Crystal structure, phase transition and conductivity study of two new organic – inorganic hybrids: [(CH2)7(NH3)2]X2, X?=?Cl/Br

Article abstract of DOI:10.1016/j.molstruc.2016.07.025

Two hybrids 1,7-heptanediammonium di-halide, [(C₇H₂₀N₂]X₂,X?=?Cl/Br crystallize in monoclinic P2₁/c, Z?=?4. [(C₇H₂₀N₂]Cl₂: a?=?4.7838 (2)??, b?=?16.9879 (8)??, c?=?13.9476 (8)??, β?=?97.773 (2)°, V?=?1203.58(10)??³, D?=?1.137?g/cm³, λ?=?0.71073??, R?=?0.052 for 1055 reflections with I?>?2σ(I), T?=?298(2)?K. [(C₇H₂₀N₂]Br₂: a?=?4.7952 (10)??, b?=?16.9740 (5)??, c?=?13.9281 (5)??, β?=?97.793 (2)°, V?=?1203.83(6)??³, D?=?1.612?g/cm³, λ?=?0.71073??, R?=?0.03 for 1959 reflections with I?>?2σ(I) T?=?298(2)?K. Asymmetric unit cell of [(C₇H₂₀N₂]X₂,X?=?Cl/Br, each consist of one heptane-1,7-diammonium cation and two halide anions. The organic hydrocarbon layers pack in a stacked herring-bone manner, hydrogen bonded to the halide ions. Lattice potential energy is 1568.59?kJ/mol and 1560.78?kJ/mol, and cation molar volumes are 0.295?nm³ and 0.300?nm³ for chloride and bromide respectively. DTA confirmed chain melting transitions for both hybrids below T?～?340?K. Dielectric and ac conductivity measurements (290??340?K. Cross over from Jonscher's universal dielectric response at low temperatures T??340?K is observed. At high temperatures halide ion hopping in accordance with the jump relaxation model prevails.

Full text of DOI:10.1016/j.molstruc.2016.07.025

Journal of Molecular Structure 1127 (2017) 59e73
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Crystal structure, phase transition and conductivity study of two new
organic e inorganic hybrids: [(CH2)7(NH3)2]X2, X ¼ Cl/Br
Mohga Farid Mostafa*, Shimaa Said El-khiyami, Seham Kamal Abd-Elal 1
Physics Department, Faculty of Science, University of Cairo, Giza, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Two hybrids 1,7-heptanediammonium di-halide, [(C7H20N2]X2,X ¼ Cl/Br crystallize in monoclinic P21/c,
Z ¼ 4. [(C7H20N2]Cl2: a ¼ 4.7838 (2) Å, b ¼ 16.9879 (8) Å, c ¼ 13.9476 (8) Å,
b
¼ 97.773 (2)ꢀ,
Received 28 May 2016
Received in revised form
5 July 2016
Accepted 8 July 2016
Available online 25 July 2016
V ¼ 1203.58(10) Å3, D ¼ 1.137 g/cm3,
l
¼ 0.71073 Å, R ¼ 0.052 for 1055 reflections with I > 2
s(I),
T ¼ 298(2) K. [(C7H20N2]Br2: a ¼ 4.7952 (10) Å, b ¼ 16.9740 (5) Å, c ¼ 13.9281 (5) Å,
b
¼ 97.793 (2)ꢀ,
V ¼ 1203.83(6) Å3, D ¼ 1.612 g/cm3,
l
¼ 0.71073 Å, R ¼ 0.03 for 1959 reflections with I > 2
s(I)
T ¼ 298(2) K. Asymmetric unit cell of [(C7H20N2]X2,X ¼ Cl/Br, each consist of one heptane-1,7-
diammonium cation and two halide anions. The organic hydrocarbon layers pack in a stacked herring-
bone manner, hydrogen bonded to the halide ions. Lattice potential energy is 1568.59 kJ/mol and
1560.78 kJ/mol, and cation molar volumes are 0.295 nm3 and 0.300 nm3 for chloride and bromide
respectively. DTA confirmed chain melting transitions for both hybrids below T ~ 340 K. Dielectric and ac
conductivity measurements (290 < T K < 410; 0.080 < f kHz<100) indicated higher conductivity and
activation energy of bromide for T > 340 K. Cross over from Jonscher's universal dielectric response at
low temperatures T < 340 K to super-linear power law for T > 340 K is observed. At high temperatures
halide ion hopping in accordance with the jump relaxation model prevails.
Keywords:
X-ray crystal structure
Phase transition
Dielectric constant
Conductivity
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
Pbam [12]. To the best of our knowledge, no structure analysis or
physical properties concerning n ¼ 7 hybrids were reported. This is
Recently, organic-Inorganic hybrid (OI) materials have attracted
much attention due to their interesting structure, optical and
electrical properties [1]. The class of hybrid materials is very large
showing different structures and properties that promise wide
applications in different fields. Alkylene-diammonium dihalide
hybrids, [(CH2)n(NH3)2]X2; n ¼ 2, …6 and X ¼ Cl/Br show several
interesting structural phase transitions, they mimic lipid bilayer,
being solids they provide an excellent model for the study of
transport in cell membranes [2]. Besides these hybrids are pre-
cursor ligands in transition metal complexes [3] and have
structure-directing properties in the synthesis of a number of
nanoparticles [4,5]. Room temperature crystal structure determi-
nation of the chlorides and bromides where n ¼ 2, 3, 4, 5 and 6
[6e16] crystallize in monoclinic system with space group P21/c
except for bromide with n ¼ 2 (space group C2/m), at 100 K [8] and
the chloride where n ¼ 5 which is orthorhombic with space group
most likely due to difficulty in growing single crystal of anhydrous
1,7 -heptanediammonium hybrids. It is worth noting that for n ¼ 8
and 10 only hydrated hybrids were obtained [17]. In this article we
report synthesis, characterization, single crystal structure analysis,
phase transitions and conductivity study of chloride and bromide
hybrids where
n
¼
7. Differential thermal scanning
580 K) and impedance spectroscopy
(290 <
K
<
T
(290 K < T < 410 K) in the frequency range 100 Hz - 100 kHz were
used to study the phase transitions and electric transport proper-
ties of the two samples 1,7-heptane-diammonium crystals
[(CH2)7(NH3)2]X2, X ¼ Cl/Br, henceforth C7C and C7B.
2. Experimental
Samples were synthesized by adding slight excess 30% HCl/HBr
to 1,7- diaminoheptane. The resulting solution is heated to 70 ꢀC for
1 h. Slow cooling to room temperature yields colorless solids. The
solids were washed with a 1:1 solution of ethanol and methylene
chloride. Samples were re-dissolved in ethanol and re-crystallized
twice. Colorless prismatic and needle crystals were grown from
* Corresponding author.
E-mail address: Mohga40@Yahoo.com (M.F. Mostafa).
Partial fulfillment of Ph.D.
1
http://dx.doi.org/10.1016/j.molstruc.2016.07.025
0022-2860/© 2016 Elsevier B.V. All rights reserved.

60
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Table 1
ethanol solution kept in vacuum desiccator for 6 months, for
chloride and bromide hybrids respectively. Chemical analysis and ir
absorption spectrum (in the range 400 cmꢁ1e4000 cmꢁ1) were
carried out at the micro analysis center at university of Cairo.
The elemental analysis showed the percent of carbon ¼ 39.50%
(40.46%), 29.30% (28.78%) and hydrogen ¼ 10.12% (9.701%), 6.50%
(6.902%) for C7Cl and C7Br respectively; theoretical values are
given in brackets.
X-ray data collection parameters and refinement, of C7C and C7B at 298 K.
a. (C7C)
b. (C7B)
Formula
Mr
Space group
a
B
C
b
V
Z
Dx
l
qmax
C7H20N2Cl2
207.784
Monoclinic P21/c
4.7838 (2)Å
16.9879 (8)Å
14.9476 (8)Å
97.773 (2)ꢀ
1203.58 (10)Å3
4
C7H20N2Br2
292.059
Monoclinic P21/c
4.79520 (10)Å
16.9740 (5)Å
14.9281 (5)Å
97.793 (2)ꢀ
1203.83 (6)Å3
4
The IR spectrum was obtained using FTIR 1650 Perkin Elmer
spectrometer. The IR and the chemical analysis results confirmed
formation of the two samples with chemical formula
[(CH2)7(NH3)2] X2, X ¼ Cl/Br.
1.147 Mg mꢁ3
0.71073
27.48ꢀ
1.612 Mg mꢁ3
0.71073
27.48ꢀ
Differential thermal scanning (DSC) measurements were carried
out on a Shimadzu thermal scanner model DSC-50 at 10 ꢀC/min.
Powdered crystals weighing 2.5 mg were used. Measurements
were performed in a flow of dry nitrogen gas at a rate of 50 ml/min.
The data were calibrated with the melting transition of Indium at
157 ꢀC.
m
0.70 mmꢁ1
2756
6.69 mmꢁ1
5182
Measured reflections
Independent reflections
Observed reflections
Criterion
Rint
3088
1055
I > 3.00 sigma(I)
0.052
2993
1959
I > 3.00 sigma(I)
0.030
X-ray crystallographic data were collected on Enraf-Nonius 590
Kappa CCD single crystal diffractometer with graphite mono-
H
K
L
ꢁ6 /6
ꢁ6 /6
0 / 21
0 / 21
ꢁ19 / 19
ꢁ19 / 19
chromator using MoK
collected at room temperature using 4-
a
(
l
¼ 0.71073 Å). The intensities were
R(all)
R(gt)
wR(ref)
wR(all)
S(ref)
0.185
0.072
u
-scan mode. The cell
0.093
0.266
0.276
2.278
0.041
0.080
0.086
1.613
refinement and data reduction were carried out using Denzo and
Scalepak programs [18]. The crystal structure was solved by the
direct method using SIR92 program [19] which revealed the posi-
tions of all non-hydrogen atoms and refined by the full matrix least
square refinement based on F2 using maXus package [20]. The
temperature factors of all non-hydrogen atoms were refined
anisotropically, then hydrogen atoms were introduced as a riding
model with CeH ¼ 0.96 and refined isotropically. Molecular
graphics were prepared using ORTEP Program [21].
Ac conductivity is measured using computer controlled SR-830
lock-In amplifier. A home built cryostat was used. Temperature
was measured using a copper constantan thermocouple. Well
ground crystallites were pressed in the form of a disc 1.0 cm in
diameter and 1.2 mm thickness under a pressure of 2.4 kPa. The
surfaces were coated with Ag paste to ensure good electrical con-
tacts. The sample chamber was evacuated for 12 h prior to mea-
surements to ensure moisture free atmosphere. Several virgin
samples were measured to ensure reproducibility of results.
D/
smax
0.037
0.016
Drmax
Drmin
wR(gt)
0.98eÅ3
0.96eÅ3
ꢁ1.32eÅ3
0.266
ꢁ0.81eÅ3
0.080
which are hydrogen bonded to the halide anion. Each two parallel
chains are connected to each other forming a couple via halide ion
Cl(2)/Br(2). The nearly perpendicular couples are connected via
Cl(1)/Br(1). Fig. 1c depicts molecular arrangement and hydrogen
bond net-work of C7Cl along a-axis. It reveals the occurrence of four
short NeCl non-bonded contacts, three of these contacts may be
ascribed to charge-assisted hydrogen-bond formation and the
fourth is a short contact directed approximately along the exten-
sion of the CeN bond. Three, H3A, H3B, and H3C, have values
within the range of the hydrogen bond distance 2.393 Å, 2.254 Å
and 2.289 Å respectively.
It is worth mentioning that hydrogen bond length of HeCl1 is
shorter than HeBr1 while the opposite is true where the HeBr2 is
slightly longer than the hydrogen bond attached to HeC12 as listed
in Table 5. The average bond length NeC ¼ 1.511 (Å), CeC ¼ 1.51 (Å),
CeH ¼ 0.960 (Å) are in the acceptable range with previously re-
ported similar hybrids [6e16].
3. Results and discussion
3.1. Crystal structure
The two isomorphous hybrids crystallize in monoclinic P21/c
with 4 molecules/unit cell each. Lattice spacing are a ¼ 4.7838 (2) Å,
4.79520 (10) Å, b ¼ 16.9879 (8) Å, 16.9740 (5) Å, c ¼ 13.9476 (8) Å,
13.9281 (5) Å,
b
¼ 97.773 (2)ꢀ, 97.793(2)ꢀ, V ¼ 1203.58 (10) Å3,
3.2. Lattice potential energy, molecular and cation volume
1203.83 (10) Å3 for chloride and bromide respectively as listed in
Table 1 along with data collection parameters and refinement.
Table 2 lists the fractional atomic coordinates and equivalent
Estimation of lattice potential energy U (pot) for the general
type of the hybrids of MpXq can be obtained using Eq. (1) below
[22]:
isotropic thermal parameters. Table
3 lists the anisotropic
displacement parameters (Å2). The selected bond length and bond
angles and dihedral angles are listed in Table 4. Table 5 lists the
hydrogen bonds geometry of the two samples.
h
i
X
UðpotÞ ¼
where
niz2
a
=V1=3
þ
b
(1)
As can be seen from Table 4, for C7C the chains deviate slightly
from planarity. It is expected that as the temperature increases
conformation changes will take place, which would lead to phase
transitions.
Fig. 1a is an ORTEP view of the atoms where X ¼ Cl/Br and Fig. 1b
shows ORTEP view of molecular arrangement in the unit cell of C7B.
The cation exists in an ideal fully extended conformation in layers
and lies on a mirror plane. The chains extend in a zigzag structure of
seven carbon atoms with two NH3 cations attached at chain ends
a
and b are appropriate fitting coefficients chosen according
to the stoichiometry of the hybrid, ni is the number of ions with a
charge zi in the formula unit, Vm is the molecular volume.
For MX2 (1:2) hybrids, the lattice potential energy is given by
Ref. [22]:
ꢀ
ꢀꢀ
ꢀ
h .
i
ꢀ
ꢀꢀ
ꢀ
UðpotÞ ¼ Zþ Zꢁ y a V1=3
þ
b
(2)
ꢀ
ꢀꢀ
ꢀ

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
61
Table 2
pointed out that for n ¼ 3 and 5 the lattice potential energy Upot
deviates slightly from the observed linear relation. This could be
associated with the difference in crystal symmetry, where
dichloride of n ¼ 3 and 5 are orthorhombic, while all the other
Fractional atomic coordinates and equivalent isotropic thermal parameters (Å2):
Ueq ¼ 1/3SiSj Uij ai ꢂ aj* ai.aj of: (a) C7C and (b) C7B.
X
Y
Z
Ueq
hybrids are monoclinic. The difference
D
Upot ¼ [Upot(C7C)ꢁUpot
a. C7C
Cl1
Cl2
N3
N4
C5
C6
C7
C8
0.1100 (5)
0.9822 (5)
0.358 (3)
0.529 (3)
0.571 (4)
0.380 (4)
0.431 (4)
0.538 (4)
0.356 (4)
0.524 (4)
0.642 (4)
0.633750
0.729751
0.236098
0.295888
0.367134
0.272794
0.676000
0.632610
0.240596
0.237076
0.39416 (13)
0.22301 (17)
0.5791 (9)
0.2302 (11)
0.3835 (12)
0.4180 (11)
0.3297 (15)
0.4646 (13)
0.5023 (14)
0.5443 (12)
0.2870 (14)
0.426830
0.360710
0.447901
0.373801
0.287075
0.353125
0.432048
0.504888
0.541826
0.44708 (17)
0.21276 (18)
0.3931 (11)
ꢁ0.1499 (14)
0.0459 (13)
0.1036 (16)
ꢁ0.0206 (15)
0.1800 (14)
0.2447 (12)
0.3229 (14)
ꢁ0.0769 (16)
0.012540
0.0411 (13)
0.0512 (14)
0.140 (13)
0.153 (14)
0.122 (14)
0.129 (15)
0.145 (17)
0.126 (15)
0.128 (15)
0.128 (14)
0.150 (18)
0.122894
0.122894
0.125190
0.125190
0.135445
0.135445
0.130145
0.130145
0.127421
0.127421
(C7B)] decreases with increasing the chain length, reaching a
minimum for n ¼ 5 as depicted in insert (i). It is to be noted that the
observed minimum is most likely associated with symmetry dif-
ferences of n ¼ 5 hybrid.
Fig. 2b shows the molecular volume (Vm) as a function of
number of carbon atoms/chain. As expected nearly linear increase
of (Vm) as chain length increases.
C9
In addition, since for a hybrid of MpXq [24]:
C10
C11
H5A
H5B
H6A
H6B
H7A
H7B
H8A
H8B
H9A
H9B
b. C7B
Br1
Br2
N3
N4
C5
C6
C7
C8
C9
C10
C11
H5A
H5B
H6A
H6B
H7A
H7B
H8A
H8B
H9A
H9B
Vm ¼ pVþ þ qVꢁ
(4)
0.083230
0.067616
0.129766
0.013565
where Vþ and Vꢁ are the volumes of the cation and anion, p ¼ 1 and
q ¼ 2 for MX2 (1:2) and V(Clꢁ) ¼ 0.0298 nm3 and V(Brꢁ) ¼ 0.0363
[24]. The volume of the cations (Vþ) C7H20N2 of C7C and C7B as
well as (Vþ) for n ¼ 2, … … 6 are also calculated. Fig. 2c shows
variation of the cations volume (Vþ) as a function of number of C
atom/chain (n). The cation volume increases with increasing chain
length. Slight deviation of (Vþ) vs. chain length from linearity for
n ¼ 5 is also observed. It is to be noted that difference between
ꢁ0.057365
0.215253
0.150473
0.211957
0.266317
0.462996
0.89132 (10)
0.01542 (12)
0.6526 (8)
0.4626 (8)
0.6520 (10)
0.6189 (10)
0.4649 (10)
0.4269 (11)
0.3460 (11)
0.4772 (10)
0.5610 (9)
0.768344
0.768993
0.711798
0.756078
0.370261
0.328201
0.353249
0.274329
0.260914
0.10604 (3)
0.27716 (4)
ꢁ0.0734 (2)
0.2704 (2)
ꢁ0.0032 (3)
0.0833 (3)
0.0322 (3)
0.1185 (3)
0.2109 (3)
ꢁ0.0420 (3)
0.1771 (3)
ꢁ0.042840
0.036760
0.05259 (3)
0.28703 (3)
0.1088 (2)
0.6448 (3)
0.2549 (3)
0.3927 (3)
0.3182 (3)
0.4556 (3)
0.5768 (4)
0.1756 (3)
0.5233 (3)
0.287047
0.233807
0.366413
0.429043
0.346840
0.283930
0.489741
0.420061
0.607469
0.536339
0.0446 (2)
0.0567 (3)
0.040 (2)
0.044 (2)
0.041 (2)
0.043 (2)
0.044 (3)
0.046 (3)
0.052 (3)
0.044 (2)
0.041 (2)
0.046964
0.046964
0.047343
0.047343
0.047806
0.047806
0.048644
0.048644
0.056149
0.056149
bromide and chloride molecular volumes [
D
Vm ¼ Vm(C7B)ꢁ
Vm(C7C)] and cation volumes [
D
Vþ ¼ Vþ (C7B)eVþ (C7C)] show
minima for n ¼ 5 hybrid which corresponding to that found for
[DUpot], see in (insert (i) of Fig. 2a.
3.3. Thermal behavior
0.125789
0.051449
Fig. 3 shows the DSC scans of the two hybrids C7C and C7B. Near
room temperatures, asymmetric endothermic peaks at
ꢁ0.008611
TC7C ¼ 334.1 2 K (
S ¼ 13.65 J/mol.K) were observed for C7C and C7B respectively. At
high temperatures endothermic peak located at TC7C ¼ 440.4 K
D
S ¼ 13.07 J/mol.K) and TC7B ¼ 336.1 1 K
0.065589
0.077369
0.145539
0.169391
0.237431
(D
(
D
S ¼ 27.12 J/mol.K) can be associated with change of crystal
0.203944
morphology while exothermic peak at TC7C ¼ 546 K reflects
dissociation. Two consecutive endothermic peaks at TC7B ¼ 529.6 K
(D
S ¼ 25.13 J/mol.K) and TC7B ¼ 541.6 K ( S ¼ 28.13 J/mol.K) are
D
where Zþ and Zꢁ are the respective charges on the cation and anion
of the compound, v is the number of ions per molecule and equals
to (p þ q). For the case of hybrids of formula MX2 with charge ratio
attributed to pre-melting and melting of C7B respectively. Due to
the non-linear behavior of heat flux with increasing temperature in
the range 295 Ke330 K and to the small differences in transition
temperatures of TC7C and TC7B, DTA measurements at a heating rate
of 5 ꢀC/min. were performed and presented in inserts (i) and (ii) of
Fig. 3. The results showed several peaks near room temperature.
Starting from the high temperature side, C7C showed broad
endothermic peak at T0(C7C) ¼ 432 3 K, a prominent transition at
T1(C7C) ¼ 330.5 1 K having a shoulder at T2(C7C) ¼ 321.6 3 K and
an inconspicuous small peak at T3(C7C) ¼ 307.9 K. The bromide
hybrid, C7B, showed two consecutive peaks corresponding to phase
(2:1) Zþ ¼ 2, Zꢁ ¼ 1, p ¼ 1, q ¼ 2,
n
¼ 3,
a
¼ 133.5 kJ molꢁ1 nm,
b
¼ 60.9 kJ molꢁ1, and Vm (nm3) is given by Ref. [23]:
ꢁ
ꢂ
Vm nm3 ¼ Mm=ð
r
NAÞ ¼ 1:66045 ꢂ 10ꢁ3Mm=
r
(3)
where NA is Avogadro's number,
(g/mol) is the molar mass as obtained from reported crystal
r
(g cmꢁ3) is the density and Mm
structure data [6e16]. Values of (Vm) as calculated from Eq. (3) are
V
transformations located at T1(C7B)
T2(C7B) ¼ 302.2 1 K. Previous studies of phospholipids, alkyl-
¼
333.8
2
K
and
m (C7C) ¼ 0.294 nm3 and Vm (C7B) ¼ 0.301 nm3. This yields lattice
energy U (pot) ¼ 1568.59 kJ/mol and 1560.78 kJ/mol for C7C and
C7B respectively. Fig. 2a shows the lattice potential energy Upot as a
function of number of carbon atoms in the chain, along with Upot
for n ¼ 2, 3, …6 as obtained from reported X-ray results (see
Table 6) [6e16]. It indicates nearly linear decrease of lattice po-
tential energy with chain length for C7C and C7B such that Upot of
the chlorides is always higher than that of the bromides. It is to be
noted that Upot of C7B is presented on a secondary axis with
different scale from that of C7C for clear data presentation. It is to be
ammonium and alkylene-diammonium hybrids have attributed
consecutive thermodynamic transitions near ambient to be asso-
ciated with chain melting transitions where major and minor
transitions near ambient have been reported [25e30]. Minor
transition is associated with dynamic two-fold rotational disorder
of the chain and the major transition is attributed to the ‘‘melting’’
of the chain. At the chain melting transition the rapid diffusion of
one or more gauche bonds up and down the hydrocarbon chain
takes place, leading to decrease of the chain length [26].

62
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Table 3
Anisotropic displacement parameters (Å2) of: a) C7C and b) C7B.
U11
U12
U13
U22
U23
U33
a. C7C
Cl1
Cl2
N3
N4
C5
C6
C7
C8
C9
C10
C11
b. C7B
Br1
Br2
N3
N4
C5
C6
C7
0.0406 (13)
0.0472 (15)
0.157 (14)
0.156 (16)
0.107 (14)
0.111 (15)
0.105 (14)
0.116 (14)
0.106 (13)
0.104 (14)
0.137 (17)
0.0007 (11)
ꢁ0.0041 (12)
0.028 (11)
ꢁ0.022 (11)
ꢁ0.021 (12)
ꢁ0.033 (12)
0.011 (14)
ꢁ0.019 (12)
ꢁ0.002 (14)
ꢁ0.021 (12)
ꢁ0.011 (15)
0.0049 (10)
0.0057 (12)
0.070 (12)
0.035 (13)
0.011 (12)
0.025 (13)
0.026 (13)
0.014 (12)
0.006 (11)
ꢁ0.003 (11)
0.053 (15)
0.0388 (14)
0.0562 (18)
0.136 (14)
0.129 (14)
0.139 (17)
0.128 (16)
0.18 (2)
0.141 (18)
0.17 (2)
0.148 (19)
0.17 (2)
ꢁ0.0038 (12)
ꢁ0.0108 (13)
0.012 (11)
ꢁ0.057 (13)
ꢁ0.036 (13)
ꢁ0.018 (14)
0.008 (17)
0.0431 (15)
0.0492 (16)
0.133 (13)
0.175 (18)
0.119 (16)
0.146 (18)
0.145 (19)
0.119 (15)
0.100 (14)
0.127 (16)
0.149 (19)
0.007 (13)
ꢁ0.015 (14)
ꢁ0.007 (14)
0.004 (16)
0.0441 (3)
0.0529 (4)
0.041 (2)
0.038 (2)
0.033 (2)
0.038 (3)
0.037 (3)
0.038 (3)
0.042 (3)
0.038 (2)
0.032 (2)
0.0006 (2)
ꢁ0.0047 (3)
ꢁ0.0003 (18)
ꢁ0.0061 (18)
ꢁ0.006 (2)
ꢁ0.013 (2)
ꢁ0.008 (2)
ꢁ0.005 (2)
ꢁ0.004 (2)
ꢁ0.004 (2)
ꢁ0.007 (2)
0.0059 (2)
0.0060 (3)
ꢁ0.0044 (17)
0.0055 (17)
0.004 (2)
0.003 (2)
0.004 (2)
0.006 (2)
0.005 (2)
0.003 (2)
0.003 (2)
0.0394 (3)
0.0588 (4)
0.040 (2)
0.045 (2)
0.044 (3)
0.043 (3)
0.047 (3)
0.046 (3)
0.053 (3)
0.043 (3)
0.043 (3)
ꢁ0.0031 (2)
ꢁ0.0120 (3)
ꢁ0.0016 (18)
ꢁ0.0064 (19)
0.000 (2)
0.0493 (3)
0.0572 (4)
0.037 (2)
0.047 (2)
0.046 (3)
0.046 (3)
0.048 (3)
0.054 (3)
0.061 (3)
0.050 (3)
0.048 (3)
0.002 (2)
ꢁ0.003 (2)
ꢁ0.001 (2)
ꢁ0.008 (3)
0.000 (2)
C8
C9
C10
C11
ꢁ0.003 (2)
Table 5
Hydrogen bond geometry and symmetry code of C7C and C7B.
Table 4
Selected interatomic distances (Å) and bond angles (ꢀ) with e.s.d's in parentheses
and dihedral angles of: a) C7C and b) C7B.
(D-H-A)
d (D-H) (Å)
D (H-A) (Å)
(D-H-A) (ꢀ)
d(D-A) (Å)
Organic chain
Bond distance (Å)
Bond distance (Å)
a) N4eH4CeCl1
b) N4eH4BeCl2
c) N4eH4AeCl2
d) N3eH3AeCl1
e) N3eH3CeCl2
f) N3eH3AeBr1
g) N3eH3BeBr1
h) N3eH3CeBr2
i) N4eH4AeBr2
j) N4eH4BeBr2
k) N4eH4CeBr1
0.960 (2)
0.960 (2)
0.960 (15)
0.960 (2)
0.960 (13)
0.960 (3)
0.960 (3)
0.960 (3)
0.960 (3)
0.960 (3)
0.960 (3)
2.477(2)
2.254(2)
2.516 (2)
2.393 (2)
2.289 (2)
2.4615(3)
2.4795 (3)
2.3413 (4)
2.596
105. (2)
167.28
107.03
153.27
166.18
153.5 (2)
160.2 (2)
163.7 (2)
131.88
163.4(2)
160.2 (2)
3.37 (2)
3.20 (2)
3.28 (2)
a) C7C
1.52 (2)
1.50 (2)
1.46 (2)
1.45 (2)
1.51 (2)
1.58 (3)
1.53 (2)
1.51 (2)
2.08 (2)
2.06 (2)
2.05 (2)
Bond angles (ꢀ)
113.0 (14)
111.6 (14)
112.8 (15)
115.3 (14)
113.4 (14)
116.4 (13)
119 (2)
ꢁ179 (3)
ꢁ176 (2)
ꢁ175 (3)
ꢁ179 (2)
177 (2)
b) C7B
N3eC10
N4eC11
C5eC6
C5eC7
C6eC8
C7eC11
C8eC9
C9eC10
C10eH3A
C10eH3B
C10eH3C
N3eC10
N4eC9
C5eC7
C5eC10
C6eC7
C6eC8
C8eC11
C9eC11
C10eH3A
C10eH3B
C10eH3C
1.487 (4)
1.486 (4)
1.512 (5)
1.507 (5)
1.521 (5)
1.523 (5)
1.500 (5)
1.501 (5)
2.026 (4)
2.011 (3)
2.025 (4)
Bond angles (ꢀ)
110.5 (3)
113.6 (3)
114.4 (3)
150.5 (2)
115.9 (3)
34.8 (2)
3.516 (12)
3.230 (13)
3.511 (3)
3.511 (3)
3.274 (3)
3.315 (3)
3.265 (3)
3.360 (3)
2.3335 (4)
2.4408 (3)
Symmetry code: a) x,1/2ꢁy,1/2 þ z, b) 1 þ x,1/2-y,1/2 þ z, c) x,1/2-y,1/2 þ z, d) 1-
x,1- y,1-z, e) 1-x,y-1/2,1/2-z, f) 1-x,-y,-z, g) 2-x,-y,-z, h) 1-x,1/2 þ y,1/2-z, i) x,1/2-y,z-
1/2, j) x-1,1/2ꢁy,z- 1/2, k) x,1/2-y,z-1/2.
C6eC5eC7
C5eC6eC8
C5eC7eC11
C6eC8eC9
C7eC5eC10
C7eC6eC8
C5eC7eC6
C6eC8eC9
C6eC8eC11
C8eC9eC11
N4eC9eC8
N4eC9eC11eC8
N3eC10eC5eC7
C10eC5eC7eC6
C7eC6eC8eC11
C5eC7eC6eC8
C8eC6eC7eC5
values with anomalies at T00(C7C) ~422 K T01(C7C)~319.7 K, such a shift
of DT~10 K and DT~16 K of T0(C7C) and T1(C7C) respectively confirms
C8eC9eC10
N3eC10eC9
N4eC11eC7
N4eC11eC7eC5
N3eC10eC9eC8
C6eC5eC7eC11
C5eC6eC8eC9
C6eC8eC9eC10
C7eC5eC6eC8
148.4 (3)
ꢁ179.2 (6)
176.6 (6)
ꢁ171.2 (6)
ꢁ172.9 (6)
179.9 (6)
179.8 (6)
the first order nature of both transitions. Insert of Fig. 4a depicts a
heating/cooling cycle of (ε0) e T at 0.81 kHz. It shows that ε0 follows
a different path on cooling, where the large drop in (ε0) values and it
temperature dependence clearly indicates an irreversible phase
transition.
Fig. 4c and d shows variation of imaginary part of the dielectric
constant (ε00) vs. temperature on heating and cooling respectively.
Results reflect anomalies observed in [ln (ε00)] vs. T, on heating and
cooling, albeit higher (ε00) magnitude.
172 (2)
Similar behavior is observed for C7B, however (ε0) values are of
much lower magnitude at low temperature T < T(1C7B) and shows
large scattering at low frequency. It undergoes thermal hysteresis of
about 4 K at T(1C7B) on cooling, whereas transition at T(2C7B) could
not be seen as it must have shifted to lower temperatures. The two
hybrids show decreasing dielectric constant as frequency increases.
3.4. Dielectric constant
3.4.1. Temperature dependence of the dielectric constant
Fig. 4a shows the real part of the dielectric constant (ε0) of C7C
between room temperature and 440 K at selected frequencies, on
heating. Variation of (ε0) with temperature reflects anomalous
changes at T3(C7C)~310 K, T2(C7C)~321.5 K, T1(C7C) ¼ 335.8 K and
T
0(C7C)~432 K. which are in reasonable agreement with endo-
3.4.2. Frequency dependence of the dielectric constant
thermic peaks observed in DTA and DSC thermographs. Fig. 4b
The variation of (ε0) as a function of angular frequency [ln (
u
)] of
depicts (ε0) -T of C7C on cooling. It shows a large decrease of (ε0)
C7C. on heating, is shown in Fig. 5a, similar results are observed on

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
63
Fig. 1. a: ORTEP view of [(CH2)7(NH3)2]X2, X ¼ Cl/Br atoms. b: Arrangements of atoms in the unit cell of [(CH2)7(NH3)2]Br2. c: Organic moieties arrangement along a-axis and the
hydrogen bond net-work of [(CH2)7(NH3)2]Cl2.

64
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
The imaginary part (ε00) of the dielectric constant as a function of
angular frequency [ln( )], of C7C, is shown in Fig. 5d and e, for
u
heating and cooling respectively. The graphs show increasing
[ln(ε00)] with temperature and decreasing with frequency according
to ε00 a uꢁ n. They also show high values of ε00 at high temperatures
and low frequencies, which can be attributed to the motion of the
charge carriers within the sample [31]. Similar characteristics of
[ln(ε00)] vs. [ln(
Fig. 5f. shows typical behavior of [ln(ε00)] vs. d[ln(
temperatures indicating higher values (ε00) on cooling which is
typical for both samples. The general features of [ln(ε00)] vs. d[ln(
)]
u
)] are observed for C7B on heating and cooling.
)] of C7B at two
u
u
graphs are characterized by a shallow minimum that shifts to
higher frequencies with increasing temperature, except for C7C in
the temperature range 295 Ke335 K, where no shallow minimum is
noted. The shallow minimum of [ln (ε00)] vs. [ln(
u)] observed for
C7C and C7B at T > T(1C7C) is similar to results of super-cooled liq-
uids, plastic crystals where the molecules are disordered with
respect to their orientation degrees of freedom as well as of ioni-
cally conducting crystals and electronic semiconductors [32]. It
demonstrates the change from the universal dielectric response
(UDR) [33] to the superliner power law (SLPL) as suggested by
Lunkenheimer and Loidl [32,34]. The graph also shows a relaxation
peak at high frequency in the temperature range 345e385 K
centered at [ln (
u
)] ~ 12.65 (f ¼ 50 kHz). The latter is somewhat
similar to the “Boson peak” that characterizes glassy samples which
is typical of vibration excitations [34].
3.5. Conductivity results
3.5.1. Temperature dependent conductivity
The variation of the ac conductivity [ln (sac)] as a function of the
reciprocal temperature [1000/T (K)] at selected frequencies of C7C,
on heating and cooling, is shown in Fig. 6a and b respectively.
Thermally activated behavior following Arrhenius relation as given
by Eq. (5) is observed.
Fig. 2. a: Lattice potential energy Upot (kJ/mol) vs. number of carbon atoms/chain (n)
of C7C and C7B. Insert (i):
DUpot (kJ/mol) vs. number of carbon atoms/chain (n). b:
Molecular volume (Vm (nm3)) vs. number of carbon atoms/chain (n) of C7C and C7B. c:
Cation volume (Vþ nm3) vs. number of carbon atoms/chain of C7C and C7B.
sacðTÞ ¼ AðTÞexpð ꢁ
DE=kTÞ
(5)
where the pre-exponential term A(T) is temperature dependent.
Anomalous changes in the variation of [ln (sac)] e [1000/T(K)] are
detected at the transitions T1(C7C) ¼ 335.8 K and T2(C7C) ¼ 319 K on
heating and at T01(C7C) ¼ 325 K on cooling. Fig. 6c depicts heating/
cooling cycle at f ¼ 2 kHz. It shows that cooling run follows the
same trajectory as the heating run with slightly higher (sac) values,
up to T ¼ 340 K. Activation energy of C7C and its fit to Eq. (6) below
are shown in Fig. 6d.
cooling and will not be shown. Fig. 5b and c depict variations of
u)] with temperature on heating and
cooling respectively. It demonstrates quite clearly the slope
slope (m) ¼ d[ln(ε0)]/d[ln(
changes taking place at the transitions T3(C7C)
¼
310 K,
T2(C7C) ¼ 321 K, and T1(C7C) ¼ 335 K and T0(C7C) ¼ 432 K on heating
and at T3(C7C) ¼ 308 K, T02(C7C) ¼ 318.5 K, T01(C7C) ¼ 329 K and
T00(C7C) ¼ 421 K on cooling.
Table 6
Number of carbon atom/chain (n), lattice potential energy (Upot kJ/mol), molecular volume (Vm nm3) and cation volume (Vþ nm3) of [(CH2)n(NH3)2] X2, X ¼ Cl/Br, n ¼ 2, 3, 4, 5, 6
and 7. Calculation were carried out from structure data measured at room temperature except for [C2H10N2]Br2 and [C5H16N2]Br2 which were measured at 100 K and 150 K
respectively.
Sample
Sp. Gr.
n
(Upot) kJ/mol
Vm (nm3)
Vþ (nm3)
Ref.
C2H10N2Cl2
P21/c
P21/c
C2/m
Pna21
P21/c
P21/c
Pbam
P21/c
P21/c
P21/c
P21/c
P21/c
P21/c
P21/c
2
2
2
3
4
4
5
5
6
6
6
6
7
7
1868.7
1800.7
1811.0
1762.6
1725.6
1680.9
1649.5
1645.4
1628.4
1594.3
1623.3
1592.5
1560.8
1569.9
0.151
0.174
0.170
0.188
0.204
0.226
0.243
0.245
0.255
0.277
0.258
0.278
0.301
0.294
0.092
0.101
0.170
0.129
0.145
0.153
0.183
0.172
0.195
0.204
0.199
0.206
0.228
0.234
[6]
[7]
[8]
[9]
[10]
[11]
[15]
[16]
[12]
[13]
[14]
[14]
This work
This work
C2H10N2Br2
C2H10N2Br2(100 K)
C3H12N2Cl2
C4H14N2Cl2
C4H14N2Br2
C5H16N2Cl2
C5H16N2Br2(150 K)
C6H18N2Cl2
C6H18N2Br2
C6H18N2Cl2
C6H18N2Br2
C7H20N2Cl2
C7H20N2Br2

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
65
Fig. 3. DSC thermograph of C7C and C7B. Inserts (i): DTA measurements at a rate of 5 ꢀC/min. of C7C. Inserts (ii): DTA measurements at a rate of 5 ꢀC/min. of C7B.
an increase in molecular mobility and conductivity. Besides, for the
larger ion the charge is more spread over the larger ionic surface,
hence reduces the charge surface density. This leads to decrease of
Coulomb interaction hence decreasing inter-ionic interactions
which results in an increase of mobility and conductivity.
a
D
E ¼
D
E0½1 ꢁ expð ꢁ f0=f Þꢃ
(6)
where
D
E0 is the activation energy in limit f / 0 and
a
is a constant
with values between 0 <
temperature, phase (I), Ecool
the range of ionic hopping.
a
< 1.0. It can be seen that in the high
D
>
D
Eheat with activation energy E0 in
D
3.6. Frequency dependence
Fig. 7a and b depicts [ln (sac)] vs. [1000/T(K)] of C7B at selected
frequencies, on heating and cooling respectively. results below T1
and T01, (sac) are nearly temperature independent but strongly
frequency dependent suggesting extrinsic type conduction, with
Fig. 8a and b shows frequency dependence of conductivity at
different temperatures as [ln (sT)] vs. [ln (
atures of C7C on heating and cooling respectively. Inserts (i) and (ii)
show [ln (sT)] vs. [ln ( )] at selected temperatures of C7B on
u)] at selected temper-
activation energy
changes of conductivity are observed at T1(C7B) ¼ 338 K on heating
and at T0
DE (C7B) ~0.013 eV on heating. Anomalous
u
heating and cooling respectively. At low temperatures, and low
frequencies few data points are scattered and have been omitted
from the plots. The graphs display typical properties of experi-
mental conductivity of most ionic conductors as well as glassy
materials [33,37,38].
The dispersive behavior of the conductivity is generally
expressed by Jonscher's universal dispersive response (UDR) as
given by Eq. (7) [33].
¼ 334 K on cooling. Fig. 7c shows [ln (sac)] vs. [1000/T
(C7B)
(K)] at f ¼ 6 kHz for C7C and C7B on heating in the temperature
range above T1(C7C). It indicates higher conductivity of C7B. Similar
behavior is observed for the cooling cycle, see Fig. 7d. The two
samples show a gradual increase of conductivity as temperature
increases, Figs. 6 and 7(a, b), such that the curves tend to merge at
high temperatures which implies frequency dependent mobility.
Fig. 7c and d depicts frequency dependence of
DE and its fit to
sdc þ AðTÞusðTÞ
(7)
Eq. (6) in the temperature range T > T1 of C7C and C7B on heating
and cooling respectively. Table 7 lists fit parameters for high tem-
perature phase (I) and low temperature phase (II) of the two
samples on heating and cooling. Due to the limited number of data
sT
¼
sdc
þ
sac
¼
where sdc and sac are the DC conductivity due to band conduction
and AC conductivity is related to hopping conduction respectively,
and the pre-exponential factor A (T) is a temperature-dependent
constant and the exponent s(T) measures the degree of correla-
tion, It usually has values between 0 in case of random hopping and
tends to 1.0 for correlated hopping [37,38]. At higher frequencies,
conductivity increases and eventually starts to attain a high-
frequency plateau. Such plateaus are known to exist in fast ionic
conductors such as RbAgI5 and Na-b’’-alumina [39]. First attempts
to fit the data of Fig 8a to Eq. (7) were successful in temperature
region below T~340 K, but failed at higher temperatures where
good fits were obtained using the superlinear power law Eq. (8)
[36]:
points above T0(C7C), no calculations of DE were performed.
The activation energy values in phase (I) lie in the range of va-
cancy conduction indicating that hopping of halide ions among
vacant sites are responsible for conduction [35]. At low tempera-
tures (T < T2(C7C)) activation energy of C7C (on heating) is
~0.4 eV which could be associated with proton conduction [36].
Fig. 7c and shows higher conductivity values for C7B
DE
d
compared to C7C. This can be attributed to differences in the ionic
size of the halide ions and their different electro-negativity which
affects both the hydrogen bonding and the coulomb interactions.
For the larger size halide ion (Brꢁ) the hydrogen bond strength is
lower than that of the smaller (Clꢁ) ion. The decrease of the
hydrogen bond strength may be looked at as a decrease of the
interaction of the charge carrier with its environment and thus to
sT
ð
u
Þ ¼ sdcþA1uðTÞS1ðTÞþA2ðTÞuS2ðTÞ
(8)

66
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Fig. 4. a: Real part of dielectric constant (ε0) vs. T (K) of C7C on heating. b: (ε0) vs. T (K) of C7C on cooling. c: Imaginary part of the dielectric constant (log (ε00)) vs. temperature of C7C
on heating. d: Imaginary part of the dielectric constant (log(ε00)) vs. temperature of C7C cooling.
Good fits were also obtained using Eq. (8) for C7C over the whole
temperature range on cooling as well as for C7B data on heating and
cooling. Above 340 K the graphs are characterized by four regions:
(i) an almost temperature-independent plateau region at the
the low temperature range [36]. It also reveals change in activation
energy which can be associated with phase transition due to
conformation and reorientation of the chain in that temperature
range.
lowest frequency in which
s
¼ cf0; (ii) Jonscher (UDR) regime
Parameters s and [lnA] vs. temperature are shown in Fig. 10b.
Below T ¼ 310 K parameter s is nearly temperature independent
and maintains a value 0.83 0.01, whereas it maintains a value of
0.77 0 .01 above it. According to [37,38] conductivity by tunneling
is function of frequency and independent on temperature, the
where
s
¼ cfs1, (0 < s < 1); (iii) a region of high-frequency disper-
sion, where
s
¼ cfs2 and (iv) a plateau region. Fig. 9a and b shows
fits of [ln (sT)] vs. [ln(u)] of C7C, on heating and cooling, at selected
temperatures in regions below and above 340 K according to Eqs.
(7) and (8) respectively. Fig. 10a depicts variation of fit parameter
frequency dependence arises from term
tance. The parameter s is given by Refs. [37,38]:
u
R4 where R is the dis-
(s0
K)) vs. temperature, as [ln(s0
340)] vs. 1000/T. The
(T< 340
(T<
calculated activation energy values are
299 < T(K) < 310 K and
Ea ¼ 0.49 eV for 310 < T(K) < 327. It
suggests that proton conduction is responsible for conduction in
DEa
¼
0.32 eV for
D

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
67
Fig. 5. a: [ln(ε0)] as function of angular frequency [ln(
u
)] of C7C on heating. b: slope (m) ¼ d[ln(ε0)]/d[ln(
u
)] vs. temperature of C7C on heating. c: slope (m) ¼ d[ln(ε0)]/d[ln(
u
)] vs.
temperature of C7C on cooling. d: [ln(ε00)] as a function of angular frequency [ln(
u
)] of C7C on heating. e: [ln(ε'')] as a function of angular frequency [ln(u)] of C7C on cooling. f.
Typical behavior of [ln(ε00)] vs. d[ln(
u)] of C7B for heating/cooling cycle.
tunneling mechanism and that their different values is a result of
the phase transition, where the Ru and potential deformation
change due to conformation and orientation of the chain. [lnA]
s ¼ 1 þ 4=ln½
u
T0ꢃ
(9)
shows also changes from (ꢁ25.42 0.07(
(ꢁ24.35 0.4(
.cm)ꢁ1) above.
Fig. 10c depicts s0(T> T1) as function of reciprocal temperature,
the calculated activation energy
U
.cm)ꢁ1) for T < 309 K to
which shows that s is independent of T. Considering t0 to be of the
order of an inverse of the optical phonon frequency (~10ꢁ13 s) and
U
for typical audio frequency (
u s
~ 104 ꢁ1) an s value of ~0.8 is ob-
D
E ¼ 0.78 eV is a reasonable
tained. The exact value depends on the magnitude of the defor-
mation potential for the localized states and on Ru [38]. Hence, one
can suggest that the obtained s values of 0.83 0.01 (T < 310 K) and
0.77 0.01 (T > 310 K) are within the range observed for proton
agreement with results listed in Table 7 as obtained from [ln(sT)] vs.
1000/T plot.
The fit parameters s1, [ln (A1)] and s2, [ln (A2)] of C7C are shown

68
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Fig. 6. a: Ac conductivity [ln (sT)] vs. [1000/T (K)] at selected frequencies of C7C on heating. b: Ac conductivity [ln (sT)] vs. [1000/T(K)] at selected frequencies of C7C, on cooling. c:
Ac conductivity [ln (sT)] vs. [1000/T(K)] for a heating/cooling cycle of C7C at f ¼ 2 kHz d: Activation energy ( E(eV)) of C7C and its fit to Eq. (6).
D
of the exponent s with temperature [37] which can be ruled
out as possible mechanism of conduction of the presently
investigated samples. Overlapping large polarons (OLPs)
show linearly decreasing s up to a certain temperature, fol-
lowed by an increase in s at higher temperatures [37] thus,
the observed variation of the exponent s cannot be associ-
ated with OLPs. Correlated barrier hopping model [36,37]
predicts an increase in the exponent s towards unity as
temperature tends to 0 K which rules out this mechanism as
well.
in Fig. 10d and e respectively. General gradual decrease of s1 and s2,
an increase of [ln (A1)] and [ln (A2)] are observed as temperature
increases with values 0.3 < s1 < 0.45 and 1.48 < s2 < 1.6. One can
summarize the variation of ln (sT) with frequency at selected
temperatures as follows:
(i) At high temperatures, in the low-frequency range, (dc con-
ductivity) prevails. The dependence of the ‘‘universal’’
exponent s on temperature and frequency is related to the
conduction mechanism [33,37,38]. The variation of the
exponent s reflects the changes in the conduction mecha-
nism throughout the temperature range investigated, and
the phase change is expected to be manifested in the varia-
tion of s with temperature. In the case of quantum tunneling
model the exponent s has values ~0.8 and is temperature
independent [37,38], as was found in the temperature range
T < 308 K. For small polarons conduction, there is an increase
In the context of the jump relaxation model [40], strong con-
nections can be made between the frequency response and the
temperature dependence of the conductivity as analyzed using the
Arrhenius approach.
(i) The frequency response is entirely due to translational and
localized hopping. Translational hopping gives the long

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
69
Fig. 7. a: [ln (sT)] vs. [1000/T(K)] of C7B at selected frequencies, on heating. b: [ln (sT)] vs. [1000/T(K)] of C7B at selected frequencies, on cooling. c: [ln (
sT)] vs. [1000/T(K)] at
f ¼ 6 kHz of C7C and C7B on heating. d: [ln (sT)] vs. [1000/T(K)] at f ¼ 6 kHz for C7C and C7B on cooling. e: Activation energy
DE(eV) vs. [ln(f(Hz)] and its fit to Eq. (6) of C7C and C7B.
f: Activation energy (DE) vs. [ln(f (Hz)] and its fit of C7C and C7B on cooling.
Table 7
observation time is too short for all jumps to be successful;
the neighborhood cannot completely relax to the new posi-
tion of the ion after its jump. As a result, the activation en-
ergy involved in this translational or rotational hopping is
smaller than that involved in the long-range diffusive
conduction.
Activation energy fit parameters of C7C and C7B according to Eq. (6).
Sample Phase E0 (eV) F (Hz)
Heat 0.79 0.02 2813 603 0.67 0.09
D
a
C7C
C7C
C7C
C7C
C7B
C7B
C7B
C7B
I (424-388 K)
II (325-309 K) Heat 0.461 0 .006 98.2 13.0 0.715 0.004
I0 (424-348 K) Cool 0.81 0.01
906 134
396 119
0.52 0.03
0.78 0.13
2474 421 0.87 0.10
II0(344-325 K) Cool 0.47 0.016
(iii) Finally, the very low activation energy is observed which is
attributed to reorientation and/or liberation motion of the
organic cation, impurities or space charges.
I (424-388 K)
II T < 336 K)
Heat 0.91 0.02
Heat 0.014 frequency independent
2684 294 0.87 0.018
Cool 0.013 frequency independent
I0 (375e424 K) Cool 0.98 0.07
II0 T < 336
Thus, it seems that the results of the conductivity can be
explained in terms of the jump relaxation model.
The study of the two hybrids indicates that replacement of
chloride by bromide does not change conductivity mechanism. This
would be expected since the differences in the structure charac-
teristics, bond angles and bond lengths are minimal. It slightly af-
fects conductivity values and activation energy which is related to
differences of halide ion size and their electronegativity.
range electrical transport in the limit of very long times, that
is when the frequency tends to zero.
(ii) The dispersive behavior of the conductivity against fre-
quency, which commences at the high-frequency end of the
dc plateau, is associated with the activation energy,
DE,
determined from the Arrhenius plots of the temperature
dependence of conductivity. In this frequency range, the

70
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Fig. 8. a: ln[sT
(
u
)] vs. ln[
u
(sꢁ1)] of C7C at selected temperatures on heating. Insert (i):ln[sT
(
u
)] vs. ln[
u (u)] vs. ln[u
(sꢁ1)] of C7B at selected temperatures on heating. b: ln[sT (sꢁ1)]
of C7C at selected temperatures on cooling. Insert (ii): ln[sT (u)] vs. ln[u
(sꢁ1)] of C7B at selected temperatures on cooling.
4. Conclusion
comparison to lattice potential of [CnH2nN2H6X2]; n ¼ 2,3, …6 and
X ¼ Cl/Br.
X-ray analysis of the room temperature phase of [(CH2)7(NH3)2]
Calorimetric studies showed two transitions at T1 ¼ 333.8 K and
T2 ¼ 302.2 K for the bromide hybrid ascribed to chain melting. The
chloride hybrid undergoes thermotropic transitions at T0 ¼ 434 K.
Near ambient, it showed three transitions at T1 ¼ 330 K, T2 ¼ 319 K
and T3 ¼ 308 K. These transitions are associated with order-
disorder change of 1, 7-diammonium chain. Dielectric constant
results confirmed the phase transitions. Conductivity of the two
X2, X ¼ Cl/Br shows a monoclinic P21/c unit cell with dimension:
a ¼ 4.7838 (2) Å, b ¼ 16.9879 (8) Å, c ¼ 13.9476 (8) Å,
b
¼ 97.773 (2)ꢀ
and a ¼ 4.7952 (10) Å, b ¼ 16.9740 (5) Å, c ¼ 13.9281 (5) Å,
b
¼ 97.793 (2)ꢀ for the chloride and bromide hybrids respectively.
The calculated lattice potential energy of chloride is higher than
that of the bromide and both hybrids have the lowest Upot in

M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
71
Fig. 9. a: ln[sT
(
u
)] vs. ln[
u
(sꢁ1)] fit to Eq. (8) of C7C at selected temperatures on heating. Symbols are data points and lines are the fits. b: ln[sT
(
u
)] vs. ln[
u
(sꢁ1)] fit to Eq. (8) of C7C
at selected temperatures on cooling. Symbols are data points and lines are the fits. c: ln[sT
points and lines are the fits. d: ln[sT )] vs. ln[
(u)] vs. ln [u
(sꢁ1)] of C7C and C7B fit to Eq. (8) at T < T1 on heating. Symbols are data
(
u
u
(sꢁ1)] of C7C and C7B fit to Eq. (8) at T < T1 on cooling. Symbols are data points and lines are the fits.
hybrids is thermally activated, where that of bromide is higher than
chloride. At high temperatures, activation energy values are in the
range ionic hopping (Cl/Br) among vacant sites for both samples. On
heating, proton tunneling prevails in the temperature range
T < 309 K while proton hopping following UDR prevails in the
temperature range 319 < T (K) < 330, indicating change of con-
duction mechanism with structure phase change for C7C. Impurity
conduction is effective for C7B at T < 330 K. Activation energy
obtained on heating is always of higher values than that obtained
on cooling for both hybrids. A cross over from Jonscher's universal
dielectric relaxation (UDR) in the temperature range T < 325 K to
superlinear power law (SLPL) for T > 340 K according to the jump
relaxation model is observed, for C7C hybrid on heating. Conduc-
tion follows SLPL on cooling for C7C and on heating and cooling for
C7B.

72
M.F. Mostafa et al. / Journal of Molecular Structure 1127 (2017) 59e73
Fig. 10. a: Fit parameter [ln(s0)] vs. 1000/T (K) on heating at T < T1. b: Fit parameters (s) and [ln(A)] vs. temperature on heating. c: Fit parameter [ln(s0)] vs. 1000/T (K) on heating at
T > T1. d: Fit parameters (s1) and [ln(A1)] vs. temperature on heating at T > T1. e: Fit parameters (s2) and [ln(A2)] vs. temperature on heating at T > T1.
1128e1136.
Supplementary material
[5] S. Takami, T. Sato, T. Mousavand, S. Ohara, M. Umetsu, T. Adschiri, Mater. Lett.
61 (2007) 4769e4772.
[6] M. Gabro, R. Lalancette, I. Bemalm, Acta Cryst. E65 (2009) o1352.
[7] I. Sotofte, Acta Chem. Scand. A 30 (1976) 309e311.
[8] C. Arderne, G.J. Kruger, Acta Cryst. E66 (2010) o2470.
[9] I.P. Markiewicz, E. Zielaskiewicz, W. Paryzek, M. Kubicki, Acta Cryst. E 67
(2011) 0371e0372.
[10] K. Chandrasekhar, V. Pattabhi, Acta Cryst. B 63 (1980) 2486e2488.
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CCDC 806007 contains the supplementary crystallographic data
for sample of chemical formula C7H20Cl2N2 and CCDC 805298 for
sample of chemical formula: C7H20Br2N2. These data can be ob-
tained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
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