Palladium(II) metallomesogens of crown ether derivatized imines, and their sodium adducts

Article abstract of DOI:10.1016/j.jorganchem.2006.08.091

A series of imines HL_n (1) (n stands for the alkoxy chain length: 4, 6, 8, 10, and 12) has been synthesized by condensation of 4-aminobenzo-15-crown-5 and p-alkoxybenzaldehyde. Orthopalladation afforded the dinuclear derivatives [Pd(μ-OAc)L

Full text of DOI:10.1016/j.jorganchem.2006.08.091

Journal of Organometallic Chemistry 691 (2006) 4990–4999
www.elsevier.com/locate/jorganchem
Palladium(II) metallomesogens of crown ether derivatized imines,
and their sodium adducts
*
´
Javier Arias, Manuel Bardajı, Pablo Espinet
Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain
Received 2 May 2006; received in revised form 17 August 2006; accepted 17 August 2006
Available online 8 September 2006
Abstract
A series of imines HLn (1) (n stands for the alkoxy chain length: 4, 6, 8, 10, and 12) has been synthesized by condensation of 4-amin-
obenzo-15-crown-5 and p-alkoxybenzaldehyde. Orthopalladation afforded the dinuclear derivatives [Pd(l-OAc)Ln]2 (2) which, by sub-
stitution reactions, led to dinuclear and mononuclear derivatives [Pd(l-Cl)Ln]2 (3) and [Pd(b-diket)Ln] (4) (b-diket = H25C12OH4C6–
C(O)–CH–C(O)–C6H4OC12H25). The imine ligands and the acetato bridged complexes are non-mesogenic whilst the chloro-bridged
and the diketonato complexes are enantiotropic liquid crystals. They display smectic A mesophases. Complexation with sodium perchlo-
rate afforded the corresponding derivatives [(O2ClO2)NaCrown] (Crown = crown derivatives 1–4 for n = 4). None of the sodium adducts
is mesogenic. The acetato bridged complexes consist of a mixture of syn and anti isomers and a dramatic increase in the syn:anti ratio is
produced upon complexation of NaClO4 (syn:anti = 4:96 for complexes 2 versus 54:46 for the corresponding [(O2ClO2)NaCrown2]). The
crown ether derivatives extract sodium picrate from aqueous solutions and the presence of the palladium centers improves clearly the
extraction, [Pd(l-Cl)Ln]2 being the best and the fastest extractor. A model for the extraction and transport process in these complexes
is proposed.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Palladium; Crown ether; Imine; Sodium complexes; Liquid crystals; Ionic transport
1. Introduction
calamitic liquid crystals self-organize into columnar meso-
phases; (b) an increase [3j] or a decrease [3a,3b,3g,3h] of
mesophase stability, the latter leading in the extreme to dis-
appearance of the mesogenic behavior.
The ability of crown ethers to complex cations [1] has
been exploited to produce sensors of cations, to extract cat-
ions, for ionic transport in membranes, or to prepare sta-
tionary phases in chromatography [2].
The formation of mesogenic organic materials from
functionalized macrocyclic ligands is a subject of current
interest. Examples have been reported using crown ethers,
which afford, often by their symmetric functionalization
with promesogenic fragments, calamitic, columnar or
plasmidic mesophases [3]. Further complexation with alkali
salts produces a variety of results: (a) changes in the meso-
phase type [3b,3e,3f,3g,3h,3l], as in cases when typically
Very little work has been reported on the synthesis of
metallomesogens containing transition metals and crown
ethers. Often the crowns have some oxygen atoms substi-
tuted by better coordinating nitrogen or sulfur atoms [4].
The central crown cavity is occupied by the metal, which
sometimes induces the mesogenic behavior as found in pol-
iazacrown cobalt [4a], diazapolyether crown copper [4c],
luminescent diazacrown lanthanide [4g], or in polythioe-
ther crown palladium derivatives [4e,4f]. Therefore, the
crown is already blocked and it is not possible to further
complex an alkali salt. However, in related phthalocyanine
metallomesogens containing uncomplexed crown ethers,
the addition of alkali cations induces changes in the struc-
ture and the transport properties [3d,5].
*
Corresponding author.
E-mail address: espinet@qi.uva.es (P. Espinet).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.091

J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4991
2. Results and discussion
O
O
H
O
O
O
C
OCnH2n+1
2.1. Syntheses and structural characterization
N
The imines 1 were readily prepared by condensation of
the corresponding p-alkoxybenzaldehydes (n = 4, 6, 8, 10,
and 12) and amino crown derivatives. Treatment of the
imines with the stoichiometric amount of palladium acetate
afforded the dinuclear cyclopalladated derivatives 2. The
reaction of 2 with HCl in diethyl ether, or with a b-diketone
in the presence of triethylamine, lead to dinuclear chloro-
bridged derivatives 3 or mononuclear diketonato deriva-
tives 4, respectively (Scheme 1).
n = 4, 6, 8, 10, 12
Fig. 1. Imines used in this work.
Dinuclear and mononuclear orthopalladated com-
pounds are one of the most widely studied class of metall-
omesogens because of their stability and the structural
versatility of the system [6]. Our group has reported a vari-
ety of cyclopalladated complexes and studied the structure-
mesogenic activity relationship, including the first chole-
steric metallomesogens [7], as well as complexes displaying
ferroelectricity [8], non-linear optics [9] or lyotropism [10].
The combination of different coordinating entities, such
as a crown ether, an imine and an alkoxy chain, into an
unique ligand could give rise to interesting systems capable
of selective recognition processes and additional properties.
In this paper, we report the synthesis and characterization
of Schiff bases functionalized with alkoxy chains of differ-
ent length and with crown ethers (Fig. 1), and their ortho-
palladated complexes. Some of these compounds behave as
thermotropic liquid crystals. Adducts of these compounds
with sodium perchlorate were prepared, which showed no
mesogenic behavior. The extraction properties of sodium
of these compounds are also reported.
These compounds are white 1, orange 2, or yellow 3–4
solids at room temperature. They were characterized by
IR and NMR spectroscopy, as well as by elemental analy-
sis. The IR spectra of the free imines show a stretching
band at 1607 cmꢀ1, assigned to m(C@N), which is shifted
to lower wavenumbers, compared to the free imines, by
ca. 20 cmꢀ1 for derivatives 2, ca. 30 cmꢀ1 for 3, and ca.
5 cmꢀ1 for 4 [11]. The IR spectra of compounds 3 show
the presence of m(Pd–Cl) bands (247 cmꢀ1) [12]. The ace-
tato-bridged complexes 2 are a mixture of syn and anti iso-
mers relative to the imine arrangement in each half of the
1
molecule [7,13], in a 4:96 ratio as shown by H NMR,
whilst chloro-bridged derivatives 3 are the pure anti isomer.
The largest difference in chemical shift, compared to the
free imines, is observed for the iminic proton (8.39 for 1,
7.45 for 2, 7.81 for 3, and 8.04 ppm for 4) and then for
O
O
H
O
C
OC H
n 2n+1
O
O
1a-1e
n = 4, 6, 8, 10, 12
N
[Pd (OAc) ]
3
6
O
O
H
O
O
C
OC H
n 2n+1
O
N
Pd
2a-2e
NEt , β-diketone
2
AcO
3
HCl/Et O
2
O
H
O
O
H
O
O
O
O
O
O
C
OC H
C
OC H
n
2n+1
n
2n+1
O
N
N
Pd
Pd
O
O
Cl
2
3a-3e
O
O
C
H
12 25
H
C
25 12
4a-4e
Scheme 1.

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J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
the aromatic protons, whilst the crown ether methylene
hydrogen atoms and the alkyl chains are only very slightly
shifted. The assignments given in Section 4 were assessed
by COSY and NOESY experiments.
because it has the best radius to fit the 15-crown ether moi-
ety [14]. The evidences supporting the formulation of the
complexes as containing perchlorate covalently bonded to
sodium are discussed later.
Complexation of compounds 1a–4a (for chain length
n = 4) with NaClO4 was achieved by addition of sodium
These sodium-containing complexes are pale yellow (for
1a) or yellow solids at room temperature. They were char-
acterized by IR and NMR spectroscopy, as well as elemen-
tal analysis. The elemental analyses were consistent with
the a Pd:Na = 1:1 ratio, but this is not very significant as
the method of preparation (evaporation to dryness) should
produce this result also for a 1:1 mixture. More significant,
the complexes are soluble in CDCl3, where NaClO4 is
insoluble, and a main change in the NMR spectra is
observed (Fig. 2): the methylene crown ether resonances
split due to the loss of symmetry upon sodium coordina-
tion (compare the signals in the range 3.0–4.5 ppm for
the pairs a/b and c/d in Fig. 2). Some small shifts of the
aromatic protons are also observed.
perchlorate in
a ratio 15-crown ether:sodium = 1:1
(Scheme 2). Sodium was chosen as the alkaline cation
O
O
H
O
O
O
C
OC H
n
2n+1
N
Pd
1a–4a, n = 4
NaClO
4
1
Additional major changes are observed in the H NMR
spectrum of derivative [(O2ClO2)NaCrown2a] (spectrum d)
compared to 2a (spectrum c): two different sets of reso-
nances, in molar ratio close to 1:1, are seen. The signals
for the methyl groups of the acetato bridges and those of
the imine resonances reveal that this apparent splitting cor-
responds in fact to a dramatic increase of the syn:anti ratio
in the complexes [(O2ClO2)NaCrown2a] (syn:anti = 54:46)
as compared to their orthopalladated precursors 2a
(syn:anti = 4:96). When the solid [(O2ClO2)NaCrown2a] is
H
O
O
O
O
O
O
C
OC H
n
2n+1
Na
O
N
Cl
O
Pd
O
[(O ClO )NaCrown1a] – [(O ClO )NaCrown4a]
2
2
2
2
Scheme 2.
Fig. 2. 1H NMR spectra in CDCl3 of the following derivatives: (a) 1a, (b) [(O2ClO2)NaCrown1a], (c) 2a, and (d) [(O2ClO2)NaCrown2a]. The presence of
signals of the syn ( ) and anti (¤) isomers is highlighted for their corresponding imine and acetate hydrogen atoms (note that in the syn isomer the two
*
acetato groups are non-equivalent by symmetry).

J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4993
washed with water, NaClO4 is extracted and the starting
material is recovered, as observed by the H NMR spec-
and the complexes are better represented as [(O2ClO2)Na-
Crown2a]. The same applies to the rest of [(O2ClO2)Na-
Crown] compounds.
1
trum of the solid residue (syn and anti isomers again show
a 4:96 molar ratio). Similarly, when a CDCl3 solution of
[(O2ClO2)NaCrown2a] is shaked with water, NaClO4 is
extracted into the water layer and the CDCl3 solution
reverts to 2a in syn:anti ratio = 4:96. The existence of a
syn/anti exchange (slow for the monodimensional experi-
ment, hence the separated observation of the two isomers)
was verified for [(O2ClO2)NaCrown2a] by an EXSY NMR
experiment which confirmed that the eight resonances
(imine and acetate) of the anti isomers exchange with the
corresponding nine resonances of the syn isomer. The very
different syn:anti ratio observed for the complexes with and
without sodium perchlorate must be due to marked
changes in polarity of the two isomers upon sodium com-
plexation, these leading to a relative increase of stability
of the syn complex.
The IR spectrum of [(O2ClO2)NaCrown2a] shows sev-
eral absorptions in the vicinity of 1100 cmꢀ1, correspond-
ing to the perchlorate group anion with the typical
splitting associated to covalently bonded perchlorate (C2v
symmetry), both in the solid state and in chloroform solu-
tion (Fig. 3; the spectrum of a gold complex containing
ionic perchlorate is given for comparison). The same is
observed for the rest of the complexes containing sodium
perchlorate. This, along with the solubility of the com-
plexes in CDCl3 (NaClO4 is insoluble in this solvent) sug-
gests a tight association of the perchlorate anions to the
cationic complex, including covalent interactions of the
oxygen atoms of the perchlorate to the sodium cation.
Coordination of the sodium atom by perchlorate finds sup-
port in some X-ray structures reported in the literature [15],
where two oxygen atoms of the perchlorate are involved in
covalent bonding to sodium. Thus two oxygen atoms of the
perchlorate group together with the oxygen atoms of the
crown ether would complete the coordination of sodium,
2.2. Mesogenic behavior
Optical, thermal and thermodynamic data of derivatives
prepared, studied using polarized light optical microscopy
and differential scanning calorimetry, are collected in
Tables 1–4 and compared in Fig. 4. The SmA mesophases
were identified in optical microscopy by their typical oily
streaks and homeotropic textures or by their fan-shaped
textures (Fig. 5).
All the imine ligands are non-mesogenic (Table 1),
although the related imines containing an alkoxy chain in
para position instead of the crown ether moiety are meso-
genic [16]. The change in alkoxy chain length modifies
the melting points only up to 18 ꢁC. Thus, the crown ether
turns out to be the dominant structural motif influencing
the thermal behavior of the imine, leading to an unfavor-
able length to width aspect ratio, while the alkoxy chain
produces only a small influence. Orthometallation to give
dinuclear complexes 2 causes an increase of the melting
points, and non-mesogenic behavior (Table 2). This is typ-
ically observed for many acetate bridged palladium deriva-
tives due to their open book (or roof) geometry, which is
unfavorable towards mesogenic behavior.
The chloro bridged dinuclear complexes, having a favor-
able planar structure and stronger intermolecular interac-
tions [6], are enantiotropic liquid crystals (Table 3).
Table 1
Optical, thermal and thermodynamic data for the imine ligands 1a–1e HLn
Derivative
n
Transitiona
T/ꢁCb
DH/kJ molꢀ1
c
1a
4
C–C0
81.2
109.6
98.5
60.2
91.6
105.0
45.3
101.0
15.17
31.23
31.29
11.18
26.85
30.15
8.29
C0–I
C–I
1b
1c
6
8
c
C–C0
C0–I
C–I
1d
1e
10
12
c
C–C0
C0–I
38.52
a
C, C0 = crystal, I = isotropic liquid.
Data for the first heating scan.
Only observed by DSC.
b
c
Table 2
Optical, thermal and thermodynamic data for the complexes 2a–2e [Pd(l-
OAc)Ln]2
Derivative
n
Transitiona
T/ꢁCb
DH/kJ molꢀ1
2a
2b
2c
2d
2e
a
4
6
8
10
12
C–I
C–I
C–I
C–I
C–I
211.3
177.16
118.5c
133.6c
180c
66.54
49.46
–
–
–
C, C0 = crystal, I = isotropic liquid.
Data for the first heating scan.
Transition with decomposition.
b
c
Fig. 3. (a) [NaCrown2a]ClO4 in Nujol mull; (b) [NaCrown2a]ClO4 in
CHCl3 solution; (c) [Au(l-iPr2PCH2PPh2)2](ClO4)2 in Nujol mull.

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J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
Table 3
same SmA mesophases are found. However, the crown
ether derivatives show higher melting points and shorter
liquid crystal ranges, as is to be expected from decreasing
the alkoxy chain/palladium ratio from 2 to 1 and adding
the flexible crown ether moiety [16].The thermal stability
of the mesophase of complexes 3a–3 e is low, probably
due to the high clearing point temperature. Moreover,
decomposition is important after three heating-cooling
cycles.
Optical, thermal and thermodynamic data for the complexes 3a–3e [Pd(l-
Cl)Ln]2
Derivative
n
Transitiona
T/ꢁCb
DH/kJ molꢀ1
c
3a
4
6
8
C–SA
220
223.2
115.2
–
SA–I
I–SA
53.26d
ꢀ5.4
3b
3c
3d
C–SA
SA–I
I–SA
206.45
214.79
174.24
44.06
6.07
ꢀ1.33
45.37
6.31
–
Typical strategies to improve the mesogenic properties
are to reduce the molecular symmetry and to increase the
number of chains. Both are expected to reduce the melting
points. In effect, the mononuclear b-diketonato complexes
4, with a planar geometry and three alkoxy chains, show a
dramatic decrease of the melting points. Their melting
points are in the short range 60–86 ꢁC (about 100–134 ꢁC
lower than the corresponding complexes 3) and their clear-
ing points in the short range 114–135 ꢁC (about 90–108 ꢁC
lower than the corresponding complexes 3). This means a
considerable broadening in mesophase range (from 37 ꢁC
for n = 4 to 67 ꢁC for n = 10), more marked for short alk-
oxy chains (Table 4). The mesophase is very viscous and
again supercooling of the SmA phase rather than crystalli-
zation was observed (even down at ꢀ30 ꢁC; no Tg was
observed). The lowering in transition temperatures has a
positive effect on the thermal stability of the compounds
in their SmA phase, and after 10 cycles there was no notice-
able decomposition. The corresponding derivatives con-
taining imines with an alkoxy chain instead of the crown
ether fragment (typical K-shaped palladium complexes)
also display SmA phases but additionally show SmC and
N phases [10].
We have also studied the mesogenic behavior of the
adducts [(O2ClO2)NaCrown] (Crown = crown derivatives
1a–4a). The thermal data are collected in Table 5. As
expected, complexation of the crown ether moiety with
sodium ion changed the thermal behavior. As stated in
the introduction complexation of alkaline cations with
organic liquid crystals usually leads to more complicated
mesophases depending on the cation and the counter ion,
although a decrease of the mesophase stability or loss of
the mesophase has also been reported. In our case, how-
ever, none of the complexes is mesogenic, and they melt
with decomposition. The imine adduct [(O2ClO2)Na-
Crown1a] shows a higher melting point than 1a, while the
rest of [(O2ClO2)NaCrown] complexes, derived from 2a–
4a, display lower melting temperatures (with decomposi-
tion) than their precursor complexes. We also studied more
in more detail the variation of the mesogenic properties of
[Pd(l-Cl)L12]2 and [Pd(b-diket)L12] (with the longest chain,
lower melting points and larger SmA ranges than for n = 4)
with other sodium salts with different anions (see Sections 4
and 4.3). Melting points (always with decomposition) were
higher than for the precursors, as found for other crown
ether based mesogens [3f,3j,3l] and the liquid crystal prop-
erties were lost. In no case we found mesogenic behavior.
The unfavorable aspect ratio of the structures of the Na-
C–SA
SA–I
205.1
222.4
190
c
I–SA
10
12
C–SA
SA–I
I–SA
177.3
234.8
228.5
35.87
8.44
ꢀ0.71
34.19
10.36
ꢀ1.69
3e
C–SA
SA–I
I–SA
169.9
231.6
220.5
a
C, C0 = crystal, SA = smectic A, I = isotropic liquid.
Data for the first heating and cooling scans.
Only observed by polarized optical microscopy.
Combined enthalpies.
b
c
d
Table 4
Optical, thermal and thermodynamic data for the complexes 4a–4e [Pd(b-
diket)Ln]
Derivative
n
Transitiona
T/ꢁCb
DH/kJ molꢀ1
c
4a
4
C–C0
66.2
86
122.6
121.2
2.57
55.42
5.56
C–SA
SA–I
I–SA
ꢀ5.6
4b
4c
4d
6
8
C–SA
SA–I
I–SA
75.8
113.5
111.4
41.8d
3.15
ꢀ4.42
64.01
5.84
ꢀ6.24
38.38
5.38
ꢀ4.97
75.19
6.06
ꢀ5.99
C–SA
SA–I
I–SA
85.6
132.8
131.3
10
12
C–SA
SA–I
I–SA
59.8
126.9
124.3
4e
C–SA
SA–I
I–SA
70
135
133.3
a
C, C0 = crystal, SA = smectic A, I = isotropic liquid.
Data for the first heating and cooling scans.
Only observed by DSC.
b
c
d
Combined enthalpies.
Clearing points are in the short range 210–235 ꢁC. As the
mesophase is cooled down, the material became very vis-
cous, and crystallization is not observed because of super-
cooling of the SmA phase (no Tg was observed). The ranges
of mesophase broaden with alkoxy chain length from 3 ꢁC
(n = 4) to 62 ꢁC (n = 12). When this behavior is compared
to the reported for the related complexes containing imines
with an alkoxy chain instead of the crown ether fragment
(therefore typical H-shaped palladium derivatives), the

J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4995
275
225
175
125
75
1
2
3
4
SA
C’
C
25
4
6
8
10 12
4
6
8
10 12
4
6
8
10 12
4
6
8 10 12
Fig. 4. Thermal behavior of compounds 1 HLn, 2 [Pd(l-OAc)Ln]2, 3 [Pd(l-Cl)Ln]2, and 4 [Pd(b-diket)Ln] (on heating; n = 4, 6, 8, 10, and 12).
Fig. 5. Typical polarized optical microscopic textures (100·). Left: 3d, obtained on heating from the solid at 200 ꢁC. The picture shows oily streaks and
homeotropic zones. Right: 4e, obtained on cooling from isotropic liquid at 131 ꢁC.
the free ligand, all with the same alkoxy chain n = 12
(Table 6; see also Section 4). Sodium picrate was used in
order to have colored solutions in water, so that the salt
concentration can be easily estimated using visible spec-
troscopy. For all the cases, the presence of palladium
improved dramatically the extraction efficiency, especially
for the chloro-bridged derivative which is the best and
the fastest extractor. The results in terms of extraction effi-
ciency are as follows: [Pd(l-Cl)L12]2 > [Pd(l-OAc)L12]2 >
[Pd(b-diket)L12] ꢁ HL12. The time to reach the extraction
maxima follows the sequence: [Pd(l-OAc)L12]2 > HL12
= [Pd(b-diket)L12] ꢁ [Pd(l-Cl)L12]2.
Table 5
Optical and thermal data for the derivatives [(O2ClO2)NaCrown]
(Crown = Crown1a–Crown4a)
Derivative
Transitiona
T/ꢁC
[(O2ClO2)NaCrown1a]
[(O2ClO2)NaCrown2a]
[(O2ClO2)NaCrown3a]
[(O2ClO2)NaCrown4a]
C-I
C–I
C–I
C–I
130b,c
170b
198b
80b,c
a
C = crystal, I = isotropic liquid.
Transition with decomposition. Only observed by polarized optical
b
microscopy.
c
Mixture of isotropic liquid and solid.
complexed molecules, discussed above, accounts for the
loss of liquid crystal behavior upon sodium complexation.
Table 6
Efficiency as extractor of derivatives 1e–4e (n = 12)
2.3. Experiments of cation extraction
Extractor
% Extracteda
t/minb
HL12
[Pd(l-OAc)L12 2
[Pd(l-Cl)L12 2
[Pd(b-diket)L12
7
76
86
33
40
73
12
40
It is known that crown-ether compounds can extract
alkaline salts into organic solvents and transport them
through ‘‘membranes’’ built with organic solvent separa-
tors. The complexes reported here also show these proper-
ties. Quantitative measurements were carried out only on
their extraction efficiency, comparing the complexes with
]
]
]
a
Calculated as follows: (A0 ꢀ A)/A0 · 100; A0 = starting absorbance;
A = final absorbance.
b
Time to reach the equilibrium (no more sodium is extracted).

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J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4. Experimental
H2O
+
CHCl3
+
H2O
+
4.1. General procedures
(Na+ )aq.
+
(anion-)aq.
(Na+ )aq.
+
[(anion)NaCrown]
IR spectra were recorded on a FT 1720X Perkin–Elmer
spectrophotometer (4000–400 cmꢀ1) using KBr pellets, or a
+
(anion-)aq.
Crown
Perkin–Elmer 883 spectrophotometer (4000–200 cmꢀ1
)
1
using Nujol mulls between polyethylene sheets. H NMR
spectra were recorded on Bruker AC-300 or ARX-300
instruments in CDCl3 solutions (if no other solvent is sta-
ted); chemical shifts are quoted relative to SiMe4 (external,
1H). The EXSY experiment was carried out with a stan-
dard phase sensitive NOESY pulse sequence. Elemental
analyses were performed with a Perkin–Elmer 2400 micro-
analyzer. The textures of the mesophases were studied with
a Leica DMRB microscope, equipped with a Mettler FP-
82HT hot stage (heating rate of 10 K minꢀ1) and a temper-
ature controller Mettler FP-90. Transition temperatures
and enthalpies were measured by differential scanning cal-
orimetry, with a Perkin–Elmer DSC-7, using aluminium
crucibles. The apparatus was calibrated with indium
(156.6 ꢁC, 28.45 J gꢀ1) as standard. UV–Vis absorption
spectra were recorded at 298 K on a Shimadzu UV-1603.
net flux
Higher
Lower
concentration
concentration
Fig. 6. Transport induced by complexation of sodium perchlorate or
picrate with crown-ether compounds.
Picrate is known to behave structurally, in crown ether
complexes, in a way quite similar to perchlorate. In effect
[(picrate)NaCrown] complexes show in the solid state, the
sodium atom coordinated with the crown ether, the alkoxy
oxygen of picrate and one oxygen of one ortho-NO2 group.
It is obvious then that the extraction behavior of Na(picrate)
and NaClO4 must be the same: Both salts are incorporated to
CHCl3 solutions of the crown-containing compounds
(whether organic or orthopalladated) in the form of the
covalent species [(anion)NaCrown] (anion = picrate, ClO4).
As we have discussed before for the compounds with
NaClO4, washing with water removes the sodium salt from
the corresponding crown ether complex. Hence the trans-
port phenomenon can be easily understood as consisting
in the extraction of the sodium salt from a more concen-
trated water solution, in the form of the corresponding
covalent complex, and its liberation to the less concentrated
water solution (Fig. 6). The observation of covalently
bonded perchlorate in the solutions in chloroform of the
complexes reported here strongly supports this model.
4.2. Syntheses
The reactions were carried out in the air atmosphere
unless otherwise stated. 4-aminobenzo-15-crown-5
(Aldrich) was used as received and literature methods were
used to prepare p-alkyloxybenzaldehyde [17], [Pd3(OAc)6]
[18], b-diketone [19]. Only example procedures and IR
and NMR data for n = 8 are described here, as the synthe-
ses and the IR and NMR data were similar for the rest of
the compounds. Yields and analytical data are given for all
the compounds.
3. Conclusions
Imines derived from 4-aminobenzo-15-crown-5 do not
behave as liquid crystals, but their orthopalladated com-
plexes induce mesogenic properties for compounds with
planar geometry. Therefore, the substitution of alkoxy
chains by a crown ether moiety in the aniline ring of the
imine ligand does not preclude the formation of SmA mes-
ophases, although in a more limited temperatures range.
The addition of sodium perchlorate gives the correspond-
ing adducts, none of which behaves as liquid crystal. In fact
the addition of a sodium salt to a solid mesogen precludes
the appearance of the mesophase upon melting. The major
spectroscopic changes observed in the adducts is the
increase of the syn isomer for the acetato bridged adduct,
and the observation of covalently bonded perchlorate in
the compounds. This observation supports that covalent
structures are formed in solution which are responsible
for the solubilization of sodium salts in chloroform in the
form [(anion)NaCrown]. The extraction properties of the
crown ether compound are not only maintained but
improved by orthopalladation of the crown-functionalized
imine.
4.2.1. Preparation of the imine HLn 1
To an ethanol solution (50 mL) of 4-aminobenzo-15-
crown-5 (0.4991 g; 1,71 mmol) were added p-octyloxybenz-
aldehyde (404 ll; 1.71 mmol) and five drops of acetic acid
as catalyst. The mixture was refluxed for 4 h, then anhy-
drous MgSO4 was added and filtered. The filtrate was evap-
orated to dryness and the residue was washed with
methanol to afford the imine as a white solid. Yield of
1a: 68%. Anal. Calc. (%): C, 67.70; H, 7.50; N, 3.16.
Found: C, 67.53; H, 7.45; N, 3.20%. Yield of 1b: 85%.
Anal. Calc. (%): C, 68.77; H, 7.91; N, 2.97. Found: C,
69.22; H, 7.88; N, 2.97%. Yield of 1c: 94%. Anal. Calc.
(%): C, 69.71; H, 8.27; N, 2.80. Found: C, 69.42; H, 8.02;
N, 2.74%. Yield of 1d: 79%. Anal. Calc. (%): C, 70.55; H,
8.59; N, 2.65. Found: C, 70.35; H, 8.26; N, 2.60%. Yield
of 1e: 88%. Anal. Calc. (%): C, 71.32; H, 8.89; N, 2.52.
Found: C, 70.93; H, 8.49; N, 2.60%. 1H RMN of 1c
HL8: 0.89 (t, J(HH) = 7.0 Hz, 3H, CH3), 1.29–1.81 (m,
12H, CH3–(CH2)6–), 3.77 (m, 8H, O–CH2–CH2–O), 3.92
(m, 4H, Ph–O–CH2–CH2–O), 4.01 (t, J(HH) = 6.3 Hz,
2H, O–CH2–(CH2)n), 4.17 (m, 4H, Ph–O–CH2–CH2–O),

J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4997
6.77 (dd, J(HH) = 8.3 and 2.2 Hz, 1H, CHar–N@C), 6.83
(d, J(HH) = 2.2 Hz, 1H, CHar–N@C), 6.88 (d, J(HH) =
8.3 Hz, 1H, CHar–N@C), 6.96 (d, J(HH) = 8.7 Hz, 2H,
CHar–C@N), 7.81 (d, J(HH) = 8.7 Hz, 2H, CHar–C@N),
8.39 (s, 1H, CH@N); IR (KBr): 1607 (m(C@N)), 1245,
1128, 1060 cmꢀ1 (m(C–O–C)).
7.82 (s, 1H, CH@N), IR (KBr): 1578 (m(C@N)), 1270,
1228, 1138, 1055 (m(C–O–C)), 247 cmꢀ1 (m(PdCl)).
4.2.4. Preparation of [Pd(b-diket)Ln] 4
To a dichloromethane solution (10 mL, freshly distilled
to remove any traces of HCl) of b-diketone (0.0457 g;
7.709 mmol) under a N2 atmosphere, was added the stoi-
chiometric amount of NEt3 (7.709 mmol) and stirred for
4.2.2. Preparation of [Pd l-OAc)Ln]2 2
To a suspension of [Pd3(OAc)6] (0.0934 g; 0.139 mmol)
in acetic acid (15 mL), was added the stoichiometric
amount of imine HL8 (0.2078 g; 0.416 mmol) and the mix-
ture was stirred at 50 ꢁC for 15 h. After that, the suspension
was evaporated to dryness, dichloromethane was added
and then filtered through a pad of Kiesselgur. Partial evap-
oration and addition of hexane afforded the compound as
an orange solid. Yield of 2a: 75%. Anal. Calc. (%): C,
53.34; H, 5.80; N, 2.30. Found: C, 53.47; H, 6.10; N,
2.27%. Yield of 2b: 51%. Anal. Calc. (%): C, 54.76; H,
6.18; N, 2.20. Found: C, 54.00; H, 5.90; N, 2.36%. Yield
of 2c: 84%. Anal. Calc. (%): C, 56.07; H, 6.53; N, 2.11.
Found: C, 55.65; H, 6.32; N, 2.01%. Yield of 2d: 75%.
Anal. Calc. (%): C, 57.26; H, 6.84; N, 2.02. Found: C,
57.21; H, 6.91; N, 2.11%. Yield of 2e: 79%. Anal. Calc.
(%): C, 58.37; H, 7.14; N, 1.94. Found: C, 57.81; H, 6.91;
N, 1.89%. 1H RMN of 2c [Pd(l-OAc)L8]2: 0.89 (t,
J(HH) = 6.0 Hz, 3H, CH3), 1.31–1.74 (m, 12H, CH3–
(CH2)6–), 1.88 (s, 3H, CH3–COO), 3.75 (m, 8H, O–CH2–
CH2–O), 3.90 (m, 4H, Ph–O–CH2–CH2–O), 4.11 (m, 6H,
O–CH2–(CH2)n and Ph–O–CH2–CH2–O), 5.88 (dd,
J(HH) = 8.5 and 2.2 Hz, 1H, CHar–N@C), 6.07 (d,
J(HH) = 2.2 Hz, 1H, CHar–N@C), 6.56 (d, J(HH) =
8.5 Hz, 1H, CHar–N@C), 6.55 (dd, J(HH) = 8.3 and
2.2 Hz, 1H, CHar–C@N), 6.87 (d, J(HH) = 2.2 Hz, 1H,
CHar–C@N), 7.12 (d, J(HH) = 8.3 Hz, 1H, CHar–C@N),
7.45 (s, 1H, CH@N), IR (KBr): 1588 (m(C@N)), 1573
(m(C@O)), 1265, 1224, 1131, 1044 cmꢀ1 (m(C–O–C)).
5 min. Then
a
dichloromethane (distilled) solution
(10 mL) of [Pd(l-OAc)L8]2 (0.0512 g; 3.855 mmol) was
added and the mixture stirred for 2 h. After filtering
through a pad of Kiesselgur, the clear solution was concen-
trated to dryness and the residue was washed with acetone
to give a yellow solid. Yield of 4a: 40%. Anal. Calc. (%): C,
67.38; H, 8.04; N, 1.23. Found: C, 66.85; H, 7.60; N, 1.60%.
Yield of 4b: 73%. Anal. Calc. (%): C, 67.82; H, 8.19; N,
1.20. Found: C, 67.64; H, 7.83; N, 1.02%. Yield of 4c:
70%. Anal. Calc. (%): C, 68.24; H, 8.34; N, 1.17. Found:
C, 68.11; H, 7.98; N, 1.20%. Yield of 4d: 51%. Anal. Calc.
(%): C, 68.64; H, 8.48; N, 1.14. Found: C, 68.20; H, 8.13;
N, 1.33%. Yield of 4e: 51%. Anal. Calc. (%): C, 69.02; H,
8.61; N, 1.12. Found: C, 68.64; H, 8.18; N, 0.88%. 1H
RMN of 4c [Pd(b-diket)L8]: 0.89 (t, J(HH) = 6.0 Hz, 9H,
CH3), 1.28–1.82 (m, 52H, CH3–(CH2)6– and CH3–
(CH2)10–), 3.81 (m, 8H, O–CH2–CH2–O), 3.99 (m, 4H,
O–CH2–(CH2)10), 4.03 (m, 4H, Ph–O–CH2–CH2–O), 4.16
(t, J(HH) = 6.8 Hz, 2H, O–CH2–(CH2)6), 4.22 (m, 4H,
Ph–O–CH2–CH2–O), 6.64 (s, 1H, OC–CH–CO), 6.66 (dd,
J(HH) = 8.5 and 2.4 Hz, 1H, CHar–N@C), 7.34 (d,
J(HH) = 8.5 Hz, 1H, CHar–N@C), 7.36 (d, J(HH) =
2.4 Hz, 1H, CHar–N@C), 6.93 (d, J(HH) = 8.6 Hz, 1H,
CHar–C@N), 7.02 (dd, J(HH) = 8.6 and 2.4 Hz, 1H,
CHar–C@N), 7.14 (d, J(HH) = 2.4 Hz, 1H, CHar–C@N),
6.85 (d, J(HH) = 8.8 Hz, 2H, CHar–C@O), 7.71 (d,
J(HH) = 8.8 Hz, 2H, CHar–C@O), 6.93 (d, J(HH)
= 8.8 Hz, 2H, CHar–C@O), 8.00 (d, J(HH) = 8.8 Hz, 2H,
CHar–C@O), 8.04 (s, 1H, CH@N); IR (KBr): 1603
(m(C@N)), 1590, 1580 (m(C@O)), 1257, 1224, 1176, 1134,
1056 cmꢀ1 (m(C–O–C)).
4.2.3. Preparation of [Pd(l-Cl)Ln]2 3
To a dichloromethane (distilled) solution (20 mL) of
[Pd(l-OAc)L8]2 (0.217 g; 1.7 mmol) under a N2 atmo-
sphere, was added dropwise the stoichiometric amount of
a 2N solution of HCl (3.4 mmol) in ether. After stirring
for 2 h, the solution was concentrated to dryness and the
residue recrystallized from cold acetone. Yield of 3a:
53%. Anal. Calc. (%): C, 51.38; H, 5.52; N, 2.40. Found:
C, 50.95; H, 5.12; N, 2.36%. Yield of 3b: 61%. Anal. Calc.
(%): C, 52.95; H, 5.92; N, 2.29. Found: C, 52.61; H, 5.72;
N, 2.19%. Yield of 3c: 40%. Anal. Calc. (%): C, 54.38; H,
6.29; N, 2.19. Found: C, 54.38; H, 6.08; N, 2.18%. Yield
of 3d: 69%. Anal. Calc. (%): C, 55.69; H, 6.63; N, 2.10.
Found: C, 55.11; H, 6.23; N, 2.23%. Yield of 3e: 64%.
Anal. Calc. (%): C, 56.90; H, 6.95; N, 2.01. Found: C,
4.2.5. General procedure for complexation with NaClO4
To an acetonitrile solution (for derivative 1a) or suspen-
sion (for complexes 2a–4a) of the crown ether derivative,
was added the stoichiometric amount of NaClO4. The
resulting clear solution was stirred for 6 h and then concen-
trated to dryness to give a pale yellow (for [NaCrown1a]-
ClO4) or yellow (for [NaCrown2a]ClO4–[NaCrown4a]-
ClO4) solid. Anal. Calc. (%) for [NaCrown1a]ClO4 Æ H2O:
C, 51.42; H, 6.04; N, 2.4. Found: C, 51.8; H, 5.41; N,
2.55%. Anal. Calc. (%) for [NaCrown2a]ClO4 Æ 3H2O: C,
42.82; H, 5.06; N, 1.85. Found: C, 42.64; H, 4.81; N,
2.23%. Anal. Calc. (%) for [NaCrown3a]ClO4 Æ 3H2O: C,
46.02; H, 5.73; N, 1.73. Found: C, 45.52; H, 5.1; N,
1.72%. Anal. Calc. (%) for [NaCrown4a]ClO4 Æ H2O: C,
60.0; H, 7.32; N, 1.09. Found: C, 60.01; H, 7.09; N,
1.13%. 1H RMN of [NaCrown1a]ClO4: 0.99 (t,
J(HH) = 7.0 Hz, 3H, CH3), 1.48–1.93 (m, 4H, CH3–
1
56.30; H, 6.58; N, 2.10%. H RMN of 3c [Pd(l-Cl)L8]2:
0.89 (t, J(HH) = 7.0 Hz, 3H, CH3), 1.29–1.76 (m, 12H,
CH3–(CH2)6–), 3.78 (m, 8H, O–CH2–CH2–O), 3.94 (m,
4H, Ph–O–CH2–CH2–O), 4.16 (m, 4H, Ph–O–CH2–CH2–
O), 4.22 (m, 2H, O–CH2–(CH2)n), 6.55–7.23 (6H, CHar),

4998
J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
(CH2)6–), 3.73–3.82 (2m, 8H, O–CH2–CH2–O), 3.96 (m,
4H, Ph–O–CH2–CH2–O), 4.03 (t, J(HH) = 6.3 Hz, 2H,
O–CH2–(CH2)2), 4.20–4.27 (2m, 4H, Ph–O–CH2–CH2–
O), 6.86 (m, 3H, CHar–N@C), 6.97 (d, J(HH) = 8.7 Hz,
2H, CHar–C@N), 7.83 (d, J(HH) = 8.7 Hz, 2H, CHar–
C@N), 8.41 (s, 1H, CH@N); IR (KBr): 1606 cmꢀ1
(m(C@N)), 1249, 1121, 1041 cmꢀ1 (m(C–O–C)), 1090,
NaCF3SO3 was added to an acetone solution of 4e, con-
centrated and vacuum dried. In both cases the behavior of
the resulting material under heating was studied by opti-
cal polarized microscopy.
4.4. Extraction experiments
625 cmꢀ1 ðmðClOꢀÞÞ. H RMN of [NaCrown2a]ClO4: 0.93
To a dichloromethane solution (10 mL) of the extracting
Pd compound (5 · 10ꢀ4 M) was added an aqueous solution
of sodium picrate (10 mL, 5 · 10ꢀ5 M) prepared in situ by
mixing solutions of picric acid and sodium hydroxide. The
mixture was vigorously stirred and samples were taken
every 5 min to monitor the diminution of sodium picrate
concentration in the aqueous phase by UV–Vis spectro-
photometry (k = 356 nm), until successive determinations
showed no variation. This was taken as indication that
equilibrium had been reached.
1
4
(m, CH3), 1.41–1.77 (m, CH3–(CH2)2–), 3.66–4.35 (m, O–
CH2–CH2–O, Ph–O–CH2–CH2–O, O–CH2–(CH2)n and
Ph–O–CH2–CH2–O); isomer A: 1.93 (s, 3H, CH3–COO),
5.84 (d, J(HH) = 2.2 Hz, 1H, CHar–N@C), 6.48 (dd,
J(HH) = 8.5 and 2.2 Hz, 1H, CHar–N@C), 7.18 (d,
J(HH) = 8.5 Hz, 1H, CHar–N@C), 6.10 (dd, J(HH) = 8.5
and 2.2 Hz, 1H, CHar–N@C), 6.48 (d, J(HH) = 8.5 Hz,
1H, CHar–C@N), 6.75 (d, J(HH) = 2.2 Hz, 1H, CHar–
C@N), 7.52 (s, 1H, CH@N); isomer B 2.02 (s, 1.5H,
CH3–COO), 2.30 (s, 1.5H, CH3–COO), 6.15 (d,
J(HH) = 2.2 Hz, 1H, CHar–N@C), 6.29 (dd, J(HH) = 8.3
and 2.2 Hz, 1H, CHar–N@C), 6.97 (d, J(HH) = 8.3 Hz,
1H, CHar–N@C), 6.48 (dd, J(HH) = 8.3 and 2.2 Hz, 1H,
CHar–C@N), 6.78 (d, J(HH) = 8.3 Hz, 1H, CHar–C@N),
6.94 (d, J(HH) = 2.2 Hz, 1H, CHar–C@N), 7.73 (s, 1H,
CH@N); IR (KBr): 1588 (m(C@N)), 1573 (m(C@O)), 1265,
1224, 1131, 1044 cmꢀ1 (m(C–O–C)), 1090, 625 cmꢀ1
ðmðClOꢀ4 ÞÞ. 1H RMN (CD3CN) of [NaCrown3a]ClO4:
0.96 (t, J(HH) = 7.3 Hz, 3H, CH3), 143–1.80 (m, 4H,
CH3–(CH2)2–), 3.70–3.72 (2m, 8H, O–CH2–CH2–O), 3.93
(m, 4H, Ph–O–CH2–CH2–O), 4.07 (t, J(HH) = 6.5 Hz,
2H, O–CH2–(CH2)2), 4.30 (m, 4H, Ph–O–CH2–CH2–O),
6.65 (d, J(HH) = 2.0 Hz, 1H, CHar–C@N), 6,74 (dd,
J(HH) = 2.0 and 8.6 Hz, 1H, CHar–C@N), 7.00 (dd,
J(HH) = 2.5 and 8.6 Hz, 1H, CHar–N@C), 7.06 (d,
J(HH) = 2.5 Hz, 1H, CHar–N@C), 7.09 (d, J(HH) =
8.6 Hz, 1H, CHar–N@C), 7.44 (d, J(HH) = 8.2 Hz, CHar–
C@N), 8.03 (s, 1H, CH@N), IR (KBr): 1578 (m(C@N)),
1270, 1228, 1138, 1055 (m(C–O–C)), 1090, 625 cmꢀ1
Acknowledgements
´
We thank the Spanish Direccion General de Investi-
´
gacion (Project CTQ2005-08729/BQU) and the Junta de
´
Castilla y Leon (Project VA099A05) for financial support.
´
J. A. thanks the Ministerio de Educion y Ciencia (Spain)
for a grant.
References
[1] (a) C.J. Pedersen, J. Am. Chem. Soc. 89 (1967) 2495;
(b) C.J. Pedersen, Science 241 (1988) 536.
[2] (a) Q. Xiaotian, Z. Zaide, X. Minggui, Z. Yongchang, T. Ying,
Talanta 46 (1998) 45;
(b) D.T. Rosa, D. Coucouvanis, Inorg. Chem. 37 (1998) 2328;
(c) D.T. Rosa, V.G. Young, D. Coucouvanis, Inorg. Chem. 37 (1998)
5042;
(d) R.E.A. Dillon, C.L. Stern, D.F. Shriver, Solid State Ionics 133
(2000) 247;
´
´
´
(e) P. Breccia, M. Van Gool, R. Perez-Fernandez, S. Martın-
ꢀ
1
ðmðClO4 ÞÞ, 247 cmꢀ1 (m(PdCl)). H RMN of [NaCrown4a]-
ClO4: 0.89 (m, 6H, (CH2)n–CH3), 1.03 (t, J(HH) = 7.0 Hz,
3H, CH3), 1.27–1.82 (m, 44H, CH3–(CH2)n), 3.74–3.81
(2m, 8H, O–CH2–CH2–O), 4.04 (2m, 4H, Ph–O–CH2–
CH2–O, and O–CH2–(CH2)n), 4.14 (m, 2H, O–CH2–
(CH2)2), 4.27 (m, 4H, Ph–O–CH2–CH2–O), 6.64 (s, 1H,
OC–CH–CO), 6.75–6.85–7.13–7.18–7.30 (5m, 6H, CHar–
C@N–CHar), 6.93 (d, J(HH) = 8.3 Hz, 2H, CHar–C@O),
7.77 (d, J(HH) = 8.3 Hz, 2H, CHar–C@O), 7.02 (d,
J(HH) = 8.7 Hz, 2H, CHar–C@O), 7.95 (d, J(HH) =
8.7 Hz, 2H, CHar–C@O), 7.89 (s, 1H, CH@N); IR (KBr):
1603 (m(C@N)), 1590, 1580 (m(C@O)), 1257, 1224, 1176,
1134, 1056 cmꢀ1 (m(C–O–C)), 1090, 625 cmꢀ1 ðmðClOꢀ4 ÞÞ.
´
Santamarıa, F. Gago, P. Prados, J. de Mendoza, J. Am. Chem.
Soc. 125 (2003) 8270.
[3] (a) G.-X. He, F. Wada, K. Kikukawa, S. Shinkai, T. Matsuda, J.
Org. Chem. 55 (1990) 541;
(b) G. Johansson, V. Percec, G. Ungar, D. Abramic, J. Chem. Soc.,
Perkin Trans. 1 (1994) 447;
(c) R.P. Tuffin, K.J. Toyne, J.W. Goodby, J. Mater. Chem. 6 (1996)
1271;
(d) C.F. van Nostrum, Adv. Mater. 8 (1996) 1027;
(e) V. Percec, G. Johansson, G. Ungar, J.P. Zhou, J. Am. Chem. Soc.
118 (1996) 9855;
(f) J.W. Goodby, G.H. Mehl, I.M. Saez, R.P. Tuffin, G. Mackenzie,
´
R. Auzely-Velty, T. Benvegnu, D. Plusquellec, Chem. Commun.
(1998) 2057;
(g) J.A. Schro¨ter, C. Tschierske, M. Wittenberg, J.H. Wendorff,
Angew. Chem. Int. Ed. 36 (1997) 1119;
´
(h) K. Leblanc, P. Berdague, J. Rault, P.-P. Bayle, P. Judeinstein,
4.3. Mesogenic behavior after addition of a sodium salt
Chem. Commun. (2000) 1291;
(i) A. Mourran, U. Beginn, G. Zipp, M. Mo¨ller, Langmuir 20 (2004)
673;
(j) A. Schultz, S. Laschat, A. Saipa, F. Gießelmann, M. Nimtz, J.L.
Schulte, A. Baro, B. Miehlich, Adv. Funct. Mater. 14 (2004) 163;
(k) T. Hegmann, B. Neumann, R. Wolf, C. Tschierske, J. Mater.
Chem. 15 (2005) 1025;
The experiments were carried out in two ways: (a) A
stoichiometric amount of solid NaOOCCH3 was added
to the solids 3e or 4e and the mixture was finely
grounded; (b)
a
stoichiometric amount of solid

J. Arias et al. / Journal of Organometallic Chemistry 691 (2006) 4990–4999
4999
´
(l) N. Steinke, W. Frey, A. Baro, S. Laschat, C. Drees, M. Nimtz, C.
Ha¨gele, F. Giesselmann, Chem. Eur. J. 12 (2005) 1026.
[4] (a) A. Liebmann, C. Mertesdorf, T. Plesnivy, H. Ringsdorf, J.H.
Wendorff, Angew. Chem. Int. Ed. Engl. 30 (1991) 1375;
(b) G. Lattermann, S. Schmidt, R. Kleppinger, J.H. Wendorff, Adv.
Mater. 4 (1992) 30;
(b) J. Buey, L. Dıez, P. Espinet, H.-S. Kitzerow, J.A. Miguel, Chem.
Mater. 8 (1996) 2375;
´
(c) J. Buey, L. Dıez, P. Espinet, H.-S. Kitzerow, J.A. Miguel, Appl.
Phys. B-Lasers Opt. 66 (1998) 355;
(d) J. Buey, S. Coco, L. Dıez, P. Espinet, J.M. Martın-Alvarez, J.A.
Miguel, S. Garcıa-Granda, A. Tesouro, I. Ledoux, J. Zyss, Organo-
´
´
´
´
(c) F. Neve, M. Ghedini, A.M. Levelut, O. Francescangeli, Chem.
Mat. 6 (1994) 70;
(d) S. Schmidt, G. Lattermann, R. Kleppinger, J.H. Wendorff, Liq.
Cryst. 16 (1994) 693;
(e) F. Neve, M. Ghedini, A.M. Levelut, O. Francescangeli, Liq.
Cryst. 21 (1996) 625;
(f) H. Richtzenhain, A.J. Blake, D.W. Bruce, I.A. Fallis, W.-S. Li,
M. Shro¨der, Chem. Commun. (2001) 2580;
metallics 17 (1998) 1750.
[10] (a) N. Usol’tseva, P. Espinet, J. Buey, J.L. Serrano, J. Mater. Chem.
7 (1997) 215;
(b) N. Usol’tseva, P. Espinet, J. Buey, K. Praefcke, D. Blunk, Mol.
Cryst. Liq. Cryst. 299 (1997) 457.
[11] H. Onoue, K. Minami, K. Nakagawa, Bull. Chem. Soc. Jpn. 43
(1970) 3480.
[12] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, fifth ed., Wiley Interscience, 1997.
´
(g) S. Suarez, O. Mamula, D. Imbert, C. Piguet, J.-C.G. Bu¨nzli,
´
Chem. Commun. (2003) 1226.
[13] (a) P. Espinet, E. Lalinde, M. Marcos, J. Perez, J.L. Serrano,
[5] H. Engelkamp, S. Middelbeek, R.J.M. Nolte, Science 284 (1999) 785.
[6] (a) P. Espinet, M.A. Esteruelas, L.A. Oro, J.L. Serrano, E. Sola,
Coord. Chem. Rev. 117 (1992) 215;
Organometallics 9 (1990) 555;
´
(b) P. Espinet, J. Perez, M. Marcos, M.B. Ros, J.L. Serrano, J.
Barbera´, A.M. Levelut, Organometallics 9 (1990) 2028;
´
´
(b) J.L. Serrano (Ed.), Metallomesogens, VCH, Weinheim, Germany,
1996.
(c) L. Dıez, P. Espinet, J.A. Miguel, M.P. Rodrıguez-Medina, J.
Organomet. Chem. 690 (2005) 261.
[7] M.J. Baena, J. Buey, P. Espinet, H.-S. Kitzerow, G. Heppke, Angew.
Chem., Int. Ed. Engl. 32 (1993) 1201.
[8] (a) M.J. Baena, P. Espinet, M.B. Ros, J.L. Serrano, A. Ezcurra,
Angew. Chem., Int. Ed. Engl. 32 (1993) 1203;
[14] (a) C.J. Pedersen, J. Am. Chem. Soc. 89 (1967) 7017;
(b) G.W. Gokel, W.M. Leevy, M.E. Weber, Chem. Rev. 104 (2004)
2723.
[15] J.D. Owen, Dalton Trans. (1981) 1066, and references therein.
´
´
(b) M.J. Baena, J. Barbera, P. Espinet, A. Ezcurra, M.B. Ros, J.L.
[16] M.J. Baena, J. Buey, P. Espinet, C.E. Garcıa-Prieto, J. Organomet.
Serrano, J. Am. Chem. Soc. 116 (1994) 1899;
(c) N.J. Thompson, J.L. Serrano, M.J. Baena, P. Espinet, Chem.
Eur. J. 2 (1996) 214;
Chem. 690 (2005) 998.
[17] R.C. Larock, Comprehensive Organic Transformations, VCH, New
York, 1989, p. 446.
(d) N.J. Thompson, R. Iglesias, J.L. Serrano, M.J. Baena, P. Espinet,
J. Mater. Chem. 6 (1996) 1741.
[18] T.A. Stephens, S.M. Morehouse, A.R. Powell, J.P. Heffer, G.
Wilkinson, J. Chem. Soc. (1965) 3632.
´
´
[9] (a) P. Espinet, J. Etxebarrıa, C.L. Folcia, J. Ortega, M.B. Ros, J.L.
[19] J. Barbera, C. Cativiela, J.L. Serrano, M.M. Zurbano, Adv. Mater. 3
Serrano, Adv. Mater. 8 (1996) 745;
(1991) 602.