Regulating the Assembly of γ-Cyclodextrin Host and Polyoxometalate-Based Guests toward Light-Responsive Hybrid Rotaxanes

The rational design of hybrid organic-inorganic rotaxanes is crucial for advancing molecular machines and functional nanomaterials, yet the integration of metal-oxo clusters into interlocked systems remains challenging. Herein, we present a precision synthesis strategy for hybrid rotaxanes combining γ-cyclodextrin (γ-CD) hosts with Anderson-type polyoxometalate (POM)-based guests. This approach utilizes covalent POM modification coupled with strategically anchored organic functionalities to control supramolecular assembly, enabling the construction of pseudo-[2]-, [3]-, and [4]rotaxanes with controlled structural variations. Significantly, we achieved the first single-crystal examples of supramolecular pseudo-[4]rotaxanes featuring γ-CD dimers threaded by two organo-POM units. A key breakthrough was achieved through light-induced single-crystal-to-single-crystal transformation of these pseudo-[4]rotaxanes, producing hybrid [3]rotaxanes containing uniquely arranged anti-head-to-tail anthracene dimers─the first reported photoresponsive architecture of this type. These structural transformations demonstrate the dynamic, stimuli-responsive character of these hybrid systems. This work establishes a new paradigm for the precision engineering of rotaxanes using organo-POM building blocks, revealing their remarkable potential for creating smart materials with programmable structural changes. The successful integration of covalent modification, supramolecular templating, and photoresponsive components provides a powerful platform for developing next-generation multifunctional molecular machines and adaptive nanomaterials with precisely controlled properties.