Synthesis and properties of luminophores derived from fluorinated biphenyls

Article abstract of DOI:10.1134/S1070428008080113

A procedure was developed for the synthesis of dimethyl 2-fluoro-and 2,2′-difluorobiphenyl-4,4′-dicarboxylates. The latter were converted into fluorinated 4,4′-bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]-and 4,4′-bis[5-(4-octyloxyphenyl)-1,3,4-oxadiazol-2-yl]biphenyls which showed strong luminescence in the crystalline state and in solution; their spectral properties were examined.

Full text of DOI:10.1134/S1070428008080113

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 8, pp. 1172–1179. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.K. Ol’khovik, A.A. Pap, V.A. Vasilevskii, N.A. Galinovskii, S.N. Tereshko, 2008, published in Zhurnal Organicheskoi Khimii,
2008, Vol. 44, No. 8, pp. 1185–1192.
Synthesis and Properties of Luminophores
Derived from Fluorinated Biphenyls
V. K. Ol’khovik, A. A. Pap, V. A. Vasilevskii, N. A. Galinovskii, and S. N. Tereshko
Institute of New Materials Chemistry, National Academy of Sciences of Belarus,
ul. F. Skoriny 36, Minsk, 220141 Belarus
e-mail: slavol@ichnm.basnet.by
Received June 25, 2007
Abstract—A procedure was developed for the synthesis of dimethyl 2-fluoro- and 2,2′-difluorobiphenyl-4,4′-
dicarboxylates. The latter were converted into fluorinated 4,4′-bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]- and
4,4′-bis[5-(4-octyloxyphenyl)-1,3,4-oxadiazol-2-yl]biphenyls which showed strong luminescence in the crystal-
line state and in solution; their spectral properties were examined.
DOI: 10.1134/S1070428008080113
Polyconjugated biphenyl derivatives may be re-
garded as short-chain analogs of polyphenylene-
vinylenes that attract interest as active materials for
light-emitting diodes. Most studies on the synthesis of
such electroluminescent materials were performed on
unsubstituted biphenyls [1, 2]. These compounds are
generally characterized by poor solubility in most or-
ganic solvents and are very prone to undergo crystal-
lization which hampers their use in practice. Therefore,
it seems to be promising to design new short-chain
analogs of polyphenylenevinylenes containing a mod-
ified biphenyl fragment and examine the effect of
substitution in that fragment on physicochemical prop-
erties of such system. Among these, most interesting
are compounds having an asymmetric structure, name-
ly biphenyl-4,4′-dicarboxylic acid derivatives with
electron-donating or electron-withdrawing substituents
in one phenyl ring [3–5].
In our study, the key intermediate compounds for
the synthesis of mono- and difluoro-substituted bi-
phenyl-4,4′-dicarboxylic acid derivatives V and IX
were the corresponding dimethyl 2-amino- and 2,2′-di-
aminobiphenyl-4,4′-dicarboxylates III and VII
(Scheme 1). The latter were prepared in two steps, by
nitration of dimethyl biphenyl-4,4′-dicarboxylate (I)
and subsequent reduction of nitro compounds II and
VI. The optimal nitration procedure was treatment of
a solution of I in concentrated sulfuric acid with a mix-
ture of concentrated sulfuric acid and 58% nitric acid
at a volume ratio of 1:(0.8–1.0). The synthesis of
mononitro derivative II required careful temperature
control. The temperature of the reaction mixture
should not exceed 20°C. Rise in the temperature to
30°C leads to preferential formation of dinitro deriva-
tive VI even using an equimolar amount of nitric acid.
Dinitro derivatives VI was obtained in 70% yield
using 2 equiv of nitric acid, the temperature of the
reaction mixture ranging from 25 to 30°C. Here, the
reaction temperature should also be controlled care-
fully; above 35°C, the reaction was accompanied by
complete hydrolysis of the ester groups. The reduction
of nitro compounds II and VI to the corresponding
amines III and VII with hydrogen was performed in
tetrahydrofuran in the presence of Pd/C as catalyst
either under atmospheric pressure or at a hydrogen
pressure of 10 atm (in a high-pressure reactor). In the
reduction of mononitro derivative II, the yield of
amine III was almost quantitative (93–95%). The
reduction of dinitro compound VI under atmospheric
In the present article we report on the synthesis of
2-fluoro- and 2,2′-difluorobiphenyl-4,4′-dicarboxylic
acids and a series of luminescent dyes based thereon.
It is known that introduction of a fluorine atom into
organic molecules leads to compounds with strongly
different properties due to high electronegativity of the
fluorine atom and its small size. Direct regioselective
fluorination of aromatic systems is very difficult to
accomplish; as a rule, mixtures of isomeric products
are formed, which are difficult to separate. One of the
most convenient regioselective methods for the intro-
duction of fluorine atoms is based on the Balz–
Schieman reaction of diazonium salts [6].
1172

SYNTHESIS AND PROPERTIES OF LUMINOPHORES
1173
Scheme 1.
NO2
MeO
O
O
MeO
O
O
HNO3, H2SO4
85%
OMe
OMe
I
II
NH2
N2 ·BF4
MeO
O
O
MeO
O
O
H2, Pd/C
NaNO2, HBF4
92%
95%
OMe
OMe
III
IV
F
MeO
O
Δ
85%
O
OMe
V
NO2
NH2
MeO
O
O
MeO
O
O
HNO3, H2SO4
70%
H2, Pd/C
85%
I
OMe
OMe
O2N
H2N
VI
VII
N2 ·BF4
F
MeO
O
O
MeO
O
NaNO2, HBF4
95%
Δ
44%
OMe
O
OMe
N2 ·BF4
VIII
F
IX
pressure was accompanied by side processes, and the
maximal yield of amine VII (85%) was attained when
the hydrogenation was carried out under pressure.
Diazomiun salts IV and VIII were obtained by nitrosa-
tion of the corresponding amine hydrochlorides with
a solution of sodium nitrite in 15% hydrochloric acid,
followed by treatment with a 40% solution of tetra-
fluoroboric acid. Diazonium tetrafluoroborates IV and
VIII were thoroughly dried over phosphorus(V) oxide
prior to thermal decomposition [7]. Introduction of
fluorine atoms into the biphenyl fragment of molecule
I resulted in lowering of the melting point by 60°C, the
effect being the strongest for monofluoro derivative V
with distorted molecular symmetry. Unlike initial
diester I, fluorinated biphenyls V and IX are readily
soluble in most organic solvents.
In the recent time, extensive studies are performed on
poly-p-phenylene analogs having an electron-with-
drawing heterocyclic fragment in the side and/or prin-
cipal conjugation chain; this fragment is responsible
for electron-transport properties of the molecule. Such
compounds can be used as electron-active components
of organic light-emitting diodes [8–10]. It is known
that oxazole and oxadiazole heterocycles are strong
electron withdrawers and that dyes based thereon are
very stable [11]. Using fluorinated biphenyls V and IX
as starting compounds we synthesized a series of new
short-chain analogs of poly-p-phenylenes and poly-p-
phenylenevinylenes containing 1,3,4-oxadiazole and
1,3-benzoxazole fragments in the principal conjugation
chain. For the sake of comparison, we also synthesized
analogous fluorine-free derivatives from unsubstituted
biphenyldicarboxylate I (Scheme 1).
Due to the presence of two carboxy groups fluori-
nated biphenyls V and IX are convenient starting com-
pounds for the synthesis of extended poly-π-conjugat-
ed systems as potential electroluminescent materials.
Dialdehydes XIII–XV were obtained in two steps.
Diesters I, V, and IX were initially reduced to the cor-
responding 4,4′-bis(hydroxymethyl)biphenyls X–XII,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008

OL’KHOVIK et al.
1174
Scheme 2.
R'
R'
R'
O
MeO
O
O
HO
LiAlH4
[O]
95–97%
85–90%
OMe
OH
O
R
R
R
I, V, IX
X–XII
XIII–XV
N
R'
O
Me
O
N
N
O
R
XVI–XVIII
R'
Cl
O
I, V, IX
O
Cl
R
XIX–XXI
R'
HN NH
O
O
4-C8H17OC6H4CONHNH2
98%
C8H17O
OC8H17
O
O
HN NH
R
C8H17
O
R'
N
N
POCl3
O
O
N
N
R
OC8H17
XXII–XXIV
I, X, XIII, XVI, XIX, XXII, R = R′ = H; V, XI, XIV, XVII, XX, XXIII, R = F, R′ = H;
IX, XII, XV, XVIII, XXI, XXIV, R = R′ = F.
and the latter were oxidized to dialdehydes. The reduc-
tion of diesters I, V, and IX was carried out using
lithium tetrahydridoaluminate in tetrahydrofuran. The
reaction with unsubstituted dimethyl biphenyl-4,4′-di-
carboxylate required prolonged heating of the reaction
mixture, while fluoro-substituted compounds were
reduced in 20–30 min at room temperature to give
98% of diols XI and XII. The oxidation of X–XII with
pyridinium chlorochromate in methylene chloride gave
dialdehydes XIII–XV in 85–90% yield. The subse-
quent condensation of dialdehydes XIII–XV with
2-methyl-1,3-benzoxazole was characterized by high
stereoselectivity. The reactions were carried out in di-
methyl sulfoxide in the presence of sodium methoxide
as a base, and the products were exclusively trans,trans
isomers XVI–XVIII (yield up to 85%).
As noted above, the presence of carboxy groups in
positions 4 and 4′ of biphenyl molecule ensures its
easy further functionalization with a view to obtain
rigid extended rod-like polyconjugated systems. For
this purpose, diesters I, V, and IX were converted into
carboxylic acid chlorides XIX–XXI which were
treated with p-octyloxybenzohydrazide to obtain the
corresponding intermediate bis-hydrazides. Cyclization
of the latter gave 1,3,4-oxadiazole derivatives XXII–
XXIV (Scheme 2). As a rule, structurally related linear
molecules having no substituent in the side or principal
chain are very poorly soluble, which prevents them
from being used as electron-active materials in light-
emitting diodes. To obtain readily soluble derivatives
the hydrazide component contained an octyloxy group.
The corresponding bis-hydrazides were formed in
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008

SYNTHESIS AND PROPERTIES OF LUMINOPHORES
1175
almost quantitative yield and were subjected to subse-
quent cyclization without additional purification. The
cyclization was performed by heating with various
dehydrating agents. The best results were obtained by
heating bis-hydrazides in phosphoryl chloride. The
yields of oxadiazoles XXII–XXIV reached 82% (cal-
culated on the initial esters I, V, and IX).
gel 60 F254 (Merck). The melting points were deter-
mined on a Kofler hot stage.
Dimethyl 2-nitrobiphenyl-4,4′-dicarboxylate (II).
A solution of 20 g (74 mmol) of dimethyl biphenyl-
4,4′-dicarboxylate (I) in 200 ml of concentrated sul-
furic acid was cooled to 15°C, and a mixture of 12 ml
(149 mmol) of 58% nitric acid and 15 ml of concen-
trated sulfuric acid was added dropwise over a period
of 40 min under stirring, maintaining the temperature
at 15–20°C. The mixture was then stirred for 1 h at 15–
20°C, diluted with 100 ml of water, and extracted with
ethyl acetate. The extract was washed with water and
a solution of sodium hydrogen carbonate, dried over
anhydrous sodium sulfate, and evaporated, and the res-
idue was recrystallized from isopropyl alcohol. Yield
19.8 g (85%), mp 98–99°C. IR spectrum, ν, cm–1:
3450, 3100, 2960, 1720, 1610, 1530, 1440, 1360,
1310, 1290, 1240, 1120, 1020, 870, 760, 710. 1H NMR
spectrum (CDCl3), δ, ppm: 3.69 s (3H, OMe), 3.94 s
(3H, OMe), 7.55 d (2H, 2′-H, 6′-H, J = 9 Hz), 7.73 d
(1H, 6-H, J = 8 Hz), 8.03 d (2H, 3′-H, 5′-H, J = 9 Hz),
8.27 d.d (1H, 5-H, J1 = 1.5, J2 = 8 Hz), 9.97 d (1H,
3-H, J = 1.5 Hz). Found, %: C 60.56; H 4.06; N 4.32.
C16H13NO6. Calculated, %: C 60.95; H 4.16; N 4.44.
All benzoxazolylethenyl derivatives XVI–XVIII
showed strong luminescence both in the crystalline
state and in solution. Their fluorescence maxima in
solution range from λ 430 to 440 nm, and introduction
of fluorine atoms almost does not change the position
of the fluorescence maxima. A different pattern was
observed for solid-state fluorescence. Crystalline com-
pound XVI displayed strong luminescence with its
maximum at λ 547 nm upon UV excitation at λ 365 nm
[12]. Introduction of fluorine atoms into position 2 of
the biphenyl fragment (compounds XVII and XVIII)
leads to short-wave shift of the fluorescence maximum
(λfl 470–480 nm). The strongest effect was observed
for monofluoro derivative XVII (λ = 473 nm) with
distorted molecular symmetry. Better solubility of
fluorinated compounds XVII and XVIII as compared
to unsubstituted benzoxazole derivative XVI should
also be noted.
Dimethyl 2-aminobiphenyl-4,4′-dicarboxylate
(III). A mixture of 15 g (0.05 mol) of compound II,
500 ml of THF, and 10 g of 5% Pd/C was hydrogenat-
ed for 5 days under vigorous stirring under atmospher-
ic pressure. When hydrogen was no longer absorbed,
the catalyst was filtered off, and the solvent was dis-
tilled off from the filtrate under reduced pressure. The
residue was recrystallized from ethanol. Yield 13.25 g
(93%), mp 176–177°C. IR spectrum, ν, cm–1: 3470,
3380, 2960, 1700, 1620, 1600, 1440, 1400, 1250,
The fluorescence maxima of oxadiazoles XXII–
XXIV in which the electron-withdrawing group is
directly attached to the biphenyl fragment are located
at shorter wavelengths (λ 400–410 nm) for both solid
samples and their solutions. Introduction of fluorine
atoms almost does not affect the position of the solid-
state and solution fluorescence maxima; only a slight
red shift of the emission band is observed (Δλ = 5–
7 nm; λfl 401 and 407 nm for XXII and XXIII,
respectively.
1
1130, 1000, 910, 760. H NMR spectrum (CDCl3), δ,
ppm: 3.39 s (2H, NH2), 3.83 s (3H, OCH3), 3.88 s (3H,
OCH3), 7.17–8.09 m (7H, Harom). Found, %: C 67.29;
H 5.32; N 4.98. C16H15NO4. Calculated, %: C 67.36;
H 5.30; N 4.91.
EXPERIMENTAL
The IR spectra were measured in the range from
400 to 4000 cm–1 on a Specord M-80 spectrometer
from samples pelleted with KBr. The 1H and 13C NMR
spectra were recorded on Bruker Biospin Avance-500
(500 and 125 MHz for 1H and 13C, respectively), Tesla
BS-587A (80 MHz), and Tesla BS-567A (100 MHz)
instruments using tetramethylsilane as internal refer-
ence. The electron-impact mass spectra were obtained
at an energy of ionizing electrons of 70 eV. The sol-
vents and reagents used were purified and dehydrated
by standard methods. The progress of reactions was
monitored by TLC on plastic plates coated with silica
Dimethyl 2-fluorobiphenyl-4,4′-dicarboxylate
(V). A suspension of dimethyl 2-aminobiphenyl-
4,4′-dicarboxylate hydrochloride prepared from 6 g
(21 mmol) of compound III and 20 ml of 15% hydro-
chloric acid was cooled to 0°C, and a solution of 2.2 g
(0.32 mol) of sodium nitrite in 3 ml of water was
added under vigorous stirring. The mixture was stirred
for 10 min at 0°C, 2.8 g (0.31 mol) of HBF4 was
added, and the mixture was stirred for 1 h. The precip-
itate was filtered off, washed with water and ethanol,
and thoroughly dried. The diazonium salt thus ob-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008

OL’KHOVIK et al.
1176
tained, 7.38 g (19 mmol), was placed into a flask con-
nected to a gas-washing bottle filled with a 10% solu-
tion of sodium hydroxide, and the flask was heated
with a stream of air heated to 300°C. When evolution
of white smoke ceased, the melt was heated for an ad-
ditional 1 min. The melt was cooled and dissolved in
200 ml of toluene, the hot solution was filtered through
a layer of silica gel, and the sorbent was additionally
washed with hot toluene (4×50 ml). The solvent was
removed under reduced pressure, and the residue was
recrystallized from 100 ml of isopropyl alcohol. Yield
4.65 g (85%), mp 142.5–143°C (from hexane). IR
spectrum, ν, cm–1: 3430, 3050, 2980, 1720, 1610,
filtration, and the solvent was distilled off from the
filtrate under reduced pressure. The crude product was
dissolved in 50 ml of toluene on heating, the solution
was passed through a layer of silica gel, the solvent
was distilled off, and the residue was recrystallized
from ethanol. Yield 3.4 g (84%), mp 170–171°C. IR
spectrum, ν, cm–1: 3450, 3370, 3900, 1700, 1620,
1560, 1510, 1490, 1440, 1420, 1310, 1240, 1200, 1120,
1
1000, 980, 890, 765. H NMR spectrum (CDCl3), δ,
ppm: 3.5 s (4H, NH2), 3.9 s (6H, OCH3), 7.1–7.53 m
(6H, Harom). Mass spectrum, m/z (Irel, %): 300 [M]+
(100), 299 [M – 1]+, (55), 285 [M – NH2 + H]+ (10),
268 [M – 2NH2]+, 253 [C15H9O4]+ (21), 241 (11), 182
(12). Found, %: C 63.90; H 5.43; N 9.21. C16H16N2O4.
Calculated, %: C 63.99; H 5.37; N 9.33. M 300.31.
1
1430, 1400, 1290, 1210, 1110, 770, 700. H NMR
spectrum (CDCl3), δ, ppm: 3.89 s (3H, OCH3), 3.89 s
(3H, OCH3), 7.46 t (1H, J = 8 Hz), 7.58 d.d (2H, J1 =
1.5, J2 = 8.5 Hz), 7.76 d.d (1H, J1 = 1.5, J2 = 11 Hz),
7.84 d.d (1H, J1 = 1.5, J2 = 8 Hz), 8.06 d (2H, J =
8.5 Hz). Found, %: C 66.49; H 4.47; F 6.52.
C16H13FO4. Calculated, %: C 66.66; H 4.55; F 6.59.
Dimethyl 2,2′-difluorobiphenyl-4,4′-dicarbox-
ylate (IX). A suspension of 500 mg of finely powdered
compound VII in 5 ml of 20% hydrochloric acid was
cooled to 0°C, and a solution of 0.3 g of sodium nitrite
in 3 ml of water was added dropwise under stirring,
maintaining the temperature at 0 to 5°C. The precip-
itate was filtered off, washed with water and alcohol,
and dried under reduced pressure. The diazonium salt
thus obtained, 700 mg, was heated in a round-bottom
flask to initiate exothermic reaction. The residue was
extracted with hot toluene, the solvent was distilled off
from the extract, and the crude product was purified by
column chromatography on silica gel using methylene
chloride as eluent. Yield 210 mg (41%), mp 139.5°C.
IR spectrum, ν, cm–1: 1720, 1560, 1490, 1430, 1400,
1300, 1250, 1200, 1130, 1100, 980, 900, 850, 800,
Dimethyl 2,2′-dinitrobiphenyl-4,4′-dicarboxylate
(VI). A solution of 20 g (74 mmol) of dimethyl
biphenyl-4,4′-dicarboxylate in 200 ml of concentrated
sulfuric acid was heated to 35°C, a mixture of 24.2 ml
of 58% nitric acid and 25 ml of concentrated sulfuric
acid was added dropwise under stirring over a period
of 40 min, and the mixture was stirred for 1 h, main-
taining the temperature at 35–40°C. The mixture was
diluted with 100 ml of water and extracted with ethyl
acetate, and the extract was washed with water and
a saturated solution of sodium hydrogen carbonate and
dried over anhydrous sodium sulfate. The solvent was
distilled off under reduced pressure, and the residue
was recrystallized from isopropyl alcohol. Yield 18.76 g
(70%), mp 155°C. IR spectrum, ν, cm–1: 2960, 2930,
2850, 2730, 1700, 1600, 1590, 1560, 1430, 1380,
1310, 1290, 1270, 1240, 1210, 1170, 1150, 1000, 840,
1
760. H NMR spectrum (CDCl3), δ, ppm: 3.96 s (6H,
OCH3), 7.48–7.51 m (2H, Harom), 7.84–7.86 m (2H,
Harom), 7.92 d.d (2H, Harom, J1 = 8, J2 = 1.5 Hz). Found,
%: C 62.93; H 4.03; F 12.34. C16H12F2O4. Calculated,
%: C 62.75; H 3.95; F 12.41.
1
810, 700, 730. H NMR spectrum (CDCl3), δ, ppm:
Biphenyl-4,4′-diyldimethanol (X). Dimethyl
biphenyl-4,4′-dicarboxylate (I), 27 g (0.1 mol), was
added in portions under continuous stirring to a sus-
pension of 4.2 g (0.11 mol) of lithium tetrahydrido-
aluminate in 150 ml of anhydrous tetrahydrofuran. The
mixture was heated for 2 h under reflux, cooled to
room temperature, and carefully treated first with
water and then with a 10% solution of sulfuric acid.
The organic phase was separated by decanting, and
the aqueous phase was extracted with ethyl acetate
(3×50 ml). The extracts were combined with the or-
ganic phase and dried over anhydrous sodium sulfate,
the solvent was distilled under reduced pressure, and
the residue was recrystallized from ethanol. Yield 90%,
3.80 s (6H, OCH3), 7.67 d (2H, 6-H, 6′-H, J = 8 Hz),
8.36 d.d (2H, 5-H, 5′-H, J1 = 1.6, J2 = 8 Hz), 8.66 d
(2H, 3-H, 3′-H, J = 1.4 Hz). Mass spectrum, m/z
(Irel, %): 360 [M]+ (15), 330 [M – 2CH3]+ (15), 329
[M – 2CH3 – H]+ (78), 314 [M – OCH3 – CH3]+ (100).
Found, %: C 53.41; H 3.31; N 7.85. C16H12N2O8. Cal-
culated, %: C 53.34; H 3.36; N 7.78.
Dimethyl 2,2′-diaminobiphenyl-4,4′-dicarbox-
ylate (VII). A mixture of 5 g (14 mmol) of compound
VI, 100 ml of acetic acid, and 10 g of 5% Pd/C in
a high-pressure reactor was hydrogenated at 30°C and
a hydrogen pressure of 3–10 atm until hydrogen was
no longer absorbed. The catalyst was separated by
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SYNTHESIS AND PROPERTIES OF LUMINOPHORES
1177
1
mp 191–192°C. H NMR spectrum (CDCl3), δ, ppm:
ing and was passed through a layer of silica gel. The
residue (a dark brown material containing the oxidant)
was dissolved in a 10% solution of sodium hydroxide,
and the solution was extracted with toluene. The ex-
tracts were combined with the organic phase, washed
with water until neutral reaction, and dried over
MgSO4. The solvent was distilled off, and the residue
was recrystallized from ethanol. Yield 82%, mp 139–
4.54 d (4H, CH2O, J = 5 Hz), 5.22 t (2H, OH, J =
5 Hz), 7.39 d (4H, 2-H, 2′-H, 6-H, 6′-H, J = 8 Hz),
7.61 d (4H, 3-H, 3′-H, 5-H, 5′-H, J = 8 Hz). Found, %:
C 78.27; H 6.46. C14H14O2. Calculated, %: C 78.48;
H 6.59.
2-Fluorobiphenyl-4,4′-diyldimethanol (XI). A so-
lution of 576 mg (2 mmol) of diester V in 10 ml of
THF was added under vigorous stirring to a suspension
of 400 mg (10 mmol) of lithium tetrahydridoaluminate
in 40 ml of THF. The mixture was stirred for 30 min at
room temperature, and excess LiAlH4 was quenched
by treatment with 10 ml of ethyl acetate. The mixture
was then treated with a 15% solution of sodium
hydroxide until a dense precipitate of aluminum oxide
was formed. The precipitate was filtered off and
washed with hot THF (2 ×15 ml). The filtrate was
evaporated, the residue was dissolved in THF, and the
solution was passed through a layer of silica gel. Yield
452 mg (99%), mp 132–133°C (from aqueous ethanol,
1:1). IR spectrum, ν, cm–1: 3250, 3050, 2930, 1490,
1430, 1400, 1360, 1290, 1270, 1210, 1130, 1040,
1020, 810. 1H NMR spectrum (CDCl3), δ, ppm: 4.53 d
(4H, J = 11 Hz), 5.10 t (1H, J = 11 Hz), 5.22 t (1H, J =
11 Hz), 7.16 m (2H, Harom), 7.38 m (2H, Harom),
7.45 d.d, (2H, J1 = 8, J2 = 1.5 Hz). Found, %: C 72.54;
H 5.51; F 8.31. C14H13FO2. Calculated, %: C 72.40;
H 5.64; F 8.18.
1
141°C. H NMR spectrum (CDCl3), δ, ppm: 7.78 d
(4H, 2-H, 2′-H, 6-H, 6′-H, J = 8 Hz), 8.00 d (4H, 3-H,
3′-H, 5-H, 5′-H, J = 8 Hz), 10.08 s (2H, CHO). Found,
%: C 80.21; H 4.66. C14H10O2. Calculated, %: C 79.98;
H 4.79.
2-Fluorobiphenyl-4,4′-dicarbaldehyde (XIV).
A solution of 2.6 g (12 mmol) of pyridinium chloro-
chromate in dioxane was added under continuous
stirring to a solution of 684 mg (3 mmol) of compound
XI in a mixture of 25 ml of methylene chloride and
10 ml of dioxane. The mixture was stirred for 20 h at
room temperature, the progress of the reaction being
monitored by TLC. Excess oxidant was decomposed
by treatment with 10 ml of isopropyl alcohol, the mix-
ture was stirred for 20 min and filtered through a layer
of silica gel, the filtrate was evaporated, the residue
was dissolved in 50 ml of methylene chloride, and the
mixture was filtered through a layer of silica gel. The
solvent was distilled under reduced pressure, and the
residue was recrystallized from ethanol. Yield 605 mg
(90%), mp >130°C (decomp.). IR spectrum, ν, cm–1:
3060, 2840, 2750, 1690, 1600, 1580, 1560, 1490,
1440, 1410, 1390, 1300, 1270, 1250, 1210, 1180,
1150, 1130, 1010, 970, 890, 840, 820, 790, 760, 740,
2,2′-Difluorobiphenyl-4,4′-diyldimethanol (XII).
Lithium tetrahydridoaluminate, 0.2 g (5.21 mmol), was
added to a solution of 1 g (3.26 mmol) of compound
IX, and the solution was stirred for 6 h on heating
under reflux. The mixture was treated with 1 ml of
a 10% solution of sodium hydroxide, the precipitate
was filtered off, the filtrate was evaporated under
reduced pressure, and the residue was recrystallized
from ethanol. Yield 0.80 g (98%). IR spectrum, ν,
cm–1: 3110, 2940, 1620, 1560, 1500, 1410, 1270, 1240,
1
720, 660. H NMR spectrum (CDCl3), δ, ppm: 7.67 t
(1H, 6-H, J = 7.5 Hz), 7.72 d (1H, 3-H, J = 10 Hz),
7.77 d (2H, 6′-H, 2′-H, J = 7.5 Hz), 7.8 d (1H, 5-H,
J = 8 Hz), 8.0 d (1H, 5′-H, 3′-H, J = 7.5 Hz), 10.05 s
(1H, CHO), 10.1 s (1H, CHO). Found, %: C 73.87;
H 4.12; F 8.45. C14H9FO2. Calculated, %: C 73.68;
H 3.97; F 8.32.
1
1130, 1050, 830. H NMR spectrum (CDCl3), δ, ppm:
2,2′-Difluorobiphenyl-4,4′-dicarbaldehyde (XV).
A solution of 2.2 g (10 mmol) of pyridinium chloro-
chromate in 10 ml of dioxane containing 1 ml of water
was added dropwise to a solution of 0.83 g
(3.32 mmol) of compound XII in 30 ml of methylene
chloride. The mixture was stirred for 12 h (TLC) and
passed through a layer of silica gel, the solvent was
removed under reduced pressure, and the residue was
recrystallized from alcohol. Yield 0.6 g (73%),
mp 150°C (decomp.). IR spectrum, ν, cm–1: 3100,
2910, 1670, 1600, 1550, 1410, 1370, 1260, 1240,
1210, 1140, 1110, 1000, 950, 880, 800, 760, 730.
4.55 d (4H, CH2, J = 5 Hz), 5.33 t (2H, OH, J = 5 Hz),
7.17–7.21 m (4H, Harom), 7.32 m (2H, Harom). Found,
%: C 67.39; H 4.82; F 15.27. C14H12F2O2. Calculated,
%: C 67.20; H 4.83; F 15.18
Biphenyl-4,4′-dicarbaldehyde (XIII). Compound
X, 2.14 g (0.01 mol), was dissolved in 60 ml of di-
chloroethane, 15.8 ml of pyridinium chlorochromate in
dioxane was added under vigorous stirring, and the
mixture was stirred for 3 h at room temperature. The
mixture was then diluted with 50 ml of dioxane, the
solution was separated from the precipitate by decant-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008

OL’KHOVIK et al.
1178
1H NMR spectrum (CDCl3), δ, ppm: 7.60–7.64 m
(2H, Harom), 7.70–7.74 m (2H, Harom), 7.79–7.82 m
(2H, Harom), 10.07 s (2H, CHO). Found, %: C 68.37;
H 4.82; F 15.51. C14H8F2O2. Calculated, %: C 68.30;
H 3.15; F 15.43.
1520, 1480, 1470, 1450, 1405, 1340, 1310, 1270,
1240, 1225, 1170, 1140, 1010, 970, 960, 940, 930,
870, 860, 850, 810, 790, 730, 720. H NMR spectrum
(CDCl3), δ, ppm: 7.37–7.40 m (4H, Harom), 7.41 d (2H,
CH=CH, J = 17 Hz), 7.54–7.57 m (2H, Harom), 7.69–
7.71 m (2H, Harom), 7.72–7.74 m (2H, Harom), 7.74–
7.75 m (2H, Harom), 7.80–7.83 m (2H, Harom), 7.86 d
(2H, CH=CH, J = 17 Hz). Found, %: C 75.46; H 3.77;
F 8.12; N 5.69. C30H18F2N2O2. Calculated, %: C 75.62;
H 3.81; F 7.97; N 5.88.
1
4,4′-Bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]bi-
phenyl (XVI). A solution of sodium methoxide
prepared from 540 mg of metallic sodium and 5 ml of
methanol was added to a solution of 1.05 g (5 mmol)
of dialdehyde XIII and 1.4 g (10 mmol) of 2-methyl-
1,3-benzoxazole in 50 ml of DMSO. The mixture was
heated to 55–60°C, stirred for 6 h at that temperature,
and cooled to room temperature, and the precipitate
was filtered off, washed with ethanol and acetone,
dried, and recrystallized from DMSO. Yield 1.85 g
(84%), mp 317°C. IR spectrum, ν, cm–1: 3060, 3040,
1640, 1530, 1450, 1410, 1350, 1310, 1290, 1280,
1240, 1190, 1160, 1150, 1010, 970, 940, 870, 840, 810,
Biphenyl-4,4′-dicarbonyl dichlorides XIX–XXI
(general procedure). A mixture of 3.3 mmol of dimeth-
yl biphenyl-4,4′-dicarboxylate I, V, or X, 25 mmol of
sodium hydroxide, and 50 ml of 90% ethanol was
heated for 1 h under reflux. The mixture was cooled to
room temperature, 50 ml of 10% hydrochloric acid
was added, and the precipitate was filtered off and
dried in a vacuum desiccator over phosphoric anhy-
dride. The crude product was mixed with 10 ml of
thionyl chloride, one drop of DMF was added, and the
mixture was heated for 1 h under reflux. Excess
thionyl chloride was removed under reduced pressure,
and the dry residue was brought into further trans-
formations without additional purification.
1
740, 730. H NMR spectrum (CF3COOD), δ, ppm:
7.53 d (2H, CH=CH, J = 16 Hz), 7.89–7.97 m (8H),
8.04–8.09 m (10H), 8.65 d (2H, CH=CH, J = 16 Hz).
13C NMR spectrum (CF3CO2D), δC, ppm: 96.78,
105.04, 107.24, 120.51, 120.84, 121.67, 122.35,
123.04, 125.38, 137.87, 141.57, 145.33, 156.43.
Found, %: C 81.71; H 4.64; N 6.17. C30H20N2O2. Cal-
culated, %: C 81.80; H 4.58; N 6.36.
1,3,4-Oxadiazole derivatives XXII–XXIV (gen-
eral procedure). A solution of 2.65 mmol of dichloride
XIX–XXI in 20 ml of anhydrous THF was added
under continuous stirring to a solution of 5.5 mmol of
p-octyloxybenzohydrazide and 20 mmol of triethyl-
amine in 30 ml of anhydrous THF, and the mixture was
stirred for 24 h at room temperature. The precipitate
was filtered off, washed with ethanol and acetone, and
dried. The product was mixed with 30 ml of phos-
phoryl chloride, and the mixture was heated for 48 h
under reflux (TLC). The mixture was cooled and
poured under vigorous stirring into 200 ml of a mix-
ture of crushed ice with water, and the precipitate was
filtered off, washed with water, dried, and recrystal-
lized from DMSO.
4,4′-Bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]-2-
fluorobiphenyl (XVII) was synthesized in a similar
way from 1.13 g (5 mmol) of dialdehyde XIV and
1.4 g (10 mmol) of 2-methyl-1,3-benzoxazole. Yield
1.8 g (78%), mp 298–299°C (from DMSO). IR spec-
trum, ν, cm–1: 3060, 1640, 1600, 1570, 1530, 1450,
1430, 1400, 1350, 1290, 1240, 1180, 1160, 1010, 970,
1
930, 860, 840, 810, 740. H NMR spectrum
(CF3CO2D), δ, ppm: 7.17 d (2H, CH=CH, J = 16 Hz),
7.18 d (2H, CH=CH, J = 16 Hz), 7.42 d (1H, 3-H, J =
11 Hz), 7.49–7.64 m (10H, Harom), 7.67–7.71 m (4H,
H
arom), 8.21 d (2H, CH=CH, J = 16 Hz), 8.27 d (2H,
CH=CH, J = 16 Hz). Found, %: C 78.82; H 4.06;
F 4.25; N 6.01. C30H19FN2O2. Calculated, %: C 78.59;
H 4.18; F 4.14; N 6.11.
4,4′-Bis[5-(4-octyloxyphenyl)-1,3,4-oxadiazol-2-
yl]biphenyl (XXII). Yield 83%, mp 256°C. IR spec-
trum, ν, cm–1: 3070, 2930, 2860, 1620, 1590, 1550,
1500, 1490, 1470, 1420, 1410, 1310, 1260, 1180,
1100, 1070, 1050, 1030, 1010, 970, 840, 830, 740,
4,4′-Bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]-2,2′-
difluorobiphenyl (XVIII). A mixture of 0.15 g
(0.6 mmol) of compound XV and 0.2 g (1.5 mmol) of
2-methylbenzoxazole in 10 ml of DMSO was added to
a solution of sodium methoxide prepared from 3 ml of
methanol and 50 mg of metallic sodium. The mixture
was stirred for 1 h, and the precipitate was filtered off
and recrystallized from DMSO. Yield 0.23 g (72%),
mp 276°C. IR spectrum, ν, cm–1: 3060, 1630, 1540,
1
730, 700, 650. H NMR spectrum (CDCl3), δ, ppm:
0.9 t (6H, CH3, J = 7 Hz), 1.3–1.38 m (16H, CH2),
1.49 m (4H, CH2), 1.83 m (4H, CH2), 4.05 t (4H,
OCH2, J = 6.5 Hz), 7.04 d (4H, Harom, J = 9 Hz), 7.82 d
(4H, Harom, J = 8 Hz), 8.09 d (4H, Harom, J = 9 Hz),
8.24 d (4H, Harom, J = 8 Hz). 13C NMR spectrum
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008

SYNTHESIS AND PROPERTIES OF LUMINOPHORES
1179
(CDCl3), δC, ppm: 14.12, 22.66, 26.01, 29.14, 29.24,
29.35, 31.81, 68.31, 115.01, 116.07, 123.69, 127.42,
127.72, 128.73, 142.78, 162.06, 163.79, 164.76. Found,
%: C 75.77; H 7.13; N 7.82. C44H50N4O4. Calculated,
%: C 75.62; H 7.21; N 8.02.
This study was performed under financial support
by the Foundation for Basic Research of Belarus
Republic (project no. Kh05-112).
REFERENCES
2-Fluoro-4,4′-bis[5-(4-octyloxyphenyl)-1,3,4-oxa-
diazol-2-yl]biphenyl (XXIII). Yield 82%, mp 246–
247°C. IR spectrum, ν, cm–1: 3060, 2940, 2860, 1610,
1580, 1550, 1490, 1470, 1420, 1400, 1300, 1250,
1180, 1100, 1070, 1050, 1030, 1000, 980, 970, 880,
1. Wincler, B., Meghdadi, F., Tasch, S., Evers, B.,
Schneider, I., Fischer, W., Stelzer, F., and Leising, G.,
Synth. Met., 1999, vol. 102, p. 1083.
2. Hohnholz, D., Schweikart, K.-H., Subramanian, L.A.,
Wedel, A., Wischert, W., and Hanack, M., Synth. Met.,
2000, vol. 110, p. 141.
1
840, 690, 670, 650. H NMR spectrum (CDCl3), δ,
ppm: 0.9 t (6H, CH3, J = 7 Hz), 1.3–1.4 m (16H, CH2),
1.45–1.5 m (4H, CH2), 1.8–1.85 m (4H, CH2), 4.04 t
(4H, OCH2, J = 6.5 Hz), 7.04 d (4H, Harom, J = 8.5 Hz),
7.67 t (1H, 6-H, J = 8.5 Hz), 7.78 d (2H, 2′-H, 6′-H,
J = 7 Hz), 7.94 d.d (1H, 3-H, J1 = 10.5, J2 = 1.5 Hz),
8.03 d.d (1H, 5-H, J1 = 8, J2- = 1.5 Hz), 8.08 d (2H,
3. Ol’khovik, V.K., Matveenko, Yu.V., Kalechits, G.V.,
Pap, A.A., and Zenyuk, A.A., Russ. J. Org. Chem.,
2006, vol. 42, p. 1164.
4. Galinovskii, N.A., Vasilevskii, D.A., and Ol’kho-
vik, V.K., Vestn. Fonda Fund. Issled., 2004, vol. 1, p. 80.
5. Son, S.-H., Yun, Je-J., Oh, G.-Ch., Jung, S.-Y.,
Kim, Y.-K., Kuhta, A.V., Olkhovik, V.K., Sasnouski, G.,
and Han, E.-M., Curr. Appl. Phys., 2005, vol. 5, p. 75.
H
arom, J = 8.5 Hz.), 8.09 d (2H, Harom, J = 8.5 Hz),
8.24 d (2H, 3′-H, 5′-H, J = 8.5 Hz). Found, %:
C 73.64; H 6.94; F 2.59; N 7.71. C44H49FN4O4. Calcu-
lated, %: C 73.72; H 6.89; F 2.65; N 7.82.
6. Suschitzky, R., Adv. Fluorine Chem., 1965, vol. 4, p. 1.
7. Organic Syntheses, Blatt, A.H., Ed., New York: Wiley,
1943, collect. vol. 2, p. 299. Translated under the title
Sintezy organicheskikh preparatov, 1949, vol. 2, p. 534.
2,2′-Difluoro-4,4′-bis[5-(4-octyloxyphenyl)-1,3,4-
oxadiazol-2-yl]biphenyl (XXIV). Yield 33%,
mp 185°C. IR spectrum, ν, cm–1: 3100, 2930, 2860,
1610, 1580, 1550, 1490, 1470, 1420, 1300, 1240,
1170, 1130, 1090, 1070, 1040, 1030, 990, 970, 960,
8. Janietz, S., Anlauf, S., and Wedel, A., Synth. Met., 2001,
vol. 122, p. 11.
9. Kaminorz, Y., Schulz, B., Schrader, S., and Brehmer, L.,
1
860, 830, 730, 710, 640. H NMR spectrum (CDCl3),
Synth. Met., 2001, vol. 122, p. 115.
δ, ppm: 0.91 t (6H, CH3, J = 7 Hz), 1.31–1.40 m (16H,
CH2), 1.47–1.51 m (4H, CH2), 1.81–1.87 m (4H, CH2),
4.06 t (2H, CH2, J = 7 Hz), 7.02–7.05 m (4H, Harom),
7.60–7.65 m (2H, Harom), 7.95–7.97 m (2H, Harom),
8.05 d.d (2H, J1 = 8, J2 = 1.5 Hz), 8.07–8.09 m
(4H, Harom). Found, %: C 72.14; H 6.49; F 5.21;
N 7.68. C44H48F2N4O4. Calculated, %: C 71.91; H 6.58;
F 5.17; N 7.62.
10. Detert, H. and Sugiono, E., Synth. Met., 2001, vol. 122,
p. 19.
11. Krasovitskii, B.M. and Bolotin, B.M., Organicheskie
lyuminofory (Organic Luminophores), Moscow:
Khimiya, 1984, 2nd ed., p. 202.
12. Chaplanova, Zh.D., Mikhailovskii, Yu.K., Agabe-
kov, V.E., Ol’khovik, V.K., Galinovskii, N.A., and Gra-
cheva, E.A., Zh. Prikl. Spektrosk., 2007, vol. 74, p. 298.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 8 2008