3419-99-6Relevant academic research and scientific papers
Structure and Stability of Quaternary Ammonium Interhalides: Experimental and Quantum-Chemical Study
Simonyan,Kletskii,Chernov'yants,Gol'eva
, p. 575 - 582 (2007/10/03)
The electronic structure of a series of ammonium interhalides [R 1R2R3R4N]XI2, where R1 = CH3, C2H5, C3H 7, F, H; R2 = R3 = R4 = CH 3, H; X = Cl, Br, I, was studied by ab initio calculations (RHF/3-21G, RHF/HW, MP2/HW). The thermodynamic stability of these compounds correlates with the strength of the hydrogen bond N-H...X and three-center interhalide bond X-I-I. Calculations confirmed that, in polar solvents, these compounds preferably decompose to [R1R2R3R 4N]+ and XI2- (with subsequent decomposition of the anion), and in nonpolar solvents, to the neutral species [R1R2R3R4N]X and I2. The calculation results were compared to the experimental data obtained by single crystal X-ray diffraction, 1H NMR spectroscopy, and spectrophotometry.
Correlations of Anion Size and Symmetry with the Structure and Electronic Properties of β-(BEDT-TTF)2X Conducting Salts with Trihalide Anions X=I3(1-), I2Br(1-), IBr2(1-)
Emge, Thomas J.,Leung, Peter C. W.,Beno, Mark A.,Wang, Hau H.,Firestone, M. A.,et al.
, p. 363 - 384 (2007/10/02)
In the isostructural series of β-(BEDT-TTF)2X organic metals, abbreviated β-(ET)2X, where X is a trihalide anion, I3(1-), I2Br(1-) or IBr2(1-), and where ET is bis-(ethylenedithio)tetrathiafulvalene (C10S8H8), the salt containing the disordered asymmetric I2Br(1-) anion has atypical structural and electronic properties compared to those containing the symmetrical and ordered I3(1-) and IBr2(1-) anions.Ambient pressure superconductivity has been detected in the salts containing the symmetrical anions, viz. β-(ET)2I3 (Tc=1.4 K) and β-(ET)2IBr2 (Tc=2.8 K), but not in that which contains the asymmetric anion, β-(ET)2I2Br, even though the I2Br(1-) anion is of length intermediate between I3(1-) and IBr2(1-).Low field esr measurements reveal that the metallic state in β-(ET)2I2Br persists to 1.07 K and also up to 5 kbar pressure.The absence of superconductivity, even under modest pressure, appears to be the result of the disordering of the I2Br(1-) anion.For these three isostructural β-(ET)2X salts, the crystal packing of the ET molecules consists of a tightly packed two-dimensional network, with interstack S...S contacts that are often less than the van der Waals radii sum of 3.60 Angstroem, and H...X interactions (X=I or Br) that serve to connect the cation networks with the anions that reside between the networks.Correlations between anion size and the intermolecular S...S and H...X distances are discussed.Unit cell lattice parameters (298/120 K) for these three isostructural salts (space group P1, Z=1) are for β-(ET)2I3: a=6.615(1)/6.561(1) Angstroem, b=9.100(1)/9.013(2) Angstroem, c=15.286(2)/15.173(2) Angstroem, α=94.38(1)/95.07(1) deg, β=95.59(1)/95.93(1) deg, γ=109.78(1)/110.28(1) deg, V=855.9(2)/829.2(3) Angstroem3; for β-(ET)2I2Br: a=6.612(1)/6.613(1) Angstroem, b=9.024(2)/8.873(2) Angstroem, c=15.192(2)/15.100(2) Angstroem, α=94.16(1)/95.64(1) deg, β=95.23(1)/95.15(1) deg, γ=110.12(1)/109.79(1) deg, V=842.3(3)/822.4(2) Angstroem3; and for β-(ET)2IBr2: a=6.593(1)/6.589(1) Angstroem, b=8.975(2)/8.820(2) Angstroem, c=15.093(5)/14.988(5) Angstroem, α=93.79(2)/95.30(2) deg, β=94.96(2)/94.87(2) deg, γ=110.54(2)/110.28(2) deg, V=828.7(5)/807.1(5) Angstroem3. - Keywords: organic metals, ET-based, anion size, structures
