Honeycomb sheet structures achieving high electrical conductivities in alkyl-substituted thiazolium bis(2-thioxo-1,3-dithiole-4,5-dithiolato) nickelate(III) complex salts

Article abstract of DOI:10.1246/bcsj.82.352

A series of [Ni(dmit)₂] (1) (dmit = 2-thioxo-1,3-dithiole-4,5- dithiolato) complex salts with 3,4-dimethylthiazolium (2), 2,3,4- trimethylthiazolium (3), and 3,4,5-trimethylthiazolium (4) cations (I, II, and III, respectively) were synthesized and characterized by single-crystal X-ray analysis and conductivity. The molecular structures of 1 were the same in all three complex salts. In the structure of I, the anions were arranged in hexagonal structures. Neighboring hexagons formed honeycomb sheet structures as the result of S-S interactions in the (001) plane. The sheets of the honeycomb structures were arranged along the c axis with translational symmetries that form columnar honeycomb channels along the [111] direction. In the structures of II and III, honeycomb sheet structures were formed as in I. But in contrast to I, the relative position of the stacked sheets in II and III was slightly dislocated, forming zig-zag channels instead. The IR spectra of I, II, and III show that the C=C stretching band is slightly red-shifted to 1337-1339 from 1350 cm^-1 for [Ni(dmit)₂]^-, caused by the partial oxidation of the anion. The measured values of the electrical conductivities were 0.20, 0.094, and 0.16 S cm^-1 for I, II, and III, respectively. These high conductivities may be ascribed to the partially oxidation of the anion. The S-S interactions regulate the honeycomb sheet structure of the crystal and should work as conduction pathways effectively.

Full text of DOI:10.1246/bcsj.82.352

352
Bull. Chem. Soc. Jpn. Vol. 82, No. 3, 352–357 (2009)
© 2009 The Chemical Society of Japan
Honeycomb Sheet Structures Achieving High Electrical
Conductivities in Alkyl-Substituted Thiazolium
Bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickelate(III) Complex Salts
Etsuko Tomiyama,*1,2 Kazuaki Tomono,1 Daisuke Hashizume,2 Tatsuo Wada,2 and Kazuo Miyamura1
1Department of Chemistry, Faculty of Science, Tokyo University of Science,
1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601
2RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako 351-0198
Received October 14, 2008; E-mail: j1306709@ed.kagu.tus.ac.jp
A series of [Ni(dmit)2] (1) (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) complex salts with 3,4-dimethylthiazolium
(2), 2,3,4-trimethylthiazolium (3), and 3,4,5-trimethylthiazolium (4) cations (I, II, and III, respectively) were synthesized
and characterized by single-crystal X-ray analysis and conductivity. The molecular structures of 1 were the same in all
three complex salts. In the structure of I, the anions were arranged in hexagonal structures. Neighboring hexagons formed
honeycomb sheet structures as the result of S£S interactions in the (001) plane. The sheets of the honeycomb structures
ꢀ ꢀ
were arranged along the c axis with translational symmetries that form columnar honeycomb channels along the [111]
direction. In the structures of II and III, honeycomb sheet structures were formed as in I. But in contrast to I, the relative
position of the stacked sheets in II and III was slightly dislocated, forming zig-zag channels instead. The IR spectra of I,
II, and III show that the C=C stretching band is slightly red-shifted to 1337Í1339 from 1350 cmÕ1 for [Ni(dmit)2]Õ,
caused by the partial oxidation of the anion. The measured values of the electrical conductivities were 0.20, 0.094, and
0.16 S cmÕ1 for I, II, and III, respectively. These high conductivities may be ascribed to the partially oxidation of the
anion. The S£S interactions regulate the honeycomb sheet structure of the crystal and should work as conduction
pathways effectively.
The metalÍdithiolate complex is an excellent building block
distorted honeycomb structure parallel to the (001) plane, with
cavities µ12.34 ¡ in diameter. The cavities were filled with
cations. The cations and anions linked via S£S and CÍH£S
interactions. To gain more insight into the regulated struc-
tures,8,9 we have synthesized the dmit complex salts with three
di- and trimethylthiazolium cations, whose molecular structures
are similar to the dmit ligand. In this work, we have selected
three cations for forming complex salts with [Ni(dmit)2]
anion 1; 3,4-dimethylthiazolium (abbreviated as 3,4-dmtz; 2),
2,3,4-trimethylthiazolium (abbreviated as 2,3,4-tmtz; 3), and
3,4,5-trimethylthiazolium (abbreviated as 3,4,5-tmtz; 4) cat-
ions. Hereafter, the crystals of 1 and 2, 1 and 3, 1 and 4, and 1
and 5 are abbreviated as I, II, III, and IV, respectively
(Chart 1).
for electronic materials.1,2 Transition-metal complexes of dmit
(dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) have received sig-
nificant attention since the report of the first open-shell
molecular superconductor (TTF)[Ni(dmit)2]2 (TTF = tetrathia-
fulvalene)3 and the first closed-shell molecular superconductor
[N(CH3)4][Ni(dmit)2]2.4 Although the closed-shell cations
make no contribution to the conductivity, their size and shape
play a predominant role in influencing the crystal structure, and
consequently in altering the electronic properties. Physical
properties of molecular conductors depend on the molecular
alignment in crystals. Reefman et al.5 reported the (tmiz)-
[Ni(dmit)2] (tmiz = 1,2,3-trimethylimidazolium) salt featuring
a type of cation that can be regarded as an intermediate between
an open-shell and closed-shell cation. This compound showed
a high conductivity of 0.21 S cmÕ1 compared with other
1:1 [Ni(dmit)2] complex salts. (MeQ)[Ni(dmit)2] (MeQ = N-
methylquinolinium) was characterized by single-crystal X-ray
analysis and exhibited a conductivity of 10Õ3 S cmÕ1.6 These
compounds crystallize in a non-segregated manner, displaying
a face-to-face stacking mode of the anions and cations. These
results suggested that the interaction between the ³-electronic
systems of both the cations and the anions might be responsible
for the conductivity. We have already reported the crystal
structure of the [Ni(dmit)2] complex salt with the 2,3-
diethylthiazolium (5) cation.7 In that crystal structure, S£S
intermolecular interactions between the anions formed a
Experimental
Syntheses of (3,4-dmtz)[Ni(dmit)2] (I), (2,3,4-tmtz)[Ni(dmit)2]
(II), and (3,4,5-tmtz)[Ni(dmit)2] (III). (Bu4N)[Ni(dmit)2] was
synthesized according to the literature.10 3,4-Dmtz iodide, 2,3,4-
tmtz iodide, and 3,4,5-tmtz iodide were prepared by a similar
procedure as follows: 4-methylthiazole, 2,4-dimethylthiazole, or
4,5-dimethylthiazole (20 mmol) and methyl iodide (100 mmol)
were stirred in Et2O (30 mL) for two days. The resultant solid was
filtered and washed several times with acetone and Et2O to obtain
derivatives of each methylthiazolium iodide. All reagents were of
reagent grade and used without further purification. Single crystals
were prepared by the cation-exchange method and slow inter-
Published on the web March 12, 2009; doi:10.1246/bcsj.82.352

E. Tomiyama et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 3 (2009)
353
diffusion of acetonitrile solution (25 mL) of (Bu4N)[Ni(dmit)2]
(0.05 mol) and chloroform/methanol (15:1) solution (45 mL) of
3,4-dmtz iodide (0.1 mol), 2,3,4-tmtz iodide (0.1 mol), or 3,4,5-
tmtz iodide (0.1 mol) for several days at room temperature.
Elemental analyses and IR spectra: (3,4-dmtz)[Ni(dmit)2] (I):
Anal. Found: C, 23.60; H, 1.13; N, 2.45%. Calcd for C11H8-
NS11Ni: C, 23.36; H, 1.43; N, 2.48%. IR (KBr, cmÕ1): 3106 (w),
1575 (w), 1338 (s, C=C), 1233 (w), 1169 (w), 1065 (s, C=S).
(2,3,4-tmtz)[Ni(dmit)2] (II): Anal. Found: C, 25.00; H, 1.42; N,
2.40%. Calcd for C12H10NS11Ni: C, 24.87; H, 1.74; N, 2.42%. IR
(KBr, cmÕ1): 3120 (w), 1589 (w), 1337 (s, C=C), 1246 (w), 1186
(w), 1065 (s, C=S). (3,4,5-tmtz)[Ni(dmit)2] (III): Anal. Found: C,
25.05; H, 1.42; N, 2.41%. Calcd for C12H10NS11Ni: C, 24.87;
H, 1.74; N, 2.42%. IR (KBr, cmÕ1): 3073 (w), 1595 (w), 1339 (m,
C=C), 1260 (w), 1196 (w), 1062 (m and br, C=S).
-704660 for compounds I, II, and III, respectively. Copies of the
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 Road, Cambridge, CB2 1EZ, U.K.; Fax:
+44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).
Measurements. IR spectra (KBr pellets) were measured using
a JASCO FT/IR-410 spectrophotometer. Elemental analyses were
performed with a Perkin-Elmer 2400II CHN analyzer. Conductiv-
ity measurements were carried out at ambient pressure using a two-
probe ac impedance method. Electrical contacts were prepared
using silver paste to attach 0.1 mmº gold wires (The Nilaco
CORPORATION) to the crystals. The magnitude of the applied
potential was 1 V in the (001) plane.
Results and Discussion
X-ray Crystallography. Diffraction data of I, II, and III were
collected with a Bruker AXS SMART diffractometer equipped
with CCD area detector using Mo K¡ (- = 0.71073 ¡) radiation.
The structures of I, II, and III were solved and refined using the
programs SHELXS-97 and SHELXL-97,11 respectively. All non-
hydrogen atoms were refined anisotropically. Positions of hydro-
gen atoms were calculated geometrically, and refined as riding
models. Crystallographic data are listed in Table 1. Crystallo-
graphic data have been deposited with Cambridge Crystallographic
Data Centre: Deposition numbers CCDC-704658, -704659, and
IR Measurement. The strong bands around 1350 cmÕ1 in
the IR spectra assigned to the C=C stretching band is known to
exhibit a large shift because of the formal charge of Ni(dmit)2;
1260 cmÕ1 for [Ni(dmit)2]0.29Õ, 1350 cmÕ1 for [Ni(dmit)2]Õ,
and 1440 cmÕ1 for [Ni(dmit)2]2Õ 12
Three crystals of I, II, and
.
III were 1:1 complex salts supported by elemental analyses
and crystal structure analyses. IR spectra, on the other hand,
show that the C=C stretching band has a slight red shift
(1337Í1339 cmÕ1) from the expected value of 1350 cmÕ1 for
[Ni(dmit)2]Õ. This suggests that the formal charge of [Ni-
(dmit)2] anions in I, II, and III has shifted to less negative
values. In the case of IV, the spectra has the expected C=C
stretching band at 1353 cmÕ1, indicating that [Ni(dmit)2] anion
in IV has a formal charge of Õ1.12
Molecular Structures.
ORTEP plots with the atomic
numbering scheme of the four molecules 1, 2, 3, and 4 are
given in Figure 1. The crystals of I, II, and III include one
crystallographically independent 1 and one counter cation
within the asymmetric units. There are no significant geo-
metrical differences in the structures of 1 among these crystals.
The structures of 1 in the salts are almost planar within
0.0856(11), 0.0598(17), and 0.0424(10) ¡ for I, II, and III,
Chart 1.
Table 1. Crystallographic Data of Complex Salts I, II, and III
I
II
III
Formula
FW
C11H8NNiS11
565.55
C12H10NNiS11
579.58
C12H10NNiS11
579.58
Crystal system
Space group
Triclinic
ꢀ
P1
Triclinic
ꢀ
P1
Triclinic
ꢀ
P1
a/¡
b/¡
c/¡
¡/°
¢/°
£/°
V/¡3
8.7476(6)
9.5979(6)
12.8223(8)
77.5520(10)
86.4570(10)
75.4880(10)
1017.66(11)
2
7.8987(11)
10.5342(15)
13.4853(19)
71.029(2)
82.029(2)
78.393(2)
1036.2(3)
2
7.9774(7)
10.5219(9)
13.2822(11)
71.6350(10)
80.880(2)
77.708(2)
1028.80(15)
2
Z
DX/Mg mÕ3
1.846
2.078
1.858
2.043
1.871
2.058
®/mmÕ1
S
1.07
0.033
0.097
Õ0.68, 0.41
1.02
0.046
0.134
Õ0.68, 1.01
2 2 1/2
0.92
0.034
0.092
Õ0.44, 0.36
R(F)a) [refs. I > 2·(I)]
wR(F2)b) [refs. I > 2·(I)]
ŵmin,max/e ¡Õ3
a) R(F) = ÊËËFoË Õ ËFcËË/ÊËFoË. b) wR(F2) = Ê[w(Fo2 Õ Fc ) ]/Ê[w(Fo ) ]
.
2 2

354
Bull. Chem. Soc. Jpn. Vol. 82, No. 3 (2009)
Highly Conductive [Ni(dmit)2] Complex Salts
Figure 1. ORTEP views of 1, 2, 3, and 4 showing 50%
probability ellipsoids and the atom-numbering scheme.
Figure 3. Crystal structure of I, showing honeycomb
structure in the (001) plane, viewed along the molecular
axis of 1. S£S interactions are shown by dashed lines.
Figure 2. Stacking of 1 and 2 in I; (a) side view and (b) top
view.
respectively. In these crystals, the NiÍS distances range from
2.1504(11) to 2.1731(19) ¡, with an average of 2.160 ¡, and
the cis-SÍNiÍS angles range from 85.76(3) to 93.43(3)°; the
NiS4 coordination thus adopts a slightly distorted square-planar
configuration. The coordinated dmit ligands are coplanar with
each other; the dihedral angles between them are 2.04(5),
0.74(7), and 0.30(6)° for I, II, and III, respectively. The
dihedral angles between the thiazole ring of the cations and
the molecular plane of the anions are 4.38(14), 1.51(19), and
1.24(18)° for I, II, and III, respectively. The thiazole rings are
almost planar within 0.0059(16), 0.0060(23), and 0.0043(19) ¡
for I, II, and III, respectively, and the carbons of the methyl
groups on the thiazole rings are also on the thiazole plane
within 0.035(5) [C10] and 0.025(6) ¡ [C11] for I, 0.001(7)
[C10], 0.023(7) [C11], and 0.029(7) ¡ [C12] for II, and
0.024(5) [C10], 0.003(6) [C11], and 0.046(6) ¡ [C12] for III.
The double bond lengths (N1ÍC7 and C8ÍC9) in the thiazole
ring are 1.362(5) and 1.329(5) ¡ for I, 1.321(6) and 1.461(5) ¡
for II, 1.342(4) and 1.351(5) ¡ for III, respectively.
Figure 4. Three sheets of honeycomb structures stacked
along the c axis with the translational symmetries.
(C1ÍC2ÍS4ÍC3ÍS3) and thiazole rings (N1ÍC8ÍC9ÍS11ÍC7)
were approximately 3.851 and 3.768 ¡, which are enough
to close to form four ³Í³ interactions.13 These anions are
arranged into a hexagonal structure in the (001) plane.
Neighboring hexagons are joined together with sharing of all
edges to form a honeycomb sheet structure (Figure 3). The
sheets of the honeycomb structures are arranged along the c
axis with the translational symmetries producing the columnar
honeycomb structures, which have straight channels along
ꢀ ꢀ
the [111] direction (Figure 4). The cations are placed in the
channels. This columnar honeycomb structure is regulated by
many S£S interactions. The S£S distances shorter than 3.70 ¡,
the sum of the van der Waals radii of S atoms, are listed in
Table 2. In addition, two CÍH£S and four ³Í³ interactions
between cations and anions are also close enough to contribute
to the honeycomb columnar structures (Table 3).
Crystal Structure of I. The crystal contained a crystallo-
graphically independent pair of 1 and 2. These two anions
sandwiched the cations (Figure 2a); the molecules of 2 stacked
on the dmit moieties with alignment of the molecular shapes
(Figure 2b). The distances between the centroids of the dmit
Crystal Structures of Isostructural II and III.
The
molecules of 3 and 4 are structural isomers of each other (see
Figure 1), and exhibit isostructural crystal packing. As shown
in Figures 5a and 5c, two anions sandwiched two cations in II

E. Tomiyama et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 3 (2009)
355
and III. Figures 5b and 5d show that the relative orientations
between the anions and cations are almost the same in each
crystal: three methyl groups and a sulfur atom (S11) occupy the
same positions. A slight difference is the location of each N1
atom. The distances between the centroids of the dmit (C1ÍC2Í
S4ÍC3ÍS3) and thiazole rings (N1ÍC8ÍC9ÍS11ÍC7) are about
3.643 and 4.531 ¡ in II and 3.631 and 4.499 ¡ in III. In
contrast to I, overlaps of thiazole rings with dmit are small.
These anions are arranged to form the hexagonal structure.
Neighboring hexagons are joined together with sharing of all
edges to form a honeycomb sheet structure in the (001) plane
(Figures 6a and 6d) as in I. The sheets are stacked along the c
axis by the translational symmetries (Figures 6b and 6e). The
relative position of the stacked sheets is slightly dislocated,
thus zigzag channels are formed in II and III (Figures 6c and
6f). The honeycomb structures are regulated by many S£S
interactions. The corresponding S£S distances are listed in
Table 4. In addition, two CÍH£S and two ³Í³ interactions are
found between cations and anions (Table 5).
Electrical Conductivities. The values of the conductivities
in the (001) planes were 0.20, 0.094, and 0.16 S cmÕ1 for I, II,
and III, respectively. These conductivities of I, II, and III are
unexpectedly high among the series of Z[Ni(dmit)2] of 1:1
complexes. In the crystal structures of I, II, III, and IV similar
honeycomb sheet structures are formed in the (001) plane. The
high conductivities of I, II, and III suggest that the honeycomb
sheets may contribute to the conduction pathways. However, as
reported previously the electrical conductivity of IV was
Table 4. Distances/¡ of S£S Interactions in II and III
II
III
S1£S1a)
S1£S3a)
S2£S9b)
S3£S6a)
S4£S6c)
S4£S11d)
S5£S5e)
S5£S11d)
S7£S7b)
S8£S8f)
3.637(2)
3.6600(19)
3.5778(14)
3.6890(13)
3.6273(14)
3.6992(14)
3.5681(14)
3.676(2)
3.6176(15)
3.5410(17)
3.3496(18)
3.5924(17)
3.6747(16)
3.6252(16)
(3.7319(17))
3.6328(18)
(3.724(2))
3.586(2)
Table 2. Distances/¡ of S£S Interactions in I
I
S1£S7a)
S1£S8b)
S2£S2c)
S2£S4c)
S4£S7c)
S5£S10d)
S6£S6b)
S6£S8b)
S9£S10e)
3.6610(10)
3.6803(9)
3.5524(13)
3.5410(10)
3.5765(10)
3.4816(12)
3.5909(12)
3.4010(9)
3.6504(11)
3.555(2)
3.365(2)
Symmetry codes: a) Õx, Õy, 2 Õ z; b) 1 Õ x, 1 Õ y, 2 Õ z;
c) 1 Õ x, Õy, 2 Õ z; d) x, Õ1 + y, 1 + z; e) Õx, Õ1 Õ y, 3 Õ z;
f) 1 Õ x, 1 Õ y, 1 Õ z.
Table 5. Geometries of Possible CÍH£S Hydrogen Bonds
in II and III
Symmetry codes: a) 2 Õ x, Õy, 1 Õ z; b) 2 Õ x, 1 Õ y, 1 Õ z;
c) 2 Õ x, Õy, 1 Õ z; d) Õ1 + x, Õ1 + y, 1 + z; e) 2 Õ x,
1 Õ y, Õz.
DÍH£A
DÍH/¡ H£A/¡ D£A/¡ (DÍH£A)/°
II
C10ÍH10A£S1a) 0.96
C12ÍH12B£S3b) 0.96
2.97
2.98
3.694(5) 134
3.883(5) 158
Table 3. Geometries of Possible CÍH£S Hydrogen Bonds
in I
III
DÍH£A
C10ÍH10B£S1 0.96
C7ÍH7£S10a)
0.93
DÍH/¡ H£A/¡ D£A/¡
(DÍH£A)/°
3.869(4) 156
3.817(4) 154
C10ÍH10C£S3b) 0.96
C11ÍH11A£S1a) 0.96
2.94
2.91
3.787(4) 148
3.734(4) 145
2.97
2.96
Symmetry codes: a) x, 1 + y, z; b) Õx, Õy, 2 Õ z.
a) Symmetry code: Õ1 + x, y, 1 + z.
Figure 5. Stacking of 1 and 3 in II; (a) side view and (b) top view. Stacking of 1 and 4 in III; (c) side view and (d) top view.

356
Bull. Chem. Soc. Jpn. Vol. 82, No. 3 (2009)
Highly Conductive [Ni(dmit)2] Complex Salts
Figure 6. Packing motifs of II and III. (a) Sheet of honeycomb structure in the (001) plane; (b) two sheets of honeycomb structures
stacked along the c axis with the translational symmetries; (c) hexagons in the honeycomb structure shown by ball-and-stick anions
in front, and capped sticks behind for II. Figures d, e, and f correspond to those for III.
Table 6. Numbers of S£S Interactions Classified by Stack-
ing Configurations in I, II, III, and IV
I
II
III
IV
Intra-honeycomb sheet
face-to-face
side-by-side
anionÍcation
1
6
[1]a)
5
1
5
[2]a)
1 + [4]a)
2
Inter-honeycomb sheet
head-to-head
side-by-side
anionÍcation
1
1
[1]a)
1
1
1
1
1
1
a) S£S separation distance of 3.7Í3.8 ¡ (sum of the van der
Waals radii of S atoms is 3.7 ¡).
10Õ7 cmÕ1, which is not high at all,7 suggesting that the
molecular interactions in the (001) plane should be slightly
different in all four complexes. Table 6 shows the numbers of
S£S distances classified by the stacking configuration shown in
Figure 7. In the honeycomb sheet, face-to-face stackings are
attributed to the large molecular orbital transfer, and side-by-
Figure 7. Stacking configurations of anions within the
intra- and inter-honeycomb sheets.

E. Tomiyama et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 3 (2009)
357
side stackings are less effective to the conduction pathway due
to small molecular orbital transfer. The honeycomb structures
of I and III, on the other hand, have face-to-face stacking and
many side-by-side stackings; those of II have no face-to-face
stacking, but many side-by-side stackings, similar to I and III.
The distorted honeycomb sheet structure of IV had no short
face-to-face stacking, and has a small number of side-by-side
stacking. The short face-to-face and side-by-side stacking
promote regular honeycomb structures. Between honeycomb
sheets, almost the same numbers of S£S interactions exist,
and these interactions contribute to the formation of crystal
structures for all four complexes. However, the overlapping of
³-orbitals for inter-sheets S£S interactions is quite small.
These interactions do not contribute to electrical conductivity.
We believe that the regularity of the honeycomb hexagons is an
important factor in archiving high conductivities, while the
distorted honeycomb hexagons as in IV seem to favor low
conductivity. As previously mentioned, the IR spectra provide
compelling evidence that the formal charge of the anion is
shifted to less negative values, and thus shift seems to correlate
with the degree of regularity of the honeycomb hexagons.
Therefore, the partially auto-oxidized formal charge of the
[Ni(dmit)2] anion is a factor that must be taken into consid-
eration to explain the high conductivity values.
values of the electrical conductivities for I, II, and III were
0.20, 0.094, and 0.16 S cmÕ1, respectively. These high con-
ductivities may be attributed to the partial auto-oxidation of the
anions, as well as the regularity of the honeycomb sheet
structure. In the latter case, the hexagonal sheets provide a 2-D
conductivity path for the electrons, while to a lesser extent
the S£S interactions between sheets may contribute to the
conduction pathways.
Finally, these dmit salts used in this study are easily
synthesized on a large scale, and thus are attractive candidates
for molecular design of conductors in industrial applications.
The authors thank Mr. Totsuka and Prof. Furukawa for
performing the conductivity measurements.
Supporting Information
IR spectra of I, II, III, and IV, and experimental detail of
electrical conductivities. This material is available free of charge
on the Web at: http://www.csj.jp/journals/bcsj/.
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Conclusion
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4
We have prepared three 1:1 complex salts composed of
[Ni(dmit)2] anion and di- or trimethyl-substituted thiazolium
cations that have high electrical conductivities, which are
attributed to the auto-oxidation of anions and many S£S
interactions that provide a conduction pathway in the crystals.
The IR spectra confirms that the formal charge of the
[Ni(dmit)2] anion has a slight positive shift from Õ1. Our
crystallographic measurements reveal that the molecular
structures of 1 were the same in all three complex salts
studied, and furthermore in the structure of I, II, and III,
the anions were arranged to form hexagonal patterns, and
neighboring hexagons formed honeycomb sheet structures as a
result of S£S interactions. The honeycomb structures of I and
III have face-to-face stacking and many side-by-side stackings;
those of II have no face-to-face stacking, but do have many
side-by-side stackings, similar to I and III. The sheets of the
honeycomb structures in I were stacked to form a columnar
cation channel. In the honeycomb sheet structures of II and III,
the distortion of the hexagonal pattern, results in the cations
S. Moriyama, Y. Nishio, K. Kajita, W. Sasaki, Chem. Lett. 1987,
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5
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being aligned in a zig-zag pattern along [111] direction. The