Synthesis, structure, and photoluminescence of 5-phenyl-2-pyridyl-5,6- dihydro[1,2,4]triazolo[1,5-c]quinazolines

Article abstract of DOI:10.1007/s11172-012-0014-9

The reactions of salicylaldehyde and benzoic aldehyde with 5-(2-aminophenyl)-3-pyridyl-1?-1,2,4-triazoles were studied. The reaction products are 5-phenyl-2-pyridyl-5,6-dihydro[1,2,4]triazolo[1,5-c]quinazolines. The structures of the synthesized compounds were determined by IR spectroscopy and ¹? and ¹³? NMR spectroscopy. The luminescence properties of solutions and solid samples were studied.

Full text of DOI:10.1007/s11172-012-0014-9

Russian Chemical Bulletin, International Edition, Vol. 61, No. 1, pp. 95—98, January, 2012
95
Synthesis, structure, and photoluminescence
of 5ꢀphenylꢀ2ꢀpyridylꢀ5,6ꢀdihydro[1,2,4]triazolo[1,5ꢀc]quinazolines
A. N. Gusev,a V. F. Shul´gin,a Z. M. Topilova,b and S. B. Meshkovab
aV. I. Vernadsky Tavrida National University,
4 prosp. Vernadskogo, 95007 Simferopol, Ukraine.
Еꢀmail: galex0330@rambler.ru
bA. V. Bogatsky Physicochemical Institute, National Academy of Sciences of Ukraine,
86 Lyustdorfskaya doroga, 65080 Odessa, Ukraine
The reactions of salicylaldehyde and benzoic aldehyde with 5ꢀ(2ꢀaminophenyl)ꢀ3ꢀpyridylꢀ
1Нꢀ1,2,4ꢀtriazoles were studied. The reaction products are 5ꢀphenylꢀ2ꢀpyridylꢀ5,6ꢀdiꢀ
hydro[1,2,4]triazolo[1,5ꢀc]quinazolines. The structures of the synthesized compounds were
determined by IR spectroscopy and 1Н and 13С NMR spectroscopy. The luminescence properꢀ
ties of solutions and solid samples were studied.
Key words: 5ꢀ(2ꢀaminophenyl)ꢀ1Нꢀ1,2,4ꢀtriazoles, 5,6ꢀdihydro[1,2,4]triazolo[1,5ꢀc]ꢀ
quinazolines, luminescence.
The study of the relationship between the specific feaꢀ
tures of the structure of a substance and its spectral propꢀ
erties is an urgent problem of molecular photonics and
physical organic chemistry.1 Correlations structure—propꢀ
erty were revealed for many organic luminophores. Neverꢀ
theless, active studies in this area are being continued at
present, which is due to their wide use in materials sciꢀ
ence, analytical chemistry, and medicinal chemistry.2—4
We have recently5 described the coordination comꢀ
pound of zinc with the condensation product of salicylꢀ
aldehyde and 5ꢀ(2ꢀaminophenyl)ꢀ3ꢀ(pyridinꢀ2ꢀyl)ꢀ1Нꢀ
1,2,4ꢀtriazole, exhibiting intense photoꢀ and electrolumiꢀ
nescence. However, no structural and spectral characterꢀ
istics of the free ligands were studied. In the present work,
we studied the structure and fluorescence properties of
solutions and solid samples of the condensation products
of salicylaldehyde and benzoic aldehyde with 5ꢀ(2ꢀaminoꢀ
4ꢀRꢀphenyl)ꢀ3ꢀpyridylꢀ1Нꢀ1,2,4ꢀtriazoles (1—8).
Results and Discussion
The starting 5ꢀ(2ꢀaminoꢀ4ꢀRꢀphenyl)ꢀ3ꢀpyridylꢀ1Нꢀ
1,2,4ꢀtriazoles were synthesized by the reaction of nitriles
of pyridinecarboxylic acids with hydrazides with the corꢀ
responding 2ꢀaminobenzoic acids.6 The studied comꢀ
pounds were prepared by the reaction of aromatic aldeꢀ
hydes with 5ꢀ(2ꢀaminophenyl)ꢀ3ꢀpyridylꢀ1Нꢀ1,2,4ꢀtriꢀ
azoles in an alcoholic solution (Scheme 1).
It was established that the reaction is general and
affords 5ꢀphenylꢀ2ꢀpyridylꢀ5,6ꢀdihydro[1,2,4]triazoloꢀ
[1,5ꢀc]quinazolines 1—8. It has earlier7,8 been found by
Xꢀray diffraction analysis that in coordination compounds the
condensation product of salicylaldehyde with 5ꢀ(2ꢀaminoꢀ
phenyl)ꢀ3ꢀ(pyridinꢀ2ꢀyl)ꢀ1Нꢀ1,2,4ꢀtriazole can exist in
two isomeric forms: linear azomethine form (А) and cyꢀ
clic dihydrotriazaindolizine form (В).
The data of NMR and IR spectroscopy indicate that in
the free state compounds 1—8 exist in cyclic form В. The
IR spectra of the synthesized substances in the region of
3270—3400 cm–1 exhibit bands attributed to the N—H
group stretching vibrations. The bands are insignificantly
broadened due to hydrogen bond formation. The skeletal
stretching vibrations of the benzene, pyridyl, and triazole
rings are detected at 1512—1602 cm–1. The 1H NMR
spectra of compounds 1—8 are characterized by the signal
of the proton of the С(5)H group at  7.10—7.25. The
Comꢀ Position
R1
R2
Comꢀ Position R1 R2
pound
Py
2
pound
Py
2
2
2
2
1
2
3
4
H
H
H
OH
OH
OH
5
6
7
8
F
OH
3
4
Cl OH
Br OH
2
Me OH
H
H
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 93—96, January, 2012.
1066ꢀ5285/12/6101ꢀ95 © 2012 Springer Science+Business Media, Inc.

96
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 1, January, 2012
Gusev et al.
Scheme 1
i. Ethaneꢀ1,2ꢀdiol.
a maximum at 365 nm. The studied compounds in the
solid state weakly fluoresce in the visible region with emisꢀ
sion maximum at 430—450 nm. The exceptions are comꢀ
pound 3, whose spectrum contains the emission maxiꢀ
mum at 540 nm, and compound 1, which nearly does not
luminesce in the solid state (Table 2). The variation of the
substituents in the aromatic rings of compounds 4—8 reꢀ
sults in an insignificant longꢀwavelength shift of the lumiꢀ
nescence maximum. The maximum bathochromic shift is
observed for the fluorinated derivative (compound 5). The
low luminescence intensity of the solid samples (except
for compound 2) can be due to considerable nonradiative
energy losses because of intermolecular interactions.
Solutions of compounds 1 and 4—8 in DMSO are
characterized by oneꢀband luminescence and Stokes shifts
usual for organic compounds. The luminescence maxiꢀ
mum is poorly sensitive to the nature of the substituent in
aromatic rings (see Table 2).
singlet signal from the hydrogen atom of the azomethine
group at  8.7—9.3 is absent, which is a ponderable arguꢀ
ment for the formation of the cyclic form.9 The 1Н NMR
spectra contain no signal of the hydrogen atom of the
triazole cycle, which usually appears at  13—14, and the
signal of the hydrogen atom of secondary amine is detectꢀ
ed at  6.99—6.78. The cyclic form is also favored by the
13С NMR spectra in which the signals of the С(5)H carꢀ
bon atom are observed at  67, whereas the signals of
the carbon atom of the HC=N group usually appear at
 157—164.10
The luminescence spectra of compound 3 were studied
in solvents of various polarity. It was found that one maxꢀ
The absorption and luminescence spectra of solid samꢀ
ples and solutions of the synthesized compounds were studꢀ
ied at ambient temperature. The maximum light absorpꢀ
tion for compounds 1—3 is detected at 319—354 nm
(Table 1), indicating the possibility of luminescence excitaꢀ
tion by the absorption of the intense mercury line with
Table 2. Parameters of the luminescence spectra of compounds
1—8 (the Ilum values are reduced to the same experimental conꢀ
ditions separately for solid samples and solutions)
Comꢀ
pound
Solid
sample
Solution in DMSO
(С = 1•10–3 mol L–1
)

max/nm
Ilum

max/nm
Ilum
* (%)
Table 1. Parameters of the absorption and excitation specꢀ
tra of compounds 1—3
1
2
3
4
5
6
7
8
440
430
540
440
450
430
430
450
1
110
8
430
420
528
452
453
448
448
430
105
120
100
131
191
115
53
17
36
5
11
15
12
12
21
Comꢀ
pound
Absorption
Excitation
6
17
20
6

max/nm
А

max/nm I/quantum s–1
1
2
3
348
319
354
0.242
0.149
0.348
390
365
406
682568
1560000
67500
20
110
* Luminescence quantum yield.

Synthesis, structure, and photoluminescence
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 1, January, 2012
97
H, 4.28. C20H15N5O. Calculated (%): C, 70.38; H, 4.40.
1Н NMR, : 10.1 (s, 1 Н, ОН); 8.65 (d, 1 Н arom., J = 4.4 Hz);
8.12 (d, 1 Н arom., J = 8.0 Hz); 7.90 (dt, 1 Н arom., J = 7.2 Hz,
J = 0.8 Hz); 7.80 (d, 1 Н arom., J = 7.2 Hz); 7.40 (m, 2 Н arom.);
7.27 (t, 1 Н arom., J = 8.4 Hz); 7.24—7.19 (m, Н arom. +
+ С(5)H); 6.95 (m, 2 Н arom. + 1 H, NH); 6.85 (t, 1 Н arom.,
J = 7.6 Hz); 6.80 (t, 1 Н arom., J = 7.2 Hz). 13С NMR, : 161.6,
155.2, 151.1, 150.0, 149.9, 143.7, 137.5, 132.3, 130.6, 127.7,
126.1, 124.6, 124.4, 122.2, 119.5, 118.3, 116.3, 115.0, 110.0,
67.7. IR, /cm–1: 3270, 1629, 1597, 1523, 1457, 1361, 1292,
1281, 1236, 1159, 742.
4
3
2
1
400
500
600
700
/nm
2ꢀ(2ꢀPyridinꢀ3ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀyl)phenol
(2). M.p. 245 С (EtOH). The yield was 81%. Found (%):
C, 70.29; H, 4.11. C20H15N5O. Calculated (%): C, 70.38;
Fig. 1. Luminescence spectra of solutions of compound 3 in
various solvents: THF (1), MeCN (2), DMF (3), and DMSO (4).
1
H, 4.40. Н NMR, : 10.04 (s, 1 H, ОН); 9.15 (s, 1 Н arom.);
8.61 (d, 1 Н arom., J = 4.8 Hz); 8.30 (dt, 1 Н arom., J = 8.0 Hz,
J = 0.8 Hz); 7.78 (d, 1 Н arom., J = 8.0 Hz); 7.48 (dd, 1 Н arom.,
J = 7.4 Hz, J = 8.2 Hz); 7.37 (s, 1 Н, С(5)H); 7.24 (dt, 1 Н
arom., J = 8.2 Hz, J = 0.8 Hz); 7.18—7.05 (m, 2 Н arom.); 6.88
(t, 2 Н arom., J = 7.6 Hz); 6.82—6.78 (m, 1 Н arom. + NH);
6.71 (t, 1 Н arom., J = 7.6 Hz). 13С NMR, : 159.7, 155.3,
151.7, 150.9, 149.9, 143.7, 138.3, 132.6, 130.7, 127.5,
126.0, 124.4, 123.9, 120.6, 119.5, 118.3, 116.2, 115.1, 109,8,
67.9. IR, /cm–1: 3402, 1624, 1602, 1512, 1458, 1412, 1350,
1248, 750.
2ꢀ(2ꢀPyridinꢀ4ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀyl)phenol (3).
M.p. 251 С (EtOH). The yield was 87%. Found (%): C, 70.03;
H, 4.54. C20H15N5O. Calculated (%): C, 70.38; H, 4.40. 1Н NMR,
: 10.04 (br.s, 1 H, ОН); 8.66 (d, 2 Н arom., J = 5.6 Hz); 7.90
(d, 2 Н arom., J = 6.0 Hz); 7.79 (d, 1 Н arom., J = 6.8 Hz); 7.40
(s, 1 Н arom.); 7.25 (t, 1 Н, J = 7.6 Hz); 7.20—7.16 (m, 1 Н arom.+
+1 H (С(5)H)); 6.95—6.85 (m, 3 Н arom. + NH); 6.73
(t, 1 Н arom., J = 7.2 Hz). 13С NMR, : 159.6, 155.4,
151.3, 150.8, 150.0, 147.5, 143.7, 134.1, 132.5, 130.6,
127.5, 126.2, 124.5, 124.4, 119.7, 118.4, 116.3, 115.0, 109.7,
67.6. IR, /cm–1: 3402, 1624, 1600, 1512, 1458, 1414, 1350,
1248, 750.
imum is observed in the luminescence spectrum in lowꢀ
polarity THF (Fig. 1, curve 1). On going to solvents of
higher polarity (DMSO, DMF, acetonitrile) (Fig. 1,
curves 2—4), two emission maxima appear, which can be
due to the existence of two tautomers in the excited state.
Thus, it was found that 5ꢀphenylꢀ2ꢀpyridylꢀ5,6ꢀdiꢀ
hydro[1,2,4]triazolo[1,5ꢀc]quinazolines represent a new
class of compounds luminescing in the solid state and in
solutions. These compounds can be recommended for use
as complexation substances in luminescence analysis
and as molecular probes and fluorescent labels in biologiꢀ
cal assays.
Experimental
Nitriles of pyridinecarboxylic acids (Merck) were used as the
starting compounds. Hydrazides of 2ꢀaminocarboxylic acids were
synthesized according to earlier described procedures.11 Solvents
were purified by standard procedures.12
IR spectra were recorded in the 4000—400 cm–1 region
on a Nicollet Nexus 470 spectrophotometer (KBr pellets).
1H and 13C NMR spectra were obtained on a Bruker VXRꢀ400
spectrometer (1Н, 400 MHz; 13С, 75 MHz) using DMSOꢀd6
as a solvent and Me4Si as an internal standard. Absorption
spectra were studied on a Lambdaꢀ9 UV/VIS/NIR spectroꢀ
photometer (Perkin—Elmer). The luminescence spectra of
solid samples were detected on an SDLꢀ1 diffraction spectroꢀ
meter (LOMO, Russia) with a FEUꢀ79 photomultiplier tube.
Excitation spectra were recorded on a FluorologꢀFL 3ꢀ22 inꢀ
strument with a xenon lamp (450 W). The standard for meaꢀ
suring quantum yields was quinine sulfate in a 0.1 М solution
of H2SO4.
Synthesis of 5ꢀphenylꢀ2ꢀpyridylꢀ5,6ꢀdihydro[1,2,4]triazoloꢀ
[1,5ꢀc]quinazolines 1—8 (general procedure). 5ꢀ(2ꢀAminoꢀ4ꢀRꢀ
phenyl)ꢀ3ꢀpyridylꢀ1Нꢀ1,2,4ꢀtriazole (4 mmol) was dissolved in
hot ethanol (20 mL), and aldehyde (4.2 mmol) was added. The
reaction mixture was magnetically stirred for 1 h on heating. The
solution was cooled down, and the precipitate that formed was
filtered off, washed with cold ethanol, and dried in vacuo. The
yields of the products were 1.0—1.2 g (75—87% based on the
starting triazole).
2ꢀ(9ꢀMethylꢀ2ꢀpyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀ
yl)phenol (4). M.p. 209 С (EtOH). The yield was 75%.
Found (%): C, 71.09; H, 4.66. C21H17N5O. Calculated (%):
C, 70.98; H, 4.79. 1Н NMR, : 10.03 (s, 1 H, ОН); 8.61 (d, 1 Н
arom., J = 5.2 Hz); 8.08 (d, 1 Н arom., J = 10.8 Hz); 7.90
(dt, 1 Н arom., J = 6.8 Hz, J = 0.8 Hz); 7.64 (s, 1 Н arom.); 7.43
(dt, 1 Н arom., J =5.6 Hz, J = 0.8 Hz); 7.25—7.15 (m, 1 Н arom. +
+ 1 H, С(5)H); 7.12—6.95 (m, 1 Н arom. + NH); 6.91—6.81
(m, 3 Н arom.); 6.73 (t, 1 Н arom., J = 7.6 Hz); 2.27 (s, 3 Н,
СН3). IR, /cm–1: 3386, 1630, 1600, 1516, 1504. 1418, 1350,
1290, 1248, 750.
2ꢀ(9ꢀFluoroꢀ2ꢀpyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀ
yl)phenol (5). M.p. 241 С (EtOH). The yield was 80%.
Found (%): C, 67.02; H, 3.79. C20H14FN5O. Calculated (%): C,
66.85; H, 3.90. 1Н NMR, : 10.05 (br.s, 1 H, ОН); 8.61
(d, 1 Н arom., J = 4.0 Hz); 8.07 (d, 1 Н arom., J = 7.2 Hz); 7.89
(dt, 1 Н arom., J = 7.2 Hz, J = 1.6 Hz); 7.54 (dd, 1 Н arom.,
J = 8.4 Hz, J = 2.8 Hz); 7.42 (m, 1 Н arom.); 7.34 (s, 1 Н arom.);
7.20—7.05 (m, 2 Н arom. + 1 H, С(5)H); 6.95—6.82
(m, 2 Н arom. + NH); 6.75 (t, 1 Н arom., J = 7.6 Hz). IR,
/cm–1: 3280, 1638, 1600, 1522, 1456, 1422, 1356, 1284,
1196, 746.
2ꢀ(2ꢀPyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀyl)phenol (1).
M.p. 237 С (EtOH). The yield was 85%. Found (%): C, 70.22;
2ꢀ(9ꢀChloroꢀ2ꢀpyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀ
yl)phenol (6). M.p. 235 С (EtOH). The yield was 84%.

98
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 1, January, 2012
Gusev et al.
Found (%): C, 63.72; H, 3.68. C20H14ClN5O. Calculated (%):
C, 63.91; H, 3.73. 1Н NMR, : 10.02 (br.s, 1 H, ОН); 8.60
(d, 1 Н arom., J = 6.0 Hz); 8.08 (d, 1 Н arom., J = 8.0 Hz); 7.89
(dt, 1 Н arom., J = 7.6 Hz, J = 1.2 Hz); 7.72 (d, 1 Н arom.,
J =2.4 Hz); 7.59 (s, 1 Н arom.); 7.42 (m, 1 Н arom.); 7.28
(m, 1 Н arom.); 7.25—7.15 (m, 1 Н arom. + 1 H, С(5)H); 6.96
(d, 1 H, NH, J = 7.2 Hz); 6.87 (d, 2 Н arom., J = 7.6 Hz); 6.75
(t, 1 Н arom., J = 7.2 Hz). IR, /cm–1: 3266, 1626, 1600, 1522,
1458, 1354, 1282, 1152, 752.
2ꢀ(9ꢀBromoꢀ2ꢀpyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,5ꢀc]quinazolinꢀ5ꢀ
yl)phenol (7). M.p. 237 С (EtOH). The yield was 87%.
Found (%): C, 57.25; H, 3.24. C20H14BrN5O. Calculated (%):
C, 57.14; H, 3.33. 1Н NMR, : 10.05 (br.s, 1 H, ОН); 8.60
(d, 1 Н arom., J = 4.4 Hz); 8.07 (d, 1 Н arom., J = 7.6 Hz);
7.90—7.82 (m, 2 Н arom.); 7.61 (s, 1 Н arom.); 7.40—7.30
(m, 2 Н arom.); 7.20—7.10 (m, 1 Н arom. + 1 H, С(5)H); 6.97
(d, 1 H, NH, J = 7.6 Hz); 6.87 (d, 1 Н arom., J = 8.4 Hz); 6.82
(d, 1 Н arom., J = 8.0 Hz); 6.75 (t, 1 Н arom., J = 7.2 Hz). IR,
/cm–1: 3268, 1626, 1600, 1520, 1458, 1354, 1284, 1234,
1152, 752.
References
1. B. M. Krasovitskii, B. M. Bolotin, Organicheskie lyuminofory
[Organic Luminophores], Khimiya, Leningrad 1984, 336 pp.
(in Russian).
2. T. H. Kim, M. S. Choi, B. H. Sohn, S. Y. Park, W. S. Lyoo,
T. S. Lee, Chem. Commun., 2008, 2364.
3. J. S. Brooks, Chem. Soc. Rev., 2010, 39, 2667.
4. L. Ding, Y. Fang, Chem. Soc. Rev., 2010, 39, 4258.
5. N. S. Eremina, K. M. Degtyarenko, R. M. Gadirov, T. N.
Kopylova, G. V. Maier, L. G. Samsonova, V. F. Shul´gin,
A. N. Gusev, S. B. Meshkova, Izv. Vuzov. Fizika [Higher
School Bulletin. Physics], 2010, 53, No. 5, 91 (in Russian).
6. W. R. Browne, D. Hesek, J. F. Gallagher, C. M. O´Connor,
J. S. Killeen, F. Aoki, H. Ishida, Y. Inoue, C. Villani, J. G.
Vos, Dalton Trans., 2003, 12, 2597.
7. A. N. Gusev, V. F. Shul´gin, S. B. Meshkova, Z. M. Topiꢀ
lova, M. A. Kiskin, G. G. Aleksandrov, I. L. Eremenko,
Zh. Neorg. Khim., 2011, 56, 35 [Russ. J. Inorg. Chem.
(Engl. Transl.), 2011, 56, No. 1].
5ꢀPhenylꢀ2ꢀpyridinꢀ2ꢀylꢀ5,6ꢀdihydro[1,2,4]triazolo[1,5ꢀc]ꢀ
quinazoline (8). M.p. 216 С (EtOH). The yield was 76%.
Found (%): C, 73.67; H, 4.65. C20H15N5. Calculated (%):
C, 73.85; H, 4.62. 1Н NMR, : 8.62 (d, 1 Н arom., J =4.4 Hz);
8.07 (d, 1 Н arom., J = 8.0 Hz); 7.89 (dt, 1 Н arom., J = 7.6 Hz,
J = 1.6 Hz); 7.79 (d, 1 Н arom., J = 7.6 Hz); 7.69 (s, 1 Н arom.);
7.44—7.36 (m, 5 Н arom. + 1 H, С(5)H); 7.29 (dt, 1 Н arom.,
J = 8.4 Hz, J = 1.6 Hz); 6.99 (d, 1 H, NH, J = 1.2 Hz); 6.92
(d, 1 Н arom., J = 8.0 Hz); 6.86 (t, 1 Н arom., J = 7.6 Hz).
13С NMR, : 160.9, 154.7, 150.2, 150.0, 149.2, 142.9, 138.3,
132.3, 130.8, 126.2, 126.1, 124.4, 124.4, 122.2, 119.3, 118.5,
116.3, 114.9, 109.9, 67.6. IR, /cm–1: 3296, 1624, 1590, 1528,
1480, 1412, 1356, 1152, 740.
8. A. N. Gusev, V. F. Shul´gin, M. A. Kiskin, I. L. Eremenko,
Koord. Khim., 2011, 37, 119 [Russ. Coord. Chem.
(Engl. Transl.), 2011, 37, No. 1].
9. M. Tanaka, T. Kobayashi, Synthesis, 1985, 967.
10. G. A. Olah, D. J. Donavan, J. Org. Chem., 1978, 43, 860.
11. R. W. Leiby, J. Hetercycl. Chem., 1984, 21, 1825.
12. A. J. Gordon, R. A. Ford, The Chemist´s Companion. A Handꢀ
book of Practical Data, Techniques, and References, Wileyꢀ
Interscience Publication, John Wiley and Sons, New York—Lonꢀ
don—Sydney—Toronto, 1972.
Received February 21, 2011;
in revised form August 10, 2011