Influence of the position of the nitro group on the structural and spectroscopic characteristics of N'-(nitrobenzylidene)sonicotinic hydrazides in the crystalline state

Article abstract of DOI:10.1023/A:1015065814759

N-Substituted isonicotinic hydrazides of the general formula Py-C(=O)-N(H)-N'=C(H)-R, where R is o- (1), m- (2), or p-nitrophenyl (3), were studied by IR spectroscopy and X-ray diffraction analysis. The position of the nitro group in these compounds has n

Full text of DOI:10.1023/A:1015065814759

Russian Chemical Bulletin, International Edition, Vol. 51, No. 1, pp. 99—104, January, 2002
99
Influence of the position of the nitro group on the structural and
spectroscopic characteristics of N´ꢀ(nitrobenzylidene)isonicotinic hydrazides
in the crystalline state
E. G. Atovmyan, L. A. Nikonova, O. S. Filipenko, T. N. Fedotova, and S. M. Aldoshin
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
1
8 Institutskii prosp., 142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (095) 515 3588. Eꢀmail: atovmyan@icp.ac.ru
N´ꢀSubstituted
isonicotinic
hydrazides
of
the
general
formula
Py—C(=O)—N(H)—N´=C(H)—R, where R is oꢀ (1), mꢀ (2), or pꢀnitrophenyl (3), were
studied by IR spectroscopy and Xꢀray diffraction analysis. The position of the nitro group in
these compounds has no effect on the type of the crystal structure. The crystal packings are
based on stacks consisting of antiparallel planar molecules. The molecules from the adjacent
stacks are linked to each other via the N—H...NPy hydrogen bonds. Depending on the position
of the nitro group, the N...NPy distance increases in the series 3 > 1 > 2 and the energy of the
hydrogen bonds decreases (according to the IR spectroscopic data) from 3.9 to 3.1 kcal mol–
1
.
Analysis of the IR spectra demonstrated that the intensity of absorption in the ν(C—H)
stretching region of the pyridine ring increases substantially as the the N—H...NPy hydrogen
bond is strengthened. Some regularities of the changes, which are observed for the ν(NO2)
bands in the spectra of the nitrophenylꢀcontaining conjugated molecules in solutions, persist in
the crystalline state.
Key words: N´ꢀ(nitrobenzylidene)isonicotinic hydrazides, molecular and crystal structure,
intermolecular hydrogen bonds, IR spectroscopic characteristics of hydrogen bonds and nitro
groups.
N´ꢀSubstituted isonicotinic hydrazides (INH) of the
general formula
molecular and crystalline properties of the compounds of
this series on the position of the nitro group in the subꢀ
stituent R. Isomer 2 differs from compounds 1 and 3
in that it crystallizes from aqueous alcohols as crysꢀ
tal hydrates. From this viewpoint, compound 2 reꢀ
sembles N´ꢀ(5ꢀnitrofurfurylidene)isonicotinic hydrazide
(
4), which can form not only anhydrous crystals possessꢀ
ing the intermolecular NH...NPy hydrogen bonds but also
crystal hydrates of different compositions with other types
of the intermolecular hydrogen bonds and a crystal solꢀ
3
,4
vate involving acetic acid and water.
The geometric parameters of the mꢀnitrobenzylidene
fragment in compound 2 are close to those of the nitrofuꢀ
ran fragment in 4. Actually, we obtained a set of crystalꢀ
line products for compound 2, as in the case of comꢀ
pound 4 studied by us earlier, viz., anhydrous crystals, the
crystal hydrates [2•H O] and [2•1.5H O], and the crystal
1
attract interest because of their photoactivity and bioꢀ
2
3
logical activity. Previously, we have investigated the efꢀ
fects of the nature and the structure of the substituent R
and the influence of the conditions of crystallization on
the composition and structure of single crystals and on
the character and geometry of the intermolecular hydroꢀ
gen bonds. In the present study, we examined oꢀ, mꢀ, and
pꢀnitrobenzylideneisonicotinic hydrazides (1, 2, and 3,
respectively) by IR spectroscopy and Xꢀray diffraction
analysis with the aim of revealing the dependence of the
2
2
solvate with acetic acid and water, viz., [2•H O•AcOH].*
2
In compound 3, the substituent R has a more substanꢀ
tial effect (compared to compounds 1 and 2) on the elecꢀ
tron density redistribution within the conjugated molꢀ
* The structural data for these compounds will be published in
Russian Chemical Bulletin, Int. Ed. in 2002.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 96—100, January, 2002.
066ꢀ5285/02/5101ꢀ99 $27.00 © 2002 Plenum Publishing Corporation
1

1
00
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Atovmyan et al.
Table 1. Crystallographic data for compounds 1—3
Table 2. Dihedral angles (α) between the planes of the pyridine
ring (I), the central fragment of the molecule (II), the phenyl
ring (III), and the nitro group (IV) in compounds 1—4
Parameter
1
2
3
Space group
a/Å
b/Å
P 2 /c
P 2 /c
P 2 /c
1
1
1
Compound
α/deg
7.510(2)
10.910(2)
15.476(3)
94.87(2)
1263.4(5)
1.421(2)
4
8.446(2)
10.800(1)
14.181(2)
106.38(2)
1241.0(5)
1.446(2)
4
7.970(2)
10.672(2)
14.905(2)
100.6(3)
1246.2(5)
1.440(2)
4
I—II
II—III
III—IV
c/Å
β/deg
1
2
3
4
16.9
8.0
8.0
8.7
0.3
0.3
—
38.9
12.5
12.3
7.2
3
V/Å
dcalc/g cm–3
12.9
Z
I > 4σ(I)
1598
1562
1194
R
wR
0.041
0.122
0.036
0.099
0.037
0.097
Table
3.
Bond
lengths
(d)
in
the
central
Py—C(=O)—N(H)—N=C(H)—R—NO fragments of N´ꢀsubꢀ
2
Note. The molecular formula of compounds 1—3 is C H N O ,
stituted isonicotinic hydrazides 1—4
13
10
4
3
М = 210.25.
w
Comꢀ
pound
d*/Å
ecule resulting in specific physicochemical properties of 3
and high reactivities of its other active centers.5
Py—C C—N N—N N=C C—R R—N C=O
In the presents study, we examine the data from Xꢀray
diffraction analysis and IR spectroscopy for anhydrous
crystals of the isomeric series of N´ꢀ(nitrobenzylidene)isoꢀ
nicotinic hydrazides 1—3 and N´ꢀ(5ꢀnitrofurfurylideꢀ
1
2
3
4
1.505 1.356 1.375 1.270 1.469 1.462 1.217
1.504 1.358 1.377 1.270 1.463 1.464 1.214
1.501 1.359 1.381 1.269 1.466 1.474 1.214
1.500 1.357 1.375 1.274 1.439 1.422 1.221
4
ne)isonicotinic hydrazide 4. Although the lastꢀmentioned
*
The accuracy of the determination of the bond lengths is
compound does not belong to the isomeric series, it (as
mentioned above) is similar to compound 2 in a number
of properties.
0.002 Å.
isotropically. The crystallographic data for compounds 1—3 are
given in Tables 1—3.
Experimental
Results and Discussion
The IR spectra were recorded on a Specord Mꢀ82 spectroꢀ
meter in KBr pellets and the spectroscopic data were processed
on a computer. To determine the stretching vibration frequenꢀ
cies of the C=O group, which are not perturbed by intermolecuꢀ
lar interactions in the crystal, we prepared dilute solutions in
THF, which was distilled over CaH2 immediately before use
The overall view of molecule 2 is shown in Fig. 1.
Molecules 1, 3, and 4 have analogous structures. The
central C(2)—C(1)—N(1)—N(2)—C(7)—C(8) fragment
of molecules 1—3 is virtually planar (the torsion angles in
these fragments are at most 5°). Molecules 2 and 3 adopt
virtually identical conformations as evidenced by the diꢀ
hedral angles between the planes of the pyridine ring (I),
the central fragment (II), the phenyl ring (III), and the
nitro group (IV), and these molecules are more planar
than molecule 1 (see Table 2). Molecule 4 is also virtually
planar. However, the conformations of molecules 1, 2,
and 4 differ substantially. In molecule 4 containing the
nitrofuran fragment as the substituent R, the electronegaꢀ
tive O(1) and N(2) atoms, the O atom of the furan ring,
and one of the O atoms of the nitro group are in the syn
orientations. To the contrary, the O(1) and N(2) atoms
and the O atoms of the nitro group in molecules 1 and 2
are in the synꢀanti positions (see Fig. 1).
(
samples are insoluble in CCl ).
4
Compound 1, the hydrate of 2 (which has been described as
6
anhydrous 2 in a number of papers cited in the study ), and
compound 3 were prepared by the reactions of isonicotinic
hydrazide with oꢀ, mꢀ, and pꢀnitrobenzaldehydes, respectively,
in aqueous ethanol (all reagents were purchased from Aldrich).
Hydrazides 1 (m.p. 235—236 °C) and 3 (m.p. 290—291 °C)
were crystallized from aqueous ethanol. Anhydrous 2 (m.p.
2
31—232 °C) was obtained when either the reaction or crystalliꢀ
zation were carried out in anhydrous MeOH, which has been
preliminarily distilled over magnesium metal.
The Xꢀray diffraction data sets for crystals of 1—3 were colꢀ
lected on a fourꢀcircle КМꢀ4 Kuma Diffraction diffractometer
(
MoꢀKα radiation, ω/2θ scanning technique, 3.05° < θ < 40.05°).
We repeated the Xꢀray study of the crystal structure of 1 because
the previous Xꢀray data have been obtained7 from crystals of
poor quality. Absorption was ignored. The structures were solved
by direct methods using the SHELXꢀ86 program package8
The corresponding bond lengths in molecules 1—4
are identical to within the experimental error (see Table 3),
except for the C—R and R—N bond lengths in compound
4. This is, apparently, associated with the difference in
the electronic structure of the furan and benzene rings.
and refined by the fullꢀmatrix leastꢀsquares method using the
9
SHELXLꢀ93 program package. The positions of all H atoms
were revealed from difference Fourier syntheses and refined

N´ꢀ(nitrobenzylidene)isonicotinic hydrazides
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
101
O(3)
N(4)
C(11)
O(2)
C(10)
C(9)
C(12)
C(13)
C(8)
C(7)
N(2)
N(1)
O(1)
C(1)
C(2)
C(3)
C(4)
C(6)
C(5)
N(3)
Fig. 1. Overall view of the molecule and the system of intermolecular NH...NPy hydrogen bonds in isonicotinic hydrazide 2.
In the crystals of 1—3, the planar molecules are packed
in stacks. This type of packing is very often observed in
the crystals of N´ꢀsubstituted benzoꢀ and isonicotinic
hydrazides3 as well as in the crystals of many other
organic compounds. In these stacks, the molecules are
oriented antiparallel with respect to each other and are
related by inversion centers along the short crystalloꢀ
graphic axis (Fig. 2). This packing mode is, undoubtedly,
determined by the high energy of interactions between
the planar molecules packed in stacks (this suggestion is
confirmed by the high melting points of the compounds
under study).
molecule contains the paraꢀnitro group and, correspondꢀ
ingly, is the longest one. In the crystal of 1, the N...NPy
distance is shorter than that in the crystal of 2 because the
nitro group is twisted out of the plane of the molecule by a
larger angle.
In the crystal structures of 1—3, there are also other
rather short intermolecular contacts, for example, the conꢀ
tact between the O atom of the C=O group and the αꢀH
atom of the Py ring (see Fig. 2). The αꢀCPy(H)...O=C
distances are 3.42, 3.12, and 3.20 Å in the crystals of
1—3, respectively. However, it should be noted that the
,10
In the crystals, the molecules from the adjacent stacks
are linked to each other through the intermolecular
N—H…...NPy hydrogen bonds (Table 4) typical of N´ꢀsubꢀ
stituted isonicotinic hydrazides. The fragment of the moꢀ
lecular packing in the crystal of 2 is shown in Fig. 1
Table 4. Geometric, spectral, and energy (ЕHB) characteristics
of the intermolecular hydrogen bonds in compounds 1—4
Parameter
1
2
3
4
(
molecules 1, 3, and 4 are packed analogously). The longꢀ
d/Å
est N...NPy distance is observed in the structure of 2.
Apparently, steric hindrances to the formation of closely
spaced stacks are larger in the case of the metaꢀnitro group
compared to the orthoꢀ or paraꢀnitro groups. Actually, in
the structure of 2, the short O(2)...N(4) contact (3.09 Å)
between the nitro groups, which are related by the inverꢀ
sion center with the coordinates (½ ½ 0) and which
belong to the molecules from the adjacent translationally
equivalent (along the b axis) stacks, does not allow the
molecules to come closer together. The shortest N...NPy
distance is observed in the structure of compound 3 whose
N...N
H...N
C=O...αꢀCPy
ω/deg
N—H...N
3.10
2.25
3.42
3.28
2.42
3.12
3.03
2.12
3.20
3.00
2.24
—
165
3196
1680
1561
3.8
161
3243
1693
1548
3.1
166
3191
1686
1564
3.9
169
3180*
—
—
4.0
–
1
ν(N—H)/cm
–
1
ν(C=O)/cm
δ(N—H)/cm–
1
ЕHB/kcal mol–
1
* The ν(NH) frequency (3120 cm–1) reported in the study is a
misprint.
4

1
02
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Atovmyan et al.
z
N(4d)
O(2a)
x
y
0
Fig. 2. Stacked packing in the crystal of 2.
C—H—O angles are too small (130—140°) and the H...O
distances are too long (2.87, 2.34, and 2.47 Å, respecꢀ
tively) to consider these contacts as intermolecular hydroꢀ
gen bonds. Actually, as can be seen from Table 4, the
ν(C=O) frequency decreases as the O...CPy distance inꢀ
creases, whereas the inverse dependence would be obꢀ
served for intermolecular hydrogen bonds. This inconsisꢀ
tency cannot be attributed to the difference in the posiꢀ
tion of the nitro group in the phenyl fragment because the
ν(C=O) frequencies in dilute solutions of 1, 2, and 4 in
THF are approximately equal (1703—1706 cm ). We
failed to obtain the corresponding data for compound 3
because it is insoluble in appropriate solvents. The differꢀ
ences in ν(C=O) for compounds 1—3 are attributed both
to intramolecular interactions and intermolecular interꢀ
action in the crystal to the intermolecular C—H...O=C
hydrogen bond. It should be noted that in the structure of
N´ꢀ(furfurylidene)isonicotinic hydrazide 5 studied by us
previously,11 the intermolecular C—H...O=C hydrogen
bond (H is the αꢀhydrogen atom of the furan ring) was
revealed by IR spectroscopy, the C...O distance in 5
idene)isonicotinic hydrazide is directed toward one of the
lone electron pairs of the O atom (the C=O...H angle
is 124°). Probably, it is the aboveꢀmentioned factors that
are responsible for the fact that this contact belongs to
intermolecular hydrogen bonds.
The aboveꢀconsidered example demonstrates once
again that the presence (or absence) of intermolecular
hydrogen bonds in the crystals cannot be judged from the
geometric parameters of the X—H...Y contact. This conꢀ
clusion is also supported by the relationship between the
ν(N—H) frequencies and the N...NPy distances.
–
1
The ν(N—H) stretching vibration frequencies, the
δ(N—H) bending frequencies, and the energies of the
intermolecular hydrogen bonds (ЕHB) for compounds 1—4
are given in Table 4. The energies Е
were calculated
HB
1
2
according to empirical equations, which relate the freꢀ
quency of the ν(N—H) vibration perturbed by the interꢀ
molecular hydrogen bond to the frequency of the nonꢀ
perturbed ν (N—H) vibration frequency. For one of the
0
structurally similar compounds, the ν (N—H) frequency
0
–
1
is 3371 cm (according to the data of the present
study). It can be seen in Table 4 that there are the
inverse linear dependences between the N...NPy disꢀ
tances and the energies ЕHB as well as between ν(N—H)
and δ(N—H).
(
3.31 Å) being larger than those in compounds 2 and 3.
Note that the C—H...O angle (158°) in 5 is larger than the
corresponding angles in compounds 2 and 3 (135 and 130°,
respectively). In addition, the H atom in N´ꢀ(furfurylꢀ

N´ꢀ(nitrobenzylidene)isonicotinic hydrazides
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
103
Taking into account the structural characteristics of
provide a unique possibility of analyzing the specꢀ
tral characteristics of the nitro groups in aroꢀ
matic compounds containing a system of conjugated
bonds. In these compounds, the nitro groups are active
πꢀacceptors causing electron density redistribution beꢀ
tween the molecular fragments. As a result, the frequenꢀ
cies (ν) and intensities (А) of the bands of symmetric
and antisymmetric stretching vibrations of the nitro
group are changed compared to nonsubstituted nitrobenꢀ
zene (NB).
the intermolecular hydrogen bonds,1
3,14
the N—H...NPy
contact in the structure of 2 cannot be assigned to the
hydrogen bonds, i.e., the attractive intermolecular interꢀ
actions between NH and NPy must be absent. However,
as can be seen in Table 4, the dependences of ν(N—H)
and ЕHB for compound 2 on the N...NPy distances are
analogous to those observed for compounds 1, 3, and 4. It
–
1
should be noted that the value of ЕHB (3.1 kcal mol
)
indicates that even at such a long (from the structural
standpoint) distance, the force field created by the NPy
atom has a substantial effect on vibrations of the N—H
The effects of substituents in the NB molecules on the
spectral characteristics of the vibration bands of the nitro
group have been studied in detail only for paraꢀsubstituted
–
1
group (ν(N—H) is more than 100 cm lower than
5
ν (N—H); see Table 4).
NB due, apparently, to the fact that the paraꢀsubstituꢀ
0
Previously,1 we noted that the existence of the of the
intermolecular N—H...NPy hydrogen bond can be, in
particular, judged from a substantially higher absorpꢀ
tion in the region of ν(C—H) vibrations of the Py ring
1
ents exert a more unambiguous effect on ν and А comꢀ
pared to the substituents in other positions. It should be
noted that the spectral studies of the mutual influence of
the groups in molecules with conjugated bonds were carꢀ
ried out in solutions and, hence, these results cannot be
correctly compared with our data on the vibration freꢀ
quencies of the nitro groups in the crystalline state. Howꢀ
–
1
(
3100—2700 cm ) compared to absorption in the spectra
of N´ꢀsubstituted isonicotinic hydrazides in which the
NPy atom is not involved in specific interactions. The
results of the present study demonstrate that the intensiꢀ
ties of the bands in this frequency region increase as the
intermolecular hydrogen bond is strengthened (Fig. 3;
Table 4). We can only state this interesting experimental
fact for which no unambiguous explanation presently
exists.
5
ever, based on the results of the study and other investiꢀ
gations of the authors cited therein, we can point out a
series of regularities analogous to those observed in
solutions.
The intensities of all symmetric vibrations А in the
s
spectra of paraꢀsubstituted NB are higher than the intenꢀ
The data from Xꢀray diffraction analysis and IR specꢀ
troscopy for N´ꢀ(nitrobenzylidene)isonicotinic hydrazides
sities of antisymmetric vibrations А , as distinguished from
as
nitrobenzene. For all compounds studied by us (1—3,
where 3 can be considered as paraꢀsubstituted NB), this
intensity ratio persists.
A
The presence of potential πꢀdonor substituents in the
para position of the NB molecule leads to a decrease in
both the νas and ν frequencies (analogous situation is also
s
3
observed in the case of compound 3). Interestingly, the
νas and ν frequencies in the spectrum of 3 are virtually
s
identical with the corresponding values found in the specꢀ
trum of pꢀnitroaniline in CCl . Compared to NB, the ν
frequencies in the spectra of 1 and 2 are lower, whereas
4
as
1
2
the ν frequencies have higher values (Table 5).
s
In solutions of paraꢀsubstituted NB, the ν and νs
as
15
bands (primarily, ν ) are split. In the spectra of the
s
crystalline samples of the compounds under study, splitꢀ
ting of the ν band was observed only for compound 1.
s
Apparently, this splitting results from the same factors as
in solutions (rather than is associated with the crystalline
state) because this effect was not observed for comꢀ
pounds 2 and 3.
ν/cm–1
The aboveꢀconsidered data suggest that some spectral
3
500
3100
2700
characteristics of the NO groups are determined only by
2
Fig. 3. IR spectra of compounds 1—3 in the region of the
ν(N—H) and ν(C—H) vibrations of the Py ring. The curves are
numbered according to the identifying numbers of the comꢀ
pounds. The lowest curve represents the spectrum of N´ꢀ(furꢀ
furylidene)isonicotinic hydrazide possessing the intermolecular
NH...…O=C hydrogen bond.
intramolecular electronic effects and are independent of
the aggregation state of the compound and interactions
with the environment, be it is formed by the solvent molꢀ
ecules in solutions or the adjacent molecules of the comꢀ
pound in the crystal.

1
04
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Atovmyan et al.
Table 5. Frequencies of the symmetric stretching (ν ) and antiꢀ
References
s
symmetric stretching (ν ) vibrations of the nitro group in the
as
crystalline samples of 1—4 and in solution of nirobenzene (NB)
and pꢀnitroaniline (NA) in CCl4
1. E. Hadjoudis, in Photochromism, Molecules and Systems,
Eds. H. Durr and M. BouasꢀLaurent, Elsevier, Amsterdam,
1
990, 708.
2
3
. Yu. P. Kitaev and B. I. Buzykin, in Gidrazony [Hydrazones],
Nauka, Moscow, 1974, 381 pp. (in Russian).
. Y. G. Atovmyan, L. A. Nikonova, I. I. Chuev, A. N.
Utenyshev, M. Z. Aldoshina, and S. M. Aldoshin, J. Mol.
Struct., 1999, 474, 167.
Compound
νs
νas
cm–1
1
2
3
4
NB
NA
1366, 1352
1355
1519
1526
1511
1521
1532
1511
4
5
6
7
8
9
. S. M. Aldoshin, L. A. Nikonova, E. G. Atovmyan, A. N.
Utenyshev, and D. B. Frolov, Izv. Akad. Nauk, Ser. Khim.,
1336
1349
1349
1338
1
996, 2263 [Russ. Chem. Bull., 1996, 45, 2148 (Engl. Transl.)].
. P. P. Shorygin, N. B. Lopatina, B. V. Lopatin, and T. E.
Gorodilova, Izv. Akad. Nauk, Ser. Khim., 1998, 304 [Russ.
Chem. Bull., 1998, 47, 297 (Engl. Transl.)].
. Beilsteins Hundbuch der organischen Chemie, E III/IV,
Springer, Berlin—Heidelberg—New York—London—Paris—
Tokyo, 1979, 22, No. 1, 571.
Hence, the crystals of isonicotinic hydrazides under
consideration are characterized by the stacked packing
formed by antiparallel elongated planar molecules regardꢀ
less of the position of the nitro group. This packing is
typical of many N´ꢀsubstituted benzoꢀ and isonicotinic
hydrazides. The molecules located in the adjacent stacks
are linked to each other through the N—H...NPy hydroꢀ
gen bonds, the N...NPy distance being determined by the
position of the nitro group and increasing in the series of
the paraꢀ, orthoꢀ, and metaꢀsubstituted derivatives. The
intermolecular N—H...NPy hydrogen bonds are characꢀ
terized by the N...NPy distances, which are larger than the
crystallographic criteria for intermolecular N...N hydroꢀ
gen bonds. As the intermolecular N—H...NPy hydrogen
bond is strengthened, the intensity of IR absorption in the
region of ν(C—H) vibrations of the Py ring increases subꢀ
stantially compared to the spectra of isonicotinic hyꢀ
drazides in which the NPy atom is not involved in interꢀ
molecular hydrogen bonding. Some regularities of the
. I. I. Chuev, S. M. Aldoshin, E. G. Atovmyan, D. B. Frolov,
and A. N. Utenyshev, Izv. Akad. Nauk, Ser. Khim., 1996,
8
96 [Russ. Chem. Bull., 1996, 45, 851 (Engl. Transl.)].
. G. M. Sheldrik, SHELXꢀ86, Program for the Crystal Strucꢀ
ture Determination, University of Cambridge (England),
Cambridge, 1986.
. G. M. Sheldrik, SHELXLꢀ93, Program for the Refineꢀ
ment of Structure, Universität Göttingen (Germany),
Göttingen, 1993.
1
1
0. T. G. Atovmyan, S. M. Aldoshin, and L. O. Atovmyan, Mol.
Cryst. Liq. Cryst., 1990, 178, 231.
1. E. G. Atovmyan, I. I. Chuev, L. A. Nikonova, A. N.
Utenyshev, and S. M. Aldoshin, Izv. Akad. Nauk, Ser. Khim.,
1998, 1369 [Russ. Chem. Bull., 1998, 47, 1331 (Engl. Transl.)].
12. V. S. Korobkov, Zh. Prikl. Spektrosk., 1973, 19, 1125 [J. Appl.
Spectrosc., 1973, 19 (Engl. Tranl.)].
3. L. N. Kuleshova and P. M. Zorkii, Acta Crystallogr., Sect. B,
981, 37, 1363.
1
1
1
1
4. Yu. V. Zefirov, Kristallografiya, 1997, 42, 936 [Crystallogr.
Repts., 1997, 42 (Engl. Transl.)].
5. P. P. Shorygin and B. V. Lopatin, Zh. Fiz. Khim., 1965, 34,
changes in the ν(NO ) frequencies in the IR spectra of
2
compounds with conjugates systems and the nitrophenyl
fragments, which were observed in solutions, persist in
the crystalline samples.
2
868 [J. Phys. Chem. USSR, 1965, 34 (Engl. Transl.)].
Received March 28, 2001