Structure of lithium benzilate hemihydrate solved by simulated annealing and difference Fourier synthesis from powder data

Abstract

The crystal structure of lithium benzilate hemihydrate (C14H11O_3^-Li+·0.5H2O) was solved from synchrotron powder diffraction data. This compound crystallizes in the monoclinic space group P21/a. The structure was solved via the direct space search for two benzilate fragments using the simulated-annealing program DASH, localization of the lithium ions and water molecule from a difference Fourier map, and a restrained Rietveld refinement (R wp = 0.0687). The structure is a coordination polymer of [Li2(C14H11O3)2·H2O]2 tetramers building helical fourfold one-dimensional channels parallel to [010]. Inside the channels the tetrahedral coordination spheres of the lithium ions contain hydroxyl and carbonyl groups, and water molecules. The water molecule functions as the cohesive entity forming extended hydrogen-bonded chains running along [010], and bifurcated donor hydrogen bonds with the two nearest carboxylates. At the outer edge of the channels, weaker intermolecular C—H...Ph hydrogen bonds along [100] and [001] contribute to the supramolecular aggregation of the structure.