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Synthesis, structure and properties of novel TTF dimers bridged by two trisulfide chains
ELSEVIER
Synthetic
Metals
102 (1999)
1739
Synthesis, structure and properties of novel TTF dimers bridged by two trisulfide chains H. Fujiwara, Institute for Molecular
E. Arai, H. Kobayashi
Science, Myodaiji,
Okazaki 444-8585,
Japan
Abstract We synthesized novel TTF dimer molecules in which two ITF moieties are connected to each other by two trisulfide chains. Structure of tetrakis(methylthio) derivative 1 is cyclophane-like one and interplanar distance in the dimer is 3.86 A. 1 shows two pairs of reversible one-electron redox waves (+0.57 and +0.67 V vs. Ag/AgCl in PhCN) and one pair of reversible two-electron redox wave (+1.15 V). The ClO4- salt of 1 has 1:2 (Donor:Anion) composition and is an insulator. On the other hand the PF6‘ salt of bis(trimethylene) derivative 2 has one-dimensional columnar donor array with 1:l composition and shows semiconducting behavior (qt = 10-l Scm-l). Keywords:
Electrochemical
methods, Conductivity,
Organic
conductors
1.
Introduction Synthesis of tetrathiafulvalenophane has been first reported in 1980 and extensively developed in 1990’s because of its unusual molecular structure and interesting intramolecular interaction [I]. We focused on a polysulfide chain as a bridging chain because it has more rigid framework than that of polymethylene chain and large interplanar interaction between two TTF moieties may be realized in a dimer. We report here the synthesis and structure of a novel cyclophane-like trisulfide-bridged mF dimers 1, 2 in which two TTF moieties are connected to each other by two trisulfide chains [2].
1 R=.SMe 2 2R = -(CH&
2.
Results and Discussion The synthesis of TTF dimers were performed by the following method. The corresponding 4,5-bis(2’cyanoethylthio)-TTF derivatives [3] were hydrolyzed with 28 wt% methanol solution of sodium methoxide in dry acetonitrile I methanol at room temperature and successively treated with zinc chloride and tetra-n-butylammonium bromide to generate the corresponding zinc dithiolene complexes, which were finally reacted with sulfur dichloride in dry acetonitrile at 55 “C. The crude product were purified by column chromatography (silica gel, carbon disulfide) and recrystallized from chlorobenzene to afford air-stable black plate-like crystals in 17 % yield. X-Ray crystal structure analysis of bis(methylthio) derivative 1 revealed that 1 has a cyclophane-like U-shape structure (Fig. la). Each two TTF moieties have planar but slightly bent structure with dihedral angles of 16.4 and 24.1”. They stack to each other in a ringover-bond like overlap mode with a intradimer interplanar distance of 3.86 A. The TTF dimer 1 shows two pairs of
based on radical
cation salts
reversible one-electron redox waves (+0.57 and +0.67 V vs. Ag/AgCl in PhCN) and one pair of reversible two-electron redox wave (+1.15 V). The first and second oxidation processes are separated with interval of 0.1 V, suggesting the existence of intradimer interaction between two TTF moieties. Preparation of cation radical salts was performed by electrochemical oxidation in THF or chlorobenzene. The composition of the ClO4- salt of 1 from THF is 1:2 (DonocAnion) and donors are in the dicationic state. TTF moieties have planar structure and eclipse almost perfectly to each other with comparatively short interplanar distance of 3.39 8, compared to that of neutral one (3.86 A) (Fig.lb). Each dimers are almost separated by the counter anions and the interaction between donors exists only through the sulfur atoms of methylthio groups in the direction of the molecular long axis. Because of the dicationic state of donors and its mixed stacking crystal structure, this ClO4- salt appeared to be an insulator. On the other hand the PF6- salt of bis(trimethylene) derivative 2 was prepared in chlorobenzene. It has one-dimensional columnar donor arrays of the dimer molecules along a-axis with I:1 composition of D:A and shows semiconducting behavior with qt = 10-l Scm-l. (4
(b)
Fig. 1. Molecular structures of 1; (a) the neutral state and (b) the dicationic state in the ClO4- salt. References [ 1] T. Otsubo et al., Adv. Mater. 8 (1996) 203. [2] H. Fujiwara et al., J. Mater. Chem. 8 (1998) 829. [3] N. Svenstrup et al., Synthesis (1994) 809.
0379-6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved. PII: SO379-6779(98)00943-6
Synthetic
Metals
102 (1999)
1739
Synthesis, structure and properties of novel TTF dimers bridged by two trisulfide chains H. Fujiwara, Institute for Molecular
E. Arai, H. Kobayashi
Science, Myodaiji,
Okazaki 444-8585,
Japan
Abstract We synthesized novel TTF dimer molecules in which two ITF moieties are connected to each other by two trisulfide chains. Structure of tetrakis(methylthio) derivative 1 is cyclophane-like one and interplanar distance in the dimer is 3.86 A. 1 shows two pairs of reversible one-electron redox waves (+0.57 and +0.67 V vs. Ag/AgCl in PhCN) and one pair of reversible two-electron redox wave (+1.15 V). The ClO4- salt of 1 has 1:2 (Donor:Anion) composition and is an insulator. On the other hand the PF6‘ salt of bis(trimethylene) derivative 2 has one-dimensional columnar donor array with 1:l composition and shows semiconducting behavior (qt = 10-l Scm-l). Keywords:
Electrochemical
methods, Conductivity,
Organic
conductors
1.
Introduction Synthesis of tetrathiafulvalenophane has been first reported in 1980 and extensively developed in 1990’s because of its unusual molecular structure and interesting intramolecular interaction [I]. We focused on a polysulfide chain as a bridging chain because it has more rigid framework than that of polymethylene chain and large interplanar interaction between two TTF moieties may be realized in a dimer. We report here the synthesis and structure of a novel cyclophane-like trisulfide-bridged mF dimers 1, 2 in which two TTF moieties are connected to each other by two trisulfide chains [2].
1 R=.SMe 2 2R = -(CH&
2.
Results and Discussion The synthesis of TTF dimers were performed by the following method. The corresponding 4,5-bis(2’cyanoethylthio)-TTF derivatives [3] were hydrolyzed with 28 wt% methanol solution of sodium methoxide in dry acetonitrile I methanol at room temperature and successively treated with zinc chloride and tetra-n-butylammonium bromide to generate the corresponding zinc dithiolene complexes, which were finally reacted with sulfur dichloride in dry acetonitrile at 55 “C. The crude product were purified by column chromatography (silica gel, carbon disulfide) and recrystallized from chlorobenzene to afford air-stable black plate-like crystals in 17 % yield. X-Ray crystal structure analysis of bis(methylthio) derivative 1 revealed that 1 has a cyclophane-like U-shape structure (Fig. la). Each two TTF moieties have planar but slightly bent structure with dihedral angles of 16.4 and 24.1”. They stack to each other in a ringover-bond like overlap mode with a intradimer interplanar distance of 3.86 A. The TTF dimer 1 shows two pairs of
based on radical
cation salts
reversible one-electron redox waves (+0.57 and +0.67 V vs. Ag/AgCl in PhCN) and one pair of reversible two-electron redox wave (+1.15 V). The first and second oxidation processes are separated with interval of 0.1 V, suggesting the existence of intradimer interaction between two TTF moieties. Preparation of cation radical salts was performed by electrochemical oxidation in THF or chlorobenzene. The composition of the ClO4- salt of 1 from THF is 1:2 (DonocAnion) and donors are in the dicationic state. TTF moieties have planar structure and eclipse almost perfectly to each other with comparatively short interplanar distance of 3.39 8, compared to that of neutral one (3.86 A) (Fig.lb). Each dimers are almost separated by the counter anions and the interaction between donors exists only through the sulfur atoms of methylthio groups in the direction of the molecular long axis. Because of the dicationic state of donors and its mixed stacking crystal structure, this ClO4- salt appeared to be an insulator. On the other hand the PF6- salt of bis(trimethylene) derivative 2 was prepared in chlorobenzene. It has one-dimensional columnar donor arrays of the dimer molecules along a-axis with I:1 composition of D:A and shows semiconducting behavior with qt = 10-l Scm-l. (4
(b)
Fig. 1. Molecular structures of 1; (a) the neutral state and (b) the dicationic state in the ClO4- salt. References [ 1] T. Otsubo et al., Adv. Mater. 8 (1996) 203. [2] H. Fujiwara et al., J. Mater. Chem. 8 (1998) 829. [3] N. Svenstrup et al., Synthesis (1994) 809.
0379-6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved. PII: SO379-6779(98)00943-6