Recent Advances in Single-Crystal-to-Single-Crystal Transformation at the Discrete Molecular Level

The present review focuses on the solid state structural transformations in discrete molecules. Since the molecules in the crystal lattice are closely packed, any transformation in the solid state is difficult due to restricted movement of the molecules. These transformations can be triggered by external stimuli, such as light, heat, uptake or exchange of solvent, mechanochemical force, etc. which may be observed by a change in their physical properties like color, magnetism, porosity, and optical. Single-crystal-to-single-crystal (SCSC) transformations in metal–organic frameworks and coordination polymers are well documented; however, reports on SCSC transformations at the discrete molecular level still remain scarce. In this review, we have compiled some interesting examples from the literature on SCSC transformation at the discrete molecular level using various external stimuli.