Electrical and dielectric properties of charge transfer complexes: Interactions between norfloxacin and ciprofloxacin with picric acid and 3,5-dinitrobenzoic acid

Article abstract of DOI:10.1134/S1070363213120372

Semiconductor behavior was observed for all three studied complexes. The dielectric constant for [(Nor)(PA)], [(Cip)(PA)], and [(Nor)(DNB)] seems to be frequency independent at high frequency, that may be attributed to low mobility of charge carriers whic

Full text of DOI:10.1134/S1070363213120372

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 12, pp. 2413–2418. © Pleiades Publishing, Ltd., 2013.
Electrical and Dielectric Properties of Charge Transfer
Complexes: Interactions between Norfloxacin
and Ciprofloxacin with Picric Acid
1
and 3,5-Dinitrobenzoic Acid
a,b
c
d
Moamen S. Refat , A. Elfalaky , and Eman Elesh
a
Department of Chemistry, Faculty of Science, Taif University, 888 Taif, Kingdom Saudi Arabia
e-mail: msrefat@yahoo.com
b
Department of Chemistry, Faculty of Science, Port Said University, Egypt
c
Department of Physics, Faculty of Science, Zagazig University, Egypt
d
Department of Physics, Faculty of Science, Port Said University, Egypt
Received September 9, 2013
Abstract―Semiconductor behavior was observed for all three studied complexes. The dielectric constant for
(Nor)(PA)], [(Cip)(PA)], and [(Nor)(DNB)] seems to be frequency independent at high frequency, that may be
[
attributed to low mobility of charge carriers which can not follow the applied field.
DOI: 10.1134/S1070363213120372
INTRODUCTION
O
N
F
CO H
Charge-transfer complexes are known to take part
in many chemical reactions like addition, substitution
2
and condensation [1, 2]. These complexes draw great
attention as non-linear optical materials and electrical
conductivities [3–6]. Drugs physical properties are also
significantly important parameters in such a way that
target the infected cells. Polymorphism has become a
very significant branch of study either for academic
research and pharmaceutical industries. Depending on
the crystal structure a drug has different bioavailability
and therapeutic effect on bacteria. In addition, the
electrostatic energies stored in a molecule play an
important role in the attraction or repulsion force
against the DNA molecule. Such electrostatic energy is
directly correlated with the dielectric constant.
N
HN
HO
C H
2
5
Norfloxacin (Nor)
O
O
F
N
N
NH
Ciprofloxacin (Cip)
EXPERIMENTAL
In this paper, we describe synthesis and studying of
electrical and dielectric properties of change transfer
complexes formed by two fluoroquinolone-class
antibiotics, Norfloxacin (Nor) and Ciprofloxacin (Cip)
All chemicals used throughout this work were
Analar or extra pure grade. Ciprofloxacin (Cip), was of
analytical reagent grade (Merck reagent). Stock
solutions of Ciprofloxacin or of picric acid were
freshly prepared and the spectroscopic grade methanol
was used as received.
[7–9].
Norfloxacin-(PA and DNB) complexes. Solid CT
1
complexes of Norfloxacin with picric acid (2,4,6-
The text was submitted by the authors in English.
2
413

2
414
MOAMEN S. REFAT et al.
(
b)
(
a)
–
1
1
/T, K
–1
1
/T, K
(
c)
–1
1
/T, K
Fig. 1. AC conductivity at different temperature T (K) and frequency at 2 MHz for: (a) I, (b) II, and (c) III complexes.
trinitrophenol, PA) and 3,5-dinitrobenzoic acid (DNB)
were prepared by mixing 1 mmol of the donor (Nor) in
methanol (10ml) with 1 mmol of each acceptor in the
same solvent with constant stirring for about 6 hrs.
Solutions were allowed to slowly evaporate at room
temperature, the solids precipitated were filtered off,
washed several times with little amounts of solvent and
dried under vacuum over anhydrous calcium chloride.
on pressed disk samples of over the same range of
temperature and frequency.
RESULTS AND DISCUSSION
AC conductivity as a function of temperature is
shown in Fig. 1 at constant field frequency equal to
1 MHz. It can be noticed that the conductivity tends to
increase slightly with increasing temperature. As
shown in Figs. 1a–1c no significant trend of AC
conductivity I, II, and III complexes was detected.
The AC conductivity of all three complexes show
semiconducting behavior. However, the activation
energy of each complex is bit differ than the other.
Table contains the activation energy values for the
corresponding complex.
[
(Nor)(PA)] (I) (yellow), C H FN O , M 548.40.
22 21 6 10 W
[
(Nor)(DNB)] (II) (buff), C H FN O , M 531.42.
23 22 5 9 W
[
(Cip)(PA)](III) (pale yellow solid), C H FN O ,
23 21 6 10
M 560.45.
W
Physical measurements. In this work AC
Conductivity (σ) of disk shaped samples were
measured, at room temperature from 323 to 583 K,
over wide range of frequencies from 50 up to 5MHz. It
is to mention that the measurements of dielectric
properties (dielectric constant ε') were also performed
The activation energy ∆E was calculated according
to equation:
−
ΔE/KBT
σ = σ e
(1)
T
0
,
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ELECTRICAL AND DIELECTRIC PROPERTIES OF CHARGE TRANSFER COMPLEXES
2415
(
a)
(a)
ln f, Hz
T , K
(
b)
(
b)
5
10
15
ln f, Hz
360
400
440
T , K
(
c)
(c)
ln f, Hz
T , K
Fig. 3. Variation of the exponent factors against tem-
perature for: (a) I, (b) II, and (c) III complexes.
Fig. 2. Frequency dependence of AC conductivity at T =
23 K for (a) I, (b) II, and (c) III complexes.
3
where σ is the conductivity at temperature T and σ is
preexponential factor.
complexes, two distinct regions can be observed.
Region 1, the low temperature region and the high
temperature region, region 2. Such regions can be
referred to many mechanisms. These mechanisms are
the decomposition of the complex, the transition from
the intrinsic semiconductor to an extrinsic semi-
conductor and phase change. For the frequency
T
0
In the above equation K represents Boltzmann
B
constant and T is the temperature in K. It can be
observed that the activation thermal energy ∆E of the
II is higher than that of I and III. In Fig. 1 for all three
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

2
416
MOAMEN S. REFAT et al.
(
a)
(a)
ln f, Hz
b)
ln f, Hz
(
(
b)
ln f, Hz
ln f, Hz
c)
(
(c)
ln f, Hz
ln f, Hz
Fig. 4. Frequency dependence of dielectric constant (ε') at
23 K for: (a) I, (b) II, and (c) III complexes.
Fig. 5. Frequency dependence of dielectric loss (ε'') at 323 K
for : (a) I, (b) II, and (c) III complexes.
3
dependence of AC conductivity of the three com-
plexes, an example for each complex at T = 323 K is
shown in Figs. 2a–2c, the AC conductivity tends to
increase slightly with increasing frequency. This can
also be attributed to the enhancement of the conduction
carriers by applied external field. The dispersion
shown in Figs. 2a–2c. According to this dispersion the
conductivity versus frequency verifies the following
expression [24].
σ(ω) = σdc + BωS,
(2)
where σ(ω) is the AC conductivity, ω is the angular
frequency which equals ω = 2πf, S is frequency
exponential factor and B is constant. The frequency
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 12 2013

ELECTRICAL AND DIELECTRIC PROPERTIES OF CHARGE TRANSFER COMPLEXES
2417
Activation energy, exponential factor and optical band gap
for [(Nor)(PA)], [(Cip)(PA)], and [(Nor)(DNB)] complexes
CONCLUSIONS
1) Semiconductor behavior was observed for all
(
three studied complexes.
∆
E
1
, eV
∆E
at low
tempature
2
, eV
Optical
band gap
w , eV
H
Comp.
no.
Exponential
factor S
at high
tempature
(2) Regarding the activation energy for the studied
complexes, the activation thermal energy ∆E of II is
higher than that for I and III.
I
0.03
0.29
0.68
0.58
0.700
0.780
0.713
0.55
0.76
0.58
(
3) In addition, the conduction mechanism in the
0
.08
three studied complexes is considered to be due to
correlation barrier hopping.
II
III
0.03
(
4) The dielectric constants of I, II, and III are
relatively high, of value about 250.
5) At low frequency, the dielectric constant of all
studied complexes tend to decrease sharply, may be
due to the polarization resulting from the
heterogeneous structure.
exponential factor, S, can be obtained by plotting ln σ(ω)
against ln ω along the dispersion region where a
straight line is produced. From the slope of the
obtained straight line, S has been obtained. Since the
value of S decreases with the increasing of temperature
as shown in Figs. 3a–3c, the conduction mechanism is
considered to be due to correlation barrier hopping.
According to this model S can be written as Eq. (3)
(
(
6) The dielectric constant of I, II, and III seem to
be frequency independent at high frequency, that may
be attributed to low mobility of charge carriers which
can not follow the applied field.
[25]
(
7) It is noticed that the dielectric loss of all three
S = 1 – (6K T/w
B H
),
(3)
complexes is continuously decreasing with frequency
in the range of studied frequency.
where w is barrier height substitution for K , T, and S,
H
B
w was calculated for each complex and recorded in
the table.
H
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