CRYSTAL ENGINEERING OF HYDROGEN-BONDED CO-CRYSTALS BETWEEN CYANURIC ACID AND DIAMIDE MOLECULES - INVESTIGATIONS ON THE FORMATION AND STRUCTURE OF CO-CRYSTALS CONTAINING CYANURIC ACID AND OXALYL DIHYDRAZIDE

The design and structural rationalization of hydrogen-bonded co-crystals formed between cyanuric acid and ‘diamide’ molecules (e.g. RNHCONHCOR′, RNHCOCONHR′ or RCONHNHCOR′) is discussed. In the knowledge of the hydrogen-bonding arrangement in the cyanuric acid–biuret co-crystal, a strategy for the design of other hydrogen-bonded co-crystals of cyanuric acid has been developed, and the first attempt to apply this strategy in the design of hydrogen-bonded co-crystals between cyanuric acid and oxalyl dihydrazide is reported. The preparation conditions employed have led to a 1 : 1 : 2 co-crystal of cyanuric acid, oxalyl dihydrazide and water (rather than a 1 : 1 co-crystal of cyanuric acid and oxalyl dihydrazide analogous to cyanuric acid–biuret), and the structural properties of this new co-crystal are reported. The results obtained are discussed in the wider context of assessing the potential for the formulation, development and exploitation of successful crystal engineering strategies for the design of hydrogen-bonded organic molecular crystals.