Anomalous distortion and stacking column formation of [Ni(dmit) 2]- induced by propeller-shaped dye cations, crystal violet and basic fuchsin

Article abstract of DOI:10.1246/bcsj.79.1060

(CV⁺)[Ni(dmit)₂]·1/2(C₆H ₆) (1) and (BF⁺)[Ni-(dmit)₂] (2) (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato, CV⁺ = cation of Crystal Violet, BF⁺ = cation of Basic Fuchsin) were prepared and characterized by X-ray crystal structural analysis. In the crystal structure of 1, the Ni(dmit)2 unit was bent at Ni in a V shape with an angle of 13.7° and tetrahedral distortion of 8.8° around Ni was also present that originated from the steric effect of the propeller-shaped CV cation. In the case of 2, BF and [Ni(dmit)₂]^- formed an independent stacking column in which [Ni(dmit)₂]⁺ were stacked alternately rotated with an angle of 90° to each other. 1 and 2 exhibited semiconducting behavior with roomtemperature conductivities of 2:9 × 10^-7 and 9:0 × 10^-5 S cm^-1, respectively.

Full text of DOI:10.1246/bcsj.79.1060

1060 Short Articles
Bull. Chem. Soc. Jpn. Vol. 79, No. 7, 1060–1062 (2006)
Anomalous Distortion and Stacking
Column Formation of [Ni(dmit)2]À
Induced by Propeller-Shaped
Dye Cations, Crystal Violet
and Basic Fuchsin
ꢀ
and Kazuo Miyamura
Yuji Soneta, Tomoko Midorikawa,
Department of Chemistry, Faculty of Science,
Tokyo University of Science, 1-3 Kagurazaka,
Shinjuku-ku, Tokyo 162-8601
Received November 17, 2005; E-mail: j1304705@ed.kagu.tus.
ac.jp
Chart 1.
(CVþ)[Ni(dmit)2] 1/2(C6H6) (1) and (BFþ)[Ni-
ꢁ
(dmit)2] (2) (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato,
CVþ = cation of Crystal Violet, BFþ = cation of Basic
Fuchsin) were prepared and characterized by X-ray crystal
structural analysis. In the crystal structure of 1, the Ni(dmit)2
unit was bent at Ni in a V shape with an angle of 13.7ꢂ and
tetrahedral distortion of 8.8ꢂ around Ni was also present that
originated from the steric effect of the propeller-shaped CV
cation. In the case of 2, BF and [Ni(dmit)2]ꢃ formed an
independent stacking column in which [Ni(dmit)2]ꢃ were
stacked alternately rotated with an angle of 90ꢂ to each other.
1 and 2 exhibited semiconducting behavior with room-
temperature conductivities of 2:9 ꢄ 10ꢃ7 and 9:0 ꢄ 10ꢃ5
S cmꢃ1, respectively.
Fig. 1. Displacement ellipsoids of [Ni(dmit)2]ꢃ in 1 and 2
were drawn at the 50% probability level.
(cation of Crystal Violet = CVþ) and tris(4-aminophenyl)meth-
ylium (cation of Basic Fuchsin = BFþ), as the counter cations
of [Ni(dmit)2]ꢃ (Chart 1). Basic Fuchsin and Crystal Violet
have a basic structure of the triphenylcarbon group and this
structure has a large planar conjugated ꢀ system. The vibrant
colors of these dyes show potential electric and optic proper-
The metal–dithiolate complex is an excellent building block
for electronic functional materials. Seven molecular supercon-
ductors based on M(dmit)2 have been discovered.1 The counter
cations used in the molecular conductors can be closed shell
cations as well as open shell ones. However, the cations used
are mostly closed shell ones and a small number of aromatic
compounds have been employed as the counter cations. Re-
cently, Cornelissen et al. reported (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 con-
ductivity of 0.21 S cmꢃ1 compared with other monoanionic
Ni(dmit)2 complex salts.2 (MeQ)[Ni(dmit)2] (MeQ = N-meth-
ylquinolinium) was characterized by X-ray crystal structural
analysis and exhibited a conductivity of 10ꢃ3 S cmꢃ1.3 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 ꢀ-electronic
systems of both the cations and the anions might be responsi-
ble for the conductivity. In this work, we have selected tri-
phenylmethane dyes, N-[4-[bis[4-(dimethylamino)phenyl]meth-
ylene]-2,5-cyclohexadien-1-ylidene]-N-methylmethanaminium
ties. However, the crystal structure of CVþClꢃ 9H2O was
ꢁ
determined and the propeller shape of the CV cation was con-
firmed.4 Crystal Violet showed photoconductive behavior of
10ꢃ7 S cmꢃ1 in a thin solid film.5 Then, [Ni(dmit)2]ꢃ complex
salts of CVþ and BFþ were prepared and characterized by X-
ray single-crystal structural analysis and electric conductivity.
The displacement ellipsoids of [Ni(dmit)2]ꢃ in 1 with the la-
beling scheme are depicted in Fig. 1. The Ni–S bond distances
˚
were 2.1603(7)–2.1667(7) A, being in good accord with the
values found for {N(C4H9)4}[Ni(dmit)2], which was regarded
as a monoanion radical.6 The Ni(dmit)2 unit showed a large
deviation from planarity. The Ni(dmit)2 unit was bent at Ni
in a V shape with the angle of 13.7ꢂ and tetrahedral distortion
of 8.8ꢂ around Ni was also present. In the case of the complex
salt of N-methylquinolinium, the NiS4 coordination geometry
of [Ni(dmit)2]ꢃ was also bent at an angle of 5.24ꢂ and tetra-
hedral distortion of 2.14ꢂ.3 The structures of dye cations were
also distorted from planarity. Examination of molecular mod-
els revealed that the six ortho-hydrogen atoms, in Crystal Vio-
let, were subjected to steric hindrance. In order to reduce this
Published on the web July 4, 2006; doi:10.1246/bcsj.79.1060

Bull. Chem. Soc. Jpn. Vol. 79, No. 7 (2006)
Ó 2006 The Chemical Society of Japan 1061
Fig. 2. Crystal structure of 1 viewed along the a-axis. The
˚
dotted lines indicate the S–S contacts shorter than 3.7 A.
Hydrophobic interactions of cation–cation (a) and cat-
ion–anion (b and c) were found and C=S distances at c
˚
[1.644(3) A] were longer than that at b [1.632(3) A].
˚
Fig. 3. Inter-column hydrogen-bond network of 2 viewed
from different angles. The hydrogen bonds of N–H S
are represented by dotted lines.
effect, Crystal Violet adopted a propeller shape.7 In the crystal
structure of 1, the anion complexes and CV cations were piled
up alternately, which implied that the large distortion of
[Ni(dmit)2]ꢃ had originated from the steric effect of the pro-
peller-shaped CV cation shown in Fig. 2. Lueck et al. proposed
a dimer structure for the CV cation in which the dimethylami-
no groups overlapped in a head-to-tail manner suitable for
maximizing the hydrophobic interactions.8 In 1, CV cations
formed the head-to-tail dimer, but the overlap of the dimethyl-
ꢁꢁꢁ
Table 1. Parameters Hydrogen Bonds between N–H S
ꢁꢁꢁ
D–H A
ꢁꢁꢁ
d(H A)
d(D A)
= (DHA)
ꢁꢁꢁ
ꢁꢁꢁ
À
N(1)–H(1B) S(1)
ꢁꢁꢁ
2.86
2.94
3.01
3.07
3.343(3)
3.691(3)
3.427(3)
3.589(3)
117.0
147.1
112.1
120.2
N(1)–H(1B) S(1)
ꢁꢁꢁ
N(1)–H(1A) S(4)
ꢁꢁꢁ
N(2)–H(1A) S(5)
ꢁꢁꢁ
amino groups was smaller than that of CVþClꢃ 9H2O. Addi-
ꢁ
tionally, the distance of the overlapped plane between the in-
þ
ꢃ
˚
tra-dimer in 1 was 3.56 A longer than that of CV Cl 9H2O
like its shape in the crystal of a perchlorate described by
Koh et al., and intramolecular bond lengths and angles of
the BF cation represented no significant change.9 [Ni(dmit)2]ꢃ
and BFþ formed independent stacking columns along the c-
axis, similar to the case of [Ni(dmit)2]nꢃ (0 < n < 1) complex
salts, which form stacking columns. However, the structure of
the [Ni(dmit)2]ꢃ column was different. In the stacking column
of 2, [Ni(dmit)2]ꢃ were stacked alternately rotated with an
angle of 90ꢂ to each other in the columns shown in Fig. 3. This
stacking structure is similar to that observed for Ni(dpg)2I
(dpg = diphenylglyoximato), where the [Ni(dpg)2] units were
stacked alternately rotated with an angle of 90ꢂ.10 Ni(dmit)2
complex salts that contains a ꢀ-conjugated cation and in which
the cation/anion ratio is 1, usually form non-segregated stacks
with the cation and anion as 1.2,3 As shown in Fig. 3, the hy-
ꢁ
˚
(3.42 A) shown in Fig. 2a. Thus, the intra-dimer interaction
was estimated to be weak. In CVþClꢃ 9H2O, the dihedral
ꢁ
angles between aminomethyl groups and phenyl groups were
5.91 and 8.76ꢂ, respectively, while that of 1 was up to
17.96ꢂ, which was induced by the overlap with [Ni(dmit)2]ꢃ.
This hydrophobic interaction of the cation and the anion in-
˚
duced the elongation of the C=S distance [1.644(3) A], which
was longer than that without cation–anion interaction
˚
[1.632(3) A]. In 1, three different inter-anion S–S contacts,
shorter than the sum of the van der Waals radii, were found.
The pairs of [Ni(dmit)2]ꢃ combined with the distance of
˚
˚
3.544(1) A (S2–S4 [1 ꢃ x, ꢃy, ꢃz]), 3.612(1) A (S2–S6
[1 ꢃ x, ꢃy, ꢃz]) were located side by side, and the inter-pair
˚
distance was 3.642(1) A (S5–S7 [1 ꢃ x, 1 ꢃ y, ꢃz]). Thus,
anions were connected along the b-axis as shown in Fig. 2.
Since it was suggested that the orbital overlaps of anions effec-
tive for conduction were present at the side by side alignment
drogen bonds of N–H S were present at all [Ni(dmit) ]ꢃ so
ꢁꢁꢁ
2
that the columns of [Ni(dmit)2]ꢃ and BFþ were bound firmly.
The parameters were tabulated in Table 1. Since this crystal
structure was controlled by these hydrogen bonds, the [Ni-
(dmit)2]ꢃ could form an independent stacking column. The
˚
or stacking within the distance of 3.7 A, the electronic interac-
tion was estimated to be relatively strong in 1.
The displacement ellipsoids of [Ni(dmit)2]ꢃ in 2 with the
labeling scheme are depicted in Fig. 1. The Ni1–S5 bond dis-
S–S contact was also found with the distance of 3.620(2) A
(S3–S30 [ꢃx, y, 1:5 ꢃ z]).
˚
˚
tance [2.1725(9) A] was longer than those of general mono-
anionic complexes. This occurs by the contact of S5 with the
ligand center C atoms of the sandwiched [Ni(dmit)2]ꢃ anion
The electric conductivities of single crystals of 1 and 2 were
measured by the two probe method. Both complex salts exhib-
ited semiconducting behavior in the temperature range of 268
to 373 K with room-temperature conductivities of 2:9 ꢄ 10ꢃ7
and 9:0 ꢄ 10ꢃ5, respectively. In 1, the interaction between
[Ni(dmit)2]ꢃ and CVþ was found, but the electric conductivity
was not as high as expected. The reason is uncertain, but the
anomalous distortion of [Ni(dmit)2]ꢃ might be the reason for
this low conductivity. In the previous report,11 however, the
0
˚
with the distance of 3.433(3) A (S5–C2 [ꢃx, y, 1:5 ꢃ z]) and
0
˚
3.407(3) A (S5–C3 [ꢃx, y, 1:5 ꢃ z]). The conformation geom-
etry around NiS4 was essentially planar, but the dmit ligand
was bent in a V shape with the angle of 7.5ꢂ due to the hydro-
gen bond between the N–H of BFþ and the terminal S atom of
[Ni(dmit)2]ꢃ. The organic cation had a propeller shape, just

1062 Y. Soneta et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 7 (2006)
(all data) = 0.1042. For 2: C25H18N3NiS10, Mr ¼ 739:73,
crystal of the 3-(4- and 3-alkyl-pyridinium)-1,5-diphenylver-
dazyl radical cation, which was similar to the triphenylmeth-
ane dyes, with Ni(dmit)2 formed in a non-segregated manner,
and the electric conductivity of these compounds were as high
˚
˚
˚
a ¼ 16:9262ð13Þ A, b ¼ 21:7766ð17Þ A, c ¼ 7:8174ð6Þ A, V ¼
3
˚
2881:5ð4Þ A , orthorhombic, space group Pbcn, Z ¼ 4, T ¼
297(2) K, Dcalcd ¼ 1:705 Mg mꢃ3, ꢁ ¼ 1:423 mmꢃ1, 18147 reflec-
tions measured, 3329 unique (Rint ¼ 0:0817), GOF (on F2) =
0.999, final R1 (I > 2ꢆ) = 0.0423, wR2 (I > 2ꢆ) = 0.0836, R1
(all data) = 0.0832, wR2 (all data) = 0.0917. Crystallographic
data have been deposited with the Cambridge Crystallographic
Data Centre: Deposition numbers CCDC-288075 and -288074
for compounds 1 and 2, 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, UK; Fax: +44
1223 336033; e-mail: deposit@ccdc.cam.ac.uk).
as 10ꢃ3–10ꢃ6 S cmꢃ1, similar to that of 2. In (BF)[PMo12O40]
ꢁ
3H2O, an unpaired electron was generated via a charge-trans-
fer mode from the organic cation to the polyanion.12 The ꢁeff
of 2 measured with MSB-MKI (Sherwood Scientific LTD
Cambridge, England) was 1.87 (emu K molꢃ1), which was a
normal value for localized [Ni(dmit)2]ꢃ. Thus, the stacking
column structure should be responsible for the relatively high
conductivity of 2, and not the charge transfer between the cat-
ions and anions.
Experimental
References
Preparation of (CV)[Ni(dmit) ] 1/2(C H ) (1) and (BF)-
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2 Á
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[Ni(dmit)2] (2). 4,5-Bis(thiobenzoyl)-1,3-dithiole-2-thione was
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at room temperature for 20 min to give a dark red solution. To this
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ꢁ
a solution of I2 (127 mg, 1 mmol) and NaI (150 mg, 1 mmol) in
methanol (20 mL) was added. After another 10 min, a solution
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ꢁ
added to the reaction mixture. Then, the solution was stirred for
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was dissolved by a mixed hot solvent using acetonitrile and ben-
zene, and then filtered. A day after, gold block crystals of 1 were
obtained in the filtrate. 2 was synthesized by a similar way to 1
using BFþClꢃ (337 mg, 1 mmol). Green disk like crystals of 2
were obtained in the filtrate. The elemental analysis data were
performed with a Perkin-Elmer 2400II CHN Analyzer. 1: Yield,
0.21 g (25%). Anal. Found: C, 46.89; H, 3.40; N, 4.92%. Calcd
for C34H33N3NiS10: C, 47.31; H, 3.85; N, 4.87%. 2: Yield, 0.25 g
(34%). Anal. Found: C, 40.91; H, 2.91; N, 5.94%. Calcd for
C25H18N3NiS10: C, 40.59; H, 2.45; N, 5.68%.
2
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9
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˚
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˚
data for 1: C34H33N3NiS10, Mr ¼ 862:94, a ¼ 7:8380ð5Þ A,
ꢂ
˚
˚
b ¼ 12:1436ð7Þ A, c ¼ 20:8824ð12Þ A, ꢂ ¼ 106:2410ð10Þ , ꢄ ¼
ꢂ
ꢂ
3
˚
97:6650ð10Þ , ꢅ ¼ 95:1480ð10Þ , V ¼ 1874:32ð19Þ A , triclinic,
space group P1, Z ¼ 2, T ¼ 297ð2Þ K, Dcalcd ¼ 1:529 Mg mꢃ3
,
ꢀ
ꢁ ¼ 1:106 mmꢃ1, 12583 reflections measured, 8449 unique
(Rint ¼ 0:0326), GOF (on F2) = 0.846, final R1 (I > 2ꢆ) =
0.0376, wR2 (I > 2ꢆ) = 0.0909, R1 (all data) = 0.0570, wR2
for the Solution of Crystal Structures, University of Gottingen,
Germany, 1997.
¨