IR spectroscopic analysis of the new organic silver complex C 13H13N4OAg

Article abstract of DOI:10.1016/j.saa.2013.03.046

IR analysis in the frequency range 400-4000 cm^-1 is used here to investigate the changes in different modes of thermally treated new metal complex (diphenyl carbazide silver complex DPCAg, C₁₃H ₁₃N₄OAg) during the glass transition at 91 C and the high temperature phase transition at 167 C. These two phase transitions in this new metal compound are studied here by detecting the changes in some IR spectroscopic parameters (e.g., mode shift, band contour, peak height and peak intensity) during the elevation of temperature. All of the vibrations of DPCAg were found to be due to ionic fundamentals 3311 cm^-1, 3097 cm ^-1, 3052 cm^-1, 1677 cm^-1, 1602 cm^-1, 1492 cm^-1, 1306 cm^-1, 1252 cm^-1, 887 cm ^-1 and 755 cm^-1. The results obtained can be considered as the first spectroscopic analysis of this new metal complex. These results strongly confirmed that the thermally treated DPCAg transverse a glass transition at 91 C and a high temperature phase transition at 167 C. Anomalous spectroscopic changes near the glass transition temperature T_g could be recorded. A temperature dependence of peak intensity of the two modes 810 cm^-1 and 3440 cm^-1 could be observed beyond T_g. Also, the high temperature phase modification at 167 C showed anomalous change in the spectroscopic parameters before and after the phase transition process. A proposed silver position in the new silver complex DPCAg has been presented.

Full text of DOI:10.1016/j.saa.2013.03.046

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 111 (2013) 252–259
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
IR spectroscopic analysis of the new organic silver complex C13H13N4OAg
F. El-Kabbany a, S. Taha b, M. Hafez a,
⇑
a Physics Dept., Faculty of Science, Cairo University, Egypt
b Physics Dept., Faculty of Science, Fayoum University, Egypt
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
IR analysis is used to investigate the
changes in modes of DPCAg.
The glass and the high temperature
phase transitions are studied by IR
spectroscopic parameters.
ꢀ
A proposed silver position in the new
complex DPCAg has been presented.
a r t i c l e i n f o
a b s t r a c t
IR analysis in the frequency range 400–4000 cmꢁ1 is used here to investigate the changes in different
modes of thermally treated new metal complex (diphenyl carbazide silver complex DPCAg, C13H13N4OAg)
during the glass transition at 91 °C and the high temperature phase transition at 167 °C. These two phase
transitions in this new metal compound are studied here by detecting the changes in some IR spectro-
scopic parameters (e.g., mode shift, band contour, peak height and peak intensity) during the elevation
Article history:
Received 9 October 2012
Received in revised form 7 March 2013
Accepted 12 March 2013
Available online 29 March 2013
of temperature. All of the vibrations of DPCAg were found to be due to ionic fundamentals 3311 cmꢁ1
3097 cmꢁ1 3052 cmꢁ1 1677 cmꢁ1 1602 cmꢁ1 1492 cmꢁ1 1306 cmꢁ1 1252 cmꢁ1 887 cmꢁ1 and
,
Keywords:
Silver complex
IR analysis
,
,
,
,
,
,
,
755 cmꢁ1. The results obtained can be considered as the first spectroscopic analysis of this new metal
complex. These results strongly confirmed that the thermally treated DPCAg transverse a glass transition
at 91 °C and a high temperature phase transition at 167 °C. Anomalous spectroscopic changes near the
glass transition temperature Tg could be recorded. A temperature dependence of peak intensity of the
two modes 810 cmꢁ1 and 3440 cmꢁ1 could be observed beyond Tg. Also, the high temperature phase
modification at 167 °C showed anomalous change in the spectroscopic parameters before and after the
phase transition process. A proposed silver position in the new silver complex DPCAg has been presented.
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
properties, which are used in the identification or determination of
either the metal ion or the coordinating agents, illustrate applica-
The importance of metal-complex formation stems from the
fact that when a metal ion becomes part of a complex, it acquires
new properties which may be strikingly different from those of the
original ion. These changes may include new crystalline form of the
formed compound and the different physical properties. These new
tions of such complexing process. The present work aims to study
the optimum condition for the formation of one silver complex,
and identify the new physical properties, which is probably found.
A new work on silver complex formed by amorphous DPC and sil-
ver will be presented in this part. DPCAg complex sample is pre-
pared by the chemical reaction between amorphous DPC [1–4]
and silver nitrate. A special attention has been paid to the probable
stability of the obtained silver complex.
⇑
Corresponding author. Tel.: +202 35676753.
E-mail address: marwa_hafez@yahoo.com (M. Hafez).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.03.046

F. El-Kabbany et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 111 (2013) 252–259
253
Fig. 1. (a) TGA thermogram for DPCAg complex. (b) DSC thermogram and its first derivative for AgDPC complex. (c) DSC thermogram for AgDPC organic complex.

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F. El-Kabbany et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 111 (2013) 252–259
An important feature of many organic metal complexes is their
erties of this metal complex compound. We hope that infrared
analysis might be successfully used to confirm the previously ob-
served phase transitions through the spectral changes in DPCAg.
extended linear chain structure. Transition metal organic com-
plexes have attracted the interest of experimental and theoretical
chemists and physicists for many years due to their fascinating
chemical and photophysical properties [5,6]. Recent examples in-
clude the development of a vapochromic light emitting diode from
a linear chain complex [7]. It has been reported that colorless tri-
nuclear gold compounds that do not form extended chain structure
by themselves can produce brightly colored complexes by sand-
wiching naked Ag+ ions to form linear chain complexes with fasci-
nating luminescence properties that include the luminescence
thermochromism [8]. Recent results have demonstrated that the
electron rich complexes can interact with organic Lewis acids to
produce infinite linear chain complexes. This means that the intro-
duction of electron rich metal element, e.g., Ag, into organic com-
plex may create new important properties and new structures.
The present study aims to use IR spectroscopic analysis to check
the probable stability of this new silver complex compound.
The present work is considered as an extension of our work on
DPCAg (includes thermal analysis such as DSC and electrical mea-
surements) [9]. These thermal and electrical investigations give a
detection for the first time of the existence of a probable glass tran-
sition at 91 °C and high temperature phase transition at 167 °C in
DPCAg compound. Here DPCAg is subjected to an IR spectroscopic
study under conditions similar to that performed before in thermal
and electrical analysis. The nature of the temperature dependence
of thermal activity of the vibrating groups is of great interest as its
role that is fundamental in explaining many of the physical prop-
Experimental
DPCAg complex compound sample is prepared by the chemical
reaction between amorphous DPC and silver nitrate (dissolved in
acetone).
C13H14N4O þ AgNO3 ! C13H13N4OAg þ HNO3
A precipitated powder is obtained in a solution of nitric acid. After
filtrating the precipitated powder and drying it, the physical prop-
erties of this new organic complex C13H13N4OAg can be studied.
We report for the first time here the properties and the crystal
structure of the new silver complex.
The thermogravimetric analysis (TGA) was carried out in this
study by Shimadzu system type 50 made in Japan. Differential
scanning calorimetry (DSC) is an efficient and powerful tool for
studying phase transition phenomena. Shimadzu DSC-60 is an
accurate differential scanning calorimetry system with numerous
features such as high sensitivity noise level as low as 1 lwRMS (at
15 °C). The temperature range here is extended between – 140 °C
and 1600 °C when liquefied nitrogen supplied.
X-ray diffraction patterns are carried out here by X-ray machine
type, Bruker axs D8, Germany with Cu Ka (k = 1.5406 Å) radiation
and secondary monochromator in the 2h range from 20° to 70°. A
good computer analysis program must be used for X-ray data
Fig. 2. X-ray diffraction patterns for DPCAg complex.

F. El-Kabbany et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 111 (2013) 252–259
255
analysis. The program used in the present study is crysfire 2002
interactive powder indexing supports system. Crysfire program as-
sists users to find the possible solutions to the powder indexing
problems, in the form of complete or partial unit cells.
IR spectra were recorded using the FT-IR type Perkin–Elmer re-
corded on satellite 2000 spectrometer and the experimental tech-
nique employed has been reported [10]. The samples used were in
the form of discs prepared by mixing 20 mg of DPCAg complex
with one gram of KBr in a cylindrical die of 10 mm diameter. The
die was then evacuated to ensure dryness and the sample was
pressed. The spectra were recorded in the 400–4000 cmꢁ1 region
by a computerized system attached to a monitor and a printer.
heat absorbed is reduced by 0.04 mW. This little change in heat ab-
sorbed indicates that this transition is not due to crystal structure
change. It can be assigned to a glass transition in this organic silver
complex. Non-crystalline solids are known as amorphous materi-
als. Such materials do not have their atoms or molecules arranged
on a lattice that repeats periodically in space. The kink point at
91 °C is called a glass transition temperature Tg. In fact, Tg is the
critical temperature that separates their glassy and rubbery behav-
ior. If a material is at a temperature below its Tg, large-scale molec-
ular motion is not possible because the material is essentially
frozen. If it is at a temperature above its Tg, molecular motion on
the scale of repeat unit takes place, allowing it to be soft or rub-
bery. The glass transition is the reversible transition in amorphous
materials (or in amorphous regions within semicrystalline materi-
als) from a hard and relatively brittle state into a molten or rubber-
like state. An amorphous solid that exhibits a glass transition is
called a glass. Despite the massive change in the physical proper-
ties of a material through its glass transition, the transition is not
itself a phase transition of any kind; rather it is a laboratory phe-
nomenon extending over a range of temperature and defined by
one of several conventions [12–14]. Glass material at room tem-
perature has an amorphous structure. Such state is called a glass
state. AgDPC complex has amorphous structure at room tempera-
ture (glassy state). When AgDPC heated to 91 °C, it transform to an-
other state (with orthorhombic crystal structure). Here AgDPC
transforms from amorphous state to the orthorhombic state. Such
phase transformation in AgDPC is called glass transition.
Results and discussion
At first and as a fast check up of the dried precipitated material,
a thermogravimetric analysis TGA is carried out as shown in
Fig. 1a. According to this figure, the DPCAg sample is stable up to
ꢂ1018 °C. At this temperature, the sample starts a melting process
and very little weight loss 12.4%. The amorphous DPC material has
a melting point 162 °C. This means that this new silver complex
belongs to very high melting point. Thermal stability of this com-
plex is very high and that is mainly depended on which of the
bonds of the complex breaks first at elevated temperatures [11].
Fig. 1b shows a DSC thermograms and its derivative with time
(DrDSC) for AgDPC complex sample in a temperature range be-
tween room temperature (ꢂ30 °C) and 140 °C. This DSC curve
showed clearly a distinct kink at ꢂ91 °C. Such kink in the DSC ther-
mogram indicates a new type of transition, which takes place in
this organic complex that contains silver. At this kink, the rate of
Fig. 1c shows the DSC thermogram for AgDPC sample in a tem-
perature range between 160 °C and 185 °C. A clear endothermic
phase transition can be observed at 167 °C.
Fig. 3. X-ray diffraction pattern for DPCAg organic complex samples at three different temperatures 150 °C, 180 °C and 200 °C.

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Table 1
Principle modes of parent amorphous DPC and silver complex (DPCAg) at room
temperature.
Modes
Amorphous DPC Organic complex
at R.T.
(DPCAg) at R.T.
Asymmetric stretching of NAH
Symmetric stretching of NAH
Aromatic CAH stretching
Bending or deformation mode of NAH 1677
NAN stretching symmetric vibrations 1602
NAN stretching asymmetric vibrations 1492
CAH stretching vibrations
C@O stretching vibrations
Out of plane CAH bending
Monosubstituted benzene
NAH oscillation
3311
3097
3052
3440
3186
3124
1628
1512
1442
1342
1273
933
1306
1252
887
755
489
810
517
Fig. 5. Peak height temperature dependence of the IR modes 517 cmꢁ1, 1273 cmꢁ1
and 1342 cmꢁ1 during the glass transition in DPCAg.
120 °C. However, the change in the principle IR different modes
is due to the elevation of temperature which is given in Table 2.
It was found that there is a clear change in the peak height of
the principle modes 517 cmꢁ1, 1273 cmꢁ1, 1342 cmꢁ1, 1628 cmꢁ1
and 3124 cmꢁ1 as the DPCAg sample temperature traversing the
glass transition temperature Tg ꢂ 91 °C as shown in Figs. 5 and 6.
The peak height shows anomalous change near the glass transition
point. The peak intensity of the two modes 810 cmꢁ1 and
3440 cmꢁ1 showed clear temperature dependence and fast reduc-
tion beyond Tg as shown in Fig. 7. By comparing the infrared spec-
tra of the complex and ligand, one can see clear frequency shift of
some peaks, due to silver metal. The scheme of the proposed reac-
tion between DPC and silver metal cation is shown in Fig. 8. During
the complex formation, the ligands coordinate to the central metal
atom, and the newly established metal–ligand coordinate bond
changes the electronic structure and the energy state. These
changes affect the vibration of the ligand and consequently its
vibrational spectrum [15].
Fig. 4. Infrared spectra of DPCAg complex at room temperature (R.T. ꢂ 30 °C), 80 °C
and 120 °C.
X-ray analysis confirmed the presence of a probable glass tran-
sition at T = 91 °C and another high temperature phase transition at
167 °C as shown in Figs. 2 and 3.
The IR spectroscopic analysis is used here to study this probable
glass transition in DPCAg at 91 °C and the high temperature phase
transition at 167 °C. At first, the principle modes of the parent
amorphous (DPC) and the silver complex DPCAg are checked at
room temperature as given in Table 1. In order to do that, a set
of IR spectra are fulfilled at different temperatures covering the re-
gions before and after this glass transition. The selected tempera-
tures are R.T., 60 °C, 70 °C, 80 °C, 100 °C, 110 °C and 120 °C. Fig. 4
shows examples of the recorded IR spectra at R.T., 80 °C and
The infrared spectroscopy is successfully used here to study the
high temperature phase transition of DPCAg at 167 °C. Fig. 9 shows
the infrared spectra of DPCAg complex at room temperature,
150 °C and 200 °C. The detailed wave number values of the princi-
ple mode are given in Table 3. Also, in the same table, the principle
modes of the parent amorphous DPC are given. A fast review of the
mode values showed that there is a clear positive and negative
mode change between the parent material and the new complex
DPCAg.

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257
Table 2
Variation of the principle modes of the silver complex (DPCAg) with temperature.
Modes
R.T.
60 °C
70 °C
80 °C
100 °C
110 °C
120 °C
Asymmetric stretching of NAH
Symmetric stretching of NAH
Aromatic CAH stretching
Bending or deformation mode of NAH
NAN stretching symmetric vibrations
NAN stretching asymmetric vibrations
CAH stretching vibrations
C@O stretching vibrations
Out of plane CAH bending
Monosubstituted benzene
3440
3186
3124
1628
1512
1442
1342
1273
933
3440
–
3425
–
3119
1620
–
1450
1373
1311
–
864
551
3425
–
3094
1635
1512
–
1388
1311
–
848
555
3471
3203
3093
1620
1527
1450
1373
1311
881
3440
3186
–
1620
–
3471
3193
3116
1620
1512
–
1388
1296
972
3132
1635
1500
1404
–
1234
926
848
540
–
1388
–
941
863
585
810
517
818
509
879
551
NAH oscillation
Fig. 6. Peak height temperature dependence of the IR modes 1628 cmꢁ1 and
3124 cmꢁ1 during the glass transition in DPCAg.
Fig. 7. Intensity temperature dependence of the two principle modes 810 cmꢁ1 and
3440 cmꢁ1 during the glass transition in DPCAg.
In addition, Fig. 9 shows two high temperature spectra for
DPCAg complex at 150 °C and 200 °C. As clear, the two spectra
are completely different. However, the IR spectra are recorded in
details for DPCAg samples at ten different temperatures started
at R.T., 120 °C, 130 °C, 140 °C, 150 °C, 170 °C, 180 °C, 190 °C,
200 °C and 210 °C. The mode changes at these temperatures are
tabulated in Table 3. The change in peak height with temperature
for the different modes of the IR spectra is given in Figs. 10 and 11.
All of them showed anomalous change in the phase transition re-
gion. The variation of the peak intensity of both the monosubsti-
tuted benzene (810 cmꢁ1) and asymmetric stretching of NAH
(3440 cmꢁ1) with temperature is given in Fig. 12. All of these
changes in the spectroscopic parameters support the previously
detected high temperature phase transition in DPCAg at 167 °C.
A phase transition process is considered as an indication of the
regularity of the thermodynamic functions characterizing the state
of a substance at a special point called the phase transition point.
As soon as such a point is reached the initial phase can no longer
exist and changes into a new phase. Near this critical point a sub-
stance acquires unusual properties. Accordingly, the phase trans-
formations observed here in DPCAg may be experimentally
observed by studying the temperature dependence of the vibra-
tional spectra, especially near the glass transition point 91 °C and
high temperature phase transition point at 167 °C. The elevation
of temperature increases the probability of reorientation of DPCAg
molecules and in turn, this should lead to a change of the charac-
teristics of the vibrational spectrum. This provides very important
information about the dynamics of the process of phase transition
in this metal complex. It is well known that a distinct shape of an
absorption band for distinct molecule is related to the number of
ions that undergo the various energy transitions. Thus, the most in-
tense line is that represents the largest number of ions undergoing
a particular transition. The intensity of each line depends here on
the number of DPC ions undergoing a certain energy transition
and hence the band envelope as a whole is a representation of
the total number of DPC ions involved [16]. As the temperature
of DPC ions increased, the contour of the absorption band will
change, but the area under the envelope will remain constant, pro-

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F. El-Kabbany et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 111 (2013) 252–259
Table 3
Variation of the principle modes of the silver complex (DPCAg) during its high
temperature phase transition.
Modes
130 °C 140 °C 150 °C 170 °C 180 °C 190 °C 200 °C 210 °C
3494 3484 3471 3417 3448 3456 3456 3456
Asymmetric
stretching of
NAH
Symmetric
–
3209 3186 3155 3186 3178 3163 3197
stretching of
NAH
Aromatic CAH
stretching
3098 3101 3123 3086 3124 3078 3106 3109
1620 1628 1620 1612 1597 1658 1620
Bending or
deformation
mode of NAH
NAN stretching
symmetric
–
1504
–
–
1504 1550 1504 1535 1520 1520
vibrations
NAN stretching
asymmetric
vibrations
1435 1458 1442
–
–
–
–
CAH stretching
vibrations
1381 1381 1381 1381 1388 1388 1381 1381
C@O stretching
vibrations
Out of plane CAH
Bending
Monosubstituted
benzene
NAH oscillation
1303 1288 1304 1280 1273
–
910
825
532
1273 1304
–
841
–
–
864
557
–
856
517
949
802
508
–
864
532
–
856
517
–
810
532
Fig. 8. Proposed silver position after the silver complex formation.
Fig. 10. Peak height temperature dependence of the IR modes 517 cmꢁ1, 1273 cmꢁ1
and 1342 cmꢁ1 during the high temperature phase transition in DPCAg at 167 °C.
Fig. 9. Infrared spectra of DPCAg complex at room temperature (R.T. ꢂ 30 °C),
150 °C and 200 °C.
vided that the increase in temperature does not change the num-
of a band remains constant for fairly large changes in temperature
until the transition temperature is reached.
ber of ions initially being in the vibrational level
m = 0. The area

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259
Fig. 12. Variation of the peak intensity of the monosubstituted benzene at
810 cmꢁ1 and asymmetric stretching of NAH at 3440 cmꢁ1 with temperature for
DPCAg.
Within this second class there are stretching and bending vibrations
which involve heavy atoms such as metal–oxygen and hindered
rotation of ligands attached to central metal atom.
Fig. 11. Peak height changes of the modes 1628 cmꢁ1, 3124 cmꢁ1 and 3186 cmꢁ1
during the high temperature phase transition in DPCAg at 167 °C.
Conclusion
References
In conclusion, the infrared spectroscopy was successfully used
for the prediction of the glass transition at 91 °C and high temper-
ature phase transition point at 167 °C for the silver complex
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a single unit cell, these
vibrations are often observed as broad peaks which represent a
composite band of several vibrations. For such compounds the
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the frequency of absorption. However, a regular change in fre-
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polarizing power of the cation.
For those lattice containing complex molecules, the vibrations
likely to be observed in the IR spectrum arise from two sources:
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(i) Molecular lattice vibrations which would occur at very low
frequencies due to the mass of the molecule.
(ii) Internal vibrations of the molecules.