New Molecular Charge Transfer Salts of BEDT-TTF, Bis(ethylenedithio) Tetrathiafulvalene, with Thiocyanato-Complex Anions: (BEDT-TTF)4[Fe(NCS)6]·CH2Cl2 and (BEDT-TTF)2[Cr(NCS)4(bipym)]·0.15H2O
✍ Scribed by Scott S. Turner; Peter Day; Thomas Gelbrich; Michael B. Hursthouse
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 341 KB
- Volume
- 159
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Two new charge transfer salts of BEDT-TTF, bis (ethylenedithio) tetrathiafulvalene, with thiocyanato-metal complex anions have been synthesized and characterized as (BEDT-TTF) 4 [Fe(NCS) 6 ] ' CH 2 Cl 2 and (BEDT-TTF) 2 [Cr(NCS) 4 (bipym)] ' 0.15H 2 O, where bipym ؍ 2,2-bipyrimidine. The Fe salt, I, crystallizes in the P-1 (No. 2) space group at 150 K with a ؍ 10.629(1) A s , b ؍ 12.099(1) A s , c ؍ 16.062(2) A s , ؍ 99.61(1)3, ؍ 90.87(1)3, ؍ 112.92(1)3, and V ؍ 1868.5(6) A s 3 . At 150 K the Cr salt, II, crystallizes in the P-1 (No. 2) space group with a ؍ 9.243(2), b ؍ 11.781(2), c ؍ 22.925(5) A s , ؍ 93.76(3), ؍ 101.51(3), ؍ 105.45
(3)3, V ؍ 2339.0(8) A s 3 , and Z ؍ 2. Both salts exhibit close S2S contacts between the anion and cation components and in II there is no -stacking between the bipym group and the BEDT-TTF molecules. Both salts are paramagnetic with C ؍ 4.926 I and C ؍ 1.819 II with small negative Weiss constants of ؊ 0.19 and ؊ 0.26, respectively. Therefore, the S2S contacts alone do not promote correlated magnetic e4ects as seen in other thiocyanato salts that also contain -stacking. Each compound is a semiconductor and has two crystallographically independent BEDT-TTF molecules for which bond length analysis give charges of ؉ 0.9 ؎ 0.1/؉ 0.6 ؎ 0.1 for I and ؉ 0.3 ؎ 0.1/ ؉ 0.9 ؎ 0.1 for II.