Synthesis of banana-like 1,3-dihydroxybenzene and 2,7-dihydroxynaphthalene esters and luminescence of their terbium(III) complexes

Article abstract of DOI:10.1134/S1070427211060139

New esters of 1,3-dihydroxybenzene and 2,7-dihydroxynaphthalene with 4-(4-alkoxybenzoyloxy)-2-(or 3-)methoxybenzoic acids were synthesized. The correlation between their structure and liquid crystal properties was examined, and the luminescence characteristics of terbium(III) complexes with these esters were studied.

Full text of DOI:10.1134/S1070427211060139

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 6, pp. 978–983. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © N.S. Novikova, E.D. Kilimenchuk, R.V. Kondrat’eva, S.B. Meshkova, Z.M. Topilova, 2011, published in Zhurnal Prikladnoi Khimii,
2011, Vol. 84, No. 6, pp. 954–959.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Synthesis of Banana-Like 1,3-Dihydroxybenzene
and 2,7-Dihydroxynaphthalene Esters
and Luminescence of Their Terbium(III) Complexes
N. S. Novikova, E. D. Kilimenchuk, R. V. Kondrat’eva,
S. B. Meshkova, and Z. M. Topilova
Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa, Ukraine
Received July 19, 2010
Abstract—New esters of 1,3-dihydroxybenzene and 2,7-dihydroxynaphthalene with 4-(4-alkoxybenzoyloxy)-
2-(or 3-)methoxybenzoic acids were synthesized. The correlation between their structure and liquid crystal
properties was examined, and the luminescence characteristics of terbium(III) complexes with these esters were
studied.
DOI: 10.1134/S1070427211060139
The advantages of liquid crystal displays (LCDs),
which are widely used today, are low power
consumption and flat screens. However, they also have
certain drawbacks such as limited angle of vision and
low brightness. Luminescent LCDs, which are emitting
displays and contain luminescent lanthanide com-
plexes, are more promising. Therefore, synthesis of
luminescent lanthanide complexes and elucidation of
the influence exerted by the ligand structure on the
luminescence intensity are very topical for the
development of such displays [1].
Liquid crystal lanthanide complexes containing as
ligands Schiff bases, β-enamino ketonates, β-diketo-
nates, and cholesterol esters with benzo crown ether
fragment are known [1]. The luminescence properties
of mesomorphic lanthanide complexes were examined
in a number of studies [2–4].
Previously [5] we demonstrated for the first time
the possibility of using liquid crystal banana-like com-
pounds, 4-methoxy-1,3-benzenedicarboxylic acid esters,
as ligands for the formation of complexes with Tb(III) ion.
This paper deals with the synthesis of banana-like
compounds containing a methoxy group in lateral
fragments of the molecules, study of their meso-
morphism, and examination of the possibility of the
formation of luminescent Tb(III) complexes with these
compounds.
EXPERIMENTAL
1,3-Dihydroxybenzene esters X–XIII were
prepared following Scheme 1. The first step was the
synthesis of 1,3-dihydroxybenzene monomethyl ether
II using dimethyl sulfate as alkylating agent. Then the
aldehyde group was introduced by Vilsmeier formyla-
tion with dimethylformamide and phosphorus oxy-
chloride, performed on cooling.
Because the reaction yielded two products, 4-hyd-
roxy-2-methoxybenzaldehyde III and its isomer, 2-hyd-
roxy-4-methoxybenzaldehyde, the procedure was modi-
fied to ensure their separation. Nevertheless, the yield
of III did not exceed 20%. The subsequent acylation of
4-hydroxy-2-methoxybenzaldehyde III and 4-hyd-
roxy-3-methoxybenzaldehyde IV was performed with
the corresponding 4-alkoxybenzoyl chlorides V in an-
hydrous pyridine.
The structures of VIa and VIb were confirmed by
IR spectroscopy. Along with the band at ~1680 cm–1,
assigned to stretching vibrations of the aldehyde
carbonyl group, a band of stretching vibrations of the
ester carbonyl group appears at ~1720 cm–1. The band
characteristic of stretching vibrations of the ether bond
С–О–С appears at ~1240 cm–1. The aldehydes
prepared, VIa and VIb, do not exhibit mesomorphic
properties, which is caused by distortion of the
978

SYNTHESIS OF BANANA-LIKE 1,3-DIHYDROXYBENZENE
979
Scheme 1.
OCH3
CH3O
HO
O
O
H
DMF, POCl3
(CH3)2SO4
HO
H
HO
OH
HO
OCH3
III
IV
I
II
O
H2n+1CnO
Cl
V
11
12
10
Y
X
3
O
O
Y
X
O
O
CrO3
CH3COOH
4
9
O
H2n+1CnO
O
H
H2n+1CnO
8
5
14
13
2
7
1 OH
6
VII
VIa, VIb
4
6
O
9
8
10
1
7
3
O
O
OH
2
16
19
HO
OH
15
13
17
14
11
O
12
VIII
20
18
C8H17O
IX
DMAP
O
O
9
Z
8
10
7
O
O
O
O
16
17
13
15
14
O
11
X
X'
O
12
Y
Y'
20
18
H2n+1CnO
OCnH2n+1
19
X = X' = OCH3, Y = Y' = H, Z = C6H4, n = 8 (X); X = X' = H, Y = Y' = OCH3, Z = C6H4, n = 10 (XI); X = X' = H, Y = Y' =
OCH3, Z = C10H6, n = 12 (XII); X = Y = H, X' = OCH3, Y' = H, Z = C6H4, n = 8 (XIII).
geometric anisotropy of the molecule on introduction
of a bulky lateral substituent, methoxy group.
requires elevated temperature and takes longer time.
The structures of 4-(4-octyloxy-benzoyloxy)-2-methoxy-
benzoic acid VIIa and 4-(4-alkoxybenzoyloxy)-3-
methoxy-benzoic acids VIIb and VIIc were deter-
mined from the 1Н NMR spectra.
4-(4-Alkoxybenzoyloxy)-2(3)methoxybenzaldehydes
VIa and VIb were oxidized to the corresponding acids
VIIa and VIIb with the Jones reagent in acetone [6]. It
should be noted that the oxidation of 4-(4-n-
octyloxybenzoyloxy)-2-methoxybenzaldehyde VIa
4-(4-Octyloxybenzoyloxy)-2-methoxybenzoic acid
VIIa showed no mesomorphic properties, whereas
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 6 2011

980
NOVIKOVA et al.
Scheme 2.
O
6
5
O
C8H17O
4
1
O
HO
2
3
VIIa
MeO
O
O
5
6
O
HO
O
OCnH2n+1
H2n+1CnO
1
4
O
O
OH
2
3
MeO
OMe
VIIb
acids VIIb and VIIc containing the methoxy group in
the 3-position formed a nematic mesophase at lower
temperatures than did their unsubstituted analogs [7].
XII by polarization microscopy show that they exhibit
no mesomorphism. The spectral characteristics, yields,
and melting points of the final diesters are given in the
table.
The phase transition temperatures for 4-(4-de-
cyloxybenzoyloxy)-3-methoxybenzoic acid VIIb are
as follows (°C): crystal (Cr) → isotropic liquid (I)
141.1, I → nematic mesophase (N) 136.6, N → Cr
117.8. The nematic phase is formed on cooling from
the isotropic liquid, i.e., it is monotropic. With the
extension of the terminal alkoxy group to 12 C atoms
(compound VIIc), the mesophase becomes enan-
tiotropic, i.e., it is detected in the course of both
heating and cooling. The phase transition temperatures
for VIIc are as follows (°С): Cr → N 120, N → I
137.8, I → N 137.2, N → Cr 98.
Mixing a methanol solution of terbium trichloride
[Тb(III) concentration 1 × 10–5 M] and a benzene
solution of ligands X–XIII (ligand concentration 1 ×
10–4 M) led to the formation of luminescent complexes
(see figure).
The lowest luminescence intensity was observed
with the diester of 1,3-dihydroxybenzene and 4-(4-
octyloxybenzoyloxy)-2-methoxybenzoic acid X. The
shift of the methoxy group to the 3-position of the
aromatic ring of the intermediate acid (compound XI)
led to an increase in the luminescence intensity by a
factor of 3. Replacement of the central benzene ring by
the naphthalene ring did not affect noticeably the
luminescence intensity (compound XII). The
complexation with ligand X could be prevented by a
steric factor (close arrangement of two bulky
substituents). To check this assumption, we syn-
thesized unsymmetrical banana-like resorcinol ester
XIII containing a methoxy group only in one lateral
fragment (Scheme 1). 3-[4-(4-Octyloxybenzoyloxy)
benzoyloxy]-1-hydroxybenzene IX was synthesized by
the reaction of chloride V with a fourfold excess of
resorcinol in dry benzene and absolute pyridine as an
agent for binding HCl, following the procedure
described in [8]. The final 3-[4-(4-octyloxybenz-
oyloxy)benzoyloxy]-1-[4-(4-octyloxybenzoyloxy)-2-
methoxybenzoyloxy]benzene XIII was synthesized by
the carbodiimide method. The structure of XIII was
The lack of mesomorphism of VIIa can be attri-
buted to the formation of an intramolecular hydrogen
bond between the carboxyl proton and oxygen atom of
the methoxy group, which prevents formation of
dimers and restoration of the geometric anisotropy of
the molecule. The presence of an intramolecular
hydrogen bond is confirmed by the IR data (νОН
=
3500 cm–1). When the methoxy group is in the m-
position relative to the carboxy group (acid VIIb), the
intramolecular hydrogen bonding is impossible, and
dimers are formed via intermolecular hydrogen
bonding (νОН = 3050 cm–1), as shown in Scheme 2.
The final banana-like esters of the synthesized acids
and 1,3-dihydroxybenzene (X, XI, XIII) and 2,7-
dihydroxynaphthalene (XII) were prepared by the
carbodiimide procedure in anhydrous methylene
1
chloride. Their structure was proved by Н NMR
1
spectroscopy. The results of examining compounds X–
determined from the Н NMR data. Examination by
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 6 2011

SYNTHESIS OF BANANA-LIKE 1,3-DIHYDROXYBENZENE
981
Properties of 1,3-dihydroxybenzene and 2,7-dihydroxynaphthalene esters X–XIII
Found, %
Comp. Yield,
no.
1Н NMR spectrum, δ, ppm (СDCl3; 300 MHz)
Calculated, %
Т, °С
Formula
%
C
H
X
67.8 106.0
71.27
71.39
6.80
6.64
C52H58O12 0.90 t (6Н, СН3), 1.22–1.55 m (20Н, СН2 ), 1.77–1.89 m
(4Н, СН2СН2О), 3.95 s (6Н, ОСН3), 4.09 t (4Н, ОСН2),
6.90–7.06 m (8Н, Н10,12,17,19), 7.13–7.21 m (3Н, Н2,4,6), 7.48 t
(1Н, Н5), 8.09–8.20 m (6Н, Н9,16,20
)
XI
70.0
28.0
99.5
73.17
73.02
7.34
7.50
C60H74O12 0.92 t (6Н, СН3), 1.25–1.45 m (24Н, СН2 ), 1.47–1.56 m
(4Н, СН2СН2СН2О), 1.81–1.90 m (4Н, СН2СН2О), 3.94 br.s
(6Н, ОСН3 ), 4.08 t (4Н, СН2О), 7.01 d (4Н, Н17,19), 7.19–
7.25 m (3Н, resorcinol Н – 2,4,6,), 7.32 d (2Н, Н12), 7.53 t
(1Н, resorcinol Н5), 7.85 d (2Н, Н9), 7.91, 7.93 d.d (2Н, Н13),
glass
8.19 d (4Н, Н16,20
)
XII
71.0
74.31
74.13
7.20
7.33
C64H76O12 0.89 t (3Н, СН3 ), 1.55–1.20 m (36Н, СН2), 1.89–1.77 m
(4Н, СН2СН2О), 3.95 br.s (6Н, ОСН3), 4.05 t (4Н, СН2О),
6.99 d (4Н, Н19,21), 7.32 d (2Н, Н14), 7.39, 7.36 d.d (2Н,
Н3,6), 7.70 d (2Н, Н1,8), 8.00–7.85 m (6Н, 2Н4,5, 4Н11,15), 8.17
d (4Н, Н18,22
)
XIII
50.0 135.6
72.32
72.51
6. 80
6.63
C51H56O11 0.90 t (6Н, СН3), 1.23–1.55 m (20Н, СН2), 1.77–1.88 m (4Н,
СН2СН2О), 3.95 s (3Н, ОСН3), 4.05 t (4Н, ОСН2), 6.9–7.02
m (6Н, Н10,12,17,19,17',19'), 7.13–7.22 m (3Н, Н2,4,6), 7.37 d (2Н,
Н10',12'), 7.48 t (1Н, Н5), 8.09–8.20 m (5Н, Н 9,16,16',20,20'), 8.28
d (2Н, Н9',13'
)
polarization microscopy showed that the compound
had no mesomorphic properties. The intensity of the
luminescence of the complex of unsymmetrical
banana-like compound XIII with terbium(III) chloride
was 26 rel. units. For comparison, we show in the
figure the luminescence intensity for the previously
prepared [5] 4-methoxy-1,3-bis[4-(4-decyloxyphen-
oxycarbonyl)phenoxycarbonyl]benzene XIV contain-
ing the methoxy group in the 4-position of the central
aromatic ring.
form : acetone = 5 : 2. The phase transition tempera-
tures of the synthesized compounds were determined
by polarization microscopy with a POLAM R-312
microscope.
4-Alkoxybenzoyl chlorides V were synthesized by
the standard procedure [9]. 3-[4-(4-Octyloxybenzoyl-
oxy)benzoyloxy]-1-hydroxybenzene IX was syn-
thesized by the procedure described in [8].
EXPERIMENTAL
1
The Н NMR spectra of 5–10% solutions of the
compounds were recorded with a Varian VXR-300
spectrometer operating at 300 MHz, and the IR
spectra, with a Specord ІR-75 spectrophotometer
(CНCl3 solutions). The luminescence spectra were
recorded with an SDL-1 spectrometer. The
luminescence was excited with the light of a DRSh-
250 mercury quartz lamp. Radiation with wavelengths
of 313 and 365 nm was cut out using light filters. The
purity of the compounds prepared was evaluated by
TLC on Silufol UV-254 plates in the system chloro-
XII
X
XIII
XI
XIV
Intensity I of the luminescence of lanthanide complexes in
relation to the ligand structure. X–XIII: methoxy group in
lateral fragments of the molecule; XIV: methoxy group in
the central aromatic ring.
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982
NOVIKOVA et al.
3-Methoxyphenol II. To 18.1 g (0.164 mol) of re-
chloride V was added with stirring over a period of 10
min. After adding the whole amount of V, a dense
white precipitate formed throughout the solution
volume. Then 30 ml of alcohol was added, and the
precipitate was filtered off, washed with alcohol (3 ×
25 ml), and dried in air.
4-(4-n-Octyloxybenzoyloxy)-2-methoxybenzalde-
hyde VIa. Yield 55.8%, mp 107°С. IR spectrum
(СНСl3), ν, cm–1: 2925, 2840 (СН2, СН3); 1720 (С=O
ester); 1680 (С=O aldehyde); 1600, 1460 (С–Сarom);
1240 (С–О–С).
4-(4-n-Decyloxybenzoyloxy)-3-methoxybenzalde-
hyde VIb. Yield 86%, mp 68.2°С. IR spectrum
(СНСl3), ν, cm–1: 2930, 2840 (СН2, СН3); 1720 (С=O
ester); 1680 (С=O aldehyde); 1595, 1465 (С–Сarom);
1240 (С–О–С).
4-(4-n-Dodecyloxybenzoyloxy)-3-methoxybenzal-
dehyde VIc. Yield 73%, mp 127.2°С. IR spectrum
(СНСl3), ν, cm–1: 2930, 2835 (СН2, СН3); 1720 (С=O
ester); 1680 (С=O aldehyde); 1595, 1470 (С–Сarom);
1240 (С–О–С).
crystallized 1,3-dihydroxybenzene I, we added with
vigorous stirring 130 ml of a 10% KOH solution. Then
we slowly added dropwise 15.5 ml (0.164 mol) of
dimethyl sulfate, avoiding warm-up of the mixture
above 40°С. After that, the mixture was stirred for 2 h
at room temperature. To bring the reaction to com-
pletion and decompose unchanged dimethyl sulfate,
the mixture was heated on a boiling water bath for 0.5 h.
After cooling, the mixture was acidified with dilute
HCl to pH 6 and extracted with benzene (3 × 100 ml),
and the benzene extract was washed with a 10% NaOH
solution (3 × 200 ml) and with water to pH 7 and was
dried over MgSO4. After removing the solvent, the
residue was transferred into a distillation flask and
subjected to vacuum fractionation, with collection of
the fraction boiling at 82–86°С/3 mm Hg. Yield
48.3%, nD20 1.5520 (published data [10]: nD20 1.5520).
4-Hydroxy-2-methoxybenzaldehyde III. A four-
necked flask was charged with 7.7 ml (0.1 mol) of
anhydrous dimethylformamide. The flask was cooled
with an ice–salt mixture to –12°С, after which 15.3 g
(0.1 mol) of phosphorus oxychloride was added
dropwise with stirring. Then 12.2 g (0.1 mol) of 3-
methoxyphenol II was slowly added dropwise, with
the cooling continued, so as to keep the temperature no
higher than –5°С. After 2.5 h, the mixture was allowed
to warm up to 15°С. A sample was taken, hydrolyzed
with a sodium hydrocarbonate solution, and subjected
to TLC analysis (chloroform : methanol = 5 : 1),
visualization by UV irradiation. Two spots were ob-
served, suggesting formation of the desired 4-hydroxy-
2-methoxybenzaldehyde III and its isomer, 2-hydroxy-
4-methoxybenzaldehyde. The flask was again cooled
in an ice bath, and finely crushed ice (100 g) was
added with stirring. After the reaction mixture dis-
solved, a 5 N NaOH solution was added until the
solution became alkaline. In the process, brown oil
separated out. The alkaline solution was carefully de-
canted into a beaker, and within 15 min a white flaky
precipitated formed throughout the solution volume.
The precipitate was filtered off, dried, and suspended
in a 1 : 1 mixture of benzene and hexane. The mixture
was heated to reflux. The precipitate was filtered off
and dried. A white powder was obtained, yield 17.8%,
mp 163°С (published data [11]: mp 154–156°С).
4-(4-Octyloxybenzoyloxy)-2-methoxybenzoic acid
VIIa. To a suspension of 3.5 g (0.009 mol) of acylated
aldehyde VIa in 50 ml of anhydrous acetone, we added
with stirring a solution of 2.32 g of chromic anhydride
in 2.4 ml of concentrated H2SO4 and 7.2 ml of water.
The mixture was stirred for 1.5 h at room temperature
and then for 2 h at 40°С and left overnight. After that,
300 g of crushed ice was added, the mixture was
stirred for 0.5 h, and, after thawing, the fine colorless
precipitate was filtered off. The precipitate was washed
with water on the filter (3 × 50 ml) and dried. Yield
1
61%, mp 128°С. Н NMR spectrum, δ, ppm (CDCl3,
300 MHz): 0.87 t (3Н, СН3), 1.20–1.50 m (10Н, СН2),
1.67–1.82 m (2Н, СН2СН2О), 3.82 s (3Н, ОСН3), 4.09
t (2Н, ОСН2), 6.91 d (1Н, 6-Н), 7.07 m (3Н, 4,11,13-
Н), 7.75 d (1Н, 3-Н), 8.07 d (2Н, 10,14-Н).
4-(4-Decyloxybenzoyloxy)-3-methoxybenzoic acid
VIIb was prepared similarly, crystallized from alcohol,
1
and dried. Yield 57.4%. Н NMR spectrum, δ, ppm
(DMSO, 500 MHz): 0.88 t (3Н, СН3), 1.21–1.38 m
(12Н, СН2), 1.39–1.48 m (2H, CH2СН2СН2О), 1.71–
1.80 m (2Н, СН2СН2О), 3.84 s (3Н, ОСН3), 4.10 t
(2Н, ОСН2), 7.12 d (1Н, 11,13-H), 7.36 d (1Н, 6-Н),
7.61–7.69 m (2Н, 3,7-H), 8.07 d (2Н, 10,14-H).
4-(4-Dodecyloxybenzoyloxy)-3-methoxybenzoic
acid VIIc was prepared similarly, recrystallized from
alcohol, and purified by column chromatography
(aluminum oxide L 40/250, eluent methylene chloride :
4-(4-Alkoxybenzoyloxy)-2-(and 3-)methoxybenz-
aldehydes VIa–VIc. Aldehyde III or IV (17.8 mmol)
was dissolved in 15 ml of anhydrous pyridine, after
which 16.8 mmol of appropriate 4-alkoxybenzoyl
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SYNTHESIS OF BANANA-LIKE 1,3-DIHYDROXYBENZENE
983
methanol = 10 : 1). The solvent was distilled off at re-
duced pressure, and the residue was washed with dry
group in lateral fragments of the banana-like molecules
leads to the lack of mesomorphism, whereas
intermediate 4-(4-alkoxybenzoyloxy)-3-methoxybenzoic
acids form a nematic mesophase.
(2) The luminescence of terbium(III) complexes of
the 1,3-dihydroxybenzene esters becomes more intense
when the methoxy group in the aromatic ring of the
lateral fragment is shifted from the 2-position to the 3-
position.
(3) The luminescence of the terbium(III) complexes
is the strongest when the methoxy group is present
only in one of the lateral fragments of the banana-like
1,3-dihydroxybenzene ester, which is apparently due to
the absence of steric hindrance to the complexation.
1
hexane. Yield 30%, М+ 456. Н NMR spectrum, δ,
ppm (DMSO, 300 MHz): 0.85 t (3Н, СН3), 1.1–1.5 m
(18Н, СН2), 1.67–1.83 m (2Н, СН2СН2О), 3.82 s (3Н,
ОСН3), 4.08 t (2Н, ОСН2), 7.12 d (1Н, 11,13-H), 7.34
d (1Н, 6-Н), 7.62–7.68 m (2Н, 3,7-H), 8.05 d (2Н,
10,14-H).
Bis-1,3-[4-(4-octyloxybenzoyloxy)-2-methoxybenz-
oyloxy]benzene X. A mixture of 1.075 g (2.7 mmol)
of acid VIIa, 0.18 g (1.63 mmol) of 1,3-dihyd-
roxybenzene I, and 36 mg (0.3 mmol) of dimethyl-
aminopyridine (DMAP) in 25 ml of anhydrous me-
thylene chloride was stirred for 10 min, after which
0.62 g (3 mmol) of dicyclohexylcarbodiimide (DCC)
was added, and the mixture was stirred for 7 h and left
overnight. The solvent was removed at reduced
pressure, and alcohol was added to the residue to
induce crystallization. The precipitate was filtered off,
washed with alcohol (3 × 30 ml), and dried.
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benzoyloxy]naphthalene XII was prepared similarly.
3-[4-(4-Octyloxybenzoyloxy)benzoyloxy]-1-[4-(4-
octyloxybenzoyloxy)-2-methoxybenzoyloxy]benzene
XIII was prepared similarly from 0.475 g (1.19 mmol)
of 4-(4-octyloxybenzoyloxy)-3-methoxybenzoic acid
VIIa, 0.548 g (1.19 mmol) of monoacylated phenol
IX, 0.268 g (1.3 mmol) of DCC, and 0.03 g (0.13 mmol)
of DMAP. The product was crystallized from the
alcohol : benzene = 3 : 1 mixture.
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khin, A.A., Ed., Leningrad: Khimiya, 1984.
(1) Previously unknown esters of 1,3-dihyd-
roxybenzene and 2,7-dihydroxynaphthalene with 4-(4-
alkoxybenzoyloxy)-2(3)-methoxybenzoic acids were
synthesized, and their capability to form liquid crystals
was examined. The presence of the bulky methoxy
11. US Patent 6512100.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 6 2011