Networks of the melamine and cyanuric acid motif
The extensive role hydrogen bonding plays in nature has been repeatedly emulated in the laboratory to produce both extensive networks and discrete aggregates. As the principle interaction between many component groups, supramolecular chemists have employed hydrogen bonding to form various assemblies, and consequently this has become of increasing interest to biologists, chemists and biochemists. Lehn, Cram, Etter, Reinhoudt and Whitesides have carried out notable work in this field. It is the challenge of synthetic chemists to produce supramolecular structures, which can contribute towards areas of research as diverse as catalysis, electronics, medicine and nanotechnology. The complementary cyanuric acid and melamine components utilise hydrogen bonding in large numbers to form the highly ordered (CA.M) motif, which creates an infinite 2-D hexagonal lattice. It has been shown that by selectively attaching different bulky groups to the two amine groups on the melamine component, the preferential formation of either two types of 1-D polymers or an additional cyclic hexagonal aggregate may form. The latter, also referred to as a rosette has been comprehensively studied, however, it is the view of the author that the scope available for the adaptation of this particular aggregate has not been fully exploited. In this work a variety of novel compounds have been prepared based upon both the cyanuric acid and melamine structures. Classical synthetic chemistry based around the cyclisation of malonates and biurets have been supplemented with the exploitation of the Sonigashira palladium catalysed cross-coupling reaction to furnish a range of new linear bis(isocyanuric acids). The synthesis of a melamine incorporating a pyridine group has now allowed the study of both metal coordinate binding and hydrogen bonding within this type of system. In addition the synthesis of a range of verdazyl radicals also attached to pyridyl groups have been accomplished.