Chiral Symmetry-Breaking Transition in Growth Front of Crystal Phase of 1,1′-Binaphthyl in Its Supercooled Melt

Although the theory of spontaneous chiral symmetry-breaking in open systems was proposed some time ago, experimental realization of this phenomenon has not been achieved. In this article, we note that the crystal growth front of 1,1′-binaphthyl shows many of the characteristics of an open system in which chiral symmetry-breaking has occurred. We studied the temperature profiles of the crystallizing surface and obtained X-ray diffraction data of the crystals grown from the melt under controlled conditions. The data show that, under appropriate conditions, the observed bimodal probability distribution of enantiomeric excess (ee) with maxima ∼60% is due exclusively to chiral crystals and not due to racemic crystals of 1,1′-binaphthyl that can also form at large supercooling. The mass independence of the ee shows that the growing front maintains a constant ee, which is a clear signature of open systems in steady state.