Tunable emissive lanthanidomesogen derived from a room-temperature liquid-crystalline schiff-base ligand

Article abstract of DOI:10.1002/chem.201301666

A novel photoluminescent room-temperature liquid-crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)₃(NO₃) ₃] (Ln=La, Pr, Sm, Gd, Tb, Dy; LH

Full text of DOI:10.1002/chem.201301666

FULL PAPER
DOI: 10.1002/chem.201301666
Tunable Emissive Lanthanidomesogen Derived from a Room-Temperature
Liquid-Crystalline Schiff-Base Ligand
Harun A. R. Pramanik,[a] Gobinda Das,[a] Chira R. Bhattacharjee,*[a] Pradip C. Paul,[a]
Paritosh Mondal,[a] S. Krishna Prasad,[b] and D. S. Shankar Rao[b]
Abstract: A novel photoluminescent
room-temperature liquid-crystalline
salicylaldimine Schiff base with a short
alkoxy substituent and series of
lanthanide(III) complexes of the type
[Ln(LH)3A(NO3)3] (Ln=La, Pr, Sm, Gd,
Tb, Dy; LH=(E)-5-(hexyloxy)-2-
[{2-(2-hydroxyethylamino)ethylimino]-
ACHTUNGTRENNUNGmethyl}phenol) have been synthesized
microscopy (POM) and differential
scanning calorimetry (DSC). The
ligand exhibits an enantiotropic hexag-
onal columnar (Colh) mesophase at
room temperature and the complexes
show an enantiotropic lamellar colum-
nar (ColL) phase at around 1208C with
high thermal stability. Based on XRD
results, different space-filling models
have been proposed for the ligand and
complexes to account for the columnar
mesomorphism. The ligand exhibits in-
tense blue emission both in solution
and in the condensed state. The most
intense emissions were observed for
the samarium and terbium complexes,
with the samarium complex glowing
with a bright-orange light (ca. 560–
644 nm) and the terbium complex
emitting green light (ca. 490–622 nm)
upon UV irradiation. DFT calculations
performed by using the DMol3 pro-
gram at the BLYP/DNP level of theory
revealed a nine-coordinate structure
for the lanthanide complexes.
a
ACHTUNGTRENNUNG
CHTUNGTRENNUNG
and characterized by FTIR, 1H and
13C NMR, UV/Vis, and FAB-MS analy-
ses. The ligand coordinates to the
metal ions in its zwitterionic form. The
thermal behavior of the compounds
was investigated by polarizing optical
Keywords: density functional calcu-
lations · lanthanides · liquid crys-
tals · luminescence · Schiff bases
Introduction
with the structural anisotropy required to exhibit liquid-crys-
talline behavior.[8] Such materials not only possess a large
magnetic anisotropy but also display interesting photophysi-
cal properties.[9] Luminescent liquid crystals, which are
useful for the design of emissive liquid crystal displays
(LCDs), can be obtained by incorporating lanthanide ions
into liquid crystals.[9] In the past few years lanthanidomeso-
gens have received considerable attention both in basic re-
search and for their applications in the field of materials sci-
ence.[10] The first lanthanide-containing liquid crystal with a
Schiff-base ligand that contained two aromatic rings was re-
ported by Galyametdinov et al. in 1991.[11] The complexes
were shown to exhibit a highly viscous SmA mesophase.
Since then a large number of lanthanidomesogens contain-
ing Schiff bases,[8a,e–g,h,10c,e–f,12] porphyrins,[13] phthalocya-
nines,[14] b-enamino ketones,[15] 1,2-phenanthrolines,[16] b-di-
ketonates,[17] and crown ethers[10a,18] have been investigated.
A series of one-ring Schiff bases, although not mesogenic,
have been complexed to lanthanides to produce ordered
mesophases.[8h,18] Very recently we reported a series of lumi-
nescent mesogenic one-ring-containing salicylaldimine Schiff
bases with a long-chain substituent and their lanthanide
complexes.[19a] Both ligands and their complexes were shown
to exhibit smectic mesomorphism. However, exploring the
physicochemical properties of such a luminescent mesogenic
compound is often hampered by their high transition tem-
peratures. The quest for low-temperature luminescent meso-
genic compounds is driven both by interest in realizing
device application and academic curiosity. Since the discov-
Luminescent liquid crystals are considered immensely im-
portant materials for their potential applications in OLEDs,
information storage, sensors, and enhanced contrast displays
because of their excellent luminescent and charge-transport-
ing abilities.[1] The design and planned synthesis of liquid-
crystalline molecules with specific magnetic, electronic, or
luminescent properties desirable for technological applica-
tions is a challenging task for synthetic chemists. Metallo-
mesogens are ideal candidates for such tunable smart multi-
functional properties owing to the optical, electronic, and
magnetic characteristics of metal complexes with anisotropic
fluids.[2–5] Such an amalgamation of luminescent molecules
and soft materials to generate new electronic devices is a
fast growing field of research.[6] The majority of metallo-
ACHTUNGTRENNUNGmesoACHTUNGTRENNUNGgens that have been reported up to now contain d-
block metals.[7] The design of lanthanide-containing liquid
crystals is marred with complication because of their high
coordination numbers that often seem to be incompatible
[a] H. A. R. Pramanik, Dr. G. Das, Prof. C. R. Bhattacharjee,
Dr. P. C. Paul, Dr. P. Mondal
Department of Chemistry, Assam University
Silchar 788011, Assam (India)
Fax: (+91)03842-270342
E-mail: crbhattacharjee@rediffmail.com
[b] Dr. S. K. Prasad, Dr. D. S. S. Rao
Centre for Soft Matter Research
Jalahalli, Bangalore 560013 (India)
Chem. Eur. J. 2013, 19, 13151 – 13159
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
13151

ery of LCDs, room-temperature liquid crystals, due to their
high thermal stability, have enjoyed significant attention.[12g]
Set in this backdrop, in this article we report the synthesis
of a new one-ring O-donor Schiff base derived from an
amino alcohol and its lanthanide complexes [Ln(LH)3-
trate groups appear at characteristic frequencies of around
1484 (n1), 1300 (n4), 1141 (n2), and 813 cmꢀ1 (n3), and the dif-
ference between the two strongest absorptions (n1 and n4) of
the nitrate groups is about 180 cmꢀ1, which clearly shows
that the NO3 groups in the solid complexes coordinate to
the lanthanide ion as bidentate ligands.[8f,10c,20] The FAB
mass spectra of the ligand and their LnIII complexes are in
good agreement with their formula masses. The 1H NMR
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
mesomorphism. Interestingly, the ligand is mesogenic at
room temperature. Although a luminescent liquid crystalline
one-ring Schiff base has recently been recorded,[19a] this ap-
pears to be the first example of a room-temperature-based
one-ring Schiff-base mesogen. Also pertinent here is to
mention that there is no report of a one-ring lanthanidomes-
ogen that exhibits columnar mesomorphism.
spectrum of the diamagnetic lanthanum
ACHTUNGTREN(NUGN III) complex shows
that the signal corresponding to the imine hydrogen, CH=N,
3
is split into a doublet (d=7.61 and 7.62 ppm with JH-H
=
12 Hz) in contrast to the singlet of the free Schiff-base
ligand (d=8.11 ppm), which suggests protonation of the
imine nitrogen. Furthermore, a new signal, characteristic of
an N+H resonance, appears in the spectrum of the complex
at d=12.07 ppm, precluding any coordination involving the
imine nitrogen. These observations are in good agreement
with systems reported previously.[8f,10c,19a,20]
Results and Discussion
Synthesis and structural assessment: The Schiff-base ligand
LH ((E)-5-(hexyloxy)-2-{[2-(2-hydroxyethylamino)ethylimi-
no]methyl}phenol, abbreviated as 6ae) was obtained from
the condensation of a 4-alkoxy-substituted aldehyde with a
2-(2-aminoethylamino)ethanol by a slight modification of
the literature procedure.[19a] The complexes (Ln–6ae) were
prepared by the reaction of the ligand with the appropriate
metal nitrate in a 1:3 ratio of Ln/LH in ethanol/acetonitrile
at ambient temperature and obtained as cream-colored
solids in good yields. The elemental analyses revealed the
stoichiometry of the complexes to be consistent with the for-
Photophysical properties: The electronic spectra (Figure 1)
of the compounds were recorded in chloroform solution.
The ligand shows three bands in the region 285–390 nm. The
bands centered at around 285 and 309 nm are due to the p–
p* transition localized on the aromatic ring and that at
mula [Ln(LH)3ACHTUNGTRENNUNG(NO3)] (Scheme 1). The nCN peak at around
1625 cmꢀ1 observed for the ligand undergoes a hypsochro-
mic shift to around 1656 cmꢀ1 in all the complexes on ac-
count of zwitterion formation. Moreover, the appearance of
a weak broad band at about 3047 cmꢀ1 reflects the zwitter-
ionic (-C=N+H) nature of the ligand. The coordinating ni-
Figure 1. UV/Vis spectra of 6ae and Ln–6ae in CH2Cl2 (10ꢀ4 m solution).
around 390 nm is due to the p–p* transition of the imine
chromophore. Upon complexation, these bands are blue-
shifted to around 284, 307–313, and 347–376 nm. A photolu-
minescence study of the ligand (Figure 2) and its complexes
was carried out in the solid, solution, and mesomorphic
states. As the ligand is mesomorphic at room temperature,
the luminescent spectra were recorded in both the solid
state and in solution. In solution, the ligand shows one emis-
sion maximum at around 436 nm in solution, however, in
the solid state (mesomorphic), the emission maximum is
redshifted to around 446 nm. In the condensed state, the
larger intermolecular interaction gives rise to greater elec-
tronic delocalization resulting in a lowering in the energy of
the electronic states and hence the emission maximum is
redshifted. In general, Schiff-base systems exhibit flores-
cence due to intraACTHNUTRGNENGUliACHUTGTNRENNUG
gand p–p* transitions.[21] Surprisingly, the
complexes all exhibit similar emission maxima in the solu-
tion, solid, and mesomorphic states. The emission maxima
Scheme 1. Reagents and conditions: i) C6H13Br, KHCO3, KI, dry acetone,
D, 40 h; ii) glacial AcOH, absolute EtOH, D, 4 h; iii) LnACTHNUTRGNE(UNG NO3)3·6H2O,
acetonitrile, stirring, RT, 3 h.
13152
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13151 – 13159

A Tunable Emissive Lanthanidomesogen
FULL PAPER
Figure 2. Photoluminescence spectra of 6ae (lexc =350 nm) in solution
and in the solid state (mesophase).
Figure 4. Photoluminescence spectrum of Tb–6ae in the solid state (lexc
350 nm). Inset shows fluorescent image of Tb–6ae.
=
can be tuned by changing the metal ions. The samarium
(III)
435 nm (Figure 5) upon photoexcitation at around 350 nm.
These emissions occur from a predominantly ligand-based
1pp* excited state.[22d] The observed photoluminescence be-
havior closely resembles similar systems reported recen-
tly.[19a–c]
complex, [Sm(LH)3A(NO3)3], glows with a bright-orange light
CHTUNGTRENNUNG
both in the solid and solution states upon UV irradiation
(Figure 3). The emission spectrum exhibits three characteris-
tic transitions originating from the Sm3+ lowest emitting
Figure 3. Photoluminescence spectrum of Sm–6ae in the solid state (lexc
350 nm).
=
Figure 5. Photoluminescence spectra of La/Pr/Gd/Dy–6ae in solution
(lexc =350 nm).
4
6
6
state G5/2 to the H9/2 (644 nm, F=18%), H7/2 (603 nm),
Thermal properties and liquid-crystalline behavior: The
thermal properties of the ligand and its complexes were
studied by using polarizing optical microscopy (POM) and
differential scanning calorimetry (DSC). The ligand was
found to exhibit enantiotropic mesomorphism at room tem-
perature. The sample placed between two glass slides can be
easily sheared to show birefringent textures, which clearly
indicates that the compound is already in the liquid-crystal-
line state at room temperature. No melting/crystallization
peak was observed in the DSC thermogram (Table 1); the
ligand transforms directly into an isotropic liquid at 358C.
Upon cooling, first batonnets appear from the isotropic
melt, which coalesce to a fan-like texture (Figure 6) with
several homeotropic regions at 288C. The mesophase was
identified as a hexagonal columnar (Colh) phase through an
XRD study (see above). The ligand with a short C6 alkoxy
terminal chain is not a simple calamitic species, the presence
of the alcoholic OH group tends to induce attractive inter-
molecular interactions involving HO···HO hydrogen bonds,
resulting in liquid-crystalline behavior. The DSC thermo-
and H5/2 (565 nm) levels.[22,23] The ligand is excited to its sin-
6
glet state and through intersystem crossing transit to their
triplet state. The energies of the singlet and triplet states are
then intramolecularly transferred to the energy level of the
Sm3+ ion. Luminescence is observed during radiative deacti-
vation to the ground state. The Tb3+ complex, an intense
green emitter, shows characteristic emission bands (lex =
350 nm) centered at around 491, 548, 583, and 621 nm, re-
5
sulting from the deactivation of the D4 excited state to the
corresponding ground state FJ (J=6, 5, 4, 3) of the Tb3+ ion
7
(Figure 4). The most intense narrow emission band centered
at around 548 nm (F=16%) corresponds to the hypersensi-
tive metal-based transition 5D4! F5.[19b] The lanthanum
7
(3d104f0) complex in solution exhibits a rather broad and
strong green emission at around 542 nm caused by ligand-
to-metal charge transfer (LMCT) excited states not ob-
served for the other lanthanide complexes (3d104fn); the pra-
seodymium, gadolinium, and dysprosium complexes show
strong blue-light emission with maxima at around 420–
Chem. Eur. J. 2013, 19, 13151 – 13159
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13153

C. R. Bhattacharjee et al.
Table 1. DSC data for 6ae and its complexes.[a]
4.6 kJmolꢀ1) is due to the I!ColL phase transition.
A similar observation was also noted for all the
other complexes (Table 1). The mesophase to the
Compounds
Heating
Cooling
6ae
Colh 35.5 (6.1) I
I 28 (5.2) Colh
La–6ae
Pr–6ae
Sm–6ae
Gd–6ae
Tb–6ae
Dy–6ae
Cr 75.8 (34.9) ColL 120.9 (4.6) I
Cr 76.7 (35.6) ColL 121.3 (4.5) I
Cr 67.3 (33.2) ColL 118.8 (4.7) I
Cr 69.8 (35.6) ColL 116.7 (4.9) I
Cr 73.7 (28.7) ColL 113.9 (3.8) I
Cr 63.5 (24.3) ColL 117.9 (4.1) I
I 119.2 (4.6) ColL 45.6 (20.2) Cr clearing point transition temperature decreases
I 120.8 (4.4) ColL 44.9 (20.1) Cr
along the lanthanide series, which is in accord with
I 117.5 (4.5) ColL 43.6 (21.4) Cr
I 115.8 (4.7) ColL 41.2 (24.3) Cr
I 111.7 (3.5) ColL 38.7 (18.7) Cr
a recent observation on related lanthanide com-
plexes.[9a,19a] The reversibility of the thermal behav-
ior was established by DSC in subsequent heating/
cooling cycles. One-ring Schiff-base complexes of
lanthanides, irrespective of their stoichiometric
I 116.3 (3.5) ColL 35.6 (17.1) Cr
[a] Temperatures in 8C.
Figure 6. POM texture of 6ae.
Figure 7. POM texture of Sm–6ae.
gram of 6ae shows a broad peak at around 358C in the heat-
ing process and a peak at around 288C in the cooling proc-
ess. As the mesophase appears in both the heating and cool-
ing cycles the mesophase is enantiotropic. The peak at 288C
(DH=5.2 kJmolꢀ1) is due to an I!Colh phase transition.
Note that the mesophase-to-isotropic transition temperature
is higher for analogous Schiff-base compounds studied in
our earlier work than that observed in the present case.[19a]
This is quite unusual considering the fact that the pendant
alkoxy chain in 6ae contains only six carbon atoms com-
pared with the 18 carbon atoms in the alkoxy chain in the
previously reported compounds.[19a] The effect of a lateral
substituent on the melting point and the isotropic–mesomor-
phic transition temperature may also be significant. The re-
placement of the OH group of the aminoethanol part by the
-NHCH2CH2OH fragment in this case increases the width of
the molecule and presumably the intermolecular distance,
which may have led to a reduction in the lateral intermolec-
ular attractive force and consequent drastic depression of
the melting and clearing points.
The complexes exhibit enantiotropic mesomorphism and
a viscous waxy appearance before melting to an isotropic
liquid. Upon cooling, the complexes also show mosaic tex-
tures (Figure 7) reminiscent of a lamellar columnar (ColL)
mesophase, which tend to decompose on further heating
after reaching the isotropic temperature. By pressing with a
needle on the microscopic cover glass, it is possible to ob-
serve birefringence, although the molecules quickly reorient
to the homeotropic alignment. The DSC trace of a typical
complex, Sm–6ae, displays two transitions in both the heat-
ing and cooling cycles (Figure 8). The transitions are very
sharp and well defined. The peak at 117.58C (DH=
Figure 8. DSC thermogram of Sm–6ae.
type, invariably exhibit smectic mesomorphism.[8h] In this
regard, the present complexes are the first of their kind that
exhibit columnar mesomorphism.
X-ray diffraction study of the ligand (6ae) and its samarium
complex (Sm–6ae): Temperature-dependent, small-angle X-
ray diffraction experiments were carried out to identify un-
equivocally the nature of the mesophase. The diffraction
pattern (Table 2) for the ligand 6ae was obtained at 288C in
the mesophase (Figure 9). In the wide-angle region, a diffuse
intensity maximum centered at around 4.2 ꢁ is observed.
This is associated with the short-range liquid-like positional
ordering of the hydrocarbon chains within the layer plane.
In the low-angle region, sharp peaks observed correspond-
ing to d spacings of 47.7, 28.2, and 23.8 ꢁ in the ratio
1:0.59:0.5 suggest a columnar phase with 2D hexagonal or-
dering with a lattice dimension of 56.1 ꢁ.[24a] Pertinent here
13154
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13151 – 13159

A Tunable Emissive Lanthanidomesogen
FULL PAPER
Table 2. PXRD data for 6ae and Sm–6ae.
Compound
Mesophase
dobsd [ꢁ]
Miller
parameters[a]
N
indices[c]
6ae
Colh, 288C
a=56.11 ꢁ
S=2725.5 ꢁ2
Vm =511.8 ꢁ3
h=4.2
47.71 (47.73)
28.23 (28.24)
23.81 (23.83)
4.2
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
N=21
Sm–6ae
ColL, 1108C
d=37.61 ꢁ
V
37.50 (37.61)
18.76 (18.80)
12.93 (12.54)
11.25 (11.26)
8.6 (h/)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
M =2025 ꢁ3
ACHTUNGTRENNUNG
Figure 10. Molecular organization in the mesophase of 6ae. a) Cross-sec-
tion through a single column constructed by the self-assembly of the ta-
pered shape molecules. b) Arrangement of the columns in a hexagonal
lattice.
AHCTUNGTRENNUNG
7.71 (7.70)
4.3 (hch)
ACHTUNGTNER(NUNG 130)
[a] For the Colh mesophase, the lattice parameters are deduced from the
following mathematical expressions for the columnar phase: <d100 >=1/
1
2
2
=
2
by side in a radial conformation is presented in Figure 10.
This leads to tubular columns,[24b–f] generated by the stacking
of the discs, and the mutual organization of these columns
into a hexagonal lattice leads to the formation of the meso-
phase. This further explains the observed variation in the
peak intensity in Figure 9, reflecting a hole in the electronic
density distribution. The effective diameter of the columns
is assumed to match the experimentally observed lattice
constant (a=56.1 ꢁ). In this arrangement, the terminal ali-
phatic chains are rather disorganized, which confine the
rigid cores by forming a liquid matrix-like structure around
them. Considering a density close to 1 gcmꢀ3 and a periodic
stacking of the molecular cores within a column of 4.2 ꢁ,
there are approximately 21 molecules per unit cell (N=hS/
Vm). In a hexagonal lattice, there is one column per unit
cell. The large number of molecules (N=21) in the cross-
section of the columns is probably due to the small taper
angle with a minimum space requirement of the peripheral
alkoxy chains, whereas the hydrogen-bonding fragment is
tightly packed in the middle of the column cores. Although
such a large number of molecules per column is quite un-
common, it is not unprecedented.[24g] The observed stacking
distance within a column (h=4.2 ꢁ) is greater than that ex-
pected (3.5 ꢁ) for p–p stacking with a “face-to-face” orien-
tation of the aromatic cores. This is accounted for by invok-
ing “edge-to-edge” stacking of the molecules in the col-
umn.[24h] Therefore that the tapered rod-like molecular
motifs may also lead to the supramolecular columnar liquid-
crystalline assembly.
NhkACHTUNGTRENNUNG[ꢀdhkACHTUNGTRENNUNG(h +k +hk) ], in which Nhk is the number of hk reflections, and
p
a=2<d100 >/ 3. The molecular volume, Vm, is calculated by using the
formula Vm =M/l1NA, in which M is the molecular weight of the com-
pound, NA is Avogadroꢂs number, 1 is the volume mass (ꢁ1 gcmꢀ3), l(T)
is a temperature correction coefficient at the temperature of the experi-
ment (T). The intracolumnar repeating distance h is calculated directly
from the estimated molecular volume Vm according to the equation h=
NVm/S, in which N is the number of molecules and S is the lattice area
p
(columnar cross-section). For a hexagonal lattice S=a2 3= . For the ColL
2
phase, d=ꢀdl00/Nl00, in which Nl00 is the number of l00 reflections.
[b] dobsd and dcalcd are the experimentally measured and theoretical dif-
fraction spacings, respectively. [c] Miller indices (hkl) of the reflections
of the Colh and ColL phases.
Figure 9. XRD profile of 6ae.
is to mention that in addition to planar disc-like molecules,
many other molecular shapes may also give rise to a colum-
nar-type of organization.[24b–h] The lattice constant (a=
56.1 ꢁ) is much larger than the monomeric molecular length
of 28.04 ꢁ for a fully extended molecule, as calculated from
a DFT study. The following model (Figure 10) could be de-
duced for the organization of the tapered molecules of the
ligand 6ae with nonequivalent ends in the columnar meso-
phase. The aliphatic tails diverge towards the periphery of
the column, whereas the polar and hydrogen-bonding moiet-
ies (OH groups) of the molecule reside near the center, sur-
rounded by an aromatic crown. The construction of the disc
resulting from the stacking of 21 tapered units of 6ae side
For the complex Sm–6ae, three peaks (Figure 11) were
observed in the small-angle region, one strong peak and two
weak peaks corresponding to the Miller indices (100), (200),
and (300) with a d-spacing ratio of 1:2:3, respectively.[25a]
The presence of these equidistant reflections shows that the
molecules are arranged in regularly spaced layers
(Figure 12) with a layer distance of 37.61 ꢁ. Two other less
intense but relatively sharp reflections were assigned to
(120) and (130) reflections, which indicate 2D columnar or-
dering of the mesophase. The presence of broad halos in the
wide-angle region at 4.3 (hch) and 8.6 ꢁ confirm the fluid
Chem. Eur. J. 2013, 19, 13151 – 13159
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13155

C. R. Bhattacharjee et al.
DFT study of Gd–6ae: As single crystals suitable for X-ray
analysis could not be grown, DFT studies were undertaken
to ascertain the optimized geometry of the Gd–6ae complex.
The ground-state geometries of the Gd–6ae complex in the
gas phase were fully optimized by using the unrestricted
BLYP/DNP methods without imposing any symmetry con-
straints. The BLYP functional, used throughout this study,
comprises a hybrid exchange functional as defined by Becke
and the nonlocal Lee–Yang–Parr correlation functional.[26c]
The basis set chosen was DNP, double-numerical atomic or-
bitals augmented by polarization functions.[26a–d] Relativistic
effects were taken into account by using an all-electron
scalar relativistic method based on the Douglas–Kroll–Hess
(DKH) transformation.[26a–d] All calculations were per-
formed with the DMol3 program package[26d]. All three ni-
trato groups coordinate to the gadolinium ion in a bidentate
fashion. With the phenolic proton transferred to the imine
nitrogen, the phenolate oxygen binds the gadolinium ion in
a monodentate fashion (Figure 13).With three monodentate
Figure 11. XRD profile of Sm–6ae.
nature of the mesophase; the former corresponds to the
molten chains in liquid-like order, whereas the latter is ascri-
bed to double periodicity. The peak centered at 20.858
(4.3 ꢁ) is much wider, extending to around 2q=358, than
that expected for an archetypical disordered mesophase.
Figure 13. Optimized structure of Gd–6ae.
Figure 12. a) Lanthanide complex containing three Schiff-base ligands
bearing a C6 alkoxy chain. b) Organization of molecules in the ColL
phase.
O-donor Schiff-base ligands and as many chelated bidentate
nitrato groups, the gadolinium ion achieves a nine-coordi-
nate geometry quite typical of lanthanides. Two of the three
imine protons form double hydrogen bonds with the pheno-
late oxygen and with an oxygen atom of a nitrato group,
whereas the third proton forms two hydrogen bonds with
two nitrato oxygen atoms and one with a phenolic oxygen
atom of a ligand. The HOMO and LUMO energies of the
complex Gd–6ae were calculated to be ꢀ4.947 and
ꢀ2.668 eV, respectively (DE=2.279 eV). The HOMO–
LUMO energy gap is a measure of the kinetic stability of a
molecule and could indicate its reactivity pattern. A large
HOMO–LUMO gap implies high kinetic stability and low
chemical reactivity because it is energetically unfavorable to
add electrons to a high-lying LUMO or to extract electrons
from a low-lying HOMO. The high HOMO–LUMO energy
The XRD analysis therefore reveals that the observed meso-
phase may more appropriately be branded as a lamellar
phase with short-range columnar order within the layers
(ColL).[25b,c] As such, the phase is more akin to a smectic-
type phase. The cross-sectional area (A=2VM/d) deduced
from the molecular volume (VM =2025 ꢁ3) and the layer
thickness (d=37.61 ꢁ) is around 108 ꢁ2. Considering a total
of three alkoxy chains, a cross-sectional area of 36 ꢁ2 (A/3)
per mesogenic unit is obtained. The ColL mesophase can be
imagined to form smectic layers made of broken lamellae
with some interdigitation of the peripheral alkoxy chains in
the layer molecules (Figure 12).
13156
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13151 – 13159

A Tunable Emissive Lanthanidomesogen
FULL PAPER
mined by using quinine bisulfate in 0.1n H2SO4) as standard. Quantum
chemical calculations were carried out on 6ae and Gd–6ae by using den-
sity functional theory (DFT) as implemented in the DMol3 package.[26d]
gap of 2.279 eV in the present case suggests the complex to
ꢀ
be quite stable. The calculated average Gd O (nitrato) and
ꢀ
Gd O (phenolic) bond distances in the Gd–6ae complex are
Materials: All solvents were purified and dried following standard proce-
dures. The materials were procured from Tokyo Kasei and Lancaster
Chemicals. Silica (60–120 mesh) from Spectrochem was used for chroma-
tographic separation. Silica gel G (E-Merck, India) was used for TLC.
ꢀ
2.578 and 2.410 ꢁ, respectively, and the bond angles O1
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Gd O2, O2 Gd O3, and O1 Gd O3 are 88.3, 83.2, and
160.58, respectively. Mutually perpendicular to each other,
the phenyl rings of the three Schiff-base ligands with the
short hexyloxy tail are located as far as possible from each
other in the three-dimensional space.
Synthesis and analysis
4-(Hexyloxy)salicyladehyde: 4-Alkoxysalicyldehyde derivatives were pre-
pared following the general method reported in the literature.[3] 2,4-Dihy-
droxybenzaldehyde (10 cm3,1.38 g), KHCO3 (10 cm3,1 g), KI (catalytic
amount), and 1-bromohexane (10 mmol, 1.6 g) were mixed in dry acetone
(250 cm3). The mixture was heated under reflux for 40 h and then fil-
tered, while hot, to remove any insoluble solids. Dilute HCl was added to
neutralize the warm solution, which was then extracted with chloroform
(100 cm3). The combined chloroform extract was concentrated to give a
purple solid, which was purified by column chromatography using a mix-
ture of chloroform and hexane (1:1, v/v) as eluent. Evaporation of the
solvents afforded a white solid product.
Conclusion
A new series of emissive lanthanidomesogens, [Ln(LH)3-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
have been successfully synthesized. The ligand and com-
plexes are both liquid crystalline and photoluminescent. The
ligand with a short C6 alkoxy tail showed hexagonal colum-
nar mesomorphism at room temperature. The complexes
were found to be thermally very stable. The Schiff-base
ligand exists as a zwitterion in the complexes, binding to the
metal in a monodentate fashion through the phenolate
oxygen and the nitrato groups chelating to the metal to
complete the nine coordination around the lanthanide ion.
Although one-ring Schiff-base complexes of lanthanides, re-
gardless of their stoichiometries, are known to exhibit smec-
tic mesomorphism,[19a] the newly reported complexes exhib-
iting lamello-columnar mesomorphism are the first of their
(E)-5-(Hexyloxy)-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol
(6ae): An ethanolic solution of 2-hydroxy-4-(hexyloxy)salicylaldehyde
(0.22 g, 1 mmol) was added to an ethanolic solution of 2-(2-aminoethyl-
AHCTUNGERTGaNNUN mino)ethanol (0.10 g, 1 mmol) The mixture was heated at reflux with a
few drops of acetic acid as catalyst for 3 h to yield the yellow Schiff base.
The compound was collected by filtration and recrystallized from abso-
lute ethanol to obtain a pure compound. Yield: 0.245 g, 75%; yellow
solid; 1H NMR (400 MHz, CDCl3): d=1.3 (t, J=8 Hz, 3H; CH3), 1.46–
1.74 (m, CH2 of in side-chain), 3.61 (t, J=4.0 Hz, 2H; CH2N=C), 3.70 (t,
J=4.0 Hz, 2H; CH2OH), 3.84 (t, J=8 Hz, 2H; OCH2), 7.09 (d, J=
8.3 Hz, 1H; C6H4), 8.11 (s, 1H; N=CH), 13.14 ppm (s, 1H, OH);
13C NMR (75.45 MHz, CDCl3, Me4Si at 258C): d=161.3 (C-1), 102.3 (C-
2), 107.4 (C-3), 161.6 (C-4), 131.3 (C-5), 116.7 (C-6), 160.8 (C-7), 55.4 (C-
8), 68.4 (OCH2), 50.5 (C-9), 52.0 (C-10), 61.5 (C-11) ppm; IR (KBr): n˜ =
ꢀ
ꢀ
ꢀ
3457 (nOH), 2924 (nasC H, CH3), 2922 (nasC H, CH2), 2871 (nsC H,
ꢀ1
ꢀ
ꢀ
CH3), 2849 (nasC H, CH2), 1625 (nC=N), 1297 cm (nC O); MS (FAB):
m/z: calcd for C17H28N2O3 308.2; found: 309 [M+H]+; elemental analysis
calcd (%) for C17H28N2O3 (308.2): C 66.2, H 9.1, N 9.0; found: C 66.1, H
9.2, N 9.1.
kind. The samariumACTHNUTRGNEUNG(III) complex shows ligand-sensitized
bright-orange emission on excitation at 350 nm with a high
quantum yield of around 18%, whereas the other complexes
are blue or green emitters. The complexes are anticipated to
serve as promising candidates for multifunctional device ap-
plications.
Synthesis of the lanthanideACHUTGTNRENNUG(III) complexes [Ln(LH)3ACHTUNTGRENN(GUN NO3)3] (LH=6ae):
A solution of Ln(NO3)3·6H20 [Ln=La (1 mmol, 0.43 g), Pr (1 mmol,
AHCTUNGTRENNUNG
0.43 g), Sm (1 mmol, 0.44 g), Gd (1 mmol, 0.51 g), Tb (1 mmol, 0.43 g),
Dy (1 mmol, 0.45 g)] in a minimum volume of acetonitrile was added
dropwise to an ethanolic solution of ligand 6ae (3 mmol, 0.92 g) at room
temperature. The reaction mixture was stirred for 3 h and the cream-col-
ored solid that formed was filtered and washed with absolute ethanol and
dried in vacuo.
Experimental Section
[La(LH)3ACHTNURTGENUNG(NO3)3] (La–6ae): Yield: 1 g, (78%); cream-colored solid;
Physical measurements: The C, H, and N analyses were carried out on a
PE2400 elemental analyzer. NMR spectra were recorded on a Bruker
DPX 400 MHz spectrometer in CDCl3 (chemical shifts in ppm) with
TMS as internal standard. The UV/Vis absorption spectra of the com-
pounds in CHCl3 were recorded on a Shimadzu UV-160PC spectropho-
tometer. IR spectra were recorded on a Perkin–Elmer L 120–000A spec-
trometer in KBr discs. The mass spectra were recorded on a JEOL SX-
102 FAB mass spectrometer. Magnetic susceptibility measurements were
made at room temperature on a Cahn-Faraday balance. The optical tex-
tures of the different phases of the compounds were studied by using a
polarizing microscope (Nikon optiphot-2-pol) attached to an Instec hot
and cold stage HCS302 microscope with an STC200 temperature control-
ler with an accuracy of 0.18C. The thermal behavior of the compounds
was studied by using a Perkin–Elmer Pyris-1 differential scanning calo-
rimeter (DSC) at heating and cooling rates of 58Cminꢀ1. X-ray measure-
ments were carried out by using samples filled in Lindemann capillaries.
The apparatus essentially involved a PANalytical XꢂPert PRO MP X-ray
diffractometer consisting of a focussing elliptical mirror and a fast high-
resolution detector. The wavelength of the radiation employed is
0.15418 nm. Photoluminescence spectra were recorded on a Shimadzu
RF-53D1 PC instrument. The fluorescence quantum yields were deter-
1H NMR (400 MHz, CDCl3): d=1.3(t, J=6.9 Hz, 9H; 3 CH3), 1.45–1.78
(m, 3 CH2 of side-chain), 6.64 (d, J=8.8 Hz, 3H; 3 C6H4), 7.61 (d, J=
12 Hz, 3H; 3 CH=N), 12.31 (br, s, 3 N+H), 3.70 ppm (t, J=4.0 Hz, 6H; 3
ꢀ
CH2OH); IR (KBr): n˜ =3317 (nOH, CH2OH), 1241 (nC O, ether), 1655
(nC=N), 1475 (n4NO3), 1290 (n1NO3), 1135 (n2NO3), 855 cmꢀ1 (n6NO3);
MS (FAB): m/z calcd for LaC48H78N9O18 1207.4; found: 1208 [M+H]+;
elemental analysis calcd (%) for LaC48H78N9O18 (1207.4): C 47.7, H 6.5,
N 10.4; found: C 47.7, H 6.4, N 10.5.
[Pr(LH)3ACTHNUGTRNE(UNG NO3)3] (Pr–6ae):Yield: 1.18 g, (76%); cream-colored solid; IR
ꢀ
(KBr): n˜ =3314 (nOH, CH2OH), 1240 (nC O, ether), 1658 (nC=N), 1474
(n4NO3), 1289 (n1NO3), 1132 (n2NO3), 850 cmꢀ1 (n6NO3); MS (FAB): m/z:
calcd for PrC48H78N9O18 1209.4; found: 1210 [M+H]+; elemental analysis
calcd (%) for PrC48H78N9O18 (1209.4): C 47.6, H 6.5, N 10.4; found: C
47.5, H 6.6, N 10.4.
[Sm(LH)3ACHTNURTGENUNG(NO3)3] (Sm–6ae): Yield: 1 g, (76%); cream-colored solid; IR
ꢀ
(KBr): n˜ =3310 (nOH, CH2OH), 1235 (nC O, ether), 1659 (nC=N), 1473
(n4NO3), 1288 (n1NO3), 1133 (n2NO3), 851 cmꢀ1 (n6NO3); MS (FAB): m/z:
calcd for SmC48H78N9O18 1220.4; found: 1221 [M+H]+; elemental analy-
sis calcd (%) for SmC48H78N9O18 (1220.4): C 47.2, H 6.4, N 10.3; found: C
47.1, H 6.4, N 10.2.
Chem. Eur. J. 2013, 19, 13151 – 13159
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13157

C. R. Bhattacharjee et al.
[Gd(LH)
G
Soc. 2000, 122, 4335–4344; d) V. S. Mironov, Y. G. Galyametdinov,
A. Ceulemans, K. Binnemans, J. Chem. Phys. 2000, 113, 10293–
10303; e) K. Lodewyckx, R. Van Deun, K. Binnemans, Mater. Sci.
Eng. C 2001, 18, 217–221; f) R. Van Deun, K. Binnemans, Mater.
Sci. Eng. C 2001, 18, 211–215; g) K. Binnemans, R. Van Deun, C.
Gçrller-Walrand, W. Haase, D. W. Bruce, L. V. Malykhina, Y. G. Ga-
lyametdinov, Mater. Sci. Eng. C 2001, 18, 247–254; h) K. Binnemans,
C. Gorller-Walrand, Chem. Rev. 2002, 102, 2303–2345.
(KBr): n˜ =3314 (nOH, CH2OH), 1241 (nC O, ether), 1651 (nC=N), 1471
(n4NO3), 1281 (n1NO3), 1129 (n2NO3), 853 cmꢀ1 (n6NO3); MS (FAB): m/z:
calcd for GdC48H78N9O18 1226.4; found: 1227 [M+H]+; elemental analy-
sis calcd (%) for GdC48H78N9O18 (1226.4): C 47.0, H 6.4, N 10.2; found: C
47.1, H 6.3, N 10.2.
[Tb(LH)3ACHTUNGTRENNUNG(NO3)3] (Tb–6ae): Yield: 1.0 g, (76%); cream-colored solid; IR
(KBr): n˜ =3319 (nOH, CH2OH), 1245 (nC O, ether), 1653 (nC=N), 1473
(n4NO3), 1283 (n1NO3), 1127 (n2NO3), 851 cmꢀ1 (n6NO3); MS (FAB): m/z:
calcd for TbC57H105N9O18 1363.6; found: 1364 [M+H]+; elemental analy-
sis calcd (%) for TbC57H105N9O18 (1363.6): C 50.2, H 7.7, N 9.2; found: C
50.1, H 7.5, N 9.3.
[9] a) A. A. Knyazev, Y. G. Galyametdinov, B. Goderis, K. Driesen, K.
Goossens, C. Gorller-Walrand, K. Binnemans, T. Cardinaels, Eur. J.
Inorg. Chem. 2008, 756–761; b) S. Tang, A. Babai, A.-V. Mudring,
Angew. Chem. 2008, 120, 7743–7746; Angew. Chem. Int. Ed. 2008,
47, 7631–7634.
[Dy(LH)3ACHTUNGTRENNUNG(NO3)3] (Dy-6ae): Yield: 1.0 g, (75%); cream-colored solid; IR
[10] a) S. Suꢄrez, O. Mamula, R. Scopelliti, B. Donnio, D. Guillon, E.
Terazzi, C. Piguet, J. C. G. Bꢅnzli, New J. Chem. 2005, 29, 1323–
1334; b) E. Terazzi, S. Suarez, S. Torelli, H. Nozary, D. Imbert, O.
Mamula, J. P. Rivera, E. Guillet, J. M. Benech, G. Bernardinelli, R.
Scopelliti, B. Donnio, D. Guillon, J. C. G. Bꢅnzli, C. Piguet, Adv.
Funct. Mater. 2006, 16, 157–168; c) S. Kumari, A. K. Shingh, K. R.
Kumar, B. Sridhar, T. R. Rao, Inorg. Chim. Acta 2009, 362, 4205–
4211; d) C. Piguet, J. Claude, G. Bunzli, B. Donnio, D. Guillon,
Chem. Commun. 2006, 3755–3768; e) S. Kumari, A. K. Singh, T. R.
Rao, Mater. Sci. Eng. C 2009, 29, 2454–2458; f) C. V. Yelamaggad,
R. Prabhu, G. Shanker, D. W. Bruce, Liq. Cryst. 2009, 36, 247–255;
g) V. I. Dzhabarov, A. A. Knyazev, M. V. Strelkov, E. Yu. Molosto-
va, V. A. Schustov, W. Haase, Y. G. Galyametdinov, Liq. Cryst. 2010,
37, 285–291; h) A. Escande, L. Guenee, E. Terazzi, T. B. Jensen, H.
Nozary, C. Piguet, Eur. J. Inorg. Chem. 2010, 2746–2759; i) T. B.
Jensen, E. Terazzi, K.-L. Buchwalder, L. Guenee, H. Nozary, K.
Schenk, B. Heinrich, B. Donnio, D. Guillon, C. Piguet, Inorg. Chem.
2010, 49, 8601–8619; j) T. B. Jensen, E. Terazzi, B. Donnio, D. Guil-
lon, C. Piguet, Chem. Commun. 2008, 181–183.
[11] Yu. G. Galyametdinov, G. I. Ivanova, I. V. Ovchinnikov, Bull. Acad.
Sci. USSR Div. Chem. Sci. (Engl. Transl.) 1991, 40, 1109–1116.
[12] a) K. Binnemans, K. Lodewyckx, Angew. Chem. 2001, 113, 248–250;
Angew. Chem. Int. Ed. 2001, 40, 242–244; b) R. Van Deun, K. Bin-
nemans, Liq. Cryst. 2001, 28, 621–627; c) K. Binnemans, K. Lode-
wyckx, B. Donnio, D. Guillon, Chem. Eur. J. 2002, 8, 1101–1105;
d) M. Marcos, A. Omenat, J. Barbera, F. Duran, J. L. Serrano, J.
Mater. Chem. 2004, 14, 3321–3327; e) K. Binnemans, K. Lodewyckx,
T. Cardinaels, T. N. P. Vogt, C. Bourgogne, D. Guillon, B. Donnio,
Eur. J. Inorg. Chem. 2006, 150–157; f) Y. T. Yang, K. Driesen, P.
Nockemann, K. Van Hecke, L. Van Meervelt, K. Binnemans, Chem.
Mater. 2006, 18, 3698–3704.
ꢀ
(KBr): n˜ =3321 (nOH, CH2OH), 1248 (nC O, ether), 1658 (nC=N), 1475
(n4NO3), 1282 (n1NO3), 1125 (n2NO3), 856 cmꢀ1 (n6NO3); MS (FAB): m/z:
calcd for DyC57H105N9O18 1367.6; found: 1368 [M+H+]; elemental analy-
sis calcd (%) for DyC57H105N9O18 (1367.6): C 50.0, H 7.7, N 9.2; found: C
50.2, H 7.5, N 9.2%.
Acknowledgements
The authors thank the Sophisticated Analytical Instrument Facility,
North-Eastern Hill University (SAIF, NEHU) and the Central Drug Re-
search Institute (CDRI) for analytical and spectral data. H.A.R.P. is
thankful to the Council of Scientific and Industrial Research (New Delhi)
for a research fellowship (No. 09/747ACTHNUTRGNEUNG(0006)/2011-EMR-I).
[1] a) R. J. Bushby, O. R. Lozman, Curr. Opin. Colloid Interface Sci.
2002, 7, 343–354; b) M. OꢂNeill, S. M. Kelly, Adv. Mater. 2003, 15,
1135–1146; c) J. Hanna, Opto-Electron. Rev. 2005, 13, 259–267.
[2] a) R. Bayꢃn, S. Coco, P. Espinet, Chem. Eur. J. 2005, 11, 1079–1085;
b) V. N. Kozhevnikov, B. Donnio, D. W. Bruce, Angew. Chem. 2008,
120, 6382–6385; Angew. Chem. Int. Ed. 2008, 47, 6286–6289; c) A.
Santoro, A. C. Whitwood, J. A. G. Williams, V. N. Kozhevnikov,
D. W. Bruce, Chem. Mater. 2009, 21, 3871–3882.
[3] C. Weder, C. Sarwa, C. Bastiaansen, P. Smith, Adv. Mater. 1997, 9,
1035–1039.
[4] Y. G. Galyametdinov, A. A. Knyazev, V. I. Dzhabarov, T. Cardinaels,
K. Driesen, C. Gorller-Walrand, K. Binnemans, Adv. Mater. 2008,
20, 252–257.
[5] D. W. Bruce, R. Deschenaux, B. Donnio, D. Guillon in Comprehen-
sive Organometallic Chemistry III, Volume 12 (Eds.: D. M. P.
Mingos, R. H.Crabtree, D. OꢂHare), Elsevier, Oxford, 2007, 195.
[6] a) K. Binnemans, J. Mater. Chem. 2009, 19, 448–453; b) Y. Wang, Y.
Liu, H. Qi, X. Li, M. Nin, M. Liu, D. Shi, W. Zhu, Y. Cao, Dalton
Trans. 2011, 40, 5046–5051.
[7] a) A. M. Giroud-Godquin, P. M. Maitlis, Angew. Chem. 1991, 103,
370–398; Angew. Chem. Int. Ed. Engl. 1991, 30, 375–402; b) P. Espi-
net, M. A. Esteruelas, L. A. Oro, J. L. Serrano, E. Sola, Coord.
Chem. Rev. 1992, 117, 215–274; c) S. A. Hudson, P. M. Maitlis,
Chem. Rev. 1993, 93, 861–885; d) D. W. Bruce, J. Chem. Soc. Dalton
Trans. 1993, 2983–2989; e) A. P. Polishchuk, T. V. Timofeeva, Russi-
an Chem. Rev. 1993, 62, 291–321; f) J. L. Serrano, Metallomesogens,
Synthesis Properties and Applications, Wiley-VCH, Weinheim, 1996;
g) A. M. Giroud-Godquin, Coord. Chem. Rev. 1998, 178–180, 1485–
1499; h) B. Donnio, D. W. Bruce, Struct. Bonding (Berlin) 1999, 95,
193–247.
[8] a) Yu. G. Galyametdinov, G. I. Ivanova, A. V. Prosvirin, O. Kadkin,
Russ. Chem. Bull. 1994, 43, 938–940; b) Y. G. Galyametdinov, M. A.
Athanassopoulou, K. Griesar, O. Kharitonova, E. A. Soto, W. Busta-
mante, L. Tinchurina, I. Ovchinnikov, W. Haase, Chem. Mater. 1996,
8, 922–926; c) K. Binnemans, Y. G. Galyametdinov, R. Van Deun,
D. W. Bruce, S. R. Collinson, A. P. Polishchuk, I. Bikchantaev, W.
Haase, A. V. Prosvirin, L. Tinchurina, I. Litvinov, A. Gubajdullin,
A. Rakhmatullin, K. Uytterhoeven, L. Van Meervelt, J. Am. Chem.
[13] a) H. Miwa, N. Kobayashi, K. Z. Ban, K. Ohta, Bull. Chem. Soc.
Jpn. 1999, 72, 2719–2728; b) J. Z. Li, H. Xin, M. Li, Liq. Cryst.
2006, 33, 913–919.
[14] a) C. Piechocki, J. Simon, J. J. Andrꢆ, D. Guillon, P. Petit, A. Skou-
lios, P. Weber, Chem. Phys. Lett. 1985, 122, 124–128; b) J. Sleven, C.
Gçrller-Walrand, K. Binnemans, Mater. Sci. Eng. C 2001, 18, 229–
238; c) F. Maeda, K. Hatsusaka, K. Ohta, M. Kimura, J. Mater.
Chem. 2003, 13, 243; d) K. Binnemans, J. Sleven, S. De Feyter, F. C.
De Schryver, B. Donnio, D. Guillon, Chem. Mater. 2003, 15, 3930–
3938; e) A. G. Gꢅrek, T. Basova, D. Luneau, C. Lebrun, E. Kol’tsov,
A. K. Hassan, V. Ahsen, Inorg. Chem. 2006, 45, 1667–1676.
[15] I. Bikchantaev, Y. G. Galyametdinov, O. Kharitonova, I. V. Ovchin-
nikov, D. W. Bruce, D. A. Dunmur, D. Guillon, B. Heinrich, Liq.
Cryst. 1996, 20, 489–492.
[16] T. Cardinaels, K. Driesen, T. N. Pa rac-Vogt, B. Heinrich, C. Bour-
gogne, D. Guillon, B. Donnio, K. Binnemans, Chem. Mater. 2005, 17,
6589–6598.
[17] Y. G. Galyametdinov, L. V. Malykhina, W. Haase, K. Driesen, K.
Binnemans, Liq. Cryst. 2002, 29, 1581–1584.
[18] a) K. Binnemans, B. Gundogan, J. Rare Earths. 2002, 20, 249–255;
b) S. Suꢄrez, O. Mamula, D. Imbert, C. Piguet, J. C. G. Bꢅnzli,
Chem. Commun. 2003, 1226–1227.
[19] a) C. R. Bhattacharjee, G. Das, P. Goswami, P. Mondal, S. K. Prasad,
D. S. S. Rao, Polyhedron 2011, 30, 1040–1047; b) M. Pietraszkiewicz,
13158
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13151 – 13159

A Tunable Emissive Lanthanidomesogen
FULL PAPER
S. Mal, O. Pietraszkiewicz, Opt. Mater. 2012, 34, 1507–1512; c) L.
Guo, G. Hu, W. Li, S. Zhang, SJFCD. 2012, 2, 48–52.
[20] B. Keshavan, P. G. Chandrashekara, N. M. Made Gowda, J. Mol.
Struct. 2000, 553, 193–19.
Ungarb, S. V. Battyb, J. Chem. Soc. Perkin Trans. 1 1993, 1411–
1420; f) V. Percec, D. Tomazos, J. Heck, H. Blackwell, Goran Ungar,
J. Chem. Soc. Perkin Trans. 2 1994, 31–44; g) X. Cheng, F. Su, R.
Huang, H. Gao, M. Prehm, C. Tschierske, Soft Matter 2012, 8, 2274–
2285; h) T. Shimogaki, S. Dei, K. Ohta, A. Matsumoto, J. Mater.
Chem. 2011, 21, 10730–10737.
[21] T. Chattopadhyay, M. Mukherjee, K. S. Banu, A. Banerjee, E.
Suresh, E. Zangrando, D. Das, J. Coord. Chem. 2009, 62, 967–979.
[22] a) B. L. An, M.-L. Gong, M.-X. Li, J.-M. Zhang, J. Mol. Struct. 2004,
687, 1–6; b) M. D. Regulacio, M. H. Pablico, J. A. Vasquez, P. N.
Myers, S. Gentry, M. Prushan, S.-.W. T. Chang, S. L. Stoll, Inorg.
Chem. 2008, 47, 1512–1523.
[23] J. A. Fernandes, R. A. S. Ferreira, M. Pillinger, L. D. Carlos, I. S.
GonÅalves, P. J. A. R.- Claro, Eur. J. Inorg. Chem. 2004, 3913–3919.
[24] a) G. Barberio, A. Bellusci, A. Crispini, M. Ghedini, A. Golemme,
P. Prus, D. Pucci, Eur. J. Inorg. Chem. 2005, 181–188; b) G. Johans-
son, V. Percec, G. Ungar, D. Abramic, J. Chem. Soc. Perkin Trans. 1
1994, 447–459; c) R. M. Richardson, S. A. Ponomarenko, N. I.
Boiko, V. P. Shibaev, Liq. Crys. 1999, 26, 101–108; d) M. Marcos, R.
Gimꢆnez, J. L. Serrano, B. Donnio, B. Heinrich, D. Guillon, Chem.
Eur. J. 2001, 7, 1006–1013; e) V. Percec, G. Johansson, J. Heck, G.
[25] a) D. Pucci, I. Aiello, A. Bellusci, A. Crispini, I. D. Franco, M. Ghe-
dini, M. La Deda, Chem. Commun. 2008, 2254–2256; b) E. Terazzi,
S. Torelli, G. Bernardinelli, J.-P. Rivera, J-M. Bꢆnech, C. Bourgogne,
B. Donnio, D. Guillon, D. Imbert, J.-C. G. Bꢅnzli, A. Pinto, D. Jean-
nerat, C. Piguet, J. Am. Chem. Soc. 2005, 127, 888–903; c) M. Ste˛-
´
pien, B. Donnio, J. L. Sessler, Chem. Eur. J. 2007, 13, 6853–6863.
[26] a) M. Douglas, N. M. Kroll, Ann. Phys. 1974, 82, 89–155; b) D. D.
Koelling, B. N. Harmon, J. Phys. C 1977, 10, 3107–3114; c) C. Lee,
W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789; d) B. Delley, J.
Chem. Phys. 1990, 92, 508–517.
Received: May 1, 2013
Revised: June 23, 2013
Published online: August 12, 2013
Chem. Eur. J. 2013, 19, 13151 – 13159
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13159