Fluxionality-Induced Enantiomerisation in Ligand Design

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A molecule or material is chiral if it is nonsuperimposable on its mirror image. This property is a key handle for controlling the function of therapeutics, catalysts, and electronic devices. The most versatile and widely used structural units in chiral organic molecules are sp3-hybridised carbon centres. On one hand, their tetrahedral geometry is ideal for making shape-persistent, inflexible structures that transmit 3D stereochemical information with high fidelity. But on the other hand, they lack an ability present in other stereogenic elements (helices, chiral planes, etc.) of flipping between their mirror-image forms. FIELD bridges this knowledge gap by pioneering fluxional carbon-centred stereochemistry. It develops the synthesis, analysis, and applications of rigid small molecules that rapidly flit between their mirror-image structures, undergoing fluxionality-induced enantiomerisation. FIELD establishes the ground rules for obtaining and exploiting fluxionally chiral carbon cages. It enumerates a series of molecular structures that are predicted to undergo this type of transformation, identifying ways to tune the dynamics, improve 3D differentiation between enantiomers, and connect the cages to other molecular components. Importantly, it develops ways to transmit the dynamic properties of the rigid cages to stereogenic transition metal ions, broadening the scope for their applications. The resulting stimulus-responsive fluxionally chiral complexes have properties that are potentially useful for amplifying the enantioinduction in asymmetric catalysis, and for writing and reading information with chiroptical materials. Overall, FIELD rethinks a fundamental aspect of organic chemistry by forming paradoxical structures that are simultaneously rigid cages, while also having mouldable chirality.