 0.82(t, CH ,
3
3
9H), 1.24–1.86(m, CH , 84H), 2.52(s, COCH , 3H), 3.96(t,
2
3
84 146 6
C, 75.18; H, 10.92%.
2
OCH , 6H), 7.15(t, C H , 2H). 13C NMR (CDCl ): d 14.05,
22.65, 26.1, 26.05, 26.30, 29.35, 29.69, 30.31, 31.68, 31.90,
2
6
2
3
69.29(OCH ), 73.47(OCH ), 107.11(C2, C6), 132.06(C1),
142.94(C4), 152.87(C3, C5), 196.92(CLO).
Nickel complexes of N,N∞-bis[3-(3∞,4∞-dihexadecanoxyphenyl)-
3-oxopropenyl]ethylenediamine (general procedures for the
nickel complexes)
2
2
General procedures for the synthesis of Schiff bases
N,N∞-Bis[3-(3∞,4∞-dihexadecanoxyphenyl)-3-oxopropenyl]-
ethylenediamine (0.50 g, 0.40 mmol) dissolved in dichloro-
methane (5.0 ml) was added to a hot methanol solution of
nickel() acetate tetrahydrate (0.049 g, 0.20 mmol), and the
solution gently refluxed for 4 h. The solution was concentrated
to dryness to give a brown solids. A yellow solid was obtained
after recrystallization from ethyl acetate. Yield 73%. 1H NMR
(CDCl ): d 0.88(t, CH , 12H), 1.27–1.49(m, CH , 104H),
N,N∞-Bis[3-(3∞,4∞-dihexadecanoxyphenyl)-3-oxopropenyl]-
ethylenediamine. A mixture of freshly cut sodium (0.34 g,
0.015 mol) suspended in dry diethyl ether (25.0 ml) and 3,4-
dihexadecyloxyacetophenone (3.0 g, 0.005 mol) was stirred for
0.5 h. Ethyl formate (1.85 g, 0.025 mol) was slowly added to
the solution at room temperature and the mixture allowed to
stir at room temperature under an N atmosphere for 18 h.
2
3
3
2
The pale orange cloudy solution was carefully quenched with
1.84(m, CH , 8H), 3.18(m, CNCH , 4H), 4.00(t, OCH ,
2
2
2
methanol to remove any excess sodium. The solution was
concentrated to give a yellow solid, which was redissolved in
dichloromethane (ca. 20.0 ml). Then acetic acid was added
slowly to neutralize the solution, and at this point the cloudy
4H), 5.63(d, COCH, 2H), 6.83(m, CHN, C H , 4H), 7.39(m,
6
3
C H , 4H). 13C NMR (CDCl ): d 14.07, 22.66, 26.03, 26.10,
29.25, 29.34, 29.35, 29.43, 29.51, 29.62, 29.65, 29.68, 29.71,
31.90, 57.92, 69.03, 69.31, 92.02, 112.48, 112.62, 119.88, 130.33,
6
3
3
J. Mater. Chem., 1998, 8, 2605–2610
2609

C. K. Lai and T. M. Swager, Chem. Mater., 1994, 6, 2252;
(e) C. K. Lai, C. H. Tsai and Y. S. Pang. J. Mater. Chem., 1998,
8, 1355.
(a) W. Pyzuk, E. Go´recka and A. Krwczynski, Liq. Cryst., 1992,
11, 797; (b) W. Pyzuk, E. Go´recka, A. Krwczynski and
J. Przedmojski, Liq. Cryst., 1993, 14, 773; (c) E. Go´recka,
W. Pyzuk, A. Krwczynski and J. Przedmojski, Liq. Cryst., 1993,
14, 1837.
148.42, 150.82, 156.14, 172.29. IR (thin film):1603, 1580, 1536,
1511, 1493, 1443, 1381, 1362, 1329, 1273, 1241, 1206, 1164,
1136 cm−1. Anal. Calc. for C H O N Ni: C, 75.36; H,
5
84 146 6
2
10.99. Found: C, 75.15; H, 10.96%.
Acknowledgements
6
7
W. Pyzuk, A. Krowczynski and E. Go´recka, Liq. Cryst., 1991,
10, 593.
(a) S. T. Trzaska and T. M. Swager, Chem. Mater., 1998, 10, 438;
(b) H. Zheng, C. K. Lai and T. M. Swager, Chem. Mater., 1994,
6, 101; (c) C. K. Lai, A. G. Serrette and T. M. Swager, J. Am.
Chem. Soc., 1992, 114, 7948.
We thank the National Science Council of Taiwan, ROC for
funding (NSC-87–2113-M008–007) in generous support of
this work.
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