1,7-dithioxo-substituted systems. Synthesis, structure, and photoconductivity of bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) sulfide

Article abstract of DOI:10.1134/S1070363210020179

Bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) sulfide was synthesized by the reaction of bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide or its oxygen analog with hydrazine. Conformational lability of the molecule of dihydrazone was studied by the DFT(B3

Full text of DOI:10.1134/S1070363210020179

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 2, pp. 284–291. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © L.V. Timokhina, V.I. Smirnov, S.G. Shevchenko, A.V. Vashchenko, I.A. Ushakov, 2010, published in Zhurnal Obshchei Khimii,
2010, Vol. 80, No. 2, pp. 259–266.
1,7-Dithioxo-Substituted Systems.
Synthesis, Structure, and Photoconductivity
of Bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) Sulfide
L. V. Timokhina, V. I. Smirnov, S. G. Shevchenko, A. V. Vashchenko, and I. A. Ushakov
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
email: tim@irioch.irk.ru
Received May 18, 2009
Abstract―Bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl) sulfide was synthesized by the reaction of bis(5,5-
dimethyl-3-thioxocyclohex-1-enyl) sulfide or its oxygen analog with hydrazine. Conformational lability of the
molecule of dihydrazone was studied by the DFT(B3LYP) method using expanded basis sets 6-311G and 6-
311G(d,p). Analysis of vibration IR and Raman spectra of the most stable conformers of the isolated molecule
of dihydrazone was performed at the harmonic approximation. Using the Onsager SCRF solvation model the
absence of solvent effect on the relative stability of the conformers was shown. The photoconductivity of
dihydrazone was studied. Low value of the ratio of photocurrent to dark current (Jp/Jd = 2.5–3.5) for
dyhydrazone was assigned to the lability of its stereoelectronic structure, which was in line with the data of 1H,
13С, and 15N NMR spectra.
DOI: 10.1134/S1070363210020179
We have shown that compounds with the S=C–
C=C–S–C=C–C=S structural fragment are promising
in a search for solar energy converters [1]. In
continuation of systematic studies in this direction in
the series of functionally substituted α,β-unsaturated
sulfides [2–5], in the present work the reaction of bis-
(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide (I) and
its oxygen analog, bis(5,5-dimethyl-3-oxocyclohex-1-
enyl) sulfide (II) with hydrazine was studied and its
stereoelectronic structure was investigated, in
particular, in connection with the photoelectric
properties of the obtained bis(5,5-dimethyl-3-hydra-
zonocyclohex-1-enyl) sulfide (III).
reaction was more sluggish and should be carried out
at room temperature.
Me
Me
Me
Me
X
S
X
I, II
Me
Me
Me
Me
NH2NH2
5'
2'
5
2
6'
1'
4
3
4'
3'
6
1
H2NN
S
NNH2
III
Reaction of dithioxosulfide (I) with hydrazine (the
ratio of the reagents 1:2) in ethanol at –10 to –5°C is
accompanied by active evolution of hydrogen sulfide
and results in the formation of the earlier unknown bis
X = S (I), O (II).
Dihydrazone III, unlike compounds I and II, is
practically insoluble in conventional organic solvents.
For analytical purposes, its low concentration solutions
in DMSO and DMSO-d6 were used.
(5,5-dimethyl-3-hydrazonocyclohex-1-enyl)
sulfide
(III) in 46% yield. Use of a 4-fold excess of hydrazine
and increase of the reaction temperature to 0–5°C
allowed to increase the yield of hydrazone III to
~80%. The same dihydrazone was obtained from
dioxosulfide II and hydrazine, although in this case the
Molecule III contains important functional frag-
ments of two types: divinyl sulfide group as the central
284

1,7-DITHIOXO-SUBSTITUTED SYSTEMS
unit and two hydrazone substituents, which can
285
H
H
H
substantially change the conformational structure of
compounds I and II. To analyze the peculiarities of
stereoelectronic structure of dihydrazone III, we
performed its conformational analysis using modern
methods of quantum chemistry, experimental methods
of IR and Raman spectroscopy, and the two-
dimensional NMR spectroscopy.
C
H
H
H
H
H
C
H
H
H
C
H
H
C
H
C
H
H
H
C
C
H
C
H
H
C
H
H
C
H
C
H
C
C
C
C
C
H
The 1H NMR spectrum of compound III in DMSO-
d6 contains narrow singlets of the NH2 group protons
(6.3 ppm), olefin protons (6.1 ppm), the protons of the
ring CH2 groups (2.11–2.13 ppm), and CH3 groups
(0.95 ppm). The absence of multiplet signals of the
CН2 and CН3 group protons is indicative of fast
reorientation of the molecule fragments leading to
averaging of the signals. The values of chemical shifts
in the 15N NMR spectrum of the C=N–NH2 fragment
of compound III were obtained from the data of two-
dimensional 1Н–15N HMBC spectroscopy and are
typical for the given structure (–47.5 ppm C=N).
H
S
H
H
H
H
IIIа
H
H
H
H
H
C
C
H
H
H
H
C
H
H
H
H
Conformational nonuniformity of the molecule of
dihydrazone III and the model system, bis(3-
hydrazonocyclohex-1-enyl) sulfide (IV) having no
methyl substituents in the six-membered rings, was
studied by the DFT(B3LYP) method.
C
H
C
H
H
H
C
C
C
H
C
C
C
H
H H
C
C
C
C
H
H
H
C
H H
S
H
H
As for the earlier studied molecule of dithio-
xosulfide I [3], calculation of molecules III and its
model IV in the gas phase predicts the preferable
existence of nonplanar cis-trans-conformer (IIIc)
(Fig. 1). The following order of relative stability of the
conformers of dihydrazone III was found: Е(IIIс) <
Е(IIIb) < Е(IIIа). Moreover, in compound III two
types of conformers are realized: less stable IIIa and
the most stable (IIIс) with the exocyclic C1'=C2' bond
and the C3'=N–NH2 group arranged above and below
the C1'SC1 plane, respectively. Unlike compound I,
these conformers are not mirror images. The difference
in their total energies is 4.53 kJ mol–1 and their dipole
moments have different values and are oppositely
directed (Fig. 1, Table 1).
H
IIIb
H
H
H
C
H
C H
H
H
H
H
H
H
H
C
H
H
H
C
H
C
C
H
H
H
H
H
C
C
C
C
C
C
H
C
C
C
H
H
S
H
H
H
The energy difference between the conformers IIIа
and IIIb is substantially less, 0.66 kJ mol–1. The
obtained order of stability is retained for the model
molecule IV that suggests negligible contribution of
the methyl substituents into the energy of stabilization
of the conformers. Variation of polarity of the medium
to ε = 36 does not change the order of stability of the
conformers.
C
H
H
H
IIIc
Fig. 1. Most stable conformers of dihydrazone III
according to DFT(B3LYP)/6-311G(d,p) calculations.
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286
TIMOKHINA et al.
Table 1. DFT(B3LYP)/6-311G(d,p) calculated total energies, energies of stabilization, dipole moments, dihedral and bond
angles of stable conformers of dihydrazone III
Comp. no.
–Еtot, au
Estab, kJ mol–1
∠C2'=C1'SC1, deg
∠C1'SC1=C2, deg
∠CSCа, deg
μ, D
–1242.72786
–1242.72813
–1242.72960
0
122.5
132.1
–19.3
132.0
25.8
105.3
104.2
105.0
3.2
5.5
3.6
IIIа
IIIb
IIIc
–0.69
–4.55
–126.2
a
C–S bond lengths in all conformers are close and equal to 1.785, 1.788, and 1.784 Ǻ for conformers IIIа, IIIb, and IIIс, respectively.
The obtained theoretical results are in line with the
and Raman spectra in the solid phase and in the
DMSO-d6 solution. Method B3LYP/6-311G in
approximation of the Onsager model revealed weak
effect of the polar properties of the medium (ε = 1–36)
on the vibration spectra of the conformers of the model
compound IV (Δν = 5 cm–1). Besides, in the IR spectra
of dihydrazone III the experimental stretching
vibrations of the NH2 groups in the range of 3400–
3000 cm–1 in the solid state and in the DMSO-d6
solution coincide. This allowed us to use the data of
theoretical calculations in the gas phase for analysis of
vibration spectra of dihydrazone III in the solid state.
Taking into account that calculations by the density
matrix functional method lead to systematic over-
estimation of frequencies, the quality of calculations
was estimated taking into account scaling factors (SF).
In Table 2 the approximate forms, frequencies, and
relative intensities of the conformationally sensitive
vibrations and their scaling factors are given. The
obtained values of SF characterize satisfactory the
accuracy of calculation of the vibration spectra of
compound III by the B3LYP/6-311G(d,p) method.
This is clearly seen from the comparison of the
theoretical and experimental vibration spectra (Figs. 2, 3).
data of the two-dimensional NMR spectroscopy for
solutions of dihydrazone III in DMSO-d6. 2D NOESY
experiment allowed to establish the configuration of
the C=N–NH2 fragment from the presence of a cross
peak between the signals of the NH2 group protons and
protons of 4(4')CН2 groups. Besides in the 2D NOESY
spectrum cross peaks are observed between the signals
of the olefin proton Н2(2') and protons of the 6(6')CН2
and CН3 groups in the 5(5') position (see scheme). The
observed correlations are possible only for conformers
IIIa and IIIc, which interconvert in the solution due to
the rotation about the S–C bond.
NH2
Me
Me
N
H
H
H
5'
2'
6'
1'
3
4'
3'
2
4
H2N
1
Me
Me
5
6
S
N
Experimental study of the IR and Raman spectra of
dihydrazone III in the solid state by the method of
frustrated total internal reflection using the zinc
selenide crystal in conjunction with quantum chemical
analysis of vibration spectra allowed to reveal specific
features of conformational equilibrium in the solid
phase.
According to the B3LYP/6-311G(d,p) calculations,
three types of normal modes are characteristic by the
form, namely, asymmetric and symmetric stretching
vibrations of the NH2 groups at 3650–3450 cm–1 and
wagging vibrations ρω of the NH2 groups at 740–
670 cm–1 (Table 2). They can be used for analytical
appraisal of the conformational equilibrium since these
very frequencies showed high sensitivity to
conformational transformations. Two bands with
different ratio of intensities are observed for
conformers IIIa and IIIc (I682 < I702 in the IR spectrum
of the less stable conformer IIIa and I687 > I726 in the
IR spectrum of the most stable conformer IIIc), and
one for conformer IIIb with equivalent N–NH2 groups
(Figs. 2, 3). A high-frequency band ρω(NH2) is due to
wagging vibrations of the NH2 group in the plane of
atoms of the central fragment, a low-frequency band is
IR (Fig. 2) and Raman (Fig. 3) spectra of the most
stable conformers IIIa, IIIb and IIIc of the molecule
of dihydrazone III in the isolated state have been
analyzed by the B3LYP/6-311G(d,p) harmonic
vibration calculations. The conformers have Cs
symmetry and each shows 135 normal modes of the A
type symmetry in the theoretical spectra, which are
active in the IR and Raman region.
The assignment of frequencies in the experimental
vibration spectra was made on the basis of analysis of
localization of theoretical vibrations, behavior of
frequencies and intensities of vibrations in different
media (gas phase, solvent with ε = 36 for model
compound IV) and comparison of the experimental IR
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1,7-DITHIOXO-SUBSTITUTED SYSTEMS
(a)
287
(b)
(c)
(d)
Fig. 2. Experimental IR-ATR spectrum of dihydrazone III in the solid state and B3LYP/6-311G(d,p) calculated IR spectra of
conformers IIIа, IIIb, and IIIс in the gas phase.
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288
TIMOKHINA et al.
(a)
0.10
0.08
0.06
0.04
0.02
3500
3000
2500 2000
1500
(b)
1000
500
0 ν, cm–1
1000
500
0
500
1000
2000
2500
3000
3500 ν, cm–1
(c)
2000
1000
0
500
1000
2000
2500
3000 3500 ν, cm–1
(d)
1000
500
0
500
1000
2000
2500
3000
3500 ν, cm–1
Fig. 3. Experimental Raman spectrum of dihydrazone III in the solid state and B3LYP/6-311G(d,p) calculated Raman spectra of
conformers IIIа, IIIb, and IIIс in the gas phase.
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1,7-DITHIOXO-SUBSTITUTED SYSTEMS
289
due to vibrations of the out-of-plane NH2 group. In the
experimental IR-ATR spectrum of dihydrazone III in
the solid phase the most intensive are two bands at 640
In the experimental Raman spectrum of dihyd-
razone III two very intense bands are observed. The
most intense one is caused by stretching vibrations of
the central fragment C=C–S–C=C with the syn-phase
stretching of the double bonds, the less intense, by the
stretching vibrations of atoms in the chain –N=C–
C=C–S–C=C–C=N–. High intensity of the bands of
these vibrations in the Raman spectrum proves the
presence of a conjugated electronic system in the said
fragments.
and 707 cm–1 with the ratio of intensities I640 > I707
,
that allows to conclude on the stabilization of
conformer IIIc in the solid phase. This is confirmed by
the results of theoretical and experimental Raman
spectra of compound III (Fig. 3, Table 2).
Analysis of the vibration spectra of dihydrazone
III must take into account not only the possibility of
existence of different conformers but also various
associates with participation of the N–NH2 groups.
From this point of view it is interesting to note the
absence of the stretching vibration bands of the NH2
group in the Raman spectra, the presence of two
additional broadened stretching vibration bands of the
NH2 group in the experimental IR spectrum in the
range 3400–3200 cm–1, and a strong broadening of the
high-frequency band ρω(NH2) at 707 cm–1. All
together, these facts are indicative of the presence of
NH-associates with participation of the out-of-plane
NH2 groups of conformer IIIa in the solid phase.
In this connection we expected that dihydrazone III
should show high photoconductivity. It was found that
in all spectral range the photocurrent is characterized
by dependence on the applied voltage. For the samples
with electrodes made of Аl, Аg, and Au, the photo-
current is observed only when positive potential is
applied to the lit electrode. This suggests that the main
charge carriers in the studied sample of dihydrazone
III are holes. Photoeffect is observed in the spectral
region of the proper absorption (210–470 nm) of
compound III. However, the efficiency of the
photoeffect is low, the ratio of photocurrent (Jp) to the
Table 2. Calculatedа and experimental characteristics of the conformationally sensitive bands in the IR and Raman spectra of
dihydrazone III
Calculatedа, ν, cm–1 (I, Km mol–1)
Experiment,
ν, cm–1
Assignment
SF
IIIа
IIIb
IIIc
IR spectra
ρωNH2
682 (472)
690 (1087)
687 (503)
640 v.s
707 v.s
3195 sh
3221 m
3285 sh
3288 w
3361 m
0.94
0.93
ρω[NH2]'
νsNH2
702 (534)
3448 (4)
3471 (2)
726 (487)
3462 (1)
3471 (2)
3473 (2)
3482 (3)
νs[NH2]'
νasNH2
3611 (20)
3621 (32)
3616 (32)
3617 (27)
3609 (20)
3620 (32)
νas[NH2]'
Raman spectra
ν[N–N=C–C=C]2–S
ν–C=C–S–C=C
1642 (428)
1647 (1203)
syn-phase
1642 (828)
1653 (2315)
syn-phase
1641(218)
1647 (1507)
syn-phase
1575 s
0.96
0.97
1598 v.s
1653 (401)
anti-phase
3447 (342)
3471 (449)
3611 (176)
3621 (235)
1654 (418)
anti-phase
3461 (365)
3470 (455)
3609 (155)
3620 (234)
νsNH2
3473 (437)
3482 (452)
3616 (195)
3617 (255)
–
νs[NH2]'
νasNH2
νas[NH2]'
–
–
–
a DFT(B3LYP)/6-311G(d,p) method.
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TIMOKHINA et al.
dark current (Jd) is Jp/Jd = 2.5–3.5. One of the reasons
of low efficiency of photoeffect in the present case
may be a possibility of dissipation of the absorbed
energy connected with the lability of stereoelectronic
structure of dihydrazone III. According to the rule of
energy interval, the possible increase in the rate of
internal conversion can be due to the presence of
isomers. Therefore, apart from the decrease of the
probability of photogeneration of positive charge
carriers (holes) worsening of the conditions for their
transport is also possible.
The reaction mixture was stirred at this temperature for
4 h until the evolution of hydrogen sulfide ceased [test
with solution of Pb(OAc)2], filtered, the filtrate was
partially evaporated. The precipitate formed was
filtered off, washed with cold methanol, and dried in a
vacuum. 0.14 g (46%) of dihydrazone III was obtained
as strongly electrified cream powder with mp 174–
176°C. IR spectrum, cm–1: 3361 m, 3288 w, 3223 m,
3196 sh [ν(NH2)], 2959 m [ν(CH3)], 2922 w, 2868 w
[ν(CH2)], 1655 w, 1631 w [ν(C=N–N)], 1584 m,
1571m [ν(C=C–S–C=C)], 707 v.s, 641 v.s [ρω(NH2)].
Raman spectrum, ν, cm–1: 3362 v.w (NH2), 2891 v.w
Therefore, by the B3LYP/6-311G(d,p) method in
the gas phase the order of stability of the conformers of
hydrazone III is determined: Е(IIIc) < Е(IIIb) <
Е(IIIa). The results of two-dimensional NMR
spectroscopy (NOESY) are indicative of intercom-
version of conformers IIIa and IIIc in the DMSO-d6
solution. In the solid state, dihydrazone III, by the data
of IR and Raman spectroscopy, exists predominantly
in an NH-associated form. Lability of stereoelectronic
structure of dihydrazone III can be considered as one
of the main reasons explaining a low efficiency of the
found photoeffect.
1
(CH2), 1598 v.s, 1575 v.s (C=C–S–C=C). Н NMR
spectrum (DMSO-d6), δ, ppm: 0.95 s (12Н, CН3), 2.11
s (4Н, 4,4'CН2), 2.13 s (4Н, 6,6'CН2), 6.13 s (2Н, 2НC=),
6.40 br.s (4H, 2NH2). 13C NMR spectrum (DMSO-d6),
δC, ppm: 28.86 (CН3), 31.56 (C5, C5'), 35.55 (C6, C6'),
43.96 (C4, C4'), 129.99 (C2, C2'), 131.17 (C1, C1'),
144.71 (C3, C3'). Found, %: C 62.11; H 8.45; N 17.88;
S 10.83. C16H26N4S. Calculated, %: C 62.75; H 8.50; N
18.30; S 10.46.
b. 0.1 g (0.3 mmol) of dithioxosulfide I and 0.04 g
(1.2 mmol) of hydrazine in 5 ml of anhydrous ethanol
were taken in the reaction carried out at 0–5°C during
4 h. The precipitate formed was filtered off, washed
with cold alcohol, and dried in a vacuum. 0.07 g (78%)
of compound III was obtained.
EXPERIMENTAL
IR spectra were registered on Fourier spectrometers
IFS 25 in KBr pellets and in DMSO solutions (d =
0.0168 cm, с = 0.1 g ml–1) and FT-IR Spectrum HE-
3100 Varian in the solid state using the device of
frustrated total internal reflection (ATR) on the SeZn
crystal. Raman spectra in the solid state were obtained
on a Fourier spectrometer FT-IR Vertex 70 Ram II. 1Н,
13C, and 15N NMR spectra were recorded on a Bruker
DPX 400 spectrometer [working frequency 400.1 (1Н),
100.4 (13C), 40.5 (15N) MHz], external standard
HMDS. The reactions were followed and the purity of
the obtained products checked by the TLC method on
Silufol UV-254 plates, eluent chloroform–ethyl
acetate, 3:1.
c. To the solution of 0.28 g (1 mmol) of bis(5,5-
dimethyl-3-oxocyclohex-1-enyl) sulfide II in 13 ml of
ethanol the solution of 0.096 g (3 mmol) of hydrazine
in 2 ml of ethanol was added dropwise at stirring in an
argon atmosphere at 0–5°C. The reaction mixture was
stirred for 8 h at 20°C until the starting diketone II
disappeared, filtered, the solvent removed in a vacuum.
The solid residue was thoroughly washed with
methanol and dried in vacuum. 0.12 g (39%) of
dihydrazone III was obtained, its mp and the IR
spectrum were identical to that from method а. Found,
%: C 62.98; H 8.79; N 17.45; S 10.63. C16H26N4S.
Calculated, %: C 62.75; H 8.50; N 18.30; S 10.46.
Bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide
I was synthesized according to [2]. Bis(5,5-dimethyl-
3-oxocyclohex-1-enyl) sulfide II was prepared by the
procedure [4].
Quantum chemical calculations were performed
by the DFT(B3LYP) method and 6-311G, 6-311G(d,p)
basis sets with full geometry optimization using
GAUSSIAN-03W program package [6]. IR and
Raman vibration spectra, total energies, zero point
energies, dipole moments, and structures of the most
stable conformers of compounds III and IV having the
Cs symmetry were calculated. BSSE was not taken into
account because of its negligible effect for extended
basis sets [7].
Bis(5,5-dimethyl-3-hydrazonocyclohex-1-enyl)-
sulfide (III). а. To a suspension of 0.31 g (1 mmol) of
bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfide (I)
in 18 ml of anhydrous ethanol a solution of 0.064 g
(2 mmol) of hydrazine in 3 ml ethanol was added at
stirring and continuous bubbling of argon at –10 to –5°C.
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1,7-DITHIOXO-SUBSTITUTED SYSTEMS
291
and Voronkov, M.G., Russ. J. Org. Chem., 2001,
vol. 37, no. 9, p. 1335.
The effect of polar medium (ε = 1–36) on the
energy and structural characteristics, dipole moments,
and vibration spectra of the conformers of the model
compound IV was estimated using the Onsager model
at the DFT(B3LYP)/6-311G level of theory.
5. Timokhina, L.V., Panova, G.M., Kanitskaya, L.V.,
Sokol’nikova, O.V., and Voronkov, M.G., Russ. J. Gen.
Chem., 2004, vol. 74, no. 10, p. 1569; Timokhina, L.V.,
Sokol’nikova, O.V., Kanitskaya, L.V., Fedorov, S.V.,
Toryashinova, D.-S.D., Yashchenko, M.P., and
Voronkov, M.G., Russ. J. Gen. Chem., 2007, vol. 77,
no. 8, p. 1342; Timokhina, L.V., Sokol’nikova, O.V.,
Kanitskaya, L.V., Yashchenko, M.P., and Voron-
kov, M.G., Russ. J. Org. Chem., 2008, vol. 44, no. 4,
p. 532.
Spectral distribution of photoconductivity of
dihydrazone III was obtained on the unit earlier
described by us [8], for the cells of the surface (raster)
and volume (sandwich) types on quartz substrates.
Aluminum and/or silver electrodes were deposited by
thermal evaporation of the metal in a vacuum 5×
10–4 Pa. To exclude the emission to vacuum in the case
of volume cell, semitransparent bottom and non-
transparent upper electrodes were used. Light trans-
mission of the semitransparent electrode was 25–30%.
The cells were made with symmetrical metal
electrodes made of Аl and Ag. The thickness of the
sample was 3–4 µm. As a source of irradiation, xenon
lamp DKsSh 1000 was used. All measurements were
performed in a cryostate in a vacuum of 10–4 Pa.
6. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuse-
ria, G.E., Robb, M.A., Cheeseman, J.R., Montgo-
mery, J.A., Vreven, Jr.T., Kudin, K.N., Burant, J.C.,
Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V.,
Mennucci, B., Cossi, M., Scalmani, G., Rega, N.,
Petersson, G.A., Nakatsuji, H., Hada, M., Ehara, M.,
Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M.,
Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Klene, M.,
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