Synthesis and characterization of highly conductive charge-transfer complexes using positron annihilation spectroscopy

Article abstract of DOI:10.1016/j.saa.2012.04.024

Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid (Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl₄), iodine, bromine, and zinc chloride (ZnCl₂) have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihilation lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors π-acceptors (Pi-OH and QL), σ-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl₄ and ZnCl₂) were covered. The results of elemental analysis indicated that the CT complexes were formed with ratios 1:1 and 1:2 for QL, SnCl₄, and ZnCl₂ acceptors and iodine, Pi-OH, and Br₂ acceptors, respectively. The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behavior of both items. The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, and the power of acceptors. The correlation between these parameters and the molecular weight and biological activities of studied complexes was also observed. Regarding the electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal (Aspergillus flavus and Candida albicans) activities.

Full text of DOI:10.1016/j.saa.2012.04.024

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and characterization of highly conductive charge-transfer complexes
using positron annihilation spectroscopy
Abdel Majid A. Adam , Moamen S. Refat a,b, T. Sharshar c,d, Z.K. Heiba d,e
a,
⇑
a
Department of Chemistry, Faculty of Science, Taif University, Al-Hawiah, P.O. Box 888, Zip Code 21974 Taif, Saudi Arabia
Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
Department of Physics, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh, Egypt
Department of Physics, Faculty of Science, Taif University, Al-Hawiah, P.O. Box 888, Zip Code 21974 Taif, Saudi Arabia
b
c
d
e
Department of Physics, Faculty of Science, Ain Shams University, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Molecular charge-transfer complexes of the tetramethylethylenediamine (TMEDA) with picric acid
Received 12 December 2011
Received in revised form 20 March 2012
Accepted 7 April 2012
4 2
(Pi-OH), benzene-1,4-diol (QL), tin(IV) tetrachloride (SnCl ), iodine, bromine, and zinc chloride (ZnCl )
have been synthesized and investigated by elemental and thermal analysis, electronic, infrared, Raman
and proton-NMR, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and positron annihila-
tion lifetime spectroscopy, and scanning electron microscopy. In this work, three types of acceptors
Available online 23 April 2012
p
-acceptors (Pi-OH and QL),
ZnCl ) were covered. The results of elemental analysis indicated that the CT complexes were formed with
ratios 1:1 and 1:2 for QL, SnCl , and ZnCl acceptors and iodine, Pi-OH, and Br acceptors, respectively.
4
r-acceptors (iodine and bromine), and vacant orbital acceptors (SnCl and
Keywords:
Tetramethylethylenediamine (TMEDA)
2
4
2
2
p-Acceptors
The type of chelating between the TMEDA donor and the mentioned acceptors depends upon the behav-
ior of both items. The positron annihilation lifetime parameters were found to be dependent on the struc-
ture, electronic configuration, and the power of acceptors. The correlation between these parameters and
the molecular weight and biological activities of studied complexes was also observed. Regarding the
electrical properties, the AC conductivity and the dielectric coefficients were measured as a function of
frequency at room temperature. The TMEDA charge-transfer complexes were screened against antibac-
terial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and antifungal
r
-Acceptors
Vacant orbital acceptors
Electronic spectra
Positron annihilation lifetime spectroscopy
(
Aspergillus flavus and Candida albicans) activities.
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
that have been used to study the structural aspects of different
types of materials even at subatomic levels. When a positron is
2
2
The charge-transfer (CT) complexes are known to take part in
many chemical reactions such as addition, substitution, and con-
densation [1,2]. These complexes have had great attention for non-
linear optical materials and electrical conductivity [3–6]. The
electron donor–acceptor (EDA) interaction is also important in
the field of drug receptor binding mechanisms [7], in solar energy
storage [8], and in surface chemistry [9] as well as in many
biological fields [10]. On the other hand, the EDA reactions of cer-
emitted from a Na source and allowed to penetrate the materials,
it thermalizes and diffuses to a depth of a few hundred microme-
ters. The positron either delocalizes or traps in defects, which leads
to an increase in its lifetime, or extracts an electron from the sur-
rounding material to form a positronium atom (Ps) with two states,
a singlet state (para-Ps, p-Ps) and a triplet state (ortho-Ps, o-Ps). In
both cases, the positron will eventually annihilate with an electron
and will have a corresponding lifetime for each state at annihila-
tion site. Each lifetime component has a corresponding intensity
tain
analysis [11]. For these wide applications extensive studies on CT
complexes of -acceptors have been performed [12]. Various spec-
p-acceptors have been successfully utilized in pharmaceutical
(I
lifetime (
and molecular solids (
i
) relating to the number of annihilations occurring at a particular
). The measured parameters of the Ps formation in ionic
and I) depend on the physical and chemical
p
s
i
troscopic techniques were used to characterize these metallic com-
plexes. Recently, positron annihilation spectroscopy has also been
applied to metallic complexes [13–15]. Positron annihilation life-
time (PAL) spectroscopy is one of the highly successful techniques
s
properties of the solids [16,17]. The previous studies show that the
Ps is preferentially formed in compounds exhibiting negative
charge stabilization at specific sites. These studies also show that
the parameters of positron annihilation are sensitive to the liability
of the solids to charge-transfer processes and it mainly depends on
the nature of the central metal ion [14]. Also, the correlation
⇑
Corresponding author. Tel.: +966 502099808.
E-mail address: majidadam@yahoo.com (A.M.A. Adam).
1
386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.04.024

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
459
between positron annihilation parameters and the structure of the
metallic complexes was observed [14].
X ‘Pert PRO PANanalytical X-ray powder diffraction, target copper
with secondary monochromate.
The present paper is concerned with the synthesis of the solid
CT complexes of tetramethylethylenediamine (TMEDA) (Formula
The PAL measurements were carried out using a fast–fast coin-
cidence spectrometer [18]. This PAL spectrometer consists of two
Bicron BC-418 plastic scintillation detectors and Ortec modules,
two 583 constant fraction differential discriminators (CFDD),
DB643 delay box (ns D), 414A fast coincidence, and 566 time-to-
amplitude converter (TAC). The data were acquired using an Ortec
919 multichannel analyzer (MCA). A positron source was prepared
1
4 2
6) as a donor and Pi-OH, QL, SnCl , iodine, bromine and ZnCl as
acceptors. The solid complexes resulted are investigated by spec-
tral, thermal and electrical methods. These tools are enough to de-
tect and characterize the behavior of interaction and the nature of
the chelating in these complexes.
2
2
using a droplet of NaCl solution dried onto two identical Kapton
foils (7.5 m thick), which were afterward glued by epoxy glue.
l
Experimental methods
This source was sandwiched between two identical samples. The
lifetime spectra were measured in air at room temperature. More
than one million counts were accumulated for each spectrum,
and each sample was measured three times. The time resolution
Materials
0
0
60
22
All chemicals (N,N,N ,N -tetramethyl-ethane-1,2-diamine, Pi-OH,
QL, SnCl , ZnCl , iodine, and bromine) were of reagent grade, were
of the spectrometer, measured with Co source at Na energy
window settings, was ꢂ300 ps (full-width at half maximum). The
positron annihilation lifetime is measured experimentally as the
4
2
purchased from Aldrich and Fluka Companies, and were used
without further purification.
time interval between the 1274.5 keV
c
ray emitted by the 22Na
radioisotope and one of the annihilation radiations.
The resulting lifetime spectra were analyzed using a computer
program LT [19] with a suitable correction for positrons annihi-
lated in the Kapton. The lifetime spectra of studied samples decom-
posed into two components. All these components were
determined with the best-fitting parameter ranging from 1.00 to
Synthesis of TMEDA CT complexes
The colored TMEDA CT complexes in solid form with Pi-OH, QL,
SnCl
ing 1 mmol of the TMEDA as a donor in pure-grade methanol
25 mL) for all complexes except for (iodine and bromine in chlo-
4 2
, ZnCl , iodine, and bromine acceptors were prepared by mix-
1
.2. The range of the experimental errors for the PAL parameters
, I , and I , determined over multiple measurements, were
(
s
1
,
s
2
1
2
roform) with 1 mmol of each acceptor. The mixtures were stirred
at room temperature for 30 min, and after that, the solid com-
plexes were precipitated separated, and washed with chloroform.
The synthesized CT complexes were dried under vacuum over
found to be <2 ps,<15 ps, 1%, and 0.5%, respectively. The mean life-
time of positron was calculated using the following relation:
s
1
I
1
þ
2 2
s I
2
s
m
¼
:
ð1Þ
anhydrous CaCl
2
.
I þ I
1
AC conductivity for disk shaped was measured, at room temper-
ature, over frequency range from 200 up to 100 kHz. The AC con-
ductivity and the dielectric constant have been measured by the
complex impedance technique using a lock-in amplifier (Model
SR 510 Stanford Research Systems).
Spectral, thermal, and electrical measurements
The elemental analyses of carbon, hydrogen, and nitrogen con-
tents were performed by the microanalysis unit at Cairo University,
Egypt, using a Perkin Elmer CHN 2400 (USA). The molar conductiv-
ities of freshly prepared 1.0 ꢀ 10 mol/cm3 dimethylsulfoxide
ꢁ3
Biological studies
(
DMSO) solutions were measured for the soluble CT complexes
using Jenway 4010 conductivity meter. The electronic absorption
spectra of the TMEDA donor and the acceptors (Pi-OH, QL, SnCl
ZnCl , iodine, and bromine) and the resulted CT complexes were
Antimicrobial activity of the tested samples was determined
using a modified Kirby–Bauer disk diffusion method [20]. Briefly,
100 ll of the best bacteria/fungi was grown in 10 mL of fresh media
4
,
2
recorded in methanol or chloroform solvents within 800–200 nm
range using a Perkin-Elmer Precisely Lambda 25 UV/Vis double
beam spectrometer fitted with a quartz cell of 1.0 cm path length.
The infrared spectra with KBr disks were recorded on a Bruker
until they reached a count of approximately 108 and 105 cells/mL
for bacteria and fungi, respectively [21]. Hundred microliters of
microbial suspension was spread onto agar plates corresponding
to the broth in which they were maintained. Isolated colonies of
each organism that might be playing a pathogenic role should
be selected from primary agar plates and tested for susceptibility
by disk diffusion method [22,23].
ꢁ1
FT-IR Spectrophotometer (4000–400 cm ). Raman laser spectra
of samples were measured on the Bruker FT-Raman with 50 mW
1
of laser at Taif University, Kingdom Saudi Arabia. The H-NMR
(
200 MHz) spectra were recorded on Varian Gemini spectropho-
Of the many media available, National Committee for Clinical
Laboratory Standards (NCCLS) recommends Mueller–Hinton agar
because it results in good batch-to-batch reproducibility. Disk dif-
fusion method for filamentous fungi tested by using approved
standard method (M38-A) developed by the NCCLS [24] for evalu-
ating the susceptibility of filamentous fungi to antifungal agents.
Disk diffusion method for yeast developed standard method
tometers. The thermal studies TG/DTG–50H were carried out on
a Shimadzu thermogravimetric analyzer under static air till
8
Dispersive X-ray Detection (EDX) were taken in Joel JSM-6390
equipment, with an accelerating voltage of 20 kV. The X-ray dif-
fraction patterns for the selected CT complexes were recorded on
00 °C. Scanning electron microscopy (SEM) images and Energy-
(
M44-P) by the NCCLS [25]. Plates inoculated with filamentous
fungi such as Aspergillus flavus at 25 °C for 48 h; Gram (+) bacteria
such as Staphylococcus aureus, Bacillus subtilis; Gram (-) bacteria
such as Escherichia coli, Pseudomonas aeruginosa were incubated
at 35–37 °C for 24–48 h, and yeast such as Candida albicans was
incubated at 30 °C for 24–48 h, and then the diameters of the
inhabitation zones were measured in millimeters [20]. Standard
disks of tetracycline (Antibacterial agent), Amphotericin B (Anti-
fungal agent) served as positive controls for antimicrobial activity,
CH3
H C
N
3
N
CH3
CH3
0
0
Formula. 16. Structure of N,N,N ,N -tetramethyl-ethane-1,2-diamine (TMEDA).

4
60
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
but filter disk impregnated with 10
chloroform, DMSO) were used as a negative control.
l
L of solvent (distilled water,
0.50, 0.75, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, or 4.00 mL volumes of
ꢁ4
a standard solution (5.0 ꢀ 10 M) of the appropriate acceptor
The agar used is Meuller–Hinton agar that is rigorously tested
for composition and pH. Further, the depth of the agar in the plate
is a factor to be considered in the disk diffusion method. This meth-
od is well documented, and standard zones of inhabitation have
been determined for susceptible values. Blank paper disks (Schlei-
cher & Schuell, Spain) with a diameter of 8.0 mm were impreg-
(Pi-OH, QL, iodine and bromine) in methanol or chloroform was
ꢁ
4
added to 1.00 mL of 5.0 ꢀ 10 M TMEDA in chloroform or metha-
nol. The total volume of the mixture was made up to 5 mL. The
o
concentration of TMEDA (C ) in the reaction mixture was thus
d
ꢁ4
o
a
fixed at 1.0 ꢀ 10 M while the concentration of
p
-acceptors (C )
ꢁ
4
varied from 0.25 to 4.00 ꢀ 10 M. These concentrations produce
donor:acceptor ratios from 4:1 to 1:4. The absorbance of each CT
complexes was measured and plotted as a function with the ratio
nated with 10 lL of tested concentration of the stock solutions.
When a filter paper disk impregnated with a tested chemical is
placed on agar, the chemical will diffuse from the disk into the
agar. This diffusion will place the chemical in the agar only around
the disk. The solubility of the chemical and its molecular size will
determine the size of the area of chemical infiltration around the
disk. If an organism is placed on the agar, it will not grow in the
area around the disk if it is susceptible to the chemical. This area
of no growth around the disk is known as a ‘‘Zone of inhibition’’
or ‘‘Clear zone.’’ For the disk diffusion, the zone diameters were
measured with slipping calipers of the National for Clinical Labora-
tory Standers [22]. Agar-based methods such as Etest disk diffusion
can be good alternatives because they are simpler and faster than
broth methods [26,27].
o
d
o
d
of (C ):(C ) according to a known method [28]. It was of interest
to observe that the solvent has a pronounced effect on the spectral
intensities of the formed charge-transfer complexes. To study this
solvent effect in a quantitative manner, it was necessary to calcu-
late the values of the equilibrium constant, K, the molar absorptiv-
ity, e, and the oscillator strength, f, of the TMEDA complexes in the
respective solvent.
The 1:1 modified Benesi–Hildebrand Eq. (2) [29] was used in
the calculations of the TMEDA with QL charge-transfer complex,
o
a
o
d
o
a
o
d
C C l
1
e
C þ C
¼ K
þ
:
ð2Þ
A
e
o
o
where Ca and Cd are the initial concentrations of the acceptor (QL)
and the donor TMEDA, respectively, and A is the absorbance of
Results and Discussion
o
a
o
d
the strong bands at 294 nm for QL. When the C :C /A, values for
each 1:1 charge-transfer complex are plotted against the corre-
The analytical data (color, molar ratio elemental analysis) are
shown in Table 1. The elemental analysis data (C and H) of the re-
sulted CT complexes were matched with the molar ratio gained
from spectrophotometric titrations. The Pi-OH, QL, iodine, and bro-
mine CT complexes have a yellow, light brown, reddish brown, and
o
o
sponding C þ C values. Straight lines are obtained with a slope
a
d
of 1/e and intercept of 1/Ke.
The spectrophotometric titrations of the intermolecular charge-
transfer complexes formed from the reactions of TMEDA with Pi-
OH, iodine, and bromine acceptors refereed to formation of 1:2
CT complexes. The 1:2 Eq. (3) [30] was used in the calculations.
orange yellow colors, respectively, but SnCl
4 2
and ZnCl complexes
are white with powder fashion. Molar conductance of all the CT
ꢁ3
complexes in DMSO solvent at 10 M concentrations were ob-
o2
o
D
-1
2
ꢁ1
CA
C
1
1
e
o
A
o
D
o
A
tained in the range 48–90
X
cm mol and the results indicated
¼ K
þ
:C ð4C þ C Þ:
ð3Þ
A
e
them to be electrolytes. These results establish the stoichiometry
of these complexes, which are in agreement with the general for-
mulas suggested.
o2
o
D
where CA and C are the initial concentration of the Pi-OH, iodine,
and bromine acceptor and donor (TMEDA), respectively, and A is the
2
o
o
absorbance of the detected CT band. The data obtained C , C
,
D
A
2
o
o
o
o
o
Electronic and photometric analyses
C ð4C þ C Þ, and (C :C )/A in methanol were calculated. By plot-
A
D
A
A
D
2
o o o o o
ting (C :C )/A values versus C ð4C þ C Þ, straight lines were ob-
A
D
A
D
A
Photometric titrations of the detectable charge-transfer bands
at 410, 294, 360, and 279 nm were performed for the reactions of
TMEDA with Pi-OH, QL, iodine, and bromine as follows: 0.25,
tained with a slope of 1/
e and an intercept of 1/Ke.
The spectroscopic and physical data such as formation constant
o
(KCT), molar extinction coefficient (eCT), standard free energy (DG ),
Table 1
4 2 2 2
Analytical and physical data for Pi-OH, QL, SnCl , I , Br , and ZnCl charge-transfer complexes.
ꢁ
1
cm2 molꢁ1
)
Compound molecular formula empirical formula Color
Molar ratio Elemental analysis (%) found
(Calcd.)
K
m (X
(
[
MW.)
C
H
(TMEDA)(Pi-OH)
2
]
Yellow
1:2
1:1
1:1
37.42
(37.60)
3.33
(3.83)
65
48
90
72
55
88
C
5
18
H
22
N
8
O
14
74.44 g/mol
[
C
2
(TMEDA)(QL)]
Light brown
White
63.49
(63.62)
9.89
(9.72)
12
H
22
N
2
O
2
26.35 g/mol
[(TMEDA)(SnCl
4
)]
19.35
4.33
C
H
6 16
N
2
SnCl
4
(19.11)
(4.25)
376.74 g/mol
[
C
6
(TMEDA)]IꢃI
3
Reddish brown 1:1
11.44
2.52
6
H
16
N
2
IꢃI
3
(11.54)
(2.56)
23.60 g/mol
[
C
4
(TMEDA)]ꢃ2Br
2
Orange yellow
White
1:2
1:1
16.92
(16.52)
4.02
(3.67)
6
H
16
N
2
ꢃ2Br
2
35.84 g/mol
[(TMEDA)(ZnCl
2
)]
28.26
5.84
C
6
H
16
N
2
ꢃZnCl
2
(28.51)
(6.33)
252.56 g/mol

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
461
Table 2
Spectrophotometric results of the TMEDA CT complexes for Pi-OH(A), QL(B), I
2
(C), and Br
2
(D).
K (l.molꢁ1)
e
max (l.mol .cm
ꢁ1
ꢁ1
)
f
l
I
D
R
DG (25 °C) KJ mol
o
ꢁ1
Complex
kmax (nm)
ECT (eV)
p
N
7
A
B
C
D
410
294
360
279
4.26
4.05
4.35
4.35
8.48 ꢀ 10
70102
10661
46694
30211
60.55
6.14
40.33
21.75
61.30
20.01
49.51
36.35
11.00
10.74
11.11
11.11
4.81
4.81
4.81
32.70
0.926
0.378
0.845
0.719
45238
23716
38083
23936
14334
7
4.7 ꢀ 10
15667
o
oscillator strength (f), transition dipole moment (
l
), resonance en-
The standard free energy changes of complexation (DG ) were
ergy (R ), and ionization potential (I ) were estimated in chloro-
N
p
calculated from the formation constants by the following Eq. (9)
[38];
form or methanol at 25 °C, and the different acceptors were
found to have a pronounced effect on the interaction with TMEDA.
These calculations can be summarized as follows;
The oscillator strength f was obtained from the approximate
formula [31],
o
D
G ¼ ꢁ2:303RTlogK
ð9Þ
CT
o
ꢁ1
where
D
G is the free energy change of the CT complexes (kJ mol ),
ꢁ1
R is the gas constant (8.314 J mol K), T is the temperature in Kel-
vin, and KCT is the formation constant of the complexes (L mol ) in
ꢁ
1
f ¼ ð4:319 ꢀ 10ꢁ
9
Þ
e
max
m1=2
ð4Þ
max is the
different solvents at room temperature.
ꢁ1
where
m
1/2 is the band width at half intensity in cm and
e
maximum extinction coefficient of the CT band. The oscillator
strength values are given in Table 2. The data resulted reveal several
items. Firstly, the TMEDA/Acceptor (where Acceptor = Pi-OH, QL, io-
dine, and bromine) systems show high values of both formation
QL and iodine/TMEDA (1:1) charge-transfer systems
The reactions of TMEDA with the QL as a
p-acceptor were car-
ried out in methanol. The electronic absorption spectra of the reac-
ꢁ4
ꢁ4
tants, TMEDA (1.0 ꢀ 10 M), and QL acceptor (1.0 ꢀ 10 M) in
MeOH along with those of the formed 1:1 CT complex are shown
in Fig. 1. The spectrum demonstrates that the formed CT complex
has a detectable absorption band around 294 nm for [(TME-
DA)(QL)] complex. This band does not exist in the spectra of the
reactants in the same behavior. The stoichiometry of the [TME-
DA]-acceptor reactions were shown in both cases to be of 1:1 ratio.
This was concluded on the bases of the obtained elemental analysis
data of the isolated solid CT complexes. In these measurements,
constant (K) and molar absorptivity (e). This high value of K reflects
the high stability of the 18-crown-6 CT complexes as a result of the
expected high rich donation of the TMEDA, which contains two
nitrogen atoms fitted with four methyl groups. Secondly, the differ-
ent values of the oscillator strength, f, increase with increase in the
dielectric constant (D) of the solvent. This result could be explained
on the basis of competitive solvent interactions with the acceptors
[
32,33].
The transition dipole moment (
l) of the TMEDA charge-transfer
concentration of TMEDA was kept fixed, while the concentration
complexes have been calculated from Eq. (5) [34] and listed in
Table 2.
ꢁ4
of the acceptor was varied over the range of 0.25 ꢀ 10
–
ꢁ4
4
.00 ꢀ 10 M as described in the experimental section. Photomet-
1=2
ric titration curves based on these measurements are shown in
Fig. 2. The 1:1 modified Benesi–Hildebrand Eq. (2) was used in cal-
culating the values of the equilibrium constant, K, and the molar
l
ðDebyeÞ ¼ 0:0958½
e
max
m
1=2
=
m
max
ꢄ
ð5Þ
The transition dipole moment is useful for determining whether
transitions are allowed, that the transition from a bonding
p
orbital
o
o
absorptivity (e C and C is the initial concentrations of the accep-
a d
⁄
to an antibonding
p
orbital is allowed because the integral defin-
tor (QL) and the donor TMEDA, respectively, while A is the absor-
ing the transition dipole moment is nonzero.
bance of the strong band around 294 nm for the TMEDA/QL CT
The ionization potential (I ) of the TMEDA donor in their CT
p
o
a
o
d
o
a
o
d
complex. Plotting the values of the C C /A against C þ C values
complexes was calculated using empirical equation derived by
Aloisi and Piganatro and Briegleb Eq. (6) [35,36];
for QL acceptor, a straight line is obtained with a slope of 1/
e
and
intercept of 1/K as shown in Fig. 3. The values of both K and
e
e asso-
ðeVÞ ¼ 5:76 þ 1:53 ꢀ 10ꢁ4
ciated with these complexes were data obtained throughout these
calculations, which are given in Table 2. This complex shows high
values of both the formation constant (K) and the extinction coef-
I
p
m
CT
ð6Þ
where m
CT is the wavenumber in cm 1 corresponding to the CT band
ꢁ
formed from the interaction between donor and acceptor. The elec-
tron donating power of a donor molecule is measured by its ioniza-
tion potential, which is the energy required to remove an electron
from the highest occupied molecular orbital.
ficients (e). These high values of K confirm the expected high stabil-
ities of the formed CT complexes as a result of the expected high
donation of the TMEDA.
The energy of the CT complexes ECT of the TMEDA complexes is
calculated using the Eq. (7) [34];
Iodine, bromine and Pi-OH/TMEDA (1:2) charge-transfer systems
New detectable bands in the UV–visible spectra at (290 and
3
60 nm), 279 and 410 nm are observed immediately on mixing
E
CT ¼ ðh
m
CTÞ ¼ 1243:667=kCTðnmÞ
ð7Þ
solutions of TMEDA and each of the iodine, bromine and picric
acids in chloroform or methanol, respectively. The electronic
absorption spectra of the donor TMEDA with acceptors (I , Br ,
2 2
and Pi-OH) have molar ratios (donor:acceptor) of 1:2. Fig. 1 Re-
vealed absorption bands attributed to the CT interaction. The spec-
trum of the TMEDA/Br
at 279 nm with hyperchromic effect due to the formation of [(TME-
DA)]ꢃ2Br CT complex, while the corresponding absorption bands
associated with the formation of the complex [(TMEDA)(Pi-OH)
where, kCT is the wavelength of the complexation band.
Determination of resonance energy (R
N
) [37] theoretically de-
rived from (Eq. (8));
max ¼ 7:7 ꢀ 10ꢁ4=½h
e
mCT=½R
N
ꢄ ꢁ 3:5ꢄ
ð8Þ
2
system shows one strong absorption band
where
mum CT band,
e
max is the molar absorptivity of the CT complexes at maxi-
CT is the frequency of the CT peak, and R is the res-
m
N
2
onance energy of the complex in the ground state, which obviously
2
]
is a contributing factor to the stability constant of the complex (a
was observed at 410 nm. Furthermore, photometric titration mea-
surements based on the characteristic absorptions bands of the CT
complexes (Fig. 2) confirmed the molar ratios of the three
N
ground state property). The values of R for the TMEDA CT com-
plexes under study have been given in Table 2.

4
62
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
3
3
2
2
1
1
0
.5
.0
.5
.0
.5
.0
.5
2
1
1
0
0
.0
.5
.0
.5
.0
PiOH
Bromine
TMEDA
TMEDA
CT complex
CT complex
0.0
200
300
400
500
600
300
400
500
600
Wavelength (nm)
Wavelength (nm)
1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
4
3
2
1
0
Iodine
TMEDA
QL
CT complex
TMEDA
CT complex
200
300
400
500
600
200
300
400
500
600
Wavelength (nm)
Wavenumber (nm)
Fig. 1. Electronic spectra of [(TMEDA)(Pi-OH)
2 3
], [(TMEDA)(QL)], [(TMEDA)]IꢃI , and [(TMEDA)]ꢃ2Br
2
CT complexes.
5
TMEDA/ iodine
TMEDA/ bromine
4
.0
3.5
.0
4
3
2
1
0
3
3
3
2
.5
.0
.5
2.5
2.0
1.5
1.0
4
3.5
3.0
.0
2.0
2
2
.5
.0
1
1
0
0
.5
.0
.5
1.5
1.0
0
.5
0.0
250
.0
3
00
400
500
600
0.5
300
350
400
450
Wavenumber (nm)
Wavelength (nm)
0.0
0
.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
ml added of bromine
ml added of iodine
TMEDA/ QL
TMEDA/ Pi-OH
3.0
3
2
2
1
1
0
.0
.5
.0
.5
.0
.5
2
2
1
1
.5
.0
.5
.0
4
3
2
1
0
3.5
3.0
2.5
2
.0
1.5
1.0
0
0
.5
.0
0.5
.0
2
50 300 350 400 450 500
Wavelength (nm)
2
50
300
350
Wavelength (nm)
0
0
.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
ml added of QL
ml added of Pi-OH
Fig. 2. Photometric titration curves of [(TMEDA)(Pi-OH)
2 3
], [(TMEDA)(QL)], [(TMEDA)]IꢃI , and [(TMEDA)]ꢃ2Br
2
CT complexes.

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
463
1
1
1
1
0
0
0
0
0
.6
.4
.2
.0
.8
.6
.4
.2
.0
5
TMEDA/ iodine complex
TMEDA/ bromine complex
4
3
2
1
0
0
2
4
6
o
8
o
10
o
12
-8
14
16
18
5
10
15
o
20
25
-8
30
35
o
o
C
(4C +C ) x10
C
(4C +C ) x10
d
d
a
d
d
a
6
5
4
3
2
1
0
TMEDA/ Pi-OH complex
TMEDA/ QL complex
1
.2
.1
1
1.0
5
10
15
20
o
25
-8
30
35
200
250
300
o
350
-6
400
o
o
o
C
(4C +C ) x10
(C +C ) x 10
d a
d
d
a
Fig. 3. The 1:2 and 1:1 modified Benesi–Hildebrand curves for [(TMEDA)(Pi-OH)
2 3
], [(TMEDA)(QL)], [(TMEDA)]IꢃI , and [(TMEDA)]ꢃ2Br
2
CT complexes.
mentioned complexes. Photometric titrations between TMEDA and
iodine, Br , and Pi-OH in CHCl or MeOH solvent were carried out
as follows: concentration of TMEDA (C ) were kept fixed at
with C2v symmetry displays three vibrations
m
s
(I–I), A
1
;
m
as (I–I),
ꢁ
2
3
B
2; and d, (I ); A
3
1
, all are infrared active in good agreement [39–
+
ꢁ
d
41] with the observed of three Raman bands for [(TMEDA)]I .I .
3
ꢁ
4
1
C
.0 ꢀ 10 M, whereas that of the acceptor (iodine, Br
2
, or Pi-OH)
According to the foregoing discussion, a general mechanism is
ꢁ4
ꢁ4
+
ꢁ
a
was changed over a wide range of 0.25 ꢀ 10 –4 ꢀ 10 M.
proposed for the formation of [(TMEDA)]I ꢃI complexes as
3
The peak absorbances appeared in the spectra that assigned to
the formed CT complexes were measured and plotted as a function
follows:
þ
ꢁ
½
TMEDAꢄ þ I
2
! ½TMEDAꢄI :I
of the ratio C
d a
:C according to the known method [28]. The 1:2
modified Benesi–Hildebrand Eq. (3) was used to calculate the val-
ꢁ1
þ
ꢁ
þ
ꢁ
ues of the equilibrium constant, K (L mol ), and the extinction
½TMEDAꢄI :I þ I ! ½TMEDAꢄI :I
2
3
ꢁ1
ꢁ1
coefficient,
e(L mol cm ), for both complexes. The data obtained
throughout this calculation are given in Table 2. Plotting values of
o
A
2
o
D
o
A
o
A
o
D
ðC Þ C /A versus C ðC þ 4C Þ values of Eq. (3), straight lines are
IR spectral analyses
obtained with a slope of 1/
Fig. 3. Table 2 has the calculated values of the spectroscopic data
such as , K, , R G, I , and f, which were deduced from the
Eq. 4–9. Generally, these complexes show high values of both the
formation constant (K) and the molar absorptivity ( ). These high
values of K confirm the expected high stabilities of the formed CT
complexes as a result of the expected high donation of the TMEDA.
The equilibrium constants are strongly dependent on the nature of
the used acceptor including the type of electron withdrawing sub-
stituents to it, such as iodine, bromine, or nitro groups.
e and intercept of 1/Ke as shown in
The infrared spectra of the TMEDA as free donor, Pi-OH/TMEDA,
QL/TMEDA, SnCl /TMEDA, ZnCl /TMEDA, iodine/TMEDA, and bro-
e
l
N
,
D
p
4
2
mine/TMEDA complexes are shown in Fig. 4(A–G), and their band
assignments are given in Tables 3–5. The infrared spectrum of the
characteristic bands of TMEDA shows the following absorption
e
ꢁ
1
bands: (i) 3385, 3374, 2970, and 2943 cm assigned for the asym-
metric stretching vibrational bands of the methyl groups (–CH + –
), (ii) 2860, 2816, and 2766 cm due to the symmetric stretch-
ing vibrational bands of –CH + –CH , (iii) in the IR spectrum of free
donor, the bending deformation bands of methyl groups are as-
3
ꢁ
1
CH
2
3
2
In the case of TMEDA/iodine, the appearance of the two absorp-
tion bands around 360 and 290 nm is well known [39–43] to be
characteristic of the formation of the triiodide ion (I ). This was
also supported by the Raman laser spectrum of the iodine complex.
ꢁ
1
signed at 1684, 1454, 1404, and 1364 cm , (iv) the asymmetric
and symmetric stretching bands as(C–N) + (C–N) of C–N exist at
1338, 1311, 1299, 1282, and 1267 cm and 1167, 1138, 1097,
ꢁ
m
m
s
3
ꢁ
1
ꢁ1
This spectrum shows the characteristic bands for the triiodide ion
1086, 1043, and 1033 cm , respectively, (v) both of in-plane bend
ꢁ
as
m
as(I–I),
m
s
(I–I), and d(I ). These three absorptions do not exist in
d(CH) and rocking d(CH) have a detectable bands at 943 and
3
ꢁ
ꢁ1
ꢁ1
the spectrum of the donor. However, the I3 ion may be linear (D
or nonlinear (C2v). Group theoretical analysis indicates that the I3
h
)
876 cm
and 836, 788, and 777 cm , respectively, (vi) bands
ꢁ
ꢁ1
at 676 and 495 cm are assigned to out-of-plane bend of the

4
64
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
00
1
A
5
0
0
4
000
3000
2000
1500
1000
500
-
1
Wavenumber (cm )
B
105
C
100
100
95
90
85
80
75
70
65
60
8
0
60
40
20
4
000 3500 3000 2500 2000 1500 1000
500
4000 3500 3000 2500 2000 1500 1000
500
-1
-1
Wavenumber (cm )
Wavenumber (cm )
1
05
1
01
D
E
100
100
9
9
9
5
0
98
9
97
96
85
9
5
8
0
5
94
7
93
92
70
9
1
65
90
4
000 3500 3000 2500 2000 1500 1000
500
4000 3500 3000 2500 2000 1500 1000
500
-1
-1
Wavenumber (cm )
Wavenumber (cm )
1
05
00
F
G
100
1
95
90
9
0
80
85
8
0
70
75
70
60
6
5
50
60
4
000 3500 3000 2500 2000 1500 1000
500
4000 3500 3000 2500 2000 1500 1000
500
-1
-1
Wavenumber (cm )
Wavenumber (cm )
Fig. 4. Infrared spectra of (A) Free TMEDA, (B) [(TMEDA)(Pi-OH)
CT complexes.
2 3
], (C) [(TMEDA)(QL)], (D) [(TMEDA)]IꢃI , (E) [(TMEDA)]ꢃ2Br
2 4 2
, (F) [(TMEDA)(SnCl )], and (G) [(TMEDA)(ZnCl )]
d(C–N). These assignments are based on the comparison of the spec-
tra of CT complexes with the spectra of the reactants, (TMEDA) do-
nor, and the acceptors. The spectra of the formed CT complexes
contain the main bands for both TMEDA and the acceptor used,
and this strongly supports the formation of the [(TMEDA)(Pi-
OH)
DA)]ꢃ2Br
2
], [(TMEDA)(QL)], [(TMEDA)(SnCl
4
)], [(TMEDA)]IꢃI
3
, [(TME-
2
, and [(TMEDA)(ZnCl )] CT complexes. However, the bands
2
associated with spectra of the formed CT complexes show some
changes in intensities and in some cases show small shifts in the fre-
quency values compared with those of the free acceptor and the

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
465
Table 3
Table 4
Characteristic infrared frequencies (cmꢁ1) and tentative assignments of TMEDA free
Characteristic infrared frequencies (cm ) and tentative assignments of TMEDA free
ꢁ1
donor and their [(TMEDA)]IꢃI
3
and [(TMEDA)]ꢃ2Br
2
CT complexes.
2
donor and their [(TMEDA)(Pi-OH) ] and [(TMEDA)(QL)] CT complexes.
TMEDA
[(TMEDA)]IꢃI
3
[(TMEDA)]ꢃ2Br
2
Assignments(b)
TMEDA
[(TMEDA)(Pi-OH)
2
]
[(TMEDA)(QL)]
Assignments(b)
3
3
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
9
8
385
374
970
943
860
816
766
684
454
404
364
338
311
299
282
267
167
138
097
086
043
033
43
3432
3013
2949
2924
2892
2827
2656
1785
1659
1463
1407
1259
3391
3017
2940
3385
3374
2970
2943
2860
2816
2766
–
3297
3101
3059
2993
–
3031
2987
2958
m
3 2
as(C–H); CH + CH
m
m
3 2
as(C–H); CH + CH
2849
2768
2634
1663
1630
1470
1418
1283
1235
2873
2829
2791
2744
2699
2589
–
1513
1479
1373
s 3 2
m (C–H); CH + CH
s
3 2
(C–H); CH + CH
2668
2531
2489
1846
1611
1541
1489
1431
1365
1330
1268
m
(OHꢃ ꢃ ꢃN), hydrogen
bonding
d(CH) deformation
–
m
(NO
d(CH) deformation
(C=C)
2
), Pi-OH
1684
1454
1404
1364
m
m
as(C–N)
1151
1069
1042
1153
1119
1058
1027
1338
1311
1299
1282
1267
1167
1138
1097
1086
1043
1033
943
1255
1226
m
m
as(C–N)
s
m (C–N)
1162
1080
1161
1141
1093
1021
s
(C–N)
992
871
998
976
d(CH) in-plane bend
d(CH) rocking
76
9
8
43
96
8
7
7
6
4
36
88
77
76
95
784
789
1003
973
919
844
789
741
896
d(CH) in-plane bend
876
668
558
590
510
461
d(C–N) out-of-plane bend
4
4
59
08
836
788
826
796
762
511
438
777
676
495
d(CH) rocking
d(C–N) out-of-plane
bend
709
546
5
4
19
41
d(ONO)
TMEDA donor. This could be understood on the basis of symmetry
and electronic structure changes in both acceptor and TMEDA in
the formed CT complexes compared with those of the free mole-
cules. In the case of [(TMEDA)(Pi-OH)
2
] and [(TMEDA)(QL)] CT com-
(
Formulas 21 and 22) in order to ascertain the complexation sites
plexes, the appearance of a few absorption bands at 2668, 2531, and
ꢁ1
ꢁ1
that may be involved in chelation (Table 5). In the spectra of the
complexes (Fig. 4), the infrared spectra of these complexes exhib-
2
489 cm and 2699, 2589, and 2365 cm , respectively, usually
comes from stretching vibrations between hydrogen (acceptor)
and some nitrogen atoms (TMEDA) [44]. Hydrogen bonding
ꢁ1
ited non-ligand bands in the regions 460–570 cm , assignable to
(M–N) vibrations [44].
m
(
m
(OHꢃ ꢃ ꢃN) has a significant influence on the peak shape and inten-
sity, generally causing peak broadening and shifts in absorption to
lower frequencies. The presence of these bands confirmed that the
proton transfer phenomena from the acidic center of each acceptor
Raman spectral analyses
(
Pi-OH and QL) to the lone pair of electron on nitrogen atom to form
2
Fig. 5A–E shows the Raman spectra of [(TMEDA)(Pi-OH) ],
OHꢃ ꢃ ꢃN hydrogen bonding upon complexation (Formulas 17
and 18). Also, there are some small changes comparing the spectra
of the CT complexes and those of the reactants, which could also be
notable from the expected changes in the symmetry and
electronic configurations of both reactants upon charge-transfer
complexation.
[(TMEDA)(SnCl
DA)(ZnCl )] CT complexes in the (4000–50 cm ) frequency ranges.
As one can see from Fig. 5 concerning the [(TMEDA)(Pi-OH) ] com-
4
)], [(TMEDA)]IꢃI
3
,
[(TMEDA)]ꢃ2Br
2
, and [(TME-
ꢁ
1
2
2
1
ꢁ
plex, vibrations at 1633, 1612, 1548, 1530, and 1346 cm clearly
correspond to the symmetric vibrational modes of (C = C) of
Pi-OH and bending deformation of d(CH). The difference intense
m
ꢁ
1
ꢁ1
The mid-infrared spectra of [(TMEDA)]IꢃI
3
and [(TMEDA)]ꢃ2Br
2
bands at 1315 and 1273 cm and 1177 and 1083 cm have been
assigned to as(C–N) and (C–N) stretching vibrations, while the
formed CT complex were recorded from KBr disks. The spectral
bands are resolved and assigned into their vibrational modes and
given in Table 3. As expected, the bands characteristic of the TME-
m
m
s
ꢁ1
frequencies component at 943 and 827 cm has been attributed
to the in-plane bend deformation and rocking overtone vibration
DA unit in both [(TMEDA)]IꢃI
3
and [(TMEDA)]ꢃ2Br
2
CT complexes
of CH
3 2
and CH groups. Assignments of the d(CN) out-of-plane
are shown with small changes in band intensities and frequency
values (Formulas 19 and 20).
and d(ONO) of Pi-OH acceptor vibrational bands exist at 706,
329, and 206 cm . On examining the Raman spectra of the [(TME-
DA)(SnCl )], and [(TMEDA)(ZnCl )] CT complexes in comparison
with TMEDA, it was found that the spectra of the Sn(IV) and Zn(II)
complexes exhibited non-ligand bands in the regions 470–505 and
380–212 cm , assignable to m(M–N) and m(M–Cl) vibrations,
ꢁ
1
For the CT complexes [(TMEDA)(Pi-OH)
when the molar ratio is 1:2, it is more likely to propose that the
TMEDA) is arranged in such a way that it is sandwiched between
2
] and [(TMEDA)]ꢃ2Br
2
4
2
(
ꢁ1
the two acceptor molecules.
The infrared spectrum of the TMEDA donor was compared with
respectively [44]. Resonance Raman spectroscopy has been used
4 2
those of the [(TMEDA)(SnCl )] and [(TMEDA)(ZnCl )] complexes
to study the reaction of iodine with the interesting TMEDA donor.

4
66
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
Table 5
Characteristic infrared frequencies (cmꢁ1) and tentative assignments of TMEDA free
donor and their [(TMEDA)(SnCl )] and [(TMEDA)(ZnCl )] CT complex.
4
2
CH3
H3C
TMEDA
[(TMEDA)(SnCl
4
)]
[(TMEDA)(ZnCl
2
)]
Assignments(b)
N
N
3
3
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
9
8
8
7
7
6
4
m
385
374
970
943
860
816
766
684
454
404
364
338
311
299
282
267
167
138
097
086
043
033
43
3418
3088
3029
2966
2769
2736
3001
2976
2930
m
m
3 2
as(C–H); CH + CH
CH3
H C
3
I
I
2895
2819
s 3 2
(C–H); CH + CH
I
I
1632
1458
1408
1351
1288
1232
1467
1353
d(CH) deformation
Formula. 19. Suggested structure of [(TMEDA)]IꢃI
3
charge-transfer complex.
1290
1247
1200
m
m
as(C–N)
Br
CH3
Br
1146
1119
1049
1170
1127
1023
s
(C–N)
H3C
N
N
CH3
Br
Br
CH3
990
972
832
771
953
d(CH) in-plane bend
d(CH) rocking
Formula. 20. Suggested structure of [(TMEDA)]ꢃ2Br
2
charge-transfer complex.
76
36
88
77
76
95
(M–N)
831
801
766
587
499
H3C
CH3
CH3
669
565
d(C–N) out-of-plane
bend
Cl
N
N
4
4
68
39
Sn
H3C
Cl
Cl
Cl
Formula. 21. Suggested structure of [(TMEDA)(SnCl
4
)] charge-transfer complex.
CH3
N
H C
3
N
3
H C
CH3
CH3
H
H3C
N
N
H
O
Zn
O-
N+
O
O-
3
H C
CH3
O
O
Cl
Cl
N+
N+
N+
O
O-
O
O-
Formula. 22. Suggested structure of [(TMEDA)(ZnCl
2
)] charge-transfer complex.
ꢁ
1
and 161 cm
to the symmetric and anti-symmetric stretching
N+
N+
vibrations, respectively, and the observed bending vibration at
13 cm is weak broad in the Raman spectrum. In the literature,
O
O-
O
O-
ꢁ1
2
the Raman spectrum of the band for free bromine exhibited at a
Formula. 17. Suggested structure of [(TMEDA)(Pi-OH)
2
] charge-transfer complex.
ꢁ1
very intense wavenumber 310 cm . In the Raman spectrum of
CT complex, the halogen vibration band,
[
m
(TMEDA)]ꢃ2Br
2
ꢁ1
(Br–Br), is shifted in the lower frequency direction at 166 cm .
1
CH3
CH3
H–NMR spectral analysis
H C
3
N
N
1H–NMR data were expressed in parts per million (ppm), and
they were referenced internally to the residual proton impurity
in DMSO (dimethylsulfoxide). The H–NMR spectra of the [(TME-
H3C
H
O
H
O
1
2 4
DA)(Pi-OH) ], [(TMEDA)(QL)], [(TMEDA)(SnCl )], and [(TME-
DA)(ZnCl )] CT complexes (Fig. 6) are consistent with the
2
1
proposed structures (Formulas 17, 18, 21 and 22). The H–NMR
spectral data of TMEDA and their CT complexes were reported in
Table 6.
Formula. 18. Suggested structure of [(TMEDA)(QL)] charge-transfer complex.
The results indicate that the complex [(TMEDA)]IꢃI
3
is formed. Maki
In the TMEDA free donor, the peak at 2.243 ppm corresponds to
(12H; 4CH ) twelve protons of four methyl groups, and beside, peak
3
ꢁ
and Forneris [42] assigned the lines of Raman spectra of I3 at 111

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
467
A
B
2
2
1
.5
.0
.5
0
0
0
0
0
.4
.3
.2
.1
.0
1.0
0
.5
.0
0
4
000 3500 3000 2500 2000 1500 1000 500
0
300
250
200
150
100
-1
50
0
Wavenumber (cm-1)
Wavenumber (cm
)
0
0
0
0
0
0
0
0
0
.16
.14
.12
.10
.08
.06
.04
.02
.00
C
D
0.10
0
0
0
0
0
.08
.06
.04
.02
.00
-0.02
500
400
300
200
100
0
4000 3500 3000 2500 2000 1500 1000 500
0
Wavenumber (cm-1)
Wavenumber (cm )
-1
E
0
0
0
0
0
0
0
0
.014
.012
.010
.008
.006
.004
.002
.000
-
0.002
4000
3500
3000
2500
2000
1500
1000
500
0
-1
Wavenumber (cm )
Fig. 5. Raman spectra of (A) [(TMEDA)(Pi-OH)
2
], (B) [(TMEDA)]IꢃI
3
, (C) [(TMEDA)]ꢃ2Br , (D) [(TMEDA)(SnCl
2
4
)], and (E) [(TMEDA)(ZnCl
2
)] CT complexes.
in the same zone at 2.384 ppm corresponds to the four protons of
CH . The discussion of the downfield status for the protons
concerning –CH and –CH group is due to the formation of inter-
QL, respectively, via intermolecular hydrogen bond, which are
shifted relative to the value of pure Pi-OH and QL acceptors. On
the other hand, the proton signals of aromatic rings for both
Pi-OH and QL were shifted slightly up field, from 8.624 ppm (pure
Pi-OH) to 8.599 ppm (after complexation) and from 6.579 ppm
(free QL) to 6.552 ppm (after complexation).
2
2
3
2
1
molecular CT complexes. Compared with the H–NMR spectrum
1
data of pure TMEDA, Pi-OH, and QL moieties, the H–NMR spectra
of the [(TMEDA)(Pi-OH)
chemical shift at 2.170–2.860 ppm and 3.126–3.756 ppm of 4CH
and 2CH protons, respectively. According to this discussion, it
2
] and [(TMEDA)(QL)] exhibit a down field
3
The [(TMEDA)(SnCl
were characterized by IR, Raman, and H–NMR spectra and ele-
mental analysis. After complexation, the protons of both –CH
and –CH groups, the signals for CH (2.444 and 2.809 ppm)
and CH (2.7059–3.408 ppm) hydrogens are shifted slightly up
field in comparison with the same signals found in TMEDA.
4 2
)] and [(TMEDA)(ZnCl )] CT complexes
1
2
can be said that the electronic environments of the TMEDA protons
change with the formation of the Pi-OH and QL CT complexes. The
weak broadening signals exhibited at 9.442 and 8.731 ppm were
3
2
2
3
assigned to the protons of m(O–H. . .N) interactions for Pi-OH and

4
68
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
Thermal analysis
weight loss of 62.59%, which is very close to the theoretical value
of 62.39% corresponding to the loss of H22 14 moiety as will
8
N O
To make sure about the proposed formula and structure of the
be described by the mechanism of the decomposition. The final
thermal product obtained at 800 °C is few carbon atoms (18C).
Accordingly, the mechanism for the thermal decomposition of
new TMEDA CT complexes, [(TMEDA)(Pi-OH)
2
], [(TMEDA)(QL)],
, [(TMEDA)]ꢃ2Br , and [(TMEDA)
)], thermogravimetric (TG) analysis was carried out for these
[
(
(TMEDA)(SnCl
ZnCl
4
)], [(TMEDA)]IꢃI
3
2
2
2
the Pi-OH complex, [(TMEDA)(Pi-OH) ], is follows:
complexes under static air flow. TG curves are shown in Fig. 7A–F.
Table 7 gives the maximum temperature values, Tmax/°C, together
with the corresponding weight loss for each step of the decompo-
sition reactions of these complexes. The obtained data strongly
support the structure proposed for the TMEDA complexes under
investigation.
The thermal decomposition of the [(TMEDA)(Pi-OH) ] complex
2
proceeds approximately with very strong one main degradation
step. This stage occurs at a maximum temperature of 191 °C with
ꢅ
191
c
½
ðTMEDAÞðPi ꢁ OHÞ ꢄ ! H22
The TGA curve of [(TMEDA)(QL)] CT complex indicates that the
mass change begins at 125 °C and continuous up to 800 °C. The
main mass loss at TGmax = 191 °C is a wide broad peak that corre-
sponds to the liberation of most organic moiety of both TMEDA
and QL molecules (obs. = 96.44%, calc. = 94.54%). The final decom-
position of the organic moiety led to residual carbon atoms.
N
8
O
14ðlossÞ þ 18C ðresidueÞ:
2
Fig. 6. 1HNMR spectrum of (A) Free TMEDA, (B) [(TMEDA)(Pi-OH)
], (C) [(TMEDA)(QL)], (D) [(TMEDA)(SnCl )], and (E) [(TMEDA)(ZnCl )] CT complexes.
2 4 2

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
469
ꢅ
1
91
c
½
ðTMEDAÞðQLÞꢄ ! C11
H
22
N
2
O
2
ðlossÞ þ 1C ðresidueÞ:
To establish the proposed formula and structure for each of the
complexes under investigation, thermogravimetric (TG) analysis
was carried out for the two solid charge-transfer complexes [(TME-
DA)]IꢃI3 and [(TMEDA)]ꢃ2Br2 under static air flow. The data ob-
tained support the proposed structures of the two complexes and
indicate the following:
(
i) The thermal degradation of the [(TMEDA)]IꢃI3 complex takes
place in two degradation stages, Fig. 7 and Table 7. The first
stage of decomposition occurs at a maximum temperature of
2
53 °C. This stage of degradation is accompanied by weight
of loss 39.26% corresponding to the loss of one iodine mole-
cule. Theoretically, the loss of these molecules corresponds
to a weight loss of 40.70%. The second decomposition stage
occurs at the maximum temperature of 343 °C. The weight
loss at this step is 60.31% due to the loss of C
agreement with the theoretical weight loss value of
9.30%. According to the above discussion the decomposi-
6 16 2 2
H N I in
5
tion mechanism of the [(TMEDA)2]IꢃI3 complex is as follows:
ꢅ
2
53
c
½
ðTMEDAÞꢄI ꢃ I
3
! I
2
þ C
6 16 4 2
H N I
ꢅ
3
43
c
C
11
H
28
N
4
I
2
! C11
H
28
N
4
I
2
þ zeroðresidueÞ:
From this mechanism of decomposition, we can deduce that iodine
molecules play an important role as a catalysis in the decomposi-
tion processes.
(
i) The thermal decomposition of [(TMEDA)]ꢃ2Br
2
complex pro-
ceeds with two main degradation steps. The first stage of the
decomposition occurs at the maximum temperature of
1
50 °C is accompanied by weight loss of 26.26% correspond
to the loss of the two methane and half bromine molecules.
Theoretically, the losses of these molecules correspond to a
weight loss of 25.67%, which agrees with the experimental
result. The second decomposition stage occurs at the maxi-
mum temperature of 326 °C. The weight loss at this step is
7
4 8 2 3
3.74% associated with the loss of C H N Br . The theoretical
weight loss value is 74.27%. Accordingly, the following
mechanism was proposed for thermal decomposition of
the [(TMEDA)]ꢃ2Br
2
complex:
ꢅ
1
50
c
½
ðTMEDAÞꢄ ꢃ 2Br
2
ꢁ! 1=2Br
2
þ 2CH
4
ðlossÞ þ C
4 8 2 3
H N Br
ꢅ
3
26
c
C
4
H
8
N
2
Br
3
ꢁ! C
4
H
8
N
2
Br
3
þ zeroðresidueÞ:
)] is shown in Fig. 7. Table 7
TG thermogram of [(TMEDA)(ZnCl
2
gives the maximum temperature values, Tmax/°C, together with the
corresponding weight loss for each step of the decomposition reac-
tion. The data obtained support the proposed structure and indi-
cate that the thermal decomposition of this complex proceeds
with two main degradation steps. The first stage of decomposition
occurs at a temperature maximum of 357 °C. The found weight loss
associated with this step is 49.03% and may be attributed to the
decomposition of TMEDA donor. The second stage of decomposi-
tion occurs at a temperature maximum of 569 °C. The weight loss
found at this stage equals to 41.09%, corresponds to the loss of
remaining TMEDA molecule. The continuous of weight loss in the
2
decomposition diagram of [(TMEDA)(ZnCl )] complex can be dis-
cussed as follows: The zinc metal is hard and brittle at most tem-
peratures, but becomes malleable between 100 and 150 °C. Above
2
10 °C, the metal becomes brittle again and can be pulverized by
beating. The [(TMEDA)(SnCl )] complex start decomposing at
239 °C with Tmax at 342 °C with simultaneous decomposition. The
4
Fig. 6 (continued)

4
70
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
Table 6
1
H–NMR spectral bands (ppm) and tentative assignments of TMEDA free donor (1), Pi-OH (2), QL (3) and their [(TMEDA)(Pi-OH)
2 4
] (4), [(TMEDA)(QL)] (5), [(TMEDA)(SnCl )] (6),
and [(TMEDA)(ZnCl
2
)] (7) CT complex.
ppm
1
Assignments(b)
2
3
4
5
2
6
7
.170
2
.243
.384
–
–
–
–
2.860
3.446
2.283
.750
3.126
3.347
2.809
2.444
12H; 4CH
4H; 2CH
2H; Aromatic ring
H; OH of Pi-OH or QL
3
2
2
3.167
3.408
2.705
3.168
3.328
2
3
.756
–
–
–
8.624
–
6.579
8.590
8.599
9.442
6.552
8.731
–
–
decomposition steps seem to be consistent with a mass loss of
obs. = 68.68% and calc. = 68.48% due to loss of C Cl as a gas-
Biological evaluation
H
6 16
N
2
4
eous molecules. The difference between the observed weight loss
and complex at all (100%) was devoted to the residual tin metal.
Biological activities were observed in terms of antimicrobial
activities of target charge-transfer complexes against gram-positive
1
0
8
6
4
2
0
2
1
1
1
4
2
0
8
6
4
A
B
-
0
0
0
100 200 300 400 500 600 700 800 900
0
0
0
100 200 300 400 500 600 700 800 900
o
o
Temp. [ C]
Temp. [ C]
20
15
10
5
0
C
D
1
1
1
1
6
4
2
0
8
6
4
2
0
2
-
100 200 300 400 500 600 700 800 900
100 200 300 400 500 600 700 800 900
o
o
Temp. [ C]
Temp. [ C]
E
F
18
16
14
12
10
8
6
4
2
0
1
0
8
6
4
2
100 200 300 400 500 600 700 800 900
100 200 300 400 500 600 700 800 900
o
o
Temp. [ C]
Temp. [ C]
Fig. 7. TG curves of (A) [(TMEDA)(Pi-OH)
2 3
], (B) [(TMEDA)(QL)], (C) [(TMEDA)]IꢃI , (D) [(TMEDA)]ꢃ2Br
2 4 2
, (E) [(TMEDA)(SnCl )], and (F) [(TMEDA)(ZnCl )] CT complexes.

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
471
Table 7
The maximum temperature, Tmax/°C, and weight loss values of the decomposition stages for the [(TMEDA)(Pi-OH)
2
], [(TMEDA)(QL)], [(TMEDA)(SnCl
4
)], [(TMEDA)]IꢃI
3
,
[
2
(TMEDA)]ꢃ2Br , and [(TMEDA)(ZnCl
2
)] CT complexes.
Complexes
Decomposition
Tmax/°C
Lost
% Weight loss
Found
Species
Calc.
[
[
[
(TMEDA)(Pi-OH)
2
]
First step
Total loss
Residue
First step
Total loss
Residue
First step
Second step
Total loss
Residue
191
191
H
22
N
8
O
14
62.59
62.59
37.41
96.44
96.44
3.56
39.26
60.31
99.57
–
62.39
62.39
37.61
94.54
94.54
5.45
40.70
59.30
100
18C
C H N O
11 22 2 2
(TMEDA)(QL)]
1C
(TMEDA)]IꢃI
3
253
343
I
2
C
6 16 2 2
H N I
–
–
[
[
[
(TMEDA)]ꢃ2Br
2
First step
Second step
Total loss
Residue
First step
Second step
Total loss
Residue
150
326
½Br
2
+ 2CH
4
26.26
73.74
100
25.67
74.33
100
C
4
H
8
N
Br
2 3
–
C
C
–
–
(TMEDA)(ZnCl
2
)]
357
569
4
H
H
12
N
2
Cl
49.03
48.90
–
–
2
4
Cl + melt of Zn metal
41.09
90.12
9.88
68.68
68.68
31.32
Zn metal
Cl
–
(TMEDA)(SnCl
4
)]
First step
Total loss
Residue
342
C
6
H
16
N
2
4
68.48
68.48
31.52
Sn metal
Table 8
Inhibition zone diameter (mm) of the target compounds against tested microorganisms.
Sample
Inhibition zone diameter (mm/mg sample)
Bacillus subtilis Escherichia coli
Pseudomonas
aeruginosa (G )
Staphylococcus
aureus (G )
Aspergillus flavus
(Fungus)
Candida albicans
(Fungus)
+
ꢁ
ꢁ
+
(
G )
(G )
Control: DMSO
Antifungal agent
0.0
0.0
0.0
0.0
0.0
0.0
Standard (Tetracycline)
34
–
9
24
9
10
13
19
32
–
9
23
10
10
14
16
34
–
9
28
9
10
15
21
30
–
10
28
9
10
13
20
–
18
0
16
0
–
19
0
17
0
(
[
[
[
[
[
[
Amphotericin B)
(TMEDA)(Pi-OH)
(TMEDA)(QL)]
2
]
(TMEDA)]IꢃI
(TMEDA)]ꢃ2Br
(TMEDA)(ZnCl
(TMEDA)(SnCl
3
2
0
0
0
0
0
2
)]
)]
4
Gram reaction. Solvent: DMSO.
(B. subtilis andS. aureus) and gram-negative (E. coli andP. aeruginosa)
and tow strains of fungus (A. flavus andC. albicans). Results from the
agar disk diffusion tests for antimicrobial activities of target com-
pounds are presented in Table 8 and illustrated in Fig. 8. The diam-
eters of zone of inhibition (in mm) of the standard drug tetracycline
against gram-positive bacteria B. subtilis and S. aureus and gram-
negative bacteria E. coli and P. aeruginosa were found to be 34, 32,
B. subtilis
E. coli
3
2
0
5
P. aeruginosa
S. aureus
Aspergillus flavus
Candida albicans
3
4, and 30 mm, respectively, while the standard drug amphotericin
B against A. flavus and C. albicans gave 18 and 19, respectively. Un-
der identical conditions, Table 8 shows that [(TMEDA)(Pi-OH)
complex has (9, 9, 9, 10, 0, and 0 mm), [(TMEDA)(QL)] complex
has (24, 23, 28, 28, 16, 17 mm), [(TMEDA) has (9, 10, 9, 9, 0,
]IꢃI
and 0 mm), [(TMEDA)]ꢃ2Br complex has (10, 10, 10, 10, 0, 0 mm),
(TMEDA)(ZnCl )] complex has (13, 14, 15, 13, 0, 0 mm), [(TME-
DA)(SnCl )] complex has (19, 16, 21, 20, 0, and 0 mm), respectively,
2
]
20
2
3
1
1
5
0
5
0
2
[
2
4
for B. subtilis, E. coli, P. aeruginosa, S. aureus, A. flavus, C. albicans. All
complexes were found to be efficient antibacterial agents except for
[
(TMEDA)(QL)] complex, which is efficient both antibacterial and
antifungal agents.
Pi-OH
QL
Iodine Bromine Zn(II)
CT complexes
Sn(IV)
X- ray powder diffraction studies
Fig. 8. Antibacterial and antifungal activity [(TMEDA)(Pi-OH)
(TMEDA)]IꢃI , [(TMEDA)]ꢃ2Br , [(TMEDA)(SnCl )], and [(TMEDA)(ZnCl
plexes as inhibition zones (mm).
2
], [(TMEDA)(QL)],
The X-ray powder diffraction patterns for the new TMEDA
charge-transfer complexes [(TMEDA)]2Br , [(TMEDA)(Pi-OH) ],
2 2
[
3
2
4
2
)] CT com-

4
72
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
2
2
1
1
50
00
50
00
A
B
2
1
1
000
500
000
500
50
0
0
0
10
20
30
40
50
60
70
80
0
10
20
30
40
2θ
50
60
70
80
2
θ
1
1
1
1
6000
4000
2000
0000
C
D
2
1
1
000
500
000
8
6
4
2
000
000
000
000
0
500
0
-2000
0
10
20
30
40
50
60
70
80
0
10
20
30
40
2θ
50
60
70
80
2
θ
Fig. 9. XRD spectra of (A) [(TMEDA)]ꢃ2Br
2 2 2
, (B) [(TMEDA)(Pi-OH) ], (C) [(TMEDA)(QL)], and [(TMEDA)(ZnCl )] CT complexes.
Table 10
Table 9
The resulting indexing of the system (TMEDA)(QL) complex and the resulting lattice
parameters a, b, c, b, volume V.
2
The resulting indexing of the system (TMEDA)(ZnCl ) complex and the resulting
lattice parameters a, b, c, b, volume V.
h
k
l
d-Obs
2h-Obs
2h-Cal
DELTA
h
k
l
d-Obs
2h-Obs
2h-Cal
DELTA
1
0
1
0
1
1
2
6.9485
6.1101
5.9894
12.730
14.485
14.779
12.693
14.509
14.772
0.037
ꢁ0.024
0.007
ꢁ
1
0
1
0
0
1
1
0
1
8.6384
7.4625
6.2380
10.232
11.850
14.187
10.210
11.847
14.188
0.022
0.003
ꢁ0.001
0.007
0.018
0.010
ꢁ
1
1
ꢁ
(
TMEDA)(QL)
(
2
TMEDA)(ZnCl )
ꢁ
2
0
0
0
2
1
1
5.2069
4.6248
4.3569
17.015
19.175
20.367
17.044
19.178
20.348
ꢁ0.035
ꢁ0.013
0.019
ꢁ
1
1
0
0
1
2
2
5.7252
5.2126
4.3192
15.465
16.996
20.541
15.458
16.978
20.501
System: monoclinic
2
System: monoclinic
ꢁ1
0
0
ꢁ3
3
ꢁ
ꢁ
2
1
a = 13.0854(123) ÅA
a = 12.0138(13) ÅA
0
0
0
1
0
1
4.0340
3.9398
22.017
22.550
22.027
22.543
ꢁ0.010
0.007
2
1
3.4926
25.483
25.472
0.011
b = 7.5334(85) ÅA
b = 7.6379(6) ÅA
c = 10.9273(58)
0
2
1
1
3
2
3
0
3
0
3
2.5032
2.4900
2.4875
35.845
36.040
36.079
35.847
36.049
36.069
ꢁ0.002
ꢁ0.009
0.010
c = 12.0273(78) ÅA
b = 112.42(74)°
V = 1096.02 ÅA 3
b = 98.50(12)°
ꢁ2
0
1
3
2
3.8935
3.8333
22.821
23.185
22.848
23.202
ꢁ0.027
ꢁ0.017
0
0
1
V = 991.67 ÅA 3
5
6
2
1
1
3
0
4
4
2
0
3
3
1
2
1.9941
1.9167
1.9115
1.8552
1.8501
1.6702
45.447
47.392
47.502
49.066
49.210
54.930
45.450
47.387
47.511
49.070
49.215
54.927
ꢁ0.003
0.005
ꢁ0.009
ꢁ0.004
ꢁ0.005
0.003
ꢁ3
0
ꢁ3
ꢁ2
3
1
2
0
0
2
2
1
3
4
0
3.5932
3.5667
3.4648
2.9947
2.7482
24.758
24.945
25.691
29.811
32.515
24.759
24.939
25.687
29.796
32.503
ꢁ0.001
0.006
0.004
0.015
0.012
ꢁ
6
3
1
ꢁ
[
(TMEDA)(QL)], and [(TMEDA)(ZnCl
Inspecting these patterns, we notice that the systems (TMEDA)(QL)
and (TMEDA)(ZnCl are well crystalline compared with
(TMEDA)]ꢃ2Br , which has high background and less intensity.
2
)] are depicted in Fig. 9.
heavy overlapping of the diffraction peaks. Single crystal for this
system should be used for its structural determination, which is
a further work.
2
)
[
2
To get structural data about these systems, we tried to index the
diffraction patterns applying the CRYSFIRE system [45]. It is a
powder-indexing wizard in the form of a family of DOS scripts
and programs for running eight indexing programs automatically.
The indexing results revealed that all patterns are monoclinic
systems but with different lattice constants, and the results are
SEM and EDX studies
Surface image using SEM (Fig. 10A–F) demonstrates the porous
structures of the surface of prepared charge-transfer complexes.
Analysis of these images shows the size of pores to be quite differ-
ent with different acceptors. The chemical analysis results by EDX
for the formed charge-transfer complexes show a homogenous dis-
tribution of each acceptor. SEM examinations checked the surfaces
given in Tables 9–11. For the system (TMEDA)(Pi-OH)
satisfactory indexing could be obtained, which may be due to the
2
, no

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
473
Table 11
complexes were determined using energy-dispersive X-ray diffrac-
tion (EDX). In the EDX profile of these complexes (Fig. 10A–F), the
peaks of the essential two elements such as carbon and nitrogen,
beside oxygen, and subsidiary elements, which constitute the mol-
The resulting indexing of the system (TMEDA).2Br
parameters a, b, c, b, volume V.
2
complex and the resulting lattice
h
k
L
d-Obs
2h-Obs
2h-Cal
DELTA
ꢁ
2
2
1
0
0
0
1
0
1
8.0056
5.7293
4.5742
11.043
15.453
19.390
11.031
15.435
19.400
0.012
0.018
ꢁ0.010
0.019
0.017
0.002
ecules of [(TMEDA)(Pi-OH)
2
], [(TMEDA)(QL)], [(TMEDA)(SnCl
4
)],
[(TMEDA)]IꢃI
3
,
[(TMEDA)]ꢃ2Br
2
,
and [(TMEDA)(ZnCl )] charge-
2
(
TMEDA)ꢃ2Br
2
transfer complexes, are clearly identified confirming the proposed
structures.
0
1
3
2
2
0
0
0
0
4.2290
3.9679
3.8238
20.990
22.388
23.243
20.971
22.371
23.241
System: monoclinic
0
a = 11.6454(45) ÅA
0
Electrical conductivity studies
ꢁ
3
2
1
1
2
0
3.6239
3.4871
24.545
25.524
24.559
25.539
ꢁ0.014
ꢁ0.015
b = 8.4653(18) ÅA
0
c = 9.6213(72) ÅA
b = 99.89 (3)°
The frequency dependence of AC conductivity of SnCl
4
and
ꢁ3
1
0
1
1
3.4479
3.3531
25.819
26.562
25.799
26.569
ꢁ0.020
0
ZnCl CT complexes at T = 306 K is shown in Fig. 11. The AC con-
V = 934.38 ÅA 3
3
ꢁ0.017
2
ductivity tends to increase slightly with increasing frequency. This
can be attributed to the enhancement of the conduction carriers
by applied external field. For these two complexes, the dielectric
2
1
2
0
4
2
2
3
1
3.5667
3.1378
1.9623
1.7897
28.420
28.452
46.226
50.988
28.413
28.430
46.223
50.992
0.007
0.022
0.003
ꢁ0.004
ꢁ
1
4
3
0
constant and dielectric loss (e and tand) were measured as a func-
tion of frequency of applied electric field at T = 306 K (see Figs. 12
and 13). It has been found that both complexes have similar
variation trend of the dielectric constant against frequency, where
the dielectric constant tends to sharply decrease with the increase
in applied field with low frequency. This may be due to the polar-
ization resulting from the heterogeneous structure. In the range
of high frequency, the dielectric constant seems likely to be
of these CT complexes that show a small to medium particles,
which has tendency to agglomerate formation with different
shapes in comparison with the starting materials. The chemical
compositions of the free TMEDA donor and charge-transfer
4
3
3
2
2
2
1
1
000
600
200
800
400
000
600
200
8
4
00
00
0
0
.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00
keV
2
Fig. 10A. SEM/EDX of [(TMEDA)(Pi-OH) ] CT complex.
2
2
1
1
1
400
100
800
500
200
9
6
3
00
00
00
0
0
.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
Fig. 10B. SEM/EDX of [(TMEDA)(QL)] CT complex.

4
74
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
0
01
5
4
4
3
2
1
600
800
000
200
400
600
8
00
0
0
.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
4
Fig. 10C. SEM/EDX of [(TMEDA)(SnCl )] CT complex.
4
4
3
3
2
2
1
1
500
000
500
000
500
000
500
000
5
00
0
0
.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
3
Fig. 10D. SEM/EDX of [(TMEDA)]IꢃI CT complex.
5
4
4
3
2
1
600
800
000
200
400
600
8
00
0
0
.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
Fig. 10E. SEM/EDX of [(TMEDA)]ꢃ2Br
2
CT complex.
frequency independent. Such behavior can be attributed to the
low charge carrier’s mobility, which hinders the frequency change
and cannot follow the frequency change. The results indicated
4 2
that the dielectric loss of SnCl and ZnCl CT complexes is contin-
uously decreasing with frequency in the range of studied
frequency.

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
475
2
2
1
1
1
400
100
800
500
200
9
6
3
00
00
00
0
0
.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
2
Fig. 10F. SEM/EDX of [(TMEDA)(ZnCl )] CT complex.
-
-
-
-
15
16
17
18
6
0
(
A)
5
4
3
2
1
0
0
0
0
0
(
A)
-
-
19
18
12
(B)
1
1
1
0
9
8
7
-
-
-
-
-
19
20
21
22
23
6
5
(B)
4
5
6
7
8
9
10
11
12
4
5
6
7
8
9
10
11
12
ln F(Hz)
ln F(Hz)
0
4
e ) at T = 306 K for Sn Cl (A)
Fig. 11. Frequency dependence of AC conductivity at T = 306 K for SnCl
ZnCl (B) charge-transfer complexes.
4
(A) and
Fig. 12. Frequency dependence of dielectric constant (
and Zn Cl (B) charge-transfer complexes.
2
2
Positron annihilation studies
indicates that there is one type of vacant. The results indicate that
the value of Pi-OH CT complex is comparable with the value of
Br CT complexes due to their same donor-to-acceptor molar ratio
of 1:2. The values are decreased by 27%, 17%, and 10% for ZnCl
QL, and SnCl , respectively, due to the different electron acceptor
power and acceptor configuration in each case.
The and I values, ascribed mainly to the number of positrons
The measured two lifetime components representing
s
1
(for
s
2
p-Ps with lifetime = 125 ps, and free and bound positrons with life-
time = 150–500 ps) and (for o-Ps with lifetimes > 900 ps) with
the associated formation probabilities I and I , respectively. Figs.
4 and 15 show the PAL parameters , I , and I as a function
of the type of CT complex. The relatively poor time resolution
ꢂ300 ps) of the used spectrometer makes the decomposition of
the shortest-lived lifetime component somewhat impossible.
The results show that the Ps was formed (I ) with a range of
2.0–34.1 for studied CT complexes. The Ps formation in these CT
2
s
2
s
2
2
,
1
2
4
1
s
1
,
s
2
1
2
s
1
1
(
annihilated in bulk or trapping centers, ranged from 303 ps to
344.2 ps and from 65.9% to 88.1%, respectively. The results show
s
1
two distinct groups. The QL and ZnCl
value and low I value, represent the first group. The second
group (Pi-OH, Br and SnCl complexes) has low value and high
value. Both groups are also defined using the calculated mean
2
CT complexes, with high
2
1
s
1
1
complexes with high intensities may be due to their Lewis base
that depends on the complex electronic configuration, and the lay-
2
4
s
1
I
1
ers between the donor and acceptor. The wide range of I
may be due to the different electron affinities of electron acceptors.
The lifetime component ascribed to the annihilation of o-Ps
2
value
lifetime. Each complex in the second group has distinguished prop-
erties that can affect the PAL parameters. These properties are the
high powerful acceptor of Pi-OH, vacant orbitals of SnCl , and high
4
s
2

4
76
A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
1
1
.2
.0
400
(A)
3
00
0
0
0
0
0
.8
.6
.4
.2
.0
200
1
00
0
1
00
0
0
.16
.14
(B)
8
0
0
0
0
0
0
0
0
.12
.10
.08
.06
.04
.02
.00
60
4
2
0
0
0
Pi-OH
QL
Bromine
CT complex
Zn(II)
Sn(IV)
4
5
6
7
8
9
10
11
12
ln F(Hz)
00
4
e ) at T = 306 K for Sn Cl (A) and
1
Fig. 15. The s lifetime component and its intensity for CT complexes.
Fig. 13. Frequency dependence of dielectric loss (
Zn Cl (B) charge-transfer complexes.
2
of bacteria was calculated, and the relative inhibition zone diame-
ter was calculated by normalizing the diameters of CT complex
with the diameter of the standard. Then, the linear correlation be-
tween the biological activity of CT complexes and the PAL param-
eters was calculated. The results indicate that the PAL components,
2
2
500
000
1
1
500
000
1
especially the short one (s , with linear correlation coeffi-
cient = 0.73), are affected by the biological activity of the CT com-
plex. Therefore, it can be used as a probe for the complex biological
activity. This observed correlation can be explained as follows:
firstly, the increasing the complex biological activity increases
the delocalized electrons over the whole chelating ring, and these
delocalized electrons affect the PAL parameters; secondly, the
dependence of the biological activity on the complex molecular
weight (linear correlation coefficient = -0.74) that already has a
strong correlation with the PAL parameters.
500
0
4
3
2
1
0
0
0
Conclusion
The positron annihilation lifetime parameters were found to be
dependent on the properties of the CT complex such as the accep-
tor power, number of layers between the donor and acceptor, do-
nor-to-acceptor molar ratio, and ionization potential of the
complexes. The molecular weight of the complex affects the mass
fraction of the donor component and consequently the fraction of
positrons annihilation in that part of the complex. The positron
annihilation lifetime components are affected by the biological
activity of the metal complex due to the increasing delocalized
electrons.
0
0
Pi-OH
QL
Bromine
CT complex
Zn(II)
Sn(IV)
Fig. 14. The o-Ps lifetime component and its intensity for CT complexes.
2
molecular weight of Br complexes. Also, the different ionization
potential of the complexes of both groups can be considered as a
factor for this classification.
Acknowledgement
This work was supported by grants from Taif University, Taif,
Saudi Arabia under project Grants No. 1103-432-1.
The results reveal that there are good positive or negative cor-
relations between all PAL parameters and the complex molecular
weight with the range of linear correlation coefficient = 0.73–
0
.88. This indicates that the molecular weight affects the mass
References
fraction of the donor component in the complex and consequently
the fraction of positrons annihilation in that part of the complex as
previously reported [17]. The average diameter of the inhibition
zone of the tetracycline and CT complexes against the four types
[
[
1] F.P. Fla, J. Palou, R. Valero, C.D. Hall, P. Speers, JCS Perkin Trans. 2 (1991) 1925.
2] T. Roy, K. Dutta, M.K. Nayek, A.K. Mukherjee, M. Banerjee, B.K. Seal, JCS Perkin
Trans. 2 (2000) 531.
[3] F. Yakuphanoglu, M. Arslan, Opt. Mater. 27 (2004) 29.

A.M.A. Adam et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 458–477
477
[
[
4] F. Yakuphanoglu, M. Arslan, Solid State Commun. 132 (2004) 229.
5] F. Yakuphanoglu, M. Arslan, M. Kucukislamoglu, M. Zengin, Sol. Energy 79
[24] National Committee for Clinical Laboratory Standards. Reference Method for
Broth Dilution Antifungal Susceptibility Testing of Conidium-Forming
Filamentous Fungi: Proposed Standard M38-A. NCCLS, Wayne, PA, USA, 2002.
[25] National Committee for Clinical Laboratory Standards, Methods for Antifungal
Disk Diffusion Susceptibility Testing of Yeast: Proposed Guideline M44-P,
NCCLS, Wayne, PA, USA, 2003.
[26] L.D. Liebowitz, H.R. Ashbee, E.G.V. Evans, Y. Chong, N. Mallatova, M. Zaidi, D.
Gibbs, Diagn. Microbiol. Infect. Dis. 4 (2001) 7.
[27] M.J. Matar, L. Ostrosky-Zeichner, V.L. Paetznick, J.R. Rodriguez, E. Chen, J.H.
Rex, Antimicrob. Agents Chemother. 47 (2003) 1647.
(
2005) 96.
6] B. Chakraborty, A.S. Mukherjee, B.K. Seal, Spectrochim. Acta Part A 57 (2001)
23.
7] A. Korolkovas, Essentials of Medical Chem, 2nd ed., Wiley, New York, 1998
Chapter 3).
8] K. Takahasi, K. Horino, T. Komura, K. Murata, Bull. Chem. Soc. Jpn. 66 (1993)
33.
9] S.M. Andrade, S.M.B. Costa, R. Pansu, J. Colloid Interface Sci. 226 (2000) 260.
[
[
[
[
2
(
7
[
10] A.M. Slifkin, Charge-Transfer Interaction of Biomolecules, Academic Press, New
York, 1971.
[28] D.A. Skoog, Principle of Instrumental Analysis, third ed., Saunders College
Publishing, New York, USA, 1985. 7.
[
[
[
11] F.M. Abou Attia, Farmaco 55 (2000) 659.
12] K. Basavaiah, Farmaco 59 (2004) 315.
13] J.C. Machado, G.M. de Lima, F.C. Oliveira, I.M. Marzano, Chem. Phys. Lett. 418
[29] R. Abu-Eittah, F. Al-Sugeir, Can. J. Chem. 54 (1976) 3705.
[30] A. El-Kourashy, Spectrochim. Acta 37A (1981) 399.
[31] H. Tsubomura, R.P. Lang, J. Am. Chem. Soc. 86 (1964) 3930.
[32] S.M. Teleb, M.S. Refat, Spectrochim. Acta Part A 60 (7) (2004) 1579.
[33] E.M. Nour, S.M. Teleb, M.A.F. El-Mosallamy, M.S. Refat, S. Afr. J. Chem. 56
(2003) 10.
[34] R. Rathone, S.V. Lindeman, J.K. Kochi, J. Am. Chem. Soc. 119 (1997) 9393.
[35] G. Aloisi, S. Pignataro, J. Chem. Soc. Faraday Trans. 69 (1972) 534.
[36] G. Briegleb, Z. Angew. Chem. 72 (1960) 401;
(
2006) 292.
[
[
[
[
14] Marques-Netto, C.F. Carvalho, C.A. Alves de Carvalho, R.D. Sinisterra, H.F. Brito,
J.C. Machado, Chem. Phys. Lett. 333 (2001) 371.
15] A.M.A. El-Sayed, H.F.M. Mohamed, A.A.A. Boraei, Radiat. Phys. Chem. 58 (2000)
7
91.
16] D.M. Schrader, Y.C. Jean, Studies in Physical and Theoretical Chemistry 57:
Positron and Positronium Chemistry, Elsevier, Amsterdam, 1986.
17] W. Brandt, A. Dupasquier (Eds.), Positron Solid-State Physics, North-Holland,
Amsterdam, 1983.
G. Briegleb, Z. Angew. Chem. 76 (1964) 326.
[37] G. Briegleb, J. Czekalla, Z. Physikchem, Frankfurt 24 (1960) 237.
[38] A.N. Martin, J. Swarbrick, A. Cammarata, Physical Pharmacy, Lee, Febiger, third
ed., Philadelphia, PA, 1969, 344.
[
[
[
[
18] T. Sharshar, M.L. Hussein, Nucl. Instr. Meth. A 546 (2005) 584.
19] J. Kansy, Nucl. Instr. Meth. A 374 (1996) 235.
20] A.W. Bauer, W.M. Kirby, C. Sherris, M. Turck, Am. J. Clin. Pathol. 45 (1966) 493.
21] M.A. Pfaller, L. Burmeister, M.A. Bartlett, M.G. Rinaldi, J. Clin. Microbiol. 26
[39] W. Kiefer, H.J. Bernstein, Chem. Phys. Lett. 16 (1972) 5.
[40] L. Andrews, E.S. Prochaska, A. Loewenschuss, Inorg. Chem. 19 (1980) 463.
[41] K. Kaya, N. Mikami, Y. Udagawa, M. Ito, Chem. Phys. Lett. 16 (1972) 151.
[42] A.G. Maki, R. Forneris, Spectrochim. Acta 23A (1967) 867.
[43] F.W. Parrett, N.J. Taylor, J. Inorg. Nucl. Chem. 32 (1970) 2458.
[44] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, Parts A and B, John Wiley & Sons, New York, 1997.
[45] R. Shirley, The CRYSFIRE powder indexing system, <http://www.ccp14.ac.uk/
tutorial/crys/obtain.htm>.
(
1988) 1437.
[
[
22] National Committee for Clinical Laboratory Standards, Performance Vol.
antimicrobial susceptibility of Flavobacteria, 1997.
23] National Committee for Clinical Laboratory Standards, Methods for dilution
antimicrobial susceptibility tests for bacteria that grow aerobically, Approved
standard M7–A3, National Committee for Clinical Laboratory Standards,
Villanova, Pa, 1993.