Two-Dimensional Hydrogen Bond Networks Supported by CH/π Interaction Leading to a Molecular Packing Appropriate for Topochemical Polymerization of 1,3-Diene Monomers

Strong and weak hydrogen bonds, as intermolecular interactions, are used for the construction of
designer crystals with organic small molecules as the building blocks. We report here crystal engineering for the
synthetic plan of the topochemical polymerization using the ammonium derivatives of 1,3-diene mono- and dicarboxylic
acids on the basis of intermolecular interactions such as NH/O and CH/π interactions. The isomerism of hydrogen
bond network structures obstructs the prediction of crystal structure and reactivity, although topochemical
polymerization requires that monomer molecules stack in a column with a stacking distance of 5 Å in the crystals.
The structures of hydrogen bond networks are roughly classified into a two-dimensional type appropriate for
topochemical polymerization, and the others consisting of two-dimensional sheets or one-dimensional ladders not
for polymerization. We conclude that the CH/π interaction of naphthylmethyl and benzyl substituents promises to
give polymerizable lamella crystals, of which the interface is supported by robust two-dimensional hydrogen bond
networks reinforced by lining with CH/π interaction between benzylic and aromatic hydrogens and π-electrons.