Thermogravimetric and kinetic study of new bis(iminophosphorane)ethane solvates

Article abstract of DOI:10.1007/s10973-020-09628-5

Thermal and crystallographic characterization of one solvent-free bis(iminophosphorane)ethane (BIPE) form and three solvates with acetonitrile (ACN), dimethyl sulfoxide (DMSO) and toluene is presented. Thermal behaviors of new compounds indicate that the

Full text of DOI:10.1007/s10973-020-09628-5

Journal of Thermal Analysis and Calorimetry
https://doi.org/10.1007/s10973-020-09628-5
Thermogravimetric and kinetic study of new bis(iminophosphorane)
ethane solvates
Manuela E. Crisan1 · Gabriela Vlase2 · Titus Vlase2 · Lilia Croitor1,3 · Gheorghe Ilia1,2 · Paulina N. Bourosh3 ·
Victor Ch. Kravtsov3 · Mihaela F. Petric1
Received: 4 October 2019 / Accepted: 23 March 2020
© Akadémiai Kiadó, Budapest, Hungary 2020
Abstract
Thermal and crystallographic characterization of one solvent-free bis(iminophosphorane)ethane (BIPE) form and three
solvates with acetonitrile (ACN), dimethyl sulfoxide (DMSO) and toluene is presented. Thermal behaviors of new com-
pounds indicate that the solvent is removed diferently from the BIPE structure, accordingly with the stoichiometric solvent
molecule amount incorporated. Thus, the solvent-free BIPE reveals high thermal stability up to 315 °C, while BIPE solvates
have a similar pattern behavior with low stability about 130 °C. The kinetic parameters of the thermal decomposition process
were determined by three diferent methods Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and nonparametric kinetic.
Crystallographic data revealed that the solvent plays the role of space fller without strong interactions with host molecules.
Guest-free BIPE, BIPE0.5ACN and BIPE0.35DMSO crystallized in monoclinic C2/c (№15) space group, while BIPETOLUENE in a
triclinic P-1 (№2) one. Crystallographic and thermogravimetric data show a good correlation between molecular structures
and activation energies.
Keywords Bis(iminophosphorane)ethane · Solvates · Single crystal X-ray difraction · Thermal stability · Non-isothermal
kinetics
Introduction
[4, 5] and as space fllers between solute molecules, with no
strong interactions between the solvent and solute molecules
[6]. The last ones may be often non-stoichiometric solvates
with the partial occupancy of their solvent molecules posi-
tions in the crystal where solvent molecules decrease the
total void spaces and improve the packing [7].
Numerous studies suggest an increasing number of new
solvates demonstrating their signifcant role in organic syn-
thesis, crystal engineering and pharmaceutical drug develop-
ment [1–3]. Depending on the stoichiometric/non-stoichi-
ometric amounts, the solvent molecules can have diferent
structural functions in organic compounds, for example as
participants in strong intermolecular interactions with the
host molecules, leading usually to stoichiometric solvates
In this context, it is very interesting to study the cases
of diferent solvent molecules incorporation in the same
host structure which give the isostructural solvates. They
allow establishing the identical packing motifs of the host
molecule with common sites of solvent positions [8]. The
relation between molecular shapes of the guest molecule,
solvent-host interactions, and formation of isostructural
solvates were ascertained [9, 10]. However, a number of
publications which highlight this phenomenon is very lim-
ited and it requires more attention. Over the last years, clas-
sifcation of solvents which form solvates has changed and
the tendency to use toluene instead of benzene increases due
to its lower toxicity, besides other top popular solvents such
as acetonitrile (ACN), dimethylformamide (DMF), dimethyl
sulfoxide (DMSO) and dioxane [11, 12].
* Titus Vlase
titus.vlase@e-uvt.ro
* Mihaela F. Petric
mihaelapetric@yahoo.com
1
“Coriolan Dragulescu” Institute of Chemistry, 24 Mihai
Viteazul Boulevard, 300223 Timisoara, Romania
2
Research Center: Thermal Analysis in Environmental
Problems, West University of Timisoara, Pestalozzi Street 16,
300115 Timisoara, Romania
3
Institute of Applied Physics, 5 Academiei Street,
2028 Chişinău, Republic of Moldova
Vol.:(0123456789)
1 3

M. E. Crisan et al.
Thermogravimetry and single-crystal X-ray difraction
are valuable analyses for studying and understanding the
solvates formation and their stability. Herein, we present
the crystal structures and thermal kinetic behavior of new
bis(iminophosphorane)ethanes (BIPE), one solvent-free
form and three solvates with ACN, DMSO and toluene
(Scheme 1). Despite the versatility of BIPE to act as
valuable building blocks in organic, organometallic and
coordination synthesis of biologically active compounds
[13–15], only two organic crystal structures with ethane
spacer between iminophosphorane fragments are currently
known [16–18]. Nature and inclusion mode of diferent
solvent molecules within the framework formed by the
host were investigated comparatively. Combination of
thermogravimetric analysis, diferential thermal analysis
and single-crystal X-ray difraction were used.
Synthesis of compounds BIPE, BIPE0.5ACN
and BIPE0.35DMSO
Bisiminophosphoranes BIPE, BIPE0.5ACN and BIPE0.35DMSO
were synthesized according to Staudinger method [16,
19, 20] in DMF (BIPE), ACN (BIPE0.5ACN) and DMSO
(BIPE0.35DMSO) at room temperature. Colorless crystals were
precipitated after a few days and were purifed by recrystal-
lization in the appropriate solvents.
X‑ray crystallography
Difraction measurements for compounds BIPE, BIPE0.5ACN
and BIPE0.35DMSO were carried out at room temperature on
an Xcalibur E difractometer equipped with CCD area detec-
tor and a graphite monochromator utilizing MoKα radia-
tion. Final unit cell dimensions were obtained and refned
on an entire data set. All calculations to solve the structures
and to refne the proposed models were carried out with
the SHELXL2014 program package [21]. All non-hydrogen
atoms were refned anisotropically. Hydrogen atoms attached
to carbon and nitrogen atoms were positioned geometrically
and treated as riding atoms. In BIPE0.35DMSO crystallization,
DMSO molecule is disordered over two positions (71/29%
occupation). The disordered DMSO molecule has been
well treated by restraining it to have the SAME geometric
parameters as the well-determined ordered DMSO molecule
and was refned isotropically. The X-ray data and the details
of the refnement for both compounds are summarized in
Table 1. Figure 1 was produced using the Mercury program
[22]. The solvent accessible voids (SAVs) were calculated
using PLATON [23]. Crystallographic data of the new com-
pounds reported herein were deposited with the Cambridge
Crystallographic Data Centre and allocated the deposition
numbers CCDC 1956713–1956715.
Experimental
Materials and physical measurements
All used reagents (diphenylphosphoryl azide and
1,2-bis(diphenylphosphino)ethane) and solvents (DMF,
ACN, DMSO and toluene) were acquired from commer-
cial sources in analytical purity and were used without
further purifcation.
Thermal behavior was determined using a Diamond
Thermobalance TG/DTA PerkinElmer in a dynamic
air atmosphere (synthetic air 5.0 Linde Gas with fow
100 mL min−1). The experiments were carried out from
25 °C up to 500 °C, at heating rates β = 7, 10, 12, 15 and
20 °C min−1, and masses around 8 mg of samples were
weighted in open aluminum crucibles.
Results and discussions
Bis(iminophosphorane)ethanes BIPE, BIPE0.5ACN and
BIPE0.35DMSO crystallize in the centrosymmetric monoclinic
space group C2/c (№15) and are isostructural (Table 1), in
contrast to toluene solvate (BIPETOLUENE) which crystal-
lizes in a triclinic P −1 (№2) space group [16]. All struc-
tures adopt almost the same packing arrangements, with
solvent molecules incorporated in the crystal lattice via
weak hydrogen-bond interactions. In the BIPE0.5ACN and
BIPE0.35DMSO compounds, solvent molecules are involved
in the C–H⋯N(O) intermolecular interactions with host
molecule, C31⋯N1A=3.658 Å, C16⋯O1S=3.353 Å and
C37⋯O1S = 3.566 Å (Fig. 1a). In BIPETOLUENE solvent,
Scheme 1 The preparation of BIPE compounds in diferent solvents
1 3

Thermogravimetric and kinetic study of new bis(iminophosphorane)ethane solvates
Table 1 Crystallographic data and structure refnement details for compounds BIPE, BIPE0.5ACN and BIPE0.35DMSO
BIPE
BIPE0.5ACN
BIPE0.35DMSO
Empirical formula
Formula mass
Temperature/K
Wavelength/Å
Crystal system
Space group
Z
C50H46N2O6P4
894.77
293(2)
0.71073
Monoclinic
C2/c
C51H44N2.50O6P4
911.76
293(2)
0.71073
Monoclinic
C2/c
C50.70H46.10N2O6.35P4S0.35
920.09
293(2)
0.71073
Monoclinic
C2/c
8
8
8
a/Å
b/Å
c/Å
41.006(4)
11.1370(8)
20.9175(12)
110.110(6)
8970.3(12)
1.325
41.180(3)
11.2006(5)
21.0745(10)
111.007(5)
9074.4(9)
1.335
41.2529(15)
11.1604(3)
21.1627(7)
110.680(3)
9115.5(5)
1.341
β/°
V/Å3
Dc/g cm−3
μ/mm−1
0.221
0.220
0.236
F(000)
3744
3804
3846
Crystal size/mm3
Refections collected/unique
Refections with [I>2σ(I)]
Data/restraints/parameters
GOF on F2
0.60×0.25×0.20
14,256/7843 (R(int)=0.0366)
4690
7843/0/559
1.001
0.30×0.20×0.17
15,002/7960 (R(int)=0.0499)
4107
7960/0/565
0.979
0.38×0.36×0.20
27,869/8079 (R(int)=0.0491)
4977
8079/6/615
1.007
R1, wR2 [I>2σ(I)]
R1, wR2 (all data)
0.0566, 0.1161
0.1106, 0.1355
0.0678, 0.1276
0.1460, 0.1539
0.0534, 0.1091
0.0983, 0.1276
toluene molecule are accumulated in the crystal lattice
via C‒H···π interactions, with carbon atom…phenyl ring
centroid distance equal with 3.189 Å (Fig. 1b). The struc-
ture of guest-free iminophosphorane BIPE contains neg-
ligible 322.4 Å3 solvent accessible voids (SAVs), which
corresponds to about 3.6% of unit cell volume [23]. No
SAVs were found in solvate structures BIPE0.5ACN and
BIPE0.35DMSO. The calculated volumes occupied by these
solvent molecules in discussed compounds are represented
in Table 2.
decomposition processes take place, both exotherms being
difcult to separate on the thermoanalytical curves.
BIPE0.5ACN has a melting point at 137.6 0.3 °C. The
mass loss step in the range 120–150 °C is difcult to
observe, given that the amount of solvent bound inside
the structure (0.5 mol ACN) is very small. The decom-
position process according to the HF curve takes place at
slightly higher temperatures than in other solvates, which
indicates higher stability of the sample in the presence of
this solvent. The mass loss, in this case, is about 67% of
the sample mass in the temperature range 339–440 °C.
In the case of BIPE0.35DMSO, the thermoanalytical
curves obtained at 10 °C min−1 in the thermal range
30–500 °C highlight two processes of decomposition: the
frst in the interval 111.6–143.1 °C with a mass loss of
2.29% of the sample mass, which can be accounted by
the loss of the DMSO solvent bound by weak hydrogen
bonds within the basic structure of compound BIPE. The
HF curve shows the endothermic process of melting the
sample with a maximum at 134.7 0.2 °C. The TG curve
shows the presence of a decomposition process with a loss
of 67% of the sample mass in the range 338.03–437.9 °C.
The decomposition process is similar to that observed in
the guest-free BIPE, except that the decomposition occurs
at higher temperatures by about 20 °C.
Thermal analysis
Thermogravimetry (TG) and derived thermogravimetry
(DTG) were performed in the air atmosphere to analyze
the thermal behavior of the studied sample. The result is
shown in Fig. 2 and proved that the guest-free BIPE is
stable up to 315 °C. Thermoanalytical curves obtained in
the atmosphere of synthetic air at a speed of 10 °C min−1
show one decomposition step for BIPE. On the Heat Flow
(HF) curve, an endothermic process can be observed,
which is attributed to the melting of the compound with
a maximum at 138 °C. The decomposition process high-
lighted in the range 315.6–430.9 °C occurs with a loss of
66.54% of the sample mass. Analyzing the DTG and HF
curves, it is observed that within this interval at least two
1 3

M. E. Crisan et al.
(a)
(b)
Fig. 1 Crystal packing in BIPE, BIPE0.5ACN and BIPE0.35DMSO. The
violet balls show the positions voids (empty or occupied by solvent
molecules) in the structure and manner of solvent molecules inter-
action with surrounding BIPE molecules (a). Crystal packing in
BIPETOLUENE structure illustrates the inclusion of toluene (b)
Table 2 Selected geometrical
and crystal packing parameters
in discussed compounds
Compound
SG
Unit cell volume/Å3
Solvent accessible voids Reference
(SAVs)/Å3%
BIPE
C2/c
C2/c
C2/c
P − 1
8970.3(12)
9074.4(9)
9115.5(5)
1265.57
322.4 (3.6)
394.9 (4.4)a
432.3 (4.7)a
229.8 (18.2)a
Present work
Present work
Present work
[16]
BIPE0.5ACN
BIPE0.35DMSO
BIPETOLUENE
aSAVs calculated upon the removal of the solvent molecules
The thermal analysis carried out in the case of
BIPETOLUENE shows similarities to BIPE0.35DMSO, the
decomposition being done by two stages of loss of mass:
the frst in the range 121.1–147.97 °C with a mass loss of
2% of the sample mass, and the second proceeding in the
range 326.1–428.6 °C with a mass loss of 67% of the sam-
ple mass similar to the previous ones, which shows that the
fnal stage takes place with the same decomposition process.
The melting point of the sample is 136.7 0.3 °C. In the
case of BIPE0.35DMSO and BIPETOLUENE samples, solvent
removal occurs before the samples are melted. This is clearly
observed on the HF curves obtained for the two samples.
In the case of BIPE0.5ACN, solvent removal occurs with the
sample melting.
1 3

Thermogravimetric and kinetic study of new bis(iminophosphorane)ethane solvates
(a)
(b)
0.1156
5.0
4.5
4.0
3.5
13
12
0.1354
5.5
12
10
8
0.0
– 0.1
– 0.2
– 0.3
– 0.4
– 0.5
– 0.6
– 0.7
– 0.8
– 0.9
– 1.0
– 1.106
0.0
– 0.1
– 0.2
– 0.3
– 0.4
– 0.5
– 0.6
– 0.7
– 0.8
– 0.9
– 1.0
– 1.108
5.0
4.5
4.0
3.5
3.0
2.5
2.0
10
8
4.955
4.954
4.953
4.952
4.951
4.950
4.949
4.940
6
6
4
4
4.947
4.9466
137.5138
2
139
140
141
142
2
3.0
2.5
2.0
0
0
– 2
– 4
– 6
– 8
– 10
– 2
– 4
– 6
– 8
1.5
1.1
1.5
1.1
35
100
150
200
250
300
350
400
450
500
100
150
200
250
300
350
400
450
500
Temperature/°C
Temperature/°C
(d)
(c)
2.612
15
14
0.03401
0.00
0.07404
0.0
3.5
13.05
12
2.4
2.2
2.0
1.8
12
10
8
– 0.05
– 0.10
– 0.15
– 0.20
– 0.25
– 0.30
– 0.35
– 0.40
– 0.45
– 0.50
2.5194
10
8
2.515
2.510
2.505
2.500
2.495
2.490
2.485
2.480
2.475
3.0
3.338
3.33
3.32
3.31
– 0.1
– 0.2
– 0.3
– 0.4
– 0.5
– 0.6
3.30
3.29
3.28
3.27
3.26
3.25
3.24
6
2.5
2.0
1.5
6
2.470
2.467
4
119.9
126
130
136
138
4
1.6
1.4
2
94.14100
110
120
130
140
152
2
0
0
1.2
1.0
0.8
– 2
– 4
– 6
– 8
– 2
– 4
– 6
– 8
1.0
0.6
– 0.7
– 0.7677
– 0.5586 0.5646
35
100
150
200
250
300
350
400
450
500
100
150
200
250
300
350
400
450
500
Temperature/°C
Temperature/°C
Fig. 2 Thermoanalytical curves obtained in an air atmosphere with 10 °C min−1 in the temperature range 10–500 °C for guest-free BIPE (a),
BIPE0.5ACN (b), BIPE0.35DMSO (c) and BIPETOLUENE (d) compounds. Inset Zoomed part of the mass loss related to the evaporation of solvents
From the thermogravimetric study performed for the
four compounds, it is observed that the solvent is removed
differently from the BIPE structure. Thus, the use of
DMSO and ACN solvents results in the decomposition of
the corresponding solvents at higher temperatures, while
in the case of BIPE-TOLUENE the solvent loss occurs at
lower temperatures. This can be explained by the size of
the solvent molecule.
Kinetic analysis
In the literature, several methods are presented that lead to
obtaining kinetic parameters for the solid phase reactions
that occur during the decomposition processes.
It is considered that, for an elementary reaction, the
expression of the reaction speed can be illustrated by the
relation (1) and (2):
As the main decomposition process that occurs in all
compounds is similar in mass loss (approximately 67%),
the kinetic study will aim to analyze the first decompo-
sition step to highlight the influence of the solvent on
the thermal behavior of the studied samples. It can be
observed that in all cases the residues obtained from
the heat treatment carried out in the air atmosphere up
to 500 °C represent 25–27% of the mass of the initial
samples.
da∕dt = k(T) × f(a)
(1)
where t is the reaction time, temperature T and α-conversion
degree.
(ꢀ × da∕dT)a = k(T) × f(a)
(2)
where β is the heating rate, (dα/dT) is the direct available
DTG data, and f(α) is the conversion function.
1 3

M. E. Crisan et al.
The data were obtained at several heating speeds, namely:
β=5, 7, 10, 12 and 15 °C min−1. For obtained the kinetic
data, two integral methods were used: Flynn–Wall–Ozawa
(FWO) (Eq. 3) [24, 25] and Kissinger–Akahira–Sunose
[26, 27] (KAS) (Eq. 4), respectively, and the nonparametric
kinetic method (NPK) developed by Sempere et al. [28, 29]
modifed and developed by Vlase et al. [30, 31].
the E data of BIPE0.5ACN and BIPE0.35DMSO compounds is
observed. The average activation energies are much higher
in the case of BIPE0.5ACN, which suggests that the bonds
formed between the basic structure BIPE and the ACN sol-
vent are much stronger, given that the solvent molecule is
smaller and achieves a better organized structure in compari-
son with BIPE0.35DMSO and BIPETOLUENE
.
The Ozawa method uses Eq. 3, being developed by inte-
grating the Arrhenius equation and assumes that neither the
activation energy nor the kinetic model changes in the whole
reaction.
The results of the NPK analysis are presented in Table 4,
which respect the conversion function proposed by Ses-
tak and Berggren [38], as shown in Eq. 5. Regarding the
results of the kinetic study carried out by the NPK method,
a complex decomposition of BIPE0.5ACN composed by
the main process with a mass over 90% (λ= 91.4%) and a
secondary process is observed here compared to the other
compounds. Both processes have deconversion function
dependent on chemical (n≠0) transformations. In the case of
BIPE0.35DMSO and BIPETOLUENE, the kinetic study performed
by the NPK method revealed three overlapping processes.
All main processes have deconversion function dependent on
both physical (m≠0) and chemical (n≠0) transformations.
It is a decomposition followed by melting as seen from the
kinetic study performed by the NPK method (chemical and
physical process).
ln ꢀ = ln A∕[R ⋅ g(ꢁ)]−5.331−1.052 ⋅ E∕R ⋅ T
(3)
ln(ꢀ∕T2) = ln[A ⋅ R∕E⋅ ≤ g(ꢁ)]−E∕R ⋅ T
(4)
Kissinger–Akahira–Sunose uses Eq. 4. The previously
presented methods are “model-free” nothing being asserted
about the conversion dependence of the reaction rate.
Therefore, we decided to use an improved method, named
modifed NPK method. The mathematical explanation of the
method is presented in detail in our previous works [32–37].
Equation (1) is the only assumption made in the develop-
ment of the nonparametric kinetics (NPK) method.
f(ꢀ) = ꢀm(1 − ꢀ)n
(5)
Conclusions
The kinetic parameters obtained with FWO and KAS
methods are centralized in Table 3, and results obtained with
NPK methods in Table 4.
The study provides the synthesis, crystallographic and ther-
mal characterization of guest-free BIPE and its solvates
BIPE0.5ACN, BIPE0.35DMSO and BIPETOLUENE. All new com-
pounds are isostructural (monoclinic C2/c space group) with
similar packing arrangements. The solvent molecules are
incorporated in the crystal lattice of the host molecule by
weak non-covalent interactions and infuence the stability of
the structure. The results of the thermogravimetric analyses
helped us to assess the thermal stability of the BIPE com-
pounds which reveals high values up to 315 °C for guest-free
BIPE and the decrease in the thermal stability to 130–140 °C
in the case of solvates. The mass losses were in agreement
Analyzing the results of the kinetic study performed by
the FWO and KAS methods, a good correlation between
Table 3 Mean activation energy (E/kJ mol−1) determined by the two
diferent kinetic analysis methods
Ea/kJ mol−1
Compound
BIPE0.5ACN
BIPE0.35DMSO
BIPETOLUENE
Ea (FWO)/kJ mol−1
Ea (KAS)/kJ mol−1
424 69
440 73
212 38
216 40
291 39
365 45
Table 4 Kinetic parameters obtained from NPK
Compound
BIPE0.5ACN
Process
λ/%
A/s−1
Ea/kJ mol−1
n
m
Corr. coef Conversion functions
Ea/kJ mol−1
Main
Secondary
91.4 2.1 × 1054 1.7 × 1012 430 21
2/5
5/4
1
0
1
1
1
0
0
0
1
0.988
0.999
0.987
(1 − x)2/5
(1 − x)5/4
(1 − x) × x
x3/2
445 24
8.2 5.2 × 1079 3.0 × 1020
630
54.3 3.5 × 1027 3.4 × 1012 211 13
3
BIPE0.35DMSO Main
Secondary 1 31.1 6.8 × 1031 1.6 × 1016 244 10
Secondary 2 14.6 6.8 × 1031 5.3 × 1024
175
BIPETOLUENE Main
Secondary 1
Secondary 2
216 29
3/2 0.999
7
1
1
1
0.997
0.994
0.992
(1 − x) × x
(1 − x) × x
(1 − x) × x
x3/2
90.8 1.5 × 1039 5.8 × 1021 302 36
293 44
5.7 9.9 × 102 9.6 × 101
3.5 9.9 × 102 5.8 × 101
15
507
5
2
3/2 0.999
1 3

Thermogravimetric and kinetic study of new bis(iminophosphorane)ethane solvates
14. Molina P, Vilaplana MJ. Iminophosphoranes: useful building
with the stoichiometric solvent amount incorporated in
solvates. We can conclude that nature of the solvent dictates
the stability of solvates as follows: toluene<ACN~DMSO.
In addition, the kinetic study provides a more complete pic-
ture of the degradation process of BIPE solvates. The kinetic
parameters were determined by using three diferent meth-
ods FWO, KAS and NPK. The frst two methods provide
average activation energies much higher for BIPE0.5ACN in
comparison with the other studied solvates, correlating with
higher thermal stability. NPK method shows a better under-
standing of the multistep degradation processes, revealing
a deconversion function dependent on both physical and
chemical transformations.
blocks for the preparation of nitrogen-containing heterocycles.
Synthesis. 1994;194:1197–218.
15. Stolzenberg H, Weinberger B, Fehlhammer WP, Puhlhofer FG,
Weiss R. Free and metal-coordinated (N-Isocyanimino)triph-
enylphosphorane: X-ray structures and selected reactions. Eur
J Inorg Chem. 2005;21:4263–71.
16. Staudinger H, Mayer J. Über neue organische Phosphorverbind-
ungen III Phosphinmethylenderivate und Phosphinimine. Helv
Chim Acta. 1919;2:635–46.
17. Weller F, Kang HC, Massa W, Rübenstahl T, Kunkel F,
Dehnicke K. Crystal structures of the Silylated Phosphanimines
Me
3SiNPPh3 und Me3SiNPPh2–C2H4–PPh2NSiMe3. Z Natur-
forsch B J Chem Sci. 2014;50(7):1050–4.
18. Marsh RE. The space groups of point group C3: some correc-
tions, some comments. Acta Cryst B. 2002;58:893–9.
19. Micle A, Miklašova N, Varga RA, Pascariu A, Plesu N, Petric
M, Ilia G. A versatile synthesis of a new bisiminophosphorane.
Tetrahedron Lett. 2009;50:5622–4.
Acknowledgements This work was partially supported by Program 2,
Project 2.1 of the “Coriolan Drăgulescu” Institute of Chemistry and by
Project ANCD 20.80009.5007.15 of the Institute of Applied Physics.
20. Petric MF, Crisan ME, Chimakov YM, Varga RA, Micle A,
Neda I, Ilia G. Structural and ab initio studies on the polymor-
phism of iminophosphorane (CH3C6H4)3P=NP[(=O)(OPh)2]. J
Mol Struct. 2015;1083:389–97.
21. Sheldrick GM. Crystal structure refnement with SHELXL. Acta
Cryst C. 2015;C71:3–8.
References
22. Macrae CF, Edgington PR, McCabe P, Pidcock E, Shields GP,
Taylor R, Towler M, Van de Streek J. Mercury: visualization
and analysis of crystal structures. J Appl Cryst. 2006;39:453–7.
23. Spek AL. Structure validation in chemical crystallography. Acta
Cryst D. 2009;D65:148–55.
1. Healy AM, Worku ZA, Kumar D, Madi AM. Pharmaceutical
solvates, hydrates and amorphous forms: a special emphasis on
cocrystals. Adv Drug Deliv Rev. 2017;117:25–46.
2. Chadha R, Kuhad A, Arora P, Kishor S. Characterisation and
evaluation of pharmaceutical solvates of Atorvastatin calcium
by thermoanalytical and spectroscopic studies. Chem Cent J.
2012;6:114–29.
24. Ozawa T. A new method of analyzing thermogravimetric data.
Bull Chem Soc Jpn. 1965;38:1881–6.
25. Flynn JH, Wall LA. A quick, direct method for the determina-
tion of activation energy from thermogravimetric data. Polym
Lett. 1966;4:323–8.
3. Griesser UJ. The importance of solvates. In: Weinheim HR, editor.
Polymorphism in the Pharmaceutical Industry. Hoboken: Wiley;
2006. p. 211–233.
26. Kissinger HE. Reaction kinetics in diferential thermal analysis.
Anal Chem. 1957;29(11):1702–6.
4. Görbitz CH, Torgersen E. Symmetry, pseudosymmetry and pack-
ing disorder in the alcohol solvates of L-leucyl-L-valine. Acta
Cryst B. 1999;B55:104–13.
27. Akahira T, Sunose T. Joint convention of four electrical insti-
tutes. Research report Chiba institute of technology. Sci Tech-
nol. 1971;16:22–31.
5. Tieger E, Kiss V, Pokol G, Finta Z, Rohlicek J, Skorepova E,
Dusek M. Rationalization of the formation and stability of bosu-
tinib solvated forms. Cryst Eng Commun. 2016;18:9260–74.
6. Vippagunta SR, Brittain HG, Grant DJW. Crystalline solids. Adv
Drug Deliv Rev. 2001;48:3–26.
28. Serra R, Nomen R, Sempere J. The non-parametric kinetics.
A new method for the kinetic study of thermoanalytical data. J
Therm Anal Calorim. 1998;52:933–43.
29. Serra R, Sempere J, Nomen R. A new method for the kinetic
study of thermoanalytical data: the non-parametric kinetics
method. Thermochim Acta. 1998;316:37–45.
7. Barbour LJ. Organic cage crystals: supramolecular joinery. Nat
Chem. 2015;7:97–9.
30. Vlase T, Vlase G, Doca N, Bolcu C. Processing of non-isother-
mal TG data. Comparative kinetic analysis with NPK method.
J Therm Anal Calorim. 2005;80:59–64.
8. Hosokawa T, Datta S, Sheth AR, Brooks NR, Young VG, Grant
DJW. Isostructurality among fve solvates of phenylbutazone.
Cryst Growth Des. 2004;4:1195–201.
31. Vlase T, Vlase G, Birta N, Doca N. Comparative results of
kinetic data obtained with different methods for complex
decomposition step. J Therm Anal Calorim. 2007;88:631–5.
32. Vlase G, Bolcu C, Modra D, Budiul MM, Ledeți I, Albu P,
Vlase T. Thermal behavior of phthalic anhydride-based poly-
esters. J Therm Anal Calorim. 2016;126:287–92.
9. Sarma JARP, Desiraju GR. Polymorphism and pseudopolymor-
phism in organic crystals: A Cambridge Structural Database study.
In: Seddon KR, Zaworotko M, editors. Crystal engineering: design
and application of functional solids. Dordrecht: Kluwer Academic
Publishers; 1999. p. 325–356.
10. Caira MR, Bettinetti G, Sorrenti M. Structural relationships, ther-
mal properties, and physicochemical characterization of anhy-
drous and solvated crystalline forms of tetroxoprim. J Pharm Sci.
2002;91:467–81.
33. Ceban I, Blajovan R, Vlase G, Albu P, Koppandi O, Vlase T.
Thermoanalytical measurements conducted on repaglinide to
estimate the kinetic triplet followed by compatibility studies
between the antidiabetic agent and various excipients. J Therm
Anal Calorim. 2016;126:195–204.
11. Görbitz CH, Hersleth HP. On the inclusion of solvent molecules
in the crystal structures of organic compounds. Acta Cryst B.
2000;B56:526–34.
34. Patrutescu C, Vlase G, Turcus V, Ardelean D, Vlase T, Albu
P. TG/DTG/DTA data used for determining the kinetic param-
eters of the thermal degradation process of an immunosup-
pressive agent: mycophenolate mofetil. J Therm Anal Calorim.
2015;121(3):983–8.
12. Desiraju GR, Sharma CVK. Perspectives in supramolecular chem-
istry: the crystal as supramolecular entity. In: Desiraju GR, editor.
Chichester: Wiley; 1996. p. 31–61.
13. Gololobov YG, Kasukhin LF. Recent advances in the Staudinger
reaction. Tetrahedron. 1992;48:1353–406.
1 3

M. E. Crisan et al.
35. Vlase T, Vlase G, Doca N. Kinetics of thermal decomposition of
alkaline phosphates. J Therm Anal Calorim. 2005;80(1):207–10.
36. Albu P, Doca SC, Anghel A, Vlase G, Vlase T. Thermal
behavior of sodium alendronate. J Therm Anal Calorim.
2017;127(1):571–6.
38. Sestak J, Berggren G. Study of the kinetics of the mechanism
of solid-state reactions at increasing temperatures. Thermochim
Acta. 1971;3:1–12.
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
37. Paul A, Budiul M, Mateescu M, Chiriac V, Vlase G, Vlase T.
Studies regarding the induced thermal degradation, kinetic
analysis and possible interactions with various excipients of an
osseointegration agent-zoledronic acid. J Therm Anal Calorim.
2017;130(1):403–11.
1 3