Spectral properties and photochemical activity of chalcone derivatives

Article abstract of DOI:10.1023/A:1013237415295

A relationship is found between spectral-luminescent and photochemical properties for mono-and disubstituted chalcone derivatives R¹CO-CH=CHR² [R¹, R² = Ph, 4-FC₆H₄, 4-BrC₆H₄, 2-furyl, 2-thienyl, 4-(PhCONH)C₆H₄, 4-NH²C₆H₄, 4-Me₂NC₆H₄].

Full text of DOI:10.1023/A:1013237415295

Russian Journal of General Chemistry, Vol. 71, No. 8, 2001, pp. 1272 1281. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 8, 2001,
pp. 1345 1355.
Original Russian Text Copyright
2001 by Rtishchev, Nosova, Solovskaya, Luk’yashina, Galaktionova, Kudryavtsev.
Spectral Properties and Photochemical Activity
of Chalcone Derivatives
N. I. Rtishchev, G. I. Nosova, N. A. Solovskaya,
V. A. Luk’yashina, E. F. Galaktionova, and V. V. Kudryavtsev
Institute of High-Molecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
St. Petersburg State Institute of Technology, St. Petersburg, Russia
Received May 17, 2000
Abstract A relationship is found between spectral luminescent and photochemical properties for mono-
and disubstituted chalcone derivatives R1CO CH=CHR2 [R1, R2 = Ph, 4-FC6H4, 4-BrC6H4, 2-furyl, 2-thienyl,
4-(PhCONH)C6H4, 4-NH2C6H4, 4-Me2NC6H4].
Earlier we showed [1] that the spectral luminescent
and photochemical properties of chalcone derivatives
are much dependent on the nuture of substituents in
the styryl moiety. On the other hand, we found that
the benzamide and nitro groups in the ketone moiety
exhibit inhibiting effect, and this finding is consistent
with data of Tsukerman et al. [2, 3] who reported that
the CO group in , -unsaturated ketones does not
completely destroy conjugation.
R1CO CH=CHR2
I XXIII
I, R1 = R2 = Ph; II, R1 = 4-BrC6H4, R2 = Ph; III, R1 =
2-furyl, R2 = Ph; IV, R1 = 2-thienyl, R2 = Ph; V, R1 =
4-(PhCONH)C6H4, R2 = Ph; VI, R1 = 4-NH2C6H4, R2 =
Ph; VII, R1 = Ph, R2 = 4-BrC6H4; VIII, R1 = Ph, R2 =
2-furyl; IX, R1 = Ph, R2 = 2-thienyl; X, R1 = Ph, R2 =
4-(PhCONH)C6H4; XI, R1 = Ph, R2 = 4-NH2C6H4; XII,
R1 = 4-BrC6H4, R2 = 4-(PhCONH)C6H4; XIII, R1
=
2-furyl, R2 = 4-(PhCONH)C6H4; XIV, R1 = 2-thienyl, R2 =
4-(PhCONH)C6H4; XV, R1 = 4-FC6H4, R2 = 4-NH2C6H4;
In this connection we considered it worthwhile to
compare the optical properties and the photochemical
activity of a series of monosubstituted chalcones with
similar substituents either in the ketone or in the
stylbene moiety, and also to examine the behavior of
disubstituted analogs, including corresponding struc-
tural isomers. The choice of substituents was deter-
mined not only by their donor acceptor ability, but
also by their feasibility, like, for example, with amide
chalcone derivatives, for functionalization, which
would aid in introducing chalcone chains into poly-
mers. Practically, such investigations allow modeling
properties of new chalcone polymers. It should be
noted that no data on the effect of the structure of the
ketone moiety on the luminescence of chalcone deriv-
atives are still available, except for some information
for disubstituted chalcones derived from dimethyl-
aniline (295 K) [3, 4], whereas investigations on the
effect of the same factor on trans cis isomerization
have been restricted to heterocyclic analogs [5].
XVI, R1 = 4-BrC6H4, R2 = 4-NH2C6H4; XVII, R1
=
2-furyl, R2 = 4-NH2C6H4; XVIII, R1 = 2-thienyl, R2 =
4-NH2C6H4; XIX, R1 = 2-thienyl, R2 = 4-Me2NC6H4; XX,
R1 = 4-(PhCONH)C6H4, R2 = 4-BrC6H4; XXI, R1 = 4-
(MeCONH)C6H4, R2 = 2-furyl; XXII, R1 = 4-(MeCONH)
C6H4, R2 = 2-thienyl; XXIII, R1 = 4-NH2C6H4, R2
=
4-BrC6H4.
The experimental results are given in Tables 1 and
2. As solvent at 295 K we most frequently used N,N-
dimethylacetamide. With amides and amines, measu-
rements in ethanol and heptane toluene were also
performed.
In terms of structure, the compounds can be
divided into 3 groups: 3-(aryl, heteryl)-1-phenyl-1-
propen-3-one derivatives (II VI) (1st group), 1-(aryl,
heteryl)-3-phenyl-1-propen-3-one derivatives (VII
XI) (2nd group), and disubstituted chalcone deriva-
tives XII XXIII (3rd group).
The objects for study were compounds I XXIII,
both previously unknown and earlier studied, such as
heterocyclic chalcone analogs, for which we obtained
new information.
Monosubstituted chalcones I XI. In the series
R1, R2 = 4-bromophenyl 2-furyl 2-thienyl N-benzo-
yl 4-aminophenyl 4-aminophenyl the frequency shift
*
(
) of the long-wave , -absorption band with
1070-3632/01/7108-1272$25.00 2001 MAIK Nauka/Interperiodica

SPECTRAL PROPERTIES AND PHOTOCHEMICAL ACTIVITY
1273
Table 1. Spectral-luminescent properties and photochemical activity of chalcone derivatives in N,N-dimethylacetamide at
295 K (in air)a
Absorption
Fluorescence
Photolysis
Comp.
no.
(H1/2)
102
F 102
a
a
f
Ss
f
ex
I
II
III
IV
V
312
316
321
323
330
334
318
365
364
321
316
342
345
353
349
338
406
403
32.1
31.6
31.2
31.0
30.3
29.9
31.4
27.4
27.6
31.1
31.6
29.2
29.0
28.3
28.7
29.6
24.6
24.8
2.68
2.99
2.90
3.06
3.95
3.31
2.77
2.43
2.41
2.44
3.09
2.74
2.19
3.62
3.53
1.92
2.83
2.85
2.48
313
313
313
313
334
334
313
366
366
334
313
366
366
366
366
334
406
406
366
29
22
18
23
14
15
16
2.3
0.9
16
23
3.0
3.2
21
Vb
Vc
VI
VIb
VIc
VII
VIII
IX
X
17.2 17.8
17.2 17.8
26.3 25.6
7.6
7.6
8.4
10.0
10.0
5.0 <10
0.05
0.06
3
18.9 19.6
8.6
4.2
10.0
0.11
21.7, 19.2
20.6
6.3
8.1
0.18
0.36
Xb
Xc
XI
XIb
XIc
22
19
6.8
1.5
8.3
19.3
18.7
2.9
3.0
4.6
5.3
6.2
5.4
17
1.1
0.01
339 sh, 355, 29.5 sh, 28.1,
23.7 sh, 22.7,
21.5 sh
21.7, 19.2
21.7, 19.2
21.7, 19.2
19.1
370 sh
359
358
360
410
416
412
415
424
334
348
351
370
27.0 sh
27.9
27.9
27.8
24.4
24.0
24.3
24.1
23.6
29.9
28.7
28.5
27.0
XII
2.89
2.83
3.95
3.15
3.04
3.10
3.34
3.50
3.85
3.10
3.44
2.29
6.2
6.2
6.1
5.3
5.5
4.9
5.4
5.6
0.10
0.11
0.13
366
366
366
406
406
406
406
406
313
366
366
366
21
11
13
XIII
XIV
XV
XVI
XVII
XVIII
XIX
XX
2.9
3.0
2.9
3.1
3.1
16
6.8
18.5
19.4
18.7
18.0
23
20
29
58
1.1
4.9
2.1
0.1
15
XXI
XXII
XXIII
1.7
2.5
2.0
17.9
7.2
9.1
0.10
a
3
1
4
1
1
(
,
) Long-wave absorption maximum, nm, 10 , cm
,
10 , l mol cm ; ( ,
(H 1/2),
Ss) maximum, fluore-
a
a
f
3
1
scence band half-width, and Stokes’ shift, 10 , cm ; ( ) fluorescence quantum yield; (F) photoreaction quantum
f
b
c
yield at
, nm. In 95% ethanol. In heptane toluene, 10:1. The data for compounds V and X are taken from [1] and
ex
for compounds X and XI in 95% ethanol, from [6].
*
respect to chalcone (I) is 500 900 1100 1800 5300
and 500 2900 3100 4100 7500 cm for the 1st and
2nd groups, repectively. The largest shifts are charac-
teristic of substituents stongly involved in charge
bathochromically shifted , band of 1,3-diphenyl-1-
1
propen-3-one (I). Substitution in the ketone moiety of
chalcone (compounds II VI) results in that the
transition is mostly contributed by the charge transfer
*
transfer, which is consistent with theoretical and ex- from the 3-aryl or 3-hetaryl substituent on the pro-
*
perimental data for chalcone and its derivatives [7 9].
penone moiety, i.e. it is a superposition of the ,
*
As follows from the published data, the first
,
band of chalcone and a bathochromically shifted band
of the corresponding acetophenone (compounds II, V,
and VI) or acetylheteryl derivatives (compounds III
and IV). This explains the slightly stronger absorption
band of compounds VII XI (2nd group) is formed
mostly by the charge transfer from the 1-aryl or 1-
heteryl substituent on the propenone moiety and is a
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

1274
RTISHCHEV et al.
Table 2. Luminescent parameters at 77 K in 95% etanola
Comp.
no.
/
ES
ET
EST
f
ph
ph
f
ph
II
III
IV
V
18.3, 16.7, 15.2
>102
>102
>102
>102
1.1
>10
1.0
0.005
0.010
0.008
0.012
0.013
0.007
0.010
18.3
18.2
18.3
18.4
18.5
17.8
16.5
16.4
17.6
15.9
17.6
17.7
17.7
(15.9)
(15.1)
(15.9)
(15.4)
(14.8)
18.0
16.5
16.6
18.4
18.2 sh, 17.9, 16.9, 15.4
18.3 sh, 18.0, 16.9, 15.4
18.4, 17.8 sh, 16.9, 15.3
18.5, 18.0 sh, 17.0, 15.4
17.8, 16.2, 14.6
16,5, 14.9
16.4, 14.8
17.6, 16.1, 14.5
(24.8)
22.9b
(6.2)
4.4
VI
20.1, 19.3 sh
VII
VIII
IX
X
XI
XII
XIII
XIV
XV
XVI
23.7, 22.6, 21.1 sh
23.4, 22.4, 21.1 sh
23.5, 22.1, 21.0 sh
23.7
23.4
23.5
21.7
23.2
23.5
23.5
21.7
20.9b
21.7b
21.2b
20.6b
24.4
24.3
24.0
22.4b
7.2
7.0
5.9
5.8
5.6
0.6
0.1
0.1
0.2
0.1
0.016
0.029
21.7 sh, 20.6, 19.5 sh 15.9 sh, 14.3
23.2 sh, 21.9, 20.8 sh 17.6, 16.0, 14.5
23.5 sh, 22.7, 21.5 sh 17.7, 16.1, 14.6
23.5 sh, 22.5, 21.2 sh 17.7, 16.1, 14.6
0.013
0.010
5.8
5.8
0.2
v
21.7 sh, 20.6, 19.5 sh
19.8, 19.2 sh
<0.1
<0.1
<0.1
<0.1
<0.1
20
(5.8)
(5.8)
(5.8)
(5.8)
(5.8)
5.6
7.8
7.4
4.0
c
c
XVII 19.8, 18.9 sh
XVIII 20.1, 19.4 sh
XIX
XX
c
v
19.4, 18.7 sh
24.4, 23.1, 21.9 sh
24.3, 22.9, 21.7 sh
18.0, 16.5, 14.9
16.5, 15.7 sh, 14.9
16.6, 15.0
0.007
0.006
0.007
XXI
1.5
0.8
XXII 24.0, 22.7, 21.5 sh
XXIII 20.2
18.4 sh, 18.0, 16.8, 15.3
a
3
1
(
,
) Fluorescence and phosphorescence absorption maxima, 10 , cm ; (
/ ) phosphorescence-to-fluorescence quantum
ph f
f
ph
yield ratio; ( ) phosphorescence lifetime, s; (E , E , and
E ) energies of the S and T states, and singlet triplet splitting,
ph
S
T
ST 1 1
3
1
b
c
10 , cm ; values in parentheses are proposed values. Determined by the blue boundary of the fluorescence band. Unresolved
3
1
band at (18.0 12.5) 10 cm
.
*
of 1st group derivatives compared with 2nd group de-
first
,
band of 4-aminoacetophenone which is a
rivatives (cf. IV, IX and V, X). The local absorption
model for compound VI is a charge-transfer band. The
of benzalacetone shows up in solutions of amine VI in
parameters of this band in heptane (283 nm,
*
1
1
polar solvents as the second
,
band (
35300 cm , 1.7 104 l mol 1 cm ) and ethanol
a
1
1
1
32700 cm ) (Fig. 1a, spectra 2 and 3). Compound
VI is the only 1st group derivative to fluoresce at
room temperature, while with an extremely low
(318 nm, 31400 cm , 2.2 104 l mol 1 cm ) suggest
that the cross conjugation of the C6H5CH=CHCO and
4-NH2C6H4CO fragments in aminochalcone VI red
5
3
*
1
quantum yield (10
10 ) (Table 1; Fig. 1a, spectra
shifts the lowest
band by 4000 cm , but the
4 6). Noteworthy is a broad structureless fluorescence
intensity of this band is preserved. The same changes
are characteristic of the emission band. The emission
band of 4-aminoacetophenone in ethanol is a fairly
1
band with a large Stokes’ shift
(up to 104 cm
Ss
in polar solvents). The parameters of this band and
the intensity of fluorescence do not change in going
1
1
narrow band at 31200 23800 cm
(
27000 cm ),
f
1
which corresponds to a
value of 4.5 103 cm .
from N,N-dimethylacetamide to ethanol. The energies
Ss
*
1
of
transitions in solutions, obtained from
The 0 0-transition energy in alcohol is 28000 cm ,
i.e. it is higher than that of 3-(4-aminophenyl)-1-
phenyl-1-propen-3-one (VI) by 4600 cm , in agree-
1
Fig. 1a, are 29000 (heptane) and 23400 cm
1
(N,N-dimethylacetamide, ethanol). Taking account of
*
the ES value for the n level, (24 1) 103 cm 1 [10],
ment of the value of the spectral shift (vide supra).
we can conclude that in the first case emission
involves the S2( *) level, and in the second, as a
The 2nd group contains three fluorescing com-
pounds. Replacement of the phenyl group by 2-furyl
(compound VIII) gives rise to a weak fluorescence
similar in parameters and nature to the fluorescence
*
result of inversion, the S1( , ) level. In both
cases, apparently, a strong vibronic interaction with
*
the S(n ) state takes place. It is known [11] that the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

SPECTRAL PROPERTIES AND PHOTOCHEMICAL ACTIVITY
1275
of amine VI, but the corresponding band is shifted
bathoflorically to the band of the latter by 2000 cm .
1
, nm
400
Benzamide X exhibits fluorescence; it is 2 3 times
stronger compared with heterocyclic chalcone deri-
300
500 600 700
(a)
D
0.8
I, rel. units
2,3
vative VIII but still remains extremely weak (
80
f
3
5,6
10 ). The fluorescence band half-width (N 1/2) in
1
ethanol, while having a large Stokes’ shift, is half that
of compound VIII. In N,N-dimethylacetamide a two-
band fluorescence is observed, resulting, according to
speculations in [1], from torsion of the phenyl groups
about the amide C(O)NH bond in the excited state.
The strongest fluorescing 2nd group compound is
amine XI (Table 1; Fig. 1b, spectra 4 6). Earlier we
studied the luminescence of this compound in ethanol
solutions [6]. Our present data on the luminescence in
N,N-dimethylacetamide and heptane reveal both
macroscopic and microscopic solvent effects on the
properties of the fluorescent state. In heptane the
4
0.4
40
0
0
3
6
5
(b)
80
0.8
1
2
4
40
0
0.4
0
35
31
27
23
19
15
3
1
10 , cm
S0
S1 bands are notably structured, while the
emission band half-width is half that of compound VI
(4600 and 8400 cm , respectively). Therewith, the
Fig. 1. Absorption (long-wave band) and fluorescence
spectra in (1, 4) heptane, (2, 5) ethanol, and (3, 6) N,N-
dimethylacetamide at 295 K. (a) 3-(4-Aminophenyl)-1-
phenyl-1-propen-3-one (VI) and (b) 1-(4-aminophenyl)-
3-phenyl-1-propen-3-one (XI).
1
luminescence intensity increases by an order of
magnitude. Apparently, the localization of the excita-
tion energy in the styrene system weakens the per-
*
turbing effect of the n, state. In going from the
hydrocarbon to a more polar solvent, the a absorption
responding band of 4-aminoacetophenone
22700 cm ) [11] by 4000 cm . The energies of the
(
00
maximum of compound XI shifts red, 3300 (ethanol)
1
1
1
and 3500 cm (N,N-dimethylacetamide), and the
T states (ET) for compounds II VI can be estimated
fluorescence band undergo a bathofloric shift by 4000
1
at (18.3 0.2) 103 cm , which is close a value
1
and 3400 cm . In going from ethanol to an aprotic
1
proposed for chalcone (18.0 103 cm [10]). Note
solvent (N,N-dimethylacetamide), the latter band
that our estimates for compounds III and IV are much
lower than those of Reinhardt et al. [5], based on the
results of quenching of photochemical trans cis iso-
merization in solutions at room temperature
1
preserves its shape but shifts blue by 600 cm
(Fig. 1b, spectra 5 and 6), and, what is more, the
quantum yield ( ) increases 15 times. Obviously, the
f
quenching in ethanol is associated with protolytic
reactions in the S1 state, which are favored by N HO
intramolecular bonding [12].
1
( 21000 cm ). The small S T splitting for amine VI
1
(4400 cm ) is presumably associated with the ano-
malous bathofloric shift of the fluorescence band on
freezing, which has been observed, for instance, with
The difference in the luminescent properties of 1st
and 2nd group compounds is most evident in ethanol
glasses at 77 K (Table 2). Compounds II V in these
conditions, like at 295 K, do not fluoresce but exhibit
weak short-lived phosphorescence whose band and
0 0 transition are only slightly affected by the struc-
ture of the ketone moiety. The overall emission spec-
1
4-aminoacetophenone (shift 2000 cm ) [11]. Pro-
bably, such a behavior is explained by appearance in
these conditions of a more planar conformation, which
is explained by a contribution of charge transfer into
the S1 state.
The luminescent properties of compounds VII XI
at 77 K are quite diverse (Table 2). The compounds
all, except for 4-bromophenyl derivative (VII), exhibit
both fluorescence and phosphorescence. Compound
VII exhibits phosphorescence only, with the para-
trum of amine VI was independent on
(313, 366,
ex
and 406 nm) and contained two bands of comparable
intensity (Fig. 2a). The overall luminescence quantum
yield was 0.1. Notable is the fact that such a stong
electron donor as NH2 only slightly affects parameters
of the T S0 transition. The phosphorescence spec-
trum of this compound (Fig. 2a, spectrum 3) is similar,
both in position and vibrational structure (500, 1000,
meters of the T S0 transition and the
/
values
ph
close to those characteristic of 1st group comfpounds.
With VIII XI, the fraction of the long-lived com-
ponent changes from 0.5 to 0.1. The phosphorescence
spectrum is less structured than the fluorescence spec-
trum. The vibration quantum energies for the latter are
1
and 1600 cm ), to those of the other compounds of
this group (Table 2) but shifted red relative to the cor-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

1276
RTISHCHEV et al.
sequences of levels (in the order of growing energy)
[schemes (1) (3)]:
, nm
I, rel. units
500
600
700
(a)
I, rel. units
80
S0 T( *) T(n *) S(n *) S( *),
(1)
(2)
(3)
80
40
1
3
S0 T( *) T(n *) S( *) S(n *),
S0 T( *) S( *) T(n *) S(n *).
40
2
Reactive is the T( *) level. Our estimates for the
energies of the S(n ) and T(n ) states, in the
*
*
0
0
(b)
absence of the possibility of direct measurements, are
80
80
1,2
1
3
23000 25000 and 21500 23000 cm , respectively
[5, 10].
40
0
40
0
The quantum yield of the photochemical trans cis
isomerization (F) of 1st and 2nd group compounds in
N,N-dimethylformamide varies tenfold: from 0.23
(IV) to 0.02 (VI) (Table 1). It is important to note that
the most sensitive to photolysis are compounds II V,
1
22
20
18
16
1
14
3
10 , cm
1
VII, and X, which have ET 17600 cm (Table 2).
Fig. 2. Emission spectra in ethanol glasses (77 K):
(1) overall spectrum, (2) fluorescence, and (3) phos-
The fact that compounds II V and VII do not fluore-
sce suggests realization in them, like in parent chal-
cone I, of scheme (1).
phorescence,
to Fig. 1).
366 nm (for a and b, see the legend
ex
The low value of ph, the values of vibration fre-
quencies in the phosphorescence spectra of com-
pounds II XI, and also, as judjed the low intensity of
luminescence, the higher rate of the T ~~ S0 transi-
tion are likely to result from the nonplanar molecular
structures of chalcone [10] and its derivatives and the
perturbing effect of the C=O group [6]. Concerning
the latter factor, we suppose that such a perturbation is
produced by the vibronic interaction of the T( *) and
1
1100, 1300, and 1400 cm
(
, C H), whereas the
long-lived luminescence spectCru=mC contains two pre-
1
vailing frequencies: 1500 and 1600 cm
( C O). The
1
S T splitting is 6000 7000 cm , which corresponds
to lower S1( *) and T1( *) states but is hardly con-
sistent with the proposed localization of the triplet
energy on the carbonyl moeity. The emission bands
of amine XI are least structured and correspond to
least energy transitions for all 1st and 2nd group com-
*
T(n ) levels, resulting from from overlap of their
pounds (Fig. 2b, spectra 1 3). The
for compound
f
potential surfaces. This effect, as follows from the
theoretical and experimental evidence for azanaphtha-
lene molecules [13, 14], is stronger than those asso-
ciated with dipole and spin orbital interactions. In our
case this conclusion is indirectly evidenced by the fact
XI, measured using a new reference (see Experi-
mental) was 0.65, which is close to the previously
measured value of 0.56 [6]. Thus, about 40% of com-
pound XI molecules at 295 K in the absence of any
other competing processes pass to the T level. The
overall luminescence quantum yield for the other
compounds of the series was lower by an order of
magnitude.
that the highest
value is characteristic of amine XI
ph
which has the lowest T( *) level in the series in
question (Table 2). The fairly strong fluoresce of
compound XI in N,N-dimethylacetamide suggests
realization of scheme (3). Benzoylation of compound
As follows from data in Table 2, the ET values for
2nd group compounds, unlike those for II VI, are
much structure-dependent and vary by 2000 cm :
from 17800 (VII) to 15900 cm (XI). The ET values
for heterocyclic chalcone analogs VIII and IX
1
XI increases ES (energy of the S1 state) by 2000 cm ,
1
quenches the fluorescence by 2 orders of magnitude,
and increases F three times, implying realization of
scheme (2) for compound X.
1
(Table 2) are close to previously reported values
(16700 and 16900 cm , respectively [5]).
Further investigations (Tables 1 and 3) revealed
two more features of the photoreaction. First, in going
from N,N-dimethylacetamide to heptane the F value
for inactive amine VI increased several times, whereas
for most other compounds in the II XI series it
remained invariable. Specifically, the F values for
heterocyclic chalcone analogs III and IV in heptane
1
The ability of chalcone and its derivatives to
photochemical trans cis isomerization, as we pro-
posed in [1], depends both on physical and
chemical factors. The first factor is directly related
to spectral-luminescence properties and assumes three
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

SPECTRAL PROPERTIES AND PHOTOCHEMICAL ACTIVITY
1277
Table 3. Rate of photochemical trans cis isomerization as a function of medium and dissolved gasa
Solvent
[O2]
kq
Comp. no.
ES
F (Ar) F(O2)
kr
kd
ST
T
VI
X
XI
V
VI
X
XI
V
29.0
26.8
25.3
27.8
23.4
24.0
21.4
28.2
23.4
24.3
21.5
1.0
1.0
1.0
1.0
23
19
14
18
1.9
22
1.8
18
4.2
14
19
2.9 7.9 107 2.6 108
7.2
15
0.8
22
1.2
14
2.2
18
9.0
4.2 3.3 107 2.1 108
5.8 3.1 107 1.4 108
40.0
3
3
95%
ethanol
6.4 10
5.4 109
7.7 109
0.9b
1.0
15
7.5 2.4 107 1.1 108
24
4.5 5.2 107 1.7 108
15
2.4 107 4.4 107
N,N-Dimethyl- 4.9 10
acetamidec
VI
X
XI
0.9b
0.4
21
14
a
c
1
1
([O ]) Concentration of dissolved oxygen, M [15]; (k ) diffusion reaction rate constant, l mol
s
, calculated from the viscosity
) quantum yield of population of T
ST
2
q
*
3
1
[16]; (E ) energy of the S(
) level in solution, 10 , cm , from Fig. 1 and Table 1; (
S
2
states; [F(Ar), F(O )] quantum yields of photoreaction in Ar and O , 10 ; ( ) lifetime of the T state in solution, ns; (k , k ) rate
constants of photoreaction and of energy degradation of electron excitation on the T level, respectively, s
2
2
T
r
d
1
b
.
From data of [6].
Data for [O ] and k in dimethylformamide.
2
q
were 0.20 and 0.23, i.e. they are close or coincide
with those in isooctane (0.21 and 0.23 [5]). Second,
the quantum yield of photolysis of inactive com-
pounds VI, VIII, IX, and XI increased 1.5 3-fold in
the absence of oxygen. In particular, the F values for
heterocyclic chalcone analogs VIII and IX in N,N-
dimethylacetamide saturated with argon were 0.08 and
than in heptane, i.e. scheme (2) is realized. As can be
noted the values in the hydrocarbon are the lowest
and the rate constants of competing photoreactions
are the highest compared with ethanol and N,N-di-
methylacetamide. The slightly reduced photochemical
activity compared with the parent chalcone, whose F
is equal to 0.30 and is independent of oxygen content,
T
0.09, respectively, against 0.03 in air. Consequently, is associated with increased ratio kd/kr (rate constants
the reactivity depends not only on ET, but also on the
of energy degradation of electron excitation and of
photoreaction), probably, as a result of the chemical
effect.
lifetime of the T state in the solution ( ). Probably,
T
the two values are interrelated, as it follows from the
above comparative estimates for amine XI at 77 K.
Table 3 compares the photochemical activity of
amines VI and XI and their benzoyl derivatives V and
X in various solvents saturated with argon or oxygen.
Data on photoreaction quenching with oxygen were
For amine XI in N,N-dimethylacetamide, where
scheme (3) is realized and the quantum yield of inter-
system crossing is no higher than 0.4, the probability
of photochemical reaction proved the same as in
heptane. To explain this fact, it will suffice to com-
pare the kd values in the two solvents. The rate of the
T ~~ S0 transition in N,N-dimethylacetamide is 5
times lower than in heptane, which probably results
from >NH O R< intermolecular hydrogen bonding.
With amides X and V, this factor is obviously less im-
portant. Estimation of this factor for amine VI (the
most stable in N,N-dimethylacetamide) is prevented
used to calculate
constants of photoreactions. The following assumpt-
ions were made: O2 has no effect on is inde-
values and the corresponding
T
(
ST
f
pendent of the presence of absence of O2); the latter
value for compound XI in N,N-dimethylacetamide is
the same as in ethanol at 77 K; and reaction with the
1
singlet oxygen O2 formed by quenching of T states
can be neglected [17]. It was found the rate of photo-
isomerization of amides V and X, unlike amines, only
slightly depends on solvents and dissolved gases. For
all the four compounds in heptane and for benzoyl-
by the lack of data on the
value, since, if scheme
(2) is realized, absorbed eneSrTgy can be lost at steps a
and b [scheme (4)] [18].
*
*
a
b
amine V in polar solvents, ES( , ) > ES(n, ), i.e.
scheme (1) is realized: ST and F have limiting values.
The fact that amine VI falls out of the series of 1st
group compounds II VI in terms of F in N,N-di-
*
S( *) ~
T( *).
~
(4)
T(n
)
~
~
In going from N,N-dimethylacetamide to ethanol,
F for both amines reduces manyfold, most strongly
methylacetamide (vide supra) can now be explained for 2nd group amine XI. The lack of correlation of
1
by that in this solvent its ES is about 6000 cm lower
this effect with
suggests that the energy is dis-
T
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

1278
RTISHCHEV et al.
in 1-[4-(benzoylamino)phenyl]-3-phenyl-2-propen-3-
, nm
500
one (X) of the phenyl substituent by 4-bromophenyl
(compound XII), 2-furyl (compound XIII), and 2-
thienyl (compound XIV) has almost no effect on the
optical properties of the solutions at 295 K, except
I,
400
I, rel. units
600 700
(a)
rel.
units
80
1
80
3
3
2
for a slight reduction of the value (Tables 1 and 2).
f
40
The fluorescence and phosphorescence bands of
compound XIV in ethanol glasses (77 K) (Fig. 3a)
correspond to radiation transitions in monosubstituted
derivative X, i.e. the excitation energy is localized
mostly on the styryl moiety. However, the slightly
changed pattern of the S1 S0 band and doubled
relative efficiency of the T S0 transition (Fig. 3a,
40
1
2
0
0
80
1
1
(b)
80
2
2
40
0
40
0
spectra 1 and 2), as well as reduced
value for the
ph
first of the listed compounds compared with the
second point to perturbing effect of 2-acetylheteryl,
i.e. to interaction of the amide group and 2-thienyl in
compound XIV. The slightly reduced F values for
compounds XIII and XIV compared with X, which
have nothing to do with fluorescence quenching (cf.
XII and XIII) (Table 1), are also associated with this
interaction.
25 23 21
19 17 15 13
3
1
10 , cm
Fig. 3. Overall emission spectra of (1) disubstituted and
(2, 3) monosubstituted chalcones in ethanol glasses
(77 K),
phenyl)-3-(2-thienyl)-2-propen-3-one (XIV), (2) 1-(4-
(benzoylamino)phenyl)-3-phenyl-2-propen-3-one (X),
and (3) 1-phenyl-3-(2-thienyl)-2-propen-3-one (IV); and
(b): (1) 3-[4-(acetylamino)phenyl)-1-(2-thienyl)-2-
320 380 nm. (a): (1) 1-[4-(Benzoylamino)-
ex
Compounds XX XXII are derivatives of 3-[4-
(benzoylamino)phenyl)-1-phenyl-2-propen-3-one (V)
and structural isomers of compounds XII XIV. Spec-
trally and photochemically, compounds XXI and
XXII with a heterocyclic radical R2 are generally
similar to compounds XIII and XIV, i.e. the key
chromophoric system is heterylmethylene acetone.
Thus, the emission bands (77 K) of compound XXII
are similar to those of monosubstituted IX but not of
compound V (Table. 2; Fig. 3b, curves 1 3). Interac-
tion between R1 and R2 shows up in a red shift
propen-3-one (XXII), (2) 3-phenyl-1-(2-thienyl)-2-
propen-3-one (IX), and (3) 3-[4-(benzoylamino)phenyl)-
1-phenyl-2-propen-3-one (V).
sipated before the molecule passes to the T level. On
the other hand, in view of the above-noted features of
luminescence in this solvent (Table 1; Fig. 1b), we
can suppose that the processes that compete with
fluorescence and the S1 ~~ T transition are quench-
ing of the S1 state both by cleavage of an N HO
intermolecular hydrogen bond and by adiabatic proton
phototransfer [12]. With amine XI, the latter process
is obviously prevailing.
1
(600 cm ) of the S1 S0 band and a blue shift (200
1
cm ) of the T S0 band, as well as in a slightly
increased
/
value compared with IX. Absorption
ph
f
bands of disubstituted XXI and XXII are shifted
1
bathochromically (500 cm ) and are 1.1 1.5 times
The rate of the photochemical trans cis isomeriza-
tion for 1st and 2nd group compounds generally
depends on ES, ET, and ST, and on the environment
stronger compared with monosubstituted VIII and IX.
At the same time, the photochemical activity de-
creases 1.3 1.7 times (Table 1).
which strongly affects both
reaction pattern.
and the overall photo-
T
If the styryl moiety of a disubstituted chalcone
contains a weakly electron-donor substituent (R2 =
4-BrC6H4) and the ketone moiety, a benzamide [R1 =
4(PhCONH)C6H4] (XX) or an aminophenyl radical
(R1 = 4-NH2C6H4) (XXIII), the key chromophoric
system is acetylaryl which is modeled by the corres-
ponding monosubstituted compound, i.e. amide V and
amine VI. As a result, the spectral luminescent pro-
perties and the photochemical activity of both pairs
of compounds are similar (Tables 1 and 2). The fluore-
scence band of compound XX at 77 K can be used to
estimate ES for its nonflurescing model compound V,
which leads to a reasonable estimate for the S T
Separation of the chemical factor from the
variety of photophysical parameters affecting F and
depending, in their turn, the chemical structure of
R1 and R2, seems not quite correct. The only substi-
tuent that exerts a minimal effect on the photo-
chemical parameters is 4-Br in each of the chalcone
phenyl rings (Tables 1 and 2). The F values for
structurally similar monosubstituted compounds II
and VII are almost equal to each other, i.e. here the
chemical factor is also not obvious.
Disubstituted chalcones XII XXIII. Replacement
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

SPECTRAL PROPERTIES AND PHOTOCHEMICAL ACTIVITY
1279
1
splitting, EST (6200 cm ) (Table 2). Apparently, for
compound XX, like for V, scheme (1) is realized with
phenyl analog (R1 = Ph) [1]. However, unlike the
latter compound (F 0.03), compound XIX undergoes
3
the highest
and F values.
no isomerization on excitation (F 10 ), apparently,
ST
because of cross conjugation which is stronger on the
T level.
The key system in the fluorescing disubstituted
chalcones XV XIX, derivatives of 1-(4-aminophenyl)-
3-phenyl-2-propen-3-one (XI), is the styrene system.
In their optical and photochemical properties they fit
scheme (3), which shows up in strong fluorescence
and a low F value (Tables 1 and 2). Since these com-
pounds exhibit no phosphorescence, in Table 2 we
give the ET values estimated under the assumption
that XV XIX have the same S T splitting as parent
amine XI. The fact that compound XIX has the lowest
The resulting data allow us to conclude that the
properties of the disubstituted chalcones depends
primarily on the structure of the arylmethylene (hete-
rylmethylene) group of the acetone moiety (further
evidence for this conclusion is provided by a 2 3-
fold increase in F for all inactive disubstituted
chalcones in deaerated solutions) and that the inter-
action of cross-conjugated chromophores in their
molecules exerts a stronger perturbing effect on the T
level compared with the S1 level.
1
ET value (14.8 103 cm ) is consistent with our
previous results for 1-(4-dimethylaminophenyl)-3-
phenyl-2-propen-3-one [1].
EXPERIMENTAL
The trends in fluorescent properties in the series
R1 = Ph (XI) 4-FC6H4 (XV) 4-BrC6H4 (XVI) 2-furyl
(XVII) 2-thienyl (XVIII) in N,N-dimethylacetamide
(Table 1) are similar to those observed earlier [3] in
toluene for , -unsaturated ketones derived from
N,N-dimethylaniline. It is suggested [3, 19] that the
long-wave band of the latter is formed by intermole-
The electronic absorption spectra were measured
on a Specord M-400 spectrophotometer. The NMR
spectra were obtained on a Bruker AC-200 spectro-
meter.
Luminescence measurements were performed on
cular charge transfer from the NMe2 group to carbonyl. the apparatus and by the procedures described in
Therefore, the ability of the disubstitued chalcones to
fluorescence depends on whether this process is
favored or unfavored by the substituent in the ketone
moiety. Halogen characteristically exhibits here
acceptor properties; as a result, replacement of phenyl
[20, 21]. The fluorescence references at 295 K were
quinine sulfate in 0.1 N H2SO4 ( 0.55) ( 313 and
366 nm) and 3-aminophthalimide fin 0.1 N eHx2SO4 (
f
0.45) (
406 nm) [22]. The luminescence reference
ex
in measurements in ethanol glasses (77 K) was 6-car-
(compound XI) by 4-bromophenyl (compound XVI)
boxy-2-(4-aminophenyl)benzothiazole ( 0.85) (
ex
red shifts S0
S1 bands (500 and 800 cm ) and
366 nm) [23]. The relative errors in f were 10%
1
f
increases 1.4-fold the intensity of the radiation transi-
tion. Therewith, the photochemical activity decreases
6-fold, probably, on account of the heavy atom in-
duced 4-fold increase in the kd value. Compounds
XVII and XVIII exhibit similar properties. Thus,
with the latter compound, the efficiency of lumines-
cence increases 1.8-fold and the F value decreases
3.2-fold. The strongest fluorescence is characteristic
of 1-[4-(dimethylamino)phenyl)-3-(2-thienyl)-2-
propen-3-one (XIX) which is close in photophysical
properties, including the ET value (vide supra), to the
(295 K) and 20% (77 K).
The equipment and technique of the photochemical
experiment were described in [6, 17]. The relative
error in F was 15%.
Compounds I XXIII were obtained as described
in [24, 25] by alkaline condensation of acetophenone
and the corresponding aldehydes. Nitro compounds
were reduced with SnCl2 7H2O in HCl. The melting
1
points and the H NMR spectra are given in Table 4.
Table 4. Melting points and 1H NMR spectra of chalcones I XXIII
Comp.
mp,
C
1H NMR spectrum (DMSO), , ppm (J, Hz)
no.
I
II
III
58 59
101 102
85 86
[26]
8.10 d (2H), 7.95 7.83 m (2H), 7.93 d (1H), 7.79 d (2H), 7.75 d (1H), 7.5 7.40 m (3H)
8.07 d (1H), 7.92 7.78 m (3H), 7.72 d.d (2H, CH=CH, JHH 16.7), 7.6 7.4 m (3H),
6.79 d.d (1H, OCH)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

1280
RTISHCHEV et al.
Table 4. (Contd.)
Comp.
mp,
C
1H NMR spectrum (DMSO), , ppm (J, Hz)
no.
IV
82 83
8.33 d (1H), 8.06 d (1H), 7.95 7.8 m (3H), 7.73 d (1H, CH=CH), 7.55 7.4 m (3H), 7.33 d.d
(1H, SCH)
V
197 198
107 108
10.51 s (1H, NH), 8.2 d (2H), 8.1 7.8 m (7H), 7.73 d (1H, CH=CH, JHH 15.8), 7.68
7.4 m (6H)
8.0 7.76 m (4H), 7.92 d (2H), 7.76 7.87 m (2H), 7.6 d (1H, CH=CH, JHH 15.9), 7.35
7.50 m (3H), 6.6 d (2H), 6.15 br.s (2H, NH2)
VI
VII
VIII
124 125
42 43
8.15 d (2H), 7.98 d (1H, CH=CH, JHH 15.9), 7.76 d (2H), 7.79 7.49 m (6H)
8.06 d (2H), 7.92 d (1H, O CH), 7.75 7.15 m (5H), 7.51 d (1H, CH=CH, JHH 15.3),
7.12 d (1H), 6.69 d.d (1H)
IX
57.5 58.5
8.08 d (2H), 7.91 d (1H, CH=CH, JHH 15.9), 7.79 d (1H, S CH), 7.74 7.5 m (5H),
7.2 d.d (1H)
X
XI
XII
187 188
153.5 154
202 203
10.48 s (1H, NH), 8.15 d (2H), 7.93 d (2H), 7.9 s (4H), 7.8 d (1H), 7.73 7.47 m (7H)
8.08 d (2H), 7.46 7.12 m (7H), 6.59 d (2H), 5.98 br.s (2H, NH2)
10.49 s (1H, NH), 8.09 d (2H), 7.97 d (2H), 7.9 s (4H), 7.82 d (2H), 7.8 d (1H, CH=CH,
JHH 15.2), 7.73 d (1H, CH=CH, JHH 15.2)
XIII
XIV
XV
213 214
215 216
134 135
154 155
142 143
174 175
114 115
10.37 s (1H, NH), 8.03 7.93 m (3H), 7.91 d (2H), 7.77 d (2H), 7.71 7.45 m (6H),
6.71 d.d (1H)
10.48 s (1H, NH), 8.31 d (1H), 8.05 d (1H), 7.97 d (2H), 7.9 s (4H), 7.83 d (1H, CH=CH,
JHH 15.9), 7.70 d (1H, CH=CH, JHH 15.9)
8.17 d.d (2H), 7.64 d (1H), 7.56 d (2H), 7.53 d (1H), 7.35 d. d (2H), 6.59 d (2H),
5.92 br.s (2H, NH2)
XVI
XVII
XVIII
XIX
(CDCl3), 7.87 d (2H), 7.76 d (1H, CH=CH), 7.61 d (2H), 7.46 d (2H), 7.28 d (1H, CH=CH),
6.67 d (2H, NH2)
7.88 d (1H), 7.58 d (1H, CH=CH, JHH 15.3), 7.48 d (1H), 7.45 d (2H), 7.25 d (1H,
CH=CH, JHH 15.3), 6.66 d.d (1H), 6.58 d (2H), 5.75 br.s (2H, NH2)
7.81 d (1H, CH=CH, JHH 15.3), 7.49 d (2H), 7.49 d (2H), 7.24 d (1H, CH=CH, JHH
15.3), 6.69 d (2H), 4.03 ush. s (2H, NH2)
8.22 d (1H), 7.98 d (1H, S CH), 7.7 d (2H), 7.67 d (1H, CH=CH, JHH 16.2), 7.56 d
(1H, CH=CH, JHH 16.2), 7.28 d.d (1H), 6.74 d (2H), 3.06 s [6H, N(CH3)2]
10.61 s (1H, NH), 8.21 d (2H), 8.1 7.91 m (5H), 7.87 d (2H), 7.78 7.48 m (6H)
10.1 s (1H, NH), 8.25 d (2H), 7.74 d (2H), 7.53 s (2H), 7.01 s (1H), 6.69 d.d (1H),
2.08 s (3H, CH3)
XX
XXI
244.5 245.5
145 146
XXII
164 165
172 173
10.33 s (1H, NH), 8.08 d (2H), 7.89 d (1H, CH=CH, JHH 15.4), 7.79 d (1H), 7.56 d
(1H, CH=CH, JHH 15.4), 7.18 d.d (1H), 2.08 (3H, CH3)
7.92 d (2H), 7.90 d (1H), 7.80 d (2H), 7.62 d (2H), 7.56 d (1H), 6.62 d (2H), 6.16 br.s
(2H, NH2)
XXIII
2. Tsukerman, S.V., Maslennikova, V.P., Nikitchen-
ACKNOWLEDGMENTS
ko, V.M., and Lavrushin, V.F., Zh. Prikl. Spektrosk.,
1970, vol. 12, no. 1, pp. 91 96.
The work was financially supported by the Russian
Foundation for Basic Research (project no. 98-03-
33289).
3. Tsukerman, S.V., Maslennikova, V.P., and Lavru-
shin, V.F., Opt. Spektrosk., 1967, vol. 23, no. 3,
pp. 396 402.
REFERENCES
4. Gustav, K., Bartsen, U., and Karnitzschy, K.,
Z. Chem., 1989, vol. 29, no. 6, pp. 213 214.
1. Kudryavtsev, V.V., Rtishchev, N.I., Nosova, G.N.,
Solovskaya, N.A., Luk’yashina, V.A., and Dobro-
dumov, A.V., Zh. Obshch. Khim., 2000, vol. 70, no. 8,
pp. 1358 1367.
5. Reinkhardt, M., Mitina, V.G., Zadorozhnyi, B.A., and
Lavrushin, V.F., Zh. Obshch. Khim., 1978, vol. 48,
no. 12, pp. 2759 2764.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001

SPECTRAL PROPERTIES AND PHOTOCHEMICAL ACTIVITY
1281
17. Kudryavtsev, V.V., Nosova, G.N., Solovskaya, N.A.,
Dobrodumov, A.V., Rtishchev, N.I., and Frolov, A.N.,
Zh. Org. Khim., 1995, vol. 31, no. 4, pp. 558 564.
6. Nosova, G.I., Rtishchev, N.I., Solovskaya, N.A.,
Dobrodumov, A.V., Luk’yashina, V.A., and Kudryav-
tsev, V.V., Zh. Obshch. Khim., 1997, vol. 67, no. 4,
pp. 661 670.
18. Rtishchev, N.I., Dobrodei, A.N., and El’tsov, A.V.,
Zh. Obshch. Khim., 1999, vol. 69, no. 10, pp. 1731
1742.
7. Sukhorukov, A.A., Zadorozhnyi, B.A., and Lavru-
shin, V.F., Teor. Eksp. Khim., 1970, vol. 6, no. 5,
pp. 602 607.
19. Nikitina, A.N., Fedyunina, T.M., and Umirzakov, B.,
8. Reinkhardt, M., Sukhorukov, A.A., Raushal’, A., and
Lavrushin, V.F., Khim. Geterotsikl. Soedin., 1977,
no. 9, pp. 1202 1205.
Opt. Spektrosk., 1973, vol. 34, no. 2, pp. 289 293.
20. Rtishchev, N.I., El’tsov, A.V., Kvitko, I.Ya., and
Alam, L.V., Zh. Obshch. Khim., 1980, vol. 50, no. 9,
pp. 2070 2085.
9. Sukhorukov, A.A., Lavrushina, O.V., Grif, V.Kh.,
Dzyuba, V.P., Pedchenko, N.F., Zadorozhnyi, B.A.,
and Lavrushin, V.F., Zh. Obshch. Khim., 1978,
vol. 48, no. 2, pp. 377 385.
21. Rtishchev, N.I., Lebedeva, G.K., Kvitko, I.Ya., and
El’tsov, A.V., Zh. Obshch. Khim., 1988, vol. 58,
no. 9, pp. 2148 2163.
10. Belaits, I.L., Kunavin, N.I., Nurmukhametov, R.N.,
and Podorol’skaya, A.E., Opt. Spektrosk., 1975,
vol. 38, no. 5, pp. 908 912.
22. Stolyarov, K.P., Solov’eva, L.A., and Firyulina, V.V.,
Vestn. Leningr. Gos. Univ., 1982, vol. 22, issue 4,
pp. 73 79.
11. Yamaguchi, G., Kakinoki, Y., and Tsubomura, H.,
Bull. Chem. Soc. Jpn., 1967, vol. 40, no. 3, pp. 526
531.
23. Rtishchev, N.I., Kvitko, I.Ya., Nagorskaya, L.P., and
El’tsov, A.V., Zh. Obshch. Khim., 1993, vol. 63, no. 2,
pp. 429 438.
12. Martynov, I.Yu., Demyashkevich, A.B., Uzhi-
nov, B.M., and Kuz’min, M.G., Usp. Khim., 1977,
vol. 46, no. 1, pp. 3 31.
13. Agren, H., Minaev, B.F., and Knuts, S., J. Phys.
Chem., 1994, vol. 98, no. 15, pp. 3943 3949.
14. Knuts, S., Agren, H., and Minaev, B.F., J. Mol. Struct.
(Teochem), 1994, vol. 311, pp. 185 197.
24. Davey, W. and Gwilt, J.R., J. Chem. Soc., 1957,
pp. 1008 1014.
25. Lavrushin, V.F., Tsukerman, S.V., and Artemen-
ko, A.I., Zh. Obshch. Khim., 1962, vol. 32, no. 4,
pp. 1324 1329.
15. Landolt Bornstein, Zahlenwerte und Funktionen aus
Physik, Chemie, Astronomie, Geophysik und Technik,
Berlin: Springer, 1962, vol II, part 2, pp. 74 75.
16. Einfuhrung in die Photochemie, Becker, H.G.O., Ed.,
Berlin: Wissenschaften, 1976.
26. Dictionary of Organic Compounds, Heilbron, I. and
Bunbury, H.M., Eds., London: Eyre and Spottiswood,
1946, vol. 1. Translated under the title Slovar’
organicheskikh soedinenii, Moscow: Inostrannaya
Literatura, 1949, vol. 1, p. 415.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 8 2001