Mixed f-d metallomesogens with an extended rigid core

Article abstract of DOI:10.1002/ejic.200400880

The liquid-crystalline behaviour of copper(II) and nickel(II) complexes of a mesogenic Schiff-base ligand derived from N,N′-disalicylidene-1,2- phenylenediamine (salophenH₂) and of the corresponding trinuclear mixed copper(II)/lanthanum(III) an

Full text of DOI:10.1002/ejic.200400880

FULL PAPER
Mixed f-d Metallomesogens with an Extended Rigid Core
Koen Binnemans,*[a] Katleen Lodewyckx,[a] Bertrand Donnio,[b] and Daniel Guillon[b]
Keywords: Copper / Lanthanides / Liquid crystals / Metallomesogens / Nickel
The liquid-crystalline behaviour of copper(II) and nickel(II
complexes of a mesogenic Schiff-base ligand derived from
N,NЈ-disalicylidene-1,2-phenylenediamine (salophenH2) and
)
tion with lanthanum(III) nitrate resulted in an increase of the
transition temperatures. The geometrical parameters (lattice
parameters and column cross-section) of all the metal com-
of the corresponding trinuclear mixed copper(II)/lantha- plexes are very similar, which indicates that the local organ-
num(III) and nickel(II)/lanthanum(III) complexes was investi-
gated. High-temperature X-ray diffraction studies revealed
that both the parent transition metal complexes and the
mixed f-d complexes exhibit a hexagonal columnar phase
isation in the mesophase is the same despite their structural
differences.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
(Colh) over an extended temperature range. Complex forma- Germany, 2005)
In this paper we have modified the salen-type ligand that
Introduction
has been used in earlier studies on f-d metallomesogens by
replacing 1,2-ethylenediamine as the linking group by 1,2-
diaminobenzene. The aim of the work was to investigate the
influence of the extension of the rigid part of the core of
the ligand on the thermal behaviour of the ligand and metal
complexes. Four mesogenic metal complexes were prepared,
namely two copper(ii) and nickel(ii) ones, and two binuclear
copper(ii)/lanthanum(iii) and nickel(ii)/lanthanum(iii) com-
plexes (Figure 3). Their liquid-crystalline properties were
investigated in detail by X-ray diffraction.
Liquid-crystalline metal complexes (metallomesogens)
combine the unique properties of both transition metals or
rare-earth metals and liquid crystals, and these compounds
form an intriguing class of new materials.[1] In this way, it
is, for instance, possible to obtain paramagnetic liquid crys-
tals,[2] or redox-active liquid crystals.[3] Nearly all metallic
elements of the periodic table have been used to create
metallomesogens, but examples of liquid crystals that con-
tain both an f-block metal ion (lanthanide or rare-earth
ion) and a d-block metal ion are rare. The first examples of
such mixed f-d metallomesogens have been reported re-
cently (Figure 1).[4] A copper(ii) complex of a mesogenic
2,2Ј-N,NЈ-bis(salicylidene)ethylenediamine (salen) deriva-
tive was used to form adducts with lanthanide(iii) nitrates. Results and Discussion
This work was extended further in the sense that the cop-
The synthesis of the N,NЈ-disalicylidene-1,2-phenylenedi-
per(ii) was replaced by nickel(ii) (Figure 2), and that the
influence of the chain length on the transition temperatures
was investigated.[5] In all cases, both the parent transition
metal complexes and the f-d complexes exhibit a hexagonal
columnar mesophase (Colh). It should be noticed that
salen-type ligands are of interest not only for preparing li-
quid-crystalline f-d complexes, but also for the design of
many types of liquid-crystalline transition metal com-
plexes.[6] The salen-type Schiff-base complexes are impor-
tant as catalysts.[7]
amine (salophenH2) Schiff-base ligand (H2L) and of the
metal complexes is outlined in Scheme 1. The first step is
the synthesis of 3,4,5-tris(tetradecyloxy)benzoic acid by al-
koxylation of 3,4,5-trihydroxybenzoic acid ethyl ester (Wil-
liamson ether synthesis), followed by formation of the free
acid by saponification of the ethyl ester and acidification of
the carboxylate salt. The second step is the coupling of
3,4,5-tris(tetradecyloxy)benzoic acid to the 4-position of
2,4-dihydroxybenzaldehyde by an ester bond (with DCC,
DMAP). The aldehyde was transformed into the Schiff-
base ligand by condensation with 1,2-diaminobenzene in
toluene. The water formed during the condensation reac-
tion was removed azeotropically in a Dean–Stark trap. The
copper(ii) complex CuL and the nickel(ii) complex NiL
were formed by reaction between the Schiff-base H2L and
copper(ii) acetate monohydrate and nickel(ii) acetate tetra-
hydrate, respectively, in a methanol/chloroform mixture.
[a] Katholieke Universiteit Leuven, Department of Chemistry,
Celestijnenlaan 200F, 3001 Leuven, Belgium
Fax: +32-16-327-992
E-mail: Koen.Binnemans@chem.kuleuven.ac.be
[b] Institut de Physique et Chimie des Matériaux de Strasbourg –
Groupe Matériaux Organiques, UMR 7504 CNRS-Université
Louis Pasteur,
B. P. 43, 23 rue du Loess, 67034 Strasbourg, Cedex 2, France
1506
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400880
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Mixed f-d Metallomesogens with an Extended Rigid Core
FULL PAPER
Figure 1. Structure of the first examples of mixed f-d metallomesogens, a trinuclear copper(ii)/lanthanum(iii) complex and a dinuclear
copper(ii)/gadolinium(iii) complex with a mesogenic 2,2Ј-N,NЈ-bis(salicylidene)ethylene diamine (salen) ligand, reported by Binnemans et
al.[4]
Figure 2. Structure of the copper(ii) complex CuL (M = Cu) and the nickel(ii) complex NiL (M = Ni) of the mesogenic N,NЈ-disalicylid-
ene-1,2-phenylenediamine (salophenH2) ligand.
Figure 3. Structure of the trinuclear copper(ii)/lanthanum(iii) complex CuLaL (M = Cu) and of the trinuclear nickel(ii)/lanthanum(iii)
complex NiLaL (M = Ni) of the mesogenic N,NЈ-disalicylidene-1,2-phenylenediamine (salophenH2) ligand H2L described in this study.
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K. Binnemans, K. Lodewyckx, B. Donnio, D. Guillon
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Scheme 1. Synthesis of the Schiff-base ligand H2L and of the metal complexes. Reagents and conditions: (a) RBr (3 equiv.), K2CO3
(6 equiv.), TBAB (phase-transfer catalyst), methyl isobutyl ketone, reflux overnight; (b) NaOH, ethanol, reflux for 4 h; acidification with
dilute HCl solution; (c) DCC, DMAP, dichloromethane, 24 h at room temp.; (d) 1,2-diaminobenzene (1/2 equiv.), glacial acetic acid
(catalyst), toluene, Dean–Stark trap, 3 h at reflux; (e) Cu(OOCCH3)2·H2O (M = Cu) or Ni(OOCCH3)2·4H2O (M = Ni) (1 equiv.),
methanol/chloroform, reflux overnight; (f) La(NO3)3·6H2O, acetone, room temp., 24 h.
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Mixed f-d Metallomesogens with an Extended Rigid Core
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The acetate ions act as the base to deprotonate the Schiff- Table 1. Transition temperatures and mesophase behaviour of the
Schiff-base complexes.
base ligand. The copper(ii)/lanthanum(iii) complex CuLaL
and the nickel(ii)/lanthanum(iii) complex NiLaL were pre-
pared by reaction between the copper(ii) complex CuL or
the nickel(ii) complex NiL and lanthanum(iii) nitrate hexa-
hydrate in acetone. The metal complexes were characterised CuLaL
by infrared spectroscopy and by elemental analysis. Both
Complex
Transition temperatures [°C][a]
CuL
NiL
Colho · 39 · Colh · 170 · I
Cr ·40 · CrЈ · 61 · Colh · 133 · I
Cr ·69 · Colh · 192 · dec.
Cr · 85 · Colh · 218 · I
NiLaL
the copper(ii)/lanthanum(iii) complex CuLaL and the nick-
el(ii)/lanthanum(iii) complex NiLaL were found to be trinu-
clear species consisting of two transition metal ions [either
copper(ii) or nickel(ii)] and one trivalent lanthanum(iii) ion
per molecule. The nitrogen content of the lanthanum(iii)
complexes, as determined by CHN microanalysis, is lower
than the calculated value. This discrepancy is due to a sys-
tematic error in the CHN microanalysis procedure, and can
be attributed to incomplete reduction of the nitrates to dini-
trogen gas or to the formation of lanthanum(iii) oxoni-
trides. Although we could not obtain single crystals of our
compounds for X-ray structure determination, we can nev-
ertheless deduce some data about the coordination sphere
of the lanthanum(iii) by referring to the crystal structures
published by Kahn et al. for f-d complexes of the salen li-
gand.[8] The three nitrate ions are coordinated to the lantha-
num(iii) ion in a bidentate fashion. The coordination
number of lanthanum(iii) is ten, with six oxygen atoms from
the three nitrate groups and four oxygen atoms of the two
copper(ii) salophen complexes [or nickel(ii) salophen com-
plexes]. The coordination polyhedron of lanthanum(iii) is
irregular and cannot be approximated by a highly symmet-
ric coordination polyhedron. Coordination number 10 is
rather unusual for lanthanide complexes, but can in this
case be achieved by the small bite angle of the nitrate
groups.
The Schiff-base ligand H2L is not mesomorphic, and it
melts directly to an isotropic liquid at 67 °C. All the metal
complexes are enantiotropic liquid crystals. The mesoph-
ases were studied by polarising optical microscopy (POM),
differential scanning calorimetry (DSC) and by high-tem-
perature X-ray diffraction. For the copper and nickel com-
plex, a typical texture of a hexagonal columnar mesophase
(Colh) could be seen by POM upon slow cooling from the
isotropic liquid. Only atypical textures were observed for
the trinuclear complex CuLaL and for the trinuclear com-
plex NiLaL, so that it was impossible to determine the me-
sophase unambiguously by POM. Observation of the tex-
ture of the copper/lanthanum complex CuLaL was also
hampered by the thermal decomposition of the complex in
the mesophase before the clearing point was reached. Just
above the melting point, the viscosity of the samples is quite
high, but the viscosity decreases with increasing tempera-
ture. Because no well-resolved DSC curves could be re-
corded (a problem also encountered in the past for similar
complexes),[4] no enthalpy data could be obtained. These
[a] Cr, CrЈ: crystalline phases; Colho: ordered hexagonal columnar
phase; Colh: hexagonal columnar phase; I: isotropic liquid; dec.:
decomposition.
Table 2. Characteristic X-ray data of the copper(ii) complex CuL.
Temperature
[°C]
dmeasd.
[Å]
[hk]
dcalcd.
[Å]
Mesophase and
parameters
30
37.3
21.4
18.7
10.3
4.5
[10]
[11]
[20]
h1
37.25
21.5
18.6
Colho
a = 43 Å
s = 1600 Å2
h2
4.1
s1
50
37.8
21.8
9.8
[10]
[11]
h1
37.8
21.8
Colh
a = 43.65 Å
s = 1650 Å2
4.5
h2
100
37.05
21.35
18.3
9.8
[10]
[11]
[20]
h1
36.9
21.3
18.45
Colh
a = 42.6 Å
s = 1570 Å2
4.5
h2
Table 3. Characteristic X-ray data of the nickel(ii) complex NiL at
100 °C.
dmeasd. [Å]
[hk]
dcalcd. [Å]
Mesophase and parameters
36.5
21.05
9.4
[10]
[11]
h1
36.5
21.1
Colh
a = 42.15 Å
s = 1540 Å2
4.5
h2
Table 4. Characteristic X-ray data of the copper(ii)/lanthanum(iii)
complex CuLaL.
Temperature
[°C]
dmeasd.
[Å]
[hk]
dcalcd.
[Å]
Mesophase and
parameters
100
36.7
[10]
[11]
[20]
h1
36.7
21.2
18.35
Colh
21.2
18.4
9.8
a = 42.4 Å
s = 1560 Å2
4.5
h2
150
35.7
20.5
17.8
13.5
9.9
[10]
[11]
[20]
[21]
h1
35.6
20.55
17.8
Colh
a = 41.1 Å
s = 1460 Å2
13.45
4.5
h2
The mesophase behaviour of the metal complexes was
problems could be due to the high viscosity of the com- studied in detail by temperature-dependent X-ray measure-
plexes, and to the low crystallinity of the complexes in the ments. The results of the X-ray measurements are summa-
solid phase. The transition temperatures of the complexes rised in Tables 2–5. X-ray patterns of the complexes are
were determined by optical microscopy, and the values are shown in Figures 4–8. X-ray diffractograms were recorded
given in Table 1.
at 30 °C (Figure 4) and at 50 °C and 100 °C (Figure 5) for
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K. Binnemans, K. Lodewyckx, B. Donnio, D. Guillon
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Table 5. Characteristic X-ray data of the nickel(ii)/lanthanum(iii)
complex NiLaL.
Temperature
[°C]
dmeasd.
[Å]
[hk]
dcalcd.
[Å]
Mesophase and
parameters
100
150
36.8
[10]
[11]
[20]
h1
h2
h3
[10]
[11]
[20]
h1
36.65
21.15
18.3
Colh
21.15
18.25
9.8
4.5
3.8
35.5
20.45
17.7
9.4
a = 42.3 Å
s = 1550 Å2
35.45
20.45
17.7
Colh
a = 40.9 Å
s = 1450 Å2
4.5
h2
Figure 6. X-ray diffractogram of the nickel(ii) complex NiL at
100 °C in the Colh phase.
Figure 4. X-ray diffractogram of the copper(ii) complex CuL at
30 °C in the Colho phase.
Figure 7. X-ray diffractogram of the copper(ii)/lanthanum(iii) com-
plex CuLaL at 150 °C in the Colh phase.
Figure 5. X-ray diffractogram of the copper(ii) complex CuL at
100 °C in the Colh phase.
Figure 8. X-ray diffractogram of the nickel(ii)/lanthanum(iii) com-
plex NiLaL at 150 °C in the Colh phase.
the mononuclear copper complex CuL (Table 2) and the
mononuclear nickel complex NiL (Table 3), and at 100 °C
(Figure 6) and 150 °C for the trinuclear copper/lanthanum
complex CuLaL (Figure 7, Table 4) and the nickel/lantha- of the aliphatic chains and rigid parts, at about 4.5 Å, a
num complex NiLaL (Figure 8, Table 5). All the samples distance corresponding to ϽhϾ in Figure 9 and Figure 10;
gave similar X-ray patterns when the experiments were per- (b) another, slightly less intense diffuse band (h1) seen at
formed in the mesomorphic temperature ranges. The X-ray about 9.4 Å, which could be an indication of a dimeric
patterns consist of: (a) a diffuse scattering halo (h2) in the structure; and (c) three or four sharp, intense reflections in
wide-angle region, corresponding to the liquid-like disorder the small-angle region, with the reciprocal spacings in the
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Mixed f-d Metallomesogens with an Extended Rigid Core
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is the same despite the structural differences. The hexagonal
symmetry of the columnar mesophase implies that the hard,
columnar core (i.e. the aromatic part) is cylindrical, and
that therefore the cross-section is circular. These hard col-
umns are separated from one another by the liquid paraf-
finic continuum formed by the molten alkyl chains. As far
as the copper(ii)/lanthanum(iii) complex and the nickel(ii)/
lanthanum(iii) complex are concerned, they both have a
square-like shape, and it is evident that upon their stacking
into an alternated orthogonal fashion (the halo h1 corre-
sponds to a dimerisation, as shown in Figure 10) and due
to the free rotation around the molecular axis, the apparent
cross-sections of the columns will appear circular, thus
satisfying the geometrical requirements for the formation
of the Colh phase. Moreover, and in agreement with this
proposal, we found that the molecular volume considering
a density of about 0.95 for each of these two trinuclear com-
pounds corresponds exactly to the volume of one single co-
lumnar stratum with a thickness of 4.5–4.6 Å (or to two
complexes per portion of column with a thickness of 9.2–
9.4 Å). Note also that the molecular dimensions of these
two mixed complexes are in good agreement with the lattice
parameters of the Colh phases, and thus they both lie al-
most flat in the 2D hexagonal lattice. However, due to the
lath-like shape of the mononuclear copper and nickel com-
plexes, it is probable that they initially associate into face-
to-face dimers (Figure 9) approximating the shape of a
large, flat square, which then self-organise into columns as
for the trinuclear complexes (Figure 9). Again, considering
a density close to unity for both the complexes, it was found
that the volume of a portion of column with a thickness of
about 4.5 Å can contain two mononuclear complexes, and
Figure 9. Molecular organisation of the copper(ii) complex CuL
and the nickel(ii) complex NiL within the hexagonal columnar me-
sophase. The columnar repeat unit is given by ϽpϾ, and ϽhϾ is
the average distance between adjacent molten chains.
Figure 10. Molecular organisation of the copper(ii)/lanthanum(iii)
complex CuLaL and the nickel(ii)/lanthanum(iii) complex NiLaL
within the columnar mesophase. The columnar repeat unit is given
by ϽpϾ, and ϽhϾ is the average distance between adjacent molten
chains.
ratio 1, √3, √4 and √7, corresponding to the indexation [hk] that the length of the complexes is of the order of the dia-
= [10], [11], [20] and [21], respectively. Such features are meter of the columns, a. As mentioned above, the presence
characteristic of a two-dimensional hexagonal packing of of the halo h1 at about 9.4 Å in the X-ray patterns of the
columns; that is, a hexagonal columnar mesophase (Colh). mesophases indicates that the repeating unit along the co-
The phase is disordered since there is no long-range corre- lumnar axis ϽpϾ is about twice the thickness of the com-
lation order within the columns, as evident from the ab- plexes. Thus, the repeating unit is formed by two molecules
sence of a sharp peak in the wide-angle region which would stacked on top of each other (dimeric structures). A similar
have corresponded to a more regular stacking along the co- behaviour was also observed for the copper complexes and
lumnar axis. However, for the copper complex CuL, an or- for the copper/lanthanide complexes we reported pre-
dered columnar mesophase with a hexagonal symmetry viously.[4] Structural models for the different metal com-
(Colho) was observed below 39 °C. A typical feature in the plexes are shown in Figures 9 and 10. Moreover, a change
X-ray diffractogram of this compound is the sharp diffrac- of the linking group formed by ethylenediamine to a linking
tion peak in the wide-angle region at about 4.1 Å (Fig- group formed by 1,2-diaminobenzene in the Schiff-base li-
ure 4). The corresponding nickel complex NiL is crystalline gand has a negligible effect on the column lattice parame-
at temperatures below 61 °C, and undergoes a crystal-to- ters. This is not unexpected due to the presence of the (dis-
crystal transition between 35 and 40 °C. The crystalline ordered) alkyl chains in the complexes in the mesophase.
character of this compound at ambient temperature is evi- For all the complexes, the lattice parameter a decreases with
dent from the large number of sharp diffraction peaks in increasing temperature.
the X-ray pattern. For the complexes in the mesophase, the
lattice parameter, a, and the column cross-section, s, were
determined from the positions of the small angle diffraction
Conclusions
peaks (10), (11), (20) and (21): a = 2/√3[1/4(d10 + √3d11
2d20 + √7d21)] and s = 2/√3[1/4(d10 + √3d11 + 2d20
+
+
We have studied the mesophase behaviour of new cop-
√7d21)].[2] The lattice parameters and thus the column cross- per(ii), nickel(ii), copper(ii)/lanthanum(iii) and nickel(ii)/
sections of all the complexes are very similar. This similarity lanthanum(iii) complexes of a mesogenic N,NЈ-disalicylid-
indicates that the local organisation within the mesophase ene-1,2-phenylenediamine (salophenH2) ligand. The cop-
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K. Binnemans, K. Lodewyckx, B. Donnio, D. Guillon
FULL PAPER
tetradecane (97.05 g, 0.35 mol), were added to a 1 L flask. Sub-
sequently, the reaction mixture was heated to reflux and stirred
overnight. The brown mixture was cooled below 100 °C, and water
(300 mL) was added. The aqueous layer was separated, and the
organic layer was washed with water (300 mL), dilute HCl solution
(300 mL, 1.0 m), and water (300 mL) again. The solvent was re-
moved on a rotary evaporator and the crude product was recrystal-
lised from acetone. This product was redissolved in an ethanol solu-
tion of NaOH (16 g, 0.4 mol) and refluxed for 4 h. After allowing
the solution to cool to room temperature, the reaction mixture was
per(ii)/lanthanum(iii) and the nickel(ii)/lanthanum(iii) com-
plexes are trinuclear. All the Schiff-base complexes exhib-
ited a hexagonal columnar mesophase (Colh). X-ray diffrac-
tion measurements on samples in the mesophase indicate
that the geometrical parameters (lattice parameter a and
column cross-section s) are largely independent of the type
of complex. This indicates that the structure of the meso-
phase is more or less identical for all the complexes. The
metal has an influence on the transition temperatures:
higher transition temperatures have been observed, and poured into cold water. The solution was acidified with dilute HCl.
The precipitate was filtered off, recrystallised from dichlorometh-
ane and washed with ethanol. Yield: 57% (42.67 g), m.p. 72 °C.
C49H90O5 (749.24): calcd. C 77.52, H 11.95; found C 77.56, H
thus a substantial enhancement of the mesophase stability
achieved, for the mixed f-d metallomesogens with respect
to the parent transition metal complexes. The replacement
of the ethylenediamine linking group present in the first
type of mixed f-d metallomesogens by a more rigid 1,2-
diaminobenzene linking group has a negligible influence on
the mesophase behaviour. This is probably due to the fact
that the linking group constitutes only a small part of the
total ligand. One could have expected that the enhanced
π-π stacking of the aromatic cores would result in higher
transition temperatures, but this is not the case. The differ-
ence between the copper(ii) or nickel(ii) ion as the d-block
metal is reflected in the thermal stability of the f-d com-
plexes, in the sense that the nickel(ii)/lanthanum(iii) com-
plex is thermally more stable than the corresponding cop-
1
11.98. H NMR (CDCl3, 300 MHz): δ = 0.89 (t, J = 6.3 Hz, 9 H,
CH3), 1.27 (m, 30 H, CH2), 1.49 (m, 6 H, CH2CH2CH2O), 1.81
(m, 6 H, CH2CH2O), 4.03 (t, J = 6.3 Hz, 6 H, CH2O), 7.33 (s, 2
H, H-aryl) ppm.
Synthesis of 3-Formyl-4-(hydroxyphenyl)-3,4,5-tris(tetradecyloxy)-
benzoate: 3,4,5-Tris(tetradecyloxy)benzoic acid (15.16 g, 0.02 mol)
and DMAP [4-(dimethylamino)pyridine; 0.24 g, 0.002 mol) were
added to a mixture of 2,5-dihydroxybenzaldehyde (2.76 g, 0.02 mol)
and N,NЈ-dicyclohexylcarbodiimide (DCC; 4.60 g, 0.022 mol) in
600 mL of dichloromethane. The solution was stirred at room tem-
perature for 24 h. The precipitated N,NЈ-dicyclohexylurea was fil-
tered off and washed with
a saturated NaHCO3 solution
(2×400 mL) and water (2×400 mL). The aqueous layers were
per(ii)/lanthanum(iii) complex. The presence of the rigid back-extracted with dichloromethane (200 mL). The combined or-
ganic layers were dried with MgSO4 and the solvent was removed
on a rotary evaporator. The crude compound was purified by col-
umn chromatography (silica, with dichloromethane as the eluent).
Yield: 49% (8.60 g), m.p. 70 °C. C56H94O7 (879.34): calcd. C 76.49,
H 10.77; found C 76.56, H 10.83. H NMR (CDCl3, 300 MHz): δ
= 0.89 (t, 9 H, CH3), 1.27 (m, 30 H, CH2), 1.50 (m, 6 H,
linking group is not a sufficient condition to induce a meso-
phase in the Schiff-base ligand.
1
Experimental Section
Equipment: The NMR spectra were recorded on a Bruker Avance
300 spectrometer (operating at 300 MHz) and Bruker AMX-400
(operating at 400 MHz), using CDCl3 as solvent and tetramethylsi-
lane (TMS) as internal standard. FTIR spectra were recorded on
a Bruker IFS-66 spectrometer, using the KBr pellet method. Ele-
mental analyses were obtained on a CE-Instrument EA-1110 ele-
mental analyzer. The optical textures of the mesophases were ob-
served with an Olympus BX60 polarizing microscope equipped
with a LINKAM THMS600 hot stage and a LINKAM TMS93
programmable temperature-controller. DSC traces were recorded
with a Mettler–Toledo DSC821e module. The XRD patterns were
obtained with two different experimental set-ups, and in all cases
the powdered sample was filled in Lindemann capillaries of 1 mm
CH2CH2CH2O), 1.81 (m, 6 H, CH2CH2O), 4.05 (t, 6 H, CH2O),
7.06 (d, Jo = 9.15 Hz, 1 H, H-aryl), 7.36 (dd, Jo = 8.91, Jm
=
2.84 Hz, 1 H, H-aryl), 7.40 (s, 2 H, H-aryl), 7.44 (d, Jm = 2.58 Hz,
1 H, H-aryl), 9.89 (s, 1 H, CHO), 10.96 (s, 1 H, OH) ppm.
Synthesis of the Schiff-Base Ligand H2L: 1,2-Diaminobenzene
(54 mg, 0.5 mmol) and five drops of glacial acetic acid (as the cata-
lyst) were added to a solution of 3-formyl-4-(hydroxyphenyl)-3,4,5-
tris(tetradecyloxy)benzoate (0.88 g, 0.001 mol) in 150 mL of tolu-
ene. The mixture was heated for 3 h at reflux, and the water formed
by the reaction was removed azeotropically (Dean–Stark trap). Af-
ter allowing the solution to cool to room temperature, the solvent
was removed under reduced pressure. The crude product was puri-
fied by recrystallisation from absolute ethanol. Yield: 92% (0.84 g),
m.p. 67 °C. C118H192N2O12 (1830.8): calcd. C 77.41, H 10.57, N
diameter. A linear monochromatic Cu-Kα beam (λ = 1.5405 Å)
1
obtained with a sealed-tube generator (900 W) and a bent quartz
monochromator were used (both generator and monochromator
were manufactured by Inel). One set of diffraction patterns was
registered with a curved counter Inel CPS 120, for which the sam-
ple temperature was controlled to within 0.05 °C; periodicities up
to 60 Å could be measured. The other set of diffraction patterns
was registered on an Image Plate detector. The cell parameters were
calculated from the position of the reflection at the smallest Bragg
angle, which is in all cases the most intense. Periodicities up to 90 Å
could be measured, and the sample temperature was controlled to
within 0.3 °C.
1.53; found C 76.94, H 10.57, N 1.54. IR (KBr): ν = 1626 cm–1
˜
1
(C=N), 1209 (C–O). H NMR (CDCl3, 300 MHz): δ = 0.88 (t, 18
H, CH3), 1.26 (m, 60 H, CH2), 1.49 (m, 12 H, CH2CH2CH2O),
1.83 (m, 12 H, CH2CH2O), 4.05 (m, 16 H, CH2O, CH2N), 6.80–
7.45 (m, 14 H, H-aryl), 8.59 (s, 2 H, CH=N), 13.01 (s, 2 H, OH)
ppm.
Synthesis of the Copper(II) Complex CuL: A hot solution of cop-
per(ii) acetate monohydrate, (30 mg, 0.15 mol) in methanol was
added dropwise to a hot solution of the Schiff-base ligand H2L
(0.24 g, 0.13 mmol) in chloroform. The reaction mixture was re-
Synthesis of 3,4,5-Tris(tetradecyloxy)benzoic Acid: Ethyl 3,4,5-tri- fluxed overnight. After allowing the solution to cool to room tem-
hydroxybenzoate (19.82 g, 0.1 mol), K2CO3 (55.28 g, 0.4 mol), tetra-
butylammonium bromide (TBAB, phase-transfer catalyst) (1.61 g,
5 mmol), methyl isobutyl ketone (MIBK; 300 mL) and 1-bromo-
perature, the solvent was removed under reduced pressure. The
crude product was crystallised from ethyl acetate, washed with
methanol and dried in vacuo. Yield: 92% (0.23 g). IR (KBr): ν =
˜
1512
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 1506–1513

Mixed f-d Metallomesogens with an Extended Rigid Core
FULL PAPER
1606 cm–1 (C=N), 1203 (C–O). C118H196CuN2O15 (1892.3): calcd.
C 72.82, H 10.15, N 1.44; found C 72.88, H 10.24, N 1.49.
Chem. Rev. 1993, 93, 861–885; c) Metallomesogens, Synthesis
Properties and Applications (Ed.: J. L. Serrano) Wiley-VCH,
Weinheim, 1996; d) D. W. Bruce, in Inorganic Materials (Eds.:
D. W. Bruce, D. O’Hare), 2nd edition, Wiley, Chichester, 1996;
chapter 8, p. 429; e) B. Donnio, D. W. Bruce, Struct. Bonding
(Berlin) 1999, 95, 193–247; f) K. Binnemans, C. Görller-Wal-
rand, Chem. Rev. 2002, 102, 2303–2345; g) B. Donnio, D. Guil-
lon, R. Deschenaux, D. W. Bruce, in Comprehensive Coordina-
tion Chemistry II (Eds.: J. A. McCleverty, T. J. Meyer), Elsevier,
Oxford, 2003, volume 7 (Eds.: M. Fujita, A. Powell, C. Creutz),
chapter 7.9, pp. 357–627.
a) Yu. Galyametdinov, M. A. Athanassopoulou, K. Griesar, O.
Kharitonova, E. A. Soto Bustamante, L. Tinchurina, I. Ovch-
innikov, I. W. Haase, Chem. Mater. 1996, 8, 922–926; b) K.
Binnemans, Yu. G. Galyametdinov, R. Van Deun, D. W. Bruce,
S. R. Collinson, A. P. Polishchuk, I. Bikchantaev, W. Haase,
A. V. Prosvirin, L. Tinchurina, I. Litvinov, A. Gubajdullin, A.
Rakhmatullin, K. Uytterhoeven, L. Van Meervelt, J. Am.
Chem. Soc. 2000, 122, 4335–4344; c) P. J. Alonso, J. I. Marti-
nez, L. Oriol, M. Pinol, J. L. Serrano, Adv. Mater. 1994, 6, 663–
667; d) J. Barbera, R. Gimenez, M. Marcos, J. L. Serrano, P. J.
Alonso, J. I. Martinez, Chem. Mater. 2003, 15, 958–964.
Synthesis of the Nickel(II) Complex NiL: A hot solution of nickel(ii)
acetate tetrahydrate (70 mg, 0.28 mol) in methanol was added drop-
wise to a hot solution of the Schiff-base ligand H2L (0.46 g,
0.25 mmol) in chloroform. The reaction mixture was heated at re-
flux temperature overnight. After allowing the solution to cool to
room temperature, the solvent was removed under reduced pres-
sure. The crude product was crystallised from ethyl acetate, washed
with methanol and dried in vacuo. Yield: 86% (0.41 g). IR (KBr):
[2]
ν = 1606 cm–1 (C=N), 1203 (C–O). C118H190N2NiO12 (1887.5):
˜
calcd. C 75.09, H 10.15, N 1.48; found C 74.68, H 10.28, N 1.50.
Synthesis of the Copper(II)/Lanthanum(III) Complex CuLaL: A
solution of lanthanum(iii) nitrate hexahydrate (0.048 g, 0.11 mmol)
in acetone was added to a solution of the copper complex CuL
(0.189 g, 0.1 mmol) in acetone. The reaction mixture was stirred at
room temperature for 24 h. The precipitate was filtered off, washed
with cold methanol and dried in vacuo. Yield: 40% (164 mg). IR
(KBr): ν = 1629 cm–1 (C=N), 1306 (C–O). C236H380Cu2LaN7O33
˜
(4105.59): calcd. C 68.98, H 9.33, N 2.39; found C 68.45, H 9.23,
N 1.97.
[3]
a) R. Deschenaux, M. Schweissguth, A. M. Levelut, Chem.
Commun. 1996, 1275–1276; b) G. H. Walf, R. Benda, F. J. Lit-
terst, U. Stebani, S. Schmidt, G. Lattermann, Chem. Eur. J.
1998, 4, 93–99; c) B. Donnio, J. M. Seddon, R. Deschenaux,
Organometallics 2000, 19, 3077–3081.
K. Binnemans, K. Lodewyckx, B. Donnio, D. Guillon, Chem.
Eur. J. 2002, 8, 1101–1105.
Synthesis of the Nickel(II)/Lanthanum(III) Complex NiLaL: A solu-
tion of lanthanum(iii) nitrate hexahydrate (0.048 g, 0.11 mmol) in
acetone was added to a solution of the nickel complex NiL
(0.189 g, 0.1 mmol) in acetone. The reaction mixture was stirred at
room temperature for a period of 24 h. The precipitate was filtered
off, washed with cold methanol and dried in vacuo. Yield: 46%
[4]
[5]
K. Binnemans, K. Lodewyckx, Supramol. Chem. 2003, 15, 485–
494.
(187 mg). IR (KBr):
ν =
˜
1627 cm–1 (C=N), 1205 (C–O).
[6] a) R. Paschke, D. Balkow, U. Baumeister, H. Hartung, J. R.
Chipperfield, A. B. Blake, P. G. Nelson, G. W. Grey, Mol.
Cryst. Liq. Cryst. 1990, 188, 105–118; b) K. Ohta, Y. Mori-
zumi, T. Fujimoto, I. Yamamoto, K. Miyamura, Y. Gohshi,
Mol. Cryst. Liq. Cryst. 1992, 214, 161–169; c) A. Serrette, P. J.
Carroll, T. M. Swager, J. Am. Chem. Soc. 1992, 114, 1887–1889
(Corrigendum: 1993, J. Am. Chem. Soc. 115, 11 656); d) R.
Paschke, D. Balkow, E. Sinn, Inorg. Chem. 2002, 41, 1949–
1953; e) I. Aiello, M. Ghedini, M. La Deda, D. Pucci, O. Fran-
cescangeli, Eur. J. Inorg. Chem. 1999, 1367–1372; f) N. Hosh-
ino, Coord. Chem. Rev. 1998, 174, 77–108.
C236H380LaN7Ni2O33 (4095.60): calcd. C 69.15, H 9.35, N 2.39;
found C 69.23, H 9.36, N 2.06.
Acknowledgments
K. B. thanks the F.W.O.-Flanders (Belgium) for a postdoctoral fel-
lowship. Financial support by the F.W.O.-Flanders (G.0117.03) and
by the K. U. Leuven (GOA, 03/03) is gratefully acknowledged.
Funding for travel was obtained from a Tournesol project (Project
T2004.10).
[7] P. G. Cozzi, Chem. Soc. Rev. 2004, 33, 410–421.
[8] M. L. Kahn, T. M. Rajendiran, Y. Jeannin, C. Mathonière, O.
Kahn, C. R. Acad. Sci. Ser. IIc 2000, 3, 131.
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Received: October 19, 2004
Eur. J. Inorg. Chem. 2005, 1506–1513
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