- Email: [email protected]
S-position isomers of BEDT-TTF and derivatives as new precursors of organic materials
Synthetic Metals 94 (1998) 41-44
S-position isomers of BEDT-TTF and derivatives as new precursors of organic materials S. Le Moustarder a, P. Hudhomme b, M. Sal16 a, P. Blanchard a, A. Riou a,*, M. Jubault a, G. Duguay b, A. Gorgues a ’ Lahoratoiw
d’IngPniwie ’ Lahoratoire
Mokulniw PT MatPrinux de S.vnthPse Organique,
Orgnniqws, UMR CNRS
1JMR CNRS 6513, Universitl
6501, IJniverritt d’Ang~rs, 2 boulevard de Nantes, 2 rue de la Houssinit?re,
lavoisier, F-49045 Anger.?, France F-44322 Nanres, France
Abstract Single crystals of two isostructural radical cation salts have been prepared by electrocrystallization from a new disulfide tetrathiafulvalene derivative. X-ray crystalline structures of the neutral donor and of the corresponding perchlorate and hexafluorophosphate salts are described. 0 1998 Elsevier Science S.A. All rights reserved. Keywords:
Tetrathiafulvalene; Electrocrystallization; Radical cation salts: X-ray structure
1. Introduction Bis( ethylenedithio) tetrathiafulvalene (BEDT-TTF) is known to generatethe highestT, organic superconductorsof the tetrathiafulvalene (TTF) series[ 1] . The prominentrole of the outer sulfur atomsof the BEDT-TTF core (and other related r-donors) is well establishedin mostof the resulting charge transfercompounds[ 1b,2,3] . In this context, we have carried out the synthesisof the Sposition isomerA of BEDT-TTF and the related derivative B [4] (Fig. 1). By analogy with materialsobtained from BEDT-TTF, radical cation saltsof compoundB have been obtainedeither by chemical or electrochemicaloxidation in the presenceof various anions.In this paper,we have particularly focusedon the crystallographic study of neutral molecule B and its saltsobtained by electrochemicaloxidation, namely, B.PF6 (1) andB*ClO, (2) [4].
2. Experimental The cyclic voltammogramsof thesetwo new r-donors A and B exhibit two reversible le- oxidation peaks,whose oxidation potentials are very close to those of BEDT-TTF (Table 1). Consequently,good n-donor ability of B allowed us to prepareby electrooxidation new related radical cation salts1 and2. * Corresponding 0379~6779/98/$19.00 PIlSO379-6779(97)04137-4
author 0
1998 Elsevier
Science S.A. All rights reserved.
A
B Fig. 1. The two new organic donors.
Table I Oxidation peak potential ED., and Epaz values in V/SCE: Ptelectrode, 2O”C, under a nitrogen atmosphere, 0.1 M Bu,N’PF,in CH,Cl,, scan rate 0.2 V SK’, [compound] = IO-‘M Compound
A
B
BEDT-TTF
E,,, (‘J) E,az (V)
0.49 0.93
0.5 I 0.9 I
AE,
0.44
0.40
n-5 I 0.92 0.41
(‘0
On the onehand,red platesof neutralB have beenprepared by recrystallization from dichloromethane/petroleumether. On the other hand,black needlesof salts1 and2 were grown on a platinum wire anodeupon constantlow current density (0.5 FA cm-*) oxidation of the donor B in the presenceof, respectively, Bu,N+PF,- and Bu,N’ C104- solutions(0.1 mol l- ’ in chlorobenzene) The X-ray structuresof the neutralmoleculeandof the two new salts were determinedwith an Enraf-Nonius MACH3 four-circles diffractometerequippedwith agraphitemonochromatizedMO Kol radiation. Thesestructureswere solvedby
42 Table 2 Crystallographic
S. Le Moustarder
et al. /Swthetic
Metals
94 (1998)
41-44
data of the three structures
Crystal dimensions (mm) Crystal system Space group a (A) h(A) c(A) P (“) Volume ( W3) &.%I A (MO Ka) (A) Temperature of measurement (Kf Measured reflections No. of reflections included in refinement Absorption coefficient p (cm’) Program Program of refinement No. of parameters R RV
B
B*PF,
BeCIO,
1 x 0.04 x 0.03 monoclinic P2,lc 5.096(5) 1 I .726(4) 25.804(7) 94.8X(5) 1536(2) 1.665( 1) 0.7 1073 298 5140 861 with 1>3rr(I) 10.965 SIR Molen 163 0.058 0.059
1 x 0.07 x 0.03 monoclinic P2,lc 7.088(9) 21.260(7) 12.763(4) 87.64(6) 1922(3) 1X38( I ) 0.7 1073 298 6278 1208 with I > 3o( I) 10.261 SIR Molen 244 0.056 0.057
0.6 x 0.06 X 0.04 monoclinic P2,lc 7.039( 5) 20.927(7) 12.551(4) 92.9315) 1846(2) 1.749( 1) 0.7 1073 298 3627 688 with I> 3a(I) 10.865 SIR Molen I64 0.066 0.067
direct methods (Program SIR) and successive Fourier difference synthesis and refined by the full-matrix least-squares method. H atoms were placed at computed positions (by the HYDRO Program) and were not refined. All crystallographic data are summarized in Table 2. Fig. 2. The crystal structure
3. Results and discussion
of the neutral molecule
B.
around the S-S bridge corresponding to a half-chair conformation (Fig. 2).
3.1. Neutral molecule B The X-ray diffraction study shows that the central TTF core of B is essentially planar. The two external S-CH, bonds are deviated on the same side of the molecular plane with dihedral angles of 42 and 75” for ( C9--S,-CT-S,) and (Cl”S8-C,-S6), respectively. By analogy with BEDT-TTF [ 51, the six-membered ring presents a distorsion, but in this case
3.2. Two new organic salts: B- PF,, B- CIO, Both salts are isostructural and have a 1: 1 stoichiometry. The donor moiety is planar. The terminal disulfide bridge displaced from the molecule plane. In both salts, the corresponding sulfur atoms are found in two positions with an
b
Fig. 3. View of the donor molecule
and of the disordered
anion in the salt B*ClO,
S. Le Moustarder
et al. /Synthetic
occupation ratio, respectively, of 57143 and 50/50, and are associated with two highly distorted half-chair conformations of the external disulfide heterocycle. By analogy with other bis(methylsulfanyl)tetrathiafulvalene derivatives, the external S-CH3 bonds are out of the molecular plane in the neutral molecule, but tend to lie in the donor moiety in salts I and 2. As in the case of BEDT-TTF, the Cs-C6 bond length of the donor moiety in B *ClO, and B * PF, increases (d( Cg-
Metals
94 (1998) 4144
43
C,) = I .368(23) and 1.368( 13) A, respectively), compared to the neutral donor B (d(C,-C,) = 1.347( 15) A) [GS] (Fig. 3). The crystal structure consists in a head-to-tail stacking of dimerized donor molecules along the [ 1001 direction. Inside a dimer, the two molecules are centrosymmetrically related. The distances intra- and interdimer are 3.42 and 3.64 A in 1 and 3.44 and 3.59 A, respectively, in 2 (Table 3). Within dimers, there are several contacts shorter than twice the van
3.59 A
3.4-a i a OS C
w
b
L-7
Fig. 4. View of the stacking
mode of the donor molecules
in the salt B-~70,:
mtradimer
Fig. 5. View of the stacking
mode of the donor molecules
in the salt B *PF,: intradimer
and interstack
contacts.
a
3.42
A I
--
intermolecular contacts and interstack
contacts.
44 Table 3 Intradimer
S. Le Moustarder
et al. /Synthetic
contact distances
Compound 4&-S’,) 4%S’d d(S,-S’,)
=4&S’,) =&W’s) =d(S,S’,)
Table 4 Interstack
contact distances
Compound
(8, (A) (A,
B*PF,
B-Clod
3.51 3.51 3.55
3.55 3.51 3.59
B.PF,
B*C104
3.59 3.63 3.56 3.60
3.59 3.48 3.53 3.49
Metals
(.b (A) (A) (A)
der Waals radius of the S atom (3.70 A). Note that the 0 atoms of the anion in B *C104 are disordered. The main feature of both structures is outlined in Fig. 4, which shows that the terminal disulfide bridge (S la, Sl b, S2a, S2b) is clearly engaged in S.. .S interstack contacts as shown by short intermolecular contacts into the bc plane (Table 4, Fig. 5).
References
[21 131 141
I51
[61 4. Conclusions [71
Conductivity measurements were carried out using the two-probe technique. The conductivity of salts 1 and 2 is
4144
lower than lop5 S cm- ’ at room temperature. However, the crystallographic study of these new salts shows the role of the terminal disulfide bridge in the structural organization: outer sulfur atoms could participate in the increasing dimensionality of materials. Mixed valence state salts have not yet been obtained from the donor B, but new efforts are being devoted to prepare them. In addition, other experiments are being carried out to obtain novel organic salts with the new donor A.
[II d(S,a-W d(S,,-U d(S,a-S,) d(S,&)
94 (1998)
[sl
(a) T. Nakamura, T. Nobutoki, M. Miyamoto, Y. Tsubokura, R. Tsuchiya, T. Takahashi, K. Kanoda, G. Saito, J. Supraconductivity 7 (1994) 671; (b) J.M. Williams,A.M. Kini,H.H. Wang,K.D.Carlson, U. Geiser, L.K. Montgomery, G.J. Pyrka, D.M. Watkins, J.M. Kommers, S.J. Boryschuk, A.V. Strieby Crouch, W.K. Kwok, J.E. Schirbe, D.L. Overmyer, D. Jung, M.H. Whangbo, Inorg. Chem. 29 ( 1990) 3262. J.J. Novoa, M.C. Rovira, C. Rovira, J. Veciana, J. Tar&, Adv. Mater. 7 (1995) 233. M.C. Rovira, J.J. Novoa, J. Tarn%, C. Rovira, J. Veciana, S. Yang, D.O. Cowan, E. Canadell, Adv. Mater. 7 ( 1995) 1023. P. Hudhomme, P. Blanchard, M. Salle, S. Le Moustarder, A. Riou, M. Jubault, A. Gorgues, G. Duguay, Angew. Chem., Int. Ed. Engl. 36 ( 1997) 878. J.M. Williams, J.R. Ferraro, R.J. Thorn, K.D. Carlson, U. Geiser,H.H. Wang, A.M. Kini, M.H. Whangbo, Organic Superconductors (Including Fullerenes), Prentice-Hall, Englewood Cliffs, NJ, 1992. C. Livage, M. Fourmigut, P. Batail, E. Canadell, C. Coulon, Bull. Sot. Chim. Fr. 130 (1993) 761. K.A. Abboud, M.B. Clavenger, G.F. de Oliviera, D.R. Talham, J. Chem. Sot., Chem. Commun. ( 1993) 1560. L. Ouahab, M. Fettouhi, J.F. Halet, V.M. Yartsev, C. GarrigouLagrange, P. Delhaes, C. Sourisseau, New J. Chem. 17 ( 1993) 399.
S-position isomers of BEDT-TTF and derivatives as new precursors of organic materials S. Le Moustarder a, P. Hudhomme b, M. Sal16 a, P. Blanchard a, A. Riou a,*, M. Jubault a, G. Duguay b, A. Gorgues a ’ Lahoratoiw
d’IngPniwie ’ Lahoratoire
Mokulniw PT MatPrinux de S.vnthPse Organique,
Orgnniqws, UMR CNRS
1JMR CNRS 6513, Universitl
6501, IJniverritt d’Ang~rs, 2 boulevard de Nantes, 2 rue de la Houssinit?re,
lavoisier, F-49045 Anger.?, France F-44322 Nanres, France
Abstract Single crystals of two isostructural radical cation salts have been prepared by electrocrystallization from a new disulfide tetrathiafulvalene derivative. X-ray crystalline structures of the neutral donor and of the corresponding perchlorate and hexafluorophosphate salts are described. 0 1998 Elsevier Science S.A. All rights reserved. Keywords:
Tetrathiafulvalene; Electrocrystallization; Radical cation salts: X-ray structure
1. Introduction Bis( ethylenedithio) tetrathiafulvalene (BEDT-TTF) is known to generatethe highestT, organic superconductorsof the tetrathiafulvalene (TTF) series[ 1] . The prominentrole of the outer sulfur atomsof the BEDT-TTF core (and other related r-donors) is well establishedin mostof the resulting charge transfercompounds[ 1b,2,3] . In this context, we have carried out the synthesisof the Sposition isomerA of BEDT-TTF and the related derivative B [4] (Fig. 1). By analogy with materialsobtained from BEDT-TTF, radical cation saltsof compoundB have been obtainedeither by chemical or electrochemicaloxidation in the presenceof various anions.In this paper,we have particularly focusedon the crystallographic study of neutral molecule B and its saltsobtained by electrochemicaloxidation, namely, B.PF6 (1) andB*ClO, (2) [4].
2. Experimental The cyclic voltammogramsof thesetwo new r-donors A and B exhibit two reversible le- oxidation peaks,whose oxidation potentials are very close to those of BEDT-TTF (Table 1). Consequently,good n-donor ability of B allowed us to prepareby electrooxidation new related radical cation salts1 and2. * Corresponding 0379~6779/98/$19.00 PIlSO379-6779(97)04137-4
author 0
1998 Elsevier
Science S.A. All rights reserved.
A
B Fig. 1. The two new organic donors.
Table I Oxidation peak potential ED., and Epaz values in V/SCE: Ptelectrode, 2O”C, under a nitrogen atmosphere, 0.1 M Bu,N’PF,in CH,Cl,, scan rate 0.2 V SK’, [compound] = IO-‘M Compound
A
B
BEDT-TTF
E,,, (‘J) E,az (V)
0.49 0.93
0.5 I 0.9 I
AE,
0.44
0.40
n-5 I 0.92 0.41
(‘0
On the onehand,red platesof neutralB have beenprepared by recrystallization from dichloromethane/petroleumether. On the other hand,black needlesof salts1 and2 were grown on a platinum wire anodeupon constantlow current density (0.5 FA cm-*) oxidation of the donor B in the presenceof, respectively, Bu,N+PF,- and Bu,N’ C104- solutions(0.1 mol l- ’ in chlorobenzene) The X-ray structuresof the neutralmoleculeandof the two new salts were determinedwith an Enraf-Nonius MACH3 four-circles diffractometerequippedwith agraphitemonochromatizedMO Kol radiation. Thesestructureswere solvedby
42 Table 2 Crystallographic
S. Le Moustarder
et al. /Swthetic
Metals
94 (1998)
41-44
data of the three structures
Crystal dimensions (mm) Crystal system Space group a (A) h(A) c(A) P (“) Volume ( W3) &.%I A (MO Ka) (A) Temperature of measurement (Kf Measured reflections No. of reflections included in refinement Absorption coefficient p (cm’) Program Program of refinement No. of parameters R RV
B
B*PF,
BeCIO,
1 x 0.04 x 0.03 monoclinic P2,lc 5.096(5) 1 I .726(4) 25.804(7) 94.8X(5) 1536(2) 1.665( 1) 0.7 1073 298 5140 861 with 1>3rr(I) 10.965 SIR Molen 163 0.058 0.059
1 x 0.07 x 0.03 monoclinic P2,lc 7.088(9) 21.260(7) 12.763(4) 87.64(6) 1922(3) 1X38( I ) 0.7 1073 298 6278 1208 with I > 3o( I) 10.261 SIR Molen 244 0.056 0.057
0.6 x 0.06 X 0.04 monoclinic P2,lc 7.039( 5) 20.927(7) 12.551(4) 92.9315) 1846(2) 1.749( 1) 0.7 1073 298 3627 688 with I> 3a(I) 10.865 SIR Molen I64 0.066 0.067
direct methods (Program SIR) and successive Fourier difference synthesis and refined by the full-matrix least-squares method. H atoms were placed at computed positions (by the HYDRO Program) and were not refined. All crystallographic data are summarized in Table 2. Fig. 2. The crystal structure
3. Results and discussion
of the neutral molecule
B.
around the S-S bridge corresponding to a half-chair conformation (Fig. 2).
3.1. Neutral molecule B The X-ray diffraction study shows that the central TTF core of B is essentially planar. The two external S-CH, bonds are deviated on the same side of the molecular plane with dihedral angles of 42 and 75” for ( C9--S,-CT-S,) and (Cl”S8-C,-S6), respectively. By analogy with BEDT-TTF [ 51, the six-membered ring presents a distorsion, but in this case
3.2. Two new organic salts: B- PF,, B- CIO, Both salts are isostructural and have a 1: 1 stoichiometry. The donor moiety is planar. The terminal disulfide bridge displaced from the molecule plane. In both salts, the corresponding sulfur atoms are found in two positions with an
b
Fig. 3. View of the donor molecule
and of the disordered
anion in the salt B*ClO,
S. Le Moustarder
et al. /Synthetic
occupation ratio, respectively, of 57143 and 50/50, and are associated with two highly distorted half-chair conformations of the external disulfide heterocycle. By analogy with other bis(methylsulfanyl)tetrathiafulvalene derivatives, the external S-CH3 bonds are out of the molecular plane in the neutral molecule, but tend to lie in the donor moiety in salts I and 2. As in the case of BEDT-TTF, the Cs-C6 bond length of the donor moiety in B *ClO, and B * PF, increases (d( Cg-
Metals
94 (1998) 4144
43
C,) = I .368(23) and 1.368( 13) A, respectively), compared to the neutral donor B (d(C,-C,) = 1.347( 15) A) [GS] (Fig. 3). The crystal structure consists in a head-to-tail stacking of dimerized donor molecules along the [ 1001 direction. Inside a dimer, the two molecules are centrosymmetrically related. The distances intra- and interdimer are 3.42 and 3.64 A in 1 and 3.44 and 3.59 A, respectively, in 2 (Table 3). Within dimers, there are several contacts shorter than twice the van
3.59 A
3.4-a i a OS C
w
b
L-7
Fig. 4. View of the stacking
mode of the donor molecules
in the salt B-~70,:
mtradimer
Fig. 5. View of the stacking
mode of the donor molecules
in the salt B *PF,: intradimer
and interstack
contacts.
a
3.42
A I
--
intermolecular contacts and interstack
contacts.
44 Table 3 Intradimer
S. Le Moustarder
et al. /Synthetic
contact distances
Compound 4&-S’,) 4%S’d d(S,-S’,)
=4&S’,) =&W’s) =d(S,S’,)
Table 4 Interstack
contact distances
Compound
(8, (A) (A,
B*PF,
B-Clod
3.51 3.51 3.55
3.55 3.51 3.59
B.PF,
B*C104
3.59 3.63 3.56 3.60
3.59 3.48 3.53 3.49
Metals
(.b (A) (A) (A)
der Waals radius of the S atom (3.70 A). Note that the 0 atoms of the anion in B *C104 are disordered. The main feature of both structures is outlined in Fig. 4, which shows that the terminal disulfide bridge (S la, Sl b, S2a, S2b) is clearly engaged in S.. .S interstack contacts as shown by short intermolecular contacts into the bc plane (Table 4, Fig. 5).
References
[21 131 141
I51
[61 4. Conclusions [71
Conductivity measurements were carried out using the two-probe technique. The conductivity of salts 1 and 2 is
4144
lower than lop5 S cm- ’ at room temperature. However, the crystallographic study of these new salts shows the role of the terminal disulfide bridge in the structural organization: outer sulfur atoms could participate in the increasing dimensionality of materials. Mixed valence state salts have not yet been obtained from the donor B, but new efforts are being devoted to prepare them. In addition, other experiments are being carried out to obtain novel organic salts with the new donor A.
[II d(S,a-W d(S,,-U d(S,a-S,) d(S,&)
94 (1998)
[sl
(a) T. Nakamura, T. Nobutoki, M. Miyamoto, Y. Tsubokura, R. Tsuchiya, T. Takahashi, K. Kanoda, G. Saito, J. Supraconductivity 7 (1994) 671; (b) J.M. Williams,A.M. Kini,H.H. Wang,K.D.Carlson, U. Geiser, L.K. Montgomery, G.J. Pyrka, D.M. Watkins, J.M. Kommers, S.J. Boryschuk, A.V. Strieby Crouch, W.K. Kwok, J.E. Schirbe, D.L. Overmyer, D. Jung, M.H. Whangbo, Inorg. Chem. 29 ( 1990) 3262. J.J. Novoa, M.C. Rovira, C. Rovira, J. Veciana, J. Tar&, Adv. Mater. 7 (1995) 233. M.C. Rovira, J.J. Novoa, J. Tarn%, C. Rovira, J. Veciana, S. Yang, D.O. Cowan, E. Canadell, Adv. Mater. 7 ( 1995) 1023. P. Hudhomme, P. Blanchard, M. Salle, S. Le Moustarder, A. Riou, M. Jubault, A. Gorgues, G. Duguay, Angew. Chem., Int. Ed. Engl. 36 ( 1997) 878. J.M. Williams, J.R. Ferraro, R.J. Thorn, K.D. Carlson, U. Geiser,H.H. Wang, A.M. Kini, M.H. Whangbo, Organic Superconductors (Including Fullerenes), Prentice-Hall, Englewood Cliffs, NJ, 1992. C. Livage, M. Fourmigut, P. Batail, E. Canadell, C. Coulon, Bull. Sot. Chim. Fr. 130 (1993) 761. K.A. Abboud, M.B. Clavenger, G.F. de Oliviera, D.R. Talham, J. Chem. Sot., Chem. Commun. ( 1993) 1560. L. Ouahab, M. Fettouhi, J.F. Halet, V.M. Yartsev, C. GarrigouLagrange, P. Delhaes, C. Sourisseau, New J. Chem. 17 ( 1993) 399.