Molecular structure and mesomorphism in the series of discotic esters derived from benzene, triazine, biphenyl, and triphenylene

Article abstract of DOI:10.1134/S1070363207010148

New mesogenic discotic triazine-based esters were synthesized and shown to form a low-temperature monotropic columnar mesophase. Using as examples the newly synthesized compounds and previously prepared discotic esters on the basis of benzene, biphenyl, a

Full text of DOI:10.1134/S1070363207010148

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 1, pp. 103 110.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
O.B. Akopova, T.V. Frolova, N.V. Usol’tseva, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 1, pp. 111 119.
Molecular Structure and Mesomorphism
in the Series of Discotic Esters Derived from Benzene,
Triazine, Biphenyl, and Triphenylene
O. B. Akopova, T. V. Frolova, and N. V. Usol’tseva
Ivanovo State University,
ul. Ermaka 39, Ivanovo, 153000 Russia
e-mail: akopov@dsn.ru
Received May 23, 2006
Abstract New mesogenic discotic triazine-based esters were synthesized and shown to form a low-
temperature monotropic columnar mesophase. Using as examples the newly synthesized compounds and
previously prepared discotic esters on the basis of benzene, biphenyl, and triphenylene, the effects of the
nature and size of the central fragment and the number, position, length, and rigidity of peripheral substituents
therein on the mesomorphic properties (in particular, the ability to form columnar and nematic mesophases)
were examined. The main structural factors stabilizing columnar and nematic mesophases were revealed.
Nematic mesomorphism was shown to be favored by increased size of the central fragment of the discogen
molecule and by the presence of cyclohexane fragments in peripheral substituents.
DOI: 10.1134/S1070363207010148
Discotic mesogens (DM) attract researchers’ atten-
tion due to their prospective use as organic materials
for new generation of electronic devices [1]. Studies
on these compounds as self-organized systems are
also interesting from the viewpoint of supramolecular
chemistry and nanotechnology [2]. Search for qualita-
tive and quantitative relations between their molecular
structure and mesomorphic properties is important for
purposeful synthesis of such mesogens. The principal
aspects of studies on discotic mesogens were for-
mulated in [3]. In the present work we examined a
new series of compounds having structures of type
I V and analyzed the effects of such structural factors
as the nature and size of the central fragment and the
position, length, number, and rigidity of peripheral
substituents on their mesomorphic properties.
detailed procedure for the synthesis of the correspond-
ing derivative and its identification data are given in
Experimental.
The data of differential scanning calorimetry (DSC)
for series II compounds showed the following phase
transitions: crystal isotropic liquid on heating and
isotropic liquid mesophase on third cooling. The
second minimum typical of the transition meso-
phase crystal was not observed on cooling, for all
mesomorphic homologs crystallize below room
temperature. The results of DSC are consistent with
the thermomicroscopic observations (Table 2).
Examination of samples of compound IIe and
2,3,6,7,10,11-hexaoctyloxytriphenylene (IX) on slow
cooling in the vicinity of the phase transition from
isotropic liquid to mesophase showed that their tex-
tures are similar (Fig. 1). The supramolecular structure
of triphenylene ether IX was reliably identified as
hexagonal columnar (Colh) [3]. On the basis of the
similarity in textures of compounds IX and II (Fig. 1)
and the results of preliminary prediction related to the
type of mesomorphism [12], we believe that the latter
is characterized by the same packing of molecules in
the mesophase as that found for IX, the more so both
these compounds are miscible in the liquid crystalline
state.
Discotic mesogens I V contain bridging ester
moieties and central fragments having different sizes.
Compounds I and III (Table 1) were synthesized pre-
viously [4 6] taking into account the results of pre-
liminary prediction of a definite type of mesomorphic
properties on the basis of molecular parameters [10,
11]. The data on mesomorphic properties of triphe-
nylene derivatives IV and V (Table 1) were taken
from [7, 9]. 1,3,5-Triazine derivatives II were syn-
thesized according to Scheme 1.
In keeping with the preliminary predictions made
in [12], liquid crystalline properties in this series of
compounds can be found starting from n = 10. A
The effect of the nature of the central fragment
on mesomorphic properties was examined using
103

104
AKOPOVA et al.
Scheme 1.
R1
N
R
R
N
N
R2
R2
R
R3
II
I
OCOR
R
R
R
N
OCOR
N
R
N
N
ROCO
ROCO
OCOR
R
OCOR
N
OCOR
N
OCOR
OCOR
R
OCOR
III
ROCO
IV
V
I, R3 = H, R1 = R2 = OCOC6H4OCnH2n+1, n = 6 (a), 7 (b), 8 (c), 9 (d), 11 (e); R3 = H, R1 = R2 = C(O)OC6H4OCnH2n+1
n = 9 (f); R3 = H, R1 = R2 = OCOC6H4C6H11-cyclo (g); R1 = H, R2 = R3 = OCOC6H4C6H11-cyclo (h).
,
R1C(O)O
H------O
O(O)CR1, R1 = CnC2n+1, n = 8 (a), 9 (b), 10 (c), 11 (d), 12 (e), 14 (f), 16 (g).
C
II, R = N
CH==CH
R1C(O)O
III, R = C6H4OCnH2n+1, n = 6 (a), 8 (b), 11 (c), R = C6H4 C6H11-cyclo (d). IV, R = C6H4OCnH2n+1, n = 6 (a), 8 (b),
10 (c), 11 (d), R = C6H4 C6H11-cyclo (e). V, R = C6H4 H19.
the series including polysubstituted benzene Ie, 1,3,5-
triazine IId, 1,3,3 5,5 -pentahydroxybiphenyl deriva-
tive IIIc, triphenylene IVd, and compound V (Table
3). Replacement of carbon atoms in the central frag-
ment of 1,3,5-trihydroxybenzene ester Ie by nitrogen
and of the ester groups by enamino (1,3,5-triazine IId)
gives rise to monotropic columnar mesophase,
whereas 1,3,5-tris(4-undecyloxybenzoyloxy)benzene
(Ie) possesses no liquid crystalline properties
(Table 1). We believe that the appearance of columnar
mesophase is favored by the presence of intermole-
cular hydrogen bonds between the enamino groups of
(a)
(b)
Fig. 1. Growth of nuclei as regular hexagons, cooling cycle: (a) 1,3,5-trazine derivative IIe, 34.3 C, parallel nicols, magnifica-
tion 400; (b) 2,3,6,7,10,11-hexaoctyloxytriphenylene (IX), 78 C, crossed nicols, magnification 250 [3].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

MOLECULAR STRUCTURE AND MESOMORPHISM
105
Table 1. Phase transition temperatures ( C) of discotic mesogens I and III Va
Compound no.
n
Cr M1
M1 M2
M2 ND
ND
I
Reference
Ia
Ib
Ic
Id
Ie
If
Ig
Ih
IIIa
IIIb
IIIc
IIId
IVa
IVb
IVc
IVd
IVe
V
6
7
8
9
60b
54b
54
66
58
[4]
[5]
[5]
[5]
[5]
[5]
[5]
[4]
[4]
[6]
[6]
[4]
[7]
[7]
[7]
[7]
[9]
[8]
48
c
11
9
6-cyclo
6-cyclo
47d
140
75
133
137
102
157
212
214
174
258
274
244
212
185
340
6
8
<20d
<20d
<20d
93
74
79
240
193
168
191
179
288
11
6-cyclo
6
8
10
11
6-cyclo
9
186e
152f
142g
145g
81
a
b
Hereinafter, Cr stands for crystalline phase, M for mesophase, N for nematic discotic, and I for isotropic liquid. The structure of
D
c
d
e
the mesophase was not reliably determined. Predicted as nonmesogen. Columnar mesophase (Col). Columnar tilted mesophase
f
g
(Col ). Columnar rectangular mesophase (Col ).
Columnar rectangular disordered mesophase (Col ).
rd
t
r
neighboring triazine II molecules. This assumption is
indirectly supported by the results reported in [13 16].
It was noted in these publications that hydrogen
bonding between neighboring molecules in a stack
favors ordering of mesophase formed by compounds
having similar groups at the central fragment. By
contrast, hexakis(4-nonylphenyl)dipyrazino[2,3-f:2 ,3 -
h]quinoxaline (V) [9] which, like triazines II, contain
nitrogen atoms in the central fragment but no enamine
spacers does not form mesophase (Table 3). Thus, the
presence of bridging enamino group in the series of
triazine derivatives II is a factor stabilizing columnar
mesophase. On the other hand, increase in the electron
density on the central fragment in the series of ben-
zene, biphenyl, and triphenylene derivatives: 0.118
(I) < 0.175 (III) < 0.607 (IV) stabilizes nematic
mesophase.
Effect of the number of benzene rings in a disc-
like molecule and the size of its central fragment.
Table 4 compares polysubstituted derivatives of ben-
zene (Ic), biphenyl (IIIb), and triphenylene (IVb). It
Table 2. Phase transition temperatures of homologous
1,3,5-triazine-based discogens II
Table 3. Temperature ranges of mesophases and inematic
phase of compounds I V
Comp.
no.
Temperature range,
C
n
Cr Ma
M
I
Comp.
no.
Mesophase
mesophase
nematic phase
IIa
IIb
IIc
IId
IIe
IIf
8
9
25.0
54.0
Ie
Nonmesogen
Col
0
>25
>154
40
0
0
10
11
12
14
16
(29.0); (29.5)b
(25.0)
33.0; 33.6b
28
IId
(35.0); (35.5)b
(47)
48.3; 42.5b
52.6
IIIc Col, ND
IVd Colr, ND
Nonmesogen
95
6
IIg
(54.0); (56.1)b
62.3; 61.7b
a
The temperature of monotropic phase transition is given in
b
V
0
0
parentheses.
DSC data.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

106
AKOPOVA et al.
OH
OH
Na,
O
Na
O
COCH3
OH
C
ethyl formate
(C2H5)2O
20 C
HO
HO
CH=CH
VI
VII
OH
OH
HO
O==C
H
HO
C C
H
OH
H
C
C
H
O
R1COCl
melamine
N
N C
H N
H
(1)
IIa IIg,
30 C, yield 30%
(1) CH3OH, DMF
(2) CH3COOH
N
N
N
H C
H C
H
O
C
OH
HO
OH
VIII
R1 = C8H17 (a), C9H19 (b), C10H21 (c), C11H23 (d), C12H25 (e), C14H29 (f), C16H32 (g).
is seen that increase in the number of benzene rings in
The effect of bridging groups on liquid crystal-
the central fragment in going from benzene deriva- line properties was analyzed using as examples esters
tives Ia Ie to substituted biphenyls IIIa IIIc and tri- Ia If with different oxygen carbon sequences in the
phenylenes IVa IVd leads to appearance of two-di- ester groups (the role of the bridging group in en-
mensional nematic-ordered phase (ND) in addition to aminoketone triazine derivative II was discussed
columnar mesophase (Col), i.e., esters like IIIa IIIc above). Not all esters Ia Ie are mesomorphic. Two-
and IVa IVd exhibit polymorphism. On the other dimensional columnar mesophase was observed only
hand, the greater the cross-sectional area of the central for two members of this homologous series on heating
XY
cf
fragment in the XY plane (S ) of a discogen molecule, in a narrow temperature range [5]. Trimesinic acid
the broader the mesophase temperature range ( Tmes
and the higher the clearing temperature, including that dimensional columnar structures both on heating and
of ND mesophase (Table 4). on cooling, and the corresponding temperature ranges
)
derivatives If with inverted ester linkers give two-
Table 4. Effects of the number of benzene rings and the size of the central fragment on the mesomorphic properties in the
series of compounds I, III, and IV
Temperature range,
C
a
XY
Comp. no.
Mesophase
Number of benzene rings
S ,
cf
mesophase
nematic phase
Ic
IIIb
IVb
Nonmesogen
Col, ND
Colr, ND
1
2
3
0
>214
92
0
140
76
62.23
102.42
85.25
a
XY
S
is the cross-sectional area of the central fragment in the XY plane.
cf
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

MOLECULAR STRUCTURE AND MESOMORPHISM
(a)
107
(b)
Fig. 2. Electron density distribution over the central fragments of ester molecules (a) Ia Ie and (b) If; averaged electron
densities on the central fragment e
=
1.97 and 0.34 eV, respectively.
cf
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

108
AKOPOVA et al.
Table 5. Effect of the nature of the lateral substituent on
the mesomorphic properties in the series of compounds I,
III, and IV
The effect of the lateral substituent nature is
clearly seen while comparing compounds I, III, and
IV, where R = OCC6H4OC6H13 or OCC6H4C6H11-
cyclo (Table 5). Replacement of the alkoxy group in
the series of polysubstituted 1,3,5-trihydroxybenzene
derivatives Ia Ie by cyclohexane fragment (compound
Ig) favors formation of more thermally stable nematic
phase whose temperature range approaches that ty-
pical of Ia (Table 5). By contrast, introduction of a
cyclohexane fragment into the lateral substituent of
1,2,3-trihydroxybenzenebased ester Ih gives rise to
bimesomorphism with simultaneous increase in the
thermal stability of the mesophase (Table 5). Unlike
1,3,3 ,5,5 -pentakis(hexyloxybenzoyloxy)biphenyl
(IIIa), 1,3,3 ,5,5 pentakis(cyclohexylbenzyl)biphenyl
(IIId) shows only one mesomorphic transition to ND
phase which exists in a narrower temperature range
but is more thermally stable. An analogous replace-
ment in triphenylene derivative IVe leads to disap-
pearance of two-dimensional columnar mesophase
while nematic phase (ND) is conserved but with a
higher clearing temperature than that for alkoxy-
substituted triphenylene-based benzoates IVa IVd.
Thus, the effect of the nature of lateral substituents on
the mesomorphic properties of the compounds under
study cannot be predicted a priori, and it strongly
depends on the structure of the central fragment and
position of the lateral substituent.
Temperature range,
C
Comp.
no.
Mesophase
mesophase
nematic phase
Ia
Ig
ND
ND
6
4
6
4
Ih
M1, M2
Colr, ND
ND
Colt, ND
ND
55
>192
12
17
>119
12
IIIa
IIId
IVa
IVe
88
52
81
52
are broader than those found for alkoxybenzoates
Ia Ie [5]. The observed behavior of esters Ia Ie and
If may be rationalized in terms of different electron
density distribution over the molecular framework
which (with account taken of microsegregation) in-
cludes the central and ester linkers. Semiempirical
MM+ and PM3 calculations (HyperChem Pro 6.0)
showed that the electron density on the central
fragment of molecule I (R3 = H, R1 = R2
=
OCOC6H4OCH3) is lower than in I (R3 = H, R1 =
R2 = C(O)OC6H4OCH3] (Fig. 2). On the other hand,
the specific electron density, i.e., the electron density
per unit area of the central fragment cross-section in
Increase in the number of lateral substituents
and the size of the central fragment in the series of
symmetrically substituted cyclohexyl derivatives of
benzene (Ig), biphenyl (IIId), and triphenylene (IVe)
leads to increase of the clearing temperature and
broadening of the temperature range of nematic phase.
It may be presumed that introduction of a relatively
rigid cyclohexane fragment into peripheral substi-
tuents containing no flexible hydrocarbon moieties
gives rise to compounds which are characterized
mainly by nematic mesomorphism. The results of
studies on discotic mesogens having both cyclohexane
fragments and flexible hydrocarbon radicals in the
lateral substituents [3] showed that such structures
favor formation of only columnar mesophase. In our
case, the observation of only nematic phase may be
rationalized in terms of the presence of bulky cyclic
fragments at the periphery of disc-shaped molecule
and the absence of main factors favoring microsegrega-
tion [17] which should maintain supramolecular
columnar ordering. Here, the shape anisometry is
responsible for the conservation of only mutual spatial
orientation of particular molecules which form
nematic phase. We were thus the first to reveal a
positive role of a rigid cyclohexane fragment in the
lateral substituent in the formation of nematic phase.
the XY plane (eTsF/STXsYF) is larger for esters of the
XY
2
second type: C(O)O , eTsF/S
=
0.046 eVE ;
TsF
XY
2
OCO , ecf/S
=
0.005 eVE [4]. Presumably,
cf
increased specific electron density on the central
fragment of trimesinic acid derivatives If should
enhance
interactions between molecules in a
column, i.e., should favor their stacking, as is in fact
observed. In this case, enantiotropic mesomorphism is
characterized by higher clearing temperatures (as
compared to Ia Ie) and broader temperature ranges.
The effects of the nature, number, position, and
length of substituents was traced in the series of
benzene (I), triazine (II), biphenyl (III), and triphe-
nylene derivatives (IV). Within the homologous series
of polysubstituted 1,3,5-triazines II, the length of the
hydrocarbon radical exerts an appreciable effect on
the type of textures formed: they vary from rod-like
(n = 10 12) to looped columnar helical (n = 14) and
nongeometric (n = 16). The type of texture, as well as
the number of mesophases and their type, of esters
IIIa IIIc derived from 1,3,3 ,5,5 -pentahydroxybi-
phenyl does not change as the hydrocarbon radical
becomes longer, but an even odd dependence of the
ND I transition temperature is observed [6].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

MOLECULAR STRUCTURE AND MESOMORPHISM
109
Discotic mesogens Ig and Ih having similar lateral
substituents but in different positions of the benzene
ring (1, 3, 5 and 1, 2, 3, respectively) showed some
differences in their mesomorphic behavior. Compound
Ig gives nematic phase in a narrow temperature range
(Table 5). Symmetry distortion in molecule Ih leads
to bimesomorphism, some increase in the thermal
stability of the mesophase, and extension of its
temperature range (Table 5). The different behaviors
of the above mesogens are likely to originate from
specific features of their steric structure and steric
factors following therefrom. Simulation and optimiza-
tion of spatial models of molecules Ig and Ih suggest
twinning of molecules Ih (with asymmetric structure
and rotation of the benzene rings relative to the central
fragment) upon stacking. As a result, molecules Ih are
packed in columns with a shift, which should lead to
twisting of columns. This assumption was confirmed
by us while studying the texture of Ih, which ap-
peared as helical fragments.
phic properties of compounds Ig and Ih, distortion of
molecular symmetry leads to expansion of the meso-
phase temperature range.
EXPERIMENTAL
The electronic absorption spectra were measured
on a Specord UV-Vis spectrophotometer. The IR
1
spectra (400 4000 cm ) were recorded in KBr on an
1
Avatar-360 FT-IR ESP spectrometer. The H NMR
spectra were obtained from solutions in CDCl3 on a
Bruker Avance 250 spectrometer.
Mesomorphic properties were studied in the tem-
perature range from 25 to 300 C by differential
scanning calorimetry (DSC) using a Perkin Elmer
Diamond DSC instrument; in all experiments, the rate
1
of heating/cooling was 1 5 degmin . The textures
and phase bahavior were examined by polarized
microscopy using a Leitz Laborlux 12 Pol polarizing
microscope coupled with a Mettler FP 82 hot stage
1
Analysis of the above data led us to draw the
following conclusions:
(heating rate 2 degmin ). The texture images were
obtained using a Wild MPS 51 camera equipped with
24 36-mm2 microadapter.
(1) Enamine bridging groups stabilize columnar
ordering of discotic triazine derivatives via formation
of intermolecular hydrogen bonds. Increase in the
electron density on the central fragment in the series
of benzene (Ia Ie), biphenyl (IIIa IIIc), and tri-
phenylene derivatives (IVa IVd) stabilizes nematic
phase;
The simulation and optimization of geometric and
electronic models were performed by the MM+ and
PM3 in methods in the semiempirical approximation
in the HyperChem Pro 6.0.
1,3,5-Trihydroxyacetophenone (VI) was syn-
thesized according to the procedure described in [18].
(2) The mesophase temperature range for the
compounds under study, including that of nematic
phase, strongly depends on the size of the central
fragment: the larger the latter, the wider the tempera-
ture range and the higher the thermal stability of the
mesophase;
2,4,6-Tris{3-oxo-3-[2,4,6-tris(hydroxyphenyl)]-
prop-1-en-1-ylamino}-1,3,5-triazine (VIII). Phloro-
acetophenone, 0.84 g, was dissolved in 50 ml of an-
hydrous diethyl ether, and 0.42 g of ethyl formate and
0.96 g of finely dispersed metallic sodium were added
to the solution. The mixture was stirred for 20 25 h
at room temperature (it gradually turned turbid and
cream-colored). The solvent and excess ethyl formate
were distilled off under reduced pressure (water-jet
pump), the residue (compound VII) was dried and
dissolved in 30 ml of methanol, and the solution was
added to a mixture of 0.21 g of 1,3,5-triazine-2,4,6-
triamine in 25 ml of dimethylformamide. The result-
ing orange solution was acidified with acetic acid,
heated to 30 40 C over a period of 20 min, cooled to
room temperature, and kept for 1 2 days in a refri-
gerator. The cream-colored crystals of enaminoketone
VIII were filtered off in a refrigerator. Evaporation of
the filtrate gave an additional amount of a reddish
product VIII. Overall yield 0.5 g.
(3) Columnar ordering of molecules of benzene
derivatives Id and If is favored by replacement of the
OC(O) ester lether by C(O)O ;
(4) The effect of lateral substituents on phase
transitions in the examined series of discogens I, III,
and IV cannot be estimated unambiguously; it is
largely determined by the structure of the central
fragment and the positions of the lateral substituents;
(5) Introduction of a cyclohexane fragment into
peripheral substituents of a discogen molecule was
shown for the first time to favor formation of nematic
(ND) mesophase. The presence of two cyclic frag-
ments at the periphery of a discogen molecule,
provided that flexible hydrocarbon radicals are absent,
gives rise to bimesomorphism;
2,4,6-Tris{[3-oxo-3-[(2,4,6-tris(decanoyloxy)-
phenyl]prop-1-en-1-ylamino}-1,3,5-triazine (IIc).
Decanoyl chloride, 8.5 mmol, was added to a solution
(6) As follows from a comparison of the mesomor-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 1 2007

110
AKOPOVA et al.
of 0.5 g of compound VIII in 50 ml of anhydrous
pyridine. The mixture was stirred for 24 h at a tem-
perature not exceeding 55 C and poured into water
acidified with hydrochloric acid. The cream-colored
precipitate was filtered off and dried in air. Yield 35
40%. The product was purified by repeated column
chromatography on silica gel L (100 250 m) using
hexane as eluent. Yield of the purified product 25%.
Compound IIc is readily soluble in acetone, benzene,
diethyl ether, and hexane. UV spectrum (chloroform),
max, nm (log ): 320 (5.19), 265 (4.10). IR spectrum
6. Frolova, T.V., Akopova, O.B., and Usol’tseva, N.V.,
Izv. Vyssh. Ucheb. Zaved., Khim. Khim. Tekhnol.,
2005, vol. 48, no. 12, p. 57.
7. Destrade, C., Tinh, N.H., Gasparoux, H., Malthete, J.,
and Levelut, A.M., Mol. Cryst. Liq. Cryst., 1981,
vol. 71, p. 111.
8. Akopova, O.B., Materialy II Vserosssiiskoi nauchnoi
konferentsii Molekulyarnaya fizika neravnovesnykh
sistem (Proc. II All-Russian Conf. Molecular
Physics of Nonequilibrium Systems ), Ivanovo, 2000,
p. 189.
1
(KBr), , cm : 1711 (C=O, ester); 1606 (C=O,
ketone); 1263 ( C O); 1049 [C C(O) C]; 880 (
,
9. Arikainen, E.O., Boden, N., Bushby, R.J., Loz-
man, O.R., Vinter, J.G., and Wood, A., Angew. Chem.,
Int. Ed. Engl., 2000, vol. 39, no. 13, p. 2333.
CH
1
out-of-plane, 1,3,5-substitution); H NMR spectrum,
, ppm: 0.85 0.87 m (9H, CH3), 1.26 s [126H,
(CH2)7], 7.26 m (2H, Harom). Found, %: C 69.20; H
8.80. C120H186N6O21. Calculated, %: C 70.35; H 9.15.
10. Akopov, D.A. and Akopova, O.B., Zh. Strukt. Khim.,
2002, vol. 43, no. 6, p. 1139.
ACKNOWLEDGMENTS
11. Zemtsova, O.V., Akopova, O.B., and Usol’tseva, N.V.,
Zh. Strukt. Khim., 2002, vol. 43, no. 6, p. 1142.
This study was performed under financial support
by the program Development of the Mechanisms for
Integration of Educational and Research Processes in
the Field of Nanomaterials (project no. RNP 2.2.1.1.
7280).
12. Akopova, O.B., Frolova, T.V., and Usol’tseva, N.V.,
Materialy nauchnoi konferentsii Nauchno-issledo-
vatel’skaya deyatel’nost’ v klassicheskom universitete:
Teoriya, metodologiya, praktika (Proc. Scientific
Conf. Research Activity in a Classical University:
Theory, Methodology, and Practice ), Ivanovo:
Ivanov. Gos. Univ., 2003, p. 55.
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