RELAXATION KINETICS AND INFRARED-SPECTRA OF THE COMPLEXATION OF LITHIUM ION BY TRIETHYLENE GLYCOL AND BY TETRAETHYLENE GLYCOL IN ACETONITRILE

Ultrasonic absorption relaxation spectra are reported covering the frequency range approximately 1-500 MHz for the complexation of LiClO4 by the open-chain polyethers triethylene glycol (EG3) and tetraethylene glycol (EG4) in acetonitrile at 25-degrees-C and at a molar ratio R = [EG3]/[LiClO4] or R = [EG4]/[LiClO4] = 1. The ultrasonic spectra can be described by the sum of two Debye relaxation processes which were interpreted according to the Eigen-Winkler mechanism Li+ + EG reversible(k0) Li+...EG reversible (k1)(k-1) Li+EG reversible (k2)(k-2) (Li+EG) (where EG denotes either EG3 or EG4), giving the rate constants k1, k-1, k2, and k-2. The first step is taken to be a preequilibration step for which K0 is calculated from classical statistical theory. The rate constants are compared with those of the corresponding process involving triglyme and poly(ethylene oxide) (PEO) previously reported. Infrared data for the 3800-3200-cm-1 region show a shift of 70 cm-1 to lower energy, indicating a strong interaction between the ethanolic oxygen of EG3 and the Li+ ion.