MOLECULAR RECOGNITION IN THE SOLID-STATE - HYDROGEN-BONDING CONTROL OF MOLECULAR AGGREGATION

The design of molecular subunits that self-assemble into well-defined structures in the solid state is an area of intense current interest. A key to controlling the packing arrangement lies in manipulating the type and orientation of the non-covalent interactions between the subunits. The strong and directional nature of hydrogen bonds has led to their widespread use in self-assembling systems. In the solid state, rules have been delineated to allow the reasonable prediction of hydrogen-bonding packing patterns in crystals. This had led to a search for molecular components that because of their hydrogen-bonding characteristics will form persistent packing motifs in well-defined shapes or patterns. We have recently discovered that a strong bidentate hydrogen bonding interaction is formed between 2-amino-6-methylpyridine and carboxylic acids. Bis(2-amino-6-methylpyridine) derivatives and dicarboxylic acids will self-assemble into alternating cocrystal structures. The packing of the two components can be controlled in a rational way by changing the nature, size, and orientation of the spacer groups that link the hydrogen-bonding subunits.