207462-35-9Relevant academic research and scientific papers
Synthesis, electrochemistry, structure, and magnetic susceptibility of 5-tert-butyl-1,3-bis-(1,2,3,5-dithiadiazolyl)benzene. Structural effect of the bulky substituent
Beekman, Richard A.,Boere, Rene T.,Moock, Klaus H.,Parvez, Masood
, p. 85 - 93 (1998)
The crystal structure of the title compound was determined at 250 K in space group I42m, a = 20.661(5) A, c = 6.764(7) A, Z = 8. The individual dithiadiazole rings form two sets of contrarotatory 4-member pinwheels clustered around a 4-fold rotation-inversion axis located halfway along the unit cell edges, describing an infinite channel lined with sulfur atoms but in which there are short intra-stack contacts through only one S atom of each CN2S2 group. The double-layer stacking occurs in order to accommodate the bulk of the fBu group, and the spacing between layers is very regular, with short and long S...S contacts of 3.48(2) and 3.61(2) A and considerable thermal motion in the c direction. The title compound and its SbF6- salt are oxidized at +0.81 V (in CH2Cl2) and at +0.61 V (in CH3CN), while a reduction process is observed only in CH2Cl2 at -0.73 V vs. SCE. Magnetic susceptibility data between 5 and 400 K demonstrate at very low temperature that the sample follows the Curie-Weiss law, θ = 0 K, and χ0 = -156 ppm emu mol-1. The free-spin concentration at T= 0 K is ≈1.3%, due to paramagnetic defects in an essentially diamagnetic structure. The diamagnetism starts to lift above 210 K; above 260 K, a strong antiferromagnetic exchange is operative. These results are consistent with the lifting of the Peierls distortion in this structure, starting above ≈200 K. The crystal structure of the parent diamidine 5-tert-butyl-1,3-[(Me3Si)2NCNSiMe3] 2C6H3 was determined in C2/c with a = 10.0788(3), b = 21.328(5), c = 20.876(5) A, β = 99.41(2)°, Z = 4. The two amidine functional groups are equivalent by crystal symmetry.
