Spectroscopic studies of the hydrogen bonded charge transfer complex of 2-aminopyridine with π-acceptor chloranilic acid in different polar solvents

Article abstract of DOI:10.1016/j.molliq.2011.06.015

Hydrogen bonded charge transfer complex (HBCT) between 2-aminopyridine (2AP) as electron donor, hydrogen bond acceptor, with chloranilic acid (CHA) as the π-electron acceptor, hydrogen bond donor, has been studied spectrophotometrically in the polar solvents acetonitrile (AN), methanol (MeOH) and ethanol (EtOH). The stoichiometry of the complex has been identified by Job's and photometric titration methods to be 1:1. The Benesi-Hildebrand equation has been applied to estimate the formation constant (K_CT) and molar extinction coefficient (ε). It was found that the value of K _CT is larger in methanol than those in acetonitrile or ethanol. The results were interpreted in terms of Kamlet-Taft α and β solvent parameters. Furthermore, the data were analyzed in terms of standard free energy change (ΔG°), oscillator strength (f), dissociation energy (W), transition dipole moment (μ) and ionization potential (I_P). Also, the solid HBCT-complex was synthesized and characterized by using elemental analysis and FTIR spectroscopy.

Full text of DOI:10.1016/j.molliq.2011.06.015

Journal of Molecular Liquids 162 (2011) 129–134
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Spectroscopic studies of the hydrogen bonded charge transfer complex of
2-aminopyridine with π-acceptor chloranilic acid in different polar solvents
a
Khairia M. Al-Ahmary a, Moustafa M. Habeeb b, , Eman A. Al-Solmy
⁎
a
Chemistry Department, Faculty of Science, King Abdul-Aziz University, Jeddah, Saudi Arabia
Chemistry Department, Faculty of Education, Alexandria University, Alexandria, Egypt
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Hydrogen bonded charge transfer complex (HBCT) between 2-aminopyridine (2AP) as electron donor,
hydrogen bond acceptor, with chloranilic acid (CHA) as the π-electron acceptor, hydrogen bond donor, has
been studied spectrophotometrically in the polar solvents acetonitrile (AN), methanol (MeOH) and ethanol
(EtOH). The stoichiometry of the complex has been identified by Job's and photometric titration methods to
be 1:1. The Benesi–Hildebrand equation has been applied to estimate the formation constant (KCT) and molar
extinction coefficient (ε). It was found that the value of KCT is larger in methanol than those in acetonitrile or
ethanol. The results were interpreted in terms of Kamlet–Taft α and β solvent parameters. Furthermore, the
data were analyzed in terms of standard free energy change (ΔG°), oscillator strength (f), dissociation energy
(W), transition dipole moment (μ) and ionization potential (IP). Also, the solid HBCT-complex was
synthesized and characterized by using elemental analysis and FTIR spectroscopy.
Received 26 March 2011
Received in revised form 9 June 2011
Accepted 26 June 2011
Available online 19 July 2011
Keywords:
2-Aminopyridine
Chloranilic acid
UV–vis
FTIR
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
steroided antiflammatory drugs that used in musculo-skeletal and
joint disorders [26]. Moreover, aminopyridines are commonly present
Proton or electron transfer complexes play an important role in the
field of magnetic, electrical conductivity and optical properties [1–5].
A great number of charge transfer receptors have been reported under
the basic construction strategy of employing hydrogen bonding [6–8].
Recent investigations have shown that hydrogen bonds could work as
efficient bridges to mediate electron transfer between bonded species
and initiate the so-called proton coupled electron transfer [9–12].
Generally, CT-interaction between benzoquinones electron accep-
tors and electron donors containing nitrogen, oxygen or sulfur atoms
has been reported over the last years.
These types of interactions play an important role in the field of
drug-receptors binding mechanism [13,14], surface chemistry [15],
applications in solar energy storage [16], uses as organic supercon-
ductors [17], and in many biological fields as antibacterial and
antifungal agents [18–20].
Aminopyridines are bioactive N-heterocyclic amines, which in-
crease the strength of the nerve signal by blocking of the voltage-
dependent K+ channel [21,22]. Also, aminopyridines have been
proposed as drugs for the treatment of many diseases such as
myocardial infarction as antithrombus agents and diarrhea as
antimicrobial agents [23–25]. In particular, 2-aminopyridine is one
of the potential impurities in piroxicam and teroxicam which are non-
in synthetic and natural products [27]. They form repeated moiety in
many large molecules with interesting photophysical, electrochemical
and catalytic applications [28].
In connection with our work on electron or proton transfer
complexes [29–34], and due to the biological and pharmaceutical
applications of aminopyridines, this article presents our results on
spectroscopic studies of the hydrogen bonded charge transfer
complex between 2-aminopyridine with chloranilic acid (Scheme 1)
in the different polar solvents acetonitrile, methanol and ethanol. The
molecular composition of the complex was studied using Job's and
photometric titration methods. The formation constant (KCT), molar
extinction coefficient (ε), standard free energy change (ΔG°),
oscillator strength (f), transition dipole moment (μ), ionization
potential (IP) and dissociation energy (W) of the formed HBCT-
complex were estimated and evaluated. In addition, the solid HBCT-
complex was isolated and characterized using elemental analyses and
infrared measurements.
2. Experimental
2.1. Physical measurements and chemicals
2.1.1. Electronic spectra
The electronic spectra were recorded in the region 700–250 nm
using UV–vis Shimadzu UV-1601 spectrophotometer connected to
Shimadzu TCC-ZUOA temperature controller unit (Japan).
⁎
Corresponding author.
E-mail address: mostafah2002@yahoo.com (M.M. Habeeb).
0167-7322/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molliq.2011.06.015

130
K.M. Al-Ahmary et al. / Journal of Molecular Liquids 162 (2011) 129–134
Polar solvent
(2AP–CHA)
2 AP + CHA
2AP•+ CHA•–
Radical ions
Donor Acceptor
n—π, π – π complex
Scheme 2. Formation of CHA radical anion.
displays any measurable absorption in the region 450–600 nm, the
resulting HBCT-complex shows strong absorption band centered at
519, 530 and 541 nm in AN, MeOH and EtOH, respectively. These
absorptions are associated with the strong change in color observed
upon mixing of the reactants (pink from colorless solutions in the
different polar solvents). These reflect the electronic transitions in the
formed HBCT-complex. It is important to report that the π-electronic
spectra were scanned against the same electronic acceptor concen-
tration to eliminate the possible overlap that may arise between
HBCT-complex and CHA bands. Moreover, it is worth mentioning that
the formed new long wave length absorption bands are attributed to
the formation of CHA radical anion resulting from complete transfer of
charge from 2AP to CHA (Scheme 2). The radical anion nature of
benzoquinones has been confirmed by electron spin-resonance
spectral measurements [35].
Scheme 1. Chemical structures of 2AP and CHA.
2.1.2. Infrared spectra
The infrared spectra were recorded as KBr disks on Bruker FTIR-
Tensor 37 Fourier transform infrared spectrophotometer (USA),
evacuated to avoid water and CO2 absorption.
2.1.3. Elemental analyses
C, H and N contents were determined with the Micro analyzer
Perkin Elmer 2400 (USA).
3.2. Effect of CHA concentration, reaction time and temperature on HBCT
complex formation
2.1.4. Chemicals
All chemicals used were of analytical grade. 2-aminopyridine was
supplied by Acros Organics, chloranilic acid was supplied by Fluka.
Acetonitrile, methanol and ethanol were purchased from PAI-ACS. KBr
was spectroscopic grade supplied by Aldrich.
The effect of CHA concentration was studied by following the
absorbance of the HBCT-complex between varied amounts of
5×10−3 M CHA with 1 mL of 2×10−3 M 2AP in 10 mL calibrated
flasks and diluted to the mark with solvent. It has been found that
maximum constant absorbance of the HBCT-complex was obtained
with 1 mL of 5×10−3 M CHA. The higher concentration of CHA causes
negligible increase in absorbance. On the other hand, higher
concentration of CHA may be useful to facilitate completion of the
HBCT-complex that leads to minimize the required time for retaining
the maximum absorbance at the corresponding wavelength.
2.2. Synthesis of the solid 1:1 HBCT-complex
The solid HBCT-complex (1:1) between 2AP and CHA was
prepared by mixing equimolar amounts of 2AP with CHA in
acetonitrile. The resulting complex solution was allowed to evaporate
slowly at room temperature where the complex was isolated as pink
crystals. The separated complex was filtered off, washed well with
acetonirile and dried over calcium chloride for 24 h. Anal. Calc. for
(2AP-CHA) C11H8N2Cl2O4 complex: C, 43.59%; H, 2.64%; N, 9.24%.
Found: C, 43.64%; H, 3.05%; N, 9.29%. MP. 207–209 °C.
The effect of time on the HBCT-reaction was studied by following
the effect of time on the HBCT-complex produced by mixing
2×10−4 M from each of 2AN and CHA in the different solvents. It
has been found that the absorbance of the HBCT-complex reached
maximum and constant value instantly in the different solvents
confirming that the time has no effect on the complex absorbance. In
addition, the formed HBCT-complex was stable for 2 h (Table 1).
The effect of temperature was monitored by following the
3. Results and discussion
3.1. Electronic spectra
absorbance of the HBCT-complex resulting by mixing 5×10−4
M
Fig. 1 shows the electronic absorption spectra of 2AP, CHA and
HBCT-complex in ethanol. While none of the reactants spectra
CHA with different concentrations of 2AP at different temperatures
(20–40 °C). It has been found that the formed HBCT-complex was
stable in the selected range at different 2AP concentrations as can be
understood from its constant absorbance at different temperatures
(Fig. 2). It seems that the extra stability of the formed complex through
hydrogen bonding is presumably attributed to its high stability in the
selected temperature range.
0.5
EtOH
C
0.4
0.3
0.2
Table 1
Effect of time on the absorbance of 1:1 HBCT-complex.
Absorbance
0.1
Time
AN
MeOH
EtOH
B
0
0.342
0.341
0.339
0.338
0.336
0.336
0.331
0.224
0.223
0.222
0.221
0.219
0.218
0.218
0.265
0.263
0.262
0.259
0.257
0.255
0.252
A
20
40
60
80
100
120
0.0
350
450
550
650
750
Wavelength (nm)
Fig. 1. Electronic spectra: (A) 2×10− 4
M
(2AP), (B) 2×10− 4
M
(CHA) and
(C) [5×10−4 M (2AP)+5×10−4 M (CHA)] in ethanol.

K.M. Al-Ahmary et al. / Journal of Molecular Liquids 162 (2011) 129–134
131
20°C
25°C
30°C
35°C
40°C
0.8
0.6
0.4
0.2
0.0
0.4
0.3
0.2
0.1
0.0
AN
MeOH
EtOH
Conc. of 2AP [M]
Fig. 2. Effect of temperature on the absorbance of HBCT-complex at different
concentrations of 2AP in methanol.
0.0
0.5
1.0
1.5
2.0
2.5
CCHA/C2AP
3.3. Stoichiometric ratio of the formed HBCT-complex
Fig. 4. Photometric titration plots of HBCT-complex in different solvents.
The composition of the formed HBCT-complex was determined by
applying Job's method of continuous variations [36] and photometric
titrations [37]. Fig. 3 represents the continuous variation plot where
maximum absorbance was recorded at 0.5 mol fraction indicating 1:1
HBCT-complex formation (2AP:CHA). Fig. 4 represents the photo-
metric titrations where two straight lines were produced intercepting
at 1:1 ratio (2AP: CHA). Accordingly, one can conclude from Figs. 3
and 4 that the HBCT-complex is formed based on a 1:1 stoichiometric
ratio (2AP: CHA).
finding of the formation of 1:1 complex (Fig. 5). In the plots, the slope
and intercept equal 1/ε and 1/ε KCT, respectively. The solvent
parameters and the values of KCT, ε and λmax. are compiled in Table 2.
An important finding from Table 2 is the highest value of KCT in
methanol compared with those in acetonitrile or ethanol. This result
could be interpreted based on the high value of the hydrogen bond
donor parameter α of methanol, 0.98 [39]. This leads to solvation of
CHA through hydrogen bond formation between methanol OH and
the carbonyl groups of CHA. This increases the electronic accepting
ability of CHA and hence KCT increases. The small value of KCT in
acetonitrile could be explained in terms of its high value of the
3.4. Formation constant of HBCT-complex
⁎
polarizability parameter π , 0.75 [39]. Consequently, acetonitrile
molecules can form a dimer through self association owing to strong
dipole–dipole interaction between these molecules leading to a small
Based on the electronic spectra of the HBCT-complex at various
2AP concentrations, KCT and ε were calculated using the modified
Benesi–Hildebrand equation [38]
effective dipole moment and synergistic behavior that decreases KCT
.
∘
∘
∘
∘
It is also observed in Table 2, the smallest value of KCT in ethanol
which could be rationalized based on the similar values of the
hydrogen bond donor and acceptor parameters (α and β) 0.83 and
0.77 of ethanol [40]. Hence, ethanol molecules exhibit dual functions
through solvation of both CHA and 2AP by hydrogen bonding
interactions. The situation produces high steric hindrance leading to
the smallest value of KCT in ethanol.
C
dC a = A = 1= KCTε + ðC d + C aÞ= ε
ð1Þ
where C°d and C°a are the initial concentrations of the electron donor
and electron acceptor, respectively, and A is the absorbance of the
CT-band. It is worth to mention that the maximum added 2AP
concentration is approximately equal to the concentration of CHA and
the calculated equilibrium constants are subjected to significant
systematic errors due to the method used. Furthermore, the excess of
2AP concentration led to a decrease in the complex absorbance. This
situation could be interpreted based on the high interaction between
2AP (pKa=6.68) and solvents or the association of 2AP molecules
through hydrogen bonding. These produce high steric hindrance
leading to destabilizing the formed complex.
3.5. Calculation of the oscillator strength and the transition dipole moment
The oscillator strength (f) is a dimensionless quantity which used
to express the transition probability of the CT-band [41] and the
transition dipole moment (μ) of the HBCT-complex [42]. The
Plotting C°dC°a/A versus (C°d +C°a) for the formed HBCT-complex
in the different solvents, straight lines were obtained supporting our
8e-7
7e-7
6e-7
5e-7
1.5
AN
1.2
0.9
0.6
0.3
0.0
4e-7
AN
MeOH
EtOH
3e-7
2e-7
0.0005 0.0006 0.0007 0.0008 0.0009 0.0010 0.0011
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Mole fraction of CHA
OCHA + CO2AP
C
Fig. 3. Job's plots of HBCT-complex in acetonitrile.
Fig. 5. Benesi–Hildebrand plots of 1:1 HBCT-complex in different solvents.

132
K.M. Al-Ahmary et al. / Journal of Molecular Liquids 162 (2011) 129–134
1.4
Table 2
Solvent parameters, Formation constant, molar extinction coefficient and wavelength
1.2
1.0
0.8
0.6
0.4
0.2
0.0
of 1:1 HBCT-complex in different solvents.
Solvent
α
β
Π
K
CT ×10−3
ε×10−3
λmax
⁎
L mol−1
L mol−1 cm−1
nm
AN
MeOH
EtOH
0.19
0.98
0.83
0.31
0.62
0.77
0.75
0.6
0.54
1.99
3.17
0.79
3.46
2.03
3.55
519
530
541
AN
MeOH
EtOH
following expressions [43] are commonly used to calculate f and μ. The
results are compiled in Table 3.
h
i
f = 4:32 × 10−9
ε
max:Δν1=2
ð2Þ
ð3Þ
0
20
40
60
80
100
C2AP / μgml-1
h
i
1=2
Fig. 6. Beer's law curves of 1:1 HBCT-complex in different solvents.
μ = 0:0958
ε max:Δν1=2 =ν max:
where Δν1/2 is the half band width of absorbance, εmax. and νmax. are
the molar extinction coefficient and wave number at the maximum
absorption of the complex, respectively.
respectively, and the EA of CHA is 1.1 eV [45]. ECT, mean values of IP,
ΔG° and W are collected in Table 3.
It is evident from Table 3 that the formed HBCT-complex is
characterized by relatively high values of both the oscillator strength
and transition dipole moment. This confirms the charge transfer from
2AP to CHA to form the pink colored free radical anion of CHA.
The data in Table 3 clearly refer that the ionization potentials of the
formed HBCT-complex are the same in the different solvents,
confirming same overlapping molecular orbital between 2AP with
CHA. In addition, the IP has no effect on the stability of the formed
HBCT-complex.
The calculated values of the dissociation energy (W) of the HBCT-
complex in the different solvents are constant suggesting that the
investigated complex is reasonably strong and stable under the studied
conditions with high resonance stabilizing energy [50].
Furthermore, the negative values of the free energy change (ΔG°)
listed in Table 2 suggest the simultaneous production of the formed
HBCT-complex. Generally, the values of ΔG° given in Table 3 become
more negative as the value of KCT increases. As the bond between the
donor and acceptor becomes stronger and thus the components are
subjected to more physical strain or loss freedom, the values of ΔG°
become more negative.
3.6. Calculation of the standard free energy change and dissociation
energy
The standard free energy change of complexation (ΔG°) was
calculated from the formation constant (KCT) according to the
following equation [44]
∘
ΔG = −2:303RT log KCT
ð4Þ
where ΔG° is the free energy change of the complex (kJ mol−1), R the
gas constant (8.314 J mol− 1 K), T is the absolute temperature
(273+°C) and KCT is the formation constant of the HBCT-complex at
25 °C.
The dissociation energy (W) of the formed HBCT-complex was
calculated from the corresponding CT energy (ECT), ionization
potential of the donor (IP) and electron affinity of the acceptor (EA)
using the relationship [45]
ECT = IP–EA–W:
ð5Þ
3.7. Application of the studied HBCT-reaction
The energy of the π–π* interaction (ECT) is calculated using the
following equation [46]
Based on the formation of colored HBCT-complex between 2AP
and CHA in the studied polar solvents, we propose in this section a
ECT = 1243:667= λCTnm
ð6Þ
Table 4
whereas, λCT is the wavelength of the CT-band of the formed complex.
The ionization potential values of the donors are calculated by using
Eq. (7)
Quantitative parameters of 1:1 HBCT-complex in different solvents.
Parameter
AN
MeOH
EtOH
Beer's law limits,
μg mL−1
1.88–94.12
1.88–94.12
1.88–94.12
IP = a + bðhνmax:
Þ
ð7Þ
Limit of detection,
0.52
0.86
0.68
μg mL−1
Limit of quantification, 1.75
2.86
2.28
where hνmax. is the π–π* transition energy in electron volts eV, a and b
are 5.11 and 0.701 [47], 4.39 and 0.857 [48] or 5.156 and 0.778 [49],
μg mL−1
⁎
⁎
⁎
Regression equation
Y
=0.0130X+
Y
=0.0108X−
Y
=0.0099X+
0.0079
0.0286
0.0199
Intercept, a
Slope, b
Confidence interval
of intercept, α
Confidence interval
of slope, β
0.0079
0.0130
0.0079 0.0011
−0.0286
0.0108
−0.0286
0.0015
0.0199
0.0099
0.0199 0.0015
Table 3
Energy, ionization potential, dissociation energy, frees energy, oscillator strength and
transition dipole moment of 1:1 HBCT-complex in different solvents.
0.0130 7.4×10−5 0.0108 0.0001 0.0099 0.0001
Solvent ECT (eV) IP (eV) W (eV) −ΔG° (K.J.mol−1
)
f
μ (Debye)
AN
MeOH
EtOH
2.40
2.34
2.30
8.00
7.94
7.90
4.50
4.50
4.50
18.79
19.95
16.51
0.73 8.98
0.47 7.28
0.47 7.38
Correlation
0.9997
0.9991
0.9989
coefficient, R2
Y is the absorbance and X is the concentration in μg mL−1
.
⁎

K.M. Al-Ahmary et al. / Journal of Molecular Liquids 162 (2011) 129–134
133
Table 5
Precision and accuracy.
tS
pffiffiffi
n
Solvent
AN
Amount taken μg mL−1
Amount found μg mL−1
Rec. %
X
SD
RSD
jX−μj
Confidence limits
23.53
32.94
51.77
70.59
80.00
14.12
32.94
42.35
70.59
80.00
32.94
42.35
51.77
61.18
80.00
23.31
32.96
52.79
70.53
79.10
14.46
31.84
40.76
72.36
82.95
33.51
42.56
53.13
61.78
79.08
99.07
100.04
101.97
99.92
98.87
102.44
96.66
99.97
1.2275
1.2278
0.03
1.41
4.42
1.76
99.97 1.41
100.31 4.42
100.94 1.76
MeOH
EtOH
100.31
100.94
3.56
1.42
3.55
1.40
0.31
0.94
96.25
102.51
103.69
101.72
100.49
102.63
100.98
98.85
t=2.776 for n=5 at 95% confidence level.
SD = standard deviation.
RSD = relative standard deviation.
simple, rapid and accurate spectrophotometric method for determi-
nation of 2AP. Under the optimum reaction conditions Beer's plots at
various 1:1 molar ratios between 2AP and CHA were constructed
(Fig. 6). The regression equation in the different solvents was
calculated by the least square method. In all cases Beer's law plots
were linear with very small intercepts and slopes and good
correlation coefficients in the general concentration range
2–94 μg ml−1 (Table 4). The limits of detection and quantification
were calculated according to the IUPAC definition [51]. The calculated
values were listed in Table 4. They recorded small values confirming
high accuracy of the method. It has been found also that the values of
the confidence intervals of intercept α, and slope β recorded small
values confirming excellent linearity between the absorbance and
concentration. The accuracy of the method was established by
performing analysis of solutions containing five different amounts
(within Beer's law limits) of 2AP and measuring the absorbance of
their HBCT-complexes with CHA in different solvents. The concen-
tration of 2AP was determined from the regression equation and then
calculated the recovery percentages, the standard deviation S, and
relative standard deviation RSD. The recovery percentage ranged from
99.71 to 100.94 with RSD ranging from 1.12 to 1.40 confirming high
accuracy and precision of the proposed method (Table 5).
3.8. Infrared spectra
The formation of 1:1 HBCT-complex between 2AP and CHA was
confirmed from a comparison of the infrared spectra of complex with
those of 2AP or CHA. The infrared spectrum of the HBCT-complex is
shown in Fig. 7 where the asymmetric and symmetric stretching
vibrations of the amino group were weakened and shifted to 3393 and
3208 cm−1 compared with 3444 and 3290 cm−1 for 2AP. This
confirms the formation of a hydrogen bonding between the amino
group of 2AP and the OH of CHA. It is worth to mention that chloranilic
acid is a dibasic acid (pK1 =1.07 and pK2 =2.24) [53,54], hence a
proton transfer hydrogen bonding is expected to occur between the
amino group and the more acidic OH of CHA. Returning to Fig. 7 one
can observe a weak band at 2850 cm−1 which can be interpreted as
due to ν (NH+) stretching vibration. Consequently, the formed charge
transfer complex is extra stabilized through bifurcated hydrogen
bonding as shown in Scheme 3. The formation of the HBCT-complex is
further confirmed from the shifts of its vibrational bands compared
with 2AP and CHA. The carbonyl stretching vibrational band ν(C_O)
is shifted to 1665 cm−1 compared with 1661 cm−1 for CHA, also
ν(C_C) for the complex is recorded at 1629 cm−1 compared with
1627 cm−1 for 2AP. The recorded band at 1544 cm−1 in Fig. 7 could
be assigned to in-plane bending δ(OH) overlapping with ν(C_N) of
2AP moiety that found at 1595 cm−1 for 2AP. In addition, ν(C\Cl)
Comparison of the difference between the mean and true value
(X− −μ) with the largest difference that could be expected as a result
of indeterminate error ( tS/√n) [52] has been carried out and the
results were collected in Table 5. It has been found that (X− −μ) were
less than tS/√n indicating that no significant difference between the
mean and true value is existed.
85
80
75
70
65
60
55
50
3500
3000
2500
2000
1500
1000
500
Wavenumber cm-1
Fig. 7. FTIR spectrum of 1:1 HBCT-complex in the range 4000–400 cm−1
.
Scheme 3. Structure of crystalline HBCT-complex.

134
K.M. Al-Ahmary et al. / Journal of Molecular Liquids 162 (2011) 129–134
[14] R. Mandal, S.C. Lahiri, J. Indian Chem. Soc. 76 (1999) 347.
[15] S.M. Andrade, S.M.B. Costa, R. Pansu, J. Colloid Interface Sci. 226 (2000) 260.
[16] K. Takahasi, K. Horino, T. Komura, K. Murata, Bull. Chem. Soc. Jpn. 66 (1993) 733.
[17] A. Eychmuller, A.I. Rogach, Pure Appl. Chem. 72 (2000) 179.
[18] H. Salem, J. Pharm. Biomed. Anal. 29 (2002) 527.
vibrational bands of the HBCT-complex were found at 838 and
761 cm−1 compared with 839 and 782 cm−1 for CHA. Furthermore,
the ring vibrational bands at 576, 555, 513 cm−1 were further
confirmed the formation of a bifurcated hydrogen bond in the HBCT-
complex (2AP-CHA) [55,56].
[19] A.M. Slifkin, Charge Transfer Interaction of Biomolecules, Academic Press, New
York, 1971.
[20] L.B. Kiev, Molecular Orbital Theory in Drug Research, Academic Press, New York,
1971.
[21] J. Melgo, M. Lemeignan, F. Peradejordi, P. Lechat, J. Pharmacol. (Paris) 16 (Suppl.
II) (1985) 109.
[22] C. Carlsoom, I. Rosen, E. Nilsson, Acta Anaesthesiol. Scand. 27 (1993) 87.
[23] J.I. Segal, B.S. Brunnemann, Pharmacotherapy 17 (1997) 415.
[24] A.G. Amr, A.M. Mohamed, S.F. Mohamed, N.A. Abdel-Hafez, A. Hammam, Bioorg.
Med. Chem. 14 (2006) 5488.
[25] I.O. Zhuravel, S.M. Kovalenko, A.V. Ivachtchenko, K.V. Balakin, V. Kazmirchuk,
Bioorg. Med. Chem. Lett. 5 (2005) 5483.
4. Conclusion
1- 2AP reacts instantly with CHA to form HBCT-complex in different
polar solvent.
2- Job's method of continuous variation and photometric titration
methods confirmed the formation of 1:1 HBCT-complex.
3- KCT of HBCT-complex in different polar solvents were estimated
where KCT recorded large value in methanol compared with
ethanol and acetonitrile.
[26] K. Parfitt, S.C. Sweetman, P.S. Blake, A.V. Parsons, Martindale, The Extra
Pharmacopoeia, 32nd ed, Phamaceutical Press, London, 1999, p. 80, 88.
[27] A. Goel, V.J. Ram, Tetrahedron 65 (2009) 7865.
4- The results were interpreted based on Kamlet–Taft solvent
parameters.
5- The solid HBCT-complex was isolated and characterized using
elemental analysis and infrared spectroscopy.
6- The formed HBCT-complex included bifurcated hydrogen bonded
proton transfer between OH of CHA and both the amino and ring
nitrogen of 2AP.
[28] N.A. Al-Hashimy, Y.A. Hussein, Spectrochim. Acta A 75 (2010) 198.
[29] M.M. Habeeb, A.S. Al-Attas, M.T. Basha, J. Mol. Liq. 150 (2009) 56.
[30] M.M. Habeeb, R.M. Alghanmi, JCED 55 (2010) 930.
[31] K.M. Al-Ahmary, M.M. Habeeb, E.A. Al-Solmy, J. Solution Chem. 39 (2010) 1264.
[32] A.S. Al-Attas, M.M. Habeeb, D.S. Al-Raimi, J. Mol. Liq. 148 (2009) 58.
[33] A.S. Al-Attas, M.M. Habeeb, D.S. Al-Raimi, J. Mol. Struct. 928 (2009) 158.
[34] K.M. Al-Ahmary, M.M. Habeeb, E.A. Al-Solmy, J. Mol. Liq. 158 (2011) 161.
[35] M.E. Abdel-Hamid, M. Abdel-Salam, M.S. Mahrous, M.M. Abdel-Khalek, Talanta 32
(1985) 1000.
[36] P. Job, Advanced Physicochemical Experimental: London, , 1964.
[37] D.A. Skoog, Principal of Instrumental Analysis, 3rd ed. Sunder College Publisher,
New York, 1985.
[38] H. Benesi, J. Hildebrand, J. Am. Chem. Soc. 71 (1949) 2703.
[39] N.S. Moyon, A.K. Chandra, S. Mitra, J. Phys. Chem. A114 (2010) 60.
[40] K.A. Connors, Chemical Kinetics, The Study of Reaction Rate in Solution, VCH
Publishers, Inc, 1990.
[41] A.B.P. Leve, Inorganic Electronic Spectroscopy, second ed., Elsevier, Amsterdam,
1985, p. 161.
[42] H. Tsubomura, R. Lang, J. Am. Chem. Soc. 86 (1964) 3930.
[43] R. Rathone, S.V. Linderman, J.K. Kochi, J. Am. Chem. Soc. 119 (1997) 9393.
[44] W.B. Person, J. Am. Chem. Soc. 84 (1962) 536.
7- Based on the simple composition of the formed HBCT-complex and
its instantaneous production, a rapid and accurate spectrophoto-
metric method for analysis of 2AP was suggested.
8- Beer's law was obeyed in the concentration range 2–94 μg ml−1
.
9- The recovery percentages ranged from 99.71 to 100.94 with
relative standard deviation ranged from 1.12 to 1.40 confirming
high accuracy and precision of the proposed method.
References
[45] H.M. McConnel, J.J. Ham, J.R. Platt, J. Chem. Phys. 21 (1964) 66.
[46] G. Briegleb, Z. Angew Chem. 76 (1964) 326.
[47] D.C. Wheat, Hand Book of Chemistry and Physics, fifteenth ed., CRC, 1969–1970.
[48] A.F. Mosten, J. Chem. Phys. 24 (1956) 602.
[49] S.R. Becker, F.W. Worth, J. Am. Chem. Soc. 84 (1962) 4263.
[50] M. Pandeeswaran, K.P. Elango, Spectrochim. Acta A 65 (2006) 1148.
[51] M.H. Irving, T.S. Freiser, West. IUPAC Compendium of Analytical Nomenclature
Definitive Rules, Pergamon Press, Oxford, 1981.
[52] J.C. Miller, N.A. Miller, Statistics for Analytical Chemistry, second ed. Ellis Horwood
Ltd, England, 1988.
[53] M.M. Habeeb, H.A. Alwakil, A. El-Dissouky, H. Abdel-Fattah, Pol. J. Chem. 69 (1995)
1428.
[54] G.H. Gohar, M.M. Habeeb, Spectroscopy 14 (2000) 99.
[55] J. Kalenik, I. Majerz, L. Sobczyk, E. Grech, M.M. Habeeb, J. Chem. Soc., Faraday
Trans. 1 85 (1989) 3187.
[1] A. Weller, K. Zachariasse, J. Chem. Phys. 46 (1967) 4904.
[2] R.K. Gupta, R.A. Sing, J. Appl. Sci. 5 (2005) 28.
[3] H.A. Hashem, M.S. Refat, Surf. Rev. Lett. 13 (2006).
[4] A. Tracz, Polym. J. Chem. 76 (2002) 457.
[5] I.M. Ishaat, A. Ahmed, Spectrochim. Acta A 77 (2010) 437.
[6] M.A. Hossain, J.M. Linares, D. Powell, K. Bouman-james, Inorg. Chem. 40 (2001)
2936.
[7] K.H. Lee, J.I. Hong, Tetrahedron Lett. 41 (2000) 6083.
[8] G. Hennrich, H. Sonnenschein, U. Reschgenger, Tetrahedron Lett. 42 (2001) 2805.
[9] I.V. Kuvykin, V.V. Ptushenko, A.V. Vershubskii, A.N. Tikhonov, Biochim. Biophys.
Acta, Bioenerg. 1807 (2011) 336.
[10] H. Ozawa, T. Hino, H. Ohtsu, T. Wada, K. Tanaka, Inorg. Chim. Acta 366 (2011) 298.
[11] R. Vinu, S. Polisetti, G. Madras, Chem. Eng. J. 165 (2010) 784.
[12] C.J. Corcoran, H. Tavassol, M.A. Rigsby, P.S. Bagus, A. Wieckowski, J. Power Sources
195 (2010) 7856.
[13] A. Kololkovas, Essentials of Medicinal Chemistry, second ed. Wiley, New York,
1998 (Chapter 3).
[56] J. Kalenik, I. Majerz, L. Sobczyk, E. Grech, M.M. Habeeb, Collect. Czech. Chem.
Commun. 55 (1990) 80.