3β-Acetoxy-6-nitrocholest-5-ene: Crystal structure, thermal, optical and dielectrical behavior

Article abstract of DOI:10.1016/j.molstruc.2014.01.031

3β-Acetoxy-6-nitrocholest-5-ene (2) has been synthesized from 3β-acetoxycholest-5-ene (1). We provided an analysis of the compound by means of FT-IR, FT-Raman, NMR and X-ray crystallography. In addition microstructural, thermal, optical and dielectrical properties were also investigated. The compound 2 crystallizes in the monoclinic space group P2 ₁ with cell dimensions, a = 15.7729 (13) A?, b = 9.8933 (8) A?, c = 17.8070(14) A?, α = 90.00, β = 96.176(4), γ = 90.00. The powder X-ray diffraction (PXRD) of the compound was recorded to ascertain phase homogeneity. The SEM micrograph showed the presence of brick shaped, elongated nitrocholestane particles with 177.12 × 25.53 × 5.69 μm dimensions. Thermogravimetric analysis showed stability of the compound up to 200 C. The dielectrical studies showed that with increase in frequency, the dielectric constant decreases and becomes almost constant at high frequencies.

Full text of DOI:10.1016/j.molstruc.2014.01.031

Journal of Molecular Structure 1063 (2014) 219–225
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
3b-Acetoxy-6-nitrocholest-5-ene: Crystal structure, thermal, optical and
dielectrical behavior
Shamsuzzaman a, , Ashraf Mashrai a,1, Hena Khanam a,1, Yahia Nasser Mabkhot b, Wolfgang Frey c
⇑
a Steroid Research Laboratory, Department of Chemistry, Aligarh Muslim University, Aligarh 202002, UP, India
b Department of Chemistry, Faculty of Science, King Saud University, Riyadh 11451, Saudi Arabia
c Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, Stuttgart 70569, Germany
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
ꢀ
3b-Acetoxy-6-nitrocholest-5-ene has been synthesized from 3b-acetoxycholest-5-ene.
Structural assignment has been performed on the basis of FT-IR, FT-Raman, 1H NMR, 13C NMR, and X-ray crystallography.
Thermal, optical, microstructural and dielectrical properties have also been explored.
Thermal studies (TG–DTA–DSC) showed thermal stability and good crystalinity of the compound.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 July 2013
Received in revised form 8 January 2014
Accepted 8 January 2014
Available online 30 January 2014
3b-Acetoxy-6-nitrocholest-5-ene (2) has been synthesized from 3b-acetoxycholest-5-ene (1). We pro-
vided an analysis of the compound by means of FT-IR, FT-Raman, NMR and X-ray crystallography. In addi-
tion microstructural, thermal, optical and dielectrical properties were also investigated. The compound 2
crystallizes in the monoclinic space group P21 with cell dimensions, a = 15.7729 (13) Å, b = 9.8933 (8) Å,
c = 17.8070(14) Å,
pound was recorded to ascertain phase homogeneity. The SEM micrograph showed the presence of brick
m dimensions. Thermogravi-
a = 90.00, b = 96.176(4), c = 90.00. The powder X-ray diffraction (PXRD) of the com-
Keywords:
Steroid
X-ray
Thermal
Optical
shaped, elongated nitrocholestane particles with 177.12 ꢁ 25.53 ꢁ 5.69
l
metric analysis showed stability of the compound up to 200 °C. The dielectrical studies showed that with
increase in frequency, the dielectric constant decreases and becomes almost constant at high frequencies.
Ó 2014 Elsevier B.V. All rights reserved.
Dielectrical
1. Introduction
specific commercially important therapeutic agents [1–3]. More-
over steroids play an important biological role and have occupied
Steroids, a widespread class of natural organic compounds
occurring in animals, plants and fungi, have shown great therapeu-
tic value for a broad array of pathologies. They comprise a wide
repertoire of structurally related natural compounds with impor-
tant functions in vivo, such as physiological regulators, hormones,
and provitamins. Steroids are representative of a rich structural
molecular diversity and ability to interact with various biological
targets and pathways. For the last seventy years the chemistry of
steroids has provided one of the most interesting and thoroughly
explored areas for organic chemists. The synthetic modification
of naturally occurring steroids with the hope of improving phar-
macological essentials has resulted in the preparation and discov-
ery of a number of diverse pharmacologically active, potent, highly
a prominent position in medicinal chemistry field. Steroids have al-
ways attracted considerable interest because of their biological sig-
naling molecules. Many representatives of this group are widely
used in medicine as essentials of anti-inflammatory, diuretic, ana-
bolic, contraceptive, antiandrogenic, progestational, anticancer and
antimicrobial agents [4,5]. The steroidal drugs are widely used in
traditional medicines, such as antibacterium, hormone kind medi-
cation, etc. Some steroid compounds are known to exert hormone
receptor-independent antiproliferative activity via the inhibition of
angiogenesis, tubulin polymerization and the upregulation of
apoptotic pathways [6–8]. Cholesterol (Chol), a well known steroid,
is ubiquitous in all living systems. Cholesterol is located in all
membrane compartments at levels as high as 50-mole percent,
which renders it the most prominent lipid in eukaryotic cells [9].
Cholesterol, which is synthesized de novo and obtained from the
diet, largely affects the biophysical properties of cellular mem-
branes and functions in a variety of synthetic pathways, including
⇑
Corresponding author. Tel.: +91 9411003465.
E-mail address: shamsuzzaman9@gmail.com ( Shamsuzzaman).
1
These authors have contributed equally.
http://dx.doi.org/10.1016/j.molstruc.2014.01.031
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

220
Shamsuzzaman et al. / Journal of Molecular Structure 1063 (2014) 219–225
those of bile acids, hormones, and, through its precursor 7-dehy-
drocholesterol (7-DH-Chol), vitamin D synthesis [10]. Nitro com-
pounds are very important and widely used chemicals [11] due
to their versatile reactivities and simplicity to prepare. In particu-
lar, the nitro functionality can readily be introduced into a choles-
tane ring. The cholesteryl-nitro compound has been widely utilized
as an intermediate for the preparation of 6-ketocholestane. In view
of the aforementioned facts and in continuation of our programme
on the synthesis of steroids [12], the present article embodies the
spectroscopic and single crystal characterization of the 3b-acet-
oxy-6-nitrocholest-5-ene. In addition, dielectrical, thermal, mor-
phological and optical behavior of the compound has also been
explored.
pellet, cp = capacitance of the specimen in Farad (F). Thin layer
chromatography (TLC) plates were coated with silica gel G and ex-
posed to iodine vapors to check the homogeneity as well as the
progress of reaction. Sodium sulfate (anhydrous) was used as a
drying agent.
2.2. Synthesis of 3b-acetoxy-6-nitrocholest-5-ene (2)
To a cooled mixture of cholesteryl acetate 1 (10 g) and conc. ni-
tric acid (250 mL, d = 1.42) sodium nitrite (10 g) was gradually
added with constant stirring over a period of about 45 min. After
complete addition of sodium nitrite stirring was continued for
additional 2 h. Cold water (300 mL) was added to reaction mixture,
yellow solid material separated out. The whole mass was extracted
with ether. The ethereal layer was washed with water, NaHCO3
solution (5%) (until washings become pink), water and dried over
anhydrous sodium sulfate. Removal of the solvents provided the
nitro compound as oil which was crystallized from methanol to
provide colorless crystals suitable for X-ray diffraction (Scheme 1)
(yield: 6.5 g), m.p. 104 °C (reported m.p. 102–104 °C) [13]. Anal.
Calc. for C29H47NO4: C, 73.53; H, 10.00; N, 2.96 (%). Found: C,
73.50; H, 10.06; N, 2.90 (%); IR (KBr, cmꢂ1): 2944, 2869 (CAH,
stretching), 1746 (C@O), 1519, 1301 (NO2, stretching), 1464,
1365 (CAH, bending), 1237 (CAO); 1H NMR (CDCl3, 400 MHz): d
2. Experimental section
2.1. General comments
All reagents and solvents were commercially available and used
as received. Melting point was determined on a Kofler apparatus.
The IR spectrum was recorded on KBr pellets with Interspec 2020
FT-IR Spectrometer spectro Lab and values are given in cmꢂ1. FT-
Raman spectra were recorded on WITec alpha 300 scanning Near
Field Optical Microscope (SNOM), Germany. 1H and 13C NMR spec-
tra were run in CDCl3 on a Bruker Avance II 400 NMR Spectrometer
at 400 MHz and 100 MHz respectively. Chemical shifts (d) are re-
ported in ppm relative to the TMS (1H NMR, 400 MHz) and to the
solvent signal (13C NMR spectra, 100 MHz). Elemental analyses of
the compound were recorded on Perkin Elmer 2400 CHN Elemental
Analyzer. X-ray diffraction (PXRD) pattern of powdered sample
was recorded on MiniFlex™ II benchtop XRD system (Rigaku Cor-
4.72 (1H, m, C3a-H, W1/2 = 16 Hz, axial), 2.01 (3H, s, OCOCH3),
1.10 (3H, s, 10-CH3) 0.67 (3H, s, 13-CH3), 0.90 and 0.85 (other
methyl protons); 13C NMR (CDCl3, 100 MHz): d 170.1 (C@O),
150.2 (C-5), 148.1 (C-6), 72.1 (CAO), 56.2, 52.9, 49.3, 42.2, 41.1,
39.6, 39.2, 38.3, 38.1, 35.7, 34.7, 33.3, 32.7, 31.8, 30.1, 29.7, 28.7,
28.1, 27.9, 25.2, 23.2, 20.2, 19.2, 17.2, 12.1; MS (ESI): m/z 473.35
[M+.].
poration, Tokyo, Japan) operating at 40 kV and a current of
2.3. X-ray diffraction
0
30 mA with Cu Ka radiation (k = 1.54 ÅA). The diffracted intensities
were recorded from 20° to 80° 2h angles with scan rate of 2°/min
and a step size of 0.02°. XRD measurements were performed at
ambient temperature. The surface morphology of the compound
was monitored using JEOL JSM-6510LV scanning electron micro-
scope (SEM). Topographical images of the synthesized compound
were taken using AFM, with a uniform thin film in acetonitrile
on a 10 ꢁ 2.5 cm glass slide. To evaporate excess solvent, the slide
was kept in vacuum at room temperature for 24 h. The sample was
scanned using non-contact tapping mode and obtained 3D topo-
logical images. The thermal study of the compound was carried
out using TGA/DTA-60H and DSC-60 instrument (SHIMADZU) at
Three dimensional intensity data for the compound 2 were col-
lected at 100 K on Bruker KAPPA APEXII DUO diffractometer using
0
Cu Ka radiation (k = 1.54178 ÅA). The structure was solved by direct
methods using SHELXS-97 software (SHELDRICK, 1990). Isotropic
refinement of the structure by least-squares methods was carried
out by using SHELXL-97 (SHELDRICK, 1997) followed by aniso-
tropic refinement on F2 of all the non-hydrogen atoms. Crystallo-
graphic data (excluding structure factors) for the structures
reported in this article have been deposited with the Cambridge
Crystallographic Data Centre (CCDC) as deposition No. CCDC
896096. All H-atom positions were calculated geometrically with
0
a
heating rate of 20 °C minꢂ1 from ambient temperature to
Uiso (H) = 1.2–1.5 ÅA Ueq (parent atom). A riding model was used in
0
800 °C (for DSC 500 °C). UV–Vis spectrum was recorded on UV–
Vis spectrophotometer (Perkin Elmer Life and Analytical Sciences,
CT, USA) in the wavelength range of A200 to 700 nm. The fluores-
cence spectrum was collected at 37 °C with a 1 cm path length cell
using a Hitachi spectrofluorometer (Model 2500) equipped with a
PC and the emission slit were set at 5 nm. The emission spectrum
was recorded in the range of 300–400 nm. The CD spectra of the
crystal was collected a JASCOJ815 spectropolarimeter equipped
with a Peltier-type temperature controller at 37 °C. Spectra were
collected from 200 to 600 nm with 20 nm/min scan speed and a re-
sponse time of 2 s. Respective blanks were subtracted. The Dielec-
tric property was determined using impedance spectroscopy. The
powder was pressed into pellets of 13 mm diameter and
0.84 mm thickness. Dielectric spectroscopy measurement was car-
ried out in the frequency range 1 kHz to 1 MHz using LCR meter
(Agilent 48). The pellets were coated on adjacent faces with silver
paste, thereby forming parallel plate capacitor geometry. The value
of dielectric constant (e0) is calculated using the formula, as fol-
their refinement (CAH = 0.98–1.00 ÅA).
3. Results and discussion
The experimental procedure followed in this manuscript [13] is
almost similar to that reported by A.T. Rowland [11]. Here conc. ni-
tric acid and sodium nitrite were taken without any other solvent
while A.T. Rowland had used conc. nitric acid and potassium nitrite
with ether as solvent.
HNO3 / Sodium nitrite
stirring/cold conditions
O
O
O
O
NO2
(1)
(2)
lows: e0= cp d/eo A, Where,
ness of pellet, A = cross sectional area of the flat surface of the
eo = permittivity of free space, d = thick-
Scheme 1. Synthesis of 3b-acetoxy-6-nitrocholest-5-ene.

Shamsuzzaman et al. / Journal of Molecular Structure 1063 (2014) 219–225
221
3.1. FT-IR/Raman spectroscopy
1365 and 1464 cmꢂ1, corresponded to CAH bending mode of
vibrations, whereby CAH stretching vibrations were detected at
2944–2869 cmꢂ1. The Raman spectrum of compound 2 in the
1250–3500 cmꢂ1 spectral range is illustrated in Fig. S2. The spectrum
demonstrated the position and relative intensity of the Raman bands.
The spectrum displayed a strong band at 2750–3000 cmꢂ1, attributed
to the stretching vibrations of the CAH units. A sharp medium peak
around 1730 cmꢂ1 was assigned to C@O stretching vibrations.
The infrared spectral analysis provides useful information
regarding the molecular structure of the compound. IR spectrum
of compound 2 (Fig. S1) showed strong peaks at 1746 and
1234 cmꢂ1 ascribed to C@O and CAO stretching vibrations respec-
tively. The characteristic peaks observed at 1301and 1519 cmꢂ1
,
were assigned to
m (NO2) stretching vibrations. The peaks at
(a)
(b)
(c)
Fig. 1. 3b-Acetoxy-6-nitrocholest-5-ene (2): (a) a perspective view ellipsoid (50% Probability), (b) three-dimensional view along the c axis and (c) three-dimensional view
along b axis.

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Shamsuzzaman et al. / Journal of Molecular Structure 1063 (2014) 219–225
Table 2
3.2. NMR spectroscopy
Selected bond lengths (Å) and angles (deg) for compound
2.
NMR spectroscopy plays a vital role in the structural confirma-
tion of the grown material. The NMR spectra (Figs. S3 and S4) of ti-
tle compound showed a multiplet at d 4.72 in 1H NMR which was
Bond length
O3BAC4B
C4BAC5B
C3BAC4B
C1BAC2B
N1BAC1B
O1BAN1B
N1BAO2B
C1BAC17B
1.456(2)
1.509(3)
1.518(3)
1.335(3)
1.481(3)
1.223(2)
1.225(3)
1.484(3)
attributed to C3a-proton while three acetoxy protons appeared as
a sharp singlet at d 2.01. The half band width (W1/2) value of C3-ax-
ial proton surely characterizes the junction of A/B ring as trans [4].
The characteristic peaks in 13C NMR spectrum were obtained at d
170.1 (C@O) and 72.1 (CAO). The chemical shift value of C-19 as
d 17.2 further conforms the nature of the ring junction [1].
Bond angle
O1B N1B O2B
O1B N1B C1B
O2B N1B C1B
C2B C1B N1B
O3B C4B C5B
C5B C4B C3B
C1B C2B C3B
N1B C1B C17B
124.25(19)
116.76(18)
118.95(19)
118.97(18)
108.27(17)
110.96(18)
122.98(19)
112.10(16)
3.3. Description of crystal structure
The title compound 2 crystallizes in the monoclinic system,
space group P21 which can be explained by the presence of 8 chiral
centers [14]. There are two molecules in the asymmetric unit,
while unit cell contains 4 molecules (Figs. 1, S5 (a and b)) with
the lattice constants of a = 15.7729 (13) Å, b = 9.8933 (8) Å,
c = 17.8070(14) Å, and the detailed data are listed in Tables 1 and
2. The solvent molecule was not located in discrete locations in
the crystal structure. Rings A and C exist in the chair conformation.
Ring B adopts a half-chair conformation, and ring D is 11b enve-
lope. The A/B ring junction is quasi-trans, while the B/C and C/D
ring systems are trans fused about the C(8)AC(16) and
changes in the bond distance and bond angle. The bond distances
and bond angle in compound 2 are found to be C3AC4 = 1.518
0
(3) Å, C4AC5 = 1.509 (3) ÅA and C3AC4AC5 = 110.96 (18). The ob-
served bond distances are shorter than the standard value of
C(sp3)AC(sp3) bond [15]. The bond angles show some deviation
from the average value of sp3-type hybridization [16]. Side-chain
is fully extended with a gauche-trans conformation of the terminal
C28 and C29 methyl groups. There are eight chiral centres in the
molecule, the absolute configuration of these sites were deter-
mined from the structure presented, these sites exhibit the follow-
ing chiralities: C4 = S, C7 = R, C8 = S, C11 = R, C12 = R, C15 = S,
C16 = S and C22 = R.
C(11)AC(15) bonds, respectively. Ring bond lengths have normal
0
values with an average of 1.528 (3) ÅA, while the cholestane side
0
chain shows an average bond length of 1.521 (3) ÅA. The bond
0
length C(1)AC(2) is 1.335 (3) ÅA, which indicates a double-bond
character. The distance between acetoxy group and C4 is 1.456
0
(2) ÅA which is slightly longer than the average values reported
[15]. The acetoxy group at position-4 is equatorial and antiperipla-
3.4. Powder XRD
nar to the C5AC6 bond with a torsion angle 178.45ꢀ and the
0
The powder form of the grown crystal (2) was subjected to
powder X-ray diffraction analysis. The appearances of sharp and
strong peaks confirmed the good crystallinity of the grown crystals
(Fig. 2). The lattice parameters of crystals were calculated using the
powder XRD data and were found in good agreement with the val-
ues obtained from single crystals.
C1ANO2 bond is 1.481(3) ÅA and the NO2 group involved in two
0
non covalent bonding (O2Aꢃ ꢃ ꢃH10D, O1Aꢃ ꢃ ꢃH15A ÅA) (Fig. S5(c)).
The substitution at ring-A of the steroid nucleus causes significant
Table 1
Crystal data and structure refinement for crystal 2.
Empirical formula
Formula weight
Wavelength (k)
C29H47NO4
3.5. Microstructral studies (SEM/AFM)
473.68
0
1.54178 ÅA
Monoclinic
P21
3.5.1. Scanning electron microscopy
Crystal system
Space group
The surface morphology of the compound 2 was investigated by
scanning electron microscopy (SEM). The SEM micrograph (Fig. S6)
clearly showed the presence of brick shaped, elongated
Unit cell dimensions
0
15.7729(13)
9.8933(8)
a (AÅ)
0
b (ÅA)
0
17.8070(14)
c (AÅ)
a
(deg)
90.00
b (deg)
(deg)
Volume (AÅ3)
96.176(4)
90.00
2762.6(4)
c
0
No. of molecules per unit cell (Z)
4
Calculated density, Mg mꢂ3
1.139
0.583
1040
Absorption coefficient (
F(000)
l
, mmꢂ1
)
Crystal size
h range for data collection
Limiting indices
Reflections collected
Restraints/parameters
Goodness-of-fit on F2
0.27 ꢁ 0.20 ꢁ 0.09 mm
2.50–66.59
ꢂ18 6 h 6 18, ꢂ11 6 k 6 9, ꢂ20 6 l 6 20
8175
1/625
1.033
Final R indices [I > 2
R indices (all data)
r(I)]
R1 = 0.0386, wR2 = 0.0994
R1 = 0.0439, wR2 = 0.1015
1=2
P
P
P
P
2
2
R1
¼
kFoj ꢂ jFck= jFoj with F2o > 2
r
ðF2oÞ. wR2 ¼ ½ wðjFo2j ꢂ jFc2jÞ = jF2oj ꢄ
.
Fig. 2. Powder XRD of 3b-acetoxy-6-nitrocholest-5-ene (2).

Shamsuzzaman et al. / Journal of Molecular Structure 1063 (2014) 219–225
223
nitrocholestane particles, extending over 177.12
with few micro crystals on it.
l
m in length,
any phase transition. After 200 °C it started decomposition and
43.68% weight loss occurred at 260 °C and at 507 °C temperature
57.14% mass is lost. The disintegration process continued with
the confiscation of almost all fragments as gaseous products, lead-
ing to the bulk decomposition of the compound before 700 °C since
the initial mass of the sample was 5.308 mg and at a temperature
of about 700 °C, all the mass was lost and nothing was left as res-
idue. The absence of any weight loss or phase transition around or
before its melting point, confirmed the nonexistence of any lattice
entrapped solvent or moisture on the grown material as well as
high stability of the steroidal nitro compound. The corresponding
DTA curve showed three notable thermal events. The endothermic
peak at 106 °C showed melting of the compound. The exothermic
peaks at 306 °C and 600 °C depicted the crystallization of some
of the phases of the decomposed material. From DSC (Differential
scanning calorimetry) curve the melting point in the present inves-
tigation was found to be 102–104 °C.
3.5.2. Atomic force microscopy
The vertical and horizontal line analysis of images for the syn-
thesized compound showed roughness parameters such as mini-
mum and maximum surface value (Figs. S7 and S8). The mean
value of the surface relative to the centre plane Mean roughness
(Ra) value was found to be 12.23 nm. The other roughness param-
eters like mid-value (average of maximum and minimum), mean,
peak to valley of the line (Rpv, difference between minimum and
maximum), root-mean-squared roughness, ten point average
roughness area (Rz, is the arithmetic average of the five highest
and five lowest valleys peaks in the line calculated by ten point
average), skewness (Rsk) and kurtosis (Rku) values of line are given
in Table 3.
3.6. Thermal analysis (TG/DTA–DSC)
3.7. Optical properties (Absorption spectra/fluorescence spectra/
circular dichroism)
Thermogravimetric/differential thermal analysis/differential
scanning calorimetry) (TG/DTA/DSC) measurements were per-
formed under nitrogen atmosphere to examine the thermal stabil-
ities of the crystalline sample and to define the conditions for the
thermal treatment on it. Melting of the grown crystals had been
estimated by differential thermal analysis (DSC). The thermograms
observed from simultaneous TGA (Fig. 3) and DTA/DSC are illus-
trated in Figs. S9 and S10. The TG curve of compound 2 revealed
that it is stable up to 200 °C (no weight loss) and does not undergo
To determine the transmission range and to know the suitabil-
ity of the crystals for optical applications, The UV–Vis absorption
properties of compound 2 were recorded in dichloromethane solu-
tion with the concentration of 10ꢂ5 M. The absorption spectrum
(Fig. 4) exhibited a strong, featureless absorption band around
265 nm, which can be assigned to an allowed
of the conjugated nitro-group with C@C double bond. Fluorescence
p ?
pꢅ transition
Table 3
AFM topographical mean surface parameters (nm) for compound 2.
Line
Min.
Max.
Mid
Mean
Rpv
Rq
Ra
Rz
Rsk
Rku
Horizontal
Vertical
ꢂ23.64
ꢂ14.52
18.13
14.21
ꢂ4.14
ꢂ2.20
0.00
0.00
42.70
27.60
12.50
5.90
10.59
5.18
24.50
24.15
0.30
0.76
2.01
3.37
Fig. 3. TGA of 3b-acetoxy-6-nitrocholest-5-ene (2).

224
Shamsuzzaman et al. / Journal of Molecular Structure 1063 (2014) 219–225
compound has no influence [17]. The conjugation of the nitro-
group with a C@C double bond gives rise to intense ultraviolet
absorption at about 266 nm, which has been classified as a
charge-transfer band. The other band at 335 nm due to (n ? pꢅ
)
showed pronounced bathochromic shifts due to conjugation and
no long wavelength band is detectable. The high circular dichroism
is due to inherent dissymmetry of the chromophore (Fig. 6).
3.8. Dielectrical properties
The dielectric properties of the crystal was measured as a func-
tion of frequency at room temperature by equation e⁄
=
e0 ꢂ ie00
where, e0 is real part of dielectric constant and describes the stored
energy while e00 is the imaginary part of the dielectric constant,
which describes the dissipated energy. The dielectric constant is
shown in Fig. S11. It is shown that with the increase in frequency,
the dielectric constant decreases and becomes almost constant at
high frequencies. This behavior can be explained using Maxwell–
Wagner interfacial model. According to this model, a dielectric
medium is considered to be composed of double layers, well con-
ducting grains which are separated by poorly conducting or resis-
tive grain boundaries. Under the application of external electric
field, the charge carriers can easily migrate the grains but are accu-
mulated at the grain boundaries. This process can produce large
polarization and high dielectric constant. The higher value of
dielectric constant can also be explained on the basis of interfa-
cial/space charge polarization due to non-homogeneous dielectric
structure.
Fig. 4. UV–Vis spectrum of 3b-acetoxy-6-nitrocholest-5-ene (2).
4. Conclusion
3b-Acetoxy-6-nitrocholest-5-ene derived from corresponding
cholest-5-ene has been characterized by spectral techniques. The
lattice parameters have been determined by single-crystal X-ray
diffraction analysis, which confirmed the identity of the synthe-
sized material. The powder X-ray diffraction pattern (PXRD) of
compound is equivalent to those simulated from single-crystal X-
ray data. Thermal studies established that the compound under-
goes no phase transition and is stable up to 200 °C. CD spectra
showed intense ultraviolet absorption at about 266 nm, which
has been classified as a charge-transfer band. The other band at
335 nm due to (n ? pꢅ) showed pronounced bathochromic shifts
due to conjugation.
Fig. 5. Fluorescence spectrum of 3b-acetoxy-6-nitrocholest-5-ene (2).
Acknowledgements
The authors would like to thank the Chairman, Department of
Chemistry, Aligarh Muslim University, Aligarh for providing
necessary research facilities. HK acknowledges UGC, New Delhi,
India for providing BSR fellowship (R.No. Acad/D-742/MR). YNM
thanks the Deanship of Scientific Research at King Saud University
for the support (P.No. RGP-VPP-007). We are also thankful to
Dr. Motohiro Nishio (The CHPI Institute, Japan) for his valuable
discussion.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.molstruc.2014.
01.031.
Fig. 6. CD of 3b-acetoxy-6-nitrocholest-5-ene (2).
References
image (Fig. 5) of the compound showed one sharp peak at 360 nm
and another broad peak at 475 nm. The nitro-group is a chromo-
phore which exhibits a Cotton effect while 3b-acetoxy-group of
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