Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups
The thione-thiol tautomerism has been investigated of thiourea groups grafted to silica surface in the presence of water molecules. The configuration of the transition state has been calculated by quantum chemical modeling of a N, N'-dimethylthiourea (DMTU) molecule in the forms of (CH₃)₂(NH₂)...
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Інститут хімії поверхні ім. О.О. Чуйка НАН України
2015
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| Cite this: | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups / O.V. Smirnova, A.G. Grebenyuk, Yu.L. Zub // Поверхность. — 2015. — Вип. 7 (22). — С. 62-69. — Бібліогр.: 22 назв. — англ. |
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| author | Smirnova, O.V. Grebenyuk, A.G. Zub, Yu.L. |
| author_facet | Smirnova, O.V. Grebenyuk, A.G. Zub, Yu.L. |
| citation_txt | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups / O.V. Smirnova, A.G. Grebenyuk, Yu.L. Zub // Поверхность. — 2015. — Вип. 7 (22). — С. 62-69. — Бібліогр.: 22 назв. — англ. |
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| description | The thione-thiol tautomerism has been investigated of thiourea groups grafted to silica surface in the presence of water molecules. The configuration of the transition state has been calculated by quantum chemical modeling of a N, N'-dimethylthiourea (DMTU) molecule in the forms of (CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ and of fragment silica clusters (HO)₃SiCH₂NHC(S)NHCH₃ with one water molecule (density functional theory method, B3LYP/6-31G (d, p)). The value of the total energy of the transition state with one water molecule and the activation energy of the thione-thiol tautomeric transition for different conformations of the system were obtained. The results of these calculations have shown that the activation barrier in the presence of a silica matrix decreases. The activation barrier in the studied systems is higher than that in similar systems in vacuum.
В работе была изучена тион-тиольная таутомерия тиомочевинных групп, привитых на поверхности диоксида кремния, в присутствии молекулы воды. Конфигурация переходного состояния была рассчитана путем моделирования молекулы N, N-диметилтиомочевины в формах ((CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ и фрагмента кластеров кремнезема (HO)₃SiCH₂NHC(S)NHCH₃ с одной молекулой воды методами квантовой химии (теория функционала плотности, метод B3LYP / 6-31G (d, р)). Были получены значения полной энергии переходного состояния с одной молекулой воды и энергии активации тион-тиольного таутомерного перехода для различных конформаций системы. Результаты этих расчетов показали, что в присутствии матрицы кремнезема активационный барьер уменьшается. В изученных системах он выше, чем в аналогичных системах в вакууме.
Було досліджено тіон-тіольну таутомерiю в присутності молекул води груп тіосечовини, прищеплених на поверхні діоксиду кремнію. Конфігурація перехідного стану була розрахована шляхом моделювання молекули N, N-диметілтіосечовини в формах (CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ і фрагментa кластерів кремнезему (HO)₃SiCH₂NHC(S)NHCH₃ з однією молекулою води методами квантової-хімії (теорія функціоналу густини, метод B3LYP / 6-31G (d, р)). Було отримано значення повної енергії перехідного стану з однією молекулою води і енергії активації тіон-тіольного таутомерного переходу для різних конформацій системи. Результати цих розрахунків показали, що в присутності матриці кремнезему бар'єр активації зменшується. У вивчених системах він вищий, ніж в аналогічних системах у вакуумі.
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| first_indexed | 2025-12-07T15:11:52Z |
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Поверхность. 2015. Вып. 7(22). С. 62–70 62
UDC 544.723 : 544.127
INFLUENCE OF NANOSILICA SURFACE ON THIONE-
THIOL TAUTOMERISM OF GRAFTED THIOUREA GROUPS
O.V. Smirnova, A.G. Grebenyuk, Yu.L. Zub
Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine,
17 General Naumov str., Kyiv 03164, Ukraine. e-mail: osmirnova@isc.gov.ua
The thione-thiol tautomerism has been investigated of thiourea groups grafted to silica
surface in the presence of water molecules. The configuration of the transition state has been
calculated by quantum chemical modeling of a N, N'-dimethylthiourea (DMTU) molecule in the
forms of (CH3)2(NH2)2CS/CH3NHCSHNCH3 and of fragment silica clusters
(HO)3SiCH2NHC(S)NHCH3 with one water molecule (density functional theory method, B3LYP/6-31G
(d, p)). The value of the total energy of the transition state with one water molecule and the activation
energy of the thione-thiol tautomeric transition for different conformations of the system were
obtained. The results of these calculations have shown that the activation barrier in the presence of a
silica matrix decreases. The activation barrier in the studied systems is higher than that in similar
systems in vacuum.
Introduction
Thiourea derivatives have a wide spectrum of biological activities including
antibacterial, antifungal, TB, antihelminthic, insecticidal, herbicidal effect and the properties
of the plant growth regulator [1, 2-5]. Acidic solutions of thiourea were examined as an
alternative to cyanide extraction of the precious metals due to their fast kinetics and low
toxicity [6]. Complex compounds of thiourea are characterized by a very high and selective
extraction and transportation Ag (I) in the presence of Co (II), Ni (II), Cu (II), Zn (II), Cd (II)
and Pb (II) using the method of the gradient pH [7]. The first example
(CH3C(O)NHC(S)NH2) of this class of molecules has been known for more than a century
ago [7]. Acyl (aroyl) thiourea ligands were used for extraction of gold (III) [8].
It is known that compounds containing composition thiourea fragments [–NH–C(=S)–
NH–] are good complexing compounds. Thiourea derivatives behave generally as flat ligands,
where S and N atoms act as donors involved in coordination to the metal center. The
substituted thioureas have, however, a greater diversity in the coordination chemistry, which
are connected with their conformational isomers, steric effects, the presence of donor groups
in substituted and intra-molecular interactions [1]. This capability of urea and thiourea moiety
to form H-bond also contributes to the formation of gels [9]. Thiourea fragments can exist in
two tautomeric forms - thione and thiol, [–NH–C(=S)–NH–] and [–N=C(SН)–NH–]. Various
factors such as pH of the medium [7], the nature of the solvent [10, 11] have the greatest
influence on the shift of the tautomeric equilibrium in either direction, as tautomeric
transitions caused prototropic binary equilibrium. The high mobility of thione-thiol balance
and speed of mutual transformations considered prototropic tautomeric forms leads to the fact
that they rarely isolate in pure form and calculate the proportion. It should be added that the
simple cations often unstable. Thiourea monomers that have been highlighted in the low-
temperature argon matrix are solely thione tautomeric form [12]. Upon UV irradiation (I> 300
nm) there is a photo reaction, the result of which is to convert the initial isomer compound in
its thiol tautomer [12]. This is only possible mechanism for the conversion of the ground state
of the thiol form in thionyl at low temperature proton tunneling through very high energy
barrier of 9030 cm-1 (108 kJ mol-1) (MP2/6-31++G(d,p)). The structure of the
photoproduction of species was determined by comparing the experimental spectra with the
63
theoretically calculated IR spectra obtained by DFT (B3LYP)/6-31++G(d,p) [12]. As one of
the compounds containing thiourea fragments –NH–C(=S)–NH–, silica was used
functionalized with thiourea groups [≡SiCH2NHC(S)NHCH3] [13]. So the question of the
existence of the fragment shape on the silica surface [≡SiCH2NHC(S)NHCH3], and the
influence of the surface and the water molecules on the process - both before and after the
sorption process becomes important.
The aim of this work is the quantum-chemical analysis of the IR spectra of the surface
layer of silica functionalized with thiourea groups [≡SiCH2NHC(S)NHCH3], which coexist in
the Thione and thiol forms in the presence of water molecules. As a model of the ligand center
molecule was chosen of the N, N'-dimethylthiourea (DMTU) in various forms and a surface
fragment of [(НО)3SiCH2NHC(S)NHCH3], simulating a trifunctional silane
[(С2Н5О)3Si(CH2)3NHC(S)NHC2H5], used in practice [13].
Experiments
IR spectra. FT-IR spectra of synthesized materials [13] were recorded on a Thermo Nicolet
Nexus Fourier-transform infrared spectrometer in the 400–4000 cm-1 range, working in ‘‘Nexus
Smart Collector’’ mode with a resolution of 8 cm-1. The samples were previously ground with
solid KBr (Fluka, for IR spectroscopy). The sample/KBr mass ratio was 1/30. The spectra were
analyzed using software ‘‘OMNIC’’.
Quantum chemical calculations. Quantum chemical calculations on the total energy of the
optimized geometrical structures of thione and thiol forms of N, N'-dimethylthiourea and of the
fragment (НО)3SiCH2NHC(S)NHCH3 were performed using density functional theory method
(DFT) [14] and the hybrid B3LYP potential [15] with basis set 6-31G (d, p).
Such calculation methods have been successfully used for the interpretation of the
vibrational spectra are similar in chemical structure of compounds (proton transfer processes in
thiourea) [12].
The calculated vibrational frequencies in the IR spectra were used as scaled by a factor
of 0.95. Calculations were performed by means of the software package PC GAMESS [16]
(version FireFly 8.0.0 (http://classic.chem.msu.su/gran/firefly/index.html) by A.Granovsky).
Results
The spectrum of tetraethoxysilane (TEOS) was recorded in liquid form between KRS
plates [13]. The vibrational spectra (IR and Raman) regularly provide useful information on the
electronic structure and the conformation of the molecule. Information about the research
focused on the probable correlations between the IR and Raman spectra of the studied thiourea
derivatives and their capability to form complexes with heavy metal ions exists in the literature
[1]. This group of compounds was tested as ionophores in ion-selective electrodes [17].
Note that the analysis of the IR spectra of the complexes formed in the surface layer of
mesoporous silicas with complexing group structure ≡Si(CH2)3NHC(S) NHC2H5 was found to
have not single but two absorption bands, which are connected with taking part in the
coordination group -NH-C(S)-NH- [18]. Note also that in obtaining mesoporous sorbent with
thiourea groups by templating method [8, 18, 19] of mesophase surfactant removal can be
carried out under different conditions - refers to the nature of the solvent, the acidity of the
environment. This, in turn, may account for the appearance on the support surface of tautomeric
equilibrium which can stabilize the surface. Since the above assumption was based on the
analysis of the IR spectra, it is noted that the thiourea moiety has no distinct characteristic
absorption band [13]. The absorption band at ~ 1560 cm-1 is generally identified by the
fragment due to the contribution of several oscillations. The absorption bands corresponding to
stretching vibrations ν (C = S) form or thionyl ν (S-H) thiol, have a low intensity. Therefore, the
low content of fixed thiourea ligand (which is typical for the vast majority of sorbents), their
identification is difficult also for these absorption bands. It becomes even more problematic if
64
the content of the thiol tautomer is substantially minimal as compared to thione one. Finally, if
the absorption band at ν (S-H) is in 2560 cm-1, in which the absorption bands of other ligands
fixed very rarely, the absorption band at ν (C = S), located in the IR spectrum at ~ 630 cm-1; It
can often be masked by other absorption bands.
As it well known, organic compounds, containing thiourea group such as -NH-C (= S)-
NH- , can exist in two tautomeric forms - thione and thiol. Previously [20-22], we designed a
model of silica surface layer formed due to hydrolytic polycondensation of three- and
tetraalkoxysilanes. This silica surface considered bears grafted thiourea groups in thione form.
In this article N, N'-dimethylthiourea groups were selected as models for thiourea complexing
center in thione, thiol forms, transition state and a form where proton is substituted with sodium
cation.
In this article molecule N, N'-dimethyl thiourea and molecular fragment
(НО)3SiCH2NHC(S)NHCH3 silica matrix with the presence of a single water molecule were
selected as models. We also studied the effect of water molecules on the energy barrier of the
thione-thiol transition. Configurations, total energy, and parameters of the optimized
geometrical structure of various forms of N,N'-dimethylthiourea with one water molecule are
presented in Fig. 1 and Table 1.
1 2 (TS) 3
-703.28341 -703.23334 -703.25369
Fig. 1. The total energy calculated (E, a.u.) of the N, N'-dimethylthiourea (DMTU) with one
water molecule in various forms: 1 - thione, 2 - transition state, 3- thiol.
Table 1. Parameters (bond lengths, Ǻ; the angles, degrees) of the optimized geometrical
structures of various forms of N, N'-dimethylthiourea (DMTU) with one water
molecule*
1 2 (TS) 3
DMTU
RSH - 1.630 1.370
RCS 1.707 1.798 1.799
RCN 1.349, 1.368 1.305, 1.376 1.282, 1.392
RNC 1.459, 1.465 1.464, 1.449 1.456, 1.466
RCH 1.092 - 1.095 1.098 – 1.091 1.090 - 1.098
RNH 1.024, 1.010 1.012, 1.396 1.012
<HSC - 91.80 94.92
<SCN 122.17, 119.17 115.17, 114.21 120.11, 112.29
<NCN 118.66 130.62 127.59
<CNH 114.04, 110.56 112.99, 113.60 112.07
<NCH 107.88 – 112.99 107.55 – 118.31 107.93 – 112.81
DMTU+H2O
RS-HOH 2.374 1.27243 1.910
RNH-OH2 1.891 1.12178 1.862
<S-HO(H) 145.980 152.841 154.108
<NH-O(H2) 163.406 159.578 156.365
*Structure numbers 1,2,3 are shown in Fig. 1.
65
In addition, for a molecular fragment (НО)3SiCH2NHC(S)NHCH3, quantum chemical
calculations were performed. Complexing site of this fragment is identical to that in the three
functional silane (С2Н5О)3Si(CH2)3NHC(S)NHC2H5, which is widely used to produce of
functionalized polysiloxane xerogels and mesoporous silicas [13]. Thus it considered thione
(4), thiol form (6), and transition state (5) (see. Fig. 2 and Table 2).
4 5 (TS) 6
-1219.80078 -1219.72693 -1219.77830
Fig. 2. The calculated total energy (E, a.u.) of molecular fragment
(HO)3SiCH2NHC(S)NHCH3 with one water molecule in various forms: 4 - thione, 6-
transition state and 5 – thiol.
Table 2. Parameters (bond lengths, Ǻ; the angles, degrees) of the optimized geometry of
molecular fragment (НО)3SiCH2NHC(S)NHCH3 in various forms with one water
molecule*
4 5(TS) 6
(НО)3SiCH2NHC(S)NHCH3
RSH - 1.653 1.353
RCS 1.692 1.782 1.830
RCN 1.352, 1.378 1.341, 1.352 1.286, 1.362
RNC 1.466, 1.469 1.465, 1.486 1.467, 1.460
RCH 1.095 - 1.092 1.092 – 1.098 1.093 - 1.096
RNH 1.094 1.011, 1.38539 1.008
RSiO 1.653 - 1.658 1.655 -1.662 1.646 - 1.665
<HSC - 83.58 92.74
<SCN 120.70, 123.72 112.142, 126.87 111.48, 125.75
<NCN 115.55 120.25 122.77
<NCSi 115.28 115.92 117.33
<CSiO 111.99 - 112.25 101.88 – 113.29 101.30- 112.90
<CNH 113.65, 114.70 112.79, 94.617 114.84
<NCH 110.85, 107.11 106.26, 110.60 110.34, 106.93
<SiCH 107.37, 111.55 106.56, 109.76 107.99, 107.08
<OSiO 106.22 – 115.31 104.59 – 108.40 108.07 - 114.63
<SiOH 113.55 - 114.02 113.84 – 115.93 107.72- 115.57
(НО)3SiCH2NHC(S)NHCH3+H2O
RS-HOH 2.497 1.178 2.249
RNH…OH2 4.207 1.181 2.444
<S-HO(H) 162.074 152.22 139.775
<NH-O(H2) 61.419 149.70 131.140
*Structure numbers 4,5,6 are shown in Fig. 2.
Discussion
The results of quantum chemical calculations on the total energy of the transition
complex in vacuum and on the activation energy values of thione-thiol tautomeric transition
between different conformations are shown in Fig. 3.
66
a
b
Fig. 3. Energy tautomeric transition diagram of N, N'-dimethylthiourea (a) and of fragment
silica cluster with the functional group [-NHC(S)NH-] (b) (see text; the structures
mentioned are enumerated correspondingly to those shown in Figs. 1 and 2).
Without water molecule, activation energy of the transition between the thione 1 and 2
forms of thiol N,N'-dimethylthiourea molecule was EA = 69.05 kJ / mol [23], whereas in the
presence of water molecules, it is EA = 78.03 kJ / mol. Respectively, for a molecular fragment
simulating the silica surface with a functional group [-NHC(S)NH-], this value was EA =
47.52 kJ / mol in the case of transition 4 - 5 or EA = 75,88 kJ / mol in the case of transition 4 -
5 ' [23], whereas in the presence of water molecules, it is EA = 59.01 kJ / mol (Fig. 4). It is
obvious that in the presence of water molecules, the activation barrier is reduced by
participatory silica matrix. With respect to the vacuum system, the activation barrier is higher
than that in the system involving a water molecule.
Analysis of the energy gap E between the frontier orbitals (22 α, β, 23 α, β and 53 α, β,
54 α, β) and charge distribution for the N, N'-dimethylthiourea of the molecule and the surface
of the silica with the functional group [-NHC(S)NH-] in the presence of water molecules, can
be used to determine the magnitude and electron donor and electron acceptor abilities of these
compounds.
The charge distribution, and the surface contour of the upper surface of the occupied
orbitals of N, N'-dimethylthiourea of the molecule (Fig. 4) and the surface of silica with the
functional group [-NHC(S)NH-] (Fig.5) in the presence of water molecules are presented in
Figs. 5, 6.
67
The surface shape of the last occupied orbital (23 - for the molecule N, N'-
dimethylthiourea (Fig. 4 a) and 53 - for functionalized of groups [-NHC(S)NH-] silica surface
interacting with a water molecule (Fig. 5 a) are different. It has a spherical shape in the first
case, dumbbell - in the second case, which is caused by the influence of the silica matrix.
a b
Fig. 4. Occupied MO (a); surfaces contours and charge distributions (b) for N,N'-
dimethylthiourea molecule in the presence of water molecules.
a b
Fig. 5. Occupied MO (a); surfaces contours and charge distributions (b) for molecular
fragment simulating the silica surface with a functional group [-NHC(S)NH-] in the
presence of water molecules.
As seen from the analysis of quantum chemical calculation of transition states (TS),
complex molecule N,N'-dimethylthiourea and functionalized of groups [-NHC(S)NH-] silica
surface interacting with a water molecule are flat, because all atoms lie in one plane and have
sp2 hybridization. Differences in the distribution of densities in the HOMO of N,N'-
dimethylthiourea molecule (Fig.4 b), and silica surface functionalized by [-NHC(S)NH-]
groups interacting with a water molecule are observed (Figure 5, b). In transition state, on the
nitrogen atom which is H-bonded to the sulfur atom through a water molecule, there is a
region of negative charge (indicated by green). On the second nitrogen atom covalently
bonded to a hydrogen atom, there are areas of both positive and negative charges; on the
68
sulfur atom - positive charge (Fig. 4, b). In the presence of the silica matrix, on a nitrogen
atom which is covalently bonded to and hydrogen through a spacer bound to a silicon atom,
there is a region of negative charge (indicated by green). In transition state, on the nitrogen
atom which is H-bonded to the sulfur atom through a water molecule, there is an area of
positive charge (indicated in red). As shown in Figure 6b, on the oxygen atom in a water
molecule is a region of negative charge, on the sulfur atom - positive. Interaction with the
oxygen atom in the water molecule occurs at the point of tangency circuits electron density
distribution of the nitrogen atom (positive), water molecules (negative), hydrogen and sulfur
atoms (positive) (Fig. 5, b). Thus, the electron-acceptor ability of silica surface functionalized
with groups [-NHC(S)NH-] interacting with a water molecule is considerably higher than the
corresponding value for the molecule of N,N'-dimethylthiourea and both systems are
characterized by a nitrogen atom which is H-bonded to the sulfur atom through a water
molecule.
After analyzing the results of the calculations, it can be concluded that the presence of
the silica matrix the band gap raises as compared with that of N,N'-dimethylthiourea molecule
(E= 9.18 eV), in the presence of water molecules (E= 13.26 eV).
Thus, by quantum chemical calculations, one can see the effect of the silica matrix to
change the distribution of the surface of the lowest occupied orbital, electron densities and the
band gap of the molecule as compared to those of N,N'-dimethylthiourea.
Summary and conclusions
On the basis of quantum-chemical calculations performed to analyze the thione-thiol
tautomerism, we can draw the following conclusions. In the systems of N, N'-
dimethylthiourea in forms (CH3)2(NH2)2CS / CH3NHCSHNCH3 / CH3NHCSNaNCH3 and the
silica cluster fragment (HO)3SiCH2NHC (S) NHCH3 with a water molecule, the activation
barrier is reduced by participatory silica matrix. With respect to the vacuum system, the
activation barrier is higher than that in the system with a water molecule. Therefore, the
lowest activation barrier of thione-thiol equilibrium is that in the presence of silica surface in
vacuum.
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ВЛИЯНИЕ ПОВЕРХНОСТИ КРЕМНЕЗЕМА НА ТИОН-TИОЛЬНУЮ
ТАУТОМЕРИЮ ПРИВИТЫХ ГРУПП ТИОМОЧЕВИНЫ
О.В. Смирнова, А.Г. Гребенюк, Ю.Л. Зуб
Институт химии поверхности им. А.А. Чуйко Национальной академии наук Украины,
ул. Генерала Наумова, 17, 03164 Киев, Украина, e-mail: osmirnova@isc.gov.ua
В работе была изучена тион-тиольная таутомерия тиомочевинных групп,
привитых на поверхности диоксида кремния, в присутствии молекулы воды.
Конфигурация переходного состояния была рассчитана путем моделирования
молекулы N, N-диметилтиомочевины в формах (CH3)2(NH2)2CS / CH3NHCSHNCH3 и
фрагмента кластеров кремнезема (HO)3SiCH2NHC(S)NHCH3 с одной молекулой воды
методами квантовой химии (теория функционала плотности, метод B3LYP / 6-31G (d,
р)). Были получены значения полной энергии переходного состояния с одной молекулой
воды и энергии активации тион-тиольного таутомерного перехода для различных
конформаций системы. Результаты этих расчетов показали, что в присутствии
матрицы кремнезема активационный барьер уменьшается. В изученных системах он
выше, чем в аналогичных системах в вакууме.
ВПЛИВ ПОВЕРХНІ КРЕМНЕЗЕМУ НА ТIОН-TIОЛЬНУ ТАУТОМЕРІЮ
ПРИЩЕПЛЕНИХ ГРУП ТІОСЕЧОВИНИ
О.В. Смiрнова, А.Г. Гребенюк, Ю.Л. Зуб
Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України,
вул. Генерала Наумова, 17, 03164 Київ, Україна, e-mail: osmirnova@isc.gov.ua
Було досліджено тіон-тіольну таутомерiю в присутності молекул води груп
тіосечовини, прищеплених на поверхні діоксиду кремнію. Конфігурація перехідного
стану була розрахована шляхом моделювання молекули N, N-диметілтіосечовини в
формах (CH3)2(NH2)2CS / CH3NHCSHNCH3 і фрагментa кластерів кремнезему
(HO)3SiCH2NHC(S)NHCH3 з однією молекулою води методами квантової-хімії (теорія
функціоналу густини, метод B3LYP / 6-31G (d, р)). Було отримано значення повної
енергії перехідного стану з однією молекулою води і енергії активації тіон-тіольного
таутомерного переходу для різних конформацій системи. Результати цих розрахунків
показали, що в присутності матриці кремнезему бар'єр активації зменшується. У
вивчених системах він вищий, ніж в аналогічних системах у вакуумі.
|
| id | nasplib_isofts_kiev_ua-123456789-148458 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 2617-5975 |
| language | English |
| last_indexed | 2025-12-07T15:11:52Z |
| publishDate | 2015 |
| publisher | Інститут хімії поверхні ім. О.О. Чуйка НАН України |
| record_format | dspace |
| spelling | Smirnova, O.V. Grebenyuk, A.G. Zub, Yu.L. 2019-02-18T13:01:33Z 2019-02-18T13:01:33Z 2015 Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups / O.V. Smirnova, A.G. Grebenyuk, Yu.L. Zub // Поверхность. — 2015. — Вип. 7 (22). — С. 62-69. — Бібліогр.: 22 назв. — англ. 2617-5975 https://nasplib.isofts.kiev.ua/handle/123456789/148458 544.723 : 544.127 The thione-thiol tautomerism has been investigated of thiourea groups grafted to silica surface in the presence of water molecules. The configuration of the transition state has been calculated by quantum chemical modeling of a N, N'-dimethylthiourea (DMTU) molecule in the forms of (CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ and of fragment silica clusters (HO)₃SiCH₂NHC(S)NHCH₃ with one water molecule (density functional theory method, B3LYP/6-31G (d, p)). The value of the total energy of the transition state with one water molecule and the activation energy of the thione-thiol tautomeric transition for different conformations of the system were obtained. The results of these calculations have shown that the activation barrier in the presence of a silica matrix decreases. The activation barrier in the studied systems is higher than that in similar systems in vacuum. В работе была изучена тион-тиольная таутомерия тиомочевинных групп, привитых на поверхности диоксида кремния, в присутствии молекулы воды. Конфигурация переходного состояния была рассчитана путем моделирования молекулы N, N-диметилтиомочевины в формах ((CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ и фрагмента кластеров кремнезема (HO)₃SiCH₂NHC(S)NHCH₃ с одной молекулой воды методами квантовой химии (теория функционала плотности, метод B3LYP / 6-31G (d, р)). Были получены значения полной энергии переходного состояния с одной молекулой воды и энергии активации тион-тиольного таутомерного перехода для различных конформаций системы. Результаты этих расчетов показали, что в присутствии матрицы кремнезема активационный барьер уменьшается. В изученных системах он выше, чем в аналогичных системах в вакууме. Було досліджено тіон-тіольну таутомерiю в присутності молекул води груп тіосечовини, прищеплених на поверхні діоксиду кремнію. Конфігурація перехідного стану була розрахована шляхом моделювання молекули N, N-диметілтіосечовини в формах (CH₃)₂(NH₂)₂CS/CH₃NHCSHNCH₃ і фрагментa кластерів кремнезему (HO)₃SiCH₂NHC(S)NHCH₃ з однією молекулою води методами квантової-хімії (теорія функціоналу густини, метод B3LYP / 6-31G (d, р)). Було отримано значення повної енергії перехідного стану з однією молекулою води і енергії активації тіон-тіольного таутомерного переходу для різних конформацій системи. Результати цих розрахунків показали, що в присутності матриці кремнезему бар'єр активації зменшується. У вивчених системах він вищий, ніж в аналогічних системах у вакуумі. en Інститут хімії поверхні ім. О.О. Чуйка НАН України Поверхность Теория химического строения и реакционной способности поверхности. Моделирование процессов на поверхности Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups Влияние поверхности кремнезема на тион-tиольную таутомерию привитых групп тиомочевины Вплив поверхні кремнезему на тiон-tiольну таутомерію прищеплених груп тіосечовини Article published earlier |
| spellingShingle | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups Smirnova, O.V. Grebenyuk, A.G. Zub, Yu.L. Теория химического строения и реакционной способности поверхности. Моделирование процессов на поверхности |
| title | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| title_alt | Влияние поверхности кремнезема на тион-tиольную таутомерию привитых групп тиомочевины Вплив поверхні кремнезему на тiон-tiольну таутомерію прищеплених груп тіосечовини |
| title_full | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| title_fullStr | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| title_full_unstemmed | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| title_short | Influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| title_sort | influence of nanosilica surface on thione-thiol tautomerism of grafted thiourea groups |
| topic | Теория химического строения и реакционной способности поверхности. Моделирование процессов на поверхности |
| topic_facet | Теория химического строения и реакционной способности поверхности. Моделирование процессов на поверхности |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/148458 |
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