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

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.