Kinetics and thermodynamic parameters of the thermal decomposition of bis(imipraminium)tetrachlorocuprate, bis(imipraminium)tetrachloromercurate and imipraminium reineckate

摘要

The complex ion-pairs of imipraminium ion with CuCl_4~(2-), HgCl_4~(2-) and [Cr(NH_3)_2(SCN)_4]~- have been prepared, identified and thermally analysed. The structure of the complex ion-pair has been proved by X-ray diffraction of a single crystal. The complex ion-pairs are bis(imipraminium)tetrachlorocuprate(II), bis(imipraminium)tetrachloromercurate(II) and imipraminium reineckate. Non-isothermal and isothermal decompositions of the above ion-pairs have been studied and the results were statistically analyzed. The thermal decomposition reaction of each ion-pair is shown to be a two-steps reaction and each step is a first-order reaction. The kinetic parameters: activation energy, E_a, and the pre-exponential term, A, were calculated for each step of the reaction. The theory of activated complex has been applied to each step of the reaction and the thermodynamic functions ΔH~≠, ΔG~≠ and ΔS~≠ are calculated. A stiff and rigid activated complex (transition state) led to a lower degrees of freedom of rotation and vibration and hence to a negative value of ΔS~≠ is obtained which means the formation of a stiff and rigid activated complex (transition state) with fewer degrees of freedom of rotation and of vibration. The thermal stability of the studied complexes varies in the order: imipraminium reineckate bis(imipraminium)tetrachloromercurate(II) > bis(imipraminium)tetrachlorocuprate(II).