Phase-Sensitive Supramolecular Chirogenesis in Bisporphyrin Systems

To date, the field of supramolecular chirality has attracted much attention in the scientific community, in the context of its direct connection with various natural systems and many practical applications in the areas of catalysis,[1] nonlinear optics,[2] polymer and materials science,[3] molecular recognition,[4] molecular devices,[5] and absolute configuration determination.[6] As noncovalent interactions are the key elements of supramolecular chemistry, there are various external and internal factors controlling chirality induction in these systems. Among these influences, the phase transition, or aggregation state, takes on particular significance in the light of the wide prospective applications of optically active systems in the solid state.[7] However, this important factor has not yet been well investigated and rationalized. Here, by applying supramolecular chemistry, solid-state optical spectroscopy, and exciton chirality principles, we describe a novel and intriguing phenomenon of phasetransition controlled chirality induction in a supramolecular system, which consists of an achiral host and a chiral guest.[8] Ethane-bridged bis(zinc octaethylporphyrin),[9] which is in a syn conformation in nonpolar solvents (see syn ZnD in Figure 1), was chosen as an achiral host molecule. This