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Synthesis and properties of new PDT- and TPDT-TTP analogues
ELSEVIER
Synthetic
Metals
102 (1999)
1621-1622
Synthesis and properties of new PDT- and TPDT-‘ITP analogues *Division
T. Kaibuk?, Y. MisakP*, K. Tanaka’, K. Takimiyab, A. Morikam?, T. Otsubob of Molecular Engineering, Gradwte School of Engineering, Kyoto University, Yoshida, Kyoto 6068501, bDepartment of Applied Chemistry, Faculty of Engineering, Hiroshima Universiq, 1-4-I Kagamiyama, Higashi-Hiroshima 739-8527, Japan
Japan
Abstract 2-(1,3-Diselenol-2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDS-TTP), its thiopyran analogue (TPDS-TIP), and their bis(methylthio) derivatives have been prepared. Their first and second oxidation potentials are comparable to those of the corresponding sulfur analogues. The PF, and AsF, salt of PDS-lTP displayed metallic conductivity down to 4.2 K, and ‘ICNQ complex was semiconductor with a low activation energy (0.006 eV). keywords:
Organic conductors
based on radical cation and/or anion salts, Electrochemical
1. Introduction
2. Results
For design of donor molecules which afford metallic salts, enhancement of conductive dimension has been regarded to be important. We have synthesized a large number of BDT-TIP (2,5-bis(l,3-dithiol-2-ylidene)-1,3,4,6-tetrathia pentalene) derivatives. Many of them have afforded cation radical salts behaving metallic temperature dependence, in which the donors form two-dimensional conducting sheet through intermolecular S*=*S contacts [ 11. Several lTP analogues possessing non-‘ITF moiety have been also synthesized so far [2-41. Among them, 2-( 1,3-dithiol2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDT-TIP, 1 a) and its thiopyran analogue (TPDT-TTP, 2 a) arc of interest [2]. Thus, the TCNQ complex and several salts of ethylenedithio-PDT-TIP showed metallic behavior down to 4.2 K, while the unsubstituted compounds 1 a and 2 a have afforded no metallic salts. To stabilize metallic state, replacement of sulfur atoms in 1,3-dithiole ring with selenium is a promising strategy because more intermolecular interactions thanks to larger van der Waals radius of selenium are expected. In these Proceedings we report synthesis and electrochemical properties of selenium analogues of 1 and 2, PDS-TlT (3a). TPDS-TIP (4 a) and their methylthio derivatives (3 c, 4 c). Furthermore, conducting properties of their salts are also described.
2.1. Synthesis
la; X=0, Y=S, R=H 3a; X=0, k; X=0,
Y=Se, Y=Se,
R=H R=SMe
2a; X=S, Y=S, R=H 4a; X=S, Y=Se, R=H 4c; X=S, Y=Se, R=SMe
0 1999 Elsevier
Science
S.A.
and Discussion
The synthetic route for the known PDT-TIP and TPDT-TIP derivatives [3] is applicable to their selenium analogues, but a little improved method was adopted at this time as shown in Scheme 1. The first step of this procedure is dehydrogenation of the compounds 5, 6 by using 2,3-dichloro-5,6-dicyano-1,4-quinone @IQ) [4]. The compounds 7, 8 and 9 b were cross-coupled in neat trimethylphosphite-toluene (l:l, v/v) at 90 “C to afford the Scheme 1 o=Ie 5, x=0 6, X-s DDQ
All rights reservea.
xylene reflux 1
~I+
3b, X=0,52% 4b. X=S, 41%
*Dr. Y. Misaki telephone; +8175 753 5933, fax; +8175 771 0172 atnail; misakiG&nee3.moleng.kyoto-u.ac.jp Acknowledgement; This work is partially supported by Grant-in-Aid for Scientific Research No. 09640687 and by Japan Society for the Promotion of Science-Research for the Future Program (BPS-RiTF96P00206). 0379-6779/99/$ - see front matter PII: SO379-6779(98)00469-X
methods, Electrocrystalization
3a, X=0,88% 4a, X=S, 58%
1622
i? Kaibuki
et al. I Synthetic
Table 1. Redox potentials of 3 and 4 in PhCN (v vs. AgJAg+, 25 “C) El E4 E2 E3 Ema) 3a +0.03 +0.24 -c) 3c +o.os +0.32 +0.54 +0.74 4a -0.01 +0.26 +0.59 +0.72 4c 0.00 +0.31 +0.61 +0.81 la +0.03 iO.23 +0.74b) 2a -0.02 +0.25 +0.63 +0.82 a) Em=(E3+Eq)/2. b) Irreversible step. Anodic peak c) Not clearly observed. Table 2. Electrical Donor 3a
102 (1999)
1621-1622
Ez-EI 0.21 0.28 0.27 0.31 0.20 0.27 potential.
0
100
200
300
‘I’(K) Fig. 1 Conducting
behavior
of PF, salt of 3 a
of TCNQ Complex and Cation Radical Salts, Donor(A)x Form Ea IeV xa) crfi /S cm-lc) mQ .ob) ld) 0.006 1 13 0.49b) O.sd) 0.034 BF4 Plate 4 0.026 A&j Needle 0.74( As) 20 Metallic down to 4.2 K SbF6 Needle 0.66(Sb) 0.3 0.017 Metallic down to 4.2 K Needle 0.50(P) 300 PF6 mQ .ob) 2d) 0.010 1 13 0.55b) 5d) 0.019 Cl04 Plate 0.61(Cl) 20 0.009 Plate 0.42(P) 10 TM-I = 250 K PF6 SbF6 Needle 0.48(Sb) 50 0.029 ASF6 Needle 0.95(As) 80 0.027 0.076 Needle 0.49(P) 30 PF6 by the energy dispersion spectroscopy from the ratio of sulfur and the elements designated in the parentheses. based on elemental analyses. c) Measured on a single crystal. d) Measured on a compressed pellet.
4a
3c
a) Determined b) Determined
Properties Acceptor
compounds 3 b and 4 b. In a similar manner, the compounds 3 c and 4 c were obtained by cross-coupling between 7, 8 and 9 c. These cross-coupling products were obtained in moderate yields of 29-52 %. The unsubstituted derivatives 3 a and 4 a were obtained by heating of 3 b and 4 b with an excess of Liir*H,O in hexamethylphosphoramide (HMPA) at 90-130 “C in 88 and 58 % yields respectively. 2.2. Electrochemical
properties
The electrochemical properties of new donors were investigated by cyclic voltammetry. The cyclic voltammograms of 3 and 4 except for 3 a in PhCN show four pairs of single-electron redox waves. Their redox potentials are summarized in Table 1. The first and second oxidation potentials of 3 a and 4a are comparable to those of the corresponding sulfur analogues. This result indicates that the donating ability does not change by introduction of selenium atoms. On the other hand, on-site Coulomb repulsions in the dicationic states of 3 a and 4 a estimated based on K-E, values are also comparable to the corresponding sulfur analogues. 2.2. Conducting
Metals
properties
The electrical conductivities of charge-transfer salts and cation radical salts of 3 a, c and 4 a were measured using the four-probe technique with gold paste contacts. lbe results are
shown in Table 2. Most of the salts shows fairly high electrical conductivities of lo-‘- IO* S cm-’ at room temperature, several of which exhibit metallic conductive behavior. Among them, the PF, salt and AsF, salt of 3 a are metallic down to 4.2 K (Fig 1). On the other hand, TCNQcomplexes and I, salts of 3 a and 4a measured on a compressed pellet show semiconductive temperature dependence of conductivities. However their activation energies (E,=lO-‘-10.’ eV) are very small, suggesting that they are expected to exhibit metallic conductive behavior on a single crystal. 3. Reference [l] (a) Y. Misaki, H. Nishikawa, K. Kawakami, S. Koyanagi, T. Yamabe, M. Shire, Chem. Lett. (1992) 2321. (b) Y. Misaki, H. Nishikawa, T. Yamabe, T. Mori, H. Inokuchi, H. Mori, S. Tanaka, Chem. Lett. (1993) 729. [2] Y. Misaki, H. Fujiwara, T. Maruyama, T. Yamabe, Synth. Met. 70( 1995)1147. [3] Y. Misaki, T. Sasaki, T. Ohta, H. Fujiwara, T. Yamabe, Adv. Mater. 8(1996) 804. [4] Y. Misaki, N. Higuchi, H. Fujiwara, T. Yamabe, T. Mori, H. Mori, S. Tanaka, Angew. Chem. Int. Ed. Engl. 34 (1995)1222. [5] Y. Misaki, H. Fujiwara, T. Yamabe, J. Org. Chem. 6 1 (1996) 3650. [6] H. Fujiwara, Y. Misaki, T. Yamabe, unpublished results.
Synthetic
Metals
102 (1999)
1621-1622
Synthesis and properties of new PDT- and TPDT-‘ITP analogues *Division
T. Kaibuk?, Y. MisakP*, K. Tanaka’, K. Takimiyab, A. Morikam?, T. Otsubob of Molecular Engineering, Gradwte School of Engineering, Kyoto University, Yoshida, Kyoto 6068501, bDepartment of Applied Chemistry, Faculty of Engineering, Hiroshima Universiq, 1-4-I Kagamiyama, Higashi-Hiroshima 739-8527, Japan
Japan
Abstract 2-(1,3-Diselenol-2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDS-TTP), its thiopyran analogue (TPDS-TIP), and their bis(methylthio) derivatives have been prepared. Their first and second oxidation potentials are comparable to those of the corresponding sulfur analogues. The PF, and AsF, salt of PDS-lTP displayed metallic conductivity down to 4.2 K, and ‘ICNQ complex was semiconductor with a low activation energy (0.006 eV). keywords:
Organic conductors
based on radical cation and/or anion salts, Electrochemical
1. Introduction
2. Results
For design of donor molecules which afford metallic salts, enhancement of conductive dimension has been regarded to be important. We have synthesized a large number of BDT-TIP (2,5-bis(l,3-dithiol-2-ylidene)-1,3,4,6-tetrathia pentalene) derivatives. Many of them have afforded cation radical salts behaving metallic temperature dependence, in which the donors form two-dimensional conducting sheet through intermolecular S*=*S contacts [ 11. Several lTP analogues possessing non-‘ITF moiety have been also synthesized so far [2-41. Among them, 2-( 1,3-dithiol2-ylidene)-5-(pyran-4-ylidene)-1,3,4,6-tetrathiapentalene (PDT-TIP, 1 a) and its thiopyran analogue (TPDT-TTP, 2 a) arc of interest [2]. Thus, the TCNQ complex and several salts of ethylenedithio-PDT-TIP showed metallic behavior down to 4.2 K, while the unsubstituted compounds 1 a and 2 a have afforded no metallic salts. To stabilize metallic state, replacement of sulfur atoms in 1,3-dithiole ring with selenium is a promising strategy because more intermolecular interactions thanks to larger van der Waals radius of selenium are expected. In these Proceedings we report synthesis and electrochemical properties of selenium analogues of 1 and 2, PDS-TlT (3a). TPDS-TIP (4 a) and their methylthio derivatives (3 c, 4 c). Furthermore, conducting properties of their salts are also described.
2.1. Synthesis
la; X=0, Y=S, R=H 3a; X=0, k; X=0,
Y=Se, Y=Se,
R=H R=SMe
2a; X=S, Y=S, R=H 4a; X=S, Y=Se, R=H 4c; X=S, Y=Se, R=SMe
0 1999 Elsevier
Science
S.A.
and Discussion
The synthetic route for the known PDT-TIP and TPDT-TIP derivatives [3] is applicable to their selenium analogues, but a little improved method was adopted at this time as shown in Scheme 1. The first step of this procedure is dehydrogenation of the compounds 5, 6 by using 2,3-dichloro-5,6-dicyano-1,4-quinone @IQ) [4]. The compounds 7, 8 and 9 b were cross-coupled in neat trimethylphosphite-toluene (l:l, v/v) at 90 “C to afford the Scheme 1 o=Ie 5, x=0 6, X-s DDQ
All rights reservea.
xylene reflux 1
~I+
3b, X=0,52% 4b. X=S, 41%
*Dr. Y. Misaki telephone; +8175 753 5933, fax; +8175 771 0172 atnail; misakiG&nee3.moleng.kyoto-u.ac.jp Acknowledgement; This work is partially supported by Grant-in-Aid for Scientific Research No. 09640687 and by Japan Society for the Promotion of Science-Research for the Future Program (BPS-RiTF96P00206). 0379-6779/99/$ - see front matter PII: SO379-6779(98)00469-X
methods, Electrocrystalization
3a, X=0,88% 4a, X=S, 58%
1622
i? Kaibuki
et al. I Synthetic
Table 1. Redox potentials of 3 and 4 in PhCN (v vs. AgJAg+, 25 “C) El E4 E2 E3 Ema) 3a +0.03 +0.24 -c) 3c +o.os +0.32 +0.54 +0.74 4a -0.01 +0.26 +0.59 +0.72 4c 0.00 +0.31 +0.61 +0.81 la +0.03 iO.23 +0.74b) 2a -0.02 +0.25 +0.63 +0.82 a) Em=(E3+Eq)/2. b) Irreversible step. Anodic peak c) Not clearly observed. Table 2. Electrical Donor 3a
102 (1999)
1621-1622
Ez-EI 0.21 0.28 0.27 0.31 0.20 0.27 potential.
0
100
200
300
‘I’(K) Fig. 1 Conducting
behavior
of PF, salt of 3 a
of TCNQ Complex and Cation Radical Salts, Donor(A)x Form Ea IeV xa) crfi /S cm-lc) mQ .ob) ld) 0.006 1 13 0.49b) O.sd) 0.034 BF4 Plate 4 0.026 A&j Needle 0.74( As) 20 Metallic down to 4.2 K SbF6 Needle 0.66(Sb) 0.3 0.017 Metallic down to 4.2 K Needle 0.50(P) 300 PF6 mQ .ob) 2d) 0.010 1 13 0.55b) 5d) 0.019 Cl04 Plate 0.61(Cl) 20 0.009 Plate 0.42(P) 10 TM-I = 250 K PF6 SbF6 Needle 0.48(Sb) 50 0.029 ASF6 Needle 0.95(As) 80 0.027 0.076 Needle 0.49(P) 30 PF6 by the energy dispersion spectroscopy from the ratio of sulfur and the elements designated in the parentheses. based on elemental analyses. c) Measured on a single crystal. d) Measured on a compressed pellet.
4a
3c
a) Determined b) Determined
Properties Acceptor
compounds 3 b and 4 b. In a similar manner, the compounds 3 c and 4 c were obtained by cross-coupling between 7, 8 and 9 c. These cross-coupling products were obtained in moderate yields of 29-52 %. The unsubstituted derivatives 3 a and 4 a were obtained by heating of 3 b and 4 b with an excess of Liir*H,O in hexamethylphosphoramide (HMPA) at 90-130 “C in 88 and 58 % yields respectively. 2.2. Electrochemical
properties
The electrochemical properties of new donors were investigated by cyclic voltammetry. The cyclic voltammograms of 3 and 4 except for 3 a in PhCN show four pairs of single-electron redox waves. Their redox potentials are summarized in Table 1. The first and second oxidation potentials of 3 a and 4a are comparable to those of the corresponding sulfur analogues. This result indicates that the donating ability does not change by introduction of selenium atoms. On the other hand, on-site Coulomb repulsions in the dicationic states of 3 a and 4 a estimated based on K-E, values are also comparable to the corresponding sulfur analogues. 2.2. Conducting
Metals
properties
The electrical conductivities of charge-transfer salts and cation radical salts of 3 a, c and 4 a were measured using the four-probe technique with gold paste contacts. lbe results are
shown in Table 2. Most of the salts shows fairly high electrical conductivities of lo-‘- IO* S cm-’ at room temperature, several of which exhibit metallic conductive behavior. Among them, the PF, salt and AsF, salt of 3 a are metallic down to 4.2 K (Fig 1). On the other hand, TCNQcomplexes and I, salts of 3 a and 4a measured on a compressed pellet show semiconductive temperature dependence of conductivities. However their activation energies (E,=lO-‘-10.’ eV) are very small, suggesting that they are expected to exhibit metallic conductive behavior on a single crystal. 3. Reference [l] (a) Y. Misaki, H. Nishikawa, K. Kawakami, S. Koyanagi, T. Yamabe, M. Shire, Chem. Lett. (1992) 2321. (b) Y. Misaki, H. Nishikawa, T. Yamabe, T. Mori, H. Inokuchi, H. Mori, S. Tanaka, Chem. Lett. (1993) 729. [2] Y. Misaki, H. Fujiwara, T. Maruyama, T. Yamabe, Synth. Met. 70( 1995)1147. [3] Y. Misaki, T. Sasaki, T. Ohta, H. Fujiwara, T. Yamabe, Adv. Mater. 8(1996) 804. [4] Y. Misaki, N. Higuchi, H. Fujiwara, T. Yamabe, T. Mori, H. Mori, S. Tanaka, Angew. Chem. Int. Ed. Engl. 34 (1995)1222. [5] Y. Misaki, H. Fujiwara, T. Yamabe, J. Org. Chem. 6 1 (1996) 3650. [6] H. Fujiwara, Y. Misaki, T. Yamabe, unpublished results.