Effect of alkoxy chains on the mesomorphic properties of (p-alkoxy)tetrafluoroarylgold(I) isocyanide complexes

Article abstract of DOI:10.1016/S0020-1693(02)01565-7

Rod-like gold(I) complexes [Au(C₆F₄OC _mH_2m+1)(C≡NC₆H₄O(O)CC ₆H₄OC_nH_2n+1)] [m=4, 8; n=4, 6, 8, 10] have been prepared and their liquid crystal behavior studied. All the tetrafluorophenylgold(I) derivatives described are liquid crystals and their thermal stability is high, even in the isotropic state. The variation in thermal properties of tetrafluorophenylgold(I) complexes is very regular. When a short alkoxy chain is placed in the tetrafluorophenyl group (m=4), both smectic A and nematic phases are observed for shorter alkoxy substituents in the isocyanide ligand (n=4, 6). For longer chain-lengths (n=8, 10), only smectic A phases are observed. When the alkoxy substituent in the tetrafluorophenyl group is longer (m=8), both SmA and SmC phases are obtained, irrespective of the chain-lengths of the isocyanide ligand.

Full text of DOI:10.1016/S0020-1693(02)01565-7

Inorganica Chimica Acta 350 (2003) 366ꢂ370
/
www.elsevier.com/locate/ica
Effect of alkoxy chains on the mesomorphic properties of
(p-alkoxy)tetrafluoroarylgold(I) isocyanide complexes
Silverio Coco, Ce´sar Ferna´ndez-Mayordomo, Santiago Falaga´n, Pablo Espinet *
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain
Received 4 July 2002; accepted 16 September 2002
This paper is dedicated to Prof. Pierre Braunstein, inspired chemist, perfect gentleman, kind boss and good friend.
Abstract
Rod-like gold(I) complexes [Au(C6F4OCmH2mꢀ1)(Cꢀ
prepared and their liquid crystal behavior studied. All the tetrafluorophenylgold(I) derivatives described are liquid crystals and their
/
NC6H4O(O)CC6H4OCnH2nꢀ1)] [mꢁ
/
4, 8; nꢁ4, 6, 8, 10] have been
/
thermal stability is high, even in the isotropic state. The variation in thermal properties of tetrafluorophenylgold(I) complexes is very
regular. When a short alkoxy chain is placed in the tetrafluorophenyl group (mꢁ
observed for shorter alkoxy substituents in the isocyanide ligand (nꢁ4, 6). For longer chain-lengths (nꢁ
phases are observed. When the alkoxy substituent in the tetrafluorophenyl group is longer (mꢁ8), both SmA and SmC phases are
/
4), both smectic A and nematic phases are
/
/8, 10), only smectic A
/
obtained, irrespective of the chain-lengths of the isocyanide ligand.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Liquid crystals; Smectic; Nematic; Fluorinated; Isocyanide; Gold
1. Introduction
[31], Pd(II), Pt(II)[30,34ꢂ37] and Fe(0) [38]. As part of
/
our systematic studies on the effect of structural
modifications on the liquid crystal behavior in meso-
morphic metal isocyanide complexes, we have described
several mesomorphic thermally stable perhalophenyl-
Liquid crystals with highly fluorinated aromatic
substructures have attracted much attention due to the
fact that many of them display interesting physical
properties, such as high clearing temperatures, high
gold(I) isocyanide complexes [AuR(Cꢀ
/
NC6H4C6H4-
4,
dielectric anisotropy or low rotational viscosity [1ꢂ3].
/
For this reason fluorinated liquid crystals are commonly
used as components of liquid crystals mixtures for
electro-optic displays.
The influence of fluorination in thermotropic liquid
crystals is quite well understood for organic molecules
OCnH2nꢀ1-p)] (RꢁC6F5, C6F4Br-o, C6F4Br-p; nꢁ
/
/
6, 8, 10, 12). They combine isocyanide ligands and
fluorinated regions, and show a rich mesopolimorphism
when the chain-length is varied. Their transition tem-
peratures change regularly with the kind of perhalophe-
nyl group [14].
We now look at the effect of introducing an alkoxy
chain in the pentafluorophenyl ligand using a 4-alkox-
ytetrafluorophenyl group, which involves doubling the
number of chains per molecule respect to the mesogenic
[1,4ꢂ
thermotropic transition metal based materials already
known [9ꢂ15], only a limited number of mesogenic
metal complexes (so-called metallomesogens) with
fluorinated ligands has been reported [16ꢂ23].
Isocyanide metal complexes have provided metallo-
mesogens of Au(I) [15,21,22,24ꢂ33], Ag(I) [32], Cu(I)
/
8]. However, in spite of the numerous examples of
/
/
complexes [AuR(Cꢀ
/
NC6H4C6H4OCnH2nꢀ1-p)] (Rꢁ
/
/
C6F5, C6F4Br-o, C6F4Br-p). Here, we report the syn-
thesis and liquid crystalline behavior of a very stable
family of tetrafluoroaryl-gold(I) isocyanide complexes
* Corresponding author. Tel.: ꢀ
3013.
E-mail address: espinet@qi.uva.es (P. Espinet).
/
34-98342 3231; fax: ꢀ34-98342
/
of the type [Au(C6F4OCmH2mꢀ1)(Cꢀ
/
NC6H4O(O)C-
C6H4OCnH2nꢀ1)] [mꢁ4, 8; nꢁ4, 6, 8, 10].
/
/
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(02)01565-7

S. Coco et al. / Inorganica Chimica Acta 350 (2003) 366ꢂ
/370
367
2. Experimental
at ꢃ
50 8C, solid [AuCl(tht)] (0.078 g, 0.250 mmol) was
added at ꢃ78 8C and the reaction mixture was slowly
brought to room temperature (3 h). Then, a few drops of
water were added and the solution was filtered in air
through anhydrous MgSO4. To the solution obtained,
/
78 8C, under nitrogen. After stirring for 1 h at ꢃ
/
Combustion analyses were made with a Perkin-Elmer
2400 microanalyzer. IR spectra (cmꢃ1) were recorded
on a Perkin-Elmer FT 1720X instrument and H and
/
1
19F NMR spectra on Bruker AC 300 or ARX 300
instruments in CDCl3. Microscopy studies were carried
out using a Leitz microscope provided with a hot stage
and polarizers at a heating rate of approximately
10 8C minꢃ1. For differential scanning calorimetry
(DSC) a Perkin-Elmer DSC7 instrument was used,
which was calibrated with water and indium; the
scanning rate was 10 8C minꢃ1, the samples were sealed
in aluminum capsules in the air, and the holder atmo-
sphere was dry nitrogen.
Cꢀ/NC6H4O(O)CC6H4OC4H9 (0.074 g, 0.250 mmol)
was added and after stirring for 15 min, the solvent
was removed on a rotary evaporator and the white solid
obtained was recrystallized from dichloromethane/hex-
ane at ꢃ
/
15 8C (69% yield). 1H NMR (CDCl3): d1 7.63,
d2 7.38, AA?XX? spin system J3,4ꢀ5
/
J
3,4?ꢁ
/
8.9 Hz), d3
3,4?ꢁ8.9
CH2), 4.06 (t, Jꢁ
0.88 (m, 14H, alkyl
118.26 (Fortho), d2
157.40 (Fmeta), AA?XX? spin system (3J1,2ꢀ5
1,2?ꢁ
1,2?ꢁ47.9
N)/cmꢃ1: (CH2Cl2) 2217, (KBr) 2215.
3
8.12, d4 7.00, AA?XX? spin system J3,4ꢀ5
Hz), 4.15 (t, Jꢁ6.7 Hz, 2H, C6F4ꢁOꢁ
6.5 Hz, 2H, C6H4ꢁOꢁCH2) 1.86ꢂ
chain). 19F NMR (CDCl3): d1
/
J
/
3
/
/
/
/
/
/
/
Literature methods were used to prepare [Cꢀ
NC6H4O(O)CC6H4OCnH2nꢀ1-p] [35] and [AuCl(tht)]
(thtꢁtetrahydrothiophene) [39].
/
ꢃ
/
ꢃ
/
/
J
/
/
3
18.0 Hz), 4J1,1?ꢀ4
Hz). IR n(Cꢀ
/
J
2,2?ꢁ
/
14.9 Hz), J1,2ꢀ5
/
J
/
Only example procedures are described, as the syn-
theses were similar for the rest of the compounds.
Yields, IR, and analytical data are given for all the
gold complexes.
/
Anal. Calc. for C28H26AuF4NO4: C, 47.13; H, 3.67; N,
1.96. Found: C, 46.87; H, 3.41; N, 1.96.
Yields, IR and analytical data for the rest of
complexes are as follows:
2.1. Preparation of 1-octyloxy-2,3,5,6-tetrafluorobenzene
mꢁ
/
4, nꢁ
/
6: Yield: 57%. IR n(Cꢀ
/
N)/cmꢃ1:(CH2Cl2)
2217, (KBr) 2216. Anal. Calc. for C30H30AuF4NO4: C,
48.58; H, 4.05; N, 1.89. Found: C, 48.59; H, 4.00; N,
1.65.
Anhydrous K2CO3 (0.787 g, 5.69 mmol) was added to
a solution of 2,3,5,6-tetrafluorophenol (0.700 ml, 3.79
mmol) and 4.17 mmol of bromooctane in 80 ml of dry
acetone. The resulting suspension was refluxed under N2
for 48 h and then allowed to cool to room temperature.
The reaction mixture was poured into 200 ml of H2O
and the solution was acidified with diluted HCl. CH2Cl2
was added to this mixture and the organic layer was
separated, dried over MgSO4, and filtered. The solvent
was evaporated on a rotary evaporator. The residue was
chromatographed (silica gel, hexane as eluent) and the
solvent was evaporated to obtain the product as a
mꢁ
/
4, nꢁ
/
8: Yield: 51%. IR n(Cꢀ
/
N)/cmꢃ1: (CH2Cl2)
2217, (KBr) 2216. Anal. Calc. for C32H34AuF4NO4: C,
49.94; H, 4.42; N, 1.82. Found: C, 49.78; H, 4.27; N,
2.02.
mꢁ
/
4, nꢁ
/
10: Yield: 60%. IR n(Cꢀ
/
N)/cmꢃ1
:
(CH2Cl2) 2217, (KBr) 2215. Anal. Calc. for
C34H38AuF4NO4: C, 51.19; H, 4.77; N, 1.76. Found:
C, 50.96; H, 4.89; N, 1.85.
mꢁ
/
8, nꢁ
/
4: Yield: 58%. IR n(Cꢀ
/
N)/cmꢃ1: (CH2Cl2)
1
2217, (KBr) 2219. Anal. Calc. for C32H34AuF4NO4: C,
49.94; H, 4.42; N, 1.82. Found: C, 50.14; H, 4.37; N,
1.89.
colorless liquid (95%). H NMR (CDCl3): d 6.74 (m,
HC6F4), d 4.21 (t, Jꢁ
15 H, alkyl chain). 19F NMR (CDCl3): d1
(Fortho-H), d2 ꢃ157.61 (Fmeta-H), AA?XX? spin system
(3J1,2ꢀ5 4J1,1?ꢀ4
1,2?ꢁ5.1 Hz, 2,2?ꢁ16.1 Hz,
3J1,2ꢃ5
1,2?ꢁ21.0 Hz).
/
0.9 Hz, Oꢁ
/
CH2), 1.86ꢂ
/
0.88 (m,
ꢃ
/
140.76
mꢁ
/
8, nꢁ
/
6: Yield: 50%. IR n(Cꢀ
/
N)/cmꢃ1: (CH2Cl2)
/
2217, (KBr) 2218. Anal. Calc. for C34H38AuF4NO4: C,
51.19; H, 4.77; N, 1.76. Found: C, 50.95; H, 4.51; N,
1.80.
/
J
/
/
J
/
/
J
/
The butoxy derivative was prepared similarly using
N,N-dimetylformamide as solvent and refluxing the
suspension for 1 h.
mꢁ
/
8, nꢁ
/
8: Yield: 48%. IR n(Cꢀ
/
N)/cmꢃ1: (CH2Cl2)
2217, (KBr) 2217. Anal. Calc. for C36H42AuF4NO4: C,
52.37; H, 5.13; N, 1.70. Found: C, 52.04; H, 4.72; N,
1.84.
2.2. Preparation of [Au(C6F4OCmH2mꢀ1)(Cꢀ
/
mꢁ
/
8, nꢁ
/
10: Yield: 55%. IR n(Cꢀ
/
N)/cmꢃ1
:
NC6H4O(O)CC6H4OCnH2nꢀ1)]
(CH2Cl2) 2217, (KBr) 2218. Anal. Calc. for
C38H46AuF4NO4: C, 53.46; H, 5.39; N, 1.64. Found:
C, 53.26; H, 5.28; N, 1.84.
All these compounds were synthesized using a similar
method. The preparation for mꢁ
example.
mꢁ4, nꢁ4: To a solution of HC6F4OC4H9 (0.055 g,
/
4, nꢁ4 is given as an
/
mꢁ
/
8, nꢁ
/
12: Yield: 56%. IR n(Cꢀ
/
N)/cmꢃ1
:
(CH2Cl2) 2217, (KBr) 2218. Anal. Calc. for
C40H50AuF4NO4: C, 54.48; H, 5.67; N, 1.59. Found:
C, 54.23; H, 5.51; N, 1.54.
/
/
0.25 mmol) in 25 ml of dry diethyl ether was added a
solution of LiBu 1.6 M in hexane (0.25 ml, 0.165 mmol)

368
S. Coco et al. / Inorganica Chimica Acta 350 (2003) 366ꢂ370
/
3. Results
The 19F NMR spectra of these complexes show two
somewhat distorted ‘doublets’ flanked by two pseudo-
triplets corresponding to an AA?XX? spin system with
3.1. Synthesis and characterization
JAA?
and ꢃ
F(meta) to gold respectively, with apparent coupling
constants (NꢁJAX AX?) in the range 18ꢂ19.7 Hz.
:
/
J
XX?. The signals appear at approximately ꢃ
/
118
/
157 ppm (ref. CFCl3) assigned to F(ortho) and
The alkoxytetrafluorobenzenes, which are starting
materials for the preparation of tetrafluorophenyl-
gold(I) complexes, were obtained by alkylation of 4-
tetrafluorophenol with the corresponding alkylbromide.
The gold(I) isocyanide complexes were prepared as
described in the literature for similar fluorophenyl-
gold(I) isocyanide derivatives [33], as represented in
/
ꢀ
/
J
/
3.2. Mesogenic behavior
All the gold isocyanide compounds [Au(C6F4OCm-
2mꢀ1)(CꢀNC6H4O(O)CC6H4OCnH2nꢀ1)] [mꢁ4, 8;
nꢁ4, 6, 8, 10] are mesomorphic and their optical,
H
/
/
Scheme 1 (thtꢁ
2mꢀ1)(CꢀNC6H4O(O)CC6H4OCnH2nꢀ1)] [mꢁ
nꢁ4, 6, 8, 10] were obtained by arylation of [AuCl(tht)]
/
tetrahydrothiophene). [Au(C6F4OCm-
/
H
/
/4, 8;
thermal and thermodynamic data are summarized in
Table 1. The free 4-isocyanophenyl 4-alkoxybenzoates
display nematic (N) and/or smectic A (SmA) phases in
/
followed by ligand exchange with the appropriate
isocyanide.
The C, H, N analyses for the complexes, yields, and
relevant IR data are given in the experimental part. The
the range 61ꢂ88 8C [35]. The variation in thermal
/
properties of the tetrafluorophenylgold(I) complexes is
IR spectra are all similar and show one n(Cꢀ
absorption for the isocyanide group at higher wavenum-
bers (:
90 cmꢃ1) than for the free isocyanide, as
/
N)
Table 1
Optical, thermal and thermodynamic data of the complexes
[Au(C6F4OCm H2mꢀ1-p)(CN-C6H4O(O)CC6H4OCn H2nꢀ1-p)]
/
reported for other gold(I) isocyanide compounds [22].
The 1H NMR spectra of the gold(I) isocyanide
complexes prepared are all very similar, showing at
300 MHz respectively four somewhat distorted ‘doub-
lets’ (a deceptively simple pattern arising from the
strictly speaking AA?XX? spin systems) for the two
phenyl groups present in the molecule. In addition, two
virtual triplets are observed at approximately 4.1 and 3.9
ppm corresponding to the first methylene group of
the C6F4OCmH2mꢀ1 and C6H4O(O)CC6H4OCnH2nꢀ1
groups, respectively. The remaining chain hydrogens
m
n
Transitiona
SmA
Temperatureb (8C)
DHb (kJ molꢃ1
)
4
4
Cꢂ
SmAꢂ
Nꢂ
CꢂSmA
SmAꢂ
Nꢂ
CꢂC?
CꢂSmA
SmAꢂ
10 CꢂSmA
SmAꢂ
CꢂC?
C?ꢂSmC
SmCꢂSmA
SmAꢂ
CꢂC?
C?ꢂCƒ
CƒꢂSmC
SmCꢂSmA
SmAꢂ
CꢂC?
C?ꢂSmC
SmCꢂSmA
SmAꢂ
10 CꢂC?
C?ꢂCƒ
CƒꢂSmC
SmCꢂSmA
SmAꢂ
12 CꢂC?
C?ꢂSmC
SmCꢂSmA
SmAꢂ
/
147.1
213.5
235.9
141.8
195.6
207.0
79.5
24.3
0.4
/N
/I
1.0
4
4
6
8
/
6.3
0.2
/N
/I
0.3
/
5.0
/
124.5
221.6
117.1
207.3
48.3
21.2
4.6
/I
4
8
/
23.0
4.7
/I
appear unresolved in the range 0.8ꢂ1.8 ppm.
/
4
6
/
8.1
22.0
/
110.3
170c
/
/I
190.7
48.45
95.39
112.9
170c
3.5
0.4
8
/
/
0.6
/
19.1
/
/I
210.6
76.6
6.2
0.8
8
8
8
/
/
110.4
175c
18.7
/
/I
200.2
55.7
6.3
9.2
/
/
85.6
4.8
/
110.6
176.0
205.6
85.3
20.2
0.2
/
/I
6.1
8
/
7.9
/
101.8
180.3
203.9
18.9
0.2
/
/I
6.3
a
C, crystal; N, nematic; Sm, smectic; I, isotropic liquid.
Data referred to the second DSC cycle starting from the crystal.
b
Temperature data as peak onset.
c
Microscopic data.
Scheme 1.

S. Coco et al. / Inorganica Chimica Acta 350 (2003) 366ꢂ
/370
369
quite regular. They show mesophases which are as fluid
as those of free isocyanides. For the butoxytetrafluor-
ophenyl derivatives, both smectic A and nematic phases
are observed for shorter alkoxy substituents in the
isocyanide ligand (nꢁ
is obtained for longer chain-lengths (nꢁ
the alkoxy substituent in the tetrafluorophenyl group is
longer (mꢁ8) both SmA and SmC phases are obtained,
/4, 6), and only a smectic A phase
/8, 10). When
/
irrespective of the chain-lengths of the isocyanide ligand.
The nematic phases display the schlieren texture
showing singularities with two and four associated
brushes (Fig. 1). The SmA mesophases present the
typical mielinic and homeotropic textures reorganizing
to the fan-shaped texture at temperatures close to the
clearing point, and the focal-conic fan texture on
cooling from the nematic or isotropic phases (Fig. 2).
The SmC mesophases show the typical schlieren texture,
which does not flash when subjected to mechanical
stress, and the broken focal-conic fan texture on cooling
from the a SmA phase with a focal-conic fan texture
(Fig. 3) [40,41]. Some of the compounds show crystal-to-
crystal transitions before melting.
Fig. 2. Polarized optical microscopic texture (ꢄ
/
100) observed for
NC6H4O(O)CC6H4OC10H21)]. The picture
[Au(C6F4OC8H17)(Cꢀ
/
shows the fan-shaped texture of the SmA phase and a homeotropic
region at 180 8C, on cooling from the isotropic liquid.
The influence of the alkoxy chain length on the
transition temperatures is quite regular and can be
summarized as follows. For mꢁ 4, the melting points
/
decrease smoothly as n increases. The same behavior is
observed for the nematic-isotropic liquid and the SmA-
isotropic liquid transitions. The increase of the chain-
lengths in the isocyanide group produces a gradual
decrease of the range of the nematic phase and an
increase of the range of the SmA phase. In contrast, for
mꢁ8 the melting and clearing temperatures remain
/
roughly invariant with the length of the alkoxy sub-
stituent in the isocyanide ligand. Moreover, at constant
n, the increase of the chain-length in the tetrafluoro-
Fig. 3. Polarized optical microscopic texture (ꢄ
/
100) observed for
[Au(C6F4OC8H17)(CꢀNC6H4O(O)CC6H4OC10H21)] at 112 8C. The
/
picture shows the same area of the previous picture. It displays the
broken fan-shape texture of the SmC phase formed on cooling from
the fan-shaped focal-conic area of the SmA phase, and a region with
schlieren texture of the SmC phase formed on cooling the homeotropic
region of the SmA phase.
phenyl ligand, from mꢁ
/
4 to mꢁ8, produces an
/
enhancement of the range of smectic mesophase.
It is interesting to note that the SmCꢂ
is detected by DSC only for longest alkoxy chains,
suggesting that as the chains get longer the SmCꢂSmA
/
SmA transition
/
transition changes from being second-order to weakly
first-order.
This trend is reminiscent of that found in [Au(Cꢀ
/
CC6H4CmH2mꢀ1)(CꢀNC6H4OCnH2nꢀ1)] complexes,
/
where the variation in length of the alkynyl chain
induces very noticeable effects on the melting points,
whereas changing the length of the isocyanide for a
given alkynyl, produces little variation in the melting
points [26].
The importance of the distribution of polar and non-
polar structural units in calamitic mesogens for the
formation of nematic and smectic phases is well-known.
Besides the molecular geometry and special conforma-
Fig. 1. Polarized optical microscopic texture (ꢄ
/
100) observed for
[Au(C6F4OC4H9)(CꢀNC6H4O(O)CC6H4OC4H9)]. The picture shows
/
the schlieren texture of the N phase, at 215 8C on cooling from the
isotropic liquid.

370
S. Coco et al. / Inorganica Chimica Acta 350 (2003) 366ꢂ370
/
[7] M.A. Osman, Mol. Cryst. Liq. Cryst. 128 (1985) 45.
[8] D. Demus, J. Goodby, G.W. Gray, H.W. Spiess, D.V. Vill (Eds.),
Handbook of Liquid Crystals, Wiley-VCH, Weinheim, 1998.
[9] A.M. Giroud-Godquin, P.M. Maitlis, Angew. Chem., Int. Ed.
Engl. 30 (1991) 375.
tional effects, micro-segregation also contributes to
induction of liquid crystal behavior. In general, micro-
segregation is favored in molecules with a well-defined
intramolecular contrast, i.e. in complexes with distinct
polar/rigid and less polar/flexible segments [42]. In these
cases smectic mesophases are stabilized.
[10] P. Espinet, M.A. Esteruelas, L.A. Oro, J.L. Serrano, E. Sola,
Coord. Chem. Rev. 117 (1992) 215.
1
[11] D.W. Bruce, in: D.W. Bruce, D. O’Hare (Eds.), Inorganic
Materials, second ed. (Chapter 8), Wiley, Chichester, 1996.
[12] S.A. Hudson, P.M. Maitlis, Chem. Rev. 93 (1993) 861.
[13] J.L. Serrano (Ed.), Metallomesogens, VCH, Weinheim, 1996.
[14] B. Donnio, D.W. Bruce, Struct. Bonding 95 (Liquid Crystals II)
(1999) 193.
According to the H NMR data above discussed, a
deshielding is observed for the first methylene group of
the C6F4OCmH2mꢀ1 ligand compared to that of the
isocyanide moiety. This supports that the electronega-
tivity of tetrafluorophenyl group is higher than that of
isocyanide group. Thus, in our gold complexes the
segregation of the aromatic and alkoxy chain blocks
must be very marked, and specially favored between the
tetrafluorophenyl group, and its alkoxy chain. More-
over, this segregation should become more efficient on
elongation of the terminal alkoxy chain. Thus, when the
chain-length, especially in the tetrafluorophenyl group,
is increased smectic phases are stabilized, as observed.
In conclusion, stable tetrafluorophenylgold(I) isocya-
nide complexes show a rich mesopolimorphism, which
can be easily modulated by variation of the terminal
alkyl chain-length of both the isocyanide and the
tetrafluorophenyl groups. Moreover, it is interesting to
note that the mesophases obtained are more fluid than
those displayed generally by metallomesogens. Finally,
changes in the alkoxy chain on the tetrafluorophenyl
group are more influencing on the thermal properties
than changes in the chain placed on the isocyanide
ligand.
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We thank the Comisio´n Interministerial de Ciencia y
Tecnolog´ıa (Project MAT99-0971), Direccio´n General
de Investigacio´n (Project MAT2002-00562) and the
Junta de Castilla y Leo´n (Projects VA15/00B and
VA050/02) for financial support.
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