Chiral Interlocked Molecule: Synthesis and Function

Chirality appeared in interlocked systems such as catenanes, knots, and rotaxanes has attracted particular interest due to its possibility producing large and flexible asymmetric field, in addition to the switch function based on high mobility of the components. The exploration of new chiral molecules and systems is of great significance in association with their function and capability as chiral source, from viewpoint of vast stretch of chirality in many scientific fields. In this review, we first introduce the paradigm of the rotaxanes' stereoisomerism, and then the recent advance on the synthesis of interlocked molecules, mainly of rotaxanes with mechanically planar chirality as one of molecular chiralities. Use of such rotaxanes as a chiral source in secondary structure control of polymers is also discussed as the first application of the mechanically planar chiral rotaxanes, with special emphasis on the dynamic helicity change of polyphenylacetylenes and poly(m-phenylene diethynylene) bearing the chiral pendant rotaxane group.