(E)-2-(hydroxystyryl)-3-phenylquinazolin-4(3H)-ones: Synthesis, photochemical and luminescent properties

Article abstract of DOI:10.24820/ark.5550190.p010.590

The new (E)-2-(hydroxyarilethenyl)-3-phenylquinazolin-4(3H)-ones with various substituents in phenyl fragment were synthesized. The effect of electron donor and acceptor substituents (±M) in quinazolinones on luminescence intensity and dual emission in 55

Full text of DOI:10.24820/ark.5550190.p010.590

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Arkivoc 2018, part vii, 0-0
(E)-2-(hydroxystyryl)-3-phenylquinazolin-4(3H)-ones: synthesis, photochemical
and luminescent properties
Grigory A. Kim,a Irina G. Ovchinnikova,a Emiliya V. Nosova,b Gennady L. Rusinov,a,b Valery N. Charushina,b
a I. Postovsky Institute of Organic Synthesis, Ural Division, Russian Academy of Sciences, S. Kovalevskoy Str., 22,
Ekaterinburg, 620041, Russia
b Ural Federal University named after the First President of Russia B.Eltsin, Mira St. 19, Ekaterinburg, 620002,
Russia
E-mail: kim-g@ios.uran.ru
Received 04-05-2018
Accepted 09-23-2018
Published on line 10-14-2018
Abstract
The new (E)-2-(hydroxyarilethenyl)-3-phenylquinazolin-4(3H)-ones with various substituents in phenyl
fragment were synthesized. The effect of electron donor and acceptor substituents (±M) in quinazolinones on
luminescence intensity and dual emission in 550-650-nm wavelength range was shown. The fact of the
reversible photo/thermal E-Z isomerization for several substances was established. The (E)-2-(5-chloro-2-
hydroxystyryl)-3-phenylquinazolin-4(3H)-one had shown the best combination of photochemical (E-Z
isomerization) and photophysical properties. The (E)-2-(2-hydroxy-5-morpholinostyryl)-3-phenylquinazolin-
4(3H)-one had revealed the best ESIPT-luminescence (Φrel = 5.3 %).
Keywords: (E)-2-(Hydroxystyryl)quinazolinones, ESIPT-luminescence, photoacids, reversible photo/thermal
isomerization, photoswitching
DOI: https://doi.org/10.24820/ark.5550190.p010.590
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Introduction
Diarylethenes and its heterocyclic analogues form the basis of modern electroluminescent and photochromic
materials, widely used in nonlinear optics, lasers with tunable frequency, optoelectronic devices for recording
and storage of information, and molecular photoswitches1,2. Unsymmetrical derivatives are of great interest
among hetarylstylbenes3. The presence of acceptor azine (azinone) core in combination with donor (aryl)
fragment in stilbene molecules might considerable influence the photochemical and photophysical properties
of luminophores because of the n,π* state contribution4. However, the amount of publications devoted to the
study of unsymmetrical (het)arylethens is not as numerous as for symmetric ones3. There are several
publications concerning the synthesis of (E)-2-styrilquinozaline-4(3H)-ones and studying of their photophysical
properties3,5-9. It should be noted that compounds of this push-pull type possessing a specific emission ability
and a profound tendency to a photoinduced E-Z-isomerization8,9 are quite promising for the development of
base- and acid-sensitive photochromic materials. Our researches have shown that the incorporation of the
hydroxyl group in the ortho position of the arylethenyl fragment of quinazolinones 3 (Scheme 1)10,11
,
generates photocontrolled processes like ESIPT luminescence12 with a typical broadband spectrum in visible
400-600-nm wavelength range and reversible E-Z isomerization of the vinylene moiety. Appropriate
mechanisms of proton transfer in excited state (ESIPT) to the diazinone fragment and back in the course of
tautomeric transitions in the conjugated chromophore system were proposed. In this communication we wish
to report about influence of donor and acceptor substituents in phenol fragment of (E)-2-
(hydroxyarylethenyl)-3-phenylquinazolin-4(3H)-ones on ESIPT and geometric isomerization of chromophore
system. Such system may be useful for white-light emitting materials.
Results and Discussion
The C=C bond formation techniques in the series of (het)arylstilbenes have often a specific nature, while
condensation of 2-methylazines4 with aromatic aldehydes in the presence of zinc chloride or sodium acetate
does not provide high yields of the target compounds. We have established that using boric acid as the
catalyst in the proposed method (Scheme 1)11,12 afford to synthesize 2-(arylethenyl)-3-phenylquinazolin-4(3H)-
ones with various acceptor and donor functional groups, including hydroxyl ones, with yields from moderate
to excellent. Synthesized substances are the E-isomers. The trans-isomerization of 3a-f is confirmed by the
presence of doublets of vicinal protons of С=С bonds in range of δ 7.79—8.25 and 6.14—6.75 ppm with the
spin-spin coupling constant of ~15.5 Hz in their 1H NMR spectra.
Scheme 1. Synthesis of (E)-2-(hydroxyarylethenyl)-3-phenylquinazolin-4(3H)-ones.
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Photophysical properties of luminophores 3
The photophysical properties of phenols have been studied by UV-Vis in neutral, basic (Me4NOH and t-BuOK)
and acidic (CH3COOH) solutions in DMF. In neutral DMF solutions the compounds 3a-f exhibited similar
spectral characteristics with absorption maxima in the range 340-400 nm. Compared to the 355-nm
absorption maximum of model ortho-hydroxystyryl substituted 3g10, the absorption bands in UV spectra of the
compounds 3a-f demonstrate the following differences. The electron-donor groups (+M) in compounds 3a, 3f
and 3e compounds provide bathochromic shift of this absorption maximum up to 3-10 nm. The presence of
morpholine fragment in quinazolinone 3d structure leads to a splitting of the absorption band with the
emergence of a long-wave shoulder at 365-480 nm. On the contrary, the electron withdrawing nitro group in
3b and OH group in the meta position of 3c provide hypsochromic shift up to ~ 12 nm.
I (a.u.)
A
x0,08
4 (THF)
3a
3b
3c
0,6
120
4 (DMF)
110
5
3d DMF
3d THF
3e
0,5
0,4
0,3
0,2
0,1
0,0
100
90
80
70
60
50
40
30
20
10
0
2
1
3f
6
3
5
4
2
3
1
6
300
400
500
600
700
λ, nm
Figure 1. The electron absorption spectra and fluorescence emission spectra (λex in the table 1) of solutions of
compounds E-3 (2·10–5 mol L–1, in DMF), E-3a (1), E-3b (2), E-3c (3), E-3d (4), E-3e (5), E-3f (6).
Fluorescence spectra of the neutral solutions E-3 demonstrate the following features. The OH group in the
ortho and para positions of the phenolic moiety, which is included in the common conjugation chain, leads to
a significant broadening of the emission band in the 400-700-nm region compared with that for the meta
substituted E-3c (~ 400-530 nm). At the same time, a bathofluoric shift of the emission band maximum from
420 nm to 485 nm is observed upon the transition from the electron withdrawing nitro derivative E-3b to the
E-3a, E-3f and E-3e with electron donor substituents (+M). It was previously shown that E-3g and its alkoxy
derivatives have dual emission in neutral media10,11 associated with proton transfer in molecules in the excited
state (ESIPT). This process is characterized by the emergence in the spectra of long-wavelength emission
bands in the 500 - 700 nm region with large Stokes shift values (≥ 6000 cm-1)12 due to the free phenolate-anion
and quinonoid-anion forms that are present in solutions along with an excited undissociated phenol form. The
quinazolinones E-3a and E-3d in neutral media demonstrate the similar behavior. In the emission spectrum of
E-3a, like of E-3g, an excited undissociated phenol form A (normal Franck-Condon excited state) and
quinonoid-anion form B (C), which are in protolytic equilibrium in photostationary state solutions (PSS), are
characterized by maxima at 445 and 600 nm, respectively (Figure 1, Scheme 2). In irradiated solutions of E-3d
the equilibrium is totally shifted to the free phenolate-anion and quinonoid-anion forms (Figure 1, Scheme 2)
with emission band maximum at 625 nm in DMF or at 583 nm in THF, like for the ortho-hydroxystyryl
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substituted E-3g in Et3N solutions11. Apparently, the formation of quinonoid-anion form G is directly related to
the transfer of the proton to the morpholine nitrogen atom in the excited planar conjugated chromophore E-
3d to form the morpholinium zwitterion D (Scheme 2). These arguments are confirmed by quantum-chemical
calculations according to which the amino group is involved in the electron density of the chromophore
HOMO localized on the phenol fragment (S-Table 3). It is worth noting a certain hypsochromic shift of the
emission maximum by 42 nm in irradiated solutions of E-3d in THF, compared with that in DMF, and an
increase by two orders of emission intensity with quantum yield of 5.3 % (< 0.1% for the other substances).
These differences observed in the spectra can be explained by the predominance of the free phenolate-anion
form G in equilibrium medium (Scheme 2).
Table 1. Photophysical and photochemical characteristics of quinazolinones E-3 in DMF
Compound λex/nm
λfl/nm
Stokes
shift/cm-1
max(abs)a/nm ()
Starting
tE-Zb/s
tZ-Ec/m
Reaction
mixture
E-isomer
E-3a
358
455 600 5955
11267
360 (20380)
359 (17855)
20
40
E-3b
E-3c
E-3d
342
343
338
420
411
5430
4823
348 (21950)
343 (16565)
329 (10295)
400 (6040)
356 (21730)
358 (20345)
358 (20100)
309 (17715)
343 (14720)
−
180
18
−
40
−
−
625 583 9000
(THF)
485
7847
6191
6925
E-3e
E-3f
E-3g
365
356
358
348 (10835)
316 (10760)
358 (9950)
12
16
16
80
30
40
475
455 600 5955
11266
aThe absorption maxima and the corresponding extinction coefficients [14] (L mol–1 cm–1) of 3 (2·10–5 mol L–1).
bDuration of photochemical E-Z isomerization of solutions upon exposure to irradiation.
cDuration of thermal Z-E isomerization of solutions thermostated at 75 °C
The validity of the assignment of 600-nm long-wavelength luminescence to the quinonoid-anion form is
confirmed by the spectral data of titration of E-3 solutions with t-BuOK and Me4NOH bases. Similarly to E-3g11,
significant changes associated with redistribution and appearance of a new absorption band in the 400-500
nm visible wavelength range are observed in spectra of E-3 basic solutions with the exception of E-3c and E-
3d. The luminescence spectra demonstrate high intensity 600-nm emission band. These changes are related to
the tautomeric transformation of conjugated system E-3 into the quinonoid form E-4 (Scheme 2, Table 2, Fig.
2) and the formation of charge transfer complexes. Earlier obtained results of 2D homo- and heteronuclear
NMR experiments in the case with steady-state basic solutions of E-3g had unequivocally confirmed the
formation of the quinonoid form E-4g with the transfer of a negative charge from the phenolate anion to the
1
oxygen atom of the keto-group10 (Scheme 2). Similar changes of proton signal positions occur in H NMR
spectra, e.g. E-3a (Experimental Section, S-Fig. 1). Consequently, a significant luminescence at 600 nm has
been the result of the direct excitation of the quinonoid-anion form E-4 (similarly E-3g10) and exhibited a
normal Stokes’ shift (Δν 1665 – 5327) and high quantum yield (Table 2). The quantum yield of chlorine
substituted E-3a reaches the highest values (23.4%) and its decrease by two orders for E-3b is caused by
luminescence quenching because of nitro group.
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Scheme 2. Photophysical and photochemical processes in (E)-2-(hydroxyarylethenyl)-3-phenylquinazolin-
4(3H)-ones.
I (a.u.)
A
0,8
80
3
2
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0,0
70
60
50
40
30
20
10
0
1
300
400
500
600
700
λ/nm
Figure 2. The electron absorption (1), fluorescence emission (2) and excitation (3) spectra of the quinonoid
form of E-3a (2·10–5 mol L–1) in DMF after the addition of Me4NOH in the molar ratio of 1:20 (excitation and
emission wavelength, λ/nm: 457 and 605, respectively).
Table 2. Selected photophysical characteristics of the quinonoid form E-4 of E-3 (2∙10–5 mol L–1) in basic media
(DMF and Me4NOH or t-BuOK), CE-3:Cbase as 1:20.
Compound (2·10-5 mol L–1) λabs/nm
λex/nm
457
505
276
338
518
580
520
λem/nm
604
555
385
625
567
642
607
Stokes’ shift / cm-1
rel (%)
4a
4b
3c
3d
4e
4f
443
490
337
5327
2390
3699
9000
1856
1665
2757
23,4
0,2
-
0.8
0.3
12,2
12,5
329 (400 shoulder)
513
548
520
4g
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A
E-3d
E-3d + Me4NOH
I (a.u.)
I (a.u.)
A
2
150
0,5
70
60
50
40
30
20
10
E-3c
1
3
2
E-3c + Me4NOH
2
E-3d + CH3COOH
0,3
3
0,4
0,3
0,2
0,1
0,0
E-3c + CH3COOH
3
1
100
50
1
0,2
0,1
2
3
1
0
0,0
0
300
400
500
600
700
300
400
500
600
700
λ/nm
λ/nm
Figure 3. The electron absorption and fluorescence Figure 4. The electron absorption and fluorescence
emission spectra (λex~338 nm) of E-3d (2·10–5 mol L–1) emission spectra (λex~343 nm) of E-3c (2·10–5 mol L–
in DMF (1) and after the addition of Me4NOH in the 1) in DMF (1) and after the addition of Me4NOH in
molar ratio of 1:20 (2) and CH3COOH (0.1 N in DMF) the molar ratio of 1:20 (2) and CH3COOH (0.1 N in
(3).
DMF) (3).
Another confirmation of ESIPT-luminescence of E-3a is its quenching in the process of the
spectrophotometric titration of solutions with acetic acid (0.1 N CH3COOH), accompanied by the
disappearance of the maximum in λmax at 600 nm in their emission spectra (S-Fig. 3). Similar changes were
observed earlier for E-3g and its alkoxy derivatives11. The well known cause of ESIPT-luminescence quenching
in such photoacids as aromatic alcohols is rapid reprotonation of any excited alcoholate ion under acidic
conditions13.
The absence of any changes in absorption and emission band positions in optical spectra of ortho and para
hydroxy derivative E-3b, E-3e and E-3f indicates the presence of the excited undissociated phenol forms
having a normal emission with maximum at 420 – 485 nm in steady-state neutral and acid solutions. At the
same time, their basic solutions demonstrate a tendency to tautomeric transformations under more stringent
conditions.
The positions of the absorption and emission bands in the optical spectra of E-3c and E-3d in steady-state
neutral, basic and acidic solutions remain unchanged as well, but the causes of these observed phenomena
are different. The lack of conjugation between the hydroxy group and the chromophoric system of the
heterocycle E-3c proved to be the main reason for the existence of only excited undissociated phenol form in
irradiated solutions at various acidity and basicity values (Fig. 4). On the contrary, electro-negative amino
group included in the common conjugated system of (E)-2-(hydroxyarylethenyl)-3-phenylquinazolin-4(3H)-
ones E-3d successfully competes for the binding of a proton (cation) with diazinone cycle during the formation
of the zwitterionic, morpholinium cationic (a) and phenolate-anion (b) forms in neutral, acidic and basic media
(Scheme 2, Table 2, Fig. 3). This is obviously the main reason for inhibiting the formation of quinonoid form E-
4d in basic media in the ground state.
Photochemical properties of chromophores 3
The tendency of E-3 ligands to photoinduced E-Z isomerization has been investigated by ultraviolet light
irradiating (365-nm wavelength band, mercury lamp) of their DMF solutions and estimated by absorption and
fluorescence spectroscopy. The E-isomers 3a,b,e,f have been found to demonstrate reverse E-Z-E
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photo/thermal isomerization in a neutral medium, identical to E-3g10,11. The E-Z isomerization process has
been accompanied by a decrease in the intensity of the absorption band to a photostationary state (PSS) with
characteristic isobestic points on the absorption titration curves in their UV-Vis spectra. The formation of the
Z-isomer has been confirmed by the appearance of doublets of the vicinal protons of the C=C bond in the
1
range of δ 5.9-6.6 ppm with a spin-spin interaction constant of 12.5 Hz in H-NMR spectra, for example, of
irradiated solutions of 3a in DMSO-d6 (experimental Section, S-Fig. 4).
According to spectroscopic studies, the nature of the introduced substituents in the para/ortho position to
the OH group of phenols E-3 has a substantial effect on the time required to achieve a PSS. So the electron
donor substituents of E-3a, E-3e and E-3f provide a commensurate with E-3g rate of E-Z isomerization in DMF
about 16 – 20 s (Table 2), whereas the presence of an electron-withdrawing nitro group in E-3b leads to a
significant deceleration of isomerization from 16 to 180 s. The reversible thermal Z-E isomerization has passed
by solution thermostating at 75° C similarly E-3g (S-Fig. 4). In general, the time of the dark Z-E isomerization
(30-40 m) of diazinones 3a,b and 3f comparable to that for previously studied derivative E-3g10,11, while the
reaction time of the para-hydroxy substituted 3e is doubled (Table 1).
The meta position of the OH group in the chromophore E-3c hasn’t practically an effect on the rate of
photoinduced E-Z isomerization but completely inhibits the reversible thermal Z-E isomerization process, i.e.
the photoisomerization reaction in this compound becomes irreversible.
According to the spectral data, the morpholino-substituted E-3d in the irradiated solutions has not
isomerized. Apparently, the action of the amino group associated with the formation of morpholinium
zwitterion D is aimed at stabilization of the trans geometry of excited molecules and, accordingly, a complete
PSS equilibrium shift from the photochemical toward the competitive photophysical processes in
chromophore solutions. Moreover, the competitive proton transfer to the amino group of the phenolic
fragment, rather than the C=O and C=N heterocycle groups10, can also be a determining factor in the slowing
or inhibition of photo/thermal isomerization processes (Table 1). A possible competitive photoinduced
transfer of a proton to nitro group as a result of the electron density shift in the phenolic fragment with the
formation of 4-oxocyclohexa-2,5-dienylideneazinic acid residue is a probable cause of a significant slowdown
in the photoisomerization reaction of E-3b. In favor of the probable proton transfer to the amino or nitro
group of the phenolic fragment, quantum-chemical calculations of HOMO and LUMO of E-3b,d show the
localization of the electron density on the phenolic fragment involving the above substituents (S-Table 3) and
the smallest values of the band gap energy.
The hindered transfer of the proton to the heterocycle due to the large spatial distance between the
hydroxy group and the diazinonic fragment can be an explanation of deceleration in thermal Z-E isomerization
of 3e. The lack of conjugation and the similar remoteness of the OH group is, apparently, the main reason for
the inhibition of thermal isomerization in E-3c molecules.
Conclusions
In summary, the spectroscopic studies of the synthesized E-isomers of 2-(arylethenyl)-3-phenylquinazoline-
4(3H)-ones 3a-f with various acceptor and donor functional groups (+M) into the ortho, para and meta
position of the phenolic fragment allowed to establish the correlation between structural features of
molecules and their photophysical and photochemical properties. It is shown that the ortho and para positions
of the OH group included in the conjugated chromophoric system lead to a significant broadening of the
emission band in the 400-700 nm range. Moreover, the ortho position of the OH group is an important factor
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in the successful operation of the photoswitches 3a and 3f, i.e. reversible photo/thermal E-Z-E isomerization.
In this case, the most optimal conditions for the transfer of a proton to the spatially-close electronegative
diazinone cycle and back in the isomerization process are formed in the conjugate system. The ortho position
of the OH group is also the crucial factor in the photophysical transformations associated with ESIPT-
luminescence. The transfer of a proton from the OH group to a heterocycle in the chloro-substituted E-3a
apparently provides the coherence of the action of photochemical (E-Z isomerization) and photophysical
(ESIPT-luminescence) transformations. On the contrary, the competitive binding of a proton by an
electronegative amino group in morpholino-substituted E-3d results in a shift in the equilibrium toward
photophysical transformations (ESIPT luminescence) and inhibition of photochemical isomerization. As a
whole, the data obtained allow us to consider these compounds as potential components for supramolecular
ionic devices and white light-emitting organic materials17 in the field of molecular ionics.18
Experimental Section
General. IR spectra were registered on IR-Fourier spectrometer PerkinElmer Spectrum One using diffuse
reflectance sampling accessory (DRA). Electron absorption spectra were recorded on a UV-2600 PC double-
beam spectrophotometer (Shimadzu, Japan) in the range of 190–700 nm with the wavelength setting accuracy
of ±0.3 nm using a Shimadzu scan standard program UVProbe. Fluorescent spectra were recorded on a Varian
Cary Eclipse fluorescence spectrophotometer with mutually perpendicular beams, the wavelength setting
accuracy of 0.5 nm. Quartz cuvette SUPRASIL 111-QS 10 (“Hellma”, Germany) were used for recording in the
range 190-800 nm, the bandwidth around the stationary point of excitation and emission was 10 nm. The
excitation point wavelength was set based on the maximum in absorption and emission spectra, the emission
point wavelength, based on the maximum in excitation spectra. In spectra luminescence of solvents was taken
into account. The relative quantum yields of solutions of compounds 3 were measured at 22 ± 1°C by the
method available on www.jyhoriba.co.uk (Jobin Yvon Ltd. 2 Dalston Gardens, Stanmore, Middlesex HA7 1BQ
UK). Samples of comparison were fluorescein (Фabs = 0,851) in 0.1 N aqueous solution of KOH and quinine
1
13
bisulfate (Фabs = 0,54614) in 0.1 N aqueous H2SO4 solution. NMR spectra the H and C were recorded in
DMSO-d6 solution on devices “Bruker DRX-400” (400 and 100 MHz) and “Bruker AVANCE-500” (500 and 126
1
13
MHz) using TMS and DMSO-d6 (δC 39.5 pps) as an internal standard. Full assignment of signals in H and C
1
1
1
NMR spectra performed using two-dimensional experiments H-1H COSY, H-1H NOESY, H-13C HSQC and
HMBC. Melting point was determined on the microheating table “Boetius”. TLC was performed on plates
Silufol UV-254. The spot was shown the light of a low pressure mercury lamps (6 watts) or iodine vapor. The 2-
methyl-3,1-benzoxazin-4-one was prepared by boiling anthranilic acid in freshly distilled acetic anhydride15.
2-Methyl-3-phenylquinazolin-4(3H)-one (1c) The synthesis was carried out by the method described in.10
Analytical characteristics of the compound were consistent with literature data.
Aniline (0.7 g, 7.5 mmol) and P2O5 (1 g) were added to 2-methyl-3,1-benzoxazin-4-one (1.2 g, 7.5 mmol) in
pyridine (15—20 mL). The reaction mixture was heated for 26 h at 90—95 °C. After the reaction reached
completion, the solvent was evaporated; water (50 mL) was added to the residue. The product was filtered off
and purified on a chromatographic column (SiO2), eluent ethyl acetate—hexane, 3:2. The yield was 1.5 g
(89%). Analytical characteristics of this compound agreed with those given in the literature.10
(E)-2-Styrilquinazolin-4(3H)-ones (3). 1.7 mmol of the corresponding aldehyde 2a-f and equimolar amount of
H3BO3 (1.3 mmol) were added to 0.3 g (1.3 mmol) of compound 1 in acetic acid (30 ml). The reaction mixture
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was boiled for 6-8 hours. After completion of the reaction, the solvent was distilled off. The product has been
purified by column chromatography from various impurities and Z-isomer formed in small quantities in the
synthesis process (2-7 %). Chromatographic separation was carried out on a column (SiO2), making eluent with
a mixture of ethyl acetate and hexane, gradient changing the ratio of the concentrations of solvents from 1:4
to 4:1, respectively. Target product was crystallized from EtOH or CH3CN (3a-f).
(E)-2-(5-Chloro-2-hydroxystyryl)-3-phenylquinazolin-4(3H)-one (3a). Pale yellow, yield 330 mg (72%), mp 309
- 311° C (CH3CN); 1H NMR (500 MHz, DMSO-d6) δ/ppm 10.44 (s, 1Н, OH), 8.13 (d.d, J 8.0, 1.3 Hz, 1H, H-5), 7.95
(d, J 15.6 Hz, 1H, Hβ), 7.87 (d.d.d, J 8.1, 7.0, 1.3 Hz, 1H, H-7), 7.77 (d, J 8,0 Hz, 1H, H-8), 7.55 – 7.63 (m, 3H, H-
11, H-13, H-12), 7.53 (d.d.d, J 8.0, 7.0, 1.0 Hz, 1H, H-6), 7.45 (m, 2H, H-10, H-14), 7.19 (d, J 2,5 Hz, 1H, H-20),
13
7.18 (d.d, J 8.5, 2.5 Hz, 1H, H-18), 6.84 (d, J 8.5 Hz, 1H, H-17), 6.63 (d, J 15.6 Hz, 1H, Hα); C NMR (126 MHz,
DMSO-d6) δ/ppm 161.77, 155.94, 152.37, 147.89, 137.59, 135.17, 134.51, 130.54, 130.05 (2), 129.52, 129.41
(2), 128.77, 127.63, 126.92, 126.87, 123.88, 123.25, 122.10, 120.99, 118.21. IR(DRA): 695, 721, 762, 812, 849,
898, 976, 1015, 1113, 1169, 1246, 1282, 1306, 1337, 1352, 1425, 1470, 1492, 1550, 1572, 1633, 1666, 3047,
3310 cm-1; Anal. Calcd for C22H15ClN2O2: C, 70.50; H, 4.03; N, 7.47, Cl, 9.46. Found: C, 70.58; H, 3.84; N, 7.13.
1
(Z)-2-(5-chloro-2-hydroxystyryl)-3-phenylquinazolin-4(3H)-one (Z-3a). H NMR (DMSO-d6) δ/ppm: 10.04 (s,
1Н, OH), 8.15 (d.d, J 8.3, 1.2 Hz, 1H, H-5), 7.81 (d.d.d, J 8.4, 6.9, 1.5 Hz, 1H, H-7), 7.49 – 7.55 (m, 3H, H-11, H-
13, H-12 H-8, H-6), 7.47 (d, J 2,6 Hz, 1H, H-20), 7.40 (m, 2H, H-10, H-14), 7.13 (d.d, J 8.7, 2.6 Hz, 1H, H-18), 6.76
(d, J 8.7 Hz, 1H, H-17), 6.62 (d, J 12.5 Hz, 1H, Hβ) 5.92 (d, J 12.5 Hz, 1H, Hα).
The quinonoid form E-4a (a solution of E-3a in a 20-fold excess of the base (Me4NOH·5H2O)): 1H NMR (DMSO-
d6, 500 MHz) δ/ppm: 8.76 (br.d, J 8.2 Hz, 1H, H-8), 7.92 (br.d.d, , J 7.7, J 1.6 Hz,1 H, H-5), 7.44 (d, J 16.0 Hz, 1H,
Hβ), 7.19 (m, 2 H, H-11, H-13), 7.11 (d.d.d, J = 8.5, 6.8, 1.5 Hz, 1 H, H-7), 6.87 (t.t, J = 7.3, 1.1 Hz, 1 H, H-12),
6.72 — 6.79 (m, 4 H, H-6, H-10, H-14, Hα), 6.65 (d, J = 3.0 Hz, 1 H, H-20,), 6.59 (d.d, J = 8.9, 3.0 Hz, 1 H, H-18),
6.01 (d, J 8.9 Hz, 1H, H-17).
(E)-2-(2-Hydroxy-5-nitrostyryl)-3-phenylquinazolin-4(3H)-one (3b). Yellow, yield 440 mg (92%), mp 351 - 353°
C (DMF); 1H NMR (500 MHz, DMSO-d6) δ/ppm 11.78 (s, 1 Н, OH), 8.12 (d.d, J 8.0, 1.0 Hz, 1H, H-5), 8.10 (d, J 2.8
Hz, 1H, H-20), 8.06 (d.d, J 9.0, 2.8 Hz, 1H, H-18), 8.02 (d, J 15.6 Hz, 1H, Hβ), 7.89 (d.d.d, J 8.1, 7.0, 1.5 Hz, 1H, H-
7), 7.80 (d, J 8.1 Hz, 1H, H-8), 7.59 – 7.65 (m, 3H, H-11, H-12, H-13), 7.54 (d.d.d, J 8.0, 7.0, 1.0 Hz, 1H, H-6), 7.47
13
(m, 2H, H-10, H-14), 6.98 (d, J 9.0 Hz, 1H, H-17), 6.75 (d, J 15.6 Hz, 1H, Hα); C NMR (126 MHz, DMSO-d6)
δ/ppm 162.32, 161.21, 151.55, 147.30, 139.69, 137.04, 134.68, 133.32, 129.57 (2), 129.07, 128.92 (2), 127.19,
126.56, 126.37, 125.99, 125.13, 122.87, 122.19, 120.57, 116.49. IR(DRA): 699, 721, 736, 750, 771, 832, 855,
900, 911, 977, 1015, 1085, 1120, 1170, 1239, 1251, 1288, 1340, 1365, 1439, 1469, 1494, 1518, 1553, 1586,
1637, 1660, 3011, 3082, 3234 cm-1; Anal. Calcd for C22H15N3O4: C, 68.57; H, 3.92; N, 10.90. Found: C, 68.24; H,
3.63; N, 10.81.
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(E)-2-(3-Hydroxystyryl)-3-phenylquinazolin-4(3H)-one (3c). White, yield 240 mg (67%), mp 272 - 274° C
(CH3CN); 1H NMR (500 MHz, DMSO-d6) δ/ppm 9.57 (s, 1 Н, OH), 8,13 (d.d, J 8.0, 1,0 Hz, 1H, H-5), 7.87 (d.d.d, J
8.0, 7.0, 1.5 Hz, 1H, H-7), 7.79 (d, J 15.5 Hz, 1H, Hβ), 7.78 (d, J 7.9 Hz, 1H, H-8), 7.57 – 7.64 (m, 3H, H-11, H-12,
H-13), 7.53 (d.d.d, J 8.0, 7.0, 1.0 Hz, 1H, H-6), 7.47 (m, 2 H, H-10, H-14), 7.15 (t, J 7.8 Hz, 1H, H-19), 6.79 (d, J
7.7 Hz, 1H, H-20), 6.74 (d.d, J 8.0, 1.7 Hz, 1H, H-18), 6.68 (br.s, 1H, H-16), 6.24 (d, J 15.5 Hz, 1H, Hα); 13C NMR
(126 MHz, DMSO-d6) δ/ppm 161.25, 157.66, 151.32, 147.38, 138.96, 137.02, 136.05, 134.74, 130.05, 129.66
(2), 129.20, 128.93 (2), 127.17, 126.56, 126.41, 120.57, 119.67, 118.98, 117.13, 113.11. IR(DRA): 691, 762, 779,
845, 952, 980, 1017, 1121, 1177, 1243, 1281, 1337, 1382, 1431, 1452, 1472, 1547, 1571, 1594, 1651, 3031,
3166 cm-1; Anal. Calcd for C22H16N2O2: C, 77.63; H, 4.74; N, 8.23. Found: C, 77.67; H, 4.60; N, 8.24.
(E)-2-(2-Hydroxy-5-morpholinostyryl)-3-phenylquinazolin-4(3H)-one (3d). White, yield 230 mg (52%), mp 255
- 257° C (CH3CN); 1H NMR (500 MHz, DMSO-d6) δ/ppm 9.59 (s, 1 Н, OH), 8.11 (d.d, J 7.9, 1.2 Hz, 1H, H-5), 7.96
(d, J 15.5 Hz, 1H, Hβ), 7.86 (d.d.d, J 8.1, 7.0, J 1.5 Hz, 1H, H-7), 7.76 (d, J 8.0 Hz, 1H, H-8), 7.55 – 7.63 (m, 3H, H-
11, H-12, H-13), 7.51 (d.d.d, J 7.9, 7.0, J 0.9 Hz, 1H, H-6), 7.44 (m, 2H, H-10, H-14), 6.84 (d.d, J 8.8, 2.8 Hz, 1H,
H-18), 6.73 (d, J 8.8 Hz, 1H, H-17), 6.67 (d, J 2.8 Hz, 1H, H-20), 6.60 (d, J 15.5 Hz, 1H, Hα), 3.69 and 2.87 (both t,
13
J 4.5 Hz, 8H, NC4H8O); C NMR (126 MHz, DMSO-d6) δ/ppm 161.34, 152.36, 150.72, 147.60, 144.18, 137.33,
136.29, 134.68, 129.54 (2), 128.95 (2), 128.88, 127.05, 126.40, 126.20, 121.57, 120.46, 120.44, 119.81, 116.70,
116.31, 66.11 (2), 49.77 (2). IR(DRA): 694, 727, 767, 831, 888, 925, 987, 1016, 1121, 1182, 1219, 1252, 1272,
1302, 1359, 1433, 1474, 1532, 1574, 1625, 1687, 2854, 2956, 3066, 3226 cm-1; Anal. Calcd for C26H23N3O3: C,
73.39; H, 5.45; N, 9.88. Found: C, 72.99; H, 5.48; N, 9.73.
(E)-2-(4-Hydroxy-3-methoxystyryl)-3-phenylquinazolin-4(3H)-one (3e). White, yield 220 mg (56%), mp 281 -
1
283° C (CH3CN); H NMR (500 MHz, DMSO-d6) δ/ppm 9.53 (s, 1Н, OH), 8.12 (d.d, J 8.1, 1.2 Hz, 1H, H-5), 7.86
(d.d.d, J 8.1, 7.0, 1.6 Hz, 1H, H-7), 7.81 (d, J 15.4 Hz, 1H, Hβ), 7.73 (d, J 8.0 Hz, 1H, H-8), 7.58 – 7.63 (m, 3H, H-
11, H-12, H-13), 7.51 (d.d.d, J 8.0, 7.0, 0.8 Hz, 1H, H-6), 7.46 (m, 2H, H-10, H-14), 6.91 (d, J 1.7 Hz, 1H, H-16),
6.79 (d.d, J 8.1, 1.7 Hz, 1H, H-20), 6.74 (d, J 8.1 Hz, 1H, H-19), 6.08 (d, J 15.4 Hz, 1H, Hα), 3.71 (s, 3H, OCH3); 13C
NMR (126 MHz, DMSO-d6) δ/ppm 161.25, 151.84, 151.77, 147.71, 147.55, 139.35, 137.14, 134.65, 129.56 (2),
128.99, 128.92 (2), 126.92, 126.39, 126.37, 126.13, 120.67, 120.36, 116.57, 115.91, 111.88, 55.45. IR(DRA):
689, 759, 772, 807, 835, 908, 975, 1016, 1037, 1119, 1132, 1165, 1213, 1261, 1286, 1340, 1361, 1400, 1469,
1516, 1542, 1598, 1657, 2839, 2956, 3013, 3065, 3319 cm-1; Anal. Calcd for C23H18N2O3: C, 74.58; H, 4.90; N,
7.56. Found: C, 74.49; H, 4.69; N, 7.51.
(E)-2-(3,5-Di-tert-butyl-2-hydroxystyryl)-3-phenylquinazolin-4(3H)-one (3f). White, yield 230 mg (48%), mp
214 - 216° C (CH3CN); 1H NMR (500 MHz, DMSO-d6) δ/ppm 8.90 (s, 1H, OH), 8.25 (d, J 15.4 Hz, 1Hβ), 8.15 (d.d,
J 8.1, 1.1 Hz, 1H-5), 7.88 (d.d.d, J 8.1, 7.0, 1.5 Hz, 1H, H-7), 7.77 (d, J 8.1 Hz, 1H, H-8), 7.58 – 7.65 (m, 3H, H-11,
H-12, H-13), 7.53 (d.d.d, J 8.0, 7.0, 0.9 Hz, 1H, H-6), 7.46 (m, 2H, H-10, H-14), 7.19 (d, J 2.2 Hz, 1H, H-18), 6.79
13
(d, J 2.2 Hz, 1H, H-20), 6.14 (d, J 15.4, Hz, 1H, Hα), 1.34 (s, 9H, 3CH3), 1.12 (s, 9H, 3CH3); C NMR (126 MHz,
DMSO-d6) δ/ppm 161.21, 152.17, 151.76, 147.52, 141.74, 138.89, 137.29, 135.40, 134.74, 129.52 (2), 128.99,
128.88 (2), 127.02, 126.43, 126.28, 125.20, 124.62, 120.48, 119.96, 119.26, 34.72, 33.77, 31.00 (3), 29.66 (3).
IR(DRA): 699, 724, 781, 879, 957, 970, 1018, 1025, 1128, 1175, 1209, 1232, 1280, 1302, 1359, 1431, 1441,
1469, 1490, 1542, 1574, 1624, 1680, 2872, 2962, 2999, 3030, 3062, 3251 cm-1; Anal. Calcd for C30H32N2O2: C,
79.61; H, 7.13; N, 6.19. Found: C, 79.48; H, 7.19; N, 6.27.
Investigation of photophysical and photochemical properties of 3a-f. Solvents were distilled and dried
according to standard procedures. The irradiation was carried out with a 250 W mercury ball gas discharge
lamp DRSh-250 with a concave mirror and a quartz lens for focusing radiation at the cuvette. To irradiate and
obtain absorption and luminescence spectra, Hellma QS-111 quartz cuvettes with a rubbed lid were used, the
optical path length was 1 cm. The cuvettes were placed in the focus of the photoreactor. Air is used for cooling
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cells and reactor. The desired range of light was allocated by means of filters SZS-7 (thermal filter) and UFS-6
(UV filter). The total power of the light flux after the filters was 150 mW, determined using a meter of average
power and energy of laser radiation IMO-2N16. The luminous flux was directed to the meter by means of
quartz optical fibers.
Kinetic studies using absorption spectroscopy
1. The control of photochemical transformations of E-3a-c,e-f (2·10-5 M) in n-butanol, acetonitrile and DMF
and E-3d in THF was carried out by recording the uv spectra of irradiated solutions every 2 seconds (up to
photostationary state (PSS) of solutions).
2. The control of the thermal transformation of the photostationary solutions Z-3 (2·10-5 М) thermostated at
75 °C was carried out by registration of UV spectra every 10 minutes. The choice of temperature is determined
by 10.
3. Spectrophotometric titration of solutions E-3a,b,e,f (2·10-5 М) by strong bases Me4NOH or t-BuOK was
carried out until unchanged state using a series of solutions with a concentration ratio of CE-3: Cbase from 1:1 to
1:25.
Kinetic studies using NMR. The 1 ml of DMSO-d6 solution of 0.06 mmol E-3 was prepared. Monitoring of
photochemical transformations of E-3 was carried out by recording the 1H NMR spectra of irradiated solutions.
Acknowledgements
This work was supported by the Russian Foundation for Basic Research (grant 18-03-00112). Analytical studies
were carried out using equipment of the Center for Joint Use “Spectroscopy and Analysis of Organic
Compounds” at the Postovsky Institute of Organic Synthesis of the Russian Academy of Sciences (Ural Branch).
Supplementary Materials
1H NMR spectra of 3a and 3d, luminescence data of compound 3a, energies and structures of HOMO and
LUMO of 3a-f are given in the Supplementary Material file associated with this article.
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