Hindered molecular reorientation of lithium ion doped succinonitrile in the terahertz range
The THz range permittivity of succinonitrile exhibits Debye-like behavior in its plastic-crystal phase, with a characteristic Cole-Cole relaxation time of 65ps ±17ps which increases considerably in the presence of ionic dopants.
Dielectric relaxation spectroscopy for evaluation of the influence of solvent dynamics on ion transport in succinonitrile-salt plastic crystalline electrolytes.
Influence of succinonitrile (SN) dynamics on ion transport in SN-lithium perchlorate (LiClO(4)) electrolytes is discussed here via dielectric relaxation spectroscopy. Dielectric relaxation spectroscopy (∼2×10(-3) Hz to 3 MHz) of SN and SN-LiClO(4) was studied as a function of salt content (up to 7 mol % or 1 M) and temperature (-20 to +60 °C). Analyses of real and imaginary parts of permittivity convincingly reveal the influence of trans-gauche isomerism and solvent-salt association (solvation) effects on ion transport. The relaxation processes are highly dependent on the salt concentration and temperature. While pristine SN display only intrinsic dynamics (i.e., trans-gauche isomerism) which enhances with an increase in temperature, SN-LiClO(4) electrolytes especially at high salt concentrations (∼0.04-1 M) show salt-induced relaxation processes. In the concentrated electrolytes, the intrinsic dynamics was observed to be a function of salt content, becoming faster with an increase in salt concentration. Deconvolution of the imaginary part of the permittivity spectra using Havriliak-Negami (HN) function show a relaxation process corresponding to the above phenomena. The permittivity data analyzed using HN and Kohlrausch-Williams-Watta (KWW) functions show non-Debye relaxation processes and enhancement in the trans phase (enhanced solvent dynamics) as a function of salt concentration and temperature.
Conformation and molecular structure of pentanedinitrile (1,3-dicyanopropane) using gas-phase electron diffraction
Abstract Pentanedinitrile (NC-CH 2 -CH 2 -CH 2 -CN) has been studied by gas-phase electron diffraction (ED) at 448 K. At this temperature the molecules exist as a mixture of about equal parts [ X =0.5(0.2)] of the two conformers AG (having one CN group anti and the other gauche to the central CCC skeleton) and GG (having both CN groups gauche to the CCC skeleton). Assuming that the two conformers differ in their geometries only in their torsion angels o 2–3 and o 3–4 , some of the important distance ( r a ) and angle ∠ α parameters are: r (CC) = 1.544(5), r (CC) = 1.463(4), r (CN) = 1.161(3), r (CH) = 1.105(9) A, ∠ CCC = 110.5(1.1)° and ∠CCC=111.2 (0.5)°. The torsion angles, relative to o 2–3 =o 3–4 =0° for the AA form, are o 2–3 =0° and o 3–4 =114(6)° for AG , while for GG both torsion angles are equal to 114(6)°. Uncertainties are given as 2σ, where σ includes uncertainty due to correlation among observations and parameters used in the data reduction. A small amount of a third conformer AA , which cannot be ruled out conclusively from the ED data, was not detected in the analysis.