New energetic Silver(I) complexes with Nnn type Pyrazolylpyridine ligands and oxidizing anions

Article abstract of DOI:10.1016/j.molstruc.2020.128001

The high energy complexes [Ag (pp) (NO₃)] (I), [Ag (dmpp) (NO₃)] (II), [Ag (pp)ClO₃)] (III), [Ag (dmpp) (ClO₃)] (IV), [Ag (pp) (ClO₄)] (V), [Ag (dmpp) (ClO₄)] (VI) were synthesized from the ligands, Bis-2,6(Pyrazol-1-yl)Pyridine (pp) and Bis-2,6 (3,5-dimethylpyrazol-1-yl)Pyridine (dmpp). They were characterized via IR spectroscopy and elemental analysis. Suitable single crystals of complexes I, IV and VI have been obtained and their molecular structures were determined by X-Ray diffraction methods. The X-Ray study revealed that these complexes were di-nuclear. All complexes have been analyzed by TG-DTA. It was determined that they decompose exothermically in explosive reactions. Elevation in the thermal decomposition temperature, enthalpy of reaction and mass loss was observed with increasing number of oxygens within the anion in the complex structure. The HOMO and LUMO energy levels of the complexes, together with the theoretical formation enthalpies, were calculated by using Gaussian 09 software package whereas the enthalpies of thermal decomposition were measured by DSC. The products of decomposition were predicted from the theoretical formation enthalpy and the measured heat of reaction values according to Hess’ law. It was observed that the thermogravimetry plots of complexes I, II and VI were suitable for thermo-kinetics investigation. Thus, they were analyzed by means of isothermal (Coats-Redfern) and non-isothermal-isoconvertional (Flyn-Ozawa-Wall and Kissinger-Akahira-Sunose) methods and certain thermodynamic parameters were calculated. It was discovered that all complexes except complex II decomposed with rapid, single step reactions whereas complex II decomposed with a 2-step reaction.

Full text of DOI:10.1016/j.molstruc.2020.128001

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New Energetic Silver(I) Complexes With Nnn Type Pyrazolylpyridine Ligands And
Oxidizing Anions
Arda Atakol, Ingrid Svoboda, Hakan Dal, Orhan Atakol, Hasan Nazır
PII:
S0022-2860(20)30326-4
DOI:
https://doi.org/10.1016/j.molstruc.2020.128001
MOLSTR 128001
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Accepted Date:
20 July 2019
03 March 2020
Please cite this article as: Arda Atakol, Ingrid Svoboda, Hakan Dal, Orhan Atakol, Hasan Nazır,
New Energetic Silver(I) Complexes With Nnn Type Pyrazolylpyridine Ligands And Oxidizing
Anions, Journal of Molecular Structure (2020), https://doi.org/10.1016/j.molstruc.2020.128001
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New Energetic Silver(I) Complexes With Nnn Type Pyrazolylpyridine Ligands And
Oxidizing Anions
1
*
2
3
4
4
Arda Atakol , Ingrid Svoboda , Hakan Dal , Orhan Atakol , Hasan Nazır
1
2
3
4
Turkish Standards Institution, Construction Materials Fire and Acoustics Laboratory, Istanbul, Turkey
Strukturforschung, FB Materialwissenschaft, TU- Darmstadt, Petersenstrasse 23, D-64287, Darmstadt, Germany
Anadolu University, Faculty of Science, Department of Chemistry, Eskişehir, Turkey
Ankara University, Faculty of Science, Department of Chemistry, 06100 Ankara, Turkey
Abstract
The high energy complexes [Ag(pp)(NO )] (I), [Ag(dmpp)(NO )] (II), [Ag(pp)ClO )] (III),
3
3
3
[
Ag(dmpp)(ClO )] (IV), [Ag(pp)(ClO )] (V), [Ag(dmpp)(ClO )] (VI) were synthesized from
3 4 4
the ligands, Bis-2,6(Pyrazol-1-yl)Pyridine (pp) and Bis-2,6(3,5-dimethylpyrazol-1-yl)Pyridine
dmpp). They were characterized via IR spectroscopy and elemental analysis. Suitable single
(
crystals of complexes I, IV and VI have been obtained and their molecular structures were
determined by X-Ray diffraction methods. The X-Ray study revealed that these complexes
were di-nuclear. All complexes have been analyzed by TG-DTA. It was determined that they
decompose exothermically in explosive reactions. Elevation in the thermal decomposition
temperature, enthalpy of reaction and mass loss was observed with increasing number of
oxygens within the anion in the complex structure. The HOMO and LUMO energy levels of
the complexes, together with the theoretical formation enthalpies, were calculated by using
Gaussian 09 software package whereas the enthalpies of thermal decomposition were measured
by DSC. The products of decomposition were predicted from the theoretical formation enthalpy
and the measured heat of reaction values according to Hess’ law. It was observed that the
thermogravimetry plots of complexes I, II and VI were suitable for thermo-kinetics
investigation. Thus, they were analyzed by means of isothermal (Coats-Redfern) and non-
isothermal-isoconvertional (Flyn-Ozawa-Wall and Kissinger-Akahira-Sunose) methods and
certain thermodynamic parameters were calculated. It was discovered that all complexes except
complex II decomposed with rapid, single step reactions whereas complex II decomposed with
a 2-step reaction.
Keywords: high energy materials; heat of decomposition; thermo-kinetic analysis; X-Ray
diffraction; thermal decomposition; DFT calculation
1

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Introduction
Pyrazolyl pyridines have been a notable class of ligands since their introduction to the literature
in 1990 [1]. They are NN and NNN type ligands similar to terpyridine but their preparation
requires less effort than terpyridine derivatives. For this reason, pyrazolyl pyridines are
commonly seen in coordination chemistry literature [2–17]. On the other hand, recent research
on high energy materials focuses on synthesis of nitrogen rich molecules. Having a nitrogen
rich ligand, novel pyrazolyl pyridine complexes could be good energetic material candidates
[18–20]. In addition, it has long been known that certain silver (I) salts and simple silver (I)
complexes exhibit explosive behavior [21–26]. As is known, explosives have been defined in
the class of energetic substances for nearly 20 years.
In the light of this knowledge, two pyrazolyl pyridine ligands, Bis-2,6(Pyrazol-1-yl)pyridine
(
pp) and Bis-2,6(3,5-dimethylpyrazol-1-yl)pyridine (dmpp), were prepared and their Ag (I)
complexes, namely [Ag(pp)(NO )] (I), [Ag(dmpp)(NO )] (II), [Ag(pp)(ClO )] (III),
Ag(dmpp)(ClO )] (IV), [Ag(pp)(ClO )] (V), [Ag(dmpp)(ClO )], were synthesized by using
3
3
3
[
3
4
4
AgNO , AgClO and AgClO in MeOH (Figure 1). The complexes were first characterized.
3
3
4
Their compositions were determined by elemental analysis and their functional groups by
IR spectroscopy. Then, they were investigated by thermogravimetry (TG) and differential
scanning calorimetry (DSC). Results of TG and elemental analyses revealed that complexes I,
V and VI bound solvent molecules (H O and MeOH) within their crystal structure. Complexes
2
I, IV and VI have been obtained in suitable single crystal form, thus and so, their solid-state
molecular structures were determined by X-Ray diffraction methods.
TG data indicated that all complexes excluding complex II gave rapid thermal decomposition
reactions. Thermo-kinetic analyses have been conducted on complexes I, II and VI. It was
revealed that complex II exhibited a 2-step thermal decomposition. On the other hand, the other
complexes decomposed very rapidly which makes the data non-workable for such analysis.
o
-1
Luckily, data obtained with heating rates below 10 C.min for complexes I and VI was useable.
Two different approaches were employed for thermo-kinetic analysis, namely, isothermal Coats
Redfern (CR) method [27–30] and non-isothermal-isoconvertional Kissinger-Akahira-Sunose
(KAS) [31–37] and Flynn-Ozawa-Wall [33–39] methods.
In addition, the effect of oxidative anion within the complex to the thermal decomposition
temperature and enthalpy was investigated. In recent literature, there has been a few studies
with similar approaches [24, 25]. Karaghiosoff et al. reports complexes prepared from AgNO3
and AgClO with the ligand 5-amino tetrazole. It is suggested that the performance of ClO4-
4
complexes were even comparable to primary explosives. It was also noted that the thermal
stability order is ClO4- > NO [24]. In another study, Tao et al. employed 5-(1-
3
methylhydrazinyl)tetrazole as ligand and its complex with AgNO was synthesized. This
3
complex was reported to have low impact sensitivity and high thermal stability [25].
Theoretical calculations on the synthesized complexes were conducted by employing the 6-
3
11++(2d,2p)//6-31G(d) basis sets using DFT/B3LYP/GENECP method in the Gaussian 09
software package [40]. NBO algorithm was used to find the d orbital occupancy values of the
2

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central atom from both the optimization data and the experimental X-ray findings. The HOMO
and LUMO energy levels of the complexes were calculated by Lanl2DZ:6-311++(2d,2p) basis
set and their stabilities were interpreted. Theoretical formation enthalpies at standard conditions
were calculated at the same level of theory by using the atomization theory [42]. Finally, the
calculated formation enthalpies and the decomposition enthalpies that were experimentally
-1
determined at 10 °C.min heating rate measured by DSC were combined in accordance with
the Hess’ law to predict the decomposition products.
X
Y
N
N
N
N
N
X
Y
X = Y = H
Bis-2,6(Pyrazol-1-yl)pyridine (pp)
X = Y = CH Bis-2,6(3,5-dimethylpyrazol-1-yl)pyridine (dmpp)
3
X
X
Y
Y
N
N
N
N
Ag
N
A
X = Y = H
A = NO3
[Ag(pp)(NO )] (I)
3
X = Y = CH A = NO
[Ag(dmpp)(NO )] (II)
3
3
3
X = Y = H
A = ClO3
[Ag(pp)(ClO )] (III)
3
X = Y = CH A = ClO
[Ag(dmpp)(ClO )] (IV)
3
3
3
X = Y = H
A = ClO4
[Ag(pp)(ClO )] (V)
4
X = Y = CH A = ClO
[Ag(dmpp)(ClO )] (VI)
3
4
4
Figure 1 General formulae of the synthesized ligands and complexes
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Experimental
Apparatus
Ag analyses were performed with a GBC Avanta PM atomic absorption spectrophotometer.
The complex (2–3 mg) was dissolved in a mixture of 1 mL HNO (63%) and 1mL H O (30%)
3
2
2
by heating. Then, the mixture was diluted to 100 mL in a volumetric flask. The final solution
was directly introduced to the nebulizer of atomic absorption instrument for the analysis of the
metal content.
IR spectra were recorded on a Shimadzu Infinity spectrometer equipped with a three reflection
-1
ATR unit, all IR spectra were recorded at a resolution of 4 cm .
Thermal analyses were conducted with Shimadzu DTG 60H and Shimadzu DSC 60. They were
o
-1
performed under N atmosphere with a heating rate of 10 C min and in Pt pans. The
2
temperature and heat calibrations of TG was carried out using In and Zn metals and DSC was
calibrated using In.
The NMR spectra of the ligands were recorded on a Varian Mercury 400MHz NMR
spectrometer in d -DMSO. C, H, N elemental analysis were carried out using Eurovector 3018
6
CHNS analyzer.
Mass spectra of the ligands were recorded on a Shimadzu 2010 Plus GCMS apparatus equipped
with a Direct Inlet unit.
X-Ray Analyses
Single crystals of complexes I, IV and VI were analyzed with an Oxford Diffraction Xcalibur
(
TM) Single Crystal X-ray Diffractometer with a sapphire CCD detector using MoK radiation
α
(λ=0.71073 Å) operating in the ω/2θ scan mode. The unit-cell dimensions were determined and
refined by using the angular settings of 25 automatically centered reflections in 2.5526.32
range. The empirical absorption corrections were applied by the semi-empirical method via the
CrysAlis CCD software [42]. Models were obtained from the results of the cell refinement and
the data reductions were carried out using the solution software SHELXL97. The structures of
the complexes were resolved by direct methods using the SHELXS97 software implemented in
the WinGX package [44].
Preparation of the Ligands
The ligands were prepared following the procedures explained in the study reported by Jameson
and Goldsby [1].
Preparation of pp: 6.8 g (0.1 mol) pyrazole was dissolved in 100 mL dry dimethyl diethylene
glycol (diglym) by stirring at 40 °C. To this solution, added was 2.4 g (0.105 mol) freshly cut
metallic Na pieces. The solution was stirred under N atmosphere for approximately 4 hours to
2
obtain Na-pyrazolate. The remaining Na metal was removed and 7.4 g (0,05 mol) 2,6-
dichloropyridine solid was added. The temperature was raised to 110 °C and the solution was
stirred for a day. It was cooled and directly poured on 500 mL water-ice mixture. The white
precipitate was filtered and dried in an oven at 80 °C. The product was recrystallized in MeOH
:
H O (2:1, v:v) mixture.
2
4

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C H N | Melting point: 135–137 °C, Yield: between 68% and 74% (in 5 repetitions).
1
1
9
5
Elemental analysis: Expected mass percentages C: 62.55, H: 4.29, N: 33.15 Experimental
mass percentages C: 61.94, H: 4.11, N: 32.87
-1
IR Data (cm ): ν
1603, νC=C(ring): 1583, νC-H(Ar): 3110–3165, δCH3= 1479–1458, δC-H =
C=N(ring):
7
63
1
H-NMR data, in d -DMSO (δ, ppm)
6
6
.63 multiplet (2H), 7.82 doublet-doublet (4H), 8.15 triplet (1H), 8.95 doublet (2H)
1
3
C-NMR data, in d -DMSO (δ, ppm)
6
1
08.0, 109.4, 127.3, 142.0, 143.1, 151.2
MS data (m/z)
11 (base peak, molecular peak), 144, 117
2
Preparation of dmpp: Similar to the preparation of pp, dmpp was prepared from 9.6 g (0.1
mol) 3,5-dimethyl pyrazole.
C H N | Melting point: 107–108 °C, Yield: between 75% and 85 % (in five repetitions).
1
5
17
5
Elemental analysis: Expected mass percentages C: 67.40, H: 6.41, N: 26.19; Experimental mass
percentages C: 67.23, H: 5.89, N: 26.54.
-1
IR Data of dmpp (cm ): νC=N(ring)= 1596, νC=C(ring) = 1587, νC-H(Ar) = 3102–3130, νC-H(Aliph)
=
2
880–2958, δCH3= 1473–1425, δC-H = 791
1
H-NMR data, in d -DMSO (δ, ppm)
6
2
.20 singlet (6H), 2.55 singlet (6H), 6.15 singlet (2H), 7.68 doublet (2H), 8.05 triplet (1H)
1
3
C-NMR data, in d -DMSO (δ, ppm)
6
1
4.0, 14.5, 109.0, 115.4, 140.1, 141.1, 150.1, 156.0
MS data (m/z)
67 (base peak, molecular peak), 252, 225, 211, 173,147, 95
Preparation of AgClO : 5.1 g (0,03 mol) AgNO was dissolved in 100 mL water by heating
2
3
3
until boiling point. 3.2 g (0,03 mol) NaClO was added to this solution and the mixture was
3
allowed to stand for 24 hours in a dark cabinet. After this period, the solution was cooled in ice-
water bath and the white crystalline precipitate was filtered, rinsed with EtOH and dried in air
[45].
Preparation of AgClO : 5.1 g (0,03 mol) AgNO was dissolved in approximately 200 mL
4
3
water by heating until boiling point. To this solution, 50 mL NaOH solution in hot water was
added. Black precipitate, AgOH, was vacuum filtered with a black ribbon filter paper and it
was rinsed with water. The precipitate was dried in an oven at 80 °C. The dried solid was added
to 25 mL 60% HClO in a flask. The mixture was allowed to evaporate until half volume in a
4
sand bath to make sure that the temperature would not exceed 150 °C. Then the mixture was
5

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cooled in an ice-water bath. The white crystalline precipitate was filtered through a fritted glass
filter with G3 porosity, was rinsed with Et O and dried in vacuum [45]. The purity of the product
2
was checked gravimetrically with the help of KClO precipitation.
4
Preparation of the complexes: All complexes were prepared from the corresponding reactants
by the following procedure. 0.004 mol ligand was dissolved in MeOH by mildly heating. To
this solution, the solution of 0.004 mol Ag(I) salt in hot water was added. The new solution was
allowed to stand for 2–3 days. The white crystalline precipitate was filtered and dried in air. All
yields were found to be lower than 30%. The used AgNO was of commercial preparation.
3
Elemental analysis results and essential FTIR data of the complexes were given in Table 1.
Table 1 Elemental analysis results and essential FTIR data of the complexes
Elemental analysis results
Complex
Essential IR Data
Calculated % (wt)
Experimental % (wt)
ν
ν
ν
ν
δ
ν
C-H(Ar): 3130–3114
C=N(ring): 1601
C=C(ring): 1565
N=O: 1347
C: 33.10
H: 2.78,
N: 21.05
Ag: 27.03
C: 34.72
H: 3.11
N: 21.17
Ag: 27.56
[
[
[
[
[
[
3 2
Ag(pp)(NO )].H O (I)
C-H(Ar): 758
C-H(Ar): 3124–3113
C: 41.21
H: 3.91
N: 19.21
Ag: 24.62
C: 40.53
H: 4.29
N: 17.96
Ag: 24.33
νC-H(Aliph): 2988-2890
ν
ν
ν
δ
ν
ν
ν
ν
δ
ν
C=N(ring): 1598
C=C(ring): 1567
N=O: 1355
3
Ag(dmpp)(NO )] (II)
C-H(Ar): 798
C-H(Ar): 3113–3119
C=N(ring): 1604
C=C(ring): 1583
Cl-O: 1047
C: 32.82
H: 2.25
N: 17.39
Ag: 26.80
C: 33.21
H: 2.30
N: 17.02
Ag: 26.35
3
Ag(pp)(ClO )] (III)
C-H(Ar): 749
C-H(Ar): 3122
C: 39.28
H: 3.73
N:15.26
Ag: 23.53
C: 38.72
H: 3.98
N: 15.77
Ag: 22.34
νC-H(Aliph): 2985–2922
C=N(ring): 1593
3
Ag(dmpp)(ClO )] (IV)
ν
ν
δ
ν
ν
ν
ν
δ
ν
ν
ν
ν
ν
δ
C=C(ring): 1559
Cl-O: 975
C-H(Ar): 804
C-H(Ar): 3153–3077
C=N(ring): 1603
C=C(ring): 1586
Cl-O: 1057
C: 31.98
H: 2.90
N: 15.53
Ag: 23.94
C:31.08
H:2.96
N:15.13
Ag:24.83
4
Ag(pp)(ClO )].MeOH (V)
C-H(Ar): 763
C-H(Ar): 3116–3120
C-H(Aliph): 2991–2875
C=N(ring): 1595
C=C(ring): 1560
Cl-O: 1047
C: 37.92
H: 4.17
N: 13.81
Ag: 21.29
C: 37.99
H: 3.74
N: 13.91
Ag: 22.01
4
Ag(dmpp)(ClO )].MeOH (VI)
C-H(Ar): 748
6

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Thermo-kinetic Analysis
Kinetic analyses for the decomposition reactions of compounds I, II and VI were carried out by
applying KAS, FOW and Coats-Redfern methods to thermograms recorded at different heating
-1
rates. Heating rates of 1.0, 5.0, 10.0, 15.0, 20.0 and 25.0 °C.min were used for complex I; 1.0,
-
1
-1
5
1
.0, 10.0, 15.0, 20.0 °C.min for complex II; 1.0, 2.0 and 5.0 °C.min for complex VI. Since
-1
.0 °C.min heating rate leads to lnβ = 0, the other heating rates were taken into account for
-1
FOW and KAS calculations where 1.0 °C.min was used in CR calculations. FOW calculation
was not applicable to complex VI because there was not enough data at three usable heating
rates. The fact that the complex decomposes very rapidly makes increasing the heating rate not
viable.
The activation energies and pre-exponential factors were calculated with the help of graphical
methods by using the temperatures corresponding to g(α) values 0.2, 0.4, 0.5, 0.6 and 0.8 at
different heating rates according to both KAS and FOW methods. On the other hand, CR
calculations were done at each heating rate for different g(α) values seperately.
The calculations were made from the plots of KAS (1), FOW (2) and CR (3) equations given
below [27–39]:
훽
퐴 퐸
푎
퐸
푎
푙푛 = 푙푛
― 푅푇
1
2
푇
푅 푔(훼)
0
.0048 퐴 퐸
푎
퐸
푎
푙푛훽 = 푙푛
―1.0516푅푇
2
3
푅 푔(훼)
푔(훼)
퐴푅
2푅푇
퐸
푎
푙푛 푇2
= 푙푛[훽퐸
(
1 ―
)
] ― 푅푇
푎
퐸
푎
2
푅푇
Because that the term 퐸훼 is ≤ 0.1 in most cases, including this one as indicated by the results,
equation 3 can be rearranged as follows:
푔(훼)
퐴푅
퐸
푎
푙푛 푇2 = 푙푛[훽퐸
]
― 푅푇
4
푎
-
1
-1 -1
In the equations; β is the heating rate (°C.min ), R is the universal gas constant (J.mol .K ) ,
-1
E is the activation energy for thermal decomposition (J.mol ), A is the Arrhenius pre-
exponential factor (min ), T is the temperature (K) and g(α) is the fraction of completion of the
a
-1
decomposition reaction. Note that these methods assume that the reaction order is 1. As each
훽
푔(훼)
푇2
1
of these methods suggest, plots of lnβ, ln and ln
against were obtained. E and A values
2
a
푇
푇
were calculated using the slope and the intercept respectively.
7

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In addition; the thermodynamic parameters, change in entropy, change in enthalpy and Gibbs
free energy for the thermal decompositions were calculated from E and A values. The entropy
a
change in a thermal reaction can be approximated by using the pre-exponential factor [28]:
퐴ℎ
푙표푔푘푇
훥푆 = 2.303
(
)
푅
5
The change in enthalpy is calculated from the activation energy as per the first rule of
thermodynamics:
훥퐻 = 퐸 ―푅훥푇
6
푎
Then the Gibbs free energy can be calculated from these parameters:
훥퐺 = 훥퐻 ― 푇훥푆
7
Theoretical Calculations
In this study, the theoretical calculations were done with the help of Gaussian 09 (Revision-
D.01). GaussView 5.0.9 was used for evaluating and expressing the results [40]. In graphical
representation of HOMO-LUMO energy levels and orbital fragment analysis, Chemissian Ver.
4
.38 was used [46].
The optimization and frequency analysis calculations were done by applying Density
Functional Theory (DFT). B3LYP (Becke-3-Lee-Yasng-Parr exchange-correlation) functional
was used with GenECP variation which is suitable to define two basis functions and ECPs in
one calculation. In the GenECP identification, LanL2DZ basis set was used for Ag atoms where
6
-31G(d) was used for the others. Frequency analysis at the same level of theory made it
possible to both check the stabilization of the optimized structures by the number of imaginary
frequencies, NImag - local minima (NImag=0) and calculate the theoretical enthalpies of
formation. The atomization energy approach was employed to calculate the formation
enthalpies (Equation 8).
Δ H° (g,M) = H (M) – Σ H° + Σatoms ΔfH°
atoms
8
f
298
In equation 8, Δ H°(g, M) stands for the gas-phase enthalpy of formation of the molecule M,
f
under investigation; H(M) represents the DFT/B3LYP/LanL2DZ:6-31G(d) calculated enthalpy
of the molecule M; ΣatomsH° denotes the sum of DFT/B3LYP/LanL2DZ:6-31G(d) calculated
enthalpies for the individual atoms (1 a.u.=2625.50 kJ mol-1) and Σatoms Δ H° is the sum of
f
the standard formation enthalpies of individual atoms taken from NIST database [47].
In addition, the electron density distribution among the atoms of the optimized structures,
HOMO-LUMO energy levels and electrostatic potential were determined by using the same
method with the basis set LanL2DZ:6-311++G (2d, 2p). The oxygen balance is calculated by
using equation 9 where % is the oxygen balance; a, b, c and n are the numbers of C, H, O and

metal atoms respectively and M is the molecular weight of the complex in question. The
theoretical heat (Q) was calculated by using the extended Kamlet-Jacobs equation [48].
8

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푐 ― 2푎 ― 푏
2
― 푛
% = 1600
9
푀
Results and Discussion
The thermo-analytical data deducted from the TG-DTA study was given in table 2. TG results
reveal the mass loss corresponding to the evaporation of a H O molecule bonded as hydrate to
2
complex 1 and of a MeOH molecule bonded as solvate to the complexes V and VI. Apparently,
the νO-H bending bands in IR spectrometry results given in table 1 belongs to these solvates.
There is a certain anomaly in the TG curves of complexes III and IV and V. The slopes of the
curves are positive in mass loss regions. Similarly, this is also noticed as deformed signals in
the DTA curves which highly diverge from the Gaussian type. The reason for this occurrence
is the extreme rapidity of the decomposition reactions. The gaseous products of the reaction
leave the medium so fast that they drag away the heat along with them. During this very small
time frame the pan temperature remains smaller than the oven temperature. The TG method
measures mass loss as well as temperature difference between sample and reference and this
causes a positive slope in the mass curves and an obvious anomaly in 2-dimensional DTA plots,
but this kind of an anomaly is not observed in DSC curves. Unfortunately, in these cases,
thermo-kinetic analysis is not applicable. Thus, only complexes I, II and VI were thermo-
kinetically investigated.
TG results reveal that complexes I, V and VI have a volatile solvate molecule. Mass loss results
show that the solvate molecule is H O in complex I and MeOH in V and VI. The νO-H bands of
2
these molecules can be seen in the IR spectra. Unexpectedly, the cleavage of MeOH from
complexes V and VI occurred at around 200 °C.
The data in table 2 indicate that the complexes decompose very rapidly between 200 and 400
°
C. It is highly probable that the residue is predominantly Ag O and elemental carbon.
2
Unfortunately, in these cases, the mass readings of the residue are incidental and non-repeatable
because some amount of the products are scattered into the oven by the rapid reaction which is
comparable to an explosive detonation. For this reason, the readings of mass of the residue
cannot be used in interpreting the thermogravimetry results.
9

Table 2 Thermo-analytical data
Complex Loss of a MeOH or a H O molecule (Where applicable) Thermal decomposition
Heat of reaction
measured by
DSC (kJ.mol )
2
-1
-1
Heating rate(°C.min ) /
Temperature range °C / DTA
peak
Expected mass loss / Heating rate (°C.min ) /
Recorded mass loss %
-1
found mass loss %
Temperature range
°C/DTA peak
[
[
[
Ag(pp)(NO )].H O (I) 1 / 91.75 – 141.60 / 126.54
4.51 / 4.92, 4.55, 4.61,
1 / 191.59 – 216.58 / 208.03
5 / 184.25 – 243.02 / 224.27
10 / 209.64 – 268.05 / 242.36
15 / 218.92 – 270.88 / 255.42
20 / 225.46 – 275.56 / 258.98
25 / 231.43 – 278.27 / 257.85
1 / 240.06 – 273.73 / 258.47
35.37, 42.44, 36.91,
37.19, 36.67, 37.95
410.29 ± 8.42
3
2
4
.51, 4.41, 4.73
5
1
1
2
2
/ 94.83 – 154.85 / 131.17
0 / 129.14 – 157.66 / 142.95
5 / 136.66 – 177.65 / 148.56
0 / 144.90 – 178.55 / 151.32
5 / 132.96 – 183.23 / 151.67
Mean: 4.61 ± 0.18
Mean: 37.76 ± 2.44
Ag(dmpp)(NO )] (II) (-)
(-)
63.59, 70.23, 65.03,
579.11 ± 19.87
3
6
5.46, 65.75, 64.23
5
1
1
2
2
/ 278.14 – 294.48 / 286.48
0 / 284.99 – 309.13 / 295.69
5 / 289.32 – 316.22 / 307.44
0 / 294.87 – 320.86 / 311.41
5 / 295.46 – 331.73 / 316.28
Mean: 65.72 ± 2.35
Ag(pp)(ClO )] (III)
(-)
(-)
1 / 188.32 – 210.07 / 206.14
47.23, 64.14, 54.05,
548.33 ± 11.44
3
6
2.49, 60.12, 58.28
5
1
1
2
2
/ 196.84 – 211.35 / 207.91
0 / 273.24 – 294.38 / 284.21
5 / 276.21 – 294.38 / 286.75
0 / 279.36 – 298.42 / 288.13
5 / 280.42 – 296.74 / 289.04
Mean: 57.72 ± 6.21
1
0

Table 2 (Continued)
Complex
Loss of a MeOH or a H O molecule (Where applicable) Thermal decomposition
Heat of reaction
measured by
DSC (kJ.mol-1)
2
-1
-1
Heating rate(°C.min ) /
Temperature range °C / DTA
peak
Expected mass loss / Heating rate (°C.min ) /
Recorded mass loss %
90.03, 82.82, 83.78,
found mass loss %
Temperature range
°C/DTA peak
[
Ag(dmpp)(ClO )]
(-)
(-)
5 / 267.48 – 287.07 / 282.89
692.79 ± 13.78
1001.71 ± 33.37
1348.00 ± 9.50
3
8
2.17, 82.14
(IV)
1
1
2
2
0 / 275.75 – 296.89 / 292.63
5 / 280.56 – 300.57 / 298.37
0 / 281.35 – 302.18 / 297.13
5 / 289.28 – 311.56 / 306.92
Mean: 84.18 ± 4.07
[
Ag(pp)(ClO )].MeOH 5 / 184.74 – 206.46 / 193.88
9.12 / 9.97, 9.21, 9.04,
5 / 320.90 – 338.52 / 335.05
10 / 331.36 – 347.93 / 343.75
15 / 337.83 – 350.26 / 345.86
20 / 342.41 – 362.54 / 356.14
25 / 343.17 – 362.86 / 353.83
1 / 305.46 – 337.83 / 330.60
5 / 308.17– 343.28 / 340.18
10 / 372.70 – 397.97 / 389.72
15 / 383.65 – 399.44 / 395.18
20 / 386.31 – 402.45 / 401.19
25 / 390.48 – 408.65 / 406.74
72.24, 76.89, 78.35,
80.34, 78.90
4
9
.16, 9.11
(V)
1
1
2
2
0 / 185.63 – 216.52 / 207.34
5 / 198.28 – 232.26 / 220.21
0 / 204.98 – 242.73 / 220.97
5 / 204.61 – 242.66 / 219.41
Mean: 9.29 ± 0.38
Mean: 77.34 ± 3.11
[
Ag(dmpp)(ClO )].
1 / 190.11 – 231.09 / 212.84
7.86 / 7.58, 6.98, 7.25,
50.59, 84.12, 91.17,
80.64, 83.55, 88.89
4
7
.55, 7.55, 7.96
MeOH (VI)
5
1
1
2
2
/ 191.07 – 230.16 / 210.64
0 /190.94 – 229.84 / 208.74
5 / 201.50 – 247.48 / 233.82
0 / 202.56 – 253.25 / 234.65
5 / 203.36 – 256.55 / 238.15
Mean:7.47 ± 0.32
Mean: 85.67 ± 4.26
1
1

Journal Pre-proof
It was determined that the thermal decomposition in all complexes except complex II takes
place in a single step where complex II decomposes with a two-step reaction. The two steps
-1
were only detected when the heating rate was 10 °C.min or lower. The TG-DTA plots of this
-1
complex recorded at 5 and 10 °C.min were given in figure 2a and 2b. When examined
carefully, the DTA curves remark the two exothermic signals whereas a single exothermic
-1
signal is observed when the heating rate is 25 °C.min . For this reason, thermo-kinetic
calculations are separately carried out for the individual steps. On the other hand, complex I
and VI exploded in single step reactions regardless of the heating rate. The thermo-kinetically
analyzed data was collected at lower heating rates. This was essential because of the rapid
nature of the thermal decomposition reactions; especially, the decomposition of complex VI
-1
which yields a mass loss curve with a positive slope at heating rates over 10 °C.min .
-1
Figure 2a TG-DTA curves of Complex II recorded at 5 °C.min , [Ag(dmpp)(NO )]
3
-1
Figure 2b TG-DTA curves of Complex II recorded at 10 °C.min , [Ag(dmpp)(NO )]
3
1
2

Journal Pre-proof
The kinetic analysis parameters which were calculated from the graphs, activation energy (Ea)
and Arrhenius pre-exponential factor (A) were given in Table 3. Thermodynamic parameters,
-1
calculated by using the mean of E values and A values calculated for 10 °C.min heating rate,
a
were given in Table 4. Table 3 does not include FOW results for complex VI because the
variation in heating rates was involuntarily limited, because any result recorded at over 10
-
1
°
C.min was unusable. It was also not possible to use lower rates since FOW method involves
-1
plotting against lnβ which is 0 or negative for heating rates equal to or below 1 °C.min .
FOW and KAS methods yielded comparable results where the variation in the value of A at
different heating rates is reasonable. Nevertheless, CR results fall far from the others and the A
value differed by large margins at various heating rates. These results imply the superiority of
the non-isothermal isoconvertional methods. This was not unexpected considering the fact that
International Confederation for Thermal Analysis (ICTAC) recommends the use of only non-
isothermal methods in this field [49].
The stoichiometry in the solvated complexes was predicted by using the mass loss values given
in the first two columns of Table 2. The mass losses of the thermal decomposition reactions for
all complexes were given in the third and fourth columns where the last column involves the
reaction enthalpies. In these results, the first thing to notice is the similarity in decomposition
temperatures of nitrate and chlorate complexes. The second one is that the heat of
decomposition and mass loss values were found to be significantly higher in the complexes
containing dmpp.
The temperature interval at which the rapid thermal decomposition occurs in pp complexes is
-
-
2
3
40–260 °C where the co-ligand is NO , it is 280–290 °C where the co-ligand is ClO and it is
3 3
-
40 – 360 °C where the co-ligand is ClO . On the other hand, the temperatures were found as
follows for dmpp complexes; 307–315 °C with co-ligand NO , 290 – 305 °C with co-ligand
ClO and 390 – 400 °C with co-ligand ClO . It seems clear that ClO complexes decompose
4
-
3
-
-
-
3
4
4
at significantly higher temperatures. This can be explained, simply by referring to the structure
-
of the bonds between co-ligand oxygen atoms and the Ag atom. The Ag – ClO bond is
4
undoubtedly the one with the highest ionic character. The oxygen atoms of other co-ligands
form less ionic bonds with the central atom. For this reason, it is the Ag – O – ClO bond which
3
has the highest thermal stability.
The formal charges of the oxidizing anions were also calculated with the help of NBO
calculations. The formal charges of the two different NO groups in complex I were calculated
3
as -0.856 and -0.855 respectively. In complex II, the formal charge of NO groups is -0.851; In
3
complex III, the formal charge of ClO groups is -0.773; in complex IV, the formal charge of
3
ClO groups is -0.796; in complex V the formal charge of ClO groups is -0.856 and in complex
3
4
VI, the formal charge of ClO groups is -0.881. The more negative formal charges on the
4
perchlorate ions compared to the formal charges on chlorate ions indicate that the ionic
character is higher in perchlorate complexes. This is in support of the thermoanalytical data
given in table 2. The perchlorate complexes decompose at higher temperatures with more
exothermic enthalpies. Similarly, the nitrate complex involving dmpp ligand decompose at a
1
3

Journal Pre-proof
slightly higher temperature than the dmpp-chlorate complex. It is plausible that the more
negative charge on the oxidizing ion is responsible for the elevated temperature of thermal
decomposition. On the other hand, nitrate and chlorate complexes that involve pp ligand behave
differently. However, such comparisons with complex I is questionable from the beginning
since it has a different coordination sphere.
One of the fundamental, desired properties in energetic materials is that they remain thermally
stable up to temperatures as high as possible [50]. Another issue to consider is the reason of the
greater magnitude of the decomposition temperatures in dmpp complexes. The electron density
of donor nitrogen atoms is elevated with the effect of four methyl groups in the ligand.
Therefore, they could donate electrons to the central atom more easily. In other words, dmpp is
stronger a ligand than pp. The coordination bonds it forms have higher stability and they could
resist higher temperatures. Like the heat of thermal decompostion, mass loss also gets larger in
compounds which decompose at higher temperatures. This is apparent in the results given in
Table 2.
Table 3 Ea and A values calculated by using the graphs of thermo-gravimetry data
Complex
FOW
KAS
CR
Ea
A
Ea
A
E
A
-
1
(min-1)
(kJ.mol-1)
(min-1)
(kJ.mol-1)
(min-1)
7.97.108
(
kJ.mol )
g(α)=0.2
0.03
g(α)=0.4
1.04
g(α)=0.5
8.06
g(α)=0.6
8.80
g(α)=0.8
3.77
g(α)=0.2
122.63
Ɵ=1
[
Ag(pp)(NO )].H O
3 2
7
1.64.106
3.45.106
1.93.106
250.106
8.45.106
.50.103
3
2
5
8
107.06
Ɵ=5
g(α)=0.4
3.12.1014
7
119.80
g(α)=0.5
.55.103
.87.102
.33.102
152.68
Ɵ=10
171.47
Ɵ=15
141.75
Ɵ= 20
169.98
Ɵ= 25
7.00.1014
1.64.1014
1
13.45
g(α)=0.6
14.96
g(α)=0.8
14.54
MEAN=
17.07±3.94
6
1
6
5.88.1017
1
7
7.18.102
1
5.14.1014
MEAN=
0.34±2.23
1
34.41
MEAN=
46.23±24.85
7
1
1
4

Journal Pre-proof
Table 3 (Continued)
Complex
FOW
KAS
CR
Ea
A
Ea
A
E
A
-
1
(min-1) (kJ.mol-1)
(min-1)
(kJ.mol-1)
(min-1)
(
kJ.mol )
g(α)=0.2
37.25
g(α)=0.4
39.95
g(α)=0.5
63.09
g(α)=0.6
88.41
g(α)=0.8
56.21
g(α)=0.2
3.65.1020 231.62
g(α)=0.4
Ɵ=5
--
[
Ag(dmpp)(NO )]
3
2
1.72.1012
1st thermal
decomposition
1449.09
Ɵ=10
1.65.1028
1.01.1054
6.45.1081
1.31.1043
2
1.07.1021 222.83
4
1
3
.45.1011 299.85
g(α)=0.5
Ɵ=15
.61.1023 573.29
Ɵ= 20
2
20.33
g(α)=0.6
16.63
g(α)=0.8
06.85
MEAN=
19.55±9.04
2
1.61.1021
3.67.1025
1.35.1021
2
2
.67.1025 871.73
Ɵ= 25
2
2
1.35.1021 462.46
2
MEAN=
MEAN=
56.98±17.11
7
31.28±452.54
2
g(α)=0.2
26.21
g(α)=0.4
40.17
g(α)=0.5
30.76
g(α)=0.6
25.26
g(α)=0.8
24.02
g(α)=0.2
Ɵ=5
3.84.1046
--
[
Ag(dmpp)(NO )]
3
2
1.19.1019 173.09
2.59.106
2nd thermal
decomposition
483.40
Ɵ=10
g(α)=0.4
2
3.84.1020 175.55
7
1
2
.98.106 1215.55
Ɵ=15
g(α)=0.5
--
1
78.04
g(α)=0.6
80.59
g(α)=0.8
84.09
MEAN=
78.22±4.29
2
6.56.1019
2.36.1019
2.22.1019
.60.107 1055.49
Ɵ= 20
3.46.1054
8.13.1073
1
2
.59.107 593.31
Ɵ= 25
1
2
7.69.107 882.13
1
MEAN=
MEAN=
29.28±6.63
8
45.97±305.55
2
1
5

Journal Pre-proof
Table 3 (Continued)
Complex
FOW
KAS
CR
Ea
A
Ea
A
E
A
(min-1)
(kJ.mol-1)
(min-1)
(
1)
kJ.mol- (min- (kJ.mol-1)
1)
g(α)=0.2
Ɵ=1
Not
meaningful
[
Ag(dmpp)(ClO )].MeOH
4
2
36.04
g(α)=0.4
98.43
g(α)=0.5
70.52
g(α)=0.6
34.98
g(α)=0.8
99.23
MEAN=
07.84±64.29
.40.106
2
3
2
2
1689.17
Ɵ=5
1.31.1030
1
.42.106 366.48
Ɵ=10
1
2
.05.1014
.03.104 182.40
MEAN=
1
.7.101
746.02±671.22
2
2.39.1015
2
1
6

Table 4 The calculated thermodynamic parameters for the thermal decomposition reactions of the synthesized complexes
Complex
Methods
FOW
ΔH /
KAS
ΔH /
CR
ΔS
ΔG
ΔS
ΔG
ΔH /
ΔS
ΔG
kJ.mol-1
J.mol .K
-1
-1
kJ.mol-1
kJ.mol-1
J.mol .K
-1
-1
kJ.mol-1
kJ.mol-1
J.mol .K
-1
-1
kJ.mol-1
Complex I
74.52
-129.01
139.41
121.25
-196.28
225.19
150.42
34.94
132.84
[
Ag(pp)(NO )]
3
Complex II
Ag(dmpp)(NO )]
261.17
155.66
129.10
--
172.44
224.29
194.00
-112.39
-169.04
113.70
736.02
289.95
--
570.75
[
3
First reaction
Complex II
234.02
--
160.04
--
182.95
213.30
247.01
324.36
850.71
751.48
--
[
Ag(dmpp)(NO )]
3
second reaction
Complex VI
286.98
562.92
[
Ag(dmpp)(ClO )]
4
1
7

Journal Pre-proof
Theoretical calculations were adopted to support the explanations to the thermogravimetric
results, bearing on the bonding character and ligand strength. Primarily, the chemical structures
of the complexes were determined. The complexes I, IV and VI were obtained in single crystal
forms appropriate for the X-Ray diffraction analysis. Note that the structure of complex II,
which was determined by X-Ray diffraction methods, has already been reported [26].
Unfortunately, it was not possible to use X-Ray diffraction on complexes III and V. Even so,
provided that these two are analogous with the other complexes, their molecular optimizations
were carried out by feeding initial structures in resemblance to the structures of complexes II,
IV and VI. The conditions of X-Ray diffraction data collection and analyzed crystal parameters
were given in Table 5, whereas the essential bond angles and bond lengths were given in Table
6
. Table 6 also provides theoretically calculated bond lengths and bond angles for comparison.
The Pluton drawings of molecular models of complexes I, IV and VI can be seen in figure 3a,
b and 3c, respectively.
3
The three complexes were found to be di-nuclear as can be seen in Figure 3a-c. Complex II,
whose structure had already been revealed in another study [26], is also di-nuclear. In
complexes II, IV and VI, the coordination spheres around Ag(I) ions are in the form N O but
3
complex I has different coordination spheres. Two donor nitrogens from each ligand coordinate
one of the Ag(I) ions in complex I forming a N coordination sphere; the other Ag(I) is in a
4
N O sphere formed by one nitrogen atom from each ligand and two oxygens of the nitrate
2
2
group. The two Ag(I) ions in complexes II, IV, VI have the same coordination spheres formed
by two nitrogens from one of the ligands and a third nitrogen from the other ligand in addition
to an oxygen atom of the nitrate group. In all four complexes, coordination spheres of both
Ag(I) ions are in the shape of radically distorted tetrahedra.
Figure 3a Pluton drawing of complex I, [Ag(pp)(NO )]
3
1
8

Journal Pre-proof
Figure 3b Pluton drawing of complex IV, [Ag(dmpp)(ClO )]
3
Figure 3c Pluton drawing of complex VI, [Ag(dmpp)(ClO )]
4
1
9

Journal Pre-proof
In X-Ray diffraction studies, Dobson parameters have been used to numerically depict how
close the coordination of a complex is to ideal tetrahedral coordination for a long time [51].
These are three values, Ѳ , Ѳ , Ѳ , calculated from the 6 angles around the central atom.
x
y
z
They are 90° in an ideal tetrahedron. The level of distortion increases as they get farther from
9
0°. The Dobson parameters for the complexes investigated in this study were found as follows:




In complex I around Ag1 ion:  =152.37°,  =72.58°,  =97.63°;
x
y
z
In complex I around Ag2 ion:  =56.06°,  =112.28°,  =95.35°
x
y
z
In complex IV, around both Ag ions:  =38.72°,  =115.08°,  =86.11°,
x
y
z
In complex VI, around both Ag ions:  = 50.21°,  =114.19°,  =48.85°
x
y
z
Ag1 refers to one of the Ag ions in complex 1 where Ag2 refers to the other one since the
coordination around these atoms are different. They can be seen in the Pluton drawing.
These values make it clear that these structures are highly distorted tetrahedra.
The results indicate that the differences between the coordination bond lenghts among the three
complexes are not much. The central atom is located approximately 2.2 Å far from nitrogen
donors of pyrazole ring, 2.5 Å from the nitrogen donors of pyridine ring and 2.6 Å from the
oxygen donors of pyridine ring. The greatest difference in bond lengths is seen in complex I
oxygen donors and Ag2 center; 2.607 Å which is 2.649 and 2.671 Å in the other complexes.
This was not deemed a significant difference in the coordination spheres.
In figure 4, the HOMO and LUMO energy levels of the complexes were shown. These values
have been theoretically calculated. The difference between the LUMO and the HOMO as well
as the fragmental contributions from individual atoms can be seen in numbers in table 7. The
difference is distincly lower in complex I compared to the other two. The HOMO-LUMO gap
is also known to be in relation with the thermal stability of the material [52]. Thermally stable
materials have larger energy differences. Although the lower difference of complex I could
explain the low decomposition temperature; this parameter falls short in explaining the high
-
-
stability of ClO complexes. The energy gap is larger in ClO complexes leading to an
4
3
-
expectation of higher decomposition temperatures than the ones observed in ClO complexes.
4
The experimental results oppose such an implication. Nevertheless, the differences are not as
notable as they are in the case of complex I.
In addition, the level of occupancy in the d orbitals of Ag atoms is calculated by using natural
bond orbital (NBO) algorithm. The findings were given in Table 8. As is seen, almost all the d
orbitals were found to be fully occupied. These findings do not imply any correspondences
between the thermal properties of the complexes and the HOMO-LUMO fragmental
distributions or the d orbital occupancy levels. On the other hand, table 8 also contains the
-
computationally calculated dipole moments. The dipole moments of ClO complexes are
4
apparently greater than the others excluding complex I which differs in the sense that it is not
symmetrical. In complex I, there are two different coordination spheres around the two Ag
-
centers and two NO groups are located at the same side, naturally generating a completely
3
different electronic distribution than the ones other complexes have. Figure 5 shows the electron
density distributions around the complexes. The divergence of Complex I from the others can
be seen at a glance. The greatness of dipole moment indicates high ionic character. For this
2
0

Journal Pre-proof
-
reason, being more ionic in character, ClO complexes decompose at higher temperatures;
4
whereas the decomposition temperature of complex I is lower because it has a smaller HOMO-
LUMO gap. The semi-empirical, thermo-kinetic analysis results given in table 2, where the
activation energy in complex I was found to be noticeably low, confirms this explanation.
Oxygen balance rules are known to be useful in predicting the products of explosion reactions
o
according to the parameter Ω [53]. In Table 9, the standard formation enthalpies (Δ H ), Ω
f
values, and the theoretical heats of the rapid thermal decomposition reactions (Q) calculated
considering these Ω values were given along with the pressure and rate of thermal
decompositions calculated by predicting the gaseous products according to the oxygen balance
rule set. Note that the theoretical enthalpy of thermal decomposition values are far greater than
the experimental results given in table 2. In addition, the Ω values are rather negative. It is very
likely that the reaction products could be highly different than the predictions in case of such
negative Ω values. Although proven useful for explosives that contain nitro groups, such an
outcome brings the practicality of oxygen balance rules into question for new generation,
nitrogen rich high energy materials. There are studies in the literature in support of such
explanation, suggesting that the intra-molecular and intermolecular interactions might have
significant impact on the reaction products as the findings of this study also implies [54].
Conclusion
The thought process of molecular design in high energy material research gains greater
importance as the need for environmentally friendly compounds is inevitably rising. In parallel,
the trend of modern research is leading to the manufacturing of nitrogen rich compounds which
generally cause less damage to the environment than their conventional counterparts do.
With this purpose in mind, 6 silver complexes were synthesized from two different nitrogen
rich ligands pp and dmpp. The thermal decomposition behavior of all complexes was analysed
by a combination of experimental and theoretical means. The structure of [Ag(dmpp)(NO )]
3
has already been reported in the literature. In addition to that, the crystal structures of
[
Ag(pp)(NO )].H O, [Ag(dmpp)(ClO )] and [Ag(dmpp).(ClO )].MeOH were revealed by XRD
3 2 3 4
methods in the scope of this study. Unfortunately [Ag(pp)(ClO )] and [Ag(pp)(ClO )].MeOH
3
4
did not yield suitable crystals for XRD analysis. The findings indicate that the synthesized
complexes demonstrated explosive thermal behavior. All complexes decompose at certain
temperatures with fast, exothermic reactions causing high mass loss values. The differences in
their thermal behavior were interpreted by the analysis of the combined knowledge of chemical
structure, HOMO – LUMO energy gap, dipole moment and thermo-kinetic parameters.
As addressed by the results of this study and the others in the literature alike, further research
about nitrogen rich compounds is crucial in better understanding the reaction mechanisms and
the effects of different chemistries of such compounds to their energetic behavior. To this end,
the results of this study could be helpful in design of new compounds, in coming up with
explanations for variances in thermal behavior, all in addition to the fact that the synthesized
materials could potentially find their way in the industrial applications in the future.
2
1

Figure 4 The graphical representation of calculated molecular orbital energy levels and the computer rendered HOMO-LUMO images of the complexes
2
2

Journal Pre-proof
Table 5 Data collection conditions and crystal data
Parameter
Complex
Complex I
Complex IV
Complex VI
[
Ag(pp)(NO )].H O [Ag(dmpp)(ClO )] [Ag(dmpp)(ClO )].MeOH
3
2
3
4
formula weight /g mol-1
398.88
458.64
506.334
T/K
300 (2)
White
293 (2)
293 (2)
White
crystal color
crystal system
space group
a /Å
White
monoclinic
C2/c
monoclinic
I2/a
monoclinic
I2/a
12.3454(4)
10.5031(4)
20.7798(6)
90.645
18.3876(6)
12.3435(3)
16.8153(5)
110.475(3)
3575.42(17)
32
18.3622(6)
12.2201(2)
16.8857(4)
106.561(3)
3631.77(15)
8
b /Å
c /Å
Beta / °
V /Å3
2694.24(16)
4
Z
Calc. density /g cm-3
µ /mm-1
1.958
1.704
1.726
1.526
1.301
1.288
F (000)
1568
1840
1904
Radiation wavelength / Å
ϴ range / 
index ranges
0.71073
2.55 – 26.37
-12≤h≤15
0.71073
3.30 – 25.05
-20≤h≤21
-11≤k≤14
-20≤l≤14
6484
0.71073
3.35 – 26.05
-21≤h≤22
-14≤k≤14
-20≤l≤20
6812
-13≤k≤13
-25≤l≤24
reflections collected
reflections unique
R1, wR2 (2ó)
9321
2711
3150
2931
0.0297, 0.0867
0.0367, 0.0924
2711/201
0.0374, 0.1108
0.0437, 0.1153
3150/230
0.0294, 0.0696
0.0376, 0.0754
2931/239
1.052
R1, wR2 (all)
data / parameters
GOOF of F2
1.055
1.054
largest difference peak hole
0.550 and -0.781
1.566 and -0.550
0.315 and -0.395
-3
/
e Å
CCDC No
889085
1943842
1943843
2
3

Journal Pre-proof
Table 6 Selected bond lengths and angles around the coordination spheres obtained using X-
Ray diffraction and theoretical calculations
Bond length, Å
X-ray
Bond angle, °
X-ray
Complex
Atoms
DFT
Atoms
DFT
N1-N2
1.360(4)
2.200(3)
2.490(3)
1.362(4)
2.246(3)
1.211(5)
1.211(6)
1.238(4)
3.0206(6)
2.246(3)
2.607(3)
1.361
2.527
2.537
1.362
3.406
1.237
1.264
1.274
4.127
3.406
2.345
N5-Ag2-N5a
O2-N6-O1
O2-N6-O3
160.12(11)
119.2(5)
121.7(5)
119.1(4)
170.29(12)
70.71(9)
133.40(10)
94.86(8)
66.69(6)
71.69
N1-Ag1
N3-Ag1
N4-N5
N5-Ag2
N6-O2
N6-O1
N6-O3
Ag1-Ag2
Ag2-N5
Ag2-O3
121.95
119.98
118.07
108.07
65.53
150.30
118.33
82.94
O1-N6-O3
N1-Ag1-N1a
N1-Ag1-N3
N3-Ag1-N3a
N1-Ag1-Ag2
N3-Ag1-Ag2
N5-Ag2-Ag1
3 2
[Ag(pp)(NO )]
80.05(8)
71.69
Ag1-N1
Ag1-N5
Ag1-N3
Ag1-Ag2
N2-N1
2.207(3)
2.269(3)
2.502(3)
3.1776(6)
1.377(4)
1.365(4)
2.649(3)
2.390
2.420
2.911
5.903
1.366
1.374
2.538
N1 - Ag1 - N5
N1 - Ag1 - N3
N5 - Ag1 - N3
N1 - Ag1 - Ag2 76.14(8)
N5 - Ag1 - Ag2 96.23(8)
N3 - Ag1 - Ag2 63.23(6)
O2 - Cl1 - O1
O2 - Cl1 - O3
O1 - Cl1 - O3
N5-Ag1-N1
N5-Ag1-N3
N1-Ag1-N3
N5-Ag1-Ag2
N1-Ag1-Ag2
N3-Ag1-Ag2
O4-Cl1-O3
140.71(12)
134.30(11)
67.36(10)
110.97
96.26
62.78
59.33
54.64
[
Ag(dmpp)(ClO
3
)]
2
N5-N4
O1-Ag1
59.33
111.0(6)
108.6(4)
104.1(3)
143.54(9)
135.68(8)
68.38(7)
79.55(7)
97.31(6)
62.96(5)
108.6(2)
111.4(3)
108.97
108.61
103.68
144.92
136.43
66.03
81.49
92.83
63.34
110.78
111.34
Ag1-N5
Ag1-N1
Ag1-N3
Ag1-Ag2
N1-N2
2.177(2)
2.228(2)
2.500(2)
3.0758(5)
1.372(3)
1.373(3)
2.671(2)
2.294
2.337
2.719
3.275
1.357
1.364
2.555
[Ag(dmpp)(ClO
4
)]
2
N4-N5
O1-Ag1
O4-Cl1-O2
2
4

Journal Pre-proof
Table 7 The energy levels of HOMO and LUMO, difference between the two and the
fragmental atomic distribution in these orbitals.
Complex
EHOMO
eV
,
ELUMO
eV
,
ΔELUMO-
HOMO
Fragmental
Contributions, % Contributions, %
LUMO
Fragmental
HOMO,
eV
[
[
[
[
[
[
Ag(pp)(NO )]
-5.920
-1.878 4.042
-1.743 4.320
-2.100 4.676
-1.738 4.785
-1.914 4.557
-2.144 4.587
O 76, Ag 23
CH 71, N 27, Ag
, O: 1
O 78, Ag 18, CH CH 72, N 25, Ag
, N 1 2,
O 73, Ag 20, N 3, CH 71, N 26, Ag
CH 3, Cl 1
O 51, Ag 31, N 9, CH 69, N 25, Ag
CH 8, Cl 1
O 79, Ag 16, N 3, CH 70, N 27, Ag
3
2
Ag(dmpp)(NO )] -6.063
3
3
Ag(pp)(ClO )]
-6.776
3
2
Ag(dmpp)(ClO )] -6.523
3
5
Ag(pp)(ClO )]
-6.471
4
CH: 1
2
Ag(dmpp)(ClO )] -6.731
O 58, Ag 24,
CH10, N 7
CH 37, N 25, Ag
2
4
Table 8 Dipole moments of the complexes and d orbital occupation levels of Ag atoms
calculated via NBO algorithm
[
Ag(pp)(NO
3
)]
2
[Ag(pp)(ClO
II
3
)]
2
[Ag(pp)(ClO
III
4
)]
2
[Ag(dmpp)(NO
IV
3
)]
2
[Ag(dmpp)(ClO
3
)]
2
[Ag(dmpp)(ClO
4 2
)]
I
V
VI
μ
1
2.381
0.012
12.084
0.006
1.146
7.774
(Debye)
Ag1
Ag2
dxy
dzx
dyz
dz2
1.9876
1.9887
1.9897
1.9834
1.9885
1.9922
1.9766
1.9856
1.9827
1.9962
1.9849
1.9888
1.9882
1.9920
1.9877
1.9857
1.9826
1.9806
1.9920
1.9791
1.9864
1.9902
1.9799
1.9883
1.9914
1.9875
1.9881
1.9865
1.9903
1.9876
1.9828
1.9822
1.9799
1.9824
1.9898
2
2
dx -y
2
5

Journal Pre-proof
Figure 5 Computer rendered images of electrostatic potential on the molecular surface of the
complexes
2
6

Journal Pre-proof
Table 9. Oxygen balance parameters
Complex H298
a.u.a)
fH298 (g,M) %
Q
(kJ.mol-1)
(kJ.g-1)
3955.14
3300.34
4445.5
4090.28
5072.68
4372.28
(-)
(
[
[
[
[
[
[
Ag(pp)(NO )]
-2248.369180
1563.57b
1434.82b
2128.08b
2031.00b
2311.63b
2217.30b
716.68c
217.99c
472.68c
249.18c
121.30c
284.90c
-102.86
3
Ag(dmpp)(NO )] -2562.705211
-133.57
-97.38
-127.33
-89.84
-119.67
(-)
3
Ag(pp)(ClO )]
-2248.369180
3
Ag(dmpp)(ClO )] -3373.313980
3
Ag(pp)(ClO )]
-3209.231282
4
Ag(dmpp)(ClO )] -3523.554081
4
C
H
-37.84628
-0.500273
(-)
(-)
N
-54.5844894
-75.0606231
-460.136242
-145.758686
(-)
(-)
O
(-)
(-)
Cl
Ag
(-)
(-)
(-)
(-)
a
DFT/B3LYP/LanL2DZ:6-31G(d)
Atomization method
NIST Database [47]
b
c
(-) Not applicable
2
7

Journal Pre-proof
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