Synthesis, 13C NMR-MAS, AC conductivity and structural characterization of [C7H12N2]ZnCl4

Article abstract of DOI:10.1016/j.jallcom.2009.09.072

Synthesis, crystal structure, ¹³ C CP-MAS-NMR analysis and impedance spectroscopy study are reported for a new organic-inorganic hybrid salt, [C_yH₁₂N₂][ZnCl₄], consisting of one 2, 4-diammonium toluene cation and one [ZnCl₄ ]^2- anion. The Zn atom is in a slightly distorted tetrahedra coordination environment. The structure can be described by the alternation of ionic and organic layers. The cohesion of the material is assured by strong charge-assisted N-H-Cl interactions established between ammonium groups and discrete [ZnCl₄]^2- tetrahedra. Solid state ¹³ C CP-MAS-NMR spectra show seven isotropic resonances, confirming the existence of seven non-equivalent carbon atoms which are consistent with the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for single crystal and powder samples, reveals that the conduction in the material is due to a hopping process along the [100] direction.

Full text of DOI:10.1016/j.jallcom.2009.09.072

Journal of Alloys and Compounds 503 (2010) 340–344
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Synthesis, 13C NMR-MAS, AC conductivity and structural
characterization of [C7H12N2]ZnCl4
Adel Jarboui∗, Bassem Louati, Faouzi Hlel, Kamel Guidara
Laboratoire de l’état solide, Faculté des Sciences de Sfax, Sfax 3018, Tunisia
a r t i c l e i n f o
a b s t r a c t
Synthesis, crystal structure, 13C CP-MAS-NMR analysis and impedance spectroscopy study are reported
for a new organic–inorganic hybrid salt, [C7H12N2][ZnCl4], consisting of one 2,4-diammonium toluene
cationandone[ZnCl4]2− anion. The Zn atom is in aslightly distortedtetrahedracoordination environment.
The structure can be described by the alternation of ionic and organic layers. The cohesion of the material
is assured by strong charge-assisted N–H· · ·Cl interactions established between ammonium groups and
discrete [ZnCl4]2− tetrahedra. Solid state 13C CP-MAS-NMR spectra show seven isotropic resonances,
confirming the existence of seven non-equivalent carbon atoms which are consistent with the solid state
structure determined by X-ray diffraction.
Article history:
Received 21 March 2009
Received in revised form
15 September 2009
Accepted 16 September 2009
Available online 23 September 2009
Keywords:
2,4-Diammonium toluene
tetrachlorozincate (II)
Crystal structure
Impedance spectroscopy study, reported for single crystal and powder samples, reveals that the con-
duction in the material is due to a hopping process along the [1 0 0] direction.
13C CP-MAS-NMR spectroscopy
Electrical properties
© 2010 Published by Elsevier B.V.
1. Introduction
hybrid materials, are some of the most powerful forces to orga-
nize structural units in both natural and artificial systems, and they
There is an increasing interest today in open-framework mate-
rials due to the numerous high-performance properties that
these materials may present. One can find two main classes of
open-framework materials. The first corresponds to inorganic com-
pounds in which MO6 octahedra and/or MO4 tetrahedra are isolated
or share edges or apexes to form 3D frameworks which con-
tain tunnels and/or cavities where ions and/or solvent molecules
can be intercalated [1]. The second class corresponds to layered
compounds such as smectite clays [2], layered hydroxyl salts
[3] and layered double hydroxides [4]. Recently, attention has
been drawn to a novel class of open-framework materials namely
organic–inorganic hybrid materials. These systems are found to
have the advantage in many fields of applications that they combine
both inorganic and organic characters [5,6]. Inorganic materi-
als offer the potential for a wide range of electronic properties
(enabling the design of insulators, semiconductors, and metals),
magnetic and dielectric transitions, substantial mechanical hard-
ness, and thermal stability. Organic molecules, on the other hand,
can provide high fluorescence efficiency, large polarizability, plastic
mechanical properties, ease of processing, and structural diversity
[7,8]. Moreover, the non-covalent interactions, usually observed in
have important effects on the organization and properties of many
materials in areas such as biology, crystal engineering and material
science [9–13]. The hybrid materials encompass organic–inorganic
composites that alternate chemically and electronically at the
molecular level. All these properties are related to the structural
changes of these compounds depending on the effects of differ-
ent factors such as temperature and composition. In this context
we report the synthesis, the crystal structure, 13C NMR-MAS and
electrical properties of the 2,4-diammonium toluene tetrachloroz-
incate (II) compound.
2. Experimental
0.37 g (3 mmol) of C7H10N2 (ALDRICH, purity: 97%) and 0.41 g (3 mmol) of ZnCl2
(ALDRICH, purity: 98%) were dissolved in 20 ml of HCl (2 M) aqueous solution. The
obtained solution was kept at room temperature. After three days, prismatic red-
brown crystals appeared (yield: 0.93 g, 93%).
A single crystal (0.52 mm × 0.43 mm × 0.26 mm) was selected by optical exam-
ination. Crystallographic measurements were made at room temperature (graphite
monochromated Mo K␣ radiation, 0.71073 Å) using a Stoe Image Plate Diffrac-
tion System and a Siemens SMART CCD area-detector diffractometer. An empirical
absorption corrections using SADABS [14] were applied. The structure was solved
by Patterson methods and refined in the anisotropic approximation using SHELXS-
86 [15] and SHELXL-97 [16]. The main crystal data, the parameters used for
intensity data collection and the reliability factor are summarized in Table 1.
The obtained solution permits us to localize the positions of zinc and chlorine
atoms. Positions of N and all carbon atoms were located after subsequent Fourier
series analysis. Hydrogen atoms of the methyl ramification were placed in cal-
culated positions. The other H atoms were successively located in a different
∗
Corresponding author.
E-mail addresses: adeljarboui@yahoo.fr (A. Jarboui), bassem-louati@yahoo.fr
(B. Louati), faouzihlel@yahoo.fr (F. Hlel), kamelguidara@yahoo.fr (K. Guidara).
0925-8388/$ – see front matter © 2010 Published by Elsevier B.V.
doi:10.1016/j.jallcom.2009.09.072

A. Jarboui et al. / Journal of Alloys and Compounds 503 (2010) 340–344
341
Table 1
use of cross-polarization for proton with 5 ms contact time. All chemical shifts (ı)
are given with respect to tetramethylsilane, according to the IUPAC convention, i.e.
shielding corresponds to negative values. Spectrum simulation was performed by
using Bruker WINFIT software [17].
Summary of crystal data, intensity measurements and refinement parameters for
[C7H12N2][ZnCl4].
Formula: [C7H12N2][ZnCl4]
Color/shape
Crystal dimensions
Crystal system
Fw = 332.36 g mol−1
Red-brown/prismatic
0.52 mm × 0.43 mm × 0.26 mm
Monoclinic
P21/c (No. 14)
V = 1261.07(5) Å3, Z = 4, ꢀ = 2.76 mm−1
The electrical measurements were performed using a two-electrode configura-
tion on polycrystalline and single crystal samples. The polycrystalline sample was
pressed into pellets of 8 mm diameter and 1.1 mm thickness using 3t/cm2 uniax-
ial pressure. Several crystallization tests allowed us to obtain crystals with suitable
dimensions to undertake an electrical study. The used crystal has a 20 mm2 of surface
and 2 mm of thickness. We note that the great crystal surfaces are perpendicular to a
direction. Indeed, in the case of the single crystal, the measurements were performed
along [1 0 0] direction. Electrical impedances were measured in a frequency ranging
from 200 Hz to 5 MHz with the TEGAM 3550 ALF automatic bridge monitored by a
microcomputer between 408 and 468 K.
Space group
a = 6.9734(1) Å, b = 9.8088 (3) Å,
c = 18.4663(4) Å, ˇ = 93.256(1)
Temperature (K)
293(2)
Mo K␣, 0.71069, graphite
ꢂ–2ꢂ
Radiation, ꢁ (Å), monochromator
Scan angle (◦)
2ꢂ range (◦)
2.2–36.8
Range of h, k, l
−11 → 11, −16 → 8, −26 → 30
11831/5943 (Rint = 0.024)
4739
Multi-scan (SADABS)
0.542, 0.823
3. Results and discussion
Reflections collected/unique
Observed reflections [Fo > 2ꢃ(Fo)]
Absorption correction
Tmin, Tmax
3.1. Structure description
Structure resolution
Structure refinement with
Refinement
Refined parameters
Goodness of fit
Paterson methods: SHELXS-86
SHELXL-97
The asymmetric unit of the title compound is made up of one
2−
F2 full matrix
164
ZnCl4
anion and a single 2,4-diammonium toluene dication. A
view of the asymmetric unit of the structure drawing with 50%
probability thermal ellipsoids is depicted in Fig. 1. The crystal
structure consists of alternating layers of organic and inorganic
corrugated sheets stacked along [1 0 0] direction, Fig. 2. Organic
and inorganic layers are interconnected through five N–H· · ·Cl
hydrogen bonds and one bifurcated hydrogen bonding estab-
1.008
0.028, 0.085
Final R and Rw
Final R and Rw (for all data)
Largest feature diff. map
w = 1/[␴ (Fo)2 + (0.0677P)2 + 0P
0.043, 0.114
0.719, −0.166e−/Å3
P = [Fo2 + 2 Fc2]/3
lished by HN22 atom, Fig. 3. Each organic cation is linked to
Table 2
2−
four ZnCl4
tetrahedra. The corresponding N· · ·Cl distances vary
Main distances (Å) and bond angles (◦) in the [C7H12N2][ZnCl4] (e.s.d. are given in
parentheses).
between 3.15(4) and 3.31(3) Å, which can be considered relatively
weak [18]. In the inorganic layers, there are no ␲–␲ interaction
between identical parallel 2,4-diammonium toluene cations, with
face-to-face distances of 4.452(3) Å which is longer than values
observed in similar compounds [19].
Distances (Å)
Angles (◦)
ZnCl4
Zn–Cl1
Zn–Cl2
Zn–Cl3
Zn–Cl4
2.264(1)
2.284(1)
2.279(1)
2.237(1)
Cl1–Zn–Cl2
Cl1–Zn–Cl3
Cl1–Zn–Cl4
Cl2–Zn–Cl3
Cl2–Zn–Cl4
Cl3–Zn–Cl4
106.5(2)
106.7(2)
112.4(2)
110.5(2)
107.4(2)
113.1(2)
The zinc atom is tetrahedrally coordinated by chlorine atoms,
with Zn–Cl distances ranging from 2.237(5) to 2.284(4) Å and
Cl–Zn–Cl angles varying from 106.5(2)◦ to 113.1(2)◦. Those values
show a slight distortion of the ZnCl42− tetrahedra. These results are
similar to the data known for the tetrachlorozincate anion [19–21].
The organic molecule exhibits a regular spatial configuration
with normal distances C–C, C–N and angles C–C–C, C–C–N. The
main value of the C–C length of the C6-ring is 1.383(2) Å, which
is between single and double bonds and agrees with that observed
in the C6-ring of benzene derivatives [22]. All the carbon atoms
of the C6-ring are coplanar with an average deviation of 0.004 Å.
Furthermore, the distances C(1)–C, C(2)–N(1) and C(4)–N(2)
+
C7H12N2
C5–C4
C5–C6
C6–C1
C2–C3
C2–C1
C2–N1
C3–C4
C4–N2
C1–C
1.375(2)
1.375(3)
1.392(2)
1.384(2)
1.392(2)
1.467(2)
1.380(2)
1.460(2)
1.498(2)
C4–C5–C6
C5–C6–C1
C3–C2–C1
C3–C2–N1
C1–C2–N1
C4–C3–C2
C5–C4–C3
C5–C4–N2
C3–C4–N2
C2–C1–C6
C2–C1–C
119.2(2)
122.1(2)
123.0(1)
117.9(1)
119.1(1)
117.7(1)
121.6(2)
119.8(1)
118.6(1)
116.5(2)
122.3(2)
121.2(2)
C6–C1–C
Fourier maps. Main geometrical features, bond distances and angles are reported in
Tables 2 and 3.
The NMR experiments were performed at room temperature on a Bruker MSL
300 spectrometer operating at 75.48 MHz for 13C. The powdered sample was packed
in a 4 mm diameter rotor and allowed to rotate at speeds up to 10 kHz in a Doty
MAS probehead. During the whole acquisition time, the spinning rate of the rotor
was locked to the required value thanks to the Bruker pneumatic unit which con-
trols both bearing and drive inlet nitrogen pressures. The spectra were acquired by
Table 3
Main interatomic distances (Å) and bond angles (◦) involved in hydrogen bonds
(e.s.d. are given in parentheses).
N–H· · ·Cl
N–H
H· · ·Cl
N· · ·Cl
N–H· · ·Cl
N1–HN11· · ·Cl2
N1–HN12· · ·Cl2
N1–HN13· · ·Cl3
N2–HN21· · ·Cl4
N2–HN22· · ·Cl1
N2–HN23· · ·Cl3
0.95(3)
0.89(4)
0.84(3)
0.96(3)
0.95(6)
0.95(5)
2.33(2)
2.32(4)
2.48(2)
2.20(3)
2.43(2)
2.44(3)
3.26(3)
3.21(4)
3.33(3)
3.15(4)
3.22(2)
3.31(3)
175(2)
169(3)
174(3)
168(2)
140(3)
152(2)
Fig. 1. Asymmetric unit of [C7H12N2][ZnCl4], with atom labels and 50% probability
displacement ellipsoids for non-H atoms.

342
A. Jarboui et al. / Journal of Alloys and Compounds 503 (2010) 340–344
Fig. 4. Plots of experimental and fitted curves of the isotropic band of the 13C CP-
MAS-NMR spectrum of the crystalline 2,4-diammonium toluene tetrachlorozincate
(II) sample rotating at magic angles with a frequency of 10 kHz. To show all fitted
resonances, peaks observed at higher frequency are zoomed in inserted plot.
ring. The more shielded chemical shift values, 136.1 and 135.7 ppm,
can be attributed to carbon atoms, C(2) and C(4) of the C6-ring,
linked to the electronegative atoms N(1) and N(2). The chem-
ical shift values were commonly observed in aniline derivative
[23].
3.3. Electrical properties
Fig. 5 shows the plot of imaginary part (Zꢀꢀ) versus real part (Zꢀ)
of complex impedance taken over the frequency range 200 Hz to
5 MHz at different temperatures 420 K ≤ T ≤ 468 K. All the semi-
circles of the polycrystalline compound exhibit some depression
instead of a semicircle centered on the real axis. Such behavior is
indicative of non-Debye type of relaxation and it also manifests
that there is a distribution of relaxation times instead of a single
relaxation times in the material [24].
The bulk ohmic resistance relative to each experimental tem-
perature is deduced from complex impedance diagrams, it is the
interception Z0 on the real axis of the zero phase angle of extrapo-
lation in the lower frequency curve. The conductivity ꢃ is obtained
from Z0 by means of the relation: ꢃ = e/Z0S, where e and S represents
the thickness and the area of the sample, respectively. The temper-
ature dependence of the conductivity in the studied temperature
range is given in Fig. 6 for polycrystalline and single crystal as a plot
of ln(ꢃT) versus reciprocal temperature. Arrhenius-type behavior
is clearly exhibited.
Fig. 2. Crystal structure of the title compound, viewed down the c-axis, showing
the layer sequence. The big empty circles represent nitrogen atoms, light grey cir-
cles represent carbon and small empty circles represent H atoms. ZnCl4 units are
represented by tetrahedra.
[1.498(2), 1.467(2) and 1.460(2) Å], clearly indicate three single
bonds.
3.2. NMR spectroscopy
The isotropic band of 13C CP-MAS-NMR spectrum of the crys-
talline 2,4-diammonium toluene tetrachlorozincate (II) sample
rotating at magic angle with frequency 10 kHz is given in Fig. 4.
Spinning the sample at 8 kHz speed allowed us to assign the
isotropic band. Simulation of the isotropic band permits to identify
seven peaks (Table 4). The presence of seven resonances corre-
sponds to the seven carbon atoms of the organic cation. This result
proves the presence of only one organic cation in the asymmet-
ric unit of the compound. The signal at 19.7 ppm corresponds to
the methyl carbon atom. The other resonances at higher chemi-
cal shift correspond to the aromatic carbon atoms of the phenyl
A linear fit to ꢃT = Aexp(−Eꢃ/kˇT),where A is the pre-exponential
factor, Eꢃ is the apparent activation energy for the mobile ions,
kˇ is the Boltzmann constant and T is the absolute temperature,
is shown. Electrical data relative to these materials are listed in
Table 5.
The electrical properties reported in Table 5 can be com-
pared. Independently of the polycrystalline or single crystal, the
[C7H12N2][ZnCl4] compound is characterized by a higher acti-
vation energy Eꢃ (2.1 0.1) eV. However, compared with the
polycrystalline compound, the single crystal [C7H12N2][ZnCl4] is
Table 4
13C CP-MAS-NMR peaks characteristics observed in the isotropic band for the spec-
trum recorded at 10 kHz of the compound [C7H12N2][ZnCl4] with e.s.d. equal to
0.1 ppm.
Peaks
ıiso (ppm)
FWHM (ppm)
1
2
3
4
5
6
7
19.7
119.1
127.2
128.2
129.4
135.7
136.1
0.86
1.21
1.24
1.12
1.06
0.83
1.68
Fig. 3. The packing of [C7H12N2][ZnCl4], viewed down the a-axis, showing anions
and cations connected by N–H· · ·Cl hydrogen bonds (dashed lines).

A. Jarboui et al. / Journal of Alloys and Compounds 503 (2010) 340–344
343
Fig. 5. Complex impedance plots of Zꢀꢀ(ꢄ) versus Zꢀ(ꢄ) at various temperatures for
[C7H12N2][ZnCl4] compound.
Fig. 7. Normalized modulus Mꢀꢀ/Mꢀꢀ
at various temperatures for polycrystalline
max
and single crystal [C7H12N2][ZnCl4].
characterized by a higher value of ꢃ0. At 400 K, the conductivity
jumps about 5 times. This increase suggests that most of transport
properties are probably due to displacements of charge carriers
along [1 0 0] direction which corresponds to the direction of the
stacking of the corrugated organic and inorganic sheets.
An analysis of the ion conductivity relaxation process in poly-
crystalline and single crystal have been undertaken in the complex
modulus M* formalism. This formalism (M* = 1/ε* = jωC0Z*, C0 is
the vacuum capacitance of the cell) is useful in determining the
charge carriers parameters such as the ion hopping rate and the
conductivity relaxation time [25,26].
Some spectra of normalized modulus, Mꢀ/Mꢀꢀ
relative to var-
max
ious temperatures are reported in (Fig. 7) for polycrystalline and
single crystal samples. The frequency range where the peak occurs
is indicative of the transition from short-range to long-range mobil-
ity at decreasing frequency and is defined by the condition ω f = 1,
Fig. 6. Temperature dependence of ln(ꢃT) versus reciprocal temperature for
[C7H12N2][ZnCl4].
where
is the most probable ion relaxation time [27]. When
f
Table 5
temperature increases, modulus peak maxima shifts to higher fre-
quencies (Fig. 7).
Electrical parameters of polycrystalline and single crystal [C7H12N2][ZnCl4].
Fig. 8 gives the temperature dependence of the fp (fp = 1/2ꢅ
)
Polycrystalline
Single crystal
f
frequency relative to Mꢀꢀ/Mꢀꢀmax. An Arrhenius-type law is shown
and the activation energies are (1.9 0.1) and (2.0 0.1) eV for the
single crystal and polycrystalline compounds, respectively.
ꢃ (ꢄ−1 cm−1) (T = 400 K)
Eꢃ 0.1 eV)
7.07 × 10−7
3.36 × 10−6
(
2.1
2.1

344
A. Jarboui et al. / Journal of Alloys and Compounds 503 (2010) 340–344
the transport is probably in [1 0 0] direction corresponding to
the direction of stacking of the corrugated organic and inorganic
sheets.
The analysis of the temperature variation of Mꢀꢀ peak indicates
that the observed relaxation process is thermally activated. The
near value of activation energies obtained from the relaxation times
and conductivity data confirms that the transport is through ion
hopping mechanism in the investigated material.
Supplementary materials
CCDC 688770 contains the supplementary crystallographic
data for this paper. This data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Rood, Cam-
bridge CB2 1EZ, UK (Fax: (international) +44 1223/336 033; e-mail:
deposit@ccdc.cam.ac.uk).
References
Fig. 8. Inverse temperature dependence of ln(fp) versus reciprocal temperature for
polycrystalline and single crystal.
[1] S. Litty, Y. Piffard, A.K. Shukla, F. Taulelle, J. Gopalakrishnan, J. Mater. Chem. 13
(2003) 1797.
[2] T. Pinnavaia, J. Sci. 22 (1983) 365.
[3] F. Cavani, F. Trifiro, A. Vaccari, Catal. Today 11 (1991) 173.
[4] L. Poul, N. Jouini, F. Fievet, Chem. Mater. 12 (2000) 3123.
[5] A.M. Fonseca, C.J.R. Silva, N. Nunes, I.C. Neves, J. Alloys Compd. 454 (2008) 72.
[6] Z. Peng, X. Xing, X. Chen, J. Alloys Compd. 425 (2006) 323.
[7] D.B. Mitzi, K. Chondroudis, C.R. Kagan, IBM J. Res. Dev. 45 (2001) 29.
[8] I. Chaabane, F. Hlel, K. Guidara, J. Alloys Compd. 461 (2008) 495.
[9] B. Gawel, W. Lasocha, M. Zieba, J. Alloys Compd. 442 (2007) 77.
[10] K.M. Guckian, B.A. Schweitzer, R.X.F. Ren, C.J. Sheils, D.C. Tahmassebi, E.T. Kool,
J. Am. Chem. Soc. 122 (2000) 2213.
The activation energies issued from the impedance Eꢃ and mod-
ulus Ef spectra are close enough to suggest that the ion transport
in polycrystalline and single crystal are probably due to a hopping
mechanism [28].
4. Conclusions
[11] S.Y. Mao, Y. Xie, Z.X. Xie, L.S. Zheng, J. Alloys Compd. 456 (2008) 534.
[12] A.L. Gillon, A.G. Orpen, J. Starbuck, X.M. Wang, Y. Rodriguez-Martin, C. Ruiz-
Perez, Chem. Commun. (1999) 2287.
[13] L. Brammer, J.C. Mareque Rivas, R. Atencio, S. Fang, F.C. Pigge, J. Chem. Soc.,
Dalton Trans. (2000) 3855.
[14] G.M. Sheldrick, SADABS, University of Göttingen, Germany, 2004.
[15] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure Solution, University
of Göttingen, Germany, 1986.
[16] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement, Univer-
sity of Göttingen, Germany, 1997.
Crystals of a hybrid material, [C7H12N2][ZnCl4], have been pre-
pared by slow evaporation of aqueous solution HCl (2 M), C7H10N2
and ZnCl2 at room temperature. The atomic arrangement is charac-
terized by infinite corrugated layers of inorganic anions alternating
with organic sheets stacked along a direction. In addition, the two
layers spreading in this network are themselves interconnected by
weak H-bonds established between NH3 groups of organic cations
and chlorine atoms ZnCl4 tetrahedron.
[17] D. Massiot, H. Theile, A. Germany, Bruker Report, vol. 43, 1994, p. 140.
[18] I.D. Brown, Acta Crystallogr. A32 (1976) 24.
13C CP-MAS-NMR spectra evidence seven different isotropic
peaks relative to carbon atoms of one organic cation in the struc-
ture.
[19] Z.-M. Jin, N. Shun, Y.-P. Lü, M.-L. Hu, L. Shen, Acta Crystallogr. C61 (2005) m43.
[20] F. Hlel, A. Rheim, T. Guerfel, K. Guidara, Z. Naturforsch. 61B (2006) 1002.
[21] N. Guo, J. Yi, Y. Chen, S. Liao, Z. Fu, Acta Crystallogr. E63 (2007) m2571.
[22] F. Hlel, R. Thouvenot, L. Smiri, Phys. Stat. Sol. (B) 242 (2005) 1243.
[23] H.C. Galka, L.H. Gade, Inorg. Chim. Acta 357 (2004) 1725.
[24] S. Sen, R.N.P. Choudhary, P. Pramanik, Physica B 387 (2007) 56.
[25] D.P. Almond, A.R. West, Solid State Ionics 11 (1983) 57.
[26] B.V.R. Chowdari, K. Radhakrishnan, J. Non-Cryst. Solids 110 (1989) 101.
[27] H.K. Patel, S.W. Martin, Phys. Rev. B45 (1992) 10292.
[28] J.M. Réau, S. Rossignol, B. Tanguy, J.M. Rojo, P. Herrero, R.M. Rojas, J. Sanz, Solid
State Ionics 74 (1994) 65.
The electrical properties of [C7H12N2][ZnCl4] material were
studied as a function of frequency and temperature ranges (200 Hz
to 5 MHz) and (420–468 K), respectively.
Independently of the single crystal or polycrystalline state,
[C7H12N2][ZnCl4], is characterized by the same activation energy
Eꢃ (2.1 0.1) eV. However, the conductivity of the single crys-
tal (T = 400 K) is about 5 times more important suggesting that