˚
donor molecules diminished to 3.2 A from the room temperature
˚
value of 4.7 A. Therefore, the structural change is not simple
˚
thermal contraction but the molecules glide by 1.5 A along the
molecular long axis. As a result of this immense structural change,
it is quite reasonable that the single crystals are extremely fragile
during phase transition.
In summary, we have successfully synthesized a new unsymme-
trical donor DMEDO-TSeF without the use of highly toxic
reagents. Novel organic metals with octahedral anions have been
prepared and their crystal structure and physical properties have
been investigated. Among them, the first-order phase transition
observed in the PF6 salt at 215 K will attract much interest not
only as a phenomenon of basic science but also as a building
block for a molecular device because of the huge molecular
˚
motion (1.5 A per molecule) during phase transition and the wide
temperature range of hysteresis.12,13 Further studies on the physical
properties of (DMEDO-TSeF)2X are now in progress together
with the exploration of related materials.
Fig. 4 Temperature dependence of the cell parameters for (DMEDO-
TSeF)2PF6. The values of cell parameters are normalized to their
respective values at 293 K. The solid and broken lines indicate the cooling
and warming process, respectively.
Notes and references
observed in the PF6 salt play an important role in first-order
metal–metal transition (vide infra). The anions of these three salts
were taken in a cavity formed by the zigzag-type donor stacks
and showed disorder based on uni-axial rotation. In the SbF6
salt, the motion of the octahedral anion is a jiggle rather than a
rotation because large SbF6 anions are installed in the cavity more
precisely.
{ Selected data of new compound DMEDO-TSeF: purple-red needles, mp
199 uC (decomp.); m/z (EI, 70 eV): 480 (M+ for C10H10O278Se80Se3); dH
(270 MHz, CD2Cl2) 4.27 (4H, s, OCH2CH2O), 2.00 (6H, s, CH3); IR (neat,
n/cm21) 1624 (s), 1443 (m), 1368 (m), 1268 (m), 1240 (w), 1134 (s);
Elemental analysis: Calc. for C10H10O2Se4: C, 25.13; H, 2.11. Found: C,
25.14; H, 2.11%.
§ Crystal data for DMEDO-TSeF: C10H10O2Se4, M = 478.02, purple-red
needles (0.50 6 0.06 6 0.05 mm), monoclinic, P21/c (#14), a = 13.958(4),
3
˚
˚
b = 8.285(2), c = 11.867(3) A, b = 109.478(6)u, V = 1293.8(6) A ,
m = 11.323 mm21, Z = 4, 9395 reflections measured, 3223 unique
(Rint = 0.0571). Final R indices [I . 2s(I)]: R1 = 0.0501, wR2 = 0.1262.
GOF = 1.076. Crystal data for (DMEDO-TSeF)2PF6: C20H20O4Se8PF6,
The unit cell parameters of the PF6 salt have been measured at
various temperatures from 293 to 220 K. As shown in Fig. 4, the
values of cell parameters a, b and c regularly decrease with
temperature down to 220 K due to thermal contraction. We tried
to perform structure analysis at 200 K (below the transition
temperature of 215 K) in order to investigate the low-temperature
metallic phase. However, the refinement of the cell parameters
was unsuccessful due to the appearance of many incommensurate
reflections. In the warming process, coherence of the crystals was
recovered above 215 K, and the cell parameters showed drastic
change due to the generation of a new phase. The cell parameters
of the PF6 salt at 220 K are summarized in Table 2 compared with
the room temperature values of the PF6, AsF6 and SbF6 salts. It is
interesting that the new phase observed in the warming process is
isostructural with the AsF6 and SbF6 salts and it should be also
noted that the drastic changes of the unit cell angles are
characteristic in this phase transition. According to preliminary
structure refinement, the slipping distance between neighboring
¯
M = 1101.01, black needles (0.20 6 0.05 6 0.02 mm), triclinic, P1 (#2), a =
˚
7.302(3), b = 7.977(3), c = 13.500(6) A, a = 73.739(10), b = 79.794(8), c =
79.329(10)u, V = 735.2(5) A , m = 10.062 mm21, Z = 1, 5474 reflections
3
˚
measured, 3607 unique (Rint = 0.0935). Final R indices [I . 2s(I)]: R1 =
0.0504, wR2 = 0.1176. GOF = 0.847. Crystal data for (DMEDO-
TSeF)2AsF6: C20H20O4Se8AsF6, M = 1144.96, black needles (0.50 6
¯
0.03 6 0.02 mm), triclinic, P1 (#2), a = 7.269(3), b = 7.632(3), c =
3
˚
˚
14.345(6) A, a = 78.664(8), b = 86.234(8), c = 69.542(7)u, V = 731.1(5) A ,
m = 11.187 mm21, Z = 1, 4486 reflections measured, 3177 unique
(Rint = 0.0351). Final R indices [I . 2s(I)]: R1 = 0.0718, wR2 = 0.1872.
GOF = 0.942. Crystal data for (DMEDO-TSeF)2SbF6: C20H20O4Se8SbF6,
¯
M = 1191.79, black needle (0.40 6 0.03 6 0.02 mm), triclinic, P1 (#2),
˚
a = 7.281(3), b = 7.930(3), c = 14.519(5) A, a = 79.806(8), b = 89.564(9),
c = 65.582(7)u, V = 749.2(4) A , m = 10.702 mm21, Z = 1, 5603 reflections
3
˚
measured, 3688 unique (Rint = 0.0586). Final R indices [I . 2s(I)]:
R1 = 0.0652, wR2 = 0.1442. GOF = 0.862. CCDC reference numbers
281658–281661. For crystallographic data in CIF format see DOI: 10.1039/
b511820d
1 H. Yamochi, in TTF Chemistry—Fundamentals and Applications of
Tetrathiafulvalene: Oxygen analogues of TTFs, ed. J. Yamada and
T. Sugimoto, Kodansha & Springer, Tokyo, 2004, ch. 4.
2 T. Suzuki, H. Yamochi, G. Srdanov, K. Hinkelmann and F. Wudl,
J. Am. Chem. Soc., 1989, 111, 3108–3109.
Table 2 Comparison of the cell parameters between the room and
low-temperature phases of PF6 salt and the room-temperature phase of
AsF6 and SbF6 salts
3 T. Imakubo and K. Kobayashi, J. Mater. Chem., 1998, 8, 1945–1947.
4 (a) M. A. Beno, H. H. Wang, A. M. Kini, K. D. Carlson, U. Geiser,
W. K. Kwok, J. E. Thompson, J. M. Williams, J. Ren and
M.-H. Whangbo, Inorg. Chem., 1990, 29, 1599–1601; (b) S. Kahlich,
D. Schweitzer, I. Heinen, S. E. Lan, B. Nuber, H. J. Keller, K. Winzer
and H. W. Helberg, Solid State Commun., 1991, 80, 191–195.
5 R. R. Schumaker, V. Y. Lee and E. M. Engler, J. Phys. (Paris), 1983,
44, C3-1139–1145.
PF6
PF6
AsF6
SbF6
T/K
˚
293
220a
293
293
a/A
˚
7.302(3)
7.977(3)
13.500(6)
73.739(10)
79.794(8)
79.329(10)
735.2(5)
7.178(4)
7.623(5)
14.174(8)
79.375(12)
87.655(14)
68.949(13)
711.2(7)
7.269(3)
7.632(3)
14.345(6)
78.664(8)
86.234(8)
69.542(7)
731.1(5)
7.281(3)
7.930(3)
14.519(5)
79.806(8)
89.564(9)
65.582(7)
749.2(4)
b/A
˚
c/A
a/deg
b/deg
c/deg
6 T. Imakubo, T. Shirahata and M. Kibune, Chem. Commun., 2004,
1590–1591.
3
˚
V/A
a
7 (a) A. M. Kini, T. Mori, U. Geiser, S. M. Budz and J. M. Williams,
J. Chem. Soc., Chem. Commun., 1990, 647–648; (b) J.-M. Fabre,
Warming process.
This journal is ß The Royal Society of Chemistry 2005
J. Mater. Chem., 2005, 15, 4399–4402 | 4401