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Figure 4
Hydrogen-bonded sheet of type Lx (Görbitz et al., 2009BB16) of L-Abu at 215 K and L-Nva at 293 K (top) and type L2 of L-Nva at 100 and 220 K (bottom). Side chains are shown as small spheres. Hydrogen bonds accepted by syn and anti carboxylate lone pairs are marked 1 and 2, respectively; distances (in Å) for L-Abu are average values for four molecules. In the L2 sheet, the H1B of molecule B (light grey C atoms) is involved in a three-centered interaction to the carboxylate group of molecule A (dark grey C atoms), with H1B⋯O2A as the shorter contact, while H1A participates in a two-centered interaction to O1B (H1A⋯O2B in orange is > 2.8 Å). In the Lx sheet all syn (1) hydrogen bonds are similar, with H1⋯O1 as the shorter component of a three-centered interaction.

IUCrJ
Volume 3| Part 5| September 2016| Pages 341-353
ISSN: 2052-2525
doi:10.1107/S2052252516010472