Chiral self-sorting and amplification in isotropic liquids of achiral molecules

Abstract

According to our present knowledge, the spontaneous resolution of racemic mixtures of chiral molecules or chiral conformers of achiral molecules into macroscopic chiral superstructures requires the confinement of these molecules in a crystal lattice, on surfaces or in other well-ordered assemblies. Herein we provide the first experimental evidence that mirror-symmetry breaking can also take place at a liquid-liquid phase transition in isotropic liquids of achiral molecules, even at relatively high temperatures around 200 °C. It is proposed that cooperative segregation of enantiomorphic molecular conformations gives rise to a conglomerate of two chiral and immiscible liquids. In these liquid conglomerates a strong chiral amplification was observed, which led to degeneracy from a stochastic distribution and eventually provided uniform chirality. We anticipate that this work will contribute to the understanding of symmetry breaking in soft matter and provide a new tool for the identification of chirality traces, and possibly affect the discussion of the emergence of chirality in prebiotic systems.

On the influence of a network on optically isotropic fluid phases with tetrahedral/octupolar order

“…It thus leads to a spontaneous mirror symmetry breaking in an optically isotropic liquid phase of achiral molecules. Such a spontaneous mirror symmetry breaking has indeed been observed very recently by the group of Tschierske [14][15][16]. In two cases [14,16] the chiral domains appeared in an optically isotropic liquid phase below a truly isotropic liquid phase, while in the other case [15] chiral domains of opposite hand were arising as a reentrant optically isotropic liquid phase below a truly isotropic liquid phase and a nematic phase.…”

“…Quite recently isotropic-isotropic phase transitions have been observed for several compounds composed of achiral molecules with liquid crystalline phases following at lower temperatures [13][14][15][16][17]. In one case a liquid crystalline tetragonal phase showing a linear electro-optic effect was observed at lower temperatures [13], while in the other three cases Tschierske's group reported the existence of mesoscopic to macroscopic chiral domains of either hand in the lower temperature optically isotropic phase [14][15][16].…”

“…In one case a liquid crystalline tetragonal phase showing a linear electro-optic effect was observed at lower temperatures [13], while in the other three cases Tschierske's group reported the existence of mesoscopic to macroscopic chiral domains of either hand in the lower temperature optically isotropic phase [14][15][16]. This observation was linked to the formation of clusters and or agglomerates of substantial size and associated with steric and packing interactions [14][15][16]. It is worth noticing that all the molecules forming these clusters and/or agglomerates are fairly large and bulky and rather distinct from typical rod-like molecules forming usual low molecular weight nematic phases.…”

“…We show that this crosscoupling term not considered before leads to ambidextrous helicity and thus provides a possible explanation for the chiral domains of both hands observed in refs. [14][15][16]. Or to phrase it more succinctly: we suggest a novel scenario of chiral symmetry breaking in the mesoscopic and macroscopic domain, which might be useful also for other areas from condensed matter and biological physics.…”

Metallomesogens: Retrospectives and Perspectives

“…супрамолекулярные металломезогены на основе полидентантных лигандов образуют геликоидальные макроско-пические структуры, являясь интересным примером проявления хиральности на макроскопическом уровне при отсутствии моле-кулярной ассиметрии [126]. Спонтанное прояв-ление хиральности на макроскопическом уровне нередко обнаруживается при супрамолекулярной самосборке, и к настоящему времени как явление наблюдалось во всех основных конденсированных фазовых состояниях вещества, начиная с кристаллического вплоть до жидкого [127]. Возникновение макроскопических хиральных областей из ахиральных молекул в жидких средах, включая текучие жидкокристаллические среды, представляет особый интерес.…”