Synthesis and mesomorphism of fluoroalkylated organometallic mesogens

Article abstract of DOI:10.1039/b511758e

The first examples of liquid crystalline chloro-bridged dinuclear palladium organyls carrying semiperfluorinated alkyl chains at their peripheries have been synthesised. The liquid crystalline properties were investigated using polarised optical microscop

Full text of DOI:10.1039/b511758e

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Synthesis and mesomorphism of fluoroalkylated organometallic mesogens{
Belk|z Bilgin-Eran,*a Carsten Tschierske,b Siegmar Dielec and Ute Baumeisterc
Received 17th August 2005, Accepted 1st November 2005
First published as an Advance Article on the web 23rd November 2005
DOI: 10.1039/b511758e
The first examples of liquid crystalline chloro-bridged dinuclear palladium organyls carrying
semiperfluorinated alkyl chains at their peripheries have been synthesised. The liquid crystalline
properties were investigated using polarised optical microscopy, differential scanning calorimetry
and X-ray scattering. Compounds with six semifluorinated chains and two alkyl chains show
hexagonal columnar liquid-crystalline phases with dramatically enhanced mesophase stabilities
compared to the related hydrocarbon derivatives, which have only monotropic discotic nematic
phases. Compounds with only four semifluorinated alkyl chains and two alkyl chains exhibit
enantiotropic smectic A and monotropic smectic C mesophases. Preliminary experiments with
mixed systems (eight-chain compounds and six-chain compounds, as well as binary systems with
dodecane or TNF) were also carried out.
In contrast to purely organic liquid crystalline materials,
Introduction
where the influence of fluorination was studied in several
The replacement of hydrogen by fluorine is extremely
cases, metal containing liquid crystals with fluorinated chains
are rare.11
important in materials design. According to its high electro-
negativity, low polarisibility, and small size the fluorine atom
Metal containing liquid crystals are especially important
makes considerable changes in the physical and chemical
since these materials can expand the range of the technological
behaviour of fluorinated compounds.1–4 The fluorine–carbon
applications and physical properties exhibited by traditional
bond is very strong, but intramolecular interactions of fluoro-
liquid crystals due to the redox properties and polarisability of
carbons are weak. This results in an exceptional combination
the metal centres. The presence of metal atoms in the complexes
of properties in fluorocarbons, such as thermal inertness,
induces properties such as colour, paramagnetism, etc.12–13
incompatibility with polar and aliphatic molecules and high
Disc-shaped ortho-palladated and -platinated benzalimines
dielectric constants. Therefore, fluorinated compounds have
are a widely studied type of organometallic liquid crystals.14–18
found broad technical applications in many different fields,
These metal centres can provide the possibility to obtain
such as surface coating, in electronics, optics, biomedicine,
mesomorphism in compounds that exhibit molecular geo-
and much research has contributed to increase the knowledge
metries which are impossible to obtain with purely organic
of these compounds within the field of self-organised mole-
structures, i.e., square planar,14–18 octahedral,19 etc. Previously
cular systems.1–4
reported dinuclear ortho-metallated palladium(II) complexes
Compounds containing fluorinated alkyl chains are also
carrying four or less alkyl chains show nematic and smectic
mesophases,12 whereas related compounds with eight alkyl
of increasing interest for the design of liquid crystalline
materials. Introduction of perfluorinated alkyl chains into
chains have a more elliptical or sheet-like shape, which leads
classical calamitic liquid crystals and also into discotic LC
to the formation of nematic–discotic mesophases.14–15 Related
leads to a significant stabilisation of smectic and columnar
compounds with six chains have not been reported.
mesophases, respectively, due to increased segregation of these
In order to evaluate the influence of the fluorophobic
chains from the rigid segments, as well as from polar and
aliphatic units.3–10 In addition, the mesophase type can be
effect on the self-organisation of these sheet-like metallo-
mesogens we have synthesised new palladium organyls in
modified due to the increased volume of perfluorinated chains.
which the alkyl chains are replaced by partially fluorinated
Furthermore, the alignment properties of fluorinated LC
chains. In addition, the first examples of dinuclear Pd(II)
materials are different from related materials with hydro-
carbon chains,6 due to the distinct interaction parameters
organyls with six peripheral chains are reported. The
structure–property relations were studied by changing the
of the fluorinated segments with surfaces, which is also of
number of semifluorinated alkyl chains and the length of
importance for the practical application of such materials.
fluorinated segments.20
a
¨
Department of Chemistry, Y|ld|z Teknik Universitesi, Davutpas¸a
Yerles¸im Birimi, TR-34210, Esenler, Istanbul, Turkey.
E-mail: bilgineran@ttnet.net.tr
Results and discussion
bInstitute of Organic Chemistry, Universita¨t Halle-Wittenberg, Kurt
Mothes-Str. 2, D-06120, Halle, Germany
Synthesis
cInstitute of Physical Chemistry, Universita¨t Halle-Wittenberg,
Mu¨hlpforte 1, D-06118, Halle, Germany
The first step in the sequence of reactions for the preparation
of the sheet-like dipalladium mesogens 5b, c and 6a–c with
{ Electronic supplementary information (ESI) available: X-ray scatter-
ing conditions and data. See DOI: 10.1039/b511758e
semifluorinated alkyl chains consists of the synthesis of the
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Scheme 1 Synthesis of the fluorinated aldehydes 1 and 2.
semifluorinated 2,3,4-trisubstituted (1) or 3,4-disubstituted (2)
benzaldehydes (see Scheme 1).
These aldehydes were obtained by reaction of 2,3,4-
trihydroxy- and 3,4-dihydroxybenzaldehyde, respectively,
with the appropriate semifluorinated alkyl bromides, using
K2CO3 as base and DMF as solvent.6a,b For the synthesis
of the semifluorinated alkyl bromides, the key step is the
[Pd(PPh3)4] catalysed radical addition of perfluoroalkyl
iodides to olefin terminated alcohols (3-butenol, 5-hexenol).6b
Reduction of the iodo group with LiAlH4, followed by
bromination with HBr gave the corresponding semifluorinated
alkyl bromides6b (see Scheme 1).
The synthesis of the imine ligands 3b, c and 4a–c as well
as their palladium complexes 5b,c and 6a–c is outlined in
Scheme 2. The dinuclear chloro-bridged palladium mesogens 5
and 6 were obtained by ortho-palladation of the imine 3 and 4,
respectively, using [PdCl2(C6H5CN)2], whereby yields of
27–38% have been achieved.
1
The molecular structures were elucidated using H and 13C
NMR, MS, and also by elemental analysis (see Experimental
section). Furthermore, 1H and 13C NMR spectroscopic data
for the dipalladium organyls 5 and 6 are in line with planar
structures and antiparallel orientations of their ligands, as
previously shown for the hydrocarbon analogues by X-ray
analysis.15a,18
Liquid crystalline properties
The mesomorphic properties of the obtained compounds 5
and 6 were investigated using polarised light optical micro-
scopy, differential scanning calorimetry and X-ray scattering.
The transition temperatures, corresponding enthalpy values
and mesophase types observed for both series of dinuclear
fluoroalkylated palladium organyls 5 and 6 are summarised
in Table 1.
Scheme 2 Synthesis of the dinuclear fluorinated ortho-palladated
mesogens 5 and 6.
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Table 1 Phase transition temperaturesa T (uC) and transition enthalpiesa DH (kJ mol21) of semifluorinated chloro-bridged dinuclear palladium
organyls 5 and 6. Cr: crystalline, Colh: hexagonal columnar, Sm: smectic and Iso: isotropic phase
Comp.
R
R9
T/uC (DH/kJ mol21
)
5b
5c
6a
6b
6c
a
C4F9(CH2)6
C6F13(CH2)4
C10H21
C4F9(CH2)6
C6F13(CH2)4
C4F9(CH2)6
C6F13(CH2)4
H
H
H
Cr 100.7 (87.3) Colh 164.5 (3.7) Iso
Cr 115.3 (62.6) Colh 226.7 (5.6) Iso
Cr 127.8 (57.7) {SmC 122.3 (0.5)} SmA 146.8 (5.3) Iso
Cr 129.1 (42.6) {SmC 106.8 (0.6)} SmA 168.2 (2.0) Iso
Cr 130.5 (39.3) SmA 174.8 (1.6) Iso
Perkin-Elmer DSC-7; heating rates 10 K min21 for the melting and clearing process. The values of monotropic transition are given in {...}.
Columnar phases of the octasubstituted compounds 5. For
both disc-shaped chloro-bridged dipalladium organyls with six
semifluorinated alkyl chains and two alkyl (hexyl) chains 5b
and 5c, enantiotropic liquid crystalline behaviour is observed.
The mesophase exhibits spherulitic textures, accompanied by
large homeotropically aligned regions, indicating an optical
uniaxial columnar mesophase (see Fig. 1).
about 0.55 nm, and the other, much weaker one has its
maximum at h # 10.5u, corresponding to a d value of about
0.42 nm. Fig. 2c shows as an example the corresponding
scattering diagram of 5c with two Lorentz curves fitted to the
experimental intensities. The stronger inner diffuse scattering
forms a closed ring in the 2D patterns with only a slight
intensity variation revealing a nearly isotropic distribution of
the corresponding distances of the scattering centres (black
line in Fig. 2d for 5b). A maximum of the weaker outer
scattering could be found at the equator of the pattern for the
fiber-like aligned sample (grey line in Fig. 2d for compound
5b). Therefore, the latter one is most likely caused by the
stacking of the hydrocarbon parts of the molecules within the
columns with a mean stacking distance of 0.42 nm, whereas
the inner one (0.55 nm) is due to the mean distance between
the disordered fluorinated chains forming the continuum
surrounding these columns.
X-ray scattering patterns (Fig. 2a) of the columnar
mesophases of 5b and 5c show three Bragg reflections in the
small-angle region with d-value ratios of 1:1/!3:1/2. The 2D
patterns of aligned samples (Fig. 2b) confirm the hexagonal
arrangement of the columns for both compounds. The lattice
parameters ahex are equal within experimental error (ahex
=
3.0 nm) without detectable temperature dependence (between
130 and 25 uC for 5b and between 130 and 170 uC for 5c).
There are two types of diffuse scattering in the wide angle
region, one has a strong maximum at h # 8u with a d value of
So, compounds 5b and 5c are the first sheet-like halogen
bridged dinuclear palladium(II) complexes showing columnar
mesophases. Previously synthesised related hydrocarbon
derivatives with the same substitution pattern had hexyloxy
chains instead of the perfluorinated chains and showed only
monotropic discotic nematic phases.14–15 Though a direct
comparison is not possible due to the different chain length the
results show that replacing these alkyl chains by fluorocarbon
chains substantially elevates the clearing temperatures and
facilitates the formation of columnar phases. This transition
of the ND phase to a Colh phase is analogous to the change
from nematic to smectic phases in calamitic systems. These
broad mesophase ranges result from a dramatic stabilisation
of the liquid-crystalline state due to a better segregation of
these chains from the metallorganic rigid cores, whereas the
organisation in columns is the result of the efficient space
filling of the periphery by the long and fluorinated chains.
Fig. 1 Polarised light optical photomicrograph of the hexagonal
columnar phase of 5b at 156 uC (crossed polarisers, the dark regions
are homeotropically aligned regions, i.e., the columns are aligned
perpendicular to the glass plates).
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Fig. 2 X-Ray diffraction patterns of the hexagonal columnar phases: (a) scattering diagram of a powder-like sample of 5b at 130 uC showing the
Bragg reflections in the small angle region; (b) 2D pattern of an aligned sample of 5c at 170 uC; (c) scattering diagram of a powder-like sample of 5c
at 150 uC showing the diffuse scattering in the wide angle region with Lorentz-fit to the intensities (black line: experimental intensity, gray lines:
individual curves for the two types of scattering, smooth black line: resulting curve); (d) comparison of the distribution of the intensity integrated
over 2h from 15 to 17u (black line, d # 0.55 nm) and from 20 to 24u (gray line, d # 0.42 nm) for the two kinds of diffuse scattering, obtained for an
aligned sample of 5b, relative intensity calculated by Irel = I (140 uC)/I (isotropic liquid).
Binary systems of 5b and 5c. The columnar mesophases can
be further stabilized by doping with the electron acceptor
2,4,7-trinitrofluorenone (TNF). Both compounds form charge-
transfer (CT)-complexes with TNF as indicated by a change
of colour from yellow to brown–red. Contact preparations of
5b and 5c with TNF exhibit a highly viscous mesophase up to
226 uC and 255 uC, respectively. On cooling from the isotropic
liquid (see Fig. 3), a texture can be found, which is very similar
to that observed for the Colh phases of TNF complexes of
the dinuclear palladium and platinum analogous containing
alkyl peripheral chains.14–15,21 Homeotropic domains indicate
an optically uniaxial, most probably hexagonal, columnar
phase. Though these mixed systems were not investigated in
more detail it is likely that the hexagonal columnar structure
of the mesophase is retained, probably with a more defined
intermolecular distance within the columns.21
For the previously reported ortho-metallated tetranuclear
palladium and platinum mesogens it was also shown that
the columnar phases are replaced by nematic-columnar
phases if non-polar solvents were added.16–17 Also the
mesomorphic properties of the fluoroalkyl-substituted
derivatives are influenced by hydrocarbon solvents. In
contact preparations of 5b and 5c with dodecane,
a
ribbon of an induced columnar phase can be seen beside
the Colh phase of the pure compounds (see, for example,
Fig. 4). Homeotropic domains indicate an optically
uniaxial columnar phase, most likely with hexagonal
symmetry. Hence, there seems to be no change of the
phase symmetry by the solvent but it is interesting to
note that the self-organisation of these mesogens with a
perfluorinated periphery can be influenced by lipophilic
solvents.
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Fig. 3 Polarised light optical photomicrograph of the contact region
between 5c (top) and TNF (bottom) at 229 uC.
Fig. 4 Polarized light optical photomicrograph of the contact region
between 5c (bottom) and dodecane (top) at 101 uC.
Smectic phases of the hexasubstituted compounds 6. The
compounds 6a–c, containing six peripheral chains (6b and 6c
with four semifluorinated alkyl chains) exhibit an enantio-
tropic smectic A phase, that can be detected by the typical fan-
like texture which can be aligned homeotropically. For 6a
and 6b, an additional phase transition, characterized by the
formation of a schlieren texture in the homeotropic regions of
the SmA phase can be observed. This schlieren texture is
characterised by four-brush disclinations and hence it can be
assigned to a tilted smectic (SmC) phase. This mesophase is
only monotropic (metastable).
X-Ray investigations confirm the layer structures for
compounds 6b and c. Layer reflections of the first and the
second order can be found on the meridian of the 2D X-ray
patterns (e.g. Fig. 5). The corresponding layer spacing
amounts to d = 3.0 nm for both compounds. The diffuse
scattering measured for 6b has maxima at h # 7.7u (d #
0.58 nm) and h # 9.0u (d # 0.49 nm). As in case of the
columnar phase, the inner one (d # 0.58 nm) is distributed
isotropically and is assigned to the disordered fluorinated
chains, while the outer one (d # 0.49 nm) has maxima at
the equator of the pattern (Fig. 5) and corresponds to the
lateral distances of the molecules within the smectic A layers.
This value is significantly larger than the typical value of face-
to-face arranged aromatic cores (typically around ca 0.36 nm)
and this indicates that despite of their sheet-like shape the
molecules are rotationally disordered. The monotropic SmC
Fig. 5 2D X-ray pattern of a partially aligned sample of 6b in the
smectic A phase at 140 uC (a) original pattern, (b) as (a), but the
scattering of the isotropic liquid has been subtracted from the original
pattern to show the slight enhancement of the diffuse outer scattering
on the equator of the pattern, (c) comparison of the distribution of the
intensity integrated over 2h from 14 to 16u (line 1, d # 0.58 nm) and
from 16 to 19u (line 2, d # 0.49 nm) for the two kinds of diffuse
scattering, relative intensity calculated by Irel = I(140 uC)/I(isotropic
liquid), line 3 with the maximum shows the position of the layer
reflection (2h = 2.94u).
phases could not be investigated by X-ray diffraction, because
the samples crystallise upon cooling.
Comparison of the non-fluorinated compound 6a with the
fluorinated analogues 6b and 6c shows that the clearing points
and the mesophase ranges are increased significantly with
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increasing degree of fluorination whereas the melting points
remain nearly the same and the stability of the tilted smectic C
mesophase is reduced.
Interestingly, though the shape of the organometallic core is
sheet-like for all investigated compounds and should favour
the formation of columnar phases, reduction of the number of
chains by only two gives rise to a transition from a columnar
to a lamellar organisation. It seems that six chains, though
some of them are fluorinated, are not enough to fill the space
sufficiently and to promote a columnar phase.
Binary systems of series 6 with TNF. The hexasubstituted
dinuclear palladium organyls 6a–c form charge-transfer
complexes with TNF. The contact preparations of 6a–c with
TNF exhibit a stabilised smectic A mesophase up to 185 uC,
214 uC and 227 uC, respectively. On cooling from the isotropic
liquid, the typical fan-like texture of a smectic A phase
appeared. A schlieren texture, as typical for biaxial smectic
phases (SmC or SmAb),22 however, could not be obtained and
hence, the induction of such a biaxial phase can be excluded.
The investigation of the contact regions of 6a–c by polarising
microscopy shows that only the smectic A phase is stabilised
and there is no change of the mesophase type.
Binary system of 5b and 6b. In order to check if additional
mesophases could be expected for molecules that have a
number of chains which is in between those of compounds 5b
and 6b, the contact region between the SmA phase of 6b and
the Colh phase of 5b was investigated. The mesophase of the
pure compound is strongly destabilised, leading to an isotropic
fluid ribbon in the contact region. Only at the borderline to the
smectic compound 6b a mesophase with a schlieren texture is
induced (i.e., below the clearing temperatures of the individual
compounds) (see Fig. 6a), which slowly grows towards the
columnar phase of compound 5b and it coalesces with this
phase (but the induced phase is still separated by a sharp
borderline from the Colh phase). The schematic phase diagram
observed on cooling of this binary system is shown in Fig. 6b.
Neither cubic nor any other 3D-ordered intermediate phase
as typical for other lamellar-columnar transitions could be
detected.23
Fig. 6 (a) Polarised light optical photomicrograph of the contact
region between 5b and 6b at ca. 68 uC. (b) Schematic binary phase
diagram of the system 5b and 6b; crystalline phases are not shown.
regarded as first examples of semi-fluorinated ortho-palladated
metallomesogens.
The substitution pattern of the metallomesogens 5 and 6 has
a significant influence on mesophase stability and mesophase
type. By increasing the number of semifluorinated alkyl
chains attached to the imine ligands, a transition from lamellar
to columnar organisation was found. Whereas the number of
fluorine atoms has a minor effect on the melting points a
strong increase in the clearing points by increasing the degree
of fluorination could be observed. Moreover, the increase of
the number of fluorine atoms in the side chains broadens the
mesophase range. Incorporating fluorinated chains leads to the
appearance of more ordered (ND phases are replaced by Colh
phases) and more stable mesophases (increased clearing tem-
peratures) due to the incompatibility and micro-segregation of
the various molecular parts. The pronounced alignment of
the columns (Colh phases of complexes) perpendicular to the
surfaces is of interest for the design of metallomesogens for
application in photovoltanic and photoconducting devices.
The schlieren texture of this induced intermediate phase is
different from a SmC schlieren texture, but very similar to a
nematic schlieren texture. Therefore, we conclude that the
lamellar to columnar transition is discontinuous, as also
reported for half-disc-like molecules.24 The intermediate
phases are more disordered than the mesophases of the pure
compounds, i.e., isotropic liquid25–26 or only orientationally
ordered (nematic).
Experimental
Conclusion
The characterization of the compounds1–6 presented here are
based on various spectroscopic data, e.g., 1H-, 13C-NMR
(Varian Unity 500 and Varian Unity 400 spectrometers, in
CDCl3 solutions) with tetramethylsilane as internal standard,
MS [AMD 402 (electron impact, 70 eV)]. Microanalyses were
performed using a Leco CHNS-932 elemental analyzer. Only
structurally relavent resonances are given in the NMR data.
Two new series of dinuclear chloro-bridged ortho-palladated
benzalimine complexes 5 and 6, containing fluorocarbon
terminal chains (and, in addition compound, 6a containing
only alkyl chains), have been synthesised. The periphery of
these metallomesogens, the number of semifluorinated alkyl
chains and the number of fluorine atoms in the fluoroalkyl
chains has been varied. Compounds
5 and 6 can be
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Transition temperatures were measured using a Mettler FP
82 HT hot stage and control unit in conjunction with a Nikon
Optiphot 2 polarizing microscope, and these were confirmed
using differential scanning calorimetry (Perkin-Elmer DSC-7,
heating and cooling rate: 10 K min21).
110.92 (3d; 3 arom. CH), 68.40, 68.38 (2t; 2 OCH2 groups).
C27H20F26O3 (886.4). MS(EI): m/z (%) = 886 (45) [M+], 512
(16) [M+-C10H8F13], 138 (100) [M+- 2 6 C10H8F13].
Synthesis of the imine ligands 3b, c and 4a–c
All X-ray investigations were carried out using Cu Ka
radiation (radiation monochromated by a Ni filter for the area
detector and with a quartz monochromator for the Guinier
devices). The powder-like samples in capillary tubes (diameter:
1 mm) were investigated by a Guinier film camera and a
Guinier goniometer (HUBER Diffraktionstechnik, Germany).
X-Ray patterns of the aligned samples (drop on a glas plate,
surface aligned at the sample–air interface) were taken by an
area detector HI-Star (Siemens, Germany). Experimental
conditions for X-ray scattering are available in the electronic
supplementary information (ESI){.
The imine 3b, c and 4a–c were prepared in the usual way14,15
by a p-toluenesulfonic acid (40 mg) catalyzed condensation of
the semifluorinated alkyloxybenzaldehydes 1 or 2 (5 mmol)
with 4-n-hexylaniline (7 mmol) (commercially available) in
50 ml toluene and purified by column chromatography on
basic aluminum oxide using petroleum ether–ethyl acetate
(20 : 1 to 5 : 1) as eluent.
Compounds 3b. Yield: 4.6 g (76%) of light yellow oil.
1H-NMR d = 8.72 (s; HCLN), 7.84, 6.73 (2d, J # 8.9 Hz each;
2 arom. H of the benzyliden ring), 7.17, 7.10 (2d, J # 8.5 Hz
each; 4 arom. H of the N-substituted phenyl ring), 4.07, 4.03,
3.98 (3t, J # 6.5 Hz each; 3 OCH2 groups), 2.60 (t, J # 7.8 Hz;
a-CH2 group). 13C-NMR: d = 155.96, 153.98, 150.27, 141.19,
140.53, 123.39 (6s; 6 arom. C), 155.20 (d; HCLN), 129.00,
122.50, 120.78, 108.76 (4d; 2,1,2 and 1 arom. CH, respectively),
74.62, 73.38, 68.54 (3t; 3 OCH2 groups), 35.51 (t; a-CH2
group). C49H56F27NO3 (1219.9): calcd. C 48.24, H 4.63, N
1.15; found C 48.50, H 4.42, N 1.08.
The preparation procedures for 3,4-didecyloxybenzaldehyde
(2a) was as in the literature.27
Synthesis of the new semifluorinated aldehydes 1b, c and 2b, c
Following earlier descriptions,14 their synthesis was carried out
by etherification of different 2,3,4- or 3,4-hydroxy substituted
benzaldehydes (15 mmol) with the corresponding semi-
fluorinated alkyl bromide (54 mmol). The crude products
were purified by column chromatography on silica gel, eluting
with petroleum ether (b.p. 30–70 uC)–ethyl acetate (10 : 1).
Compounds 3c. Yield: 4.9 g (69%) of white crystals, phase
transition temperatures: Cr 47 uC (27.6 kJ mol21) {Col 40 uC
1
(1.9 kJ mol21)} Iso. H-NMR d = 8.70 (s; HCLN), 7.86, 6.75
Compounds 1b. Yield: 14.9 g (94%) of white crystals, mp:
1
39 uC (39.1 kJ mol21). H-NMR: d = 10.22 (s; CHO), 7.56,
(2d, J # 8.8 Hz each; 2 arom. H of the benzyliden ring), 7.17,
7.10 (2d, J # 8.5 Hz each; 4 arom. H of the N-substituted
phenyl ring), 4.07–3.99 (m; 3 OCH2 groups), 2.60 (t, J #
7.8 Hz; a-CH2 group). 13C-NMR: d = 155.55, 153.74, 150.04,
141.02, 140.66, 123.58 (6s; 6 arom. C), 154.67 (d; HCLN),
129.02, 122.86, 120.75, 108.94 (4d; 2,1,2 and 1 arom. CH,
respectively), 74.24, 72.94, 68.14 (3t; 3 OCH2 groups), 35.54 (t;
a-CH2 group). C49H44F39NO3 (1435.9): calcd. C 40.99, H 3.09,
N 0.97; found C 41.05, H 3.00, N 1.08.
6.71 (2d, J # 8.8 Hz each; 2 arom. H), 4.14, 4.04, 3.96 (3t, J #
6.5 Hz each; 3 OCH2 groups). 13C-NMR: d = 188.76 (d;
CHO), 158.84, 156.43, 140.96, 123.61 (4s; 4 arom. C), 124.08,
108.23 (2d; 2 arom. CH), 75.11, 73.46, 68.68 (3t; 3 OCH2
groups).
Compounds 1c. Yield: 17.8 g (93%) of white crystals, mp
62 uC (40.0 kJ mol21). 1H-NMR d = 10.20 (s; CHO), 7.59, 6.74
(2d, J # 8.8 Hz each; 2 arom. H), 4.14, 4.08, 3.99 (3t, J #
5.8 Hz each; 3 OCH2 groups). 13C-NMR: d = 188.39 (d; CHO),
158.49, 156.15, 141.00, 123.87 (4s; 4 arom. C), 124.72, 108.50
(2d; 2 arom. CH), 74.77, 73.04, 68.33 (3t; 3 OCH2 groups).
Compounds 4a. Yield: 2.3 g (81%) of yellow crystals, mp
1
51 uC (47.9 kJ mol21). H-NMR d = 8.33 (s; HCLN), 7.56 (s,
broad; arom. H), 7.26 (dd, J # 8.3 and J # 1.5 Hz; arom. H),
7.17, 7.12 (2d, J # 8.2 Hz each; 4 arom. H of the N-substituted
phenyl ring), 6.89 (d, J # 8.3 Hz; arom. H), 4.08, 4.04 (2t, J #
6.6 Hz each; 2 OCH2 groups), 2.60 (t, J # 7.7 Hz; a-CH2
group). 13C-NMR: d = 159.17 (d; HCLN), 152.04, 149.93,
149.47, 140.32, 129.63 (5s; 5 arom. C), 128.98, 123.90, 120.70,
112.59, 111.45 (5d; 2,1,2,1 and 1 arom. CH, respectively),
69.25, 69.19 (2t; 2 OCH2 groups), 35.53 (t; a-CH2 group).
C39H63NO2 (577.9): calcd. C 81.05, H 10.99, N 2.42; found C
80.90, H 10.76, N 2.44. MS(EI): m/z (%) = 577 (100) [M+], 437
(7) [ M+-C10H21].
Compounds 2b. Yield: 9.8 g (88%) of light yellow oil.
1H-NMR d = 9.81 (s; CHO), 7.40 (dd, J # 8.3 and J # 1.8 Hz;
arom. H-6), 7.37 (d, J # 1.8 Hz; arom. H-2), 6.93 (d, J #
8.3 Hz; arom. H-5), 4.07, 4.04 (2t, J # 5.2 Hz each; 2 OCH2
groups). 13C-NMR: d = 190.77 (d; CHO), 154.49, 149.36,
130.09 (3s; 3 arom. C), 126.57, 111.89, 111.09 (3d; 3 arom.
CH), 68.83, 68.82 (2t; 2 OCH2 groups). C27H28F18O3 (742.5).
MS(EI): m/z (%) = 742 (87) [M+], 440 (23) [M+-C10H12F9], 138
(100) [M+-2 6 C10H12F9].
Compounds 2c. Yield: 10.9 g (82%) of white crystals, mp
1
Compounds 4b. Yield: 3.2 g (70%) of white crystals, mp 60 uC
(46.7 kJ mol21). 1H-NMR d = 8.34 (s; HCLN), 7.58 (s, broad;
arom. H), 7.26 (dd, J # 8.3 and J # 1.5 Hz; arom. H), 7.17,
7.12 (2d, J # 8.2 Hz each; 4 arom. H of the N-substituted
phenyl ring), 6.90 (d, J # 8.3 Hz; arom. H), 4.09, 4.05 (2t, J #
6.4 Hz each; 2 OCH2 groups), 2.60 (t, J # 7.7 Hz; a-CH2
64 uC (45.6 kJ mol21). H-NMR d = 9.82 (s; CHO), 7.42 (dd,
J # 8.3 and J # 1.8 Hz; arom. H-6), 7.38 (d, J # 1.8 Hz;
arom. H-2), 6.94 (d, J # 8.3 Hz; arom. H-5), 4.09, 4.07 (2t, J #
4.3 Hz each; 2 OCH2 groups). 13C-NMR: d = 190.53 (d;
CHO), 154.09, 149.09, 130.19 (3s; 3 arom. C), 126.63, 111.80,
1142 | J. Mater. Chem., 2006, 16, 1136–1144
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group). 13C-NMR: d = 159.16 (d; HCLN), 151.83, 149.87,
149.32, 140.52, 129.77 (5s; 5 arom. C), 129.06, 124.13, 120.74,
112.42, 111.11 (5d; 2,1,2,1 and 1 arom. CH, respectively),
68.78, 68.74 (2t; 2 OCH2 groups), 35.49 (t; a-CH2 group).
C39H45F18NO2 (901.7): calcd. C 51.95, H 5.03, N 1.55; found
C 52.15, H 5.30, N 1.39. MS(EI): m/z (%) = 901 (100) [M+], 599
(10) [M+-C10H12F9].
Compounds 6a. Yield: 0.23 g (33%) of yellow crystals.
1H-NMR d = 7.75 (s; 2 HCLN), 7.23, 7.12 (2d, J # 7.1 Hz
each; 8 arom. H of the N-substituted phenyl rings), 6.84,
6.80 (2s; 4 arom. H of the Pd-substituted phenyl rings),
3.98 (s, broad, 2 OCH2 groups), 3.89 (t, J # 6.6 Hz; 2 OCH2
groups), 2.58 (t, J # 7.8 Hz; 2 a-CH2 groups). 13C-NMR: d =
172.84 (d; 2HCLN), 150.81, 149.05, 146.59, 146.37, 142.23,
137.43 (6s; 12 arom. C), 128.36, 123.12, 117.42, 114.24 (4d; 4,
4, 2 and 2 arom. CH, respectively), 70.24, 68.78 (2t; 4 OCH2
groups), 35.65 (t; 2 a-CH2 groups). C78H124Cl2N2O4Pd2
(1437.6): calcd. C 65.17, H 8.69, N 1.95; found C 65.05, H
8.77, N 2.03.
Compounds 4c. Yield: 4.0 g (77%) of white crystals, mp 73 uC
(36.5 kJ mol21). 1H-NMR d = 8.34 (s; HCLN), 7.59 (s, broad;
arom. H), 7.28–7.26 (m; arom. H), 7.18–7.13 (m; 4 arom. H of
the N-substituted phenyl ring), 6.90 (d, J # 8.3 Hz; arom. H),
4.13, 4.07 (2t, J # 5.8 Hz each; 2 OCH2 groups), 2.60 (t, J #
7.7 Hz; a-CH2 group). 13C-NMR: d = 158.97 (d; HCLN),
151.59, 149.79, 149.15, 140.61, 130.01 (5s; 5 arom. C), 129.08,
124.28, 120.75, 112.38, 111.00 (5d; 2,1,2,1 and 1 arom. CH,
respectively), 68.32, 68.30 (2t; 2 OCH2 groups), 35.50 (t; a-CH2
group). C39H37F26NO2 (1045.7): calcd. C 44.79, H 3.56, N
1.34; found C 45.00, H 3.79, N 1.18.
Compounds 6b. Yield: 0.28 g (27%) of yellow crystals.
1H-NMR d = 7.76 (s; 2 HCLN), 7.23, 7.13 (2s, J # 7.1 Hz
each; 8 arom. H of the N-substituted phenyl rings), 6.84, 6.80
(2s; 4 arom. H of the Pd-substituted phenyl rings), 3.98
(s, broad, 2 OCH2 groups), 3.89 (t, J # 6.4 Hz; 2 OCH2
groups), 2.58 (t, J # 7.8 Hz; 2 a-CH2 groups). 13C-NMR: d =
172.93 (d; 2HCLN), 150.43, 148.97, 146.58, 146.24, 142.34,
137.56 (6s; 12 arom. C), 128.41, 123.09, 117.27, 113.83 (4d; 4,
4, 2 and 2 arom. CH, respectively), 69.67, 68.36 (2t; 4 OCH2
groups), 35.60 (t; 2 a-CH2 groups). C78H88Cl2F36N2O4Pd2
(2085.3): calcd. C 44.93, H 4.25, N 1.34; found C 44.74, H 4.43,
N 1.30.
Synthesis of the palladium complexes 5b, c and 6a–c
A suspension of 1 mmol of the imine compounds 3b, c or 4a–c
and 1 mmol of bis(benzonitrile)-palladium(II) chloride in 20 ml
of dry ethanol and in 10 ml of dry dichloromethane was
stirred under Ar atmosphere for 4 days at room temperature.
The resulting yellow solid was filtered off, suspended in
chloroform and the suspension filtered through a short Celite
column. The solvent was evaporated under reduced pressure.
The compounds 5b, c and 6a–c were purified by several
crystallizations from methanol–dichloromethane.
Compounds 6c. Yield: 0.43 g (36%) of yellow crystals.
1H-NMR d = 7.77 (s; 2 HCLN), 7.23, 7.13 (2d, J # 7.1 Hz
each; 8 arom. H of the N-substituted phenyl rings), 6.85,
6.81 (2s; 4 arom. H of the Pd-substituted phenyl rings), 4.01
(s, broad, 2 OCH2 groups), 3.92 (t, J # 5.5 Hz; 2 OCH2
groups), 2.58 (t, J # 7.8 Hz; 2 a-CH2 groups). 13C-NMR: d =
172.76 (d; 2HCLN), 150.10, 149.05, 146.42, 146.05, 142.40,
137.76 (6s; 12 arom. C), 128.37, 123.02, 117.29, 113.84 (4d; 4,
4, 2 and 2 arom. CH, respectively), 69.32, 67.98 (2t; 4 OCH2
groups), 35.65 (t; 2 a-CH2 groups). C78H72Cl2F52N2O4Pd2
(2373.1): calcd. C 39.48, H 3.06, N 1.18; found C 39.36, H 2.64,
N 0.98.
The transition temperatures of the palladium compounds
5b, c and 6a–c are given in Table 1.
Compounds 5b. Yield: 0.45 g (33%) of yellow crystals.
1H-NMR d = 7.99 (s; 2 HCLN), 7.24–7.12 (m; 8 arom. H of
the N-substituted phenyl rings), 6.55 (s, broad; 2 arom. H of
the Pd-substituted phenyl rings), 4.08, 3.84 (2t, J # 6.5 Hz
each; 4 OCH2 groups), 3.95 (s, broad, 2 OCH2 groups), 2.57
(t, J # 7.8 Hz; 2 a-CH2 groups). 13C-NMR: d = 170.39 (d;
2 HCLN), 154.84, 151.73, 149.85, 146.86, 142.23, 137.54,
132.21 (7s; 14 arom. C), 128.33, 123.15, 112.97 (3d; 4, 4 and
2 arom. CH, respectively), 74.42, 73.32, 68.37 (3t; 6 OCH2
groups), 35.62 (t; 2 a-CH2 groups). C98H110Cl2F54N2O6Pd2
(2721.7): calcd. C 43.25, H 4.07, N 1.03; found C 43.29, H 4.06,
N 0.97.
Acknowledgements
B. Bilgin-Eran is grateful to the Alexander von Humboldt
Foundation for a research fellowship at Universita¨t Halle-
Wittenberg, Halle, Germany.
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