Synthesis, structure, and luminescent properties of 2-[2-(9-Anthryl)vinyl] quinolines

Article abstract of DOI:10.1134/S1070428012010113

Previously unknown 2-[2-(9-anthryl)vinyl]quinolin-8-ol and 2-[2-(9-anthryl)vinyl]-8-methoxyquinoline were synthesized by condensation of 8-hydroxy(methoxy)-2-methylquinoline with 9-anthraldehyde in acetic anhydride, as well as by the Wittig reaction. The product structure was determined on the basis of their 1H NMR, IR, UV, and mass spectra and quantum-chemical calculations. 2-[2-(9-Anthryl)vinyl]-8-methoxyquinoline showed luminescence with a quantum yield f of 0.25, which was considerably higher than that of its 8-hydroxy analog (f = 0.067). Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070428012010113

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 1, pp. 78–82. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © O.V. Serdyuk, I.V. Evseenko, G.A. Dushenko, Yu.V. Revinskii, I.E. Mikhailov, 2012, published in Zhurnal Organicheskoi Khimii,
2012, Vol. 48, No. 1, pp. 83–87.
Synthesis, Structure, and Luminescent Properties
of 2-[2-(9-Anthryl)vinyl]quinolines
O. V. Serdyuka, I. V. Evseenkoa, G. A. Dushenkob, Yu. V. Revinskiib, and I. E. Mikhailovb
a Southern Federal University, Rostov-on-Don, Russia
b Southern Research Center, Russian Academy of Sciences, pr. Stachki 194/2, Rostov-on-Don, 344090 Russia
e-mail: mikhail@ipoc.rsu.ru
Received April 6, 2011
Abstract—Previously unknown 2-[2-(9-anthryl)vinyl]quinolin-8-ol and 2-[2-(9-anthryl)vinyl]-8-methoxy-
quinoline were synthesized by condensation of 8-hydroxy(methoxy)-2-methylquinoline with 9-anthraldehyde
in acetic anhydride, as well as by the Wittig reaction. The product structure was determined on the basis of their
1H NMR, IR, UV, and mass spectra and quantum-chemical calculations. 2-[2-(9-Anthryl)vinyl]-8-methoxy-
quinoline showed luminescence with a quantum yield φ of 0.25, which was considerably higher than that of its
8-hydroxy analog (φ = 0.067).
DOI: 10.1134/S1070428012010113
8-Hydroxyquinoline and its derivatives attract con-
siderable interest due to their wide application as
chelating ligands for the preparation of various photo-
and electroluminescent metal complexes [1, 2] and
highly effective fluorescent chemosensors for metal
cations [3, 4]; in addition, these compounds exhibit
strong biological activity [5]. In particular, 8-hydroxy-
quinoline aluminum (AlQ3) due to its good conducting
properties and intense yellow–green luminescence in
the solid state is one of the main electroluminescent
materials in organic light-emitting diodes (OLEDs)
[6]. It is known that π–π*-electron transitions in AlQ3
and analogous metal complexes occur in the chelating
8-hydroxyquinoline ligand and that the highest occu-
pied (HOMO) and lowest unoccupied molecular orbit-
als (LUMO) are localized on the phenol and pyridine
fragments, respectively [7]. Electron-donating and
electron-withdrawing substituents in the phenol and
pyridine rings of the ligand strongly affect the energy
gap between the HOMO and LUMO, so that chemical
modification of the ligand may be used for fine tuning
of optical parameters, as well as of electron and hole
transport properties of metal complexes. Furthermore,
introduction of substituents, e.g., styryl groups, into
the hydroxyquinoline ligand system enhances thermal
stability of metal complexes as compared to complexes
with unsubstituted quinolines and improves their solu-
bility in organic solvents [8, 9]. The latter factor is
very important in the manufacture of light-emitting
diodes; it ensures the possibility of using modern high-
performance technologies such as spin-coating and
ink-jet printing for the preparation of thin amorphous
films from such compounds [10].
Taking the above stated into account, we made
an attempt to obtain a new 8-hydroxyquinoline ligand
system containing a 2-(9-anthryl)vinyl substituent in
position 2 of the quinoline ring with a view to syn-
thesize therefrom photo- and electroluminescent metal
complexes for light-emitting diodes.
It is known that 2-methylquinolin-8-ol (Ia) reacts
with 4 equiv of aromatic aldehydes on prolonged heat-
ing in boiling acetic anhydride to give the correspond-
ing 2-styrylquinolin-8-ols [5, 11, 12]. By analogous
reaction with 9-anthraldehyde we synthesized previ-
ously unknown 2-(2-anthrylvinyl)quinolin-8-ol (IIa) in
moderate yield (29%), and the reaction of the same
aldehyde with 8-methoxy-2-methylquinoline (Ib) af-
forded methoxy derivative IIb (Scheme 1, path a). We
also proposed an alternative synthetic route to com-
pound IIa via Wittig reaction (Scheme 1, path b). The
latter path is more advantageous due to higher yield of
the target product (68%), simpler procedures for its
isolation and purification, and the use of an equimolar
amount of the aldehyde component.
The electronic spectra of IIa contained a set of
strong absorption bands at λmax 213–392 (acetonitrile)
78

SYNTHESIS, STRUCTURE, AND LUMINESCENT PROPERTIES OF 2-[2-(9-ANTHRYL)...
79
Scheme 1.
N
AntCHO, Ac2O, 16 h, reflux
OR
a
N
Me
OR
AntCHO, t-BuOK
MeOH, 24 h
Ia, Ib
IIa, IIb
R = H, Ac2O
reflux
b
Br–
NBS, (BzO)2, CCl4, 10 h, reflux
PPh3, 1 h, reflux
PPh3
N
Me
N
CH2Br
N
OAc
OAc
OAc
III
IV
V
R = H (a), Me (b); Ant = 9-anthryl.
phenolic hydroxy group and basicity of the pyridine-
type nitrogen atom in the 8-hydroxyquinoline system
upon excitation [13, 14]. The electronic absorption
spectra of methoxyquinoline IIb were analogous to the
spectra of IIa, and their emission maxima in toluene
were very similar (λfl 493 and 496 nm for IIb and IIa,
respectively). However, the luminescence quantum
yield of compound IIb (φ = 0.25) was considerably
higher than that of IIa (φ = 0.067) since the former
lacks labile proton and ESIPT is impossible.
The electronic and steric structures and relative
stabilities of possible cis and trans isomers and the
corresponding conformers of IIa and IIb) (see table
and figure; Scheme 2) were determined by quantum-
or 333–391 nm (toluene), which were assigned to π–π*
electron transitions in the anthracene and quinoline
fragments and in the entire conjugation system of
molecule IIa. The observed doubling of long-wave
maxima may be related to the presence of two forms
characterized by fairly similar spectral parameters.
Compound IIa in acetonitrile displayed a lumines-
cence emission maximum at λfl 501 nm (φ = 0.005).
The low luminescence quantum yield φ of IIa may be
due to radiationless deactivation of the excited state via
photoinitiated intramolecular proton transfer (ESIPT)
from the phenolic hydroxy group to the nitrogen atom
in the quinoline ring. The ESIPT process is likely to be
favored by considerable increase of the acidity of the
Scheme 2.
OR
OR
N
1
N
3
5
ΔEZPE = 6.8 kcal/mol
4
N
2
R = H
OR
trans-IIa2, trans-IIb2
TS trans-II
trans-IIa1, trans-IIb1
OR
N
N
OR
cis-IIa1, cis-IIb1
cis-IIa2, cis-IIb2
R = H (a), Me (b).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 1 2012

SERDYUK et al.
80
1.431
1.356
N
1.349
O
0.979
1.466
1.348
1.422
1.332
1.419
1.483
1.419
1.339
2.061
0.979
1.475
1.422
O
1.350
2.059
1.324
N
1.430
1.360
1.493
trans-IIa1, c1
TS trans-IIa, c1
1.423
1.423
1.472
0.978
O
2.067
N
1.347
1.331
1.350
1.355
1.467
1.433
trans-IIa2, c1
Calculated [B3LYP/6-31G(d,p)] structures of conformers trans-IIa1 and trans-IIa2 and transition state for their interconversion
TS trans-IIa (bond lengths are given in Å).
chemical calculations in terms of the density functional
theory [B3LYP/6-31G(d,p)]. Structures cis/trans-IIa1/2
and cis/trans-IIb1/2 (two conformers for each cis and
trans isomer) occupy minima on the potential energy
surfaces. The anthracene fragment in all structures is
appreciably turned apart relative to the quinoline ring
plane; for example, the dihedral angle C2C3C4C5 in
trans-IIa2 is equal to –131.7°. Both conformers of the
trans isomer of IIa are more stable than cis isomers
cis-IIa1 and cis-IIa2 by ΔEZPE = 2.4 and 3.7 kcal/mol,
and the trans isomers of IIb (trans-IIb1 and trans-
IIb2) are more stable than cis-IIb1 and cis-IIb2 by
ΔEZPE = 2.5 and 4.9 kcal/mol, respectively. Therefore,
compounds IIa and IIb were found to exist only as
trans isomers (in keeping with the coupling constants
X-ray diffraction data for styrylquinolines [8]). Con-
formers trans-IIa1 and trans-IIb1 are similar to trans-
IIa2 and trans-IIb2 in stability, and the calculated
barrier to rotation about the C1–C2 single bond through
transition state TS trans-II (R = H) is 6.8 kcal/mol
(see figure). The presence of two conformers of the
trans isomers of IIa and IIb is consistent with the
experimental data (doubling of long-wave absorption
maxima in the electronic spectra).
EXPERIMENTAL
The IR spectra were recorded on an FSM-1202
spectrometer from samples dispersed in mineral oil.
The 1H NMR spectra were measured on a Bruker DPX
250 instrument at 250 MHz from solutions in CDCl3
1
for the vinylic protons in the H NMR spectra and
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 1 2012

SYNTHESIS, STRUCTURE, AND LUMINESCENT PROPERTIES OF 2-[2-(9-ANTHRYL)...
81
Total and relative energies of isomers and conformers of the
ground state of compounds IIa and IIb in the gas phase
calculated by the B3LYP/6-31G(d,p) methoda
using tetramethylsilane as internal reference. The mass
spectra (electron impact, 70 eV) were obtained on
a Kratos MS-30 mass spectrometer (ion source tem-
perature 200°C). The electronic absorption spectra
were measured on a Varian Cary 100 Scan spectro-
photometer. The luminescence spectra were recorded
on a Hitachi F-4010 instrument from solutions in
acetonitrile and toluene. Quantum-chemical calcula-
tions (for isolated molecules) in terms of the density
functional theory [15] using B3LYP three-parameter
potential and B3LYP/6-31G(d,p) valence-split basis set
were performed with the aid of Gaussian-03 software
package. All stationary points on potential energy sur-
faces were identified by calculating Hessian matrices.
Compound
no.
ΔEZPE,
kcal/mol
Etot, a.u.
ω1, cm–1
trans-IIa2
trans-IIa1
TS trans-IIab
cis-IIa1
–1092.9248
–1092.9240
–1092.9134
–1092.9201
–1092.9186
–1132.2174
–1132.2155
–1132.2117
–1132.2091
0.0
0.6
6.8
3.0
3.7
0.0
1.1
3.6
4.9
16
14
b–66b–
11
cis-IIa2
10
trans-IIb2
trans-IIb1
cis-IIb1
15
14
8-Methoxy-2-methylquinoline (Ib) [16] and
2-methylquinolin-8-yl acetate (III) [17] were synthe-
sized according to known procedures.
10
cis-IIb2
10
a
2-[2-(9-Anthryl)ethenyl]quinolines IIa and IIb
(general procedure). A mixture of 10 mmol of
2-methylquinoline Ia or Ib and 40 mmol of 9-an-
thraldehyde in 30 ml of acetic anhydride was heated
for 16 h under reflux. The solvent was distilled off
under reduced pressure, the residue was treated with
6 N sulfuric acid, and the mixture was heated for 3 h at
the boiling point. The mixture was then cooled to 0°C
and made weakly alkaline by adding 1 N sodium hy-
droxide. The precipitate was filtered off and recrystal-
lized from benzene–hexane (1:1).
Etot is the total energy, 1 a.u. = 627.5095 kcal/mol; ΔEZPE is the
relative energy with account taken of zero-point harmonic vibra-
tion energy; ω1 is the least harmonic vibration frequency;
E
ZPE(trans-IIa2) = –1092.5763 a.u.; EZPE(trans-IIb2) =
–1131.8411 a.u.
b
Transition state for the transformation trans-IIa2
trans-IIa1;
ω1 is the only imaginary harmonic vibration frequency.
sium tert-butoxide. The mixture was stirred for 12 h at
room temperature, and 50 ml of benzene and 30 ml of
water were added. The solution was treated with 30 ml
of concentrated hydrochloric acid, the red precipitate
was filtered off and dispersed in water, the suspension
was treated with excess triethylamine, and the resulting
yellow suspension was filtered. The product was dried
and recrystallized from benzene–hexane (1:1). Yield
1.37 g (68%).
2-[2-(9-Anthryl)ethenyl]quinolin-8-ol (IIa).
a. Yield 1.01 g (29%), yellow crystals, mp 195–196°C
(from benzene–hexane, 1:1). IR spectrum, ν, cm–1:
3393, 1562, 1511, 1460, 1376, 1331, 1331, 1086, 894.
1H NMR spectrum, δ, ppm: 7.20–7.26 m (3H, CH=,
H
H
arom), 7.33–7.36 m (1H, Harom), 7.41–7.44 m (1H,
arom), 7.47–7.52 m (3H, Harom), 7.76 d (1H, Harom, J =
2-[2-(9-Anthryl)ethenyl]-8-methoxyquinoline
(IIb). Yield 1.10 g (30%), yellow crystals, mp 174–
175°C (from benzene–hexane, 1:1). IR spectrum, ν,
cm–1: 1557, 1502, 1460, 1376, 1326, 1103, 889.
1H NMR spectrum, δ, ppm: 4.09 s (3H, OMe), 7.06–
7.24 m (2H, Harom), 7.34–7.49 m (7H, CH=, Harom),
7.92–8.01 m (3H, Harom), 8.18–8.22 d (1H, Harom, J =
8.6 Hz), 8.38–8.40 m (4H, CH=, Harom). Mass spec-
trum, m/z (Irel, %): 361 (100) [M]+, 342 (22), 202 (77),
180 (78), 173 (42), 165 (55), 164 (75), 159 (51), 158
(91), 150 (36), 143 (25), 129 (26), 116 (19). UV spec-
trum, λmax, nm (logε): in acetonitrile: 214 (4.61), 256
(5.09), 369 (4.13), 389 (4.17); λfl 494 nm (φ = 0.028);
in toluene: 332 (3.81), 372 (3.97), 392 (4.08);
λfl 493 nm (φ = 0.25). Found, %: C 86.42; H 5.33;
N 3.86. C26H19NO. Calculated, %: C 86.40; H 5.30;
N 3.88.
8.5 Hz), 8.01–8.05 m (2H, Harom), 8.20 d (1H, Harom
,
J = 8.5 Hz), 8.37–8.45 m (3H, Harom), 8.57–8.64 d (1H,
CH=, Jtrans = 19.4 Hz). Mass spectrum, m/z (Irel, %):
347 (100) [M]+, 346 (96), 203 (37), 202 (64), 173 (68),
164 (22), 163 (20), 159 (15), 158 (18), 145 (29), 117
(27). UV spectrum, λmax, nm (logε): in acetonitrile:
213 (4.59), 255 (5.00), 370 (3.96), 392 (4.14);
λfl 501 nm (φ = 0.005); in toluene: 333 (3.82), 371
(4.04), 391 (4.11); λfl 496 nm (φ = 0.067). Found, %:
C 86.44; H 4.95; N 4.06. C25H17NO. Calculated, %:
C 86.43; H 4.93; N 4.03.
b. A mixture of 3.14 g (5.8 mmol) of 8-acetoxy-
quinolin-2-yl(triphenyl)phosphonium bromide (V) and
1.19 g (5.8 mmol) of 9-anthraldehyde in 10 ml of
methanol was treated with 1.2 g (12.5 mmol) of potas-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 1 2012

SERDYUK et al.
3. Song, K.Ch., Kim, J.S., Park, S.M., Chung, K.-Ch.,
82
8-Acetoxyquinolin-2-ylmethyl(triphenyl)phos-
Ahn, S., and Chang, S.-K., Org. Lett., 2006, vol. 8,
phonium bromide (V). A mixture of 5.03 g (25 mmol)
of 2-methylquinolin-8-yl acetate (III), 4.45 g (25 mmol)
of N-bromosuccinimide, and 0.03 g of benzoyl per-
oxide in 40 ml of carbon tetrachloride was heated for
10 h under reflux. The mixture was filtered from
succinimide, the filtrate was carefully evaporated,
20 ml of benzene and 6.55 g (25 mmol) of triphenyl-
phosphine were added to the residue, the mixture was
heated for 1 h under reflux, and the precipitate was
filtered off. Yield 7.90 g (58%), light brown crystals,
mp 294–295°C (from acetonitrile). IR spectrum, ν,
cm–1: 1754, 1600, 1463, 1442, 1376, 1205, 1173, 1111,
1074. 1H NMR spectrum, δ, ppm: 1.97 s (3H, MeCO),
5.99–6.09 m (2H, CH2), 7.24–8.08 m (20H, Harom).
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This study was performed under financial support
by the Ministry of Education and Science of the
Russian Federation (Analytical Departmental Special-
Purpose Program “Development of Scientific Potential
at Higher School,” project no. 3.7.11), by the Russian
Foundation for Basic Research (project no. 11-03-
00 145 a), by the Chemistry and Materials Science
Department of the Russian Academy of Sciences
(project “Kinetics, Dynamics, and Mechanisms of
Intramolecular Rearrangements of η1-Cyclopolyene
Compounds”), and by the President of the Russian
Federation (project no. NSh-3233.2010.3). Quantum-
chemical calculations were performed at the Super-
computer Center, Research Institute of Physical
Organic Chemistry, Southern Federal University.
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