Carbofunctional Silatrane Possessing Imidazole Moiety: Synthesis, Characterization, and Antibacterial Studies

Article abstract of DOI:10.1080/10426507.2014.902822

1-(3-(1-imidazol-1-yl)propyl)-2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3.0]undecane 3, with imidazole functionality containing transannular N→Si bond (2.13 ?), was synthesized by transetherification reaction of triethanolamine 1 with N-(3-propyltriethoxysilane)imidazole 2. The compound was characterized by elemental analysis, spectroscopic techniques (IR, ¹H NMR, ¹³C NMR, UV-VIS), mass spectrometry, and X-ray diffraction. The thermal stability of silatrane 3 was studied by TGA/DTG/DSC techniques, which is in agreement with the mass spectrometry and X-ray diffraction studies. The structural investigations of 3 were complemented by quantum-chemical studies of the structure. Compound 3 showed slight activity against Escherichia coli and Staphylococcus aureus, while no activity was found against Bacillus subtillus and Vibrio cholera.

Full text of DOI:10.1080/10426507.2014.902822

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Phosphorus, Sulfur, and Silicon and the
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Carbofunctional Silatrane Possessing
Imidazole Moiety: Synthesis,
Characterization, and Antibacterial
Studies
a
a
a
Gurjaspreet Singh , Sheenam Girdhar , Raj Pal Sharma , Przemysław
b
c
Starynowicz & Baljinder Singh
a
Department of Chemistry, Panjab University, Chandigarh 160014,
India
b
Click for updates
Faculty of Chemistry, University of Wroclaw, Poland
c
Department of Biotechnology, Panjab University, Chandigarh
60014, India
1
Accepted author version posted online: 26 Jun 2014.Published
online: 16 Oct 2014.
To cite this article: Gurjaspreet Singh, Sheenam Girdhar, Raj Pal Sharma, Przemysław Starynowicz
Baljinder Singh (2014) Carbofunctional Silatrane Possessing Imidazole Moiety: Synthesis,
Characterization, and Antibacterial Studies, Phosphorus, Sulfur, and Silicon and the Related Elements,
89:11, 1732-1745, DOI: 10.1080/10426507.2014.902822
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Phosphorus, Sulfur, and Silicon, 189:1732–1745, 2014
Copyright ꢀ
Taylor & Francis Group, LLC
C
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2014.902822
CARBOFUNCTIONAL SILATRANE POSSESSING
IMIDAZOLE MOIETY: SYNTHESIS, CHARACTERIZATION,
AND ANTIBACTERIAL STUDIES
1
1
1
Gurjaspreet Singh, Sheenam Girdhar, Raj Pal Sharma,
2
3
Przemysław Starynowicz, and Baljinder Singh
Department of Chemistry, Panjab University, Chandigarh 160014, India
Faculty of Chemistry, University of Wroclaw, Poland
1
2
3
Department of Biotechnology, Panjab University, Chandigarh 160014, India
GRAPHICAL ABSTRACT
Abstract 1-(3-(1-imidazol-1-yl)propyl)-2,8,9-trioxa-5-aza-1-silabicyclo[3.3.3.0]undecane 3,
with imidazole functionality containing transannular N→Si bond (2.13 Å), was synthesized by
transetherification reaction of triethanolamine 1 with N-(3-propyltriethoxysilane)imidazole 2.
1
The compound was characterized by elemental analysis, spectroscopic techniques (IR, H NMR,
1
3
C NMR, UV–VIS), mass spectrometry, and X-ray diffraction. The thermal stability of silatrane
was studied by TGA/DTG/DSC techniques, which is in agreement with the mass spectrometry
3
and X-ray diffraction studies. The structural investigations of 3 were complemented by quantum-
chemical studies of the structure. Compound 3 showed slight activity against Escherichia coli
and Staphylococcus aureus, while no activity was found against Bacillus subtillus and Vibrio
cholera.
Keywords Imidazole; silatrane; N-(3-propyltriethoxysilane)imidazole
Received 26 June 2013; accepted 26 January 2014.
Address correspondence to Dr. Gurjaspreet Singh, Assistant Professor, Department of Chemistry, Panjab
University, Chandigarh 160014, India. E-mail: gjpsingh@pu.ac.in
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gpss.
1
732

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1733
INTRODUCTION
Silatranes, cyclic organosilicon ethers of tris(2-oxyalkyl)amines or their derivatives,
1
have been an expanse of profound study since their discovery in the early sixties. The
immense interest among researchers in these compounds was induced by their unusual
polyhedral structure, the presence of a hypervalent X Si N fragment, their specific phys-
2
–4
ical properties, the often unique reactivity, and a broad spectrum of biological activity.
In the recent years, organopropyl silatranes have been under close scrutiny by various re-
searchers owing to the peculiarities of their electronic and molecular structure and diverse
5
–7
applications.
Nitrogen heterocycles in silatranes have a long history and remain a front-runner for
8
bioactive applications. The imidazole ring is ubiquitous in nature and plays a critical role
9
in many structures within the human body, notably as histamine and histidine. Synthetic
imidazoles are present in many fungicides and antifungal, antiprotozoal, and antihyperten-
sive medications.1
0–12
The presence of a donor pyridine-like nitrogen atom within the ring,
capable of selective binding cationic species also converts the imidazole derivatives into
excellent metal ion sensors.13 The polar imidazole ring suggests a plethora of emerging
14
material science and biophysical applications. The silatranes containing imidazole moi-
15–16
ety are scarce
silatranes. .
and the motivation of this research stems from our previous work on
17
We report herein the preparation of 1-(3-(1-imidazol-1-yl)propyl)-2,8,9-trioxa-
5-aza-1-silabicyclo[3.3.3] undecane 3 derived from triethanolamine 1 and N-(3-
propyltriethoxysilane)-imidazole 2 as well as its structural characterization by single
1
13
crystal X-ray diffraction, IR, H NMR, C NMR, UV–VIS and mass spectrometry. The
thermal stability of 3 was studied using TGA/DTG/DSC techniques. Theoretical methods
such as DFT and HF theory are very important for computing a molecular structure. So,
the results obtained from X-ray crystallography were compared with theoretical studies
such as DFT and HF methods. Anti-microbial activities of silatrane 3 were evaluated
against bacterial culture of Escherichia coli and Bacillus subtillus, Staphylococcus aureus
and Vibrio cholera.
RESULTS AND DISCUSSION
Synthesis
The triethoxysilane 2 was synthesized according to a method published earlier18–19
(Scheme 1). The method of preparation was found to be propitious because of high yield of
desired product as well as of its purity. Silatrane 3 was synthesized by transetherification
reaction of 2 with 1 in the presence of KOH. The general reaction scheme for the synthesis
of 3 is given below (Scheme 2). The product was stable in air and highly soluble in common
organic solvents.
Scheme 1 Formation of triethoxysilane 2.

1
734
G. SINGH ET AL.
Scheme 2 Formation of silatranes 3
Spectroscopic Studies
IR Spectroscopy. The IR spectra of compounds 2 and 3 were recorded in the range
−
1
4
000–400 cm . All bands observed for the silatranyl moiety were consistent with previous
20,21
literature reports.
The absorption peaks of interest were those of Si O, N→Si and C N
1
−
−1
bonds. The bands at 1070 cm and 1097 cm were assigned to the ν(Si-O) stretching
vibration in 2 and 3, respectively. In addition, symmetric deformational vibration of the
silatranyl skeleton with a predominant contribution from the bond N→Si was observed at
− −1 −1
1
5
77 cm . The bands observed at 1507 cm and 1506 cm for 2 and 3, respectively, are
the main characteristic bands indicating the presence of C N group. Two bands observed
−
1
−1
at 1124 cm and 940 cm are characteristic for the symmetric and asymmetric stretching
of the NC3 fragment of the silatrane ring, respectively.
1
13
NMR Spectroscopy. The H and C NMR spectra are consistent with the structure
of synthesized compound 3. On comparing H NMR spectra of 3 with those of 1, a downfield
1
shift for the OCH2 and NCH2 protons of Si(OCH2CH2)3N moiety in 3 was observed. All
protons in the compound 3 were identified and the total number of protons calculated from
1
the integration curve was found to be equal to expected number. In the H NMR spectrum
of compound 3 an upfield shift was observed for SiCH2 protons as compared to 2, which
clearly indicates an increase in electron density at silicon due to the formation of N→Si
dative bond. A triplet appears for the SiCH2 protons at 0.30 ppm due to the presence of
a direct Si–C bond. In addition, a multiplet due to the protons of the CCH2C fragment at
1
.17 ppm was also observed. In the 13C NMR spectrum of silatrane 3 the most shielded
carbon atom belongs to the Si-CH2 moiety and is observed at 13.2 ppm. The signals
observed at 119.0, 128.8, and 137.1 ppm are assigned to the imidazole ring carbon atoms.
Mass Spectrometry. Mass spectra of compound 3 showed the molecular ion
peaks with the addition of H and Na and their fragmentation displays the common features
22
of silatranes. The molecular ion peak, which is also the base peak, appears in the spectra
+
as [M+H] at m/z = 284. The molecular ion peak was more abundant as compared to
silatranyl ion peak. The fragmentation pattern of 3 is shown in Scheme 3.
UV–VIS Spectra. The UV spectra of complex 3 when recorded in ethanol gave a
∗
−1
23,24
peak at 250 nm which was attributed to the π–π transition
in the imidazole group with
2
−1
a molar extinction coefficient ε = 2.7 × 10 M cm (Figure 1). This long wavelength
∗
π–π absorption band successfully experienced a redshift in silatrane 3 relative to that
in the free imidazole25 which showed that the introduction of silatranylpropyl group on
∗
the imidazole ring markedly perturbed the low energy π–π transition in UV spectra of
imidazole similar to that of other azoles such as pyrrole, indole, and carbazole. .
26
Thermogravimetric Analysis. Thermogravimetric analysis (TGA) curve of com-
pound 3 was recorded to study its thermal stability. The complex was heated from 25 to
◦
1
000 C under nitrogen atmosphere. The TGA curve of compound 3 shows mainly two steps:
the first corresponds to the loss of imidazole moiety (calc. = 23.09%, expt. = 23.67%) in

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1735
Scheme 3 Mass fragmentation pattern of compound 3.
◦
the temperature range 110–180 C, which was also confirmed by the mass spectrum of 3;
the second step shows the weight loss of the rest of the molecule (calc. = 76.91%, expt. =
◦
7
6.33%) starting from 225 C (Figure 2). The maximum weight loss was indicated by the
◦
DTG peak at 265 C (Figure 3). In DSC, a small endothermal peak was observed at about
18 C, which was assigned to its melting point (Figure 4).
◦
1
X-Ray Crystallography. Single crystal X-ray diffraction study showed that com-
pound 3 crystallized in a monoclinic crystal system. The X-ray data, selected bond dis-
tances, and angles of compound 3 are listed in Table 1 and 2. An ORTEP type view of
3
with atomic labeling is shown in Figure 5 (thermal ellipsoids have been drawn at 50%
probability level). The five atoms bonded to the silicon atom form a distorted trigonal
bipyramid; such geometry is imposed by the coordination of the tripodal triethanolamine
2.0
1.5
1.0
0.5
250
300
Wavelength (nm)
Figure 1 UV–VIS spectrum of 3 (5 mM solution in ethanol).

1
736
G. SINGH ET AL.
100
80
60
40
20
0
0
100
200
300
400
500
600
700
Temperature (°C)
Figure 2 TGA curve of compound 3.
fragment. The O atoms of the tetradentate ligand occupy equatorial positions and the N
donor is present at apical site trans to the imidazole functionalized alkyl chain. The most
noteworthy parameter is the N→Si bond length of 2.138(2) Å. This value is close to the
average distance in the N(C2H4O)3SiC fragments, 2.146(52) Å, calculated out of 126 frag-
ments retrieved from the CCDC data base. The minimum reported value of this distance,
+
1
.965(5) Å, was found in 1-(dimethyloxonio)silatranium tetrafluoroborate, [(CH3)2O -
27
Si(OCH2CH2)3N]BF4. The shortest N→Si bond (2.095 Å) in a silatrane with a Si–C
28
bond was found in 1-[(silatranyl)methyl]-1,2,4-triazole. On the other hand, the longest
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
100
200
300
400
500
600
700
Temperature (°C)
Figure 3 Deriv. TGA curve of compound 3.

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1737
-
-
-
-
-
-
-
1.0
1.5
2.0
2.5
3.0
3.5
4.0
50
75
100
125
150
175
200
Temperature (°C)
Figure 4 DSC curve of compound 3.
N→Si bonds, 2.421 and 2.32 Å, for this subgroup of silatranes, were observed in 8-
dimethylamino-1-naphthyl)silatrane29 and (-)-(4R,6R,11R)-1,4,6,11-tetramethylsilatrane,
.
30
ClC3H6Si(OCH2CH2)2 [OCH2CH(COOH)]N H2O , respectively.
The present N→Si bond distance is noticeably shorter than the sum of the van der
Waals radii (3.5 Å) and indicates a weak bonding interaction between both the atoms.
The N Si C is a three center four-electron hypervalent bond. The bond angles around
Table 1 Details on X-ray data collection and structure refinement of compound 3
Chemical formula
Mr
C12H21N3O3Si
283.41
Crystal system, space group
Temperature (K)
a, b, c (Å)
Monoclinic, P21/n
100
6.569(2), 11.756(4), 18.287(6)
95.62(3)
◦
β ( )
3
V (Å )
1405.4(8)
Z
4
Radiation type
Mo Kα
0.18
−
1
μ (mm
)
Crystal size (mm)
Data collection
0.43 × 0.33 × 0.18
Tmin, Tmax
0.949, 0.976
9784, 3410, 2718
0.032
No. of measured, independent, and observed [I > 2σ(I)] reflections
Rint
Refinement
R[F > 2σ(F )], wR(F ), S
No. of reflections
2
2
2
0.045, 0.124, 1.10
3410
No. of parameters
No. of restraints
172
0
H-atom treatment
ꢀ
H-atom parameters constrained
0.48, −0.28
ρmax, ꢀρmin (e Å 3)
−

1
738
G. SINGH ET AL.
Table 2 Selected bond lengths (Å) and angles ( ) of silatrane 3
◦
Si—O2
1.6695 (13)
N2—C10
1.342 (2)
Si—O1
Si—O3
Si—C7
Si—N1
O1—C2
O2—C4
O3—C6
1.6696(13)
1.6737(12)
1.8887(17)
2.1379(14)
1.4184(19)
1.4299(19)
1.426(2)
N2—C12
N2—C9
C1—C2
C3—C4
C5—C6
1.368(2)
1.468(2)
1.519(2)
1.517(2)
1.517(2)
C7—C8
C8—C9
1.536(2)
1.515(2)
N1—C5
1.473(2)
C10—N3
1.322(2)
N1—C1
1.473(2)
N3—C11
1.373(3)
N1—C3
1.477(2)
C11—C12
1.371(3)
O2—Si—O1
O2—Si—O3
O1—Si—O3
O2—Si—C7
O1—Si—C7
O3—Si—C7
O2—Si—N1
O1—Si—N1
O3—Si—N1
C7—Si—N1
C2—O1—Si
C4—O2—Si
C6—O3—Si
C5—N1—C1
C5—N1—C3
C1—N1—C3
C5—N1—Si
C1—N1—Si
118.30(7)
118.53(7)
119.37(6)
97.82(7)
95.39(7)
96.33(7)
84.01(6)
83.02(6)
83.44(6)
178.00(6)
123.16(10)
121.32(10)
122.40(10)
112.98(12)
114.02(13)
113.16(12)
105.11(9)
106.00(9)
C3—N1—Si
C10—N2—C12
C10—N2—C9
C12—N2—C9
N1—C1—C2
O1—C2—C1
N1—C3—C4
O2—C4—C3
N1—C5—C6
O3—C6—C5
C8—C7—Si
C9—C8—C7
N2—C9—C8
N3—C10—N2
C10—N3—C11
C12—C11—N3
N2—C12—C11
104.48(9)
106.68(15)
126.82(16)
126.41(16)
105.68(12)
109.04(13)
105.57(12)
108.05(13)
105.97(13)
108.42(13)
113.96(11)
113.40(13)
112.24(13)
113.03(17)
104.11(16)
110.43(17)
105.76(17)
Figure 5 ORTEP diagram of compound 3.

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1739
Figure 6 Packing diagram of compound 3.
the silicon atom may be discussed in terms of pentacoordination character, i.e., percentage
trigonal bipyramid (%TBP). The pentacoordination character could be calculated from three
apical-to-equatorial bond angles and three equatorial-to-equatorial bond angles according
to the Equations (1) and (2). % TBPax and % TBPeq for compound 3 were 66.56% and
88.95%.
ꢀ
ꢂ
ꢁ
θ
%
TBPax = 100% [{109.5 − 1/3
n }/(109.5 − 90.0)]
(1)
(2)
ꢀ
ꢂ
ꢁ
θ
%TBPeq = 100% [{1/3
n − 109.5}/(120.0 − 109.5)]
where θn is average of angles Oeq Si Cax and ϕn is average of angles Oeq Si Oeq.
The values of the %TBP parameters show that the figure spanned by O1, O2, O3,
and C7 may be described as a trigonal pyramid distorted toward a tetrahedron. The crystal
is held together with van der Waals forces only. The shortest intermolecular contacts are:
1
O1· · ·C10 (1 + x, y, z) − 3.246(3) Å (O1· · ·H10 (1 + x, y, z) − 2.62 Å), O2· · ·C5 ( −x,
2
1
2
1
2
1
2
1
2
1
2
+
y, − z) − 3.417(3) Å (O1· · ·H5A ( − x, + y, − z) − 2.47 Å), O3· · ·C1 (−1 +
1
2
x, y, z) − 3.451(3) Å (O3· · ·H1B (−1 + x, y, z) − 2.55 Å) and N3· · ·C4 (−3/2 − x,
−
1
2
1
2
1
2
y, − + z) − 3.435(3) Å (N3· · ·H4A (−3/2 − x, − y, − + z) − 2.56 Å). The packing
diagram is shown in Figure 6.
A comparative study of some characteristic geometrical features of previously re-
ported γ -organopropyl silatranes has been summarized in Table 3.

1
740
G. SINGH ET AL.
Table 3 Comparison of some characteristic geometrical data of γ -organopropyl silatranes
◦
◦
R
N→Si (Å) Si-Oav. (Å)
NSiC ( )
NSiOmean( )
% TBPax
% TBPeq
Lit.
C3H3N2
NCS
SH
OH
NH2
2.13
2.16
2.17
2.17
2.17
1.67
1.65
1.65
1.66
1.66
178.00
178.34
178.60
179.80
179.10
83.49
82.60
82.70
82.70
82.74
66.56
64.46
62.66
62.56
62.76
88.95
86.34
84.76
85.04
84.95
This work
[31]
[32]
[33]
[34]
Computational Studies. Density Functional Theory (DFT) and Hartree–Fock
HF) calculations were performed for compound 3 with the GAUSSIAN 03 software
(
35,36
∗
∗
package
at the 6-31+G (d) and 3-21+G level of theory (Figure 7). The various
geometrical parameters obtained from the crystal data were further compared with the
calculated values obtained from the HF methods and DFT as shown in Table 4.
There were discrepancies between some parameters around the silicon atom for both
gas and solid phases, i.e., crystal-phase structure. The bond angle around the silicon atom,
such as N(1)–Si–C(7), was an important factor to judge how much the geometry around
the silicon atom deviated from a pentacoordinated trigonal bipyramidal structure. In this
theoretical study, however, the N(1)–Si–C(7) bond angle in the gas phase was found to be
◦
◦
around 180 whereas the experimentally determined N(1)–Si–C(7) bond angle was 178.0 .
The most significant geometrical parameter of the silatranes, the N→Si bond length, was
found calculated to be relatively longer than that retrieved from the crystal data. This dis-
3
7–41
crepancy may be due to a shallow vibrational potential of the N→Si bond
and influence
of crystal packing forces. The X-ray studies demonstrated that the bond lengths Si O av.,
Figure 7 Optimized structure of compound 3.

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1741
Table 4 Calculated and X-ray crystallographic data of compound 3
X-ray crystal
data
DFT, B3LYP
3-21G
DFT, B3LYP
6-31G (d)
RHF,
6-31G (d)
∗
∗
∗
∗
PParameters
RHF, 3-21G
N(1)→Si
2.13
1.66
2.31
1.71
2.60
1.67
2.31
1.71
2.70
1.64
Si-O av.
Si-C7
1.88
1.89
1.87
1.89
1.86
N(2)-C(9)
1.46
1.47
1.46
1.46
1.46
N(1)-C(1,3,4)
N(2)-C(10)
1.38
1.34
1.43
1.38
1.44
1.36
1.43
1.38
1.44
1.34
N(3)-C(10)
1.32
1.33
1.31
1.33
1.29
N(2)-C(10)-N(3)
C(9)-N(2)-C(10)
C(7)-C(8)-C(9)
C(8)-C(7)-Si
N(1)-Si-C(7)
O(1)-Si-O(2)
O(1)-Si-O(3)
O(2)-Si-O(3)
C(5)-N(1)-Si
113.03
126.82
113.40
113.96
178.00
118.30
119.37
118.53
105.11
111.78
126.25
113.32
111.99
179.76
118.04
117.70
116.76
103.60
112.45
126.45
114.38
115.15
179.32
113.22
114.50
113.71
98.66
111.78
126.25
113.32
111.99
179.76
118.04
116.76
117.76
103.45
112.88
126.66
114.27
115.12
179.46
112.44
114.68
111.79
96.65
Si–C, N(2)–C(9), N(2)–C(10) and the bond angles N(2)–C(10)–N(3), C(9)–N(2)–C(10),
C(7)–C(8)–C(9) were in accordance with the theoretical data. The variation in other bond
lengths and angles was attributed to the denser packing of molecules which promotes the
intensification of intermolecular interactions and, hence, compression of the molecules.
Biological Activity. To investigate the antibacterial activity compound 3 was dis-
solved in DMSO and the sample was tested in triplicate. DMSO alone was taken as control
and results were compared with control. Antibacterial activity is classified as highly active
(
>14 mm), moderately active (10–14 mm), slightly active (6–10 mm), and less than 5 mm
42
is taken as inactive.
The minimum inhibitory concentration (MIC) of compound 3 was determined using
micro-broth dilution method. In the broth dilution MIC method, various concentrations
of the compound are inoculated with a standard suspension of test bacteria. Following an
◦
overnight incubation at 35 C, the MIC is determined by observing the lowest concentration
of the compounds that will inhibit visible growth of the test bacteria. Growth was determined
photometrically by measuring the optical density (OD) at 600 nm.
OD of organism grown with sample
Percentage of growth =
.
OD of control
The inhibition zone diameter after 12 h was found to be 6 mm for E. coli and
Staphylococcus aureus. MIC50 (defined as the minimum concentration at which 50% of
the isolates were inhibited) of compound 3 against E.coli and Staphylococcus aureus was
120 ± 2 mg/mL.
EXPERIMENTAL
Syntheses
The syntheses were carried out under dry nitrogen atmosphere using vacuum glass
line. The organic solvents used were dried and purified according to standard procedures.

1
742
G. SINGH ET AL.
3-Chloropropyltriethoxysilane (Aldrich) and triethanolamine (Merck) were used as re-
ceived from supplier. N-(3-Propyltriethoxysilane)imidazole 2 was synthesized according
to reported method.
Characterization
Infrared spectra were routinely obtained as Nujol mulls with a Perkin-Elmer RX-I
FT IR spectrometer. C, H, and N analyses were obtained with a FLASH-2000 Organic
+
Elemental Analyzer. Mass spectrometric measurements (TOF MS, ES , 1.38 eV) were
carried out with a VG Analytical (70-S) spectrometer. The electronic spectrum in ethanol
as a solvent was monitored using 10 mm quartz cells with Jasco UV–VIS spectrophotometer
1
13
model V-530. The H and C NMR spectra were recorded with a Jeol and Bruker FT NMR
AL 300 MHz) spectrometer using CDCl3 as solvent. Chemical shifts are reported in ppm
(
relative to tetramethylsilane.
X-Ray Diffraction Studies
An appropriate crystal of 3 was cut from a larger one and mounted on a Kuma
KM4 diffractometer equipped with a CCD counter. The collected data were corrected for
polarization, Lorentz, and absorption, the last calculated from the crystal habits captured
from photo scans. The structure was solved and refined routinely with SHELXS97 and
SHELXL97 programs.4 The positions of the hydrogen atoms (all of them are C-bonded)
were calculated geometrically. All non-H atoms were refined anisotropically, the positions
of the H atoms were geometrically constrained and their isotropic temperature factors were
constrained as 1.2 of the trace of the thermal vibration tensors of the parent C atoms. The
pertinent data are given in Table 1.
3,44
Thermogravimetric Analyses
TGA/DTG/DSC analyses were run on SDT Q 600V20.9 Build 20TGA Instrument.
◦
The sample was loaded in alumina pans and ramped at 10 C/min over a temperature range
of 25–1000 C in dry air at 60 mL/min.
◦
Theoretical Studies
The quantum mechanical calculations were performed with the Gaussian 03 series
programs. Geometries were optimized using Hartree–Fock (HF) calculations and Density
Functional Theory (DFT), using Becke’s three parameter hybrid exchange functional and
∗
the correlation functional of Lee, Yang, and Parr (B3LYP) with basis set at 3-21G and
∗
6-31G (d) level of theory.
Assessment of Antibacterial Activity
Disk Diffusion Method. Antimicrobial activity was determined by the disk dif-
fusion method. In this technique, the filter paper (Whatsmann no. 1) sterile disc of 5 mm
diameter impregnated with test compounds (20, 40, 60, 80, 100 mg/mL of DMSO) were
◦
placed in nutrient agar plate at 37 C for 12 h. The inhibition zones around the dried
impregnated disks were measured after 12 h.

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1743
Test Microorganism. Test isolates were taken from the MTCC (Microbial Type
Culture Collection) at the Institute of Microbial Technology (IMTECH), Chandigarh, India
and included Escherichia coli and Bacillus subtillus, Staphylococcus aureus and Vibrio
cholera.
Synthesis of N-(3-propyltriethoxysilane)imidazole 2. To a suspension of
◦
NaH (0.52 g, 22 mmol) in anhydrous THF (55 mL) at 0 C was added imidazole (1.5 g,
2
2 mmol) and the mixture was allowed to stir for 30 min. 3-Chloropropyltriethoxysilane
◦
(5.29 g, 22 mmol) was then added to the reaction mixture at 0 C. The reaction mixture
was allowed to warm to room temperature and stirred under reflux for a further 24 h.
The reaction mixture was cooled to room temperature, filtered and washed with ether. The
filtrate was concentrated in vacuo and a colorless oil was separated as the final product,
1
which was used as such without any further purification. H NMR (CDCl3): δ = 0.61
(
t, J = 8.1 Hz, 2H, SiCH2), 1.12 (t, J = 7.1 Hz, 6H, CH3), 1.76 (m, 2H, CCH2C), 3.40 (t, J
=
7.8 Hz, 2H, CCH2N), 3.70 (q, J = 7.1 Hz, 9H, OCH2), 6.82 (s, 1H, imidazole-H), 7.39
13
(
(
(
s, 1H, imidazole-H), 7.68 (s, 1H, imidazole-H). C NMR (CDCl3): δ = 7.7 (SiCH2), 17.8
CH3), 26.1 (CCH2C), 46.6 (CCH2N), 57.7 (OCH2), 118.2, 120.9, 134.4 (imidazole-C). IR
−1
Nujol, cm ): 1070 (ν (as)Si OC), 1507 (ν (as)C N).
Synthesis of 1-(3-(1-Imidazol-1-yl)propyl)-2,8,9-trioxa-5-aza-1-silabicy-
clo[3.3.3] undecane (3). N-(3-Propyltriethoxysilane)imidazole (1.00 g, 3.68 mmol)
was added to triethanolamine (0.55 g, 3.68 mmol) in anhydrous benzene with a catalytic
amount of KOH at room temperature in a two-necked flask fitted with a Dean Stark trap.
The resulting mixture was refluxed for 5 h to remove azeotropically the ethanol formed
during the reaction. The solvent was evaporated under vacuum and 10 mL of ether was
added. The content was stirred for 30 min and the product was isolated as a white powder.
The solid was filtered and dried under vacuum. White needle-shaped crystals suitable for
single crystal X-ray analyses were separated after 2 days from the ether extract. M.p.:
◦
1
8
6
(
(
18 C, Yield: 0.87 g, 84%. Anal. Calcd. for C15H27N3O3Si: C, 55.35; H, 8.36; N, 12.91; Si,
−1
.63. Found: C, 55.32; H, 8.34; N, 12.88; Si, 8.64%. IR (Nujol, cm ): 1093 (ν(as)Si OC),
1
22 (ν (as)N→Si), 1506 (ν(as)C N). H NMR (CDCl3): δ = 0.30 (m, 2H, SiCH2), 1.76
m, 2H, CCH2C), 2.72 (t, J = 5.8 Hz, 6H, NCH2), 3.67 (t, J = 5.8 Hz, 6H, OCH2), 3.77
t, J = 7.8 Hz 2H, CCH2N), 6.84 (s, 1H, imidazole-H), 6.92 (s, 1H, imidazole-H), 7.39 (s,
1
5
H, imidazole-H). 13C NMR (CDCl3): δ = 13.2 (SiCH2), 27.2 (CCH2C), 50.3 (CCH2N),
1.1 (NCH2), 57.6 (OCH2), 119.0, 128.8, 137.1 (imidazole-C). MS (m/e, relative intensity,
+
assignment): 284 [100, M + H] , 216.1 [3.33, CH2CH2CH2Si(OCH2CH2)3N], 174.1
+
+
[
27.48, Si(OCH2OCH2)3N ], 306 [8.06, M+Na] .
CONCLUSION
A synthetic methodology for the synthesis of silatrane 1-(3-(1-imidazol-1-yl)propyl)-
,8,9-trioxa-5-aza-1-silabicyclo[3.3.3]undecane has been outlined. The product obtained
2
has been characterized by various physicochemical techniques and its structure confirmed
by single crystal X-ray diffraction. In the present study, anti-microbial activities of sila-
trane 3 were evaluated against bacterial culture of Escherichia coli and Bacillus subtillus,
Staphylococcus aureus and Vibrio cholera. The compound showed slight activity against
Escherichia coli and Staphylococcus aureus but no activity was found against Bacillus sub-
tillus and Vibrio cholera. The results obtained clearly indicated that the compound 3 was
not active toward growth inhibition of Gram negative and Gram positive bacteria under this

1
744
G. SINGH ET AL.
investigation. Instead bacteria(s) utilized these compounds as a source of carbon, nitrogen
and energy.
FUNDING
The authors are thankful to UGC, New Delhi (India) for providing financial support.
SUPPLEMENTAL MATERIAL
Supplementary data for this article can be accessed on the publisher’s website,
www.tandfonline.com/gpss
CCDC-927330 contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data request/cif.
REFERENCES
1
2
3
4
5
6
. Frye, C. L.; Vogel, G. E.; Hall, J. A. J. Am. Chem. Soc. 1961, 83, 996-997.
. Voronkov, M. G. Top. Curr. Chem. 1979, 84, 77-135.
. Verkade, J. G. Coord. Chem. Rev. 1994, 137, 233-295.
. Puri, J. K.; Singh, R.; Chahal, V. K. Chem. Soc. Rev. 2011, 40, 1791-1840.
. Singh, R.; Puri, J. K.; Sharma, R. P.; Malik, A. K.; Ferretti V. J. Mol. Struct. 2010, 982, 107-112.
. Puri, J. K.; Singh, R.; Chahal, V. K.; Sharma, R. P.; Wagler, J.; Kroke E. J. Organomet. Chem.
2011, 696, 1341-1348.
7
8
. Singh, R.; Mutneja, R.; Kaur, V.; Wagler, J.; Kroke, E. J. Organomet. Chem. 2013, 724, 186-191.
. Han, A.; Li, L.; Qing, K.; Qi, X.; Hou, L.; Luo, X.; Shi, S.; Ye, F. Bioorg. Med. Chem. 2013, 23,
1310-1314.
9. Molina, P.; Tarraga, A.; Oton, F. Org. Biomol. Chem. 2012, 10, 1711-1724.
1
1
0. Townsend, L. B. Curr. Med. Chem. 2006, 13, 1-23.
1. Bahnous, M.; Bouraiou, A.; Chelghoum, M.; Bouacida, S.; Roisnel, T.; Smati, F.; Bentchouala,
C.; Gros, P. C.; Belfaitah, A. Bioorg. Med. Chem. Lett. 2013, 23, 1274-1278.
2. Bando, T.; Sugiyama, H. Acc. Chem. Res. 2006, 39, 935-944.
1
1
3. Kumar, D.; Thomas, K. R. Justin; Chen, Y. L.; Jou, Y. C.; Jou, J. H. Tetrahedron 2013, 69,
2594-2602.
1
1
4. Yuea, S.; Li, N.; Biana, J.; Houb, T.; Mab, J. Synth. Met. 2012, 162, 247-256.
5. Sheludyakov, V. D.; Kuzmina, N. E.; Abramkin, A. M.; Korlyukov, A. A.; Arkhipov, D. E.;
Loginov, S. V.; Cheshkov, D. A.; Storozhenko, P. A. Russ. J. Gen. Chem. 2011, 81, 2468-2477.
6. Voronkov, M. G.; Fundamenskii, V. S.; Zelbst, E. A.; Katkevich, Y. V.; Trofimova, O. M.;
Bolgova, Y. I.; Chernov, N. F. Dokl. Chem. 2005, 401, 39-41.
1
1
7. Singh, G.; Saroa, A.; Garg, M.; Sharma, R. P.; Gubanov, A.I.; Smolentsev, A. I. J. Organomet.
Chem. 2012, 719, 21-25.
1
1
2
2
8. Miao, J.; Wan, H.; Shao, Y.; Guan, G.; Xu, B. J. Mol. Catal. A: Chem. 2011, 348, 77-82.
9. Zhang, Q.; Luo, J.; Wei, Y. Green Chem. 2010, 12, 2246-2254.
0. Yamamoto, T.; Terada, A.; Muramatsu, T.; Ikeda, K. Org. Prep. Proced. Int. 1994, 26, 555-556.
1. Yamamoto, T.; Sugiyama, S.; Akimoto, K.; Hayashi, K. Org. Prep. Proced. Int. 1992, 24, 346-
348.
2
2. Pestunovich, V. A.; Kirpichenko, S. V.; Voronkov, M. G. Silatranes and their tricyclic analogues.
In: Z. Rappoport, Y. Apeloig(Eds.), Chemistry ofOrganic SiliconCompounds; Wiley: Chichester,
UK, 1998, 1447-1537.
2
3. Fujiwara, S. T.; Gushikem Y. J. Braz. Chem. Soc., 1999, 10, 389-393.

CARBOFUNCTIONAL SILATRANE POSSESSING IMIDAZOLE MOIETY
1745
2
2
2
4. Vickers M. S.; Martindale K. S.; Beer, P. D. J. Mater. Chem., 2005, 15, 2784-2790.
5. Andres, L. S.; Fulscher, M. P.; Roos, B. O. J. Phys. Chem. 1996, 100, 6484-649.
6. Voronkov, M. G.; Trofimova, O. M.; Turchaninov, V. K.; Zelbst, E. A.; Bolgova, Y. I.; Belyaeva,
V. V.; Larina L. I.; Aksamentova, T. N.; Mikhaleva A. I.; Chernov N. F. Russ. J. Org. Chem.,
2003, 39, 1458-1466.
2
2
2
7. Garant, R. J.; Daniels, L. M.; Das, S. K.; Janakiraman, M. N.; Jacobson, R. A.; Verkade, J. G. J.
Am. Chem. Soc. 1991, 113, 5728-5735.
8. Voronkov, M. G.; Zelbst, E. A.; Kashaev, A. A.; Trofimova, O. M.; Bolgova, Y. I.; Fundamenski,
V. S.; Chernov, N. F. Dokl. Akad. Nauk SSSR 2001, 376, 5-7.
9. Carre, F.; Cerveau, G.; Chuit, C.; Corriu, R. J. P.; Nayyar, N. K.; Reye, C. Organometallics 1990,
9, 1989-1991.
3
0. Stachel, S. J.; Ziller, J. W.; Van Vranken D. L. Tetrahedron Lett. 1999, 40, 5811-5812.
3
1. Singh, R.; Puri, J. K.; Chahal, V. K.; Sharma, R. P.; Venugopalan, P. J. Organomet. Chem. 2010,
6
95, 183-188.
2. Dumitriu, A. M. C.; Cazacu, M.; Shova, S.; Turta, C.; Simionescu, B. C. Polyhedron 2012, 33,
19-126.
3
1
33. Hencsei, P.; Kovaks, I. J. Organomet. Chem. 1989, 377, 19-23.
34. Hencsei, P.; Pktiyi, L.; Fulop, V.; Baryshok, V. P.; Voronkov M. G., Kuznetsova, G. A. J.
Organomet. Chem. 1988, 346, 315-320.
3
3
3
3
5. Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
6. Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785-789.
7. Belyaeva, V. V.; Frolov, Y. L.; Voronkov, M. G. J. Struct. Chem. 2005, 46, 1072-1076.
8. Trofimov, A. B.; Zakrzewski, V. G.; Dolgounitcheva, O.; Ortiz, J. V.; Sidorkin, V. F.; Belogolova,
E. F.; Belogolov, M.; Pestunovich, V. A. J. Am. Chem. Soc. 2005, 127, 986-995.
9. Shishkov, I. F.; Khristenko, L. V.; Rudakov, F. M.; Golubinskii, A. B.; Vilkov, L. V. Karlov, S.
S.; Zaitseva, G. S.; Samdal, S. Struct. Chem. 2004, 15, 11-16.
3
4
4
4
0. Korlyukov, A. A.; Lyssenko, K. A.; Antipin, M. Y.; Kirin, V. N.; E. A. Chernyshev, E. A.;
Knyazev, S. P. Inorg. Chem. 2002, 41, 5043-5051.
1. Alkorta, I.; Elguero, J.; Fruchier, A.; Macquarrie, D. J.; Virgili, A. J. Organomet. Chem. 2001,
25, 148-153.
2. Sharmroukh, A. H.; Zaki, M. E. A.; Morsy, E. M. H.; Abdel-Megeid, F. M. E. Arch. Pharm.
007, 340, 345-351.
6
2
4
4
3. Sheldrick, G. M. SHELXS-97, Program for Structure Solution, University of G o¨ ttingen, 1997.
4. Sheldrick, G. M. SHELXL-97, Program for Structure Refinement, University of G o¨ ttingen, 1997.