Proton transfer complexes based on some π-acceptors having acidic protons with 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one donor: Synthesis and spectroscopic characterizations

Article abstract of DOI:10.1016/j.molstruc.2011.04.001

Charge transfer complexes based on 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4- triazin-5(4H)-one (ArNH₂) organic basic donor and pi-acceptors having acidic protons such as picric acid (PiA), hydroquinone (Q(OH)₂) and 3,5-dinitrobenzene (DN

Full text of DOI:10.1016/j.molstruc.2011.04.001

Journal of Molecular Structure 995 (2011) 116–124
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Proton transfer complexes based on some
p-acceptors having acidic protons with
3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one donor: Synthesis
and spectroscopic characterizations
Moamen S. Refat a,b, , Hosam A. Saad b,c, Abdel Majid A. Adam b
⇑
a Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
b Department of Chemistry, Faculty of Science, Taif University, 888 Taif, Saudi Arabia
c Department of Chemistry, Faculty of Science, Zagazig University, Zagazig, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Charge transfer complexes based on 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one (ArNH2)
organic basic donor and pi-acceptors having acidic protons such as picric acid (PiA), hydroquinone
(Q(OH)2) and 3,5-dinitrobenzene (DNB) have been synthesized and spectroscopically studied. The
ANHþ3 ammonium ion was formed under the acid–base theory through proton transfer from an acidic
to basic centers in all charge transfer complexes resulted. The values of formation constant (KCT) and
Received 14 February 2011
Received in revised form 31 March 2011
Accepted 1 April 2011
Available online 7 April 2011
molar extinction coefficient (eCT) which were estimated from the spectrophotometric studies have a dra-
Keywords:
matic effect for the charge transfer complexes with differentiation of pi-acceptors. For further studies the
vibrational spectroscopy of the [(ArNH3þ)(PiA–)] (1), [(ArNHþ3 )(QðOHÞ2ꢀ)] (2) and [(ArNH3þ)(DNB–)] (3) of
(1:1) charge transfer complexes of (donor: acceptor) were characterized by elemental analysis, infrared
spectra, Raman spectra, 1H and 13CNMR spectra. The experimental data of elemental analyses of the
charge transfer complexes (1), (2) and (3) were in agreement with calculated data. The IR and Raman
spectra of (1), (2) and (3) are indicated to the presence of bands around 3100 and 1600 cm–1 distinguish
to ANHþ3 . The thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) techniques
were performed to give knowledge about thermal stability behavior of the synthesized charge transfer
complexes. The morphological features of start materials and charge transfer complexes were investi-
gated using scanning electron microscopy (SEM) and optical microscopy.
3-Amino-6-[2-(2-thienyl)vinyl]-1,2,4-
triazin-5(4H)-one (ArNH2)
Picric acid
Hydroquinone
3,5-Dinitrobenzene
Charge transfer complexes
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
partial transfer of a p-electron from the base to an unoccupied orbi-
tal of the acid [14]. Literature survey [15,16] concerning the impor-
tance of charge transfer complexes of many donating centers,
reveals a great attention as solar cells [15] and analysis of an active
ingredient or pharmaceutical dosages [16]. To continue our investi-
gation in this research area [17–19], we report here the formation of
the three new (1:1) CT-complexes [(ArNHþ3 )(PiA–)] (1),
[(ArNHþ3 )(QðOHÞ2ꢀ)] (2) and [(ArNHþ3 )(DNB–)] (3), respectively. The
main task of the work is to discuss the reaction stoichiometries,
spectroscopic characterizations of the new CT-complexes and pre-
dict the place of interaction between the ArNH2 donor and accep-
tors (PiA, Q(OH)2 and DNB).
Biological activities of the organic compounds containing thio-
phene are well known to exhibit various biological activities like
anti-HIV PR inhibitors [1], anti-breast cancer [2], anti-inflammatory
[3], anti-protozoal [4], antitumor [5], antitubercular with antimyco-
bacterial activity [6]. On the other hand, 1,2,4-triazine have
attracted the attention of most chemists because many of 1,2,4-tri-
azines are biologically active [7] and were used in medicine espe-
cially as anti AIDS, anticancer agents [8], antitubercular agents
[9], anti-anxiety and anti-inflammatory activities [10], as well as
in agriculture [11]. Intermolecular charge transfer (CT) complexes
are formed when electron donors and electron acceptors interacted
as general phenomenon in organic chemistry branch [12]. Mulliken
and Person [13] considered such complexes to arise from a Lewis
acid–Lewis base type of interactions. The bonding between the
components of the complex being postulated to arise from the
2. Experimental
2.1. Chemical and reagents
All chemicals and reagents used in this study were of analytical
grade. Picric acid, hydroquinone and 3,5-dinitrobenzene were ob-
tained from Aldrich Chemical Company.
⇑
Corresponding author at: Department of Chemistry, Faculty of Science, Port Said
University, Port Said, Egypt.
E-mail address: msrefat@yahoo.com (M.S. Refat).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.04.001

M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
117
2.2. Synthesis of ArNH2 donor
yield and high purity. First pathway, the conventional method by
refluxing 2-aminoganidine carbonate with 2-oxo-4-(2-thie-
nyl)but-3-enoic acid [20] in glacial acetic acid [21]. Second pathway,
carrying out the reaction between the two above compounds (sol-
vent free) under microwave irradiation as described in literature
The synthesis of the starting materials of 3-amino-6-[2-(2-thie-
nyl)vinyl]-1,2,4-triazin-5(4H)-one (donor; ArNH2) was carried out
in order to gain access to the best appropriate methods with good
NH2
NH
N
O
N
Hd
Hc
H
N
OH
S
MWI/2min
or AcOH ref. 2h
NH2
NH
S
+
H2N
Ha
O
O
He
Hb
donor
Scheme 1. Pathway preparation of 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one (donor; ArNH2).
Table 1
Analytical and Physical data for 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one (ArNH2) and their charge transfer complexes.
Compound empirical formula (M. Wt.)
Color
Km (X
ꢀ1 cmꢀ1 molꢀ1
)
Elemental analysis (%) found (calcd.)
C
H
N
S
ArNH2(C9H8N4OS) 220.25
[(ArNHþ3 )(PiA–)] (449.35)
[(ArNHþ3 )(QðOHÞꢀ2 )](330.36)
[(ArNHþ3 )(DNB–)] (388.36)
Yellow
Yellow
15
45
51
39
48.98
(49.08)
39.89
(40.09)
54.38
(54.53)
46.22
3.14
(3.66)
2.39
(2.47)
4.20
(4.27)
3.08
25.32
(25.44)
21.77
(21.82)
16.87
(16.96)
21.43
14.55
(14.56)
7.11
(7.14)
9.65
(9.71)
8.15
(8.26)
Light
Yellow
Light
Yellow
(46.39)
(3.11)
(21.64)
Fig. 1. Electronic absorption spectra of ArNH2–PiA, ArNH2–Q(OH)2 and ArNH2–DNB charge transfer systems, where [ArNH2] = 0.2 ꢁ 10–4 M, [Acceptors: PiA, Q(OH)2 and
DNB] = 0.2 ꢁ 10–4 M, Mixture, [(ArNH2)(acceptor)] = 0.2 ꢁ 10–4 M.

118
M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
Fig. 2. Titration spectra of (A) ArNH2–PiA, (B) ArNH2–Q(OH)2 and (C) ArNH2–DNB systems at detectable peaks of 345, 292 and 340 nm, respectively.
[22], (Scheme 1) the structure of donor was confirmed with its 1H
NMR, 13C NMR, IR, as well as mass spectra.
2.3. Synthesis of charge transfer complexes of ArNH2 donor
The three solid charge transfer complexes [(ArNHþ3 )(PiA–)] (1),
[(ArNHþ3 )(QðOHÞ2ꢀ)] (2) and [(ArNHþ3 )(DNB–)] (3) were synthesized
as a yellow-to-pale yellow colors by mixing a saturated solution
(25 mL) of 3-amino-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one
(donor; ArNH2) to a saturated solution (25 mL) of each acceptors
(PiA, Q(OH)2 and DNB) in methanol. All mixtures were stirred for
45 min at 40 °C temperature and the solid products were filtered
off, washed with minimum amounts of chloroform and dried under
vacuum over anhydrous CaCl2.
(i) First pathway: A mixture of 2-oxo-4-(2-thienyl)but-3-enoic
acid (0.01 mol), 2-aminoganidine carbonate (0.01 mol) in
glacial acetic acid (25 mL) was stirred under reflux for 2 h,
cooled to room temperature, the precipitate separated while
reflux collected by filtration on hot to give a yellowish crys-
tals (yield 62%) m.p. over 300 °C.
(ii) Second pathway: A mixture of 2-oxo-4-(2-thienyl)but-3-
enoic acid (0.01 mol) and 2-aminoganidine carbonate
(0.01 mol) were dissolved in a mixture of methylene chlo-
ride/methanol ((80/20) (v/v)), 15 mL) then 1.0 g of silica
gel (200–400 mesh) was added, the solvent was removed
by evaporation, the dried residue was transferred into a
glass beaker and irradiated for (1.5–2.0 min) in a domestic
microwave oven. The product was chromatographed on a
silica gel column, using methylene chloride as eluent.
(Yield = 98%) m.p. over 300 °C. IR (KBr): 3353, 3107 cmꢀ1
(NH2, NH), 1668 cmꢀ1 (C@O amide). 1H NMR (DMSO-d6):
d = 6.73 (d, 1H, J = 15.9 Hz, CH@CHe), 6.85 (s, 2H, NH2),
7.08 (t, 1H, J = 3.60, 4.80 Hz, thiophene – Hb,) 7.28 (d, 1H,
J = 3.3 Hz, thiophene – Hc), 7.51 (d, 1H, J = 5.1 Hz, thiophene
– Ha), 8.00 (d, 1H, J = 15.9 Hz, CHd@CH) and 12.27 (s, 1H,
NH). 13C NMR (DMSO-d6): d = 120.5, 120.6, 126.6, 127.5,
128.2, 128.4, 141.7, 142.4 and 155.3 (ArAC, C@C, C@N and
C@O), m/e (Int.%): 220 (14.27), 219 (64.24), 135 (100), 121
(20.20), 78 (13.51), 69 (12.99), 59 (15.14), 44 (15.69), 43
(32.57).
2.4. Physical measurements and analytical estimations
Elemental analyses (C, H, and N) were performed by the micro
analytical unit, Cairo University. The electronic absorption spectra
of the ArNH2 donor and the acceptors (PiA, Q(OH)2 and DNB) and
the resulted charge transfer complexes were recorded in methanol
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. Infrared spectra within the range of 4000–
400 cmꢀ1 for the free reactants and the resulted CT-complexes were
recorded from KBr disks using a Shimadzu FT-IR Spectrometer with
30 scans and 2 cmꢀ1 resolution, while Raman laser spectra of sam-
ples were measured on the Bruker FT–Raman with laser 50 mW. 1H,
13C NMR were recorded as DMSO solutions on a Bruker 600 MHz
spectrometer using TMS as the internal standard. DSC thermograms
of the ArNH2 donor and its charge transfer complexes were

M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
119
Fig. 3. The modified Benesi–Hildebrand plot of (A) ArNH2–PiA, (B) ArNH2–-Q(OH)2 and (C) ArNH2–DNB systems at detectable peaks of 345, 292 and 340 nm, respectively.
were reported in Table 1. The elemental analysis tool proved that
Table 2
the molar ratio between ArNH2 (donor) and respective
p-accep-
Spectorophotometric data of the ArNH2-PiA, ArNH2-Q(OH)2 and ArNH2-DNB charge
transfer systems in methanol.
tors (PiA, Q(OH)2 and DNB) is 1:1. The interaction process occurs
through the proton transfer from acidic centers in the mentioned
acceptors to the nitrogen atom of ArNH2 donor. Conductivity me-
ter type Jenway 4010 was used to measure conductivities of dif-
ferent charge transfer complexes of ArNH2 donor in DMSO with
1.0 ꢁ 10ꢀ3 mol/dm3 concentration. The conductivities of the free
reactants were also measured at a similar condition in order to
make comparison between the free donor and acceptors with
those of its charge transfer complexes. The molar conductances
of ArNH2 CT-complexes were reported in Table 1. The molar con-
Complex
K (l molꢀ1
)
k max (nm)
e )
(l molꢀ1 cmꢀ1
1.26 ꢁ 104
0.78 ꢁ 104
0.595 ꢁ 104
345
292
340
9.44 ꢁ 104
3.31 ꢁ 104
5.66 ꢁ 104
[(ArNHþ3 )(PiA–)]
[(ArNHþ3 )(QðOHÞꢀ2 )]
[(ArNHþ3 )(DNB–)]
obtained on a SCINCO DSC 1500 STA. Samples in solid form were
placed in aluminum pans with a pierced lid, and heated rate of
10 °C minꢀ1 under a nitrogen flow. TGA was carried out on a SCIN-
CO TGA 1500 STA apparatus at a heating rate of 10 °C minꢀ1 under
nitrogen atmosphere. Scanning electron microscopy (SEM) images
and energy-dispersive X-ray detection (EDX) were taken in Joel
JSM-6390 equipment, with an accelerating voltage of 20 kV. Micro-
structures of donor and charge transfer complexes were examined
by Optical microscopy model Meiji 7800 Techno Microscopy.
ductance values range from 15 to 51
X
ꢀ1 cmꢀ1 molꢀ1. The molar
conductance values indicate that the charge transfer complexes
have slightly electrolytic nature. Slightly electrolytic complexes
assigned to the formation of positive and negative datives anions
under the acid–base migration theory [23].
3.2. UV/Vis spectra and photometric titrations
The electronic absorption spectra of 0.2 ꢁ 10ꢀ4 M solutions of
ArNH2, PiA, Q(OH)2, DNB, and their ArNH2-acceptor mixtures in
methanol are shown in Fig. 1. The charge transfer absorption bands
which detectable after proton transfer were observed in the spec-
tra of the reaction mixtures at 350 nm, (292 and 338 nm) and
(277and 340 nm) for the ArNH2–PiA, ArNH2–Q(OH)2 and ArNH2–
DNB complexes, respectively. Based on the photometric titration
processes represented in Fig. 2, the stoichiometry has 1:1 M ratio
3. Results and discussion
3.1. Analytical data and conductivity measurements
Elemental analyses data of 3-amino-6-[2-(2-thienyl)vinyl]-1,2,
4-triazin-5(4H)-one (donor) and their charge transfer complexes

120
M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
Fig. 5. Raman Laser spectra of (A) [(ArNHþ3 )(DNB–)] and (B) [(ArNH3þ)(PiA–)] charge
transfer complexes.
Table 3
Assignments of the IR and Raman (R) spectral bands (cmꢀ1) for ArNH2 and their
charge transfer complexes.
d(NHþ3
)
d(NHþ3
)
q
(NHþ3
IR
)
Compound
m
(NH)
def
sym
IR
R
IR
R
IR
R
R
[(ArNHþ3 )(PiA–)]
[(ArNHþ3 )(QðOHÞꢀ2 )]
[(ArNHþ3 )(DNB–)]
Fig. 4. IR spectra of (A): [(ArNH3þ)(PiA–)], (B): [(ArNH3þ)(QðOHÞ2ꢀ)] and (C):
3100 3085 1627 1616 1334 1337 797 827
3065 3102 1546 1604 1350 1327 804 779
3107 3100 1614 1624 1350 1353 812 845
[(ArNHþ3 )(DNB–)] charge transfer complexes.
for ArNH2: acceptor. The 1:1 modified Benesi–Hildebrand Eq. (1)
[24] was used in the calculations of formation constant, K, and
the molar absorptivity, e, values for each charge transfer complexes
400 cmꢀl shows the main characteristic absorption bands of NH3þ
group. For example the (NH), ddef(NH3), dsym(NH3), and (NH3)
m
q
formed. Fig. 3 showed these straight lines plots and the obtained
data were given in Table 2. The data reveals that ArNH2–PiA,
ArNH2–Q(OH)2 and ArNH2–DNB charge transfer systems show
high values of both the K and . The high values of K reflect the high
stability of the formed CT-complexes as a result of the expected
high electron donation from the ArNH2 while the high value of
agree quite well with the formation of CT-complexes which are
known to have high absorptivity values [17–19]. The value of K
for [(ArNHþ3 )(PiA–)] is about twice times higher than that of
[(ArNHþ3 )(QðOHÞ2ꢀ)] or [(ArNHþ3 )(DNB–)]. Accordingly, the formed
CT-complexes are formulated as [(ArNH2)(acceptor)]. These results
were supported by the elemental analysis data of the solid com-
plexes as well as photometric titration.
vibration of all charge transfer complexes occurs at about 3100,
1600, 1300 and 800 cmꢀ1, respectively. The presence of these
bands confirmed that the proton transfer phenomena from the
acidic center of each acceptor to the lone pair of electron of –
NH2 group to form NHþ ammonium ion upon complexation. Also,
3
there is some small changes comparison between the spectra of
the CT-complexes and those of the reactants, could also be notable
from the expected changes in the symmetry and electronic config-
urations of both reactants upon charge transfer complexation.
3.3.1. 1H and 13C NMR spectra
The reaction of ArNH2 as donor with picric acid as acceptor gave
a new charge transfer complex named by 5-oxo-6-[2-(2-thienyl)
vinyl] -4,5-dihydro-1,2,4-triazin-3-aminium-2,4,6-trinitrobenzen-
olate (Scheme 2). The 1H NMR showed disappearance of the signal
of NH2 in ArNH2 donor with presence of a broad signal at
d = 4.8 ppm which assigned to NHþ3 through the formation of salt
between ArNH2 and picric acid. The signal at d = 8.88 ppm in the
free picric acid which assigned to aromatic proton was right
shifted. This displacement due to the increase of the shielding of
these protons with overall decrease in the value of the coupling
constant because of the change of the magnetic environment of
CoaCodl
A
1
Coa þ Cod
¼
þ
ð1Þ
K
e
e
3.3. Infrared and Raman spectra
The infrared and Raman data for the ArNH2 charge transfer
complexes are shown in Figs. 4 and 5 and the observed absorption
bands were listed in Table 3. The band assignments between 4000–

M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
121
H
N+
Hd
He
N
N
N
Ha
O-
H
S
H
H
O
N
Ha
Hb
N
S
N+
NO2
NO2
H
OH
H
NH
Hb
Hd HO
He
Hc
Hf
O2N
O
Hc
Scheme 4. Formula of [(ArNH3þ)(QðOHÞꢀ2 )] charge transfer complex.
Hf
Scheme 2. Formula of [(ArNH3þ)(PiA–)] charge transfer complex.
and 14,6 (s, 1H, OH). 13C NMR (DMSO-d6): d = 115.5, 123.5,
126.2, 126.8, 127.8, 128.1, 128.4, 142.1, 145.8, 149.6, 154.9 and
164.7 (ArAC, C@C, C@N and C@O).
all proton as a result of complex formation. 1H NMR (DMSO-d6):
d = 4.8 (b, 3H, NHþ), 6.40 (d, 1H, J = 14.2 Hz, CH@CHe), 7.12 (t,
3
1H, J = 3.6, 3.6 Hz, thiophene – Hb), 7.31 (d, 1H, J = 3.6 Hz, thio-
phene – Hc), 7.59 (d, 1H, J = 5.4 Hz, thiophene – Ha), 7.75 (d, 1H,
J = 14.7 Hz, CHd@CH), 8.60 (s, 2H, Hf of benzene ring) and 12,01
(s, 1H, NH). 13C NMR (DMSO-d6): d = 120.5, 124.3, 125.2, 127.4,
128.3, 128.4, 129.1, 138.8, 141.2, 141.7, 155.1, 160.6 and 163.1
(ArAC, C@C, C@N and C@O).
3.4. Optical and scanning electron microscopes
Surface image using optical microscope (Fig. 6) demonstrate to
the porous structures of the surface of prepared charge transfer
complexes. Analysis of these images shows the size of pores to
be quite different with different acceptors. The chemical analysis
results by EDX for the formed charge transfer complexes show a
homogenous distribution of each acceptor. SEM examinations
were checked the surfaces of these CT-complexes that show a
small particles which tendency to agglomerates formation with
different shapes comparison with the start materials. The chemical
compositions of the free ArNH2 donor and charge transfer com-
plexes were determined using energy-dispersive X-ray diffraction
(EDX). In the EDX profile of these complexes (Fig. 7A–D), the peaks
of the carbon, nitrogen, oxygen, and sulfur elements, wþhich consti-
tute the molecules of ArNH2, [(ArNHþ3 )(PiA–)], [(ArNH3 )(QðOHÞ2ꢀ)]
and [(ArNHþ3 )(DNB–)] charge transfer complexes, are clearly identi-
fied confirming the proposed structures.
Similar results was obtained by the reaction of ArNH2 with dini-
trobenzene which, resulted in 5-hydroxy-6-(2-(thiophen-2-yl)vi-
nyl)-1,2,4-triazin-3-aminium 2,6-dinitro benzen-1-ide (Scheme
3), the 1H NMR showed disappearance of the signal of NH2 in
ArNH2 donor with appearance of broad signal at d = 4.5 ppm for
NHþ3 referring to the formation of salt between the electron poor
dinitrobenzene and the electron rich triazine derivative ArNH2.
The complex formed an activate NHAC@O M N@CAOH tautomer-
ization in triazine ring which, illustrated in the appearance of sig-
nal at d = 14.72 ppm for OH group and disappearþance of ring NH
signal. 1H NMR (DMSO-d6): d = 4.5 (b, 3H, NH3 ), 6.80 (d, 1H,
J = 10.2 Hz, CH@CHe), 7.13 (t, 1H, J = 3.6,3.6 Hz, thiophene – Hb),
7.20 (d, 1H, J = 1.8 Hz, dinitrobenzene– Hf), 7.51 (d, 1H, J = 5.4 Hz,
thiophene – Hc), 7.81 (d, 1H, J = 6.6 Hz, thiophene – Ha), 7.91 (t,
1H, J = 5.4, 5.6 Hz, dinitrobenzene – Hg), 8.65 (d, 1H, J = 10.2 Hz,
CHd@CH) and 14.72 (s, 1H, OH). 13C NMR (DMSO-d6): d = 118.5,
123.5, 126.3, 126.9, 127.9, 128.2, 129.3, 129.4, 131.5, 142.2,
147.9, 154.9 and 164.6 (ArAC, C@C, C@N and C@O).
For the reaction between the electron rich 1,4-qinol acceptor
and triazine derivative ArNH2 donor, the (5-hydroxy-6-[2-(thio-
phen-2-yl)ethenyl]-1,2,4-triazin-3-aminium 4-hydroxy phenolate)
(Scheme 4) is resulted with the same result that obtained from the
electron poor picric acid and dinitrobenzene. The 1H NMR showed
signals at d = 4.51, 6.56 and 8.66 ppm for NHþ3 , four aromatic quinol
protons and one quinol OH proton, respectively, with disappear-
ance of NH2 signal of ArNH2 donor. 1H NMR (DMSO-d6): d = 4.65
(b, 3H, NHþ3 ), 6.56 (s, 4H, ArH quinol), 6.81 (d, 1H, J = 16.2 Hz,
CH@CHe), 7.08 (t, 1H, J = 3.60, 4.80 Hz, thiophene – Hb,) 7.20 (d,
1H, J = 1.5 Hz, thiophene – Hc), 7.52 (d, 1H, J = 2.4 Hz, thiophene
– Ha), 7.82 (d, 1H, J = 15.9 Hz, CHd@CH), 8.66 (s, 1H, OH quinol)
3.5. Thermal analysis TGA/DSC
The simultaneous TGA/DSC analysis of the ArNH2(C9H7N4OS]
free
þdonor
and
their
respective
[(ArNHþ3 )(PiA–)],
[(ArNH3 )(QðOHÞꢀ2 )] and [(ArNHþ3 )(DNB–)] charge transfer com-
plexes were studied from ambient temperature to 800 °C under
nitrogen atmosphere using
a-Al2O3 as the reference (Fig. 8. The
free donor decomposed in three steps with seven (100, 225, 275,
400, 475, 530 and 750 °C) DSC peaks. The first decomposition step
at DSC = 100 and 225 °C endothermic, it loses a fragment of NH2
with a weight loss 7.73%. Then the endothermic peaks at 275 and
400 °C were assigned to the loss of H2S and C2H2 after the decom-
H
f
H
g
O2N
H
H
H
a
H
d
S
N
N
N
C-
H
H
f
N+
b
NO2
H
H
H
e
c
HO
Fig. 6. Optical microscopy photos of (A) ArNH2, (B) [(ArNHþ3 )(PiAꢀ)], (C)
[(ArNHþ3 )(QðOHÞ2ꢀ)] and (D) [(ArNHþ3 )(DNBꢀ)] complexes.
Scheme 3. Formula of [(ArNH3þ)(DNB–)] charge transfer complex.

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M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
A
001
500
450
400
350
300
250
200
150
100
50
0
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00
keV
003
B
1000
900
800
700
600
500
400
300
200
100
0
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
C
004
1000
900
800
700
600
500
400
300
200
100
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. 7. SEM images and EDX spectra of (A) ArNH2, (B) [(ArNHþ3 )(PiAꢀ)], (C) [(ArNHþ3 )(QðOHÞ2ꢀ)] and (D) [(ArNH3þ)(DNBꢀ)] complexes.
position of thiophene moiety with weight loss 27.27%. The third
step has a wide range 400–800 °C with three DSC maximum peaks
at 475, 530 and 750 °C involves the removal of C5HN3O with mass
loss 54.09%.
800 °C with DSC maximum peaks at (150 °C, 200 °C endothermic),
275 °C exothermic and 625 °C exothermic, respectively. The first
decomposition step has a weight loss about 10.22% with librated
one of NO2 molecules from picric acid moiety. The second step is
exothermically by fragments of 2NO2 + NH2 + OH moieties with
27.78% weight loss. The last step completed with the loss of rest or-
The [(ArNHþ3 )(PiA–)] charge transfer complex was degraded by
three decomposition steps from 25–250 °C, 250–400 °C and 400–

M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
123
002
D
1800
1600
1400
1200
1000
800
600
400
200
0
0.00
0.80
1.60
2.40
3.20
keV
4.00
4.80
5.60
6.40
Fig. 7 (continued)
Fig. 8. A–D: TGA and DSC curves of (A) ArNH2, (B) [(ArNHþ3 )(PiAꢀ)], (C) [(ArNHþ3 )(QðOHÞ2ꢀ)] and (D) [(ArNH3þ)(DNBꢀ)] complexes.
ganic moieties of both ArNH2 donor and PiA acceptor, leaving a few
residual carbon atoms.
endothermically DSC peaks at 100, 150, 200 and 275 °C and one
exothermic peak at 350 °C with a weight loss 71.21% which as-
signed to starts decomposed in the temperature range of 25–
400 °C with the liberated of thiophene, acetylene and DNB frag-
ments. The amino triazin moiety was decomposed in both endo-
thermically and exothermically peaks at 450 and 700 °C,
respectively, with a weight loss value equal 23.00%. Few carbon
atoms remain as a final residual.
The [(ArNHþ3 )(QðOHÞꢀ2 )] charge transfer complex decomposes
firstly in the range of 25–300 °C, endothermically evolved thio-
phene moiety with a weight loss 25.07%. The second step within
range (300–400 °C, mass loss 13.00%) involves the exothermic peak
with loss of acetylene and hydroxo moieties. The third decomposi-
tion step at DSC = 435 °C assigned to the losses of NH2 and the sec-
ond OH group of hydroquinone acceptor with a weight 10.00%. The
last degradation step at DSC = (675 and 725 °C exothermically) has
an extremely large scale of weight loss for about 42.00% due to
libration of the rest of both donor and hydroquinone acceptor leav-
ing few carbonþatoms as residue.
References
[1] C. Bonini, L. Chiummiento, M.D. Bonis, M. Funicello, P. Lupattelli, G. Suanno, F.
Berti, P. Campaner, Tetrahedron 61 (2005) 6580.
[2] L. Brault, E. Migianu, J. Med. Chem. 40 (2005) 757.
[3] P.R. Kumar, S. Raju, P.S. Goud, M. Sailaja, M.R. Sarma, G.O. Reddy, M.P. Kumar,
V.V.R.M.K. Reddy, T. Suresh, P. Hegde, Bioorg. Med. Chem. 12 (5) (2004) 1221.
The [(ArNH3 )(DNB–)] charge transfer complex decomposed in
two major steps. The first degradation step contain four maximum

124
M.S. Refat et al. / Journal of Molecular Structure 995 (2011) 116–124
[4] R.A. Tapia, L. Alegria, C.D. Pessoa, C. Salas, M.J. Cortes, J.A. Valderrama, M.E.
[14] J.E. Frey, A.M. Andrews, D.G. Ankoviac, D.N. Beaman, L.E. Du Pont, T.E. Elsner,
S.R. Lang, M.A.O. Zwart, R.E. Seagle, L.A. Torreano, J. Org. Chem. 55 (2) (1990)
606.
Sarciron, F. Pautet, N. Walchshofer, H. Fillion, Bioorg. Med. Chem. 11 (2003)
2175.
[5] P. Dallemagne, L.P. Khanh, A. Alsaidi, I. Varlet, V. Collot, M. Paillet, R. Bureau, S.
Rault, Bioorg. Med. Chem. 11 (7) (2003) 1161.
[6] M.P. Kumar, G. Panda, Y.K. Manju, V. Chaturvedi, S. Sinha, Bioorg. Med. Chem.
Lett. 18 (2008) 289.
[15] K.Y. Rajpure, C.H. Bhosale, Mater. Chem. phys. 64 (1) (2000) 70.
[16] S. Licht, Solar Energy Mater. Solar Cells 38 (1995) 305.
[17] M.S. Refat, H.M.A. Killa, I. Grabchev, M.Y. El-Sayed, Spectroscopy 52 (2) (2007)
75.
[7] R.M. Abdel-Rahman, Phosphorous, Sulphur Silicon-Rev 166 (2000) 315.
[8] R.M. Abdel-Rahman, Pharmazie 56 (1) (2001) 18.
[9] C. Gill, G. Jadhav, M. Shaikh, R. Kale, A. Ghawalkar, D. Nagargoje, M. Shiradkar,
Bioorg. Med. Chem. Lett. 18 (2008) 6244.
[18] M.S. Refat, L.A. El-Zayat, Polyhedron 27 (2) (2008) 475.
[19] M.S. Refat, H.A. Ahmed, I. Grabchev, L.A. El-Zayat, Acta A 70 (4) (2008) 907.
[20] V. Varshney, N.N. Mishra, P.K. Shukla, D.P. Sahu, Bioorg. Med. Chem. Lett. 19
(23) (2009) 6810.
[10] P. Mullick, S.A. Khan, T. Begum, S. Verma, D. Kaushik, O. Alam, Acta Poloniae
Pharm. Drug Res. 66 (2009) 379.
[11] R.M. Abdel-Rahman, Pharmazie 56 (2001) 195.
[12] N. Haga, H. Nakajima, H. Takayanagi, K. Tokumaru, J. Org. Chem. 63 (1998)
5372.
[21] A. Dornow, H. Menzel, P. Marx, Chem. Ber. 97 (1964) 2173.
[22] H.A. El-Sayed, A.H. Moustafa, A.Z. Haikal, E.S.H. El-Ashry, Nucl., Nucl. Nucleic
Acids 28 (2009) 184.
[23] M. Gaber, H.A. Dessouki, E.H. Hossani, Spectrosc. Lett. 25 (4) (1992) 463.
[24] R. Abu-Eittah, A. El-Kourashy, J. Phys. Chem. 76 (1972) 2405.
[13] R.S. Mulliken, W.B. Person, Molecular Complexes: A Lecture and Reprint, John
Wiley and Sons, New York, 1969.