Spectroscopic characterization of metal chloride/polyamide complexes

Complexes formed between metal halides MX_n (M=Li, Zn, Fe; X=Cl, Br) and an amorphous polyamide have been characterized by Infrared and Raman spectroscopies. They provide examples of the large variety of situations which can be generated by varying the concentration of the salts and their Lewis acidity. The LiX salts are dissociated and the lithium ion interacts with four amide oxygens or less, depending on the concentration, while the anion establishes N-H...X⁻ hydrogen bonds. Complexes with LiTFSI exhibit some ionic conductivity. Zinc halides are complexed under the form of a bent ZnX₂ molecule strongly coordinated to two or one amide oxygens depending on the concentration. Finally, FeCl₃ is ionized in the whole investigated concentration range into FeCl ₄ ⁻ and FeCl₂(L) ₄ ⁺ where L is the amide ligand coordinated to iron by its oxygen. Paper presented at the 2nd Euroconference on Solid State Ionics in Funchal, Madeira, Portugal, Sept. 10–16, 1995