Ambient-pressure organic superconductors κ-(DMEDOTSeF) 2[Au(CN)4](Solv.): Tc tuning by modification of the solvent of crystallization

Article abstract of DOI:10.1002/chem.200700314

The unsymmetrical π donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)₄] ion and cyclic ethers as solvent of crystallization. The six new organic superconductors κ-(DMEDOTSeF) ₂[Au(CN)₄](Solv.) [solv. = 1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2Hpyran (DHP), or 1,4-dioxane (1,4DOX)] are classified into two subphases κ_L and κ′ according to the differen ces in their space group symmetry. κ_L(DMEDO-TSeF) ₂[Au(CN)₄](Solv.) (solv. = DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Prima, and T_c of the κ_L phase varies by 1.7-5.3 K according to the size and shape of the solvent of crystallization. On the other hand, κ′ (DMEDO-TSeF)₂[Au(CN)₄](Solv.) (solv. = DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The κ′-phase containing 1,4-DOX shows superconductivity at 4.2 K, but the κ′-phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors κ_H- and κ_L(DMEDO-TSeF)₂[Au(CN)₄](THF), revealed that the T_c of the present system is finely tunable by utilizing the effect of the solvent of crystallization.

Full text of DOI:10.1002/chem.200700314

FULL PAPER
DOI: 10.1002/chem.200700314
Ambient-Pressure Organic Super
ACHTREUNG
TSeF)2[Au(CN)4]
Crystallization**
ACHTREUNG
[a]
Takashi Shirahata,[a, b] Megumi Kibune,[a] Hiroko Yoshino,[a] andTatsuro Imakubo*
Abstract: The unsymmetrical p donor
dimethyl(ethylenedioxy)tetraselenaful-
valene (DMEDO-TSeF) has provided
six new organic superconductors with a
monovalent square-planar [Au(CN)4]ꢀ
ion and cyclic ethers as solvent of crys-
tallization.The six new organic super-
ces in their space group symmetry. kL-
(DMEDO-TSeF)2[Au(CN)4](solv.)
in the noncentrosymmetric monoclinic
space group Cc.The k’-phase contain-
ing 1,4-DOX shows superconductivity
at 4.2 K, but the k’-phase containing
DOL does not show superconductivity
down to 1.4 K. Systematic investigation
of the six new organic superconductors,
together with the two previously re-
ported superconductors kH- and kL-
AHCTREUNG
(solv.=DOL, DHF, THP, 1,3-DOX or
DHP) crystallizes in the orthorhombic
space group Pnma, and Tc of the kL
phase varies by 1.7–5.3 K according to
the size and shape of the solvent of
crystallization.On the other hand, k’-
conductors
TSeF)2[Au(CN)4]
oxolane (DOL),
k-(DMEDO-
A
(DMEDO-TSeF)2[Au(CN)4]
A
2,5-dihydrofuran
(solv.=DOL or 1,4-DOX) crystallizes
(DMEDO-TSeF)2[Au(CN)4](THF), re-
N
(DHF), tetrahydropyran (THP), 1,3-di-
oxane (1,3-DOX), 3,4-dihydro-2H-
pyran (DHP), or 1,4-dioxane (1,4-
DOX)] are classified into two subphas-
es kL and k’ according to the differen-
vealed that the Tc of the present
system is finely tunable by utilizing the
effect of the solvent of crystallization.
Keywords: fulvalenes
bonds · solvent effects · supercon-
ductors · supramolecular chemistry
· hydrogen
ꢀ
Introduction
ed for the PF6 salt of ethylenedioxytetrathiafulvalene
(EDO-TTF), which is a hybrid of BO and pristine TTF.[4] In
spite of these successful results on TTF derivatives, there
are few reports on tetraselenafulvalene (TSeF) derivatives
bearing a ethylenedioxy group because of difficulties in syn-
thesis.Recently, we reported the safe synthesis of bis(ethyle-
nedioxy)tetraselenafulvalene (BEDO-TSeF)[5] and dimethyl-
Among the large number of substituents on organic p
donors based on tetrathiafulvalene (TTF), the ethylenedioxy
group gives characteristic features such as high solubility in
common organic solvents and the ability to construct
CH···O hydrogen bonds.[1] The symmetrical derivative bis(e-
thylenedioxy)tetrathiafulvalene (BEDO-TTF or BO)[2] has
provided various organic metals containing two organic su-
perconductors,[3] and a giant photoresponse has been report-
A
promising p donors containing the ethylenedioxy group for
the development of organic metals and superconductors
without the use of highly hazardous CSe2.The latter mole-
cule DMEDO-TSeF is the hybrid of tetramethyltetraselena-
fulvalene (TMTSF)[7] and BEDO-TSeF, and it is also the
chalcogen analogue of dimethyl(ethylenedithio)diselenadi-
thiafulvalene (DMET), which provided the first organic su-
perconductor based on an unsymmetrical organic p donor.[8]
We began research on the cation radical salts of DMEDO-
[a] Dr.T.Shirahata, M.Kibune, H.Yoshino, Dr.T.Imakubo
Imakubo Initiative Research Unit, RIKEN
2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)
Fax : (+81)48-467-8790
E-mail: imakubo@riken.jp
[b] Dr.T.Shirahata
ꢀ
ꢀ
ꢀ [6]
Current address:
TSeF with the octahedral anions PF6 , AsF6 , and SbF6 .
The donor packing motifs (so-called b-type) and quasi-one-
dimensional electronic band structures of these three salts
are similar to those of the first organic superconductor
(TMTSF)2PF6,[9] but unfortunately no sign of superconduc-
tivity was observed.In the search for new organic supercon-
Department of Chemistry and Materials Science
Tokyo Institute of Technology
O-okayama, Tokyo 152-8552 (Japan)
[**] DMEDO-TSeF=dimethyl(ethylenedioxy)tetraselenafulvalene.
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
Chem. Eur. J. 2007, 13, 7619 – 7630
ꢀ 2007 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
7619

ductors based on DMEDO-TSeF, we have tried counter
anions with a variety of sizes and shapes and focused on
monovalent square-planar organometallic anions, which
have provided unique organic superconductors such as q-
(DIETS)2[Au(CN)4] (DIETS=diiodo(ethylenedithio)disele-
and single crystals of neutral DMEDO-TSeF were grown by
slow evaporation of a CS2/n-hexane solution at room tem-
[6]
perature.X-ray structure analysis was performed at 293
and 150 K, and crystal data are summarized in Table 1.As
nadithiafulvalene)[10] and k-(BEDT-TTF)2[M
(CF3)4](1,1,2-
A
Table 1.Crystal data for neutral DMEDO-TSeF.
trichloroethane) (BEDT-TTF=bis(ethylenedithio)tetrathia-
fulvalene; M=Cu, Ag, and Au).[11] The former shows super-
conductivity under uniaxial strain applied along the I···N
bond, and the latter form two superconducting subphases
(kH and kL), whereby the insulating layer in the kL-phase is
much thicker than those of common organic superconduc-
tors.Inspired by these successful results, we introduced the
[Au(CN)4]ꢀ ion into the DMEDO-TSeF system and report-
ed two new ambient-pressure organic superconductors: kH-
T [K]
293[a]
150
formula
formula weight
crystal system
space group
a [Š]
C10H10O2Se4
478.02
C10H10O2Se4
478.02
monoclinic
P21/c (no.14)
13.930(4)
8.267(2)
11.842(3)
109.470(6)
1285.8(6)
4
2.469
11.394
3228
2210
154
0.0502
1.040
0.0460, 0.1057
0.0753, 0.1173
monoclinic
P21/c (no.14)
13.868(3)
8.3621(16)
11.462(2)
110.379(4)
1246.0(4)
4
2.548
11.758
3088
2617
147
0.0331
1.054
0.0315, 0.0916
0.0391, 0.0956
b [Š]
c [Š]
b [8]
V [Š3]
and kL-(DMEDO-TSeF)2[Au(CN)4](THF) (1: kH-phase; 2:
A
Z
1calcd [gcmꢀ3
]
kL-phase).[12] Twenty-five years after TMTSF, DMEDO-
TSeF is the second example of a sulfur-free donor providing
a bulk organic superconductor.[13] It is well-known that Tc of
an organic superconductor is sensitive to small structural
changes in counter anions and/or solvent of crystalliza-
tion,[11,14] and from this point of view the above two
DMEDO-TSeF-based organic superconductors seem to be
suitable candidates for Tc tuning by modification of the sol-
vent of crystallization.Furthermore, the high solubility of
DMEDO-TSeF in common organic solvents is also advanta-
geous for preparing the cation radical salts.Here we report
on the synthesis, crystal structures, and physical properties
m [mmꢀ1
]
independent reflections
observed reflections [I>2s(I)]
variable parameters
Rint
GOF
R1, wR2 [I>2s(I)]
R1, wR2 (all data)
[a] Reflection data for reference[6] were reanalyzed and the disorder
model for the ethylene bridge was improved.
shown in Figure 1, the 4,5-dimethyl-1,3-diselenole unit de-
rived from TMTSF is almost planar except for the hydrogen
atoms of the methyl groups.On the other hand, the 1,3-dise-
lenole ring of the 4,5-ethylenedioxy-1,3-diselenole unit de-
rived from BEDO-TSeF is bent, and the folding angle in-
creases at low temperature, from 18.98 at 293 K to 20.28 at
150 K.The disorder of the ethylene bridge observed at
room temperature has disappeared at 150 K.DMEDO-
TSeF shows two reversible redox waves, and the electro-
chemical properties of DMEDO-TSeF lie midway between
those of the parent molecules TMTSF and BEDO-TSeF.[6]
of
a
series of cation radical salts kL-(DMEDO-
(solv.) [solv.= 1,3-dioxolane (DOL) (3),
TSeF)2[Au(CN)4]
ACHTREUNG
2,5-dihydrofuran (DHF) (4), tetrahydropyran (THP) (5),
1,3-dioxane (1,3-DOX) (6), or 3,4-dihydro-2H-pyran (DHP)
(7)] and k’-(DMEDO-TSeF)2[Au(CN)4](solv.) [solv.=DOL
A
(8) or 1,4-dioxane (1,4-DOX) (9)] including six new ambi-
ent-pressure organic superconductors, comparison with the
parent superconductors 1 and 2, and experimental details of
the synthesis of DMEDO-TSeF.
Preparation of cation-radical salts: Single crystals of the
[Au(CN)4]ꢀ salts of DMEDO-TSeF were prepared by galva-
nostatic oxidation of a solution of the corresponding cyclic
ether (DOL, DHF, THP, 1,3-DOX, DHP, or 1,4-DOX) con-
taining DMEDO-TSeF and tetrabutylammonium tetracya-
noaurate as supporting electrolyte.These new salts crystal-
lize in the so-called k-type structure and are classified into
kL- and k’-subphases according to their space-group symme-
try.Electrochemical crystallization in DOL afforded two
Results andDiscussion
Donor synthesis: Neutral DMEDO-TSeF was synthesized
by cross-coupling of the corresponding 1,3-diselenole-2-se-
lones 10 and 11 according to the literature,[6] (Scheme 1)
phases kL- and k’-(DMEDO-TSeF)2[Au(CN)4](DOL) (3: kL-
A
phase; 8: k’-phase).Salt 3 is isostructural with kL-phase salt
2,[12] whereas salt 8 crystallizes in the monoclinic Cc space
Scheme 1.Synthesis of DMEDO-TSeF.
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Ambient-Pressure Organic Superconductors
FULL PAPER
1,3-DOX (6), DHP (7), or 1,4-DOX (9) crystallize in a
single phase.Salts 4–7 belong to the kL-phase, and salt 9 be-
longs to the k’-phase.
kL-(DMEDO-TSeF)2[Au(CN)4](solv.): X-ray structure anal-
A
yses for the five new cation-radical salts of the kL-phase con-
taining DOL (3), DHF (4), THP (5), 1,3-DOX (6), or DHP
(7) as solvent of crystallization were performed at 293 and
150 K.They are isostructural with 2[12] and crystallize in the
orthorhombic space group Pnma (Tables 2 and 3).The
donor/anion/solvent ratios of these five salts are 2:1:1; the
ratios and the nature of the solvent of crystallization were
1
confirmed by elemental analyses and H NMR spectroscopy,
respectively.The molecular packing motif of 6 at 293 K is
shown in Figure 2 as a representative of the kL-phase salts.
The crystallographically equivalent Layers A and A’ are
separated by thick insulating layers (ca. 4.5–5.0 Š at 293 K,
see Tables 2 and 3) composed of [Au(CN)4]ꢀ anions and sol-
vent of crystallization.[16] Many CH···N hydrogen bonds
[15]
shorter than 2.75 Š exist between the donor molecule and
the [Au(CN)4]ꢀ anion.The ethylene bridges of the donor
molecules in 5, 6, and 7 show ordered conformations at
293 K, in contrast to those of 3 and 4, which are disordered
due to flipping, as well as 2 (Figure 3).Fractions of the
major orientation increase to 80(2)% for 3 and 82(2)% for
4 at 150 K, but the disorder still persists (Table 4).Differen-
ces in the conformations of the ethylene bridges are related
to the size of the solvent of crystallization, that is, salts 2–4
contain five-membered cyclic molecules, and salts 5–7 con-
tain six-membered cyclic molecules.The smaller solvent of
crystallization gives more clearance around the boundary of
the layers and makes it easier for the ethylene bridges of
the donor molecules to flip.
Figure 1.Molecular structures for DMEDO-TSeF at a) 293 K and
b) 150 K: Top view (left), side view (center) and conformation of the eth-
ylene group (right).Gray atoms and bonds represent minor orientation
of the disordered ethylene bridge.c) Molecular packing motif at 150 K
viewed along the crystallographic b axis.Dotted lines indicate CH···O
contacts shorter than 2.72 Š.[15]
group.Salts 3 and 8 cannot be distinguished by their crystal
shape but can be identified by X-ray diffraction analysis, as
in the case of salts 1 (kH-phase) and 2 (kL-phase), which si-
multaneously grow from THF solution.[12] On the other
hand, the cation radical salts containing DHF (4), THP (5),
Table 2.Crystal data and transition temperature Tc(onset) for kL-phases 2–4.
G
Compound (solv.)
2 (THF)[a]
3 (DOL)
4 (DHF)
T [K]
293
293
150
293
150
formula
formula weight
crystal system
space group
a [Š]
C28H28AuN4O5Se8
1329.19
orthorhombic
Pnma (no.62)
8.3269(13)
38.638(6)
11.1203(17)
3577.8(9)
4
C27H26AuN4O6Se8
1331.16
C27H26AuN4O6Se8
1331.16
orthorhombic
Pnma (no.62)
8.2253(17)
38.307(8)
10.926(2)
3442.6(12)
4
C28H26AuN4O5Se8
1327.17
C28H26AuN4O5Se8
1327.17
orthorhombic
Pnma (no.62)
8.2241(13)
38.277(6)
10.9849(17)
3458.0(9)
4
orthorhombic
Pnma (no.62)
8.2783(13)
38.465(6)
11.0850(16)
3529.7(9)
4
orthorhombic
Pnma (no.62)
8.2770(12)
38.518(5)
11.1487(16)
3554.3(9)
4
b [Š]
c [Š]
V [Š3]
Z
1calcd [gcmꢀ3
]
2.468
12.294
2.505
12.463
2.568
12.779
2.480
12.375
2.549
12.720
m [mmꢀ1
]
independent reflections
observed reflections [I>2s(I)]
variable parameters
Rint
4572
2877
275
0.1050
4489
2916
275
0.1061
4406
3499
220
0.1002
4552
2626
274
0.1339
4382
3079
274
0.1129
GOF
0.967
0.966
1.175
0.933
1.097
R1, wR2 [I > 2s(I)]
R1, wR2 (all data)
thickness of insulating layer [Š]
Tc [K]
0.0492, 0.1273
0.0806, 0.1369
4.9
0.0426, 0.1082
0.0708, 0.1229
4.5
0.0511, 0.1267
0.0664, 0.1377
4.3
0.0536, 0.1354
0.0963, 0.1473
4.6
0.0590, 0.1549
0.0874, 0.1647
4.4
3.0
1.7
4.2
[a] From reference [12].
Chem. Eur. J. 2007, 13, 7619 – 7630
ꢀ 2007 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
www.chemeurj.org
7621

T.Imakubo et al.
Table 3.Crystal data and transition temperature Tc (onset) for kL-phases 5–7.
Compound (solv.)
5 (THP)
6 (1,3-DOX)
7 (DHP)
150
T [K]
293
150
293
150
293
formula
formula weight
crystal system
space group
a [Š]
C29H30AuN4O5Se8 C29H30AuN4O5Se8 C28H28AuN4O6Se8 C28H28AuN4O6Se8 C29H28AuN4O5Se8 C29H28AuN4O5Se8
1343.22
1343.22
orthorhombic
Pnma (no.62)
8.2714(13)
38.714(6)
11.0576(18)
3540.8(10)
4
1345.19
orthorhombic
Pnma (no.62)
8.3693(11)
38.799(5)
11.0377(15)
3584.2(8)
4
1345.19
orthorhombic
Pnma (no.62)
8.3224(12)
38.607(6)
10.8655(16)
3491.1(9)
4
1341.20
orthorhombic
Pnma (no.62)
8.3980(12)
39.000(5)
11.0472(16)
3618.2(9)
4
1341.20
orthorhombic
Pnma (no.62)
8.3442(13)
38.825(6)
10.8534(17)
3516.1(9)
4
orthorhombic
Pnma (no.62)
8.3630(11)
38.892(5)
11.2433(15)
3656.9(8)
4
b [Š]
c [Š]
V [Š3]
Z
1calcd [gcmꢀ3
]
2.440
2.520
2.493
2.559
2.462
2.534
m [mmꢀ1
]
12.029
12.423
12.275
12.603
12.158
12.511
independent reflections
observed reflections [I>2s(I)]
variable parameters
Rint
4610
2620
237
0.1574
4462
3553
237
0.0923
4597
2882
219
0.1198
4454
3569
219
0.0910
4663
2847
237
0.1031
4520
3359
237
0.1260
GOF
0.884
1.150
0.932
1.029
0.948
1.122
R1, wR2 [I>2s(I)]
R1, wR2 (all data)
thickness of insulating layer [Š] 4.9
0.0602, 0.1461
0.1015, 0.1574
0.0952, 0.2505
0.1110, 0.2578
4.8
0.0450, 0.1071
0.0802, 0.1148
4.9
0.0396, 0.0962
0.0532, 0.0997
4.7
0.0477, 0.1196
0.0811, 0.1270
5.0
0.0629, 0.1631
0.0867, 0.1751
4.8
Tc [K]
4.5
2.6
5.3
Figure 4a shows molecular arrangements of the conduct-
ing donor layer for 3 as a representative of the kL-phase
salts.The head-to-tail dimers are arranged orthogonally, and
Figure 2.Molecular packing motif for 6 at 293 K.Dotted lines indicate
CH···N contacts shorter than 2.75 Š.
Figure 4.a) Donor arrangement of 3 at 293 K viewed along the crystallo-
graphic b axis.Dotted lines indicate CH···O contacts shorter than 27. 2 Š.
The minor orientations of the disordered ethylene bridge of the donor
molecule are omitted for clarity.b) Crystal structure of the insulating
layer for 3 at 293 K projected onto the ac plane.Red and green indicate
configurations A and B of the disordered DOL molecules, respectively
(positions generated by the mirror symmetry operation are omitted for
clarity).
Figure 3.Conformations of the ethylenedioxy group of DMEDO-TSeF
for 2–7 at 293 K.Gray atoms and bonds in 2–4 represent the minor orien-
tations of the disordered ethylene bridge.
the donor arrangement within the donor layer is of the so-
called k-type.The CH···O hydrogen bonds are constructed
along the interaction p and run along the a axis.The solvent
of crystallization is located in cavities formed by the herring-
bone-type arrangement of anions (Figure 4b).The molecu-
lar arrangements of the donor layer for the other kL-phase
salts are the same as that of 3, but there are marked differ-
ences in the configuration of the solvent of crystallization
among the kL-phase salts.In salt 3, configurations A (60%)
and B (40%) of the DOL molecule, which are represented
by red and green in Figure 4b, are located in the general po-
sition around the mirror plane.Therefore, extreme disorder
Table 4.Distributions of two orientations of disordered ethylene bridges.
Compound (solv.)
T [K]
Major [%]
Minor [%]
2 (THF)[a]
3 (DOL)
293
293
150
293
150
74(2)
69(2)
80(2)
70(2)
82(2)
26(2)
31(2)
20(2)
30(2)
18(2)
4 (DHF)
[a] From reference [12].
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Chem. Eur. J. 2007, 13, 7619 – 7630

Ambient-Pressure Organic Superconductors
FULL PAPER
due to the 2”2=4 conformations is observed at 293 K
(Figure 5, top left), as well as for the THF molecules in 2.[12]
Similar complicated disorder of the solvent of crystallization
ieve the ordered configuration for DHF and THP, the
mirror planes of the molecules must be congruent with the
mirror plane of the crystal; at least the oxygen atom must
lie in the mirror plane.However, such an arrangement is
disadvantageous in view of the larger steric repulsion of the
hydrogen atoms between the solvent of crystallization and
donor molecules along the crystallographic b axis compared
with formation of CH···O hydrogen bonds.
Temperature-dependent resistivity of salts 2–7, measured
perpendicular to the conducting ac plane, are shown in
Figure 6.Broad maxima around 100 K, which resemble
those of the k-type BEDT-TTF salts,[11,17] were observed
except for salt 3, and a distinct resistivity drop at the super-
conducting transition was observed at Tc(onset)=3.0 K for
G
2, 4.2 K for 4, 4.5 K for 5, 2.6 K for 6, and 5.3 K for 7.Al-
though a resistivity drop of salt 3, which seems to indicate
superconducting transition, was also observed at 1.7 K for
several crystals with reliable reproducibility, complete super-
conductivity of 3 has not been confirmed due to its low tran-
sition temperature and the cooling limit of the measurement
apparatus.It is well known that the broad maximum of re-
sistivity in the high-temperature range and the supercon-
ducting transition of the k-type salts are simultaneously sup-
pressed under applied pressure.[11,18] The DOL molecule is
the smallest among the solvents of crystallization of the six
kL salts, and no resistivity maximum was observed for 3.
Therefore, the effect of chemical pressure may be intrinsic
to 3, and the superconducting transition is suppressed below
2 K.Superconductivity of 2, 4, 5, 6, and 7 was also con-
firmed by magnetic susceptibility measurements (Figure 7).
The onset temperatures of the diamagnetic transitions are
2.8 K for 2, 4.0 K for 4, 4.5 K for 5, 2.5 K for 6, and 5.0 K
for 7, respectively.The volume fraction of superconductivity
at 1.9 K is about 25, 80, 30, 10, and 20% of the perfect dia-
magnetism for 2, 4, 5, 6, and 7, respectively, and all these
salts are bulk organic superconductors.
Figure 5.Molecular structures of the solvent of crystallization viewed
along the crystallographic c axis.Dotted lines indicate mirror planes par-
allel to the ac plane.
is also observed in 4 and the ratio of configurations A and B
is 50:50.The existence of the two configurations for the sol-
vent of crystallization in salts 2–4 seems to be related to the
size of the five-membered cyclic molecules, which are small-
er than the cavities formed by the [Au(CN)4]ꢀ ion.On the
other hand, the mode of disorder is simpler for the salts in-
cluding six-membered cyclic molecules.The disorder of the
solvent of crystallization in salts 5 and 7 is based on only
one asymmetric unit, and only positional disorder induced
by the mirror symmetry operation is observed.Furthermore,
the 1,3-DOX molecule in salt 6 shows ordered configuration
at 293 K and it is consistent with the mirror symmetry of the
1,3-DOX molecule itself.The five-membered cyclic mole-
cule DOL also has mirror symmetry, and the ordered con-
figuration is observed at 150 K.
The relationship between the cell volume at 293 K and Tc
(onset) for salts 2–7 is shown in Figure 8.The Tc for salt 2 is
lower than that of salt 5, and the structural difference be-
tween 2 and 5 is the ring size of the solvent of crystalliza-
tion.Salt 2 contains five-membered cyclic THF, whereas salt
5 contains six-membered cyclic THP.A similar relationship
between Tc and the number of the ring atoms in the solvent
of crystallization is observed between 3/6 and 4/7, and it is
consistent with the chemical-pressure effect caused by the
size of the solvent of crystallization.
The Tc values for salts 2, 3, 5, and 6 depend in a roughly
linear fashion on cell volume, and those of salts 4 and 7 de-
viate from this linearity.These correlations suggest some ad-
ditional effects on Tc of salts 4 and 7 apart from the ring
size of the solvent of crystallization.The cell volumes of
salts 4 and 7 are smaller than those of salts 2 and 5, and this
is consistent with the smaller size of the DHF and DHP
molecules, which include a C=C double bond in the molecu-
lar skeleton.However, the c axis of salt 4 and the a axis of
the salt 7 are longer than those of salts 2 and 5, respectively
(see Tables 2 and 3).The effect of the anisotropic changes in
The DHF and THP molecules have mirror symmetry, as
do the 1,3-DOX and DOL molecules, but the disorder of
the DHF and THP molecules still remains at 150 K.The
ratio of configurations A and B of the DHF molecule is
20:80, and positional disorder induced by the mirror symme-
try operation is inevitable for both DHF and THP.To ach-
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T.Imakubo et al.
Figure 6.Temperature dependence of resistivity for a) 2–4 and b) 5–7, measured perpendicular to the conducting ac plane.c) and d) show temperature
dependence of the normalized resistivity in the low-temperature region for 2–4 and 5–7, respectively.
Figure 7.Temperature dependence of zero-field cooled (ZFC, closed circle) and field-cooled (FC, open circle) dc magnetization for a) 2, 4 and b) 5–7 in
an applied field of 10 Oe.
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Ambient-Pressure Organic Superconductors
FULL PAPER
[a]
Table 5.Calculated overlap integrals
(”10ꢀ3) for 2 on the basis of the
structure at 293 K[b] and 3–7 on the basis of the structure at 293 and
150 K.
Compound (solv.)
T [K]
b1
b2
ꢀ9.32
p
q
jb2/qj
2 (THF)
3 (DOL)
293
293
150
293
150
293
150
293
150
293
150
ꢀ20.63
ꢀ20.32
ꢀ21.87
ꢀ19.95
ꢀ21.75
ꢀ20.87
ꢀ23.31
ꢀ21.73
ꢀ23.02
ꢀ22.04
ꢀ23.75
0.21
0.37
0.75
0.09
0.39
0.30
0.45
0.53
1.00
0.67
1.05
4.25
4.16
4.32
4.15
4.34
3.94
4.35
4.16
4.08
4.24
4.25
2.19
2.37
2.42
2.36
2.36
2.34
2.35
2.17
2.29
2.08
2.17
ꢀ9.85
ꢀ10.47
ꢀ9.80
ꢀ10.24
ꢀ9.22
ꢀ10.21
ꢀ9.04
ꢀ9.33
ꢀ8.81
ꢀ9.23
4 (DHF)
5 (THP)
6 (1,3-DOX)
7 (DHP)
[a] See Figure 4a for definition of the overlap integrals.[b] From refer-
ence [12].
due to strong dimerization, are degenerate on the zone
boundary (Figure 9a).As shown in Figure 9b, the calculated
Fermi surfaces for the salts of kL-phases 2–7 are in the range
from opened quasi-two-dimensional to closed two-dimen-
sional.The overlap integrals b2 and q connect adjacent
dimers along the a and c axes, respectively, and it has been
reported that the degree of two-dimensionality can be esti-
mated by the ratio of these two interdimer overlap inte-
grals.[25] Indeed, the jb2/qj value of 7, which shows the high-
est Tc, is the smallest (2.08 at 293 K) among the six kL salts
and it suggests the strongest two-dimensional character.
However, there is no general consistency between Tc and
the dimensionality of the calculated Fermi surfaces through-
out the six kL salts.To explain each contradiction between
Tc and the dimensionality of the calculated Fermi surfaces,
experimental information on the Fermi surfaces and optimi-
zation of the Hückel parameters of O and Se atoms for
DMEDO-TSeF are required.[26]
3
Figure 8.Relationship between cell volume V [Š at 293 K] and the Tc-
(onset) [K] for 2–7.The onset temperature of the resistivity drop for 3 is
used as the Tc indicating superconductivity.
ACHTREUNG
the shape of the solvent of crystallization, which corre-
sponds to the anisotropic chemical-pressure effect for salts 4
and 7, seems to be one of the origins of the deviation from
the linear relationship between the Tc and cell volume.The
effect of the anisotropic pressure on superconductivity of or-
ganic superconductors has already been reported for the
uniaxial strain dependence of Tc of k-type superconduc-
tors.[19,20] For example, the increase in Tc for k-(BEDT-
TTF)2Cu2(CN)3, in which the conducting donor layer is
formed along the bc plane,[21] was observed by applying uni-
axial strain independently along the b and c axes.[19]
Another interesting feature of the new series of organic
superconductors is the thickness of the insulating layer (ca.
4.5–5.0 Š at 293 K),[16] which completely separates the con-
ducting donor layers.The transition temperatures of 2–7 are
relatively high compared with those of the known k-type su-
perconductors based on unsymmetrical p donors,[8e,22] and
the characteristic CH···N hydrogen bonds between the
donor molecule and the counter anion likely play an impor-
tant role in the superconductivity, because electron transport
through the anion layer must occur to achieve bulk super-
conductivity.It has already been reported that weak do-
nor···anion interactions sometimes influence the physical
properties in classical TMTSF and BEDT-TTF salts.[23]
k’-(DMEDO-TSeF)2[Au(CN)4](solv.): Two cation-radical
N
salts of the k’-phase containing DOL (8) or 1,4-DOX (9) as
solvent of crystallization are isostructural and crystallize in
the monoclinic space group Cc (Table 6).X-ray structure
analyses were performed at 293 K for both salts and at
150 K for 9.Low-temperature structure analysis for 8 was
also performed repeatedly at 150 K, but the structure refine-
ment for 8 did not converge because of crystal fragility, in
spite of a slow cooling rate of less than 1 Kminꢀ1.
The donor/anion/solvent ratios of 8 and 9 are 2:1:1, and
the ratios and the species of the solvents of crystallization
were confirmed by elemental analyses and 1H NMR spec-
Intermolecular overlap integrals[24] for the five new salts
3–7, calculated on the basis of the structure at 293 and
150 K, are summarized in Table 5 together with those of salt
2 at 293 K.As in the known k-type BEDT-TTF salts,[25] in-
tradimer overlap integrals b1 are considerably larger than
the interdimer overlap integrals b2.The electronic band dis-
persions and Fermi surfaces of salts 2–7 were calculated
within the tight-binding approximation by using these over-
lap integrals.Four bands are built from the HOMOs of the
donor molecules in the conducting donor layer, and the
upper and lower two bands, which are separated by a gap
troscopy, respectively.The molecular arrangement of salt
9
at 293 K viewed along the crystallographic b axis is shown in
Figure 10.There are two layers A and A ’ in the unit cell
and they are crystallographically equivalent.As in the salts
of the kL-phase, many CH···N hydrogen bonds are formed
between the donor molecule and the [Au(CN)4]ꢀ ion.
As shown in Figure 11a, the conducting donor layer con-
sists of crystallographically independent donor molecules I
and II, and the packing motif is of the so-called k-type.Mol-
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7625

T.Imakubo et al.
Figure 9.Calculated electronic band structures for kL salts at 293 and 150 K: a) Band dispersions of 3 and 6.b) Fermi surfaces of 2–7.
Table 6.Crystal data and transition temperature Tc(onset) for the k’-phases 8 and 9.
A
Compound (solv.)
8 (DOL)
9 (1,4-DOX)
T [K]
293
293
150
formula
formula weight
crystal system
space group
a [Š]
C27H26AuN4O6Se8
1331.16
monoclinic
Cc (no.9)
38.806(7)
11.112(2)
8.2431(15)
96.910(3)
3528.6(11)
4
C28H28AuN4O6Se8
1345.19
monoclinic
Cc (no.9)
38.954(7)
11.2180(19)
8.2845(14)
97.206(3)
3591.6(11)
4
C28H28AuN4O6Se8
1345.19
monoclinic
Cc (no.9)
38.802(9)
11.086(2)
8.2185(18)
97.648(4)
3503.9(13)
4
b [Š]
c [Š]
b [8]
V [Š3]
Z
1calcd [gcmꢀ3
]
2.506
12.467
2.488
12.250
2.550
12.557
m [mmꢀ1
]
independent reflections
observed reflections [I>2s(I)]
variable parameters
Rint
8806
6553
433
0.0637
8989
6962
442
0.0793
8817
7964
430
0.0582
GOF
0.960
0.910
1.009
R1, wR2 [I>2s(I)]
R1, wR2 (all data)
Flack parameter
thickness of insulating layer [Š]
Tc [K]
0.0425, 0.1014
0.0577, 0.1045
0.062(11)
4.6
0.0398, 0.0831
0.0517, 0.0983
ꢀ0.027(10)
4.6
0.0308, 0.0765
0.0345, 0.0772
ꢀ0.021(8)
4.5
[a]
–
4.2
[a] Metallic down to 1.4 K.
ecules I and II form head-to-tail dimers, and a two-dimen-
sional k-type structure is constructed in the bc plane.The
CH···O hydrogen bonds (dotted lines in the figure) are
formed between donor molecules I–I and II–II, and the net-
work runs along the c axis.The [Au(CN) ]ꢀ ions and the sol-
vent of crystallization are located on aꢁ40.15 and form thick
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Ambient-Pressure Organic Superconductors
FULL PAPER
Table 7.Distributions of two orientations of the ethylene bridges.
Compound (solv.)
T [K]
Major [%]
Minor [%]
8 (DOL)
293
molecule I
molecule II
molecule I
molecule II
molecule I
molecule II
59(2)
67(2)
67(2)
74(2)
71(1)
100
41(2)
33(2)
33(2)
26(2)
29(1)
0
9 (1,4-DOX)
293
150
Temperature dependences of the resistivity for 8 and 9
measured perpendicular to the conducting bc plane are
shown in Figure 13.A broad maximum of the resistivity
Figure 10.Molecular packing motif for 9 at 293 K.Dotted lines indicate
CH···N contacts shorter than 2.75 Š. The minor orientations of the disor-
dered ethylene bridge of the donor molecule are omitted for clarity.
Figure 11.a) Donor arrangement of 9 at 293 K viewed along the crystal-
lographic a axis with molecules I and II represented in red and green, re-
spectively.Dotted lines indicate CH···O contacts shorter than 27. 2 Š.The
minor orientations of the disordered ethylene bridge of the donor mole-
cule are omitted for clarity.b) Crystal structure of the insulating layer for
9 at 293 K, projected onto the bc plane.
insulating layers (ca. 4.5–4.6 Š, see Table 6). The solvent of
crystallization molecules, DOL in 8 and 1,4-DOX in 9, show
an ordered structure and are located in cavities formed by
the herringbone-type arrangement of anions (Figure 11b).
The ethylene bridges of molecules I and II show disorder
due to flipping (Figure 12), and distributions of the major
and minor orientations are summarized in Table 7.The eth-
ylene bridge of donor molecule II shows an ordered confor-
mation at 150 K, whereas the disorder of the ethylene
bridge of the molecule I remains at 150 K.
Figure 13.Temperature dependence of resistivity for 8 and 9 measured
perpendicular to the conducting bc plane.The inset shows the normalized
resistivity in the low-temperature region.
around 100 K was observed in salt 9, and a superconducting
transition occurred at Tc(onset)=4.2 K. On the other hand,
G
the resistivity of salt 8 monotonously decreases with lower-
ing temperature, and a superconducting transition was not
detected down to 1.4 K. The difference in conducting behav-
ior between 8 and 9 is explained by the chemical-pressure
effect, as for the kL-phase.The superconductivity of 9 was
also confirmed by magnetic susceptibility measurements
(Figure 14).The onset temperature of the diamagnetic tran-
sition is 4.2 K, which is the same as Tc(onset) in the resistivi-
G
ty measurements.The calculated volume fraction of super-
conductivity at 1.9 K is about 60% of the perfect diamagnet-
ism, that is, 9 is also a bulk organic superconductor.Most or-
ganic superconductors have an inversion center in their crys-
tal, and salt 9, which has no inversion center, is the second
noncentrosymmetric organic superconductor based on un-
symmetrical p donors after (DTEDT)3[Au(CN)2].[27]
The calculated overlap integrals on the basis of the struc-
ture at 293 K for both salts and at 150 K for 9 are listed in
Table 8.In both salts, the intradimer overlap integrals b1 are
much larger than the interdimer overlap integrals b2, p, p’,
q, and q’.Four bands are built from the HOMOs of the four
donor molecules in the primitive cell (ap =(aꢀb)/2, bp =b,
Figure 12.Conformations of the ethylenedioxy group of the crystallo-
graphically independent DMEDO-TSeF molecules I and II for 9 at
293 K and 150 K.The gray atoms and bonds represent the minor orienta-
tions of the disordered ethylene bridge.
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7627

T.Imakubo et al.
Figure 14.Temperature dependence of ZFC (closed circle) and FC (open
circle) DC magnetizations for 9 in an applied field of 10 Oe.
Figure 15.Calculated electronic band structures for k’-salt 9.a) Band dis-
persions at 293 K.b) Fermi surfaces at 293 (left) and 150 K (right).
cp =c), and they resemble those of the kL-phase salts except
for the energy gap on the zone boundary (Figure 15a).As
shown in Figure 15b, the calculated Fermi surfaces of salt 9
at 293 and 150 K are opened and those of 8 at 293 K are
almost the same.
The packing motifs of the k-(DMEDO-TSeF)2[Au(CN)4]-
A
they are further classified into kH-, kL-, and k’-subphases ac-
cording to differences in space-group symmetry.In the
[a]
Table 8.Calculated overlap integrals
(”10ꢀ3) for 8 on the basis of the
known
k-(BEDT-TTF)2M(CF3)4(1,1,2-trihaloethane)
A
structure at 293 K and for 9 on the basis of the structure at 293 and
system,[11] three subphases (kH, kL and kL’) have been report-
ed, as in the present DMEDO-TSeF salts, but the crystal
structure of the kH-phase could not be determined, and su-
perconductivity of the kL’-phase has not been confirmed.[11]
On the other hand, the crystal structures of three subphases
of the present system have been fully resolved, and distinct
differences in superconductivity have been studied for all
three subphases.The crystal structures of the DMEDO-
TSeF salts are supported by CH···O and CH···N hydrogen
bonds among the donor molecules and the counter anions,
and they are in contrast to the complicated crystal structures
of superconductors based on the parent BO molecule.[3b,c]
Recently, unconventional critical behavior was also reported
for k-type salts of BEDT-TTF,[28] and the present k-type su-
perconductors based on the new p donor DMEDO-TSeF
suggest extending the materials map of the unique phenom-
ena of the k-type salts.
The most interesting feature of the present new series of
organic superconductors is dependence of the transition
temperature of superconductivity on the solvent of crystalli-
zation.Among the six kL-type salts, the onset temperatures
of the superconductivity are sensitive to the size and shape
of the solvent of crystallization, as well as to the presence of
a C=C double bond.A size effect of the solvent of crystalli-
zation on superconductivity has been reported for the
above-mentioned BEDT-TTF system,[11e] but the effect of
shape, especially the anisotropic effect derived from the
presence of a C=C double bond in the solvent of crystalliza-
150 K.
Compound (solv.) T [K] b1
b2
ꢀ20.93 ꢀ10.04 0.28 ꢀ0.36 3.86 4.91
ꢀ19.87 ꢀ9.57 0.28 ꢀ0.61 3.58 4.48
ꢀ21.15 ꢀ10.30 0.50 ꢀ0.52 3.57 4.72
p
p’
q
q’
8 (DOL)
9 (1,4-DOX)
293
293
150
[a] See Figure 11a for definition of the overlap integrals.
Conclusion
In addition to kH- and kL-(DMEDO-TSeF)2[Au(CN)4]
(1: kH-phase; 2: kL-phase), seven cation radical salts (3–9)
have now joined the family of three-component organic
A
metals k-(DMEDO-TSeF)2[Au(CN)4](solv.) (solv.=cyclic
U
ether), and eight of them show superconductivity at ambient
pressure.The number of superconducting salts derived from
DMEDO-TSeF is the same as that of DMET, which is the
first and the largest source of organic superconductors based
on unsymmetrical p donors.[8] The Tc values of the organic
superconductors based on DMEDO-TSeF (1.7–5.3 K) are
much higher than those of DMET (0.55–1.9 K), and they
show superconductivity at ambient pressure.One of the ori-
gins of the superiority of the DMEDO-TSeF salts with
regard to superconductivity is derived from the sulfur-free
skeleton of the donor molecule, that is, the inner TSeF skel-
eton extends the electronic dimensionality and the small
ethylenedioxy group instead of the ethylenedithio group
may apply chemical pressure in the crystal.
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Ambient-Pressure Organic Superconductors
FULL PAPER
troscopy on a sonicated suspension containing dried crystals of each salt,
and the donor/anion/solvent ratios of the salts were determined by ele-
mental analysis as follows:
tion, is predominant in this family.On the other hand, the
appearance of the kH- and k’-phases enables us to determine
the structural limit of the solvent of crystallization for which
the isomorphic crystal structure of the present system is
maintained.This information on the relationship between
superconductivity and molecular structure of the solvent of
crystallization is interesting from the viewpoint of develop-
ing new organic superconductors.The design of new organic
superconductors from scratch is extremely difficult, but
tuning of Tc on the basis of modifying the solvent of crystal-
lization is in progress, and accumulation of this knowledge
will open the way to a new benchmark in organic supercon-
ductors.
Mixture of
3 and 8 (DOL): elemental analysis calcd (%) for
C27H26AuN4O6Se8: C 24.36, H 1.97, N 4.21; found: C 24.07, H 1.90, N
4.19.
4 (DHF): elemental analysis calcd (%) for C28H26AuN4O5Se8: C 25.34, H
1.97, N 4.22; found: C 25.20, H 1.95, N 4.18.
5 (THP): elemental analysis calcd (%) for C29H30AuN4O5Se8: C 25.93, H
2.25, N 4.17; found: C 25.74, H 2.26, N 4.17.
6 (1,3-DOX): elemental analysis calcd (%) for C28H28AuN4O6Se8: C
25.00, H 2.10, N 4.17; found: C 24.87, H 2.04, N 4.13.
7 (DHP): elemental analysis calcd (%) for C29H28AuN4O5Se8: C 25.97, H
2.10, N 4.18; found: C 25.63, H 2.14, N 4.19.
9 (1,4-DOX): elemental analysis calcd (%) for C28H28AuN4O6Se8: C
25.00, H 2.10, N 4.17; found: C 24.95, H 2.04, N 4.14.
X-ray crystallographic analysis: Diffraction data were collected on a
Bruker AXS SMART-APEX CCD system with graphite-monochromat-
ized MoKa radiation (l=0.71073 Š). Raw frame data were integrated
using SAINT,[30] face-indexed absorption corrections[31] were applied for
the cation-radical salts 3–9, and empirical absorption corrections using
SADABS[32] were applied for neutral DMEDO-TSeF.The structures
were solved by the direct method (SHELXS-97[33]) and refined by full-
matrix least-squares techniques on F2 (SHELXTL).[34] CCDC-637835
(DMEDO-TSeF at 293 K), CCDC-637836 (DMEDO-TSeF at 150 K),
CCDC-637837 (3 at 293 K), CCDC-637838 (3 at 150 K), CCDC-637839
(4 at 293 K), CCDC-637840 (4 at 150 K), CCDC-637841 (5 at 293 K),
CCDC-637842 (5 at 150 K), CCDC-637843 (6 at 293 K), CCDC-637844
(6 at 150 K), CCDC-637845 (7 at 293 K), CCDC-637846 (7 at 150 K),
CCDC-637847 (8), CCDC-637848 (9 at 293 K), and CCDC-637849 (9 at
150 K) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from the Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data request/cif.
Experimental Section
General: All chemicals and solvents were of reagent grade.All reactions
were conducted under an argon atmosphere.Hexamethylphosphoric tria-
mide (HMPT) was purchased from Sigma-Aldrich Japan K.K. and used
without further purification.Column chromatography was carried out
with silica gel (Kanto Chemical Co., Inc., 100–210 mm).Preparative gel-
permeation chromatography (GPC) was performed on Japan Analytical
Industry Co., Ltd. LC-908W equipped with JAI-GEL 1H, 2H column as-
sembly. 1H and 13C NMR spectra were recorded on a JEOL JNM-
Alpha400 spectrometer operating at 400 MHz for 1H and 100 MHz for
13C.The chemical shifts are reported downfield from internal Me 4Si.
Mass spectra were recorded in EI mode with an ionization energy of
70 eV on a Shimadzu QP-5050A quadrupole mass spectrometer.The
melting points were determined from the TG-DTA analyses on an SII
EXSTAR6000 analyzer.IR spectra were recorded on a Shimadzu FTIR-
8100M spectrometer with a PIKE MIRacle diamond ATR.Elemental
analyses were performed at the Advanced Development & Supporting
Center, RIKEN.
Electronic bandcalculations : Intermolecular overlap integrals were cal-
culated by using the HOMOs of the donor molecules obtained by ex-
tended Hückel MO calculations with the semiempirical parameters for
the s and p Slater-type atomic orbitals listed in the Supporting Informa-
tion.The electronic band dispersions and Fermi surfaces were calculated
by using the intermolecular overlap integrals under the tight-binding ap-
proximation.[24]
Dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF): HMPT
(0.74 mL, 4.1 mmol) was added to a mixture of selone 10[5a] (226 mg,
0.68 mmol) and selone 11[29] (215 mg, 0.71 mmol) in benzene (90 mL) at
room temperature, and the solution was stirred for 2 h.After the removal
of the solvent under reduced pressure, the crude products were separated
by column chromatography (SiO2/CS2–CH2Cl2) and then purified by
preparative GPC (CS2).The target DMEDO-TSeF was isolated as
purple-red needles (31 mg, 0.065 mmol, 10%). M.p. 1998C (decomp);
1H NMR (400 MHz, CD2Cl2): d=4.27 (s, 4H; OCH2CH2O), 2.00 ppm (s,
6H; CH3); 13C NMR (100 MHz, CD2Cl2): d=127.33, 125.85, 109.38,
93.04, 67.03, 16.28 ppm; IR (neat): n˜ =1624 (s), 1443 (m), 1368 (m), 1268
(m), 1240 (w), 1134 cmꢀ1 (s); MS (70 eV, EI): m/z: 480 [M+ for
Electrical resistivity: The dc electrical resistivities were measured by the
standard four-probe method in the temperature range of 1.4–300 K. Gold
wires (10 or 18 mm) were attached to a single crystal by using carbon
paste, and silver paste was used to connect the gold wires to the measure-
ment substrate.
Magnetic susceptibility: Magnetic susceptibilities were measured on a
Quantum Design SQUID magnetometer (MPMS-XL5) for randomly ori-
ented samples in the temperature range of 1.9–10 K with a dc magnetic
field of 10 Oe.The diamagnetism of the sample holder was obtained
from blank experiments under the same conditions as those for the
sample measurements.The diamagnetic core susceptibilities of the
DMEDO-TSeF molecule, [Au(CN)4]ꢀ anion and solvent of crystalliza-
tions were evaluated with Pascalꢁs table: cdia [emumolꢀ1]: DMEDO-TSeF
ꢀ1.74”10ꢀ4; [Au(CN)4]ꢀ ꢀ1.04”10ꢀ4; THF ꢀ0.53”10ꢀ4; DOL ꢀ0.42”
10ꢀ4; DHF ꢀ0.65”10ꢀ4; THP ꢀ0.46”10ꢀ4; 1,3-DOX ꢀ0.58”10ꢀ4; DHP
C10H10O278Se80Se3]; elemental analysis calcd (%) for C10H10O2Se4:
25.13, H 2.11; found: C 25.14, H 2.11.
C
Cyclic voltammetry: The cyclic voltammogram of DMEDO-TSeF was re-
corded on a BAS ALS-model 610A analyzer in a benzonitrile solution of
Bu4NBF4 (0.1m), and glassy carbon working and Pt auxiliary electrodes
were employed.The sweep rate was 100 mVs ꢀ1.Potentials were refer-
enced to Ag/AgNO3 standard electrode and were calibrated versus the
Cp2Fe/Cp2Fe+ couple recorded under the same conditions.
ꢀ0.54”10ꢀ4; 1,4-DOX ꢀ0.58”10ꢀ4
.
Crystal preparation: Single crystals of the [Au(CN)4]ꢀ salts of DMEDO-
TSeF were prepared by galvanostatic oxidation under the conditions
listed in the Supporting Information.THF and 1,4-DOX were purchased
from Kanto Chemical Co., Inc. and used without further purification.
THP and dichloromethane were purchased from Sigma-Aldrich Japan
K.K. and Dojindo Laboratories and used without further purification.
DHF, DOL, DHP, and 1,3-DOX were purchased from Tokyo Chemical
Industry Co., Ltd. and distilled before use. Cyclohexane was purchased
from Junsei Chemical Co., Ltd. and distilled before use. Platinum wire
electrodes (1.0 mm 1) and standard H-shaped cells were employed.The
identity of the solvent of crystallization was confirmed by 1H NMR spec-
Acknowledgement
We thank Dr. Kenji Yoza (Bruker AXS K.K.) for his kind advice on crys-
tal structure analysis.
Chem. Eur. J. 2007, 13, 7619 – 7630
ꢀ 2007 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
www.chemeurj.org
7629

T.Imakubo et al.
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Published online: July 3, 2007
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