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Metal complexes with extended TTF dithiolato ligand: PTDT
Synthetic
Metals
102 (1999)
1768-1769
Metal complexes with extendedTTF dithiolato ligand: PTDT
The University
Abstract Novel monoanionic,
dianionic
A. Kobayashi, hf. Kumasaki and H. Tanaka of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033,
and neutral nickel,
propylenedithiotetrathiafulvalenedithiolate[ptdtz~=(SsC~H~)z~], show the possibility of the electronic band formation crystal
of Ni(ptdt),
revealed
an extremely
copper and palladium by novel
high electrical
complexes
have been synthesized. 2D or 3D intermolecular
conductivity(7
Japan
with the extended TTF dithiolato
ligand,
The crystal structures of these complexes contacts through ptdt ligands. The sing1 e
S cm-‘) at room temperature
as a neutral molecular crystal.
Keywords: Organic conductors based on radical cation and/or anion salts 1. Introduction In
recent
tetramethylammonium investigations
of
molecular
conductors
and
superconductors, there is an increasing interest in molecules with extended x-conjugated frameworks[l]. This is because such molecules can stabilize multi-cation states and increase intermolecular interactions. However, only a few conducting metal complexes with elongated dithiolene-type ligands have been prepared [2,3]. Usually,the solubility of extended-ligand complexesis poor. In order to increase solubility, we prepared anew ligand ptdt2- whichincorporates an additional methylene group into etdt2‘. The long ligand will be preferably favorable for increasing overlapping between the molecules. Each of the two tetrathiafulvalene transition metal atom will
moieties joined to the central be able to produce S...S networks
even if the metal complex molecule has conformation. We report here the preparations characterizations of M(ptdt), complexes.
a twisted and the
dithiolates
(Ph,P)2[Pd(ptdt),].0.6Me2C0 structure determination, resistivity, 3. Results
were performed
by X-ray crystal
cyclic voltammetry, electrical ESR and magnetic susceptibility measurements. and discussion
3.1 (Me,N)[Ni(ptdt),].l.4Me2C0 The [Ni(ptdt)2J-anion the molecule is fairly group. The geometry
is shown in Fig. 1. Theplanarity of good except the terminal propylenic around Ni is squar planar and the Ni-S
distances are 2.163(l), 2.172(l), 2.174(l) and 2.164(l) while the S-Ni-S angles within the five-membered ring
2. Experimental We prepared the tetrathiafulvalene
salts of metal complexes were obtained
by deprotection of cyanoethyl group with Me,NOH followed by addition of methanol solutions of MCI, (M=Ni, Cu and Pd) at -78°C. The neutral [Ni(ptdt)2] was obtained by electrochemical oxidation. Characterization of (Me,N)[Ni (ptdt),?], neutral [Ni(ptdt)2], (Ph,P)2[Cu(ptdt)2].l .2Me,CO and
following
the
A are
93.11(4) and 92.86(4)‘, the remainder are 85.52(4) and 88.72(4)‘, respectively. One of the ligand of the monoanion [Ni(ptdt)2]‘ overlaps with that of an adjacent anion separated
method of Narvor etal [2]. We first used p-acetoxybenzyl as the protecting group in cross-coupling to synthesize the unsymmetrical precursor of ptdt2‘[3,4]. However the cross-
by about half of the unit of the molecules, forming a onedimensional chain along [loll. The overlapping mode of [Ni(ptdt),]- is ring-over-bond type and the interplanar distance
coupling molecule
is 3.30 A. The electrical conductivity was 1.4x10” S cm“ at room temperature and dropped with decreasing temperature indicating semiconducting behavior with E,=O.O9eV (lSlK-292K).
method gave more than five products and our target was obtained in 4.6% yield. We then used
cyanoethyl as the protecting group and succeeded obtaining the precursor of ptdt2- in high yield (61%). 0379-6779/99/$ - see. front matter PII: SO379-6779(98)000488-3
0 1999
Elsevier
Science
S.A.
in The
All rights
reserved.
A. Kobayashi
Fig. 1. [ Ni(ptdt)&
et al. I Synthetic
Merais it?2 (1999)
1768-1769
anion
3.2 (Ph,P)z[Cu(ptdt)z].l.2MezC0 A distorted tetrahedral
geometry
is observed
atom with Cu-S distances of 2.279(4),
2.273(4),
around the Cu 2.282(4)
and
2.265(4) A and S-Cu-S angles of 93.6(l), 93.2(l), 140.3(2) and 142.0(2)‘. The dihedral angle between the planes is 54.2’. Theanions form a one-dimensional chain along the c-direction
Fig. 2. The crystal structure of neutral
[Ni(ptdtfZ]
with both ligands, which overlap in ring-over-bond type with those of adjacent anions. The interplanar distance is ca. 3.39 A. The large Ph,P+ cations prevent overlapping along the b direction.
The x-conjugated
systems
of the ptdt ligands
are
large enough to form Magnetic susceptibility
conduction pathways in the crystal. within the temperature range 2-300 K
obeyed Curie behavior,
indicating
the presence of Cu2*.
T IK
3.3 Neutral [Ni(ptdt)z]
Fig. 3. Pressure dependence of electrical neutral [Ni(ptdt)2J
The crystal structure
of
indicates that the overlap one is larger than those
neutral
[Ni(ptdt)z](THF)
of the molecule in 1:l or 2:l
(Fig.
resistivities
of
2)
with the adjacent complexes. The
shortest intermolecular S...S distance is 3.34 A. Ni(ptdt), molecules stack stepwisely along the long axis of the molecules, Magnetic susceptibility was measured from room temperature down to 2K. The C-value corresponds to only 2.2 % of the value calculated for one S=1/2 spin entity per formula unit. The room temperature electrical conductivity was 7 S
The ab initio
calculations
of HF/6-311G*
level were performed by Gaussian 94. The symmetries of HOMO and LUMO orbitals are similar to those of dmit metal complexes. These calculations between HOMO and LUMO conductivities presumably
suggest that the energy gap levels is small. The high
intermolecular overlap associated ligand n-systems and preliminary
reflected the improved with the use of extended band structure calculation
cm-l, which is abnormaly higher than the values normally observed for neutral complexes of dithiolenes (1O‘3 S cm-‘).
suggest the possibility of the development semi-metallic neutral molecular crystals.
The conductivity indicating the
4. References
decreased slowly with lowering temperature semiconducting behavior. The activation
and CIS/3-21G*
of
metallic
or
S. Koyanagi,
T.
Yamabe and M. Shiro, Chem. Lett., (19 9 2 ) 2321. [2] N.L. Narvor, N. Robertson, T. Weyland, J.D. Kilburn,
A.
energy was 0.09 eV. Recently, we obtained neutral complex without molecules. Crystal data of [Ni(ptdt&J: monoclinic, group C2/c, a =10.053(3), v=2750.3(1.8) 95.31(3)‘, electrical from high
resistivities conducting
solvent space
6 = 11.734(5), c =23.415(g) A, /I= A3. Pressure dependence of
indicated
that there is a phase transition
state to low conducting
state below 60
K (Fig. 3). The ESR spectrum of polycrystalline sample, observed at 260 K, showed only one signal g= 2.024 and the line width was 88 G . It grew gradualy, with decreasing temperature. Below 100 K, another radical species(g=2.0238) began to grow.
[l]
Y. Misaki,
H. Nishikawa,
K. Kawakami,
E. Underhill, M. Webster, N. Svenstrup Chem. Commun., (19 9 6) 1363.
and J. Becker,
[3] M. Nakano, A. Kuroda, T. Maikawa and G. Matsubayashi, Mol. Cryst. Liq. Cryst., 284 (1996) 301. [4] M. Kumasaki, H. Tanaka Chem.,l (1998) 301. [5] K. Ueda , M.Goto, Yamamoto
and A. Kobayashi,
T. Sugimoto,
and H. Fujita,
J. Mater.
S. Endo, N. Toyota,
Synth. Met., 85 (1997)
K.
1679.
Metals
102 (1999)
1768-1769
Metal complexes with extendedTTF dithiolato ligand: PTDT
The University
Abstract Novel monoanionic,
dianionic
A. Kobayashi, hf. Kumasaki and H. Tanaka of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033,
and neutral nickel,
propylenedithiotetrathiafulvalenedithiolate[ptdtz~=(SsC~H~)z~], show the possibility of the electronic band formation crystal
of Ni(ptdt),
revealed
an extremely
copper and palladium by novel
high electrical
complexes
have been synthesized. 2D or 3D intermolecular
conductivity(7
Japan
with the extended TTF dithiolato
ligand,
The crystal structures of these complexes contacts through ptdt ligands. The sing1 e
S cm-‘) at room temperature
as a neutral molecular crystal.
Keywords: Organic conductors based on radical cation and/or anion salts 1. Introduction In
recent
tetramethylammonium investigations
of
molecular
conductors
and
superconductors, there is an increasing interest in molecules with extended x-conjugated frameworks[l]. This is because such molecules can stabilize multi-cation states and increase intermolecular interactions. However, only a few conducting metal complexes with elongated dithiolene-type ligands have been prepared [2,3]. Usually,the solubility of extended-ligand complexesis poor. In order to increase solubility, we prepared anew ligand ptdt2- whichincorporates an additional methylene group into etdt2‘. The long ligand will be preferably favorable for increasing overlapping between the molecules. Each of the two tetrathiafulvalene transition metal atom will
moieties joined to the central be able to produce S...S networks
even if the metal complex molecule has conformation. We report here the preparations characterizations of M(ptdt), complexes.
a twisted and the
dithiolates
(Ph,P)2[Pd(ptdt),].0.6Me2C0 structure determination, resistivity, 3. Results
were performed
by X-ray crystal
cyclic voltammetry, electrical ESR and magnetic susceptibility measurements. and discussion
3.1 (Me,N)[Ni(ptdt),].l.4Me2C0 The [Ni(ptdt)2J-anion the molecule is fairly group. The geometry
is shown in Fig. 1. Theplanarity of good except the terminal propylenic around Ni is squar planar and the Ni-S
distances are 2.163(l), 2.172(l), 2.174(l) and 2.164(l) while the S-Ni-S angles within the five-membered ring
2. Experimental We prepared the tetrathiafulvalene
salts of metal complexes were obtained
by deprotection of cyanoethyl group with Me,NOH followed by addition of methanol solutions of MCI, (M=Ni, Cu and Pd) at -78°C. The neutral [Ni(ptdt)2] was obtained by electrochemical oxidation. Characterization of (Me,N)[Ni (ptdt),?], neutral [Ni(ptdt)2], (Ph,P)2[Cu(ptdt)2].l .2Me,CO and
following
the
A are
93.11(4) and 92.86(4)‘, the remainder are 85.52(4) and 88.72(4)‘, respectively. One of the ligand of the monoanion [Ni(ptdt)2]‘ overlaps with that of an adjacent anion separated
method of Narvor etal [2]. We first used p-acetoxybenzyl as the protecting group in cross-coupling to synthesize the unsymmetrical precursor of ptdt2‘[3,4]. However the cross-
by about half of the unit of the molecules, forming a onedimensional chain along [loll. The overlapping mode of [Ni(ptdt),]- is ring-over-bond type and the interplanar distance
coupling molecule
is 3.30 A. The electrical conductivity was 1.4x10” S cm“ at room temperature and dropped with decreasing temperature indicating semiconducting behavior with E,=O.O9eV (lSlK-292K).
method gave more than five products and our target was obtained in 4.6% yield. We then used
cyanoethyl as the protecting group and succeeded obtaining the precursor of ptdt2- in high yield (61%). 0379-6779/99/$ - see. front matter PII: SO379-6779(98)000488-3
0 1999
Elsevier
Science
S.A.
in The
All rights
reserved.
A. Kobayashi
Fig. 1. [ Ni(ptdt)&
et al. I Synthetic
Merais it?2 (1999)
1768-1769
anion
3.2 (Ph,P)z[Cu(ptdt)z].l.2MezC0 A distorted tetrahedral
geometry
is observed
atom with Cu-S distances of 2.279(4),
2.273(4),
around the Cu 2.282(4)
and
2.265(4) A and S-Cu-S angles of 93.6(l), 93.2(l), 140.3(2) and 142.0(2)‘. The dihedral angle between the planes is 54.2’. Theanions form a one-dimensional chain along the c-direction
Fig. 2. The crystal structure of neutral
[Ni(ptdtfZ]
with both ligands, which overlap in ring-over-bond type with those of adjacent anions. The interplanar distance is ca. 3.39 A. The large Ph,P+ cations prevent overlapping along the b direction.
The x-conjugated
systems
of the ptdt ligands
are
large enough to form Magnetic susceptibility
conduction pathways in the crystal. within the temperature range 2-300 K
obeyed Curie behavior,
indicating
the presence of Cu2*.
T IK
3.3 Neutral [Ni(ptdt)z]
Fig. 3. Pressure dependence of electrical neutral [Ni(ptdt)2J
The crystal structure
of
indicates that the overlap one is larger than those
neutral
[Ni(ptdt)z](THF)
of the molecule in 1:l or 2:l
(Fig.
resistivities
of
2)
with the adjacent complexes. The
shortest intermolecular S...S distance is 3.34 A. Ni(ptdt), molecules stack stepwisely along the long axis of the molecules, Magnetic susceptibility was measured from room temperature down to 2K. The C-value corresponds to only 2.2 % of the value calculated for one S=1/2 spin entity per formula unit. The room temperature electrical conductivity was 7 S
The ab initio
calculations
of HF/6-311G*
level were performed by Gaussian 94. The symmetries of HOMO and LUMO orbitals are similar to those of dmit metal complexes. These calculations between HOMO and LUMO conductivities presumably
suggest that the energy gap levels is small. The high
intermolecular overlap associated ligand n-systems and preliminary
reflected the improved with the use of extended band structure calculation
cm-l, which is abnormaly higher than the values normally observed for neutral complexes of dithiolenes (1O‘3 S cm-‘).
suggest the possibility of the development semi-metallic neutral molecular crystals.
The conductivity indicating the
4. References
decreased slowly with lowering temperature semiconducting behavior. The activation
and CIS/3-21G*
of
metallic
or
S. Koyanagi,
T.
Yamabe and M. Shiro, Chem. Lett., (19 9 2 ) 2321. [2] N.L. Narvor, N. Robertson, T. Weyland, J.D. Kilburn,
A.
energy was 0.09 eV. Recently, we obtained neutral complex without molecules. Crystal data of [Ni(ptdt&J: monoclinic, group C2/c, a =10.053(3), v=2750.3(1.8) 95.31(3)‘, electrical from high
resistivities conducting
solvent space
6 = 11.734(5), c =23.415(g) A, /I= A3. Pressure dependence of
indicated
that there is a phase transition
state to low conducting
state below 60
K (Fig. 3). The ESR spectrum of polycrystalline sample, observed at 260 K, showed only one signal g= 2.024 and the line width was 88 G . It grew gradualy, with decreasing temperature. Below 100 K, another radical species(g=2.0238) began to grow.
[l]
Y. Misaki,
H. Nishikawa,
K. Kawakami,
E. Underhill, M. Webster, N. Svenstrup Chem. Commun., (19 9 6) 1363.
and J. Becker,
[3] M. Nakano, A. Kuroda, T. Maikawa and G. Matsubayashi, Mol. Cryst. Liq. Cryst., 284 (1996) 301. [4] M. Kumasaki, H. Tanaka Chem.,l (1998) 301. [5] K. Ueda , M.Goto, Yamamoto
and A. Kobayashi,
T. Sugimoto,
and H. Fujita,
J. Mater.
S. Endo, N. Toyota,
Synth. Met., 85 (1997)
K.
1679.