Synthesis, computational modelling and liquid crystalline properties of some [3]ferrocenophane-containing Schiff's bases and β-aminovinylketone: Molecular geometry-phase behaviour relationship

Article abstract of DOI:10.1016/j.jorganchem.2007.09.010

Rotationally fixed [3]ferrocenophane extends the variety of possible molecular geometries in its derivatives in comparison with unbridged ferrocenes. In this respect molecular geometry-liquid crystalline properties relationship studies in [3]ferrocenophane mesogens are of considerable interest. Different positional isomers of mono- and di-substituted [3]ferrocenophanes which are obtained by incorporating one or two promesogenic building blocks into the cyclopentadienyl rings are reported in this article. A series of mono-substituted [3]ferrocenophane-containing Schiff's bases was synthesized by condensing isomeric p-aminophenyl [3]ferrocenophanes with appropriate aldehydes. Isomers of di-substituted [3]ferrocenophane amines gave rise to a series of azomethines with two promesogenic substituents in the cyclopentadienyl rings. Besides, a β-enaminoketone was prepared from 3-(p-aminophenyl)[3]ferrocenophane. Nematic and smectic mesophases were observed in the synthesized compounds under a polarizing optical microscope. The [3]ferrocenophane-containing β-enaminoketone showed complex mesomorphic behaviour connected with occurrence of the keto-enamine and imino-enol tautomeric equilibrium in this compound. On the base of computational models obtained by semi-empirical quantum chemistry calculations the molecular geometry-phase behaviour relationships were examined. It was demonstrated that mesomorphism of [3]ferocenophane azomethines depends on the spatial orientation of the substituents with respect to the propanediyl bridge in a case of mono-, and as well as to each other in a case of di-substituted derivatives.

Full text of DOI:10.1016/j.jorganchem.2007.09.010

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5571–5582
www.elsevier.com/locate/jorganchem
Synthesis, computational modelling and liquid crystalline properties
of some [3]ferrocenophane-containing Schiff’s bases and
b-aminovinylketone: Molecular geometry–phase behaviour relationship
a,
a
b,c
Oleg N. Kadkin *, Haksoo Han , Yuri G. Galyametdinov
a
Department of Chemical Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-749, South Korea
Department of Physical and Colloid Chemistry, Kazan State Technological University, 68 K. Marks Street, 420015 Kazan, Russia
b
c
Kazan Institute of Physics and Technology, Russian Academy of Sciences, 16/7 Sibirskiy Trakt Street, 420029 Kazan, Russia
Received 22 June 2007; received in revised form 30 August 2007; accepted 4 September 2007
Available online 21 September 2007
Abstract
Rotationally fixed [3]ferrocenophane extends the variety of possible molecular geometries in its derivatives in comparison with
unbridged ferrocenes. In this respect molecular geometry–liquid crystalline properties relationship studies in [3]ferrocenophane mesogens
are of considerable interest. Different positional isomers of mono- and di-substituted [3]ferrocenophanes which are obtained by incor-
porating one or two promesogenic building blocks into the cyclopentadienyl rings are reported in this article. A series of mono-substi-
tuted [3]ferrocenophane-containing Schiff’s bases was synthesized by condensing isomeric p-aminophenyl [3]ferrocenophanes with
appropriate aldehydes. Isomers of di-substituted [3]ferrocenophane amines gave rise to a series of azomethines with two promesogenic
substituents in the cyclopentadienyl rings. Besides, a b-enaminoketone was prepared from 3-(p-aminophenyl)[3]ferrocenophane. Nematic
and smectic mesophases were observed in the synthesized compounds under a polarizing optical microscope. The [3]ferrocenophane-con-
taining b-enaminoketone showed complex mesomorphic behaviour connected with occurrence of the keto-enamine and imino-enol tau-
tomeric equilibrium in this compound. On the base of computational models obtained by semi-empirical quantum chemistry calculations
the molecular geometry–phase behaviour relationships were examined. It was demonstrated that mesomorphism of [3]ferocenophane
azomethines depends on the spatial orientation of the substituents with respect to the propanediyl bridge in a case of mono-, and as well
as to each other in a case of di-substituted derivatives.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Ferrocenophane; Liquid crystals; Metallomesogens; Azomethine; b-Aminovinylketone
1. Introduction
Thus, unbridged ferrocenomesogens are widely
explored. The synthesized examples of ferrocene-contain-
ing liquid crystals can be classified into three main groups:
(i) mono-substituted; (ii) homoannularly di-substituted;
(iii) heteroannularly di-substituted (see Fig. 1). Because of
the rotational freedom of the cyclopentadienyl rings
around the normal axis both S-shaped and U-shaped
conformations are possible in a liquid crystalline state for
heteroannularly substituted ferrocenes.
Ferrocene containing liquid crystals attract continuous
interest of many researchers in the world. Imrie et al. and
Deschenaux et al. have summarized in reviews results
obtained in this field to the end of last century [1]. Research
efforts on syntheses, structural characterization and prop-
erties of new liquid crystalline ferrocene derivatives still
persist in recent years [2].
There is another less investigated type of ferrocenomes-
ogens such as derivatives of the bridged ferrocenes. For
example, the reported liquid crystalline [3]ferrocenophane
compound showed broader mesophase in comparison with
*
Corresponding author.Fax: +82 2 312 6401.
E-mail address: onk@yonsei.ac.kr (O.N. Kadkin).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.09.010

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O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
Fe
Fe
ii)
i)
Fe
Fe
iii)
Fig. 1. Molecular shapes occurring in the liquid crystalline ferrocene derivatives.
its unbridged analogue [3]. Hence, incorporation of a fer-
rocenophane unit into the liquid crystalline structures can
bring certain advantages over its unbridged ferrocene
counterparts. Furthermore, the possibility of various posi-
tional isomers in derivatives of rotationally fixed ferroceno-
phanes results in wide diversity of the molecular geometries
that can be realized in the liquid crystalline structures on
their base. In this respect molecular geometry–liquid crys-
talline properties relationship studies in [3]ferrocenophane
mesogens are of considerable interest.
Recently, we have reported inclusion of the aryl substit-
uents into a [3]ferrocenophane moiety [4], which gave rise
to isolation of several p-nitrophenylated isomers. Further
efforts to obtain mesogenic materials from these arylated
products gave rise to a series of new [3]ferrocenophane-
containing liquid crystals which are described in the present
article. Some of these synthesized compounds are designed
specially for coordinating transition metal ions and obtain-
ing heteronuclear metallomesogenic systems, which are of
special interest due to the potential revelation of the unique
magnetic and optical properties [5].
rocenophanes with stannous(II) chloride (see Scheme 1).
The imines 5–8 were obtained by Schiff’s condensation of
amines 1–4 with corresponding aldehydes 10 and 19 (see
Schemes 2 and 3).
All of the synthesized alkoxylated products were pre-
pared using the Williamson reaction: 4-dodecyloxybenzal-
dehyde 10a and 2-hydroxy-4-dodecyloxybenzaldehyde 10b
were prepared by etherification correspondingly of
4-hydroxybenzaldehyde 9a and 2,4-dihydroxybenzalde-
hyde 9b with dodecyl bromide and potassium carbonate
in acetone; similar procedure was used to prepare 4-dode-
cyloxyacetophenone 12 from 4-hydroxyacetophenon 11;
4-dodecyloxybenzoic acid 17 was obtained via hydrolysis
of ethyl-(4-dodecyloxy)benzoate 16, where the latter was
prepared by an etherification reaction between ethyl-
(4-hydroxy)benzoate 15 and 1-bromododecane. An esterifi-
cation reaction between 4-hydroxybenzaldehyde 9a and
4-dodecyloxybenzoyl chloride 18 afforded 4-(40-dod-
ecyloxybenzoyloxy)benzaldehyde 19a. In the same condi-
tions 2,4-dihydroxybenzaldehyde 9b reacts yielding
2-hydroxy-4-(40-dodecyloxybenzoyloxy)benzaldehyde 19b.
Using a reaction of 4-dodecyloxybenzoylacetaldehyde
sodium salt 13 with hydrochloride of 3-(40-aminophe-
nyl)[3]ferrocenophane 1, b-aminovinylketone 14 was syn-
thesized. Mass-spectroscopic, IR and 1H NMR data of
the synthesized compounds are in a full agreement with
the proposed structures. Noticeably, compounds 5b, 5d
and 14 are able to form complexes with various transition
metals due to inclusion of the appropriate coordinating
groups into their molecules.
2. Results and discussion
2.1. Syntheses and spectral properties
The ferrocenophane-containing amines 1–4 were
obtained by reduction of the respective p-nitrophenyl[3]fer-
NH2
NH2
The illustrated configurations of the amines 1–4 are
based on the X-ray structural studies of their nitro-precur-
sors [4]. The propylidene bridge of [3]ferrocenophane
appears as three groups of signals in the areas of
Fe
Fe
2
1
1
1.85–2.00, 2.00–2.10 and 2.30–2.45 ppm in H NMR spec-
trum of the amine 2, while in the amine 1 all relevant
signals appear in the region of 1.85–2.05 ppm. This con-
forms to a less symmetric structure of the amine 2 in com-
parison with the amine 1 and consequently more varied
distances between a benzene mojety and different protons
of an alkylidene bridge. It is remarkable that in a 1H
NMR spectrum of the amine 3 two protons assigned to
the diarylated cyclopentadiene ring appear as a singlet at
3.24 ppm. The chemical and magnetic equivalency of these
protons is a consequence of their equal surrounding in
NH2
NH2
Fe
Fe
NH2
NH2
4
3
Scheme 1. Structures of [3]ferrocenophane-containing amines 1–4.

O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
5573
N HC
R
N HC
R
X
Fe
Fe
5 a-d
6 a,b
a: R=OC12H25
b: R=OOC
a: X=H, R=OC12H25
b: X=OH, R=OC12H25
OC12H25
OOC
OC12H25
OC12H25
c: X=H, R=
OOC
d: X=OH, R=
N HC
R
N HC
R
Fe
Fe
N HC
R
N HC
7 a,b
R
8 a,b
a: R=OC12H25
OOC
a: R=OC12H25
OC12H25
b: R=
OOC
OC12H25
b: R=
Scheme 2. Structures of [3]ferrocenophane-containing Schiff’s bases 5–8.
respect to the aromatic substituents and other parts of the
[3]ferrocenophane fragment.
compiled in Table 2. Unexpectedly, optical textures charac-
teristic for the columnar nematic phase were observed in
the super-cooled samples of compound 5a (Fig. 2). These
experimental observations can be rationalized by assump-
tion that at these relatively low temperatures molecules of
compound 5a congregate in bundles due to plane-to-plane
interactions of ferrocenophane units with each other, and
with the other aromatic rings in rigid core as well. Though
the observed mesophase is thermodynamically unstable
(monotropic), as a matter of fact [3]ferrocenophane-con-
taining azomethine 5a is the first example of mono-substi-
tuted ferrocenes with two benzene rings showing liquid
crystalline properties as there was no reported examples
in the earlier literature [1,2]. The mono-substituted [3]fer-
rocenophane Schiff’s base 5b containing lateral hydroxyl
substituent in a rigid core is non-mesomorphic (see Table
2).
The enanthiotropic nematic mesophases were observed
under a polarizing optical microscope in 5c and 5d, where
the aromatic rigid core was extended by the third benzene
ring. It is remarkable that compound 6b which is isomeric
to 5c showed only the monotropic nematic phase in a
super-cooled sample (see Fig. 2 for optical textures). There
is only a slight difference between these isomers connected
with stereochemical position of the propylidene bridge
in the ferrocene core towards the aromatic substituent.
A ferrocene moiety is revealed in the UV spectra of all
the synthesized compounds (Table 1) by two intensive max-
ima owing to n–p* and p–p* electronic transitions in the
regions of 277–297 and 330–339 nm, and non-intensive
absorption at 430–450 nm assigned to d-d transitions of
the iron atom [6]. The azomethine chromophore appears
in the Schiff’s bases 5–8 and b-aminovinylketone 14 with
intensive maxima in the area of 380–390 nm which is
absent in the spectra of the amines 1 and 2. It is noticeable
fact that compounds 5b and 5d containing a hydroxyl in
the ortho-position to an azomethine group have an addi-
tional intensive maximum at ꢀ350 nm. This additional
band connected with the absorption of carbonyl groups
emerged as a consequence of the imino-enol–keto-enamine
tautomerism in these compounds (see Scheme 4) [7,8]. The
intramolecular hydrogen bond provides the necessary sta-
bility to the corresponding keto-enamine tautomers.
2.2. Liquid crystalline properties
Thermal behaviour of the synthesized compounds was
investigated under a polarizing optical microscope with a
heating stage. The transition temperatures and the related
mesophases identified by thermal optical microscopy are

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O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
i
ii
5 a,b;
6 a; 7 a; 8 a
OHC
OC12H25
OHC
OH
X
X
9 a,b
10 a,b
a: X=H
b: X=OH
-O
C
Na+
O
C
O
C
iii
iv
OH
OC12H25
OC12H25
H3C
OHC
H3C
13
11
12
v
C
O
OC12H25
N
H
Fe
14
HO
O
C
O
C
vi
vii
C
OC12H25
OH
OC12H25
O
C2H5O
C2H5O
17
18
16
15
viii
Cl
C
O
OC12H25
ix
OHC
O
C
O
x
X=H: 5 c, 6 b, 7 b, 8b;
X=OH: 5 d
a: X=H
OC12H25
b: X=OH
X
19 a,b
Scheme 3. Synthesis of the [3]ferrocenophane-containing Schiff’s bases and b-aminovinylketone. Reagents and conditions: (i, iii, vi) BrC12H25, K2CO3, in
acetone, reflux; (ii, x) relevant amines 1–4, EtOH, reflux; (iv) ethylformiate, Na, abs. benzene, reflux; (v) amine 1, equimolar HCl, EtOH, reflux; (vii) KOH,
water/ethanol, reflux; (viii) SOCl2, reflux; (ix) aldehyde 9a or 9b, pyridine/benzene, reflux.
Table 1
UV/Vis (CH2Cl2) data of the compounds 1, 2, 5a–d, 6a,b, 7b, 8a,b, and 14
Compound
k
max, nm (loge, l cmꢁ1 molꢁ1
)
1
2
288 (4.303)
285 (4.079)
292 (4.461)
286 (4.169)
279 (4.639)
277 (4.561)
293 (4.401)
277 (4.673)
276 (5.058)
297 (4.794)
278 (4.931)
286 (4.224)
330 (sh) (3.511)
–
330 (4.377)
326 (sh) (4.169)
338 (sh) (4.236)
330 (sh) (4.308)
332 (4.338)
329 (4.277)
333 (4.644)
–
–
–
–
–
447 (2.698)
440 (2.661)
a
5a
5b
5c
5d
6a
6b
7b
8a
8b
14
a
380 (sh) (4.136)
385 (sh) (4.022)
389 (sh) (3.909)
382 (sh) (3.643)
380 (sh) (3.968)
385 (sh) (3.845)
390 (sh) (4.228)
387 (sh) (4.356)
390 (sh) (4.165)
390 (4.499)
455 (sh) (3.507)
440 (sh) (3.500)
450 (sh) (3.483)
460 (3.722)
430 (sh) (3.293)
425 (sh) (3.355)
446 (sh) (3.820)
455 (sh) (3.886)
455 (3.918)
347 (4.220)
–
350 (4.404)
–
–
–
–
–
–
335 (4.716)
339 (4.520)
a
–
450 (sh) (3.983)
The absorption appears as inflexion and can not be defined.

O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
5575
H
N
nophane compound 5d has almost the same width as in
the related ferrocene-containing Schiff’s base (130–163 °C,
see Table 2, vs. 135–171 °C [9]). In general, addition of
the propylidene bridge to a ferrocene fragment in b-posi-
tion to the promesogenic substituent enhances liquid crys-
talline properties of mono-substituted ferrocenyl mesogens,
while the presence of the propylidene group in a-position
drastically reduces mesomorphism.
H
N
C
C
O H
O H
A
H
H
C
H
H
C C
C
H O
C C
N
N
H O
Homoannularly di-substituted [3]ferrocenophane deriv-
atives 7a and 7b did not reveal mesomorphism. Heteroan-
nularly di-substituted compound 8a exhibited the
enanthiotropic nematic mesophase in a short temperature
range. Analogous compound 8b with more extended sub-
stituents showed only the monotropic smectic mesophase
upon cooling from the isotropic liquid state. Optical tex-
ture was not defined clearly in this case, however the
observed mesophase can be ascribed to the smectic type
on account of its limited fluidity (see Table 2 for phase
behaviour, and Fig. 3 for the observed microscopic
textures).
In order to compare stereometrical appearance of the
isomeric pairs 5c–6b and 7b–8b their conformational mod-
els were obtained using HYPERCHEM-7 program for molecu-
lar simulation. Initial geometry optimizations of the
structures were accomplished by simple molecular mechan-
ics calculations using MM+ method with a steepest descent
calculation algorithm, and then the obtained configura-
tions were optimized further by Fletcher–Reeves algo-
rithm. Finally semi-empirical calculations were performed
on the obtained configurations using PM3 method with a
conjugate directions algorithm.
B
Scheme 4. The imino-enol–keto-enamine tautomeric equilibrium: A for
compounds 5b and 5c; B for compound 14.
Obviously, [3]ferrocenophane derivative 5c has more
extended geometry in comparison with the related 2-substi-
tuted isomer 6b. At the same time the cyclopentadien ring
of the [3]ferrocenophane fragment in compound 6b is very
likely tilted in respect to the conjugated plane of the adja-
cent benzene ring because of sterical hindrance from the
closely positioned propylidene bridge. The characteristic
UV absorption maxima of a ferrocene core at ꢀ430–450
in the compounds 6a and 6b are significantly blue-shifted
regarding to the related bands for their isomeric counter-
parts 5a and 5c (see Table 1), and this confirms additionally
the previously made statement. Thus, the conformational
configuration where conjugation planes of the aromatic
promesogenic rigid core are tilted from the cyclopentadie-
nyl rings seems unfavorable for appearance of liquid
crystalline properties in [3]ferrocenophane-containing
systems.
It was interesting to compare liquid crystalline behav-
iour of the [3]ferrocenophane compounds 5c, 5d and their
ferrocene analogues [9]. The presence of the propylene
bridge in a ferrocene moiety has a significant effect on the
temperature range of the nematic phase in a case of com-
pound 5c, which shows the broader mesophase (138–
172 °C, see Table 2) than its corresponding ferrocene cou-
nerpart (154–165 °C [9]). The nematic phase in [3]ferroce-
The propylidene bridge in mesogenic [3]ferrocenophane
compound 5c extends the long axis of the molecule, while
in [3]ferrocenophane compound 6b it increases overall
bulkiness of the ferrocene group in perpendicular direction
to the molecular long axis (see Fig. 4). Compound 6b
exhibits poor mesomorphism as result of this unfavourable
geometry.
Table 2
Phase behaviour of the compounds 5a–d, 6a,b, 7a,b, 8a,b, and 14
Compound
Crystal
T (°C)
Mesophase type
T (°C)
Isotropic liquid
5a
5b
5c
5d
6a
6b
7a
7b
8a
8b
14
n
n
n
n
n
n
n
n
n
n
n
[65]a
–
138
130
–
[66]b
–
ꢂNCol
–
ꢂN
ꢂN
–
116
52
n
n
n
n
n
n
n
n
n
n
172
163
105
153
60
121
116
178
ꢂN
–
–
–
112
[155]
[118]
[124]
ꢂN
ꢂSmX
ꢂSmC
ꢂN
152 (192)c
n
a
Monotropic phase transition: anisotropic optical textures observed at fast cooling from isotropic liquid, while at slow cooling crystallization of the
sample occured.
b
Homeotropic texture was observed at fast cooling before crystallization occured.
The monotropic nematic and smectic C mesophases were observed at fast cooling from the isotropic liquid state; at slow cooling and keeping sample
c
between 130 and 140 °C crystallization in the another crystal form occurs, which melted at 192 °C.

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O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
Fig. 2. Photomicrographs of optical textures observed under a polarizing microscope: (a) schlieren texture observed at 60 °C in a super-cooled sample of
compound 5a; (b) focal-conic texture with crystallization areas observed in a super-cooled sample of compound 5a at 35 °C; (c) marbled texture of the
nematic phase in compound 5c at 156 °C; (d) homeotropic texture with crystallization areas observed at 66 °C in a super-cooled sample of compound 6b;
and (e) crystallization of compound 6b upon slow cooling from the isotropic liquid phase.
Fig. 3. Photomicrographs under a polarizing microscope: (a) compound 8a at 115 °C, nematic–isotropic liquid transition; (b) homeotropic texture
observed in compound 8a upon cooling from the isotropic liquid phase; (c) the smectic phase observed in compound 8b at 156 °C upon cooling from the
isotropic liquid; and (d) the smectic phase of compound 8b with crystallization areas.

O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
5577
including cyclopentadiene rings of the ferrocene fragment,
while in the former compound two adjacent benzene rings
attached to the ferrocene moiety constrain each other, and,
as consequence, their alignment in one plane with a cyclo-
pentadien ring is hindered. Over again this confirmed by
hypsochromic shift of the UV absorption maximum of
the central iron atom at 446 nm in the compound 7b in
comparison with the analogous band for the isomer 8b
(see Table 1). Hence, [3]ferrocenophane derivatives 7a
and 7b did not exhibit liquid crystalline properties, whereas
compounds 8a and 8b displayed mesomorphism. Though,
mesomorphism of the latter compounds was merely poor
due to their still not enough favourable molecular shapes.
The b-aminovinyl ketone 14 showed complex thermal
behaviour upon subsequent heating and cooling processes
(see Table 2). When a sample of the compound was heated
fast, it melted to an isotropic state near 150 °C. On the
immediate rapid cooling the monotropic nematic phase
was observed at 124 °C, then smectic C at 118 °C which
crystallizes upon further cooling below 110 °C (see Fig. 6
for optical textures). This cycle can be repeated if the heat-
ing and cooling processes are performed fast enough.
When cooling from the isotropic phase is carried out slowly
[3]ferrocenophane-containing b-aminovinyl ketone 14 crys-
tallizes in the temperature range of 150–125 °C into
another crystal form. This second crystal form is rather
high-melting (192 °C) in comparison with the first crystal
form. The low-melting crystal form develops only upon
fast cooling from the clearing point down to 124 °C, and
further cooling from the liquid crystalline state. Generally,
a sample of compound 14 after consequent heating-cooling
cycles comprises a mixture both of the crystal forms in dif-
ferent ratios depending on its thermal prehistory. It is
noticeable that the analogous b-aminovinyl ketone on the
base of unbridged ferrocene was non-mesogenic [10]. This
confirms above made suggestion that inclusion of the pro-
pylidine bridge into a ferrocene unit boost up liquid crys-
talline properties.
Fig. 4. Computer simulation of the molecules of compounds 5c and 6b by
HYPERCHEM-7 program (Hypercube Inc.).
Fig. 5. Computer simulation of the molecules of compounds 7b and 8b by
HYPERCHEM-7 program (Hypercube Inc.).
Generally, both the di-substituted [3]ferrocenophanes 7b
and 8b have undesirable stereometrical shapes for appear-
ance of liquid crystalline properties (see Fig. 5). However,
the heteroannular di-substituted compound 8b showed a
thermodynamically unstable mesophase (monotropic) (see
Table 2). In comparison with the homoannularly di-substi-
tuted [3]ferrocenophane 7b the compound 8b has no
restrictions for effective conjugation of all aromatic rings
We suggest that the observed phase transformations in
the b-aminovinyl ketone 14 are connected with the
equilibrium of its keto-enamine and imino-enol tautomers
(see Scheme 4). Fig. 7 represents the computer simulated
Fig. 6. Photomicrographs of compound 14 under a polarizing microscope: (a) marbled texture of the nematic phase at 124 °C; and (b) broken fan-shaped
texture of smectic C phase at 112 °C.

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O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
Interesting phenomenon of complex thermal behaviour
was observed in [3]ferrocenophane-containing b-aminovi-
nylketone, when the compound has rather differing isotro-
pic liquid transition temperatures depending on the
thermal history of sample. We suggested rationalizing this
by taking into consideration keto-enamine – imino-enol
tautomeric equilibrium occurring in b-aminovinylketones.
Geometric shapes of the respective tautomers have a signif-
icant influence on molecular packing of crystals, and, con-
sequently, on their melting points. Separate crystallization
of the imino-enol form from a liquid mixture of tautomers
can be realized at certain temperatures due to the substan-
tial difference in isotropic liquid transition temperatures for
two tautomers.
Fig. 7. Computer simulation of imino-enol and keto-enamine tautomeric
forms of compound 14 by HYPERCHEM-7 program (Hypercube Inc.).
molecular models of these two tautomers. Molecules of the
keto-enamine tautomer are bent as the r-electronic system
of the nitrogen atom has a pyramidal configuration in this
case. On the contrary p-electrons of the imine bond in the
imino-enol are fully integrated into a conjugational
sequence with the aromatic system. As a result molecules
of compound 14 in the latter tautomer have less flexible
rod-like shape. We believe that the initial low-melting bent
keto-enamine tautomer after the first melt transforms into
more plane, and, consequently, higher-melting imino-enol
tautomer. Separate crystallization of the imino-enol form
becomes possible mainly due to the substantial difference
in isotropic liquid transition temperatures for two tautom-
ers. If the cooling is performed slowly enough, the imino-
enol tautomer starts to crystallize and leaves the liquid
phase zone consecutively shifting the tautomeric equilib-
rium towards imino-enol side. Eventually all the sample
crystallizes mainly into the latter form if it was kept long
enough at the temperatures 125–140 °C. If the cooling from
an isotropic liquid is carried out rapidly down to 125 °C
and lower the first tautomer still representes in a mixture
of the tautomers by considerable amounts and can be crys-
tallized from the intermediate liquid crystalline phases.
4. Experimental
4.1. General details
Melting points were determined by the capillary
method. Liquid crystalline properties were studied using
a polarizing optical microscope ‘‘Olympus BH-2’’ equipped
with a heating stage HS1 (INSTEC) and remote tempera-
ture controller RTC1 (INSTEC). Photomicrographs were
taken with a camera from Nikon. IR spectra were recorded
by using a Perkin–Elmer Paragon 1000 instrument. Mass
spectra were obtained with a spectrometer MAT 8200
(Finnigan) by electron and chemical ionisation methods
at 70 eV. UV and visible spectra in the region of 250–600
nm were recorded on a spectrophotometer Lambda-14
1
(Perkin–Elmer) in CH2Cl2. H NMR spectra were mea-
sured on spectrometers ARX 300 and ARX 200 (Bruker)
with TMS as an internal standard. All organic and inor-
ganic materials used in the syntheses were purchased from
Sigma–Aldrich or FLUKA if it is not stated otherwise. Sol-
vents were dried and distilled before using.
4.1.1. 3-(4-Aminophenyl)[3]ferrocenophane (1)
3. Conclusions
A mixture of 3-(p-nitrophenyl)[3]ferrocenophane [4]
(1.00 g, 2.880 mmol), SnCl2 Æ 2H2O (2.60 g, 11,522 mmol)
and aqueous HCl (conc.) (5 mL) were refluxed for 2 h in
a mixture iPrOH/H2O (1:1) (50 mL). A solution changes
color from purple to yellow at the end of reaction. The
resulting mixture was treated with Na2CO3 until obtaining
pH 7. Isopropanol was evaporated in a rotary evaporator,
and then the obtained yellow suspension was extracted
with CH2Cl2. An aqueous layer was separated, extracted
again with dichloromethane, and the combined organic
layers were dried over an anhydrous Na2SO4. A sodium
sulphate was filtered off, and dichloromethane was evapo-
rated to dryness. The obtained residue was recrystallized
from EtOH. Yield 0.86 g (94.1%). Yellowish orange pow-
der, m.p. 95 °C. 1H NMR (200 MHz, CDCl3, 25 °C):
d = 1.85–2.05 (m, 6H, C3H6 bridge), 3.41 (m, 1H,
C5H3Fe), 3.20–3.70 (br. s, 2H, NH2), 3.87 (m, 1H,
C5H3Fe), 4.03 (m, 1H, C5H3Fe), 4.18 (m, 2H, C5H4Fe),
4.38 (m, 2H, C5H4Fe), 6.57 (m, 2H, C6H4), 7.22 (m, 2H,
Remarkable relationship between liquid crystalline
properties and geometrical isomerism in mono- and di-
substituted [3]ferrocenophane derivatives was demon-
strated. In mono-substituted [3]ferrocenophanes inclusion
of the propylidene bridge to a ferrocene fragment in b-posi-
tion to a promesogenic substituent enhances the liquid
crystalline properties, while the propylidene in a-position
is less favourable for mesomorphism. It was shown that
3-p-aminophenyl[3]ferrocenophane is a superior building
block for the syntheses of ferrocenyl liquid crystals.
A series of mesogenic structures were synthesized on the
base of an isomeric pair of 3,4-di- and 3,40-bis-p-aminophe-
nyl[3]ferrocenophanes. Generally, the molecular shapes of
these isomers are not favourable for revealing mesomor-
phism. Though heteroannularly bis-substituted [3]ferroce-
nophane azomethines exhibited some poor liquid
crystalline properties.

O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
5579
~
C6H4). IR (KBr tablet): m ¼ 3458:3 (N–H), 3368.3 (N–H),
408.3189; found: 408.1449. Anal. Calc. for C25H24FeN2:
C, 73.54; H, 5.92; N, 6.86. Found: C, 73.67; H, 5.78; N,
6.81%.
2906.1 (C–H), 2835.5 (C–H), 1620.9, 1531.5, 1469.4,
1430.5, 1276.3, 1043.4, 829.0, 801.8 cmꢁ1. Anal. Calc. for
C19H19FeN: C, 71.94; H, 6.04; N, 4.41. Found: C, 72.03;
H, 6.07; N, 4.38%.
4.1.5. 4-Dodecyloxybenzaldehyde (10a)
A solution of 4-hydroxybenzaldehyde 9a (6.9783 g,
4.1.2. 2-(4-Aminophenyl)[3]ferrocenophane (2)
0.0571 mol)
and
1-bromododecane
(14.2423 g,
Prepared as described above by reduction of 2-(p-nitro-
phenyl)[3]ferrocenophane [4] (0.15 g, 0.432 mmol) with
SnCl2 Æ 2H2O (0.6 g, 2.659 mmol) in a mixture of iPrOH/
H2O (1:1) (10 mL) and HCl (conc.) (1 mL). The obtained
yellow oil (0.13 g) was purified by column chromatography
(Al2O3, eluent CH2Cl2). Yield 0.07 g (51.1%). Yellow oil.
1H NMR (200 MHz, CDCl3, 25 °C): d = 1.85–2.00 (m,
4H, C3H6 bridge), 2.00–2.10 (m, 1H, C3H6 bridge) 2.30–
2.45 (m, 1H, C3H6 bridge), 3.24 (m, 1H, C5H3Fe), 3.40–
3.80 (br. s, 2H, NH2), 3.93 (m, 1H, C5H3Fe), 4.00 (m,
1H, C5H3Fe), 4.06 (m, 2H, C5H4Fe), 4.25 (m, 2H,
C5H4Fe), 6.63 (m, 2H, C6H4), 7.23 (m, 2H, C6H4). IR
0.0571 mol) in acetone (50 mL) was refluxed for 48 h in
the presence of an anhydrous potassium carbonate (15 g).
Inorganic salts were filtered off, and acetone was evapo-
rated to dryness. The residue was distilled under vacuum
(165–170 °C/0.007 mm Hg). Yield 12.3764 g (74.8%). Light
yellow oil, which crystallize upon cooling below 0 °C as
paraffin-like solid. 1H NMR (200 MHz, CDCl3, 25 °C):
d = 0.87 (t, 3H, CH3), 1.29 (m, 18H, CH2), 1.77 (m, 2H,
CH2CH2O), 4.05 (t, 2H, CH2O), 6.92 (m, 2H, C6H4),
7.77 (m, 2H, C6H4), 9.79 (s, 1H, CHO).
4.1.6. 2-Hydroxy-4-dodecyloxybenzaldehyde (10b)
~
(KBr tablet): m ¼ 3451:4 (N–H), 3369.1 (N–H), 2915.0
Prepared as described above from 2,4-dihydroxybenzal-
dehyde 9b (7.8143 g, 0.0566 mol) and 1-bromododecane
(14.1010 g, 0.0566 mol) in a slurry of anhydrous potassium
carbonate (40 g) in acetone (100 mL). The residue after
evaporation of acetone was crystallized from ethanol.
Yield 13.1856 g (76.0%). White powder, m.p. 49–50 °C.
1H NMR (200 MHz, CDCl3, 25 °C): d = 0.87 (t, 3H,
CH3), 1.30 (m, 18H, CH2), 1.75 (m, 2H, CH2CH2O), 4.00
(t, 2H, CH2O), 6.39 (m, 1H, C6H3), 6.51 (m, 1H, C6H3),
7.40 (m, 1H, C6H3), 9.71 (s, 1H, CHO), 11.45 (s, 1H, OH).
(C–H), 2844.3 (C–H), 1620.0, 1524.2, 1437.3, 1277.3,
1044.0, 830.0, 800.8 cmꢁ1. Anal. Calc. for C19H19FeN: C,
71.94; H, 6.04; N, 4.41. Found: C, 72.08; H, 6.01; N, 4.45%.
4.1.3. 3,40-Di(4-aminophenyl)[3]ferrocenophane (3)
Prepared as described above by reduction of 3,4-di-(4-
nitrophenyl)[3]ferrocenophane [4] (0.0792 g, 0.169 mmol)
with SnCl2 Æ 2H2O (0.2891 g, 1.281 mmol) in a mixture of
iPrOH/H2O (2:1) (20 mL) and HCl (conc.) (0.4 mL). The
product was crystallized from dichloromethane solution
by adding EtOH and evaporating CH2Cl2. Yield 0.0681 g
4.1.7. 4-Dodecyloxyacetophenone (12)
1
(98.6%). Yellowish orange powder, m.p. 112 °C. H NMR
Prepared as described above from 4-hydroxyacetophe-
none 11 (30.20 g, 0.1212 mol) and 1-bromododecane
(16.51 g, 0.1212 mol) in a slurry of anhydrous potassium
carbonate (35 g) in acetone (100 mL). The product was
crystallized from ethanol. Yield 35 g (95%). White crystals,
m.p. 58–59 °C. 1H NMR (200 MHz, CDCl3, 25 °C):
d = 0.85 (t, 3H, CH3), 1.28 (m, 18H, CH2), 1.75 (m, 2H,
CH2CH2O), 1.49 (s, 3H, CH3CO), 3.97 (t, 2H, CH2O),
6.80 (m, 2H, C6H4), 7.81 (m, 2H, C6H4).
(200 MHz, CDCl3, 25 °C): d = 1.80–2.15 (m, 6H, C3H6
bridge), 2.50–3.50 (br. s, 4H, NH2), 3.74 (m, 2H,
C5H4Fe), 4.15 (m, 2H, C5H4Fe), 4.29 (s, 2H, C5H2Fe),
6.52 (m, 2H, C6H4), 7.15 (m, 2H, C6H4). IR (KBr tablet):
~
m ¼ 3428:2 (N–H), 3361.0 (N–H), 1917.3 (C–H), 2845.7
(C–H), 1618.3, 1522.6, 1279.2, 1176.2, 830.6 cmꢁ1. MS
(70 eV): m/z (%): 408 (100) [M+]; C25H24FeN2: calc.:
408.3189; found 408.1278. Anal. Calc. for C25H24FeN2: C,
73.54; H, 5.92; N, 6.86. Found: C, 73.78; H, 5.98; N, 6.79%.
4.1.8. 4-Dodecyloxybenzoic acid (17)
4.1.4. 3,40-Bis-(4-aminophenyl)[3]ferrocenophane (4)
Prepared as described above by reduction of 3,40-bis-(4-
nitrophenyl)[3]ferrocenophane [4] (0.1203 g, 0.257 mmol)
with SnCl2 Æ 2H2O (0.4535 g, 2.010 mmol) in a mixture of
iPrOH/H2O (2:1) (25 mL) and HCl (conc.) (0.6 mL). The
product was crystallized from dichloromethane solution
by adding EtOH and evaporating CH2Cl2. Yield 0.1001 g
A mixture of ethyl ester of 4-hydroxy benzoic acid 15
(25.0 g, 0.150 mol) and 1-bromododecane (37.5 g,
0.150 mol) was refluxed for 50 h in a slurry of potassium
carbonate (130 g) in acetone (250 mL). Inorganic salts were
filtered off and the filtrate was evaporated to dryness. A
solution of potassium hydroxide (8.4 g, 0.150 mol) in a
mixture of water/ethanol (100 mL/100 mL) was added to
the residue of crude ester 16, and the mixture was refluxed
for 24 h. Then an aqueous HCl (conc.) (6 mL) was added
and refluxing was continued for 2 h. The obtained white
precipitate was filtered off and washed several times with
water, and two times with ethanol. Yield 44.3 g (96.4%).
White powder, Cr–SA 94 °C, SA–N 131 °C, N–I 139 °C.
1H NMR (200 MHz, CDCl3, 25 °C): d = 0.87 (t, 3H,
CH3), 1.30 (m, 18H, CH2), 1.76 (m, 2H, CH2CH2O), 3.98
1
(95.4%). Yellowish orange powder, m.p. 91 °C. H NMR
(200 MHz, CDCl3, 25 °C): d = 1.85–2.10 (m, 6H, C3H6
bridge), 2.70–4.10 (br. s, 4H, NH2), 3.78 (m, 2H,
C5H3Fe), 4.25 (m, 2H, C5H3Fe), 4.32 (m, 2H, C5H3Fe),
6.59 (m, 2H, C6H4), 7.16 (m, 2H, C6H4). IR (KBr tablet):
~m ¼ 3428:2 (N–H), 3359.2 (N–H), 2907.3 (C–H), 2837.4
(C–H), 1618.2, 1528.3, 1275.5, 1179.1, 829.0 cmꢁ1. MS
(70 eV): m/z (%): 408 (100) [M+]; C25H24FeN2: calc.:

5580
O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
(t, 2H, CH2O), 6.84 (m, 2H, C6H4), 7.90 (m, 2H, C6H4), 9–
10 (very br. s, 1H, COOH).
(m, 2H, C6H4), 8.42 (s, 1H, CH@N). IR (KBr tablet):
~
m ¼ 2919:4 (C–H), 2846.5 (C–H), 1607.9 (CH@N),
1568.9, 1519.6, 1465.5, 1421.6, 1304.1, 1247.2, 1162.4,
848.2 cmꢁ1; MS (70 eV): m/z (%): 589 (100) [M+], 420
(11.58) [M+ꢁC12H25]; C38H47FeNO: calc.: 589.6345;
found: 589.3024. Anal. Calc. for C38H47FeNO: C, 77.40;
H, 8.03; N, 2.37. Found: C, 77.63; H, 7.98; N, 2.34%.
4.1.9. 4-(4-Dodecyloxybenzoyloxy)benzaldehyde (19a)
A mixture of 4-dodecyloxybenzoic acid 17 (6.21 g,
0.0203 mol) and thionyl chloride (20 mL) was refluxed for
5 h, then SOCl2 excess was distilled off under atmospheric
pressure. The remaining SOCl2 was removed at room tem-
perature by applying vacuum for 1 h. This fresh chloridic
anhydride 18 was dissolved in dry benzene (20 mL) and
added dropwise during 45 min to a stirred solution of 4-
hydroxybenzaldehyde 9a (2.48 g, 0.0203 mol) in a mixture
pyridine/benzene (10 mL/10 mL). The reaction mixture
was refluxed for 4 h, then cooled down and stirred at room
temperature overnight. The obtained products were poured
into 100 mL of water. The organic layer was separated in a
separating funnel and washed with diluted aqueous HCl,
then separated again and dried over a sodium sulphate.
Drying agent was filtered off and the filtrate was evapo-
rated to dryness. The residue was recrystallized from etha-
nol. Yield 7.69 g (92.3 %). White powder, Cr–N 66 °C, N–I
77 °C. 1H NMR (200 MHz, CDCl3, 25 °C): d = 0.90 (t, 3H,
CH3), 1.26 (m, 18H, CH2), 1.79 (m, 2H, CH2CH2O), 3.98
(t, 2H, CH2O), 6.86 (m, 2H, C6H4), 7.27 (m, 2H, C6H4),
7.82 (m, 2H, C6H4), 8.04 (m, 2H, C6H4), 9.83 (s, 1H,
CHO).
4.2.2. 3-[4-(2-Hydroxy-4-dodecyloxybenzaldimino)phenyl]
[3]ferrocenophane (5b)
Prepared from 3-(4-aminophenyl)[3]ferrocenophane 1
(0.1424 g, 0.449 mmol) and compound 10b (0.1534 g,
0.500 mmol). Yield 0.2379 g (87.3%). Yellowish orange
1
powder. H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t,
3H, CH3), 1.27 (m, 18H, CH2), 1.79 (m, 2H, CH2CH2O),
1.90–2.15 (m, 6H, C3H6 bridge), 3.44 (m, 1H, C5H3Fe),
3.89 (m, 1H, C5H3Fe), 4.00 (t, 2H, CH2O), 4.11 (m, 1H,
C5H3Fe), 4.22 (m, 2H, C5H4Fe), 4.49 (m, 2H, C5H4Fe),
6.44 (m, 1H, C6H3), 6.55 (m, 1H, C6H3), 7.10 (m, 2H,
C6H4), 7.42 (m, 2H, C6H4), 8.08 (m, 1H, C6H3), 8.86 (s,
~
1H, CH@N). IR (KBr tablet): m ¼ 2918:8 (C–H), 2848.8
(C–H), 1608.1 (CH@N), 1592.5, 1519.2, 1466.9, 1431.7,
1316.2, 1279.4, 1185.6, 1102.0, 816.5 cmꢁ1. MS (70 eV):
m/z (%): 605 (100) [M+]. Anal. Calc. for C38H47FeNO2:
C, 75.36; H, 7.82; N, 2.31. Found: C, 75.08; H, 7.98; N,
2.27%.
4.1.10. 2-Hydroxy-4-(4-dodecyloxybenzoyloxy)
benzaldehyde (19b)
4.2.3. 3-{4-[4-(4-Dodecyloxybenzoyloxy)benzaldimino]
phenyl}[3]ferrocenophane (5c)
Prepared in a previous manner by esterification reaction
between 4-hydroxysalicylaldehyde 9b (3.5231 g, 0.0255
mol) and 4-dodecyloxybenzoic acid (7.8168 g, 0.0255
mol). Yield 5.5407 g (50.9%). White fibrous crystals, m.p.
73–74 °C.
Prepared from 3-(4-aminophenyl)[3]ferrocenophane 1
(0.2503 g, 0.789 mmol) and compound 19a (0.3255 g,
0.792 mmol). Yield 0.3968 g (70.8%). Yellowish orange
1
powder. H NMR (300 MHz, CDCl3, 25 °C):d = 0.88 (t,
3H, CH3), 1.24–1.35 (m,18H, CH2), 1.82 (m, 2H,
CH2CH2O), 1.90–2.10 (m, 6H, C3H6 bridge), 3.44 (m,
1H, C5H3Fe), 3.90 (m, 1H, C5H3Fe), 4.04 (t, 2H, CH2O),
4.13 (m, 1H, C5H3Fe), 4.23 (m, 2H, C5H4Fe), 4.52 (m,
2H, C5H4Fe), 6.97 (m, 2H, C6H4), 7.14 (m, 2H, C6H4),
7.33 (m, 2H, C6H4), 7.44 (m, 2H, C6H4), 7.96 (m, 2H,
C6H4), 8.15 (m, 2H, C6H4), 8.51 (s, 1H, CH@N). IR
4.2. General procedure for obtaining Schiff’s bases (5–8)
Ferrocenophane-containing amines 1–4 were dissolved
in minimal amount of hot ethanol and added to a solution
of slightly excess from equimolar quantity of the appropri-
ate aldehydes 10, 19. The reaction mixtures were refluxed
for 0.5–1 h. The precipitate obtained after cooling of the
mixture was filtered, then recrystallized from ethanol, or
reprecipitated from a CH2Cl2 solution by adding ethanol.
Yields varied from 70% to 95%.
~
(KBr tablet): m ¼ 2920:4 (C–H), 2849.9 (C–H), 1720.8
(C@O), 1610.0 (CH@N), 1514.5, 1466.1, 1320.2, 1267.6,
1206.9, 1173.7, 1161.0, 1079.9, 845.6 cmꢁ1. MS (70 eV):
m/z (%): 709 (100) [M+], 420 (15.04) [M+ꢁC12H25-
OC6H4CO], 289 (17.66) [C12H25OC6H4CO+], 120 (64.02)
[OC6H4CO+]; C45H51FeNO3: calc.: 709.7406; found:
709.7062. Anal. Calc. for C45H51FeNO3: C, 76.15; H,
7.24; N, 1.97. Found: C, 76.02; H, 7.18; N, 1.92%.
4.2.1. 3-[4-(4-Dodecyloxybenzaldimino)phenyl][3]
ferrocenophane (5a)
Prepared from 3-(4-aminophenyl)[3]ferrocenophane 1
(0.5128 g, 1.618 mmol) and compound 10a (0.4955 g,
1.706 mmol). Yield 0.8322 g (87.0%). Light orange powder.
1H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t, 3H, CH3),
1.27 (m, 18H, CH2), 1.81 (m, 2H, CH2CH2O), 1.90–2.15
(m, 6H, C3H6 bridge), 3.43 (m, 1H, C5H3Fe), 3.90 (m,
1H, C5H3Fe), 4.01 (t, 2H, CH2O), 4.12 (m, 1H, C5H3Fe),
4.23 (m, 2H, C5H4Fe), 4.50 (m, 2H, C5H4Fe), 6.96 (m,
2H, C6H4), 7.10 (m, 2H, C6H4), 7.42 (m, 2H, C6H4), 7.83
4.2.4. 3-{4-[2-Hydroxy-4-(4-dodecyloxybenzoyloxy)
benzaldimino]phenyl}[3]ferrocenophane (5d)
Prepared from 3-(4-aminophenyl)[3]ferrocenophane 1
(0.1443 g, 0.455 mmol) and compound 19b (0.1941 g,
0.455 mmol). Yield 0.2561 g (77.5%). Yellowish orange
1
powder. H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t,
3H, CH3), 1.24–1.35 (m, 18H, CH2), 1.82 (m, 2H,
CH2CH2O), 1.90–2.10 (m, 6H, C3H6 bridge), 3.44 (m,

O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
5581
1H, C5H3Fe), 3.90 (m, 1H, C5H3Fe), 4.04 (t, 2H, CH2O),
4.15 (m, 1H, C5H3Fe), 4.24 (m, 2H, C5H4Fe), 4.52 (m,
2H, C5H4Fe), 6.82 (dd, J1(H,H) = 2.24 Hz, J2(H,H) =
8.37 Hz, 1H, C6H3), 6.88 (d, J1(H,H) = 2.24 Hz, 1H,
C6H3), 6.97 (m, 2H, C6H4), 7.19 (m, 2H, C6H4), 7.42 (d,
J2(H,H) = 8.37 Hz, 1H, C6H3), 7.46 (m, 2H, C6H4), 8.14
(m, 2H, C6H4), 8.66 (s, 1H, CH@N). IR (KBr tablet):
found: 709.6663. Anal. Calc. for C45H51FeNO3: C, 76.15;
H, 7.24; N, 1.97. Found: C, 76.32; H, 7.31; N, 1.91%.
4.2.7. 3,4-Di[4-(4-dodecyloxybenzaldimino)phenyl][3]
ferrocenophane (7a)
Prepared from 3,4-di(4-aminophenyl)[3]ferrocenophane
3 (0.0320 g, 0.078 mmol) and compound 10a (0.0455 g,
0.158 mmol). Yield 0.0615 g (82.5%). Yellowish orange
amorphous solid. 1H NMR (300 MHz, CDCl3, 25 °C):
d = 0.88 (t, 6H, CH3), 1.24–1.37 (m, 36H, CH2), 1.80 (m,
4H, CH2CH2O), 1.95–2.10 (m, 6H, C3H6 bridge), 3.81
(m, 2H, C5H4Fe), 4.01 (t, 4H, CH2O), 4.22 (m, 2H,
C5H4Fe), 4.44 (s, 2H, C5H2Fe), 6.97 (m, 4H, C6H4), 7.05
(m, 4H, C6H4), 7.37 (m, 4H, C6H4), 7.83 (m, 4H, C6H4),
8.42 (s, 2H, CH@N). MS (70 eV): m/z (%): 952 (100)
[M+ꢁH]; C63H80FeN2O2: calc.: 953.1724; found:
953.1212. Anal. Calc. for C63H80FeN2O2: C, 79.38; H,
8.46; N, 2.94. Found: C, 79.12; H, 8.28; N, 2.90%.
~
m ¼ 2918:5 (C–H), 2848.0 (C–H), 1724.1 (C@O), 1601.9
(CH@N), 1522.2, 1466.8, 1251.9, 1167.4, 1149.3, 1117.9,
1064.2, 837.9 cmꢁ1. MS (70 eV): m/z (%): 725 (100) [M+],
436
(87.53)
[M+ꢁC12H25OC6H4CO],
289
(7.68)
[C12H25OC6H4CO+], 120 (50.76) [OC6H4CO+]; C45H51-
FeNO4: calc.: 725.7400; found: 725.5511. Anal. Calc. for
C45H51FeNO4: C, 74.47; H, 7.08; N, 1.93. Found: C,
74.62; H, 7.16; N, 1.91%.
4.2.5. 2-[4-(4-Dodecyloxybenzaldimino)phenyl][3]
ferrocenophane (6a)
Prepared from 2-(4-aminophenyl)[3]ferrocenophane 2
(0.0247 g, 0.078 mmol) and compound 10a (0.0236 g,
0.081 mmol). Yield 0.0428 g (93.2%). Yellowish orange
4.2.8. 3,4-Di{4-[4-(4-dodecyloxybenzoyloxy)benzaldimino]
phenyl}[3]ferrocenophane (7b)
1
powder. H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t,
Prepared from 3,4-di(4-aminophenyl)[3]ferrocenophane
3 (0.0251 g, 0.061 mmol) and compound 19a (0.0505 g,
0.123 mmol). Yield 0.0650 g (88.0%). Yellowish orange
3H, CH3), 1.25–1.35 (m, 18H, CH2), 1.81 (m, 2H,
CH2CH2O), 1.88–2.00 (m, 4H, C3H6 bridge), 2.09 (m,
1H, C3H6 bridge), 2.44 (m, 1H, C3H6 bridge), 3.25 (m,
1H, C5H3Fe), 3.95 (m, 1H, C5H3Fe), 4.02 (t, 2H, CH2O),
4.02 (m, 1H, C5H3Fe), 4.13 (m, 2H, C5H4Fe), 4.31 (m,
1H, C5H4Fe), 4.36 (m, 1H, C5H4Fe), 6.97 (m, 2H, C6H4),
7.14 (m, 2H, C6H4), 7.44 (m, 2H, C6H4), 7.84 (m, 2H,
1
powder. H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t,
6H, CH3), 1.25–1.35 (m, 36H, CH2), 1.82 (m, 4H,
CH2CH2O), 1.95–2.10 (m, 6H, C3H6 bridge), 3.83 (m,
2H, C5H4Fe), 4.05 (t, 4H, CH2O), 4.23 (m, 2H, C5H4Fe),
4.46 (s, 2H, C5H2Fe), 6.98 (m, 4H, C6H4), 7.08 (m, 4H,
C6H4), 7.33 (m, 4H, C6H4), 7.40 (m, 4H, C6H4), 7.97 (m,
4H, C6H4), 8.15 (m, 4H, C6H4), 8.52 (s, 2H, CH=N). IR
~
C6H4), 8.44 (s, 1H, CH@N). IR (KBr tablet): m ¼ 2917:7
(C–H), 2849.2 (C–H), 1602.1 (CH@N), 1584.7, 1510.1,
1466.1, 1248.8, 1160.2, 848.3 cmꢁ1. MS (70 eV): m/z (%):
589 (100) [M+], 420 (7.67) [M+ꢁC12H25]; C38H47FeNO:
calc.: 589.6345; found: 589.4709. Anal. Calc. for
C38H47FeNO: C, 77.40; H, 8.03; N, 2.37. Found: C,
77.59; H, 8.09; N, 2.31%.
~
(KBr tablet): m ¼ 2921:8 (C–H), 2850.9 (C–H), 1734.0
(C@O), 1604.0 (CH@N), 1510.9, 1466.5, 1257.3, 1200.9,
1165.6, 1064.5, 843.7 cmꢁ1. MS (70 eV): m/z (%): 1192
(88.61) [M+ꢁH], 903 (15.76) [M+ꢁC12H25OC6H4CO],
289 (19.11) [C12H25OC6H4CO+], 120 (100) [OC6H4CO+];
C77H88FeN2O6: calc.: 1193.3846; found: 1192.8614. Anal.
Calc. for C77H88FeN2O6: C, 77.50; H, 7.43; N, 2.35.
Found: C, 77.73; H, 7.54; N, 2.41%.
4.2.6. 2-{4-[4-(4-Dodecyloxybenzoyloxy)benzaldimino]
phenyl}[3]ferrocenophane (6b)
Prepared from 2-(4-aminophenyl)[3]ferrocenophane 2
(0.0304 g, 0.096 mmol) and compound 19a (0.0393 g,
0.096 mmol). Yield 0.0473 g (69.7%). Yellowish orange
4.2.9. 3,40-Bis-[4-(4-dodecyloxybenzaldimino)phenyl][3]
ferrocenophane (8a)
1
powder. H NMR (300 MHz, CDCl3, 25 °C): d = 0.88 (t,
Prepared from 3,40-bis-(4-aminophenyl)[3]ferroceno-
phane 4 (0.0245 g, 0.060 mmol) and compound 10a
(0.0365 g, 0.126 mmol). Yield 0.0423 g (73.4%). Yellowish
orange powder. 1H NMR (300 MHz, CDCl3, 25 °C):
d = 0.88 (t, 6H, CH3), 1.24–1.50 (m, 36H, CH2), 1.80 (m,
4H, CH2CH2O), 2.00 (m, 6H, C3H6 bridge), 3.91 (m, 2H,
C5H3Fe), 4.02 (t, 4H, CH2O), 4.35 (m, 2H, C5H3Fe), 4.45
(m, 2H, C5H3Fe), 6.98 (m, 4H, C6H4), 7.13 (m, 4H,
C6H4), 7.35 (m, 4H, C6H4), 7.85 (m, 4H, C6H4), 8.46 (s,
3H, CH3), 1.25–1.35 (m, 18H, CH2), 1.82 (m, 2H,
CH2CH2O), 1.88–1.97 (m, 4H, C3H6 bridge), 2.10 (m,
1H, C3H6 bridge), 2.45 (m, 1H, C3H6 bridge), 3.26 (m,
1H, C5H3Fe), 3.96 (m, 1H, C5H3Fe), 4.03 (m, 1H,
C5H3Fe), 4.05 (t, 2H, CH2O), 4.14 (m, 2H, C5H4Fe), 4.31
(m, 1H, C5H4Fe), 4.37 (m, 1H, C5H4Fe), 6.98 (m, 2H,
C6H4), 7.18 (m, 2H, C6H4), 7.33 (m, 2H, C6H4), 7.46 (m,
2H, C6H4), 7.98 (m, 2H, C6H4), 8.15 (m, 2H, C6H4), 8.53
~
~
(s, 1H, CH@N). IR (KBr tablet): m ¼ 2919:6 (C–H),
2H, CH@N). IR (KBr tablet): m ¼ 2922:4 (C–H), 2850.8
2849.7 (C–H), 1731.2 (C@O), 1602.7 (CH@N), 1510.2,
1254.3, 1198.0, 1160.0, 1063.6, 1007.6, 843.2 cmꢁ1. MS
(70 eV): m/z (%): 709 (100) [M+], 420 (7.79)
[M+ꢁC12H25OC6H4CO], 289 (40.50) [C12H25OC6H4CO+];
120 (65.18) [OC6H4CO+]; C45H51FeNO3: calc.: 709.7406;
(C–H), 1607.5 (CH@N), 1570.0, 1520.8, 1464.5, 1422.1,
1306.0, 1249.3, 1162.8, 844.3 cmꢁ1. MS (70 eV): m/z (%):
952 (100) [M+ꢁH]; C63H80FeN2O2: calc.: 953.1724; found:
953.1243. Anal. Calc. for C63H80FeN2O2: C, 79.38; H,
8.46; N, 2.94. Found: C, 79.53; H, 8.35; N, 2.97%.

5582
O.N. Kadkin et al. / Journal of Organometallic Chemistry 692 (2007) 5571–5582
4.2.10. 3,40-Bis-{4-[4-(4-dodecyloxybenzoyloxy)
benzaldimino]phenyl}[3]ferrocenophane (8b)
1626.4, 1599.7, 1573.1, 1531.7, 1465.9, 1279.5, 1244.9,
1168.4, 1038.8, 831.2 cmꢁ1. MS (70 eV): m/z (%): 631
(100) [M+], 462 (6.32) [M+ꢁC12H25]; C40H49FeNO2: calc.:
631.6714; found: 631.9114. Anal. Calc. for C40H49FeNO2:
C, 76.06; H, 7.82; N, 2.22. Found: C, 76.23; H, 7.69; N,
2.28%.
Prepared from 3,40-bis-(4-aminophenyl)[3]ferroceno-
phane 4 (0.0290 g, 0.071 mmol) and compound 19a
(0.0583 g, 0.142 mmol). Yield 0.0663 g (78.1%). Yellowish
orange powder. 1H NMR (300 MHz, CDCl3, 25 °C):
d = 0.88 (t, 6H, CH3), 1.25–1.35 (m, 36H, CH2), 1.83 (m,
4H, CH2CH2O), 1.99–2.05 (m, 6H, C3H6 bridge), 3.94
(m, 2H, C5H3Fe), 4.05 (t, 4H, CH2O), 4.23 (m, 2H,
C5H3Fe), 4.47 (m, 2H, C5H3Fe), 6.98 (m, 4H, C6H4),
7.17 (m, 4H, C6H4), 7.34 (m, 4H, C6H4), 7.38 (m, 4H,
C6H4), 7.99 (m, 4H, C6H4), 8.15 (m, 4H, C6H4), 8.56 (s,
Acknowledgements
O.N. Kadkin acknowledges the Deutscher Akademi-
scher Austauschdienst (DAAD). Special thanks to Prof.
Dr. Willy Friedrichsen for his advising and encouraging
this work. We are grateful to Mr. Elmar Schneider and
Ms. Utta Oelbermann for mass, IR and UV spectroscopy
measurements, and Mr. Dirk Mayer, Ms. Wiebke Delfs
~
2H, CH=N). IR (KBr tablet): m ¼ 2920:8 (C–H), 2850.3
(C–H), 1729.8 (C@O), 1603.0 (CH@N), 1510.1, 1255.0,
1197.9, 1158.1, 1064.4, 843.4 cmꢁ1. MS (70 eV): m/z (%):
1192 (69.12) [M+ꢁH], 903 (15.76) [M+ꢁ C12H25O-
C6H4CO], 289 (26.39) [C12H25OC6H4CO+], 120 (100)
[OC6H4CO+]; C77H88FeN2O6: calc.: 1193.3846; found:
1193.3039. Anal. Calc. for C77H88FeN2O6: C, 77.50; H,
7.43; N, 2.35. Found: C, 77.34; H, 7.48; N, 2.39%.
1
and Mr. Holger Franzen for recording H NMR spectra.
Financial support from Korean government program
BK-21 is also gratefully acknowledged.
References
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~
N–H). IR (KBr tablet): m ¼ 2920:5 (C–H), 2850.1 (C–H),