What Triggers Supramolecular Isomerism in Nonmolecular Solids? A case study of Copper Pyridazine Halides

Molecular recognition and aggregation occurring in solution are critical events towards the nucleation and growth of a crystal. However, controlling aggregation towards a particular supramolecular assembly is difficult due to lack of information on its thermodynamics and kinetics. Hence, the occurrence of supramolecular isomers is hardly recognized. In this paper, therefore, we demonstrate a retrosynthetic analysis to interpret the occurrence of isostructures and supramolecular isomers and predict the possibility of new phases in copper halide-pyridazine-H 2 O system. A significant feature of this paper is the use of crystal engineering tools, namely, synthons and tectons to interpret the phase diagram of a system. The structure-synthesis correlation discussed here provides chemical insight to evolve a synthetic protocol to interpret and predict the possibility of supramolecular isomers in metal organic solids. Graphical Abstract [Cu II ( pdz )X 2 ], 1 – 2 ; [Cu 2 I ( pdz )X 2 ], 3 - 5 ; [CuI( pdz )X], 6 – 8 and [Cu 2 I ( pdz )3Cl 2 ]. 3 H 2 O, 9 where pdz = pyridazine, were crystallized from aqueous solution for the first time and their structure elucidation was carried out using X-ray crystallographic techniques. Growth of isostructures and supramolecular isomers in 1 – 9 has been interpreted in terms of tectons ( I – III ).