Kristallistrukturanalyse von lösungsmitterfreiem Lithium-benzoat. Relevanz föur die Material-eigenschaften von Lithium-carboxylaten?

Abstract

Anhydrous Li benzoate crystallizes from water as very thin, soft, and flexible platelets. The poor quality of these crystals rendered the data collection for the crystal structure determination very difficult. Anisotropic refinement did not reduce the R value below 0.1. The Li benzoate molecules form a two-dimensional polymeric structure consisting of a grid of lithium and carboxylate O-atoms, with the Ph groups forming kind of a covering layer on each side. The polymeric layers are stacked with phenyl CH groups pointing towards each other. Thus, very weak van-der-Waals forces hold the layers together. This structural feature is in agreement with the macroscopic properties of the crystals and probably causes Li carboxylates to be valuable components of high-temperature, high-performance greases (for instance in the vacuum technology). The structures of Li benzoate and of other Li carboxylates may also provide a clue for the fact that ionomers containing LiOOC groups are especially tough materials.