Liquid crystal behavior induced in highly luminescent unsymmetrical borondifluoride β-diketonate materials

Article abstract of DOI:10.1016/j.ica.2011.06.014

Highly luminescent and liquid crystal materials were successfully prepared by the strategic introduction of unsymmetrically alkyloxyphenyl substituted β-diketones, as ligands towards the BF₂ group. So, four families of ligands and their boron derivatives were prepared, each of them containing invariable the alkyl chain at one of the substituents in the 1(3) position, with 12, 14, 16 or 18 carbon atoms, while for the other substituent at the 3(1) position, the number of alkyl carbon atoms was increased from 4 to 18. In this way, the influence of factors as asymmetry or molecular length was evaluated towards the liquid crystal behavior of the compounds. The photophysical characterization of the boron derivatives was also carried out, showing in all cases a high fluorescent emission in the blue-violet region in solution and in the green region in the solid state, with quantum yields near the unity. In addition, thermal studies by DSC, as well as the analysis by POM and XRD were determinant to characterize the compounds as liquid crystal materials, exhibiting B₁ mesophases, in agreement with the banana molecular shape. In contrast the corresponding β-diketone precursors behave again as liquid crystals showing SmC and N mesophases.

Full text of DOI:10.1016/j.ica.2011.06.014

Inorganica Chimica Acta 381 (2012) 124–136
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Liquid crystal behavior induced in highly luminescent unsymmetrical
borondifluoride b-diketonate materials
b
Ignacio Sánchez a, José Antonio Campo a, José Vicente Heras a, Mercedes Cano a, , Elisabete Oliveira
⇑
a Department of Inorganic Chemistry I, Faculty of Chemistry, Universidad Complutense de Madrid, 28040 Madrid, Spain
b BIOSCOPE Group, Faculty of Science, Physical-Chemistry Department, Ourense Campus, University of Vigo, 32004 Ourense, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 21 June 2011
Highly luminescent and liquid crystal materials were successfully prepared by the strategic introduction
of unsymmetrically alkyloxyphenyl substituted b-diketones, as ligands towards the BF2 group. So, four
families of ligands and their boron derivatives were prepared, each of them containing invariable the
alkyl chain at one of the substituents in the 1(3) position, with 12, 14, 16 or 18 carbon atoms, while
for the other substituent at the 3(1) position, the number of alkyl carbon atoms was increased from 4
to 18. In this way, the influence of factors as asymmetry or molecular length was evaluated towards
the liquid crystal behavior of the compounds.
Fluorescence Spectroscopy: from Single
Chemosensors to Nanoparticles Science –
Special Issue
Keywords:
The photophysical characterization of the boron derivatives was also carried out, showing in all cases a
high fluorescent emission in the blue–violet region in solution and in the green region in the solid state,
with quantum yields near the unity. In addition, thermal studies by DSC, as well as the analysis by POM
and XRD were determinant to characterize the compounds as liquid crystal materials, exhibiting B1 mes-
ophases, in agreement with the banana molecular shape. In contrast the corresponding b-diketone pre-
cursors behave again as liquid crystals showing SmC and N mesophases.
Highly luminescent materials
Borondifluoride
b-Diketonate ligands
Bent-core mesophases
Liquid crystals
Bifunctional materials
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
based on two photon excitation [6]. Borondifluoride b-diketonates
containing aromatic moieties in the chelating ring have been sug-
Luminescent liquid crystal materials have attracted consider-
able attention over past decades by their ability to be used in dis-
plays, OLEDs and, in general, in devices for new technologies [1–5].
In particular, to combine liquid crystal and luminescent proper-
ties in the same material leading to intrinsically luminescent mes-
ogens is a challenge because the molecular self-organization in the
mesophase can be exploited to improve device performances for
different applications such as linear polarized electroluminescence
[6]. They are also interesting because of their carrier high charge
mobility, which makes them able to develop defect-free layers [7].
Related with highly luminescent materials it is noticeable the
interest up surged in the research of fluorescent organoboron dyes
such as 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as
well as borondiketonates for their applications within fields as
molecular probes [1], photosensitizers [2] and lasers [3] because
they possess large molar extinction coefficients, two-photon
absorption cross section, high emission quantum yields and sensi-
tivity to the surrounding medium. Strongly blue-absorbing dyes
have recently stirred a growing interest in fluorescent imaging
gested as two-photon probes for in vivo studies with the excitation
in the transparent window of tissues due to their intense blue–
green luminescence [7], giving their absorption wavelengths for
their p–
p⁄ transitions much shorter than their analogs BF2-pyrro-
methenes [8].
On the other hand, in designing metallomesogens (metal-
containing liquid crystals), metal centers and ligands can be used
to control the mesomorphism of the materials, so metals can in-
duce mesomorphism when incorporated in non-mesomorphic
materials or mesomorphic ligands can suffer dramatic effects in
their liquid crystal properties by coordination to a metal centre.
However, although the field of metallomesogens based on transi-
tion metals has properly expanded, no relevant information is pro-
duced by considering the presence of a metalloid such as boron,
which offers new opportunities.
With these considerations in mind, our work has been directed
towards the research of new luminescent materials based on bor-
ondifluoride b-diketonate compounds which are designed to exhi-
bit additional liquid crystal behavior.
In this context, our previous works were directed towards the
study of the photophysical properties of compounds of the type
[BF2(OOR(n))] and [BF2(OO2R(n))] (OOR(n) = 3-(4-alkyloxyphenyl)-
⇑
Corresponding author. Tel.: +34 91394 4340; fax: +34 91394 4352.
E-mail address: mmcano@quim.ucm.es (M. Cano).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.06.014

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
125
propane-1,3-dionate and OO2R(n) = 1,3-bis-(4-alkyloxyphenyl)-pro-
pane-1,3-dionate, R(n) = C6H4OCnH2n+1). All of them were highly
luminescent materials, displaying intense green or blue lumines-
cence in the solid state and in solution, but none of them exhibited
liquid crystal behavior [9].
Following our interest on boron complexes with accessible
mesophases, the structure of the ligands was strategically modified
taking into account concepts such as the lowering of the symmetry
or the diminution of the lateral interactions that had been success-
fully used to improve the mesomorphic behavior [10]. In particu-
lar, by reducing the symmetry by building unsymmetrical
materials, the molecules ought to pack less favourably in the solid
state, hence reducing the melting temperatures, and potentially,
the clearing temperatures.
ence (7.26 ppm), and coupling constants
J
are in hertz.
Multiplicities are indicated as s (singlet), d (doublet), t (triplet),
m (multiplet). The 1H chemical shifts and coupling constants are
accurate to 0.01 ppm and 0.3 Hz, respectively.
Phase studies were carried out by optical microscopy using an
Olympus BX50 microscope equipped with a Linkam THMS 600
heating stage. The temperatures were assigned on the basis of op-
tic observations with polarized light.
Measurements of the transition temperatures were made using
a Perkin–Elmer Pyris 1 differential scanning calorimeter with the
sample (1–4 mg) sealed hermetically in aluminum pans and with
a heating or cooling rate of 5–10 K minꢀ1
.
The X-ray diffractograms at variable temperature were re-
corded on a Panalytical X’Pert PRO MPD diffractometer in a h–h
configuration equipped with a Anton Paar HTK1200 heating stage
(X-ray Diffraction Service of Complutense University).
On these basis we decided to involve unsymmetrically substi-
tuted b-diketonates of the type 1-(4-alkyloxyphenyl)-3-(4-alkyl-
oxyphenyl)-propane-1,3-dionate, OOR(n)R(m) (R(n) = C6H4OCnH2n+1
,
Absorption spectra were recorded on a JASCO V-650 spectro-
photometer and fluorescence emission on a Horiba–Jobin–Yvon
Fluoromax-4 spectrofluorimeter equipped with a ThermoNeslab
RTE7 bath. The linearity of the fluorescence emission verses con-
R(m) = C6H4OCmH2m+1) as ligands towards BF2 as a support for li-
quid crystal behavior. The first results obtained for the compounds
[BF2(OOR(12)R(m))] (m = 14, 16, 18) evidenced the liquid crystal
behavior of those materials, which exhibited B1 mesophases
although in a short range of temperatures [11].
centration was checked in the concentration range used (10ꢀ4
–
10ꢀ6 M). A correction for the absorbed light was performed when
necessary. All spectrofluorimetric studies were performed as fol-
lows: the stock solutions of the ligands (ca. 10ꢀ3 M) were prepared
by dissolving an appropriate amount of the ligand in a 5 mL volu-
metric flask and diluting to the mark with dichloromethane HPLC
or UVA-sol grades. Fluorescence spectra of solid samples were re-
corded on the spectrofluorimeter exciting the solid compounds at
appropriated k (nm) using a fiber-optics device connected to the
spectrofluorimeter. The emission spectra as a function of the tem-
perature were recorded in the 300–800 nm range, using a fiber op-
tic system connected to the spectrofluorimeter and the solid
samples were heated over a hotplate with an external temperature
control provided with a digital thermo par.
Encouraged by these results, we were interested in confirming
the above proposal by the study of related boron derivatives for
which existed the possibility of varying independently the chain
length of the alkyloxyphenyl substituent in each position of the
b-diketonate. This systematic variation allows us to analyze the
influence of both factors, the asymmetry and the overall molecular
length, in the mesomorphism of the compounds.
Thus, the following families of complexes [BF2(OOR(n)R(m))] with
n = 12, 14, 16, 18 and m = 4, 8, 10 have been prepared and their
thermal and photophysical studies have been carried out. Through-
out this paper the abbreviation Dn,m is used for the unsymmetri-
cally 1,3-alkyloxyphenyl substituted b-diketones;
n and m
indicate the number of carbon atoms in the alkyloxy chains. As
well, the related borondifluoride b-diketonate complexes are rep-
resented by Bn,m
.
Thus, for instance, D12,4 is the diketone
2.2. Synthesis of the compounds [HOOR(n)R(m)] (n = 12, 14, 16, 18;
m = 4, 6, 8, 10, 14, 16) (Dn,m)
[HOOR(12)R(4)] and B12,4 is the complex [BF2(OOR(12)R(4))].
Thus, four families of compounds have been prepared and their
properties discussed. The strategic introduction of asymmetry in
this type of compounds appeared to provide a lateral dipole
favouring the mesomorphic properties.
The compounds Dn,m were obtained by Claysen synthesis be-
tween a 4-alkyloxyacetophenone and an ethyl 4-alkyloxybenzoate.
The general procedure is described as follows: To a solution of
12 mmol of the 4-alkyloxyacetophenone and 30 mmol of NaH
(60 wt.% dispersion in mineral oil) in dimethoxyethane (250 mL),
15 mmol of the corresponding ethyl 4-alkyloxybenzoate were
slowly added. The solution was refluxed for 24 h. The resulting sus-
pension was left to cool at room temperature and then added to
water (600 mL). By addition of a hydrochloric acid solution (spec.
grav. 1.19) until pH 2 a brown precipitate was obtained. The mix-
ture was stirred for 24 h at room temperature and then the brown
precipitate was filtered off and washed repeatedly with 50 mL hex-
ane portions to yield a white solid which was dried in vacuo.
The compounds D18,12, D16,12 and D14,12, which will be used in
the discussion for comparative purposes, have been reported in
our previous work [11]. Yields, elemental analysis and spectro-
scopic IR and 1H NMR are given for all the b-diketones prepared.
A study and discussion of the liquid crystal behavior of the new
b-diketones, as precursors of the b-diketonate ligands, is also
included.
2. Experimental
2.1. Materials and physical measurements
All commercial reagents were used as supplied. The synthetic
route to unsymmetrical alkyloxyphenyl disubstituted b-diketones
was carried out following a similar procedure to that used for the
related symmetrical derivatives [9,11–13].
Elemental analyses for carbon and hydrogen were carried out
by the Microanalytical Service of Complutense University (vali-
dated range: %C 0.50–94.7 and %H 0.50–7.6). IR spectra were re-
corded on a FTIR Thermo Nicolet 200 spectrophotometer with
samples as KBr pellets or in dichloromethane solution in the
4000–400 cmꢀ1 region: vs (very strong), s (strong), m (medium),
w (weak).
2.2.1. [HOOR(12)R(4)] (D12,4
)
Yield: 3.12 g (52%). Anal. Calc. for C31H44O4ꢁH2O (498.7 g molꢀ1):
C, 74.66; H, 9.30. Found: C, 75.00; H, 9.18%. IR (KBr, cmꢀ1): 3431w
(OH), 1673s (C@O enol form) and 1606s (C@C)Ø. 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.6, CH3 R(12)), 0.99
(t, 3J 7.4, CH3 R(4)), 1.27 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.6,
OCH2), 4.52 (s CH2 keto form), 6.73 (s, CH enol form), 6.93 (d, 3J 8.7,
1H NMR spectra were performed at room temperature on a
Bruker DPX-300 spectrophotometer (NMR Service of Complutense
University) from solutions in CDCl3. Chemical shifts d are listed rel-
ative to Me4Si using the signal of the deuterated solvent as refer-
3
3
Hm), 6.96 (d, 3J 8.7, Hm ), 7.94 (d, J 8.7, Ho), 8.05 (d, J 8.7, Ho ).
0
0

126
I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
2.2.2. [HOOR(12)R(8)] (D12,8
)
2.2.9. [HOOR(16)R(6)] (D16,6
)
Yield: 3.37 g (49%). Anal. Calc. for
C
35H52O4ꢁ2H2O
Yield: 5.24 g (75%). Anal. Calc. for
C
37H56O4ꢁ1.25H2O
(572.8 g molꢀ1): C, 73.39; H, 8.85. Found: C, 73.35; H, 8.86%. IR
(KBr, cmꢀ1): 3431w (OH), 1672s (C@O enol form) and 1607s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s
(587.4 g molꢀ1): C, 75.66; H, 10.03. Found: C, 75.70; H, 9.64%. IR
(KBr, cmꢀ1): 3422w (OH), 1673s (C@O enol form) and 1607s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.90 (t, 3J 6.5,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.03 (t, 3J 6.5, OCH2), 4.52 (s
CH2 keto form), 6.73 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95
CH2 keto form), 6.72 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95
3
3
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
(d, 3J 8.9, Hm’), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
0
0
2.2.3. [HOOR(12)R(10)] (D12,10
Yield: 4.08 g (57%). Anal. Calc. for
)
2.2.10. [HOOR(16)R(8)] (D16,8
)
C
37H56O4ꢁ1.75H2O
Yield: 5.16 g (70%). Anal. Calc. for C39H60O4ꢁH2O (610.9 g molꢀ1):
C, 76.68; H, 10.23. Found: C, 76.81; H, 9.98%. IR (KBr, cmꢀ1): 3431w
(OH), 1673s (C@O enol form) and 1607s (C@C)Ø. 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7, CH3), 1.26 (m,
CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s CH2 keto form),
(596.4 g molꢀ1): C, 74.52; H, 10.06. Found: C, 74.55; H, 9.26%. IR
(KBr, cmꢀ1): 3432w (OH), 1686s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.6,
CH3), 1.27 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.6, OCH2), 4.52 (s
CH2 keto form), 6.73 (s, CH enol form), 6.93 (d, 3J 8.9, Hm), 6.96
6.73 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95 (d, 3J 8.9, Hm ),
0
3
(d, 3J 8.9, Hm’), 7.94 (d, 3J 8.9, Ho), 8.05 (d, J 8.9, Ho ).
0
7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
3
0
2.2.4. [HOOR(14)R(4)] (D14,4
Yield: 5.02 g (79%).
)
Anal.
Calc. for
C
33H48O4ꢁH2O
2.2.11. [HOOR(16)R(10)] (D16,10
Yield: 5.65 g (73%). Anal. Calc. for
)
(526.8 g molꢀ1): C, 75.25; H, 9.57. Found: C, 75.08; H, 9.51%. IR
(KBr, cmꢀ1): 3429w (OH), 1672s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7,
CH3 R(14)), 0.99 (t, 3J 7.4, CH3 R(4)), 1.26 (m, CH2), 1.81 (m, CH2),
4.02 (t, 3J 6.7, OCH2), 4.52 (s CH2 keto form), 6.73 (s, CH enol form),
C
41H64O4ꢁ1.5H2O
(648.0 g molꢀ1): C, 76.00; H, 10.42. Found: C, 76.35; H, 9.69%. IR
(KBr, cmꢀ1): 3434w (OH), 1673s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s
6.93 (d, 3J 8.9, Hm), 6.96 (d, 3J 8.9, Hm ), 7.94 (d, J 8.9, Ho), 8.04 (d, J
CH2 keto form), 6.73 (s, CH enol form), 6.93 (d, 3J 8.9, Hm), 6.96
3
3
0
3
8.9, Ho ).
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
0
0
2.2.5. [HOOR(14)R(6)] (D14,6
Yield: 4.52 g (65%). Anal. Calc. for
)
2.2.12. [HOOR(16)R(14)] (D16,14
Yield: 5.70 g (67%). Anal. Calc. for
)
C
35H52O4ꢁ2.5H2O
C
45H72O4ꢁ1.5H2O
(581.4 g molꢀ1): C, 72.25; H, 9.87. Found: C, 72.66; H, 8.56%. IR
(KBr, cmꢀ1): 3445w (OH), 1685s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.91 (t, 3J 6.5,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.5, OCH2), 4.53 (s
(704.1 g molꢀ1): C, 76.77; H, 10.74. Found: C, 76.35; H, 9.98%. IR
(KBr, cmꢀ1): 3427w (OH), 1680s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.5,
CH3), 1.27 (m, CH2), 1.80 (m, CH2), 4.02 (t, 3J 6.5, OCH2), 4.52 (s
CH2 keto form), 6.73 (s, CH enol form), 6.93 (d, 3J 8.9, Hm), 6.96
CH2 keto form), 6.72 (s, CH enol form), 6.93 (d, 3J 8.9, Hm), 6.96
3
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.05 (d, J 8.9, Ho ).
0
0
3
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
0
2.2.6. [HOOR(14)R(8)] (D14,8
Yield: 6.15 g (88%).
)
Anal. Calc.
for
C37H56O4ꢁH2O
2.2.13. [HOOR(18)R(4)] (D18,4
Yield: 4.62 g (67%). Anal. Calc. for
)
(582.9 g molꢀ1): C, 76.25; H, 10.03. Found: C, 75.99; H, 9.79%. IR
(KBr, cmꢀ1): 3431w (OH), 1672s (C@O enol form) and 1607s
(C@C)Ø. IR (CH2Cl2, cmꢀ1) 1724 m (C@O keto form), 1686 m (C@O
enol form) and 1604s (C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si)
d (ppm): 0.88 (t, 3J 6.7, CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t,
3J 6.7, OCH2), 4.52 (s CH2 keto form), 6.73 (s, CH enol form), 6.92
C
37H56O4ꢁ0.5H2O
(573.9 g molꢀ1): C, 77.44; H, 10.01. Found: C, 77.15; H, 10.05%. IR
(KBr, cmꢀ1): 3431w (OH), 1687s (C@O enol form) and 1608s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.87 (t, 3J 6.8,
CH3 R(18)), 0.99 (t, 3J 7.4, CH3 R(4)), 1.25 (m, CH2), 1.80 (m, CH2),
4.02 (t, 3J 6.8, OCH2), 4.52 (s CH2 keto form), 6.73 (s, CH enol form),
(d, 3J 8.9, Hm), 6.95 (d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, 3J
6.93 (d, 3J 8.9, Hm), 6.96 (d, 3J 8.9, Hm ), 7.94 (d, J 8.9, Ho), 8.04 (d, J
3
3
0
0
0
0
8.9, Ho ).
8.9, Ho ).
2.2.7. [HOOR(14)R(10)] (D14,10
Yield: 5.77 g (79%). Anal.
)
2.2.14. [HOOR(18)R(6)] (D18,6
Yield: 4.98 g (67%). Anal. Calc. for
)
Calc.
for
C39H60O4ꢁH2O
C
39H60O4ꢁ1.5H2O
(610.9 g molꢀ1): C, 76.68; H, 10.23. Found: C, 76.85; H, 9.83%. IR
(KBr, cmꢀ1): 3438w (OH), 1672s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s
(619.9 g molꢀ1): C, 75.56; H, 10.24. Found: C, 75.92; H, 9.93%. IR
(KBr, cmꢀ1): 3417w (OH), 1687s (C@O enol form) and 1608s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.5,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.03 (t, 3J 6.5, OCH2), 4.52 (s
CH2 keto form), 6.73 (s, CH enol form), 6.93 (d, 3J 8.9, Hm), 6.96
CH2 keto form), 6.72 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
3
0
0
3
(d, 3J 8.9, Hm’), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
2.2.8. [HOOR(16)R(4)] (D16,4
Yield: 4.98 g (75%).
)
Anal. Calc.
for
C
35H52O4ꢁH2O
2.2.15. [HOOR(18)R(8)] (D18,8
)
(554.8 g molꢀ1): C, 75.77; H, 9.81. Found: C, 76.04; H, 9.60%. IR
(KBr, cmꢀ1): 3420w (OH), 1673s (C@O enol form) and 1607s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.87 (t, 3J 6.6,
CH3 R(16)), 0.99 (t, 3J 7.4, CH3 R(4)), 1.25 (m, CH2), 1.81 (m, CH2),
4.02 (t, 3J 6.6, OCH2), 4.52 (s CH2 keto form), 6.73 (s, CH enol form),
Yield: 4.13 g (51%). Anal. Calc. for C41H64O4ꢁ3H2O
(675.0 g molꢀ1): C, 72.96; H, 9.45. Found: C, 73.30; H, 9.33%. IR
(KBr, cmꢀ1): 3445w (OH), 1673s (C@O enol form) and 1606s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7,
CH3), 1.25 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s
6.92 (d, 3J 8.9, Hm), 6.96 (d, 3J 8.9, Hm ), 7.94 (d, J 8.9, Ho), 8.04 (d, J
CH2 keto form), 6.73 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95
3
3
0
8.9, Ho ).
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
3
0
0
0

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
127
2.2.16. [HOOR(18)R(10)] (D18,10
)
2.3.4. [BF2OOR(14)R(4)] (B14,4
)
Yield: 5.14 g (63%). Anal. Calc. for C43H68O4ꢁ1.5H2O (676.0
gmolꢀ1): C, 76.40; H, 10.59. Found: C, 76.11; H, 9.72%. IR (KBr,
cmꢀ1): 3427w (OH), 1672s (C@O enol form) and 1606s (C@C)Ø.
1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.7, CH3),
1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.7, OCH2), 4.52 (s CH2 keto
Anal. Calc. for C33H47O4BF2 (556.6 g molꢀ1): C, 71.22; H, 8.51.
Found: C, 70.88; H, 8.31%. IR (KBr, cmꢀ1): 1561vs (C@O), 1503s
(C@C)Ø, 1378 m (BO) and 1033s (BF). 1H NMR (300 MHz; CDCl3;
Me4Si) d (ppm): 0.88 (3H, t, 3J 6.7, CH3 R(14)), 0.99 (3H, t, 3J 7.4,
CH3 R(4)), 1.26 (24H, m, CH2), 1.83 (4H, m, CH2), 4.07 (4H, t, 3J
6.7, OCH2), 7.00 (1H, s, CH), 7.00 (4H, d, 3J 9.0, Hm), 8.11 (4H, d, 3J
9.0, Ho).
form), 6.73 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95 (d, 3J 8.9,
3
m ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
0
H
2.3.5. [BF2OOR(14)R(8)] (B14,8
)
2.2.17. [HOOR(18)R(14)] (D18,14
Yield: 7.25 g (78%). Anal. Calc. for
)
Anal. Calc. for C37H55O4BF2ꢁ0.05(CH2Cl2) (616.9 g molꢀ1): C,
72.14; H, 8.99. Found: C, 72.05; H, 8.59%. IR (KBr, cmꢀ1): 1561vs
(C@O), 1503s (C@C)Ø, 1376 m (BO) and 1036s (BF). 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (6H, t, 3J 6.7, CH3), 1.27
(32H, m, CH2), 1.83 (4H, m, CH2), 4.08 (4H, t, 3J 6.7, OCH2), 6.99
(1H, s, CH), 7.00 (4H, d, 3J 9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
C
47H76O4ꢁ4H2O
(777.2 g molꢀ1): C, 72.64; H, 10.89. Found: C, 72.77; H, 10.06%. IR
(KBr, cmꢀ1): 3427w (OH), 1687s (C@O enol form) and 1607s
(C@C)Ø. 1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.4,
CH3), 1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.4, OCH2), 4.52 (s
CH2 keto form), 6.72 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95
3
(d, 3J 8.9, Hm ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
0
0
2.3.6. [BF2OOR(16)R(4)] (B16,4
)
Anal. Calc. for C35H51O4BF2ꢁ0.15(CH2Cl2) (597.3 g molꢀ1): C,
70.68; H, 8.66. Found: C, 70.56; H, 8.40%. IR (KBr, cmꢀ1): 1562vs
(C@O), 1503s (C@C)Ø, 1378 m (BO) and 1030s (BF). 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (3H, t, 3J 6.7, CH3 R(16)),
0.99 (3H, t, 3J 7.4, CH3 R(4)), 1.26 (28H, m, CH2), 1.83 (4H, m,
CH2), 4.07 (4H, t, 3J 6.7, OCH2), 7.00 (1H, s, CH), 7.00 (4H, d, 3J
9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
2.2.18. [HOOR(18)R(16)] (D18,16
Yield: 7.12 g (77%). Anal. Calc. for
)
C
49H80O4ꢁ2H2O (769.2
gmolꢀ1): C, 76.51; H, 11.01. Found: C, 76.49; H, 10.17%. IR (KBr,
cmꢀ1): 3444w (OH), 1679s (C@O enol form) and 1607s (C@C)Ø.
1H NMR (300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (t, 3J 6.4, CH3),
1.26 (m, CH2), 1.81 (m, CH2), 4.02 (t, 3J 6.4, OCH2), 4.52 (s CH2 keto
form), 6.72 (s, CH enol form), 6.92 (d, 3J 8.9, Hm), 6.95 (d, 3J 8.9,
3
0
0
H
m ), 7.94 (d, 3J 8.9, Ho), 8.04 (d, J 8.9, Ho ).
2.3.7. [BF2OOR(16)R(8)] (B16,8
)
Anal. Calc. for C39H59O4BF2 (640.7 g molꢀ1): C, 73.11; H, 9.28.
Found: C, 73.27; H, 9.00%. IR (KBr, cmꢀ1): 1561vs (C@O), 1504s
(C@C)Ø, 1378 m (BO) and 1036s (BF). 1H NMR (300 MHz; CDCl3;
Me4Si) d (ppm): 0.88 (6H, t, 3J 6.7, CH3), 1.27 (36H, m, CH2), 1.83
(4H, m, CH2), 4.07 (4H, t, 3J 6.7, OCH2), 6.99 (1H, s, CH), 7.00 (4H,
d, 3J 9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
2.3. Synthesis of the compounds [BF2(OOR(n)R(m))] (n = 12, 14, 16, 18;
m = 4, 8, 10) (Bn,m
)
To a solution in dichloromethane (50 mL) of 1 mmol of the cor-
responding sodium b-diketonate (prepared in situ from 1 mmol of
the b-diketone and 1.5 mmol of NaH 60% dispersion in mineral oil),
5 mmol of HBF4ꢁEt2O were added. The mixture was stirred at room
temperature for 24 and then cooled down at ꢀ18 °C. The yellow so-
lid formed was filtered off in vacuo and purified by chromatogra-
2.3.8. [BF2OOR(18)R(4)] (B18,4
)
Anal. Calc. for C37H55O4BF2ꢁ0.15(CH2Cl2) (625.4 g molꢀ1): C,
71.35; H, 8.91. Found: C, 71.36; H, 8.59%. IR (KBr, cmꢀ1): 1549vs
(C@O), 1498s (C@C)Ø, 1374 m (BO) and 1033s (BF). 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (3H, t, 3J 6.7, CH3 R(18)),
0.99 (3H, t, 3J 7.4, CH3 R(4)), 1.26 (32H, m, CH2), 1.82 (4H, m,
CH2), 4.07 (4H, t, 3J 6.7, OCH2), 7.00 (1H, s, CH), 7.00 (4H, d, 3J
9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
phy using dichloromethane as eluent. The compounds B18,12
,
B16,12 and B14,12, reported by us [11] will be used in this work in
the discussion. Elemental analysis and spectroscopic data are given
as follows.
2.3.1. [BF2OOR(12)R(4)] (B12,4
)
Anal. Calc. for
C
31H43O4BF2ꢁ0.3(CH2Cl2) (554.0 g molꢀ1): C,
67.86; H, 7.93. Found: C, 67.85; H, 7.71%. IR (KBr, cmꢀ1): 1548vs
(C@O), 1502s (C@C)Ø, 1378 m (BO) and 1038s (BF). 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.88 (3H, t, 3J 6.7, CH3 R(12)),
0.99 (3H, t, 3J 7.4, CH3 R(4)), 1.27 (20H, m, CH2), 1.83 (4H, m,
CH2), 4.07 (4H, t, 3J 6.7, OCH2), 7.00 (1H, s, CH), 7.00 (4H, d, 3J
9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
2.3.9. [BF2OOR(18)R(8)] (B18,8
)
Anal. Calc. for C41H63O4BF2 (668.8 g molꢀ1): C, 73.64; H, 9.50.
Found: C, 73.39; H, 9.18%. IR (KBr, cmꢀ1): 1562vs (C@O), 1504s
(C@C)Ø, 1378 m (BO) and 1035s (BF). 1H NMR (300 MHz; CDCl3;
Me4Si) d (ppm): 0.88 (6H, t, 3J 6.7, CH3), 1.26 (40H, m, CH2), 1.82
(4H, m, CH2), 4.07 (4H, t, 3J 6.7, OCH2), 7.00 (1H, s, CH), 7.00 (4H,
d, 3J 9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
2.3.2. [BF2OOR(12)R(8)] (B12,8
)
Anal. Calc. for C35H51O4BF2ꢁ0.15(CH2Cl2) (597.3 g molꢀ1): C,
70.68; H, 8.66. Found: C, 70.63; H, 8.35%. IR (KBr, cmꢀ1): 1556vs
(C@O), 1502s (C@C)Ø, 1376 m (BO) and 1036s (BF). 1H NMR
(300 MHz; CDCl3; Me4Si) d (ppm): 0.90 (6H, t, 3J 6.7, CH3), 1.28
(28H, m, CH2), 1.83 (4H, m, CH2), 4.08 (4H, t, 3J 6.7, OCH2), 6.99
(1H, s, CH), 7.00 (4H, d, 3J 9.0, Hm), 8.11 (4H, d, 3J 9.0, Ho).
3. Results and discussion
3.1. Characterization and thermal studies of the b-diketones
[HOOR(n)R(m)
]
The ligands play a key role in determining the mesomorphic
behavior, since they can control the molecular shape and polariza-
tion by using suitable substituents. Before discussing the meso-
morphism of the new b-diketones described in this work we
consider of interest the data reported for previous related
compounds.
The symmetrically 1,3-alkyloxyphenyl substituted b-diketone
ligands, [HOO2R(n)], Dn,n, n = 8, 9 and 10, have been previously re-
ported by Ohta and col. as mesomorphic compounds [13,14]
2.3.3. [BF2OOR(12)R(10)] (B12,10
)
Anal. Calc. for C37H55O4BF2 (612.7 g molꢀ1): C, 72.54; H, 9.05.
Found: C, 72.02; H, 8.67%. IR (KBr, cmꢀ1): 1562vs (C@O), 1504s
(C@C)Ø, 1378 m (BO) and 1036s (BF). 1H NMR (300 MHz; CDCl3;
Me4Si) d (ppm): 0.89 (6H, t, 3J 6.7, CH3), 1.27 (32H, m, CH2), 1.83
(4H, m, CH2), 4.07 (4H, t, 3J 6.7, OCH2), 6.99 (1H, s, CH), 7.00 (4H,
d, 3J 9.0, Hm), 8.10 (4H, d, 3J 9.0, Ho).

128
I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
correspond to the ortho and meta protons of the phenyl rings, of
the two tautomeric keto and enol forms.
OH
O
The IR spectrum of D14,8, as a representative example, in CH2Cl2
solution shows two bands in the carbonyl region at 1724 and
1683 cmꢀ1 assigned to the
m(CO) absorption frequencies of the keto
and enol forms, respectively. By contrast, the IR spectra in the solid
state of all the compounds exhibit only one band in this region at
ca. 1671 cmꢀ1. This fact is in agreement with the presence of the
enol form as the unique tautomer in the solid state. Bands at ca.
H2n+1CnO
OCmH2m+1
1607 and 3431 cmꢀ1 assigned to the
tions are also observed.
m(C@C)Ø and m(OH) absorp-
D12,m
D14,m
D16,m
D18,m
n = 12 m = 4, 8, 10, 14, 16, 18
n = 14 m = 4, 6, 8, 10, 12, 16, 18
n = 16 m = 4, 6, 8, 10, 12, 14, 18
n= 18 m = 4, 6, 8, 10, 12, 14, 16
The new b-diketones studied exhibit mesomorphic behavior
(Table 1), showing SmC mesophases in all cases (Fig. 3a, b and d)
and N mesophases in some of them (Fig. 3c and d). Several solid–
solid phase transitions are observed as well.
The Cr ? SmC phase transition typically varies between 81 and
105 °C. In general terms, it was observed that the variation on the
number of carbon atoms in both alkyl chains, n and m, decreased
or increased the stability of the crystalline phase, being this fact re-
flected by the lowering or the increasing of the melting point as it
is commented as follows.
An analysis of the thermal behavior of the four families of com-
pounds allows us to observe two tendencies in the variation of the
melting temperatures in each family, depending on the chain
length with m P 10 or m 6 10 carbon atoms, I and II, respectively.
On one hand, for compounds of the families D14,m, D16,m and
D18,m with a full length of the alkyl chains of L = m + n P 24, 26
and 28 carbon atoms, respectively (I), the melting temperatures
decrease by increasing the asymmetry |m ꢀ n| which is consistent
with an increasing of the molecular length. Therefore, for each kind
of family, the best results were obtained for compounds with the
shortest chains, D14,10, D16,10 and D18,10, respectively. However, in
the family D12,m with L > 22 (I), although a decreasing in the melt-
ing temperatures was also observed by increasing the asymmetry,
in this case the lowest melting temperature was found for the lon-
Fig. 1. b-Diketones studied.
exhibiting a mesophase which was described by Serrano and co-
workers. as a crystalline smectic phase [15].
Related b-diketones with longer n = 12, 14, 16 and 18 carbon
atoms in the alkyl chains, D12,12, D14,14, D16,16 and D18,18 were stud-
ied in our lab and clearly determined as mesomorphic materials
showing SmC phases in the temperature range of 94–130 °C [16].
Moreover, unsymmetrically substituted b-diketones of the type
[HOOR(n)R(m)], Dn,m, were also reported for n = 7 and m = 9, 10 car-
bon atoms in the alkyl chains of the substituents at 1(3) and 3(1)
positions. D7,9 did not show mesomorphic behavior, but the longer
D7,10 exhibited a monotropic smectic phase [17].
On the other hand, some other b-diketones with three or four
alkyl chains in the aromatic substituents, such as 1-(3,4-dialkyl-
oxyphenyl)-3-(4-alkyloxyphenyl)-propane-1,3-dione and 1-(3,4-
dialkyloxyphenyl)-3-(3,4-dialkyloxyphenyl)-propane-1,3-dione
have been also reported as non-liquid crystal materials [17]. In
those compounds, the absence of mesomorphism has been ex-
plained on the basis that the increased number of terminal chains
on these ligands disrupts the calamitic mesomorphism [15].
In this work, four new series of unsymmetrically substituted b-
diketones have been prepared and structurally characterized
(Fig. 1). Their thermal behavior has been studied by differential
scanning calorimetry (DSC), polarized-light optical microscopy
(POM) and low angle temperature-dependent X-ray diffraction
(XRD).
gest compound, D12,18
.
On the other hand, for the compounds of all the above families,
but with shorter chains, L 6 22, 24, 26 and 28 for D12,m, D14,m, D16,m
and D18,m, respectively (II), the melting temperatures decrease by
increasing the full molecular length, being this fact related to the
concomitant decreasing of the asymmetry. As a consequence, those
with L = 22, 24, 26 and 28 for D12,m, D14,m, D16,m and D18,m, respec-
tively, are the compounds with lower melting points.
These variations are summarized, for the families D12,m and
D18,m, as representative examples in the Fig. 4a and b, respectively.
As a conclusion we can deduce that for compounds with longer
chains, m P 10, an increasing in the asymmetry is determining to
get lower transition temperatures. By contrast, the compounds of
all families having shorter chains, m 6 10, require the presence of
alkyl chains in both substituents with closer lengths to get a lower
melting temperature (Table 2).
The solution 1H NMR spectra in CDCl3 of all new compounds
Dn,m show well defined signals for the b-diketone core and the
alkyloxyphenyl substituents. The singlets at ca. 6.73 ppm from
CH proton and 4.52 ppm from CH2 protons of the central carbon
of the diketone core confirm the existence of keto and enol tautom-
ers in solution (Fig. 2), being the enol form the major one (>90%) as
deduced from the signal intensity ratio of the CH/CH2 protons.
However, in the NMR time-scale it was not possible to distinguish
between the two different possible enol forms (Fig. 2a and 2c).
Duplicated doublets at ca. 8.04, 7.94 and 6.96, 6.93 ppm
Temperature-dependent powder X-ray diffraction experiments
for some selected compounds confirmed the SmC mesophases
O
OH
O
O
OH
O
R
R'
R
R'
R
R'
(a)
(b)
(c)
R = OCnH2n+1; R' = OCmH2m+1
Fig. 2. Keto–enol equilibrium.

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
129
Table 1
Thermal behavior of compounds Dn,m.
T/ °C (
FAMILY COMPOUND Cr ?
D )
H / kJ mol-1
Cr’ ?
Cr’’ ?
91 (32.0)
SmC ?
N ?
113 (0.4)
I
?
N ?
106 (-0.4)
SmC ?
70 (-11.6)
Cr ?
Cr’
D12,m
D12,4
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
73 (18.3)
72 (43.7)
62 (5.4)
74 (7.2)
64 (6.5)
74 (21.3)
77 (15.7)
60 (18.4)
71 (14.9)
70 (12.6)
74 (7.2)
65 (-13.1)
83b
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
49 (-13.5)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
D12,8
86 (7.4)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
116a (2.8) ꢂ 116a (2.8) ꢂ 118a (-1.5) ꢂ 118a (-1.5) ꢂ
79 (-5.5)
74 (-6.8)
68 (-29.0)
69 (-9.8)
79 (-24.7)
76 (-20.1)
62b
55b
D12,10
D12,14
D12,16
D12,18
D14,4
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
79a (50.8)
ꢂ
ꢂ
84a,b (50.8)
93a,b (56.3)
116 (2.7)
ꢂ
118b
113 (2.9)
119 (3.7)
118b
ꢂ 117 (-1.7)
ꢂ
94 (-0.3)
108 (-1.4)
115 (-5.1)
114 (-4.4)
114 (-2.2)
71a (-7.3)
94b
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
67 (-19.6)
63 (-2.1)
60 (-8.8)
74 (-15.2)
56 (-10.4)
83a (56.3)
ꢂ
ꢂ
ꢂ
ꢂ
*
*
*
78a,b (50.5) ꢂ 89a (50.5)
81a (45.7)
81 (8.1)
ꢂ
86a,b (45.7)
95 (42.4)
94(43.0)
93 (43.5)
92a,b (57.7)
93a,b (56.3)
97 (42.2)
94(43.9)
D14,m
118 (2.6)
D14,6
D14,8
ꢂ
115a (2.1) ꢂ 115a (2.1) ꢂ 116 (-1.1)
ꢂ
ꢂ
112 (3.9)
ꢂ
124b
ꢂ 114 (-2.9)
72 (-20.1)
68 (-37.8)
68 (-29.0)
76 (-39.6)
83 (-22.4)
82 (-17.1)
84 (-29.1)
76 (-18.8)
59 (-8.0)
63 (-2.1)
ꢂ
ꢂ
D14,10
D14,12
D14,16
D14,18
D16,4
81a (57.7)
83a (56.3)
87 (12.6)
ꢂ
ꢂ
ꢂ
98 (0.2)
113 (2.9)
118 (3.2)
113 (4.4)
105 (0.9)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
95 (-0.9)
108 (-1.4)
111 (-1.9)
104 (-2.1)
102 (-0.4)
109 (-4.9)
107 (-1.5)
88 (-0.6)
115 (-5.1)
111 (-1.9)
96 (-1.0)
111 (-1.4)
120 (-7.8)
96 (-0.7)
92 (-1.0)
114 (-4.4)
104 (-2.1)
96 (-1.0)
*
*
*
75 (-8.2)
65 (-26.1)
ꢂ
ꢂ
D16,m
81 (29.4)
99 (30.1)
99 (50.6)
96 (39.4)
81a,b (49.3)
D16,6
D16,8
58b
114 (2.2)
ꢂ
123 (2.0) ꢂ 129b
ꢂ
76 (29.5)
60b
109 (3.2)
98 (1.2)
119 (3.7)
118 (3.2)
107b
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
64 (-18.4)
ꢂ
D16,10
D16,12
D16,14
D16,18
D18,4
D18,6
D18,8
D18,10
D18,12
D18,14
D18,16
75a (49.3)
ꢂ
63a,b (-26.4) ꢂ 57a (-26.4) ꢂ
64 (6.5)
65 (-13.1)
87 (15.6)
71 (10.8)
73a (10.9)
78a,b (50.5) ꢂ 89a (50.5)
69 (-9.8)
ꢂ
ꢂ
60 (-8.8)
ꢂ
87 (12.6)
93a (61.0)
85 (8.1)
ꢂ
ꢂ
ꢂ
97 (42.2)
76 (-39.6)
100a,b (61.0) ꢂ
82a,b (-57.8) ꢂ 79a (-57.8) ꢂ
D18,m
105 (50.1)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
116 (1.2)
126 (9.6)
112b
90 (-28.4)
80 (-31.4)
59 (-32.7)
57 (-27.3)
79 (-24.7)
83 (-22.4)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
73 (-20.6)
65 (-7.4)
ꢂ
ꢂ
77a,b (10.9) ꢂ 100 (56.2)
65a,b (54.8) ꢂ 75a (54.8)
ꢂ
89b
53b
ꢂ
ꢂ
ꢂ
ꢂ
78a,b (50.0) ꢂ 81a (50.0)
97 (1.5)
74 (21.3)
81a (45.7)
93a (61.0)
ꢂ
86a,b (45.7)
94 (43.9)
118b
74 (-15.2)
75 (-8.2)
ꢂ
ꢂ
83b
113 (4.4)
107b
87 (15.6)
ꢂ
100a,b (61.0) ꢂ
82a,b (-57.8) ꢂ 79a (-57.8) ꢂ
a
Overlapped processes.
Temperature determined by POM.
b
*
Ref. [11].
Fig. 3. Photomicrographs of the mesophases observed by POM: (a) SmC mesophase of D12,8 at 90 °C on heating; (b) SmC mesophase of D14,8 at 110 °C on heating; (c) N
mesophase of D14,8 at 120 °C on heating; and (d) SmC and N mesophases of D14,8 at 95 °C on cooling.
assigned by POM (Table 3). The pattern shows two or three maxima
in the low-angle region. The reciprocal spacing ratio of 1:2:3 indi-
cates the existence of a lamellar mesophase. The peaks are so as-
signed to the (0 0 1), (0 0 2) and (0 0 3) reflections of the smectic
phase. Also, the diffuse halo due to the fluid movement of the alkyl
chains appears in the medium angle region of the diffractograms.
For these compounds, the layer spacing, d, was smaller than the
molecular length in the full extended conformation, l, deduced by

130
I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
110
100
90
(a)
♦I (L≥ 26)
♦II (L≤ 22)
D12,14
MT / ºC
D12,4
D12,16
D12,8
D12,18
D12,10
80
70
12
16
20
24
28
32
n + m
110
100
90
(b)
D18,4
D18,6
D18,16
D18,14
♦I (L≥ 28)
♦II (L≤ 28)
MT / ºC
D18,8
D18,12
80
D18,10
70
18
22
26
30
34
38
n + m
Fig. 4. Melting temperatures of compounds D12,m (a) and D18,m (b) as a function of the molecular length.
Table 2
Influence of the molecular length and molecular asymmetry on the melting temperatures.
extrapolation from that found in the single-crystal X-ray diffrac-
tion of the related D4,4 [12]. This fact indicates that in this meso-
phase the molecules are inclined related to the layer.
Nematic enantiotropic phases were also observed for com-
pounds with L = 20 or 22 carbon atoms. Interestingly, those are
the shortest ones of the series D12,m, D14,m and D16,m (m = 6, 8,
10) with the exception of those with m = 4.
It seems that in the long chained b-diketones (L P 24), the high-
er interchain interactions due to the presence of longer alkyl chains
do not allow the characteristic disorder of the N phase.

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
131
Table 3
X-ray diffraction data for selected Dn,m compounds.
Compound
D12,10
T (°C)
Phase
SmC
Position 2h (°)
d-spacing (Å)
Miller indexes (hkl)
Lattice parameters (Å)
Estimated length (Å)
85 (cooling)
2.7
5.5
18.6
3.7
18.5
2.4
4.7
18.3
2.4
4.5
19.7
2.3
4.6
19.5
2.2
4.2
18.2
2.4
4.7
7.1
18.3
2.2
4.6
19.8
32.2
16.2
4.8
24.1
4.8
36.8
18.7
4.9
37.1
17.6
4.6
38.7
19.2
4.6
40.5
20.9
4.9
36.6
18.7
12.5
4.9
40.1
19.4
4.5
0 0 1
0 0 2
a
c = 32.2
l = 38.7
115 (cooling)
100 (cooling)
N
a
D14,8
D16,8
D16,10
D16,14
D18,4
SmC
0 0 1
0 0 2
a
0 0 1
0 0 2
a
0 0 1
0 0 2
a
0 0 1
0 0 2
a
0 0 1
0 0 2
0 0 3
a
0 0 1
0 0 2
a
c = 36.8
c = 37.1
c = 38.7
c = 40.5
c = 36.6
l = 38.7
l = 41.2
l = 43.7
l = 48.7
l = 38.7
100 (heating)
70 (cooling)
90 (cooling)
85 (cooling)
SmC
SmC
SmC
SmC
D18,10
70 (cooling)
SmC
c = 40.1
l = 46.2
a: Halo of the molten alkyl chains.
Then, we can establish that the type of mesophase obtained is
directly linked to the length of the alkyl chains attached to the phe-
nyl rings of the substituents at the 1,3 positions of the b-diketone.
The variation of the clearing temperatures of compounds of the
families D14,m, D16,m, D18,m follows the same sequence that those
observed in the melting temperatures By contrast, for the family
D12,m, the clearing temperatures exhibit an opposite variation to
that of the melting temperatures.
From the above comments we determine that for each family,
the compound exhibiting the lower melting temperature is that
with m = 10 carbon atoms, as shown in green in Table 2. Taking
into account this result, and also by considering the compound that
exhibits the highest range of the liquid crystal existence, including
SmC and N phases, we can conclude that the best results corre-
spond to the compound D12,10, showing phase transition tempera-
tures to the SmC and N phases of 84 and 116 °C, respectively, and a
clearing point of 118 °C (Table 2).
length and the asymmetry in the mesomorphism of the new boron
derivatives as well as to study the photoluminescent behavior.
The 1H NMR spectra in CDCl3 solution of all complexes Bn,m
show the characteristic signals of the alkyloxyphenyl substituted
b-diketonate ligand [11]. In all cases it is observed a singlet at ca.
7.00 ppm, which corresponds to the central proton of the diketo-
nate core (CH). This fact is consistent with the coordination of
the ligand as enolate form. Also, two doublets observed at ca.
8.11 and 7.00 ppm, respectively correspond to the ortho and meta
protons of the phenyl rings.
The IR spectra in KBr show an absorption band of the m(CO) fre-
quency at ca. 1561 cmꢀ1, bathocromically shifted with respect to
the free diketone, in agreement with that of the diketonate form.
Also the presence of the
of the (OH) band from the enol tautomer of the b-diketone indi-
m
(BO) band at ca. 1376 cmꢀ1 and the lack
m
cate the coordination of the carbonyl groups to the boron atom.
A band at ca. 1036 cmꢀ1, assigned to the
m(BF) absorption is also
observed.
The thermal behavior of the boron derivatives is shown in
Table 4. All the compounds behave as liquid crystals, showing an
3.2. Characterization and thermal studies of the complexes
[BF2(OOR(n)R(m))]
We have previously reported that the strategic design of
unsymmetrically 1,3-alkyloxyphenyl substituted borondifluoride
b-diketonates of the type [BF2(OOR(12)R(m))] (m = 14, 16 and 18)
was successfully used in order to obtain liquid crystal behavior
in addition to a high photoluminescent quantum yield [11]. We
were interested in proving if this behavior follows a regular pattern
so allowing to get the desired bifunctional materials.
F
F
B
O
O
Thus, following these precedents and taking into account the
thermal study of the new related b-diketones above described,
we now propose to extend the thermal and luminescent studies
to new families of unsymmetrical boron derivatives using as li-
gands the asymmetric 1,3-alkyloxyphenyl substituted diketones
maintaining one of the lateral chains with 4, 8 or 10 carbon atoms
while the other one is increased from 12 to 18 carbon atoms each
series (Fig. 5). Those ligands have been selected due to they exhib-
ited the best liquid crystal behavior, related with the melting tem-
perature and the mesophase stability range, and additionally
because they are adequate to compare the effect of the molecular
H2n+1CnO
OCmH2m+1
B12,m
B14,m
B16,m
B18,m
n = 12 m = 4, 8, 10
n = 14 m = 4, 8
n = 16 m = 4, 8
n = 18 m = 4, 8
Fig. 5. Borondifluoride complexes studied.

132
I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
Table 4
Thermal behavior of compounds Bn,m
.
T (°C) (
Family Compound Cr
D )
H/kJ molꢀ1
?
Cr’
?
Cr’’
?
B1
?
I
?
B1
?
Cr
?
Cr’
?
Cr’’
B12 m
,
B124
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
109 (10.6)
118 (11.3)
115 (18.6)
102 (4.6)
109 (14.0)
45 (8.5)
112 (24.1)
98 (58.3)
116 (29.7)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
132a (22.9)
142a (21.8)
143a (27.4)
131a (24.3)
139a (24.2)
120 (25.1)
135a (22.4)
133a (26.7)
134a (21.1)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
132a(22.9)
142a(21.8)
143a (27.4)
131a (24.3)
139a (24.2)
130 (12.2)
135a(22.4)
133a(26.7)
134a (21.1)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
132a (-22.2)
142a (-23.6)
142a (-26.5)
128a (-21.4)
139a (-24.3)
128a (-18.9)
135a (-23.6)
122a (-21.6)
133a (-22.4)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
132a (-22.9)
142a (-23.6)
142a (-26.5)
128a (-21.4)
139a (-24.3)
128a(-18.9)
135a (-23.6)
122a (-21.6)
133a (-22.4)
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
B12,8
B12,10
B14,4
B14,8
B16,4
B16,8
B18,4
B18,8
109 (-3.0)
87 (-16.0)
ꢂ
75 (-4.4)
ꢂ
B14,m
B16,m
B18,m
70b
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
86 (11.7)
110 (2.7)
ꢂ
ꢂ
109 (-3.4)
79 (-2.8)
110 (-4.0)
68b
a
Overlapped processes.
Temperature determined by POM.
b
enantiotropic mesophase at temperature close to the clearing.
Thus, a crystalline phase, the mesophase and the isotropic liquid
are almost observed at the same temperature. In agreement with
these features, the DSC thermograms show in the heating, in addi-
tion to a first peak due to a solid–solid transition, one wide peak
corresponding to the overlapped solid–mesophase–isotropic liquid
processes. On cooling, two peaks corresponding to the reverse pro-
cesses to those appearing on heating are observed. A first wide
peak is related to the mesophase growth as well as its crystalliza-
ence of crystals or the quick appearance of the isotropic liquid. The
mesophase was identified as a B1 mesophase. The phase transition
temperatures for our compounds are in a similar range to that
found for organic compounds exhibiting bent-core mesophases of
the B1 type [18–21].
The B1 phase is one of the so-called banana phases, formed by
bent-core mesogens. This phase seems to exhibit a fluid smectic
structure and, in general is observed as having a mosaic texture.
When cooling from the isotropic liquid, a dendritic growth of the
mesophase is observed with dendrites coalescing to form a mosaic
texture [22]. In our compounds, the mosaic texture could be clearly
observed in all cases (Fig. 6) both on heating and cooling, as well as
the dendritic growth (Fig. 6a) through a very slow decreasing of
temperature from the isotropic phase.
tion. The second peak is associated to
transition.
a solid–solid phase
In order to identify the mesophase nature, a careful and precise
control of the temperature was carried out by a slow POM observa-
tion, maintaining the temperature for several minutes each 0.1 °C
increasing or decreasing stage, both on heating and on cooling. In
this way, we were able to achieve the mesophase without the pres-
By comparing the phase transition temperatures of compounds
Bn,4 and Bn,8 from their DSC thermograms, we can deduce that, in
Fig. 6. Textures observed by POM of the B1 mesophase of B12,10 at 145.6 °C on cooling (a) and (b), and B14,8 at 140.5 °C on cooling (c) and (d).

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
133
general terms, the melting temperatures decrease as the difference
between the length of both alkyl chains of the substituents in-
creases, therefore, indicating that an increase of the asymmetry
gives rise to lower transition temperatures (Table 5).
b) here described, with m + n varying from 16 (B12,4) until 30
(B12,18) carbon atoms in length, it is evident that the lowest melting
temperatures are obtained for the longest and shortest com-
pounds, both showing the highest asymmetry.
So, for instance, taken the series Bn,4, melting temperatures are
moved from 132 to 120 °C when n is increased from 12 to 16 car-
bon atoms and a similar decrease from 142 to 134 °C is observed in
Taking into account these results, we can conclude that the
molecular asymmetry is a determining factor to obtain lower tran-
sition temperatures in this type of boron derivatives (Fig. 7).
On the other hand, in order to establish a complete identifica-
tion of the mesophase, temperature-dependent XRD studies were
carried out. Due to the narrow range of existence of the mesophase,
diffractograms were taken at different stages at temperatures close
to the clearing process, maintaining the temperature for several
minutes in each stage, as the same way used on the POM observa-
tion. Several registers were taken at each stage after different
Bn,8 compounds (Table 5b). Related derivatives previously reported
[11] are also included here for comparative purposes (Table 5a).
The same behavior was also observed for the compounds with
both chains longer than 10 carbon atoms (B12,m with m = 14, 16
and 18 carbon atoms), although for those compounds the increased
asymmetry is consistent with a higher full molecular length.
Therefore, by considering all the B12,n derivatives (Table 5a and
Table 5
Influence of the molecular asymmetry on the melting temperatures of compounds Bn,m
.
148
144
B12,10
140
136
132
128
B12,8
MT / ºC
B12,14
B12,16
B12,18
30
B12,4
14
18
22
26
n + m
Fig. 7. Melting temperature of the compounds B12,m as a function of the molecular length.

134
I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
Table 7
lapses of time. Due to this careful control, we were able to obtain
diffractograms, which allow us to establish the presence of a B1
phase. In these cases, the two or three reflection peaks, in the small
angle region, indexed as (1 0 1), (2 0 2) and (0 0 2), indicate a rect-
angular columnar arrangement (Table 6). The intensity of the sec-
ond peak is much higher than the first peak, as reported for B1
phases [19].
Photophysical characterization of selected compounds of the Bn,m type. (Absorption
and emission maxima in solution in the solid state in nm, molar absorption coefficient
Lmolꢀ1cmꢀ1 and fluorescence quantum yields in 2.0 ꢃ 10ꢀ6
M
dichloromethane
solution)
c
Complex
e
/104
Uf
solutiona
k
solutionb
k
solidd
max
em
max
abs
max
em
k
B16,4
B16,8
B16,12
412
412
412
7.9
5.4
6.8
439
438
437
0.95
0.92
0.95
474
488
486
3.3. Photophysical studies of the compounds [BF2(OOR(n)R(m))]
a
b
c
Estimated error: 1 nm.
kex = 412 nm; estimated error: 1 nm.
kex = 412 nm; estimated error: 5%.
kex = 412 nm; estimated error: 1 nm.
Electronic absorption spectra in dichloromethane solution and
emission spectra in the solid state and in dilute dichloromethane
d
solution were recorded for the complexes of the families B12,m
,
B14,m, B16,m and B18,m. Due to their similarity, only data of represen-
tative examples are depicted in Table 7. Those of the related com-
plex B16,12, previously reported by us [11], are also included for
comparative purposes.
All of the boron derivatives fluoresce at ca. 480 nm in the solid
state and at ca. 438 nm in dichloromethane solution (Fig. 8). The
chain length of the aryl substituents at the 1,3-positions of the b-
diketonate ligand has virtually no effect on the spectroscopic prop-
erties of these compounds.
3.3.3. Variable-temperature studies
In order to prove the luminescence of the compounds at the li-
quid crystal state, the luminescent behavior of the compounds B16,4
and B16,8 was studied at different temperatures from the solid state
to the isotropic liquid. The fluorescence spectra were also regis-
tered on cooling from the isotropic liquid until room temperature
(Fig. 10).
In general, the behavior of the emission band on heating shows
that the intensity of fluorescence is almost unaffected until ca.
120–130 °C and then it decreases by increasing the temperature.
It almost disappears at temperature of the isotropic liquid, when
a quenching on the fluorescence is observed due to the increase
of non radiative decay processes. The maximum of the fluorescence
emission was not totally recovered upon cooling, being restored
until 40% in some cases.
3.3.1. Solution studies
The UV–Vis absorption spectra of dilute solutions (ca. 2.0–
4.0 ꢃ 10ꢀ6 M) in dichloromethane of the compounds exhibit two
absorption bands, being the strongest one centred at ca. 412 nm
(Table 7, Fig. 9), characteristic of the electronic
p–
p⁄ transition of
The above results allow us to establish that the mesophase
aggregation state does not quench the emission. It is also remark-
able that the emission maximum is maintained in the heating/
cooling cycle, indicating that the excited state is not modified.
chelating b-diketonate ligands [23].
The fluorescence spectra display a broad band with an unre-
solved vibronic substructure in the blue region with a maximum
at ca. 438 nm. The emission shows an excellent photoluminescence
relative quantum yield (ca. 0.95, with an estimated error of 5%)
using a solution of anthracene as standard (
U = 0.27) [24]. The
4. Conclusions
emissive nature of these compounds was markedly higher than
that of our previously reported boron difluoride b-diketonates [9]
as well as that of several boron difluoride diaroylmethanato with
different substituents [7].
The high quantum yield, close to the unity, in addition to the
observed absorption in the yellow region and emission in the
blue–violet range, make these compounds to be good candidates
as fluorescent biological probes.
Four new families of unsymmetrically substituted b-diketones
[HOOR(n)R(m)
]
as well as their borondifluoride derivatives
[BF2(OOR(n)R(m))] were prepared and structurally characterized.
The thermal study indicates a mesomorphic behavior in all cases,
showing SmC and N mesophases for the b-diketones and bent-core
B1 mesophases for the boron derivatives.
It appears that the coordination of the diketonate ligand to the
borondifluoride fragment generates a bent-core molecular shape
involving three bonded cycles, in contrast with the open structure
3.3.2. Solid state studies
The photophysical properties of the compounds B16,m were also
studied in the solid state in order to establish their influence on the
fluorescent behavior. The emission spectra exhibit a similar pat-
tern consistent with a broad band centred at ca. 480 nm (Table 7,
Fig. 9) assigned to a ligand-centred transition (LCT) which is red-
shifted with respect to that observed in solution.
Table 6
X-ray diffraction data of selected compounds of the Bn,m type.
Compound T (°C)
Phase Position
d-
spacing
(Å)
Miller
Indexes
(hkl)
Lattice
parameters
(Å)
2h (°)
B12,4
129
(cooling)
B1
4.6
4.8
9.3
18.8
19.1
18.3
9.5
1 0 1
0 0 2
2 0 2
a
a = 22.4
c = 36.6
4.7
B18,4
133
(heating)
B1
3.5
4.2
18.6
25.1
21.3
4.8
1 0 1
0 0 2
a
a = 31.1
c = 42.5
Fig. 8. B10,12 in the solid state (left) and 10ꢀ5 M dichloromethane solution (right).
(kexc. = 365 nm).
a: Halo of the molten alkyl chains.

I. Sánchez et al. / Inorganica Chimica Acta 381 (2012) 124–136
135
0.15
Abs.
Abs.
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.15
Em. in the solid state
Em. in CH2Cl2 solution
Em. in the solid state
Em. in CH2Cl2 solution
a
b
A
A
0.8
0.10
0.10
0.6
0.4
0.05
0.00
0.05
0.2
0.00
0.0
250
300
350
400
450
500
550
600
650
700
250
300
350
400
450
500
550
600
650
700
λ / nm
λ
/ nm
Fig. 9. UV–Vis and normalized emission spectra in 2.0 ꢃ 10ꢀ6 M dichloromethane solution and in the solid state of (a) B16,4 and (b) B16,8 at room temperature (kex = 412 nm).
25 ºC
37 ºC
50 ºC
60 ºC
75 ºC
88 ºC
97 ºC
120 ºC
132 ºC
130 ºC
90 ºC
57 ºC
30 ºC
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
50 ºC
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
70 ºC
95 ºC
115 ºC
129 ºC
135 ºC
170 ºC
160 ºC
115 ºC
75 ºC
heating
cooling
heating
cooling
20
40
60
80
T / ºC
100
120
140
300
350
400
450
T / K
40 ºC
a
b
450
500
550
600
450
500
550
600
λ / nm
λ / nm
Fig. 10. Fluorescence spectra of (a) B16,4 and (b) B16,8 in the solid state as a function of temperature. Inset: intensity of emission as a function of the temperature
(kex = 412 nm).
of the free b-diketone. In agreement with this proposal a B1 meso-
phase is observed only in the boron derivatives, being the molecu-
lar asymmetry a determinant requirement to attain liquid crystal
behavior. New studies are in progress in order to extend the meso-
phase range.
of Spain, Project CTQ2010-19470 and Universidad Complutense
de Madrid (Spain), Project UCM2010-910300 for the financial
support.
I.S. thanks the Ministerio de Educación of Spain by the predoc-
toral scholarship from the FPU program.
The development of liquid crystal compounds based on achiral
bent-shaped molecules has recently attracted much attention due
to their potential application as materials with ferroelectric and
antiferroelectric properties. Taking into account that molecules de-
scribed for these purposes are typically organic, the consecution of
B1 mesophases with a central core of the borondifluoride b-diketo-
nate type opens new opportunities in the field of bent-core liquid
crystals.
E.O. thanks FCT-MCTES (Portugal) by the Postdoctoral Grant
SFRH/BPD/72557/2010. The University of Vigo INOU-ViCou K914
(Spain), Scientific PROTEOMASS Association (Ourense-Spain) and
Xunta de Galicia (Biomedicine sectorial program) project
09CSA043383PR for financial support are also acknowledge. We
are grateful to Dr. Carlos Lodeiro from the BIOSCOPE, Physical
Chemistry Department, University of Vigo, Spain for his help with
the photophysical studies.
From the photophysical studies of the boron derivatives, a high
quantum yield close to the unity was observed in all cases. In addi-
tion, the absorption located in the yellow region and their emission
in the blue-violet range make these new compounds to be good
candidates as fluorescent biological probes.
All the team thank to program ‘‘Joint Portuguese-Spanish Pro-
ject 2009’’ for bilateral agreement number 69/09 (Portugal)/HP
2008-0066 (Spain).
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