Structural Rationalisation of Co-crystals Formed between Trithiocyanuric Acid and Molecules Containing Hydrogen Bonding Functionality

Crystallisation of trithiocyanuric acid (TTCA) from various organic solvents that have hydrogen bonding capability (acetone, 2‐butanone, dimethylformamide, dimethyl sulfoxide, methanol and acetonitrile) leads to the formation of co‐crystals in which the solvent molecules are incorporated together with TTCA in the crystal structure. Structure determination by single‐crystal X‐ray diffraction reveals that these co‐crystals can be classified into different groups depending upon the topological arrangement of the TTCA molecules in the crystal structure. Thus, three different types of single‐tape arrangements of TTCA molecules and one type of double‐tape arrangement of TTCA molecules are identified. In all co‐crystals, hydrogen‐bonding interactions are formed through the involvement of NH bonds of TTCA molecules in these tapes and the other molecule in the co‐crystal. Detailed rationalisation of the structural properties of these co‐crystals is presented. A systematic basis for predicting and rationalising the structures of co‐crystals formed between trithiocyanuric acid TTCA and other molecules containing hydrogen bonding functionality has been achieved. The co‐crystals are conveniently classified according to the structural arrangement of the TTCA molecules, which comprises either double‐tapes or single‐tapes (of which there are three distinct types) of TTCA molecules. The picture shows the structure of the TTCA/acetone co‐crystal.