Crystal structure and thermal decomposition kinetics of 1-(pyridinium-1-yl)propane-(1-methylpiperidinium) bi[bis(trifluoromethanesulfonyl)imide], [PyC3Pi][NTf2]2

The structure of a room temperature asymmetrical dicationic ionic liquid (ADIL), 1-(pyridinium-1-yl) propane-(1-methylpiperidinium) bi[bis(trifluoromethanesulfonyl)imide] ([PyC3Pi][NTf2]2), was studied by the X-ray diffraction method. Meanwhile, thermal analysis of [PyC3Pi][NTf2]2 was also studied using non-isothermal thermogravimetric analysis (TGA). The title crystal belongs to the triclinic with space group Pī and unit-cell parameters a = 0.95217 (8) nm, b = 1.05129 (11) nm, c = 1.70523 (14) nm, α = 89.759 (8)°, β = 80.657 (7)°, γ = 68.007 (9)°, and F(000) = 792. Thermal stability and thermal decomposition kinetics of the title compound were also investigated using TGA under the atmosphere of highly pure nitrogen. Heating curves at different rates were correlated with kinetic equations Friedman and ASTM (also called iso-conversion method). The values of average activation E (kJ·mol− 1) and pre-exponential constant lgA are 149.58 kJ·mol− 1 and 8.83, respectively, which were obtained by the two methods. The kinetic model function, activation energy and pre-exponential constant of this reaction using the multivariate non-linear-regression method were f(α) = (1 − α)(1 + 4.1870α), 151.04 kJ·mol− 1 and 8.81, respectively, which were basically consistent with iso-conversion methods.

Graphical abstractA new class of asymmetrical dicationic ionic liquid [PyC3Pi][NTf2]2 has been synthesized and determined by X-ray diffraction. The structural unit belongs to the triclinic, thereinto, N(3) possesses 100% position probability, which only 50% for both N(4) and N(5), giving the charge neutral structure of the title compound. Thermal analysis reveals that the title compound decomposes in one transition in N2 atmosphere. The thermal decomposition kinetic analysis has also been reported.Figure optionsDownload full-size imageDownload as PowerPoint slide