First radical cаtion salt of bis(ethylenedithio)tetrathiafulvalene with organic anion [С(NCN)2NH2]–: synthesis, structure, and conducting properties

Article abstract of DOI:10.1007/s11172-016-1548-z

The electrochemical oxidation of bis(ethylenedithio)tetrathiafulvalene (ET) in the presence of simple dicyanamide salts of rare-earth metals with the general formula M[N(CN)₂]₃ (M = Gd³⁺, Dy³⁺, and Ho³⁺) as electrolytes was studied for the first time. A novel radicalcаtion salt α-ЕТ₂[С(NCN)₂NH₂] with the unexpected (2,1-dicyano)guanidine anion was synthesized. The crystal structure of the salt and its conducting properties were studied. The structure of the salt is layered with alternating conducting radical-cation and insulating anionic layers. The cationic layers of the α-type are formed by two crystallographically independent radical-cations of ET of various charges. The anionic layers are formed of [С(NCN)₂NH₂]^– anions linked by hydrogen contacts into chains. The crystals of ЕТ₂[С(NCN)₂NH₂] demonstrate a semiconducting character of conductivity in a temperature range of 300—100 K.

Full text of DOI:10.1007/s11172-016-1548-z

Russian Chemical Bulletin, International Edition, Vol. 65, No. 8, pp. 2034—2039, August, 2016
2034
First radical cаtion salt of bis(ethylenedithio)tetrathiafulvalene
with organic anion [С(NCN)2NH2]–:
synthesis, structure, and conducting properties
N. D. Kushch,a N. G. Spitsina,a A. M. Kolesnikova,a and S. V. Simonovb
aInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (496) 522 3507. Еꢀmail: kushch@icp.ac.ru
bInstitute of Solid State Physics, Russian Academy of Sciences,
2 ul. Akad. Osip´yana, 142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (496) 522 8160
The electrochemical oxidation of bis(ethylenedithio)tetrathiafulvalene (ET) in the presꢀ
ence of simple dicyanamide salts of rareꢀearth metals with the general formula M[N(CN)2]3
(M = Gd3+, Dy3+, and Ho3+) as electrolytes was studied for the first time. A novel radicalꢀ
cаtion salt αꢀЕТ2[С(NCN)2NH2] with the unexpected (2,1ꢀdicyano)guanidine anion was synꢀ
thesized. The crystal structure of the salt and its conducting properties were studied. The
structure of the salt is layered with alternating conducting radicalꢀcation and insulating anionic
layers. The cationic layers of the αꢀtype are formed by two crystallographically independent
radicalꢀcations of ET of various charges. The anionic layers are formed of [С(NCN)2NH2]–
anions linked by hydrogen contacts into chains. The crystals of ЕТ2[С(NCN)2NH2] demonꢀ
strate a semiconducting character of conductivity in a temperature range of 300—100 K.
Key words: radicalꢀcаtion salt, bis(ethylenedithio)tetrathiafulvalene, dicyanamide salts of
rareꢀearth metals, electrocrystallization, structure, conductivity.
A novel scientific trend related to the production of
ity induced by magnetic field, which was observed in crysꢀ
tals of κꢀ(BETS)2FeCl4 and κꢀ(BETS)2FeBr4.8,9
bi(multi)functional materials appeared in the recent
10—15 years in the chemistry and physics of radicalꢀcatꢀ
ion salts based on chalcogenꢀcontaining πꢀdonors. The
structures of these materials are formed by two spatially
separated subsystems, each of which exhibits different
properties, for example, such as conductivity and photoꢀ
chromism, conductivity and magnetism.1,2 The works on
the synthesis and study of bifunctional molecular comꢀ
pounds combining the conducting and magnetic properꢀ
ties have been carried out most actively in the recent time.
At the moment, investigations in this direction are conꢀ
centrated on the family of lowꢀdimensional conductors
based on radicalꢀcation salts with paramagnetic anionic
complexes.1 In these materials the conductivity is related
to electrons in organic layers, whereas the magnetic propꢀ
erties are usually determined by localized ions of transiꢀ
tion metals in insulating layers. In particular, the coexistꢀ
ence of superconducting and paramagnetic properties2—4
or even antiferromagnetic properties5—7 was found in salts
of bis(ethylenedithio)tetrathiafulvalene (ET) and bisꢀ
(ethylenedithio)tetraselenafulvalene (BETS). Moreover, it
was found that the interaction of localized spins in insuꢀ
lating layers with πꢀelectrons in conducting layers can
result in such an unusual phenomenon as superconductivꢀ
A combination of conducting and magnetic subsystems
in crystals of the radicalꢀcation salts and various manifesꢀ
tations of synergetic effects also can favor the appearance
of new properties. In addition to traditionally used halide,
cyanide, and oxalate transition metal complexes, dicyanꢀ
amido metallates recently attract researchers attention as
magnetic counterions in radicalꢀcation salts.10—12 These
complexes are characterized by a great variety of strucꢀ
tures and exhibit diverse magnetic properties (ferromagꢀ
netism, antiferromagnetism, and paramagnetism), which
depend on the character of exchange interactions between
unpaired dꢀelectrons of the metal atoms through the bridgꢀ
ing ligands N(CN)2–. A relationship between the nature
of the dꢀmetal and composition of the synthesized radiꢀ
calꢀcation salts was found by the study of the electroꢀ
chemical oxidation of ET in the presence of dicyanamides
of dꢀmetals (Mn2+, Co2+, Сr3+, and Сu2+) as electrolytes.
It was established that different products were obtained
depending in the metal nature.10—18 However, only the
use of dicyanamidomanganates in the form of simple
(Mn[N(CN)2]2) or complex (Ph4P{Mn[N(CN)2]3}) salt
as electrolytes resulted in the formation of crystals with
dicyanamidometallate anions: (ET)2{Mn[N(CN)2]3} and
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2034—2039, August, 2016.
1066ꢀ5285/16/6508ꢀ2034 © 2016 Springer Science+Business Media, Inc.

Radical cation salt with [C(NCN)2NH2]– anion
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2035
and (ET)2{MnCu[N(CN)2]4}.11,14 We have recently synꢀ
thesized a novel radicalꢀcation salt based on the BETS
donor (κꢀBETS2{Mn[N(CN)2]3}), which combines the suꢀ
perconducting (Тc = 5.75 K at Р = 0.4 Kbar) and antiferꢀ
romagnetic properties.19 Relationships were observed in
this salt between the metal—dielectric phase transition in
the conducting BETS subsystem and the formation of the
shortꢀrange magnetic order in insulating anionic layers in
the range of the temperature of the metal—insulator
transition.19,20 As established later, the metal—dielectric
transition is also accompanied by the antiferromagnetic
transition in the conducting sublattice.21
ied as electrolytes. When Ho[N(CN)2]3•2Н2О +
(Ph4P)[N(CN)2] (1 : 1) mixture is used as an electrolyte,
orthorhombic crystals of radicalꢀcation salt 1 are formed
having the counterion [C(NCN)2NH2]–, which differs
from the starting anion in the electrolyte. The introducꢀ
tion of simple salts of Gd3+ or Dy3+ dicyanamides into the
electrolyte under similar synthesis conditions is accompaꢀ
nied by the growth of crystals of an organic conductor of
the known structure, viz., bis(ethylenedithio)tetrathiaꢀ
fulvalene dicyanamide dihydrate (α´´ꢀЕТ2N(CN)2•2Н2О,
2).18 The formation of crystals of this salt could be asꢀ
sumed on the basis of the dissociation of the electrolyte
components in the solution to form N(CN)2– anion. The
latter can participate in the formation of both metalloꢀ
complex anions Ho3+ (in particular, {Ho[N(CN)2]6}3–
)
and related radicalꢀcation salts and radicalꢀcation salts
containing no metals. However, the presence of the
[С(NCN)2NH2]– ion in the salt was quite unexpected.
We have previously found that crystals of salt α´´´ꢀ
(ET)6(NO3)3•2(C2H5O2N3) containing two biuret
(C2H5O2N3) molecules were grown during the electroꢀ
chemical oxidation of ET in the presence of electrolyte
Cr[N(CN)2]1.5(NO3)1.5•6H2O instead of the expected
radicalꢀcation salt with the metallocomplex anion.18 As
shown earlier,16 the formation of biuret molecules is
a result of hydrolysis of the terminal —С≡N groups of the
dicyanamide anion. In this case, the formation of anion
[С(NCN)2NH2]– upon the electrocrystallization of ET in
the presence of the simple holmium salt as an electrolyte
is also related, probably, to the hydrolysis of the —С≡N
groups of the [N(CN)2]– anion followed by condensation
presumably via Scheme 1.
The study of magnetic dicyanamides of rareꢀearth
4fꢀelements as magnetic counterions is of special interest.
Unlike dꢀmetals, 4fꢀelements are characterized by high
anisotropy of magnetic properties and a higher coordinaꢀ
tion number in complex salts and exhibit luminescence
properties. The appearance of new properties cannot be
excluded in radicalꢀcation salts with anions of this type.
In this work, we studied the electrochemical oxidation
of ET in the presence of simple dicyanamide salts of rareꢀ
earth metals (REM) with the general formula M[N(CN)2]3
(M = Gd, Dy, Ho) as electrolytes. Radicalꢀcation salt
ЕТ2[C(NCN)2NH2] (1) with the unexpected (2,1ꢀdiꢀ
cyano)guanidine anions [C(NCN)2NH2] was synthesized
for the first time, and its crystal structure and conducting
properties were studied.
The optimum conditions for crystal growth of salts 1
and 2 are given in Experimental. The absence of metals in
the composition of radicalꢀcation salts 1 and 2 were preꢀ
liminarily established by electronꢀprobe Xꢀray spectral
microanalysis (EPMA). The final compositions of both
salts were found by the full Xꢀray diffraction analysis. The
main crystallographic data and structure refinement paraꢀ
meters for salt 1 are presented in Table 1.
Results and Discussion
The electrochemical oxidation of ET was carried out
in various solvents (dichloromethane—EtOH (96%),
1.1.2ꢀtrichloroethane—EtOH (96%), chlorobenzene—
EtOH(abs.)) in the presence of simple salts of REM diꢀ
cyanamides with the general formula M[N(CN)2]3•2Н2О
The crystals of 1 have a nonꢀcentrosymmetric layered
structure in which conducting radicalꢀcation layers alterꢀ
nate with insulating anionic layers along the direction of
(М
= Gd, Dy, Ho). Twoꢀcomponent mixtures
(Ph4P)[N(CN)2] + M[N(CN)2]3•2Н2О (1 : 1) were studꢀ
Scheme 1

2036
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
Kushch et al.
Table 1. Main crystallographic data and refinement paraꢀ
meters for the structure of salt (ET)2[C(NCN)2]⋅NH2]
the c axis (Fig. 1). Two conducting layers per unit cell are
related to each other by the symmetry axis 21. The radicalꢀ
cation layers of the αꢀtype are formed by symmetrically
dependent stacks of ET molecules. The stack is formed by
two crystallographically independent radicalꢀcations A and
B alternating along the a axis (Fig. 2, а). The numeration
of atoms in the structure of this salt is presented in Fig. 3.
The angle between the central 1,4ꢀdithione (ТТF) fragꢀ
ments of adjacent molecules A and B in the stack is
5.25(1)°. This is a distinctive feature of the radicalꢀcation
layer in salt 1 unlike the most part of radicalꢀcation salts
with the packing of the αꢀtype in which the donor moleꢀ
cules in the stack are mutually parallel.22 The planes of the
radical cations are inclined relative to the direction of
stack (a axis) at an angle of 50.09(1)° and 53.89(1)° for A
and B, respectively. The central TTF fragments of symꢀ
metrically dependent donors from the adjacent stacks have
an inclination of 114.14(1)°. The overlap of the radical
cations in the stack is of the "ring above atom" type for
which the donor molecules are shifted relative to each
other in the cross direction (see Fig. 2, b). The intermoꢀ
lecular distances in the stack are 3.8(1) and 3.7(1) Å.
According to the stoichiometry, each radicalꢀcation
ET•+ should have the charge equal to +0.5. A comparison
Parameters
1
Formula
Molecular weight
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
C23H18N5S16
877.38
Orthorhombic
P212121
9.2417(7)
10.5926(5)
34.113(1)
90
β/deg
90
γ/deg
90
V/Å3
3339.5(3)
4
1.745
Z
dcalc/g cm–3
μ/cm–1
1.064
Scan mode
2—30.5
48178 (0.038)
10180
Number of measured reflections (Rint
Number of independent reflections
with I > 2σ(I)
)
9532
Number of refined parameters
398
R1 (I > 2σ(I))
0.033
ωR2 (for all reflections)
0.077
c
0
b
Fig. 1. Projection of the crystal structure of salt ET2[C(NCN)2NH2] along the а direction.
Note. Figures 1, 2, and 4 are available in full color in the onꢀline version on the webꢀpage (http://www.link.springer.com).
b
a
b
a
Fig. 2. а, Projection of the radicalꢀcation layer along the major axis of the molecule. b, Overlaps of the molecules in the stack of salt
ET2[C(NCN)2NH2]. Thermal ellipsoids of ~50% probability.

Radical cation salt with [C(NCN)2NH2]– anion
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2037
S(5)
Table 2. Shortened intermolecular conꢀ
tacts in the structure of salt
(ET)2[C(NCN)2NH2]
a
S(7)
S(1)
S(3)
H(7B)
C(3)
C(4)
H(9A)
C(5)
C(1)
C(2)
H(7A)
C(8)
C(7)
H(8A)
С(9)
H(10B)
H(9B)
Contact
Contact length/Å
C(6)
H(8B)
H(10A)
S(2)—S(17)
S(6)—S(17)
S(8)—S(11)
S(8)—S(15)
S(5)—S(18)
S(12)—S(17)
S(16)—S(17)
S(15)—S(18)
S(7)—S(12)
S(1)—S(18)
S(7)—S(16)
3.558
3.476
3.563
3.587
3.584
3.573
3.536
3.604
3.612
3.686
3.693
S(2)
S(4)
S(6)
S(8)
S(15)
C(13)
b
S(17)
S(11)
S(13)
H(17A)
C(15)
H(19B)
C(19)
C(12)
C(17)
H(17B)
C(18)
C(11)
H(19A)
C(20)
H(18B)
H(20A)
C(14)
C(16)
H(20B)
H(18A)
S(14)
H(5B)
S(12)
S(16)
S(18)
N(5)
c
N(2)
H(5A)
C(21)
C(23)
b
0
N(3)
N(1)
N(4)
C(22)
Fig. 3. Numeration of atoms in radicalꢀcations A (a) and B (b)
and in anion [C(NCN)2NH2]– (с) in salt ET2[C(NCN)2NH2].
Thermal ellipsoids are presented with 50% probability.
of the bond lengths of the central TTF fragment (С(1)—
С(2) = 1.357(3) Å, С(11)—С(12) = 1.390(2) Å) shows
that radicalꢀcation A has a charge close to ЕТ0, and that
of B is close to ET•+. The charge calculated by the empirꢀ
ical equation23 gives values of +0.26 and +0.99 for donor
molecules А and В, respectively. The dihedral angles beꢀ
tween the (S4C2) fragments with the edges passing along
the S(1)—S(2) and S(3)—S(4) bonds for molecules A and
along the S(11)—S(12) and S(13)—S(14) bonds for moleꢀ
cules B are 7.59(2)° and 6.22(2)°, respectively, vs 3.77(1)°
and 2.32(1)°. Molecules А and B are characterized by
a "boat" conformation. The terminal ethylene groups in both
radicalꢀcations have a eclipsed conformation. The conꢀ
ducting layer contains a series of shortened contacts of the
S...S and S...C types between the adjacent ET molecules.
The values of the contacts are given in Table 2.
The anionic layer in the crystals of salt 1 consists of
double chains formed along the a direction of the planar
[С(NCN)2NH2]– anions in which the anions are linked
by hydrogen bonds N—H...N (Fig. 4). The anion is inꢀ
clined relative to the ab plane by an angle of 12.43(4)°.
There are a series of shortened S...N contacts and hydroꢀ
gen bonds between the anionic and radicalꢀcation layers.
Their values are listed in Table 2.
a
Fig. 4. Projection of the anionic layer in salt ET2[C(NCN)2NH2].
perature range from 300 to 100 K with activation energies
of 0.16 and 0.44 eV for the lowꢀ (220—140 K) and highꢀ
temperature (250—300 K) ranges respectively (Fig. 5).
log (R/R300
)
R/R300
4000
4.0
3.0
2.0
1.0
0
3000
2000
1000
0
4.0
5.0
6.0 1000•T–1/К–1
140 160 180 200 220 240 260 280 300 T/К
The conductivity of the crystals of salt 1 at room temꢀ
perature is 2•10–2 Ohm–1 cm–1. The salt demonstrates
the semiconducting character of conductivity in the temꢀ
Fig. 5. Temperature dependence of the resiatance for a single
crystal of ET2[C(NCN)2NH2].

2038
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
Kushch et al.
equal to 1 μA cm–2 at 25 °С in an argon atmosphere. A mixture
of two salts, (Ph4P)[N(CN)2] + Ho[N(CN)2]3•2H2O (1 : 1)
(C2 = 0.5•10–3 mol L–1), was used as an electrolyte. The syntheꢀ
sis was carried out in a glass Hꢀlike twoꢀelectrode cell with the
separated cathodic and anodic compartments. Diffusion restricꢀ
tions were created with a glass porous filter no. 3. Platinum wires
1 mm in diameter served as electrodes after their preliminary
electrochemical purification in a 0.1 N sulfuric acid solution.
Black lustrous orthorhombic crystals 0.6×0.3×0.8 mm in size
were grown on the anode within 1.5—2 weeks. The crystals were
filtered off, washed with acetone, and dried in air. The plateꢀlike
crystals of 2 were obtained using the procedure similar to the
synthesis of salt 1 in the presence of the electrolyte consisting of
a 1 : 1 mixture of two salts (Ph4P)[N(CN)2] + М[N(CN)2]3•
•2H2O (М = Gd, Dy).
Energyꢀdispersive Xꢀray fluorescence analysis. The presence
of rareꢀearth elements in the electrolytes (3a—c) was monitored
by energyꢀdispersive Xꢀray fluorescence analysis on an XꢀApt M
spectrometer (COMITA, Russia) equipped with an Xꢀray tube
with the silver anode. The presence of REM was established by L
lines. The measurements for the samples containing gadolinium
and dysprosium were conducted at the following parameters:
voltage on the tube 15 kV, current 100 mA, and living time 60 s.
The measurement parameters for the detection of holmium were
as follows: voltage 25 kV, current 300 mA, and living time 60 s.
Elemental analysis and IR spectroscopy. The elemental analꢀ
yses of salts М[N(CN)2]3•2H2O (М = Gd, Dy, Ho) and
(Ph4P)[N(CN)2] were carried out on a Vario MICRO Cube anꢀ
alyzer.
The IR spectra of samples 3a—c were recorded at room
temperature on a Varian 3100 FTꢀIR spectrophotometer
(EXCALIBUR SERIES) in the frequency range from 4000 to
400 cm–1 with the Smart HART attachment of multiple attenuꢀ
ated total internal reflectance on a planar crystal of ZnSe Flat
without special sample preparation. Absorption bands in the IR
spectra were assigned on the basis of published data.24,25
Electronꢀprobe Xꢀray spectral microanalysis. The prelimiꢀ
nary compositions of single crystals of 1 and 2 were determined
by the electronꢀprobe Xꢀray spectral microanalysis method on
a JEOL JSMꢀ5800L scanning electron microscope with a thouꢀ
sandꢀfold magnification and an electron beam energy of 20 keV.
The depth of beam penetration into the sample was 1—3 μm.
Xꢀray diffraction analysis. Unit cell parameters of crystals 1
and 2 and the experimental set of reflection intensities were
obtained on an Oxford Diffraction GeminiR fourꢀcircle difꢀ
fractometer with a CCD detector (MoKб radiation, щ scan mode,
graphite monochromator) at room temperature. An absorption
correction of diffraction reflection intensities was applied by the
SCALE3 ABSPACK algorithm in the CrysAlisPro program.26
The crystal structures were determined by the ab initio method
using the Superflip program27 and refined by least squares using
the SHELXL program.28 All nonꢀhydrogen atoms were refined
in the anisotropic approximation. Hydrogen atoms were speciꢀ
fied geometrically with the thermal parameters Uiso(H) = 1.2Ueq
of the corresponding C and N atoms. The main crystallographic
data and refinement parameters of the structure of salt 1 are
presented in Table 1.
This behavior corresponds to the observed charge ordering
(charge localization) in the conducting layer of the crystal
structure.
Experimental
Bis(ethylenedithio)tetrathiafulvalene (ЕТ, Aldrich) was puꢀ
rified by recrystallization from chlorobenzene (C6H5Cl, Fluka).
tetraphenylphosphonium bromide ((Ph4P)Br, Aldrich, >99.5%),
sodium dicyanamide (Na[N(CN)2], Fluka, >96%), and REM
nitrate hexahydrates (Alfa Ventron, 99.9%) were used as received.
Synthesis of electrolytes and salts αꢀЕТ2[С(NCN)2NH2] (1)
and α´´ꢀЕТ2N(CN)2•2Н2О (2). Electrolytes M[N(CN)2]3•
•2H2O (M = Gd, Dy, Ho) used in the work were obtained
according to a described procedure24 using ion exchange in an
aqueous solution at room temperature on a column containing
5 mL of the strongly acidic ionꢀexchange resin (Merck, Ionꢀ
enaustauscher I, Art. 4765) with a capacity of 1.7 mmol mL–1
.
A 2•10–2 М aqueous solution corresponding to salt M(NO3)3•
•6H2O (M = Gd, Dy, Ho) was passed through a column before
it was filled with metal ions. The process was monitored by
a change in the pH of the eluate from acidic to neutral value.
The column was washed with bidistilled water to remove an
excess of REM nitrates, then a 25•10–2 М aqueous solution of
sodium dicyanamide was passed, and the eluate was collected.
After a portion of the solvent from the eluate solution was evapꢀ
orated at room temperature and crystals were formed, coarseꢀ
crystalline fractions were selected and dried at 100 °С to a conꢀ
stant weight. The energyꢀdispersive Xꢀray fluorescence analysis
of M[N(CN)2]3 powders unambiguously showed the presence of
the corresponding metal in the salts. The IR spectra of polycrysꢀ
talline samples of M[N(CN)2]3•2H2O contain absorption bands
corresponding to vibrations of the C≡N, N—C, and N—C≡N
bonds characteristic of coordinated dicyanamide groups in the
lanthanide(III) salts.24 The broad absorption band in a range of
3600—3000 cm–1 and the narrow bands at 1630—1650 cm–1
indicate the presence of water in the salts of the general formula
M[N(CN)2]3•2H2O (3) (М = Gd (a), Dy (b), and Ho (c)).
Elemental analysis for Gd[N(CN)2]3•2H2O (3a). Found (%):
С, 18.44; Н, 1.06; N, 32.25. GdС6Н4N9О2. Calculated (%):
С, 18.40; Н, 1.02; N, 32.21.
Elemental analysis for Dy[N(CN)2]3•2H2O (3b). Found (%):
С, 18.00; Н, 1.07; N, 31.58. DyС6Н4N9О2. Calculated (%):
С,17.98; Н, 1.00; N, 31.46.
Elemental analysis for Ho[N(CN)2]3•2H2O (3c). Found (%):
С, 18.01; Н, 1.00; N, 31.29. HoС6Н4N9О2. Calculated (%):
С, 17.92; Н, 1.00; N, 31.36. The melting points of the syntheꢀ
sized compounds were higher than 350 °С.
Compound (Ph4P)[N(CN)2] (4) was synthesized according
to a known procedure25 by the exchange reaction mixing aqueous
solutions of (Ph4P)Br and Na[N(CN)2]. The clotted white preꢀ
cipitate formed was filtered off and washed with distilled water
and diethyl ether. The product was recrystallized two times from
methanol to obtain (Ph4P)[N(CN)2] as a white powder. Found (%):
С, 77.04; Н, 4.94; N, 10.38. С26Н20N3P. Calculated (%):
С, 77.02; Н, 4.97; N, 10.37. M.p. 210.5—211 °С.
Orthorhombic crystals of compound 1 were synthesized by the
The crystals of compound 2 were identified by Xꢀray difꢀ
fraction analysis, which showed their complete identity with
salt α´´ꢀЕТ2N(CN)2•2Н2О earlier synthesized and described
by us.18
electrochemical oxidation of the donor (C1 = 0.12•10–3 mol L–1
)
in a mixture of solvents chlorobenzene—EtOH(abs.) (15 : 2,
mL) at constant current (I = 0.5 μA) and the current density

Radical cation salt with [C(NCN)2NH2]– anion
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2039
The crystallographic data for salt 1 were deposited with
the Cambridge Crystallographic Data Center (CIF file CCDC
1439588) and can be obtained free of charge at
www.ccdc.cam.ac.uk/getstructures.
Measurement of conductivity. The conductivity of the crysꢀ
tals was measured in the conducting plane of the crystal by the
standard fourꢀcontact method on an automated setup with dc in
a temperature range of 300—100 K. Platinum wire contact
(d = 10 μm) were glued to the crystal using the DOTITE XCꢀ12
graphite paste.
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The authors are grateful to L. I. Buravov for measuring
conductivity.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos. 14ꢀ03ꢀ00119
and 15ꢀ02ꢀ02723) and the NNIO (Project No. KA 1652/4ꢀ1).
16. E. B. Yagubskii, N. D. Kushch, A. V. Kazakova, L. I. Buraꢀ
vov, V. N. Zverev, A. I. Manakov, S. S. Khasanov, R. P.
Shibaeva, JETP Lett. (Engl. Transl.), 2005, 82, 93 [Pis´ma v
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hlov, A. D. Dubrovskii, E. B. Yagubskii, E. Canadell, J. Solid
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Received December 4, 2015