Studies on the development and generalization of the preparative method of organic crystals with a specific crystal structure by controlling the mode of polymorphic transition

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By this research, we have established the methodologies (1) to clarify the supramolecular structure in the supersaturated solution of an organic compound, (2) to isolate the metastable crystals formed kinetically from the supersaturated solution and elucidate the crystal structure, and (3) to elucidate the mechanism of polymorphic transition of the metastable polymorphic form into the stable polymorphic form during crystallization from the supersaturated solution.By using these methodologies, it has been clarified that Preferential Enrichment, an unusual enantiomeric resolution phenomenon which we found, is an event of a complexity system which can easily lead to the symmetry breaking. Namely, (1) a molecular prenucleation aggregate or a metastable crystalline phase is regarded as an chaos state, (2) the phase transition between the chaos states induces symmetry breaking characteristic of a complexity system, and (3) additional increasing returns phenomenon occurs in solution. Since it is known that the phase transition in a complexity system is controlled by external effects, we have investigated the control of Preferential Enrichment. As a result, we have succeeded in the induction and inhibition of Preferential Enrichment by controlling the mode of polymorphic transition with seed crystals. This result lends additional support to our proposed mechanism of Preferential Enrichment. Furthermore, for the first time, we have successfully induced polymorphic transition on the surface of a seed crystal and have referred to this phenomenon as Epitaxial Transition.Furthermore, we have found a new mode of polymorphic transition that can induce Preferential Enrichment. This result indicates the mechanistic flexibility in the polymorphic transition inducing Preferential Enrichment. Therefore, by carefully choosing the kinetic crystallization conditions or seeding with appropriate crystals, Preferential Enrichment may be applicable to certain racemic compounds.