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Hydrogen Bonding and Structural Motifs in Organic l-Malate(2−) Salts

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posted on 13.06.1996 by Christer B. Aakeröy, Mark Nieuwenhuyzen
To examine packing preferences and hydrogen-bond patterns in organic l-malate salts [AH2][mal] or [AH]2[mal] (where A = amine), the syntheses and crystal structures of six new salts, bis(4-chlorobenzyl)ammonium(1+) l-malate(2−) monohydrate (1), ethylenediammonium(2+) l-malate(2−) (2), piperazinium(2+) l-malate(2−) monohydrate (3), bis(3-methylbenzyl)ammonium(1+) l-malate(2−) (4), bis(3-chlorobenzyl)ammonium(1+) l-malate(2−) monohydrate (5), and 1,6-hexanediammonium(2+) l-malate monohydrate (6), are presented. In contrast to the structurally consistent hydrogen malate salts, these compounds show a variety of unpredictable packing patterns which demonstrates that the removal of a single hydrogen-bond interaction can substantially alter the structure of a family of ionic compounds. This observation lends considerable support to design strategies which employ hydrogen bonding as means of linking ionic building blocks into predictable multidimensional architectures. The structural effects of hydrogen bonding is discussed in detail, and the use of a combination of single-crystal and powder X-ray diffraction techniques for assessing structural purity is addressed.