Structural Dependence of Catenand Effect: Thermodynamic and Kinetic Modulation of Catenane Coordination Properties via Ring-size and Exocyclic Substituent Variation.

Although the effects of ligand interlocking on specific features of coordinated metal were first reported in 1980s', strategies to precisely control these features through structural modifications of interlocked ligands remains underdeveloped. This limitation has hindered the broader exploitation of this unique class of coordination compounds across various fields of transition metal chemistry. Through a systematic comparison and detail analysis of a series of CuI catenane complexes, we show in this work that the size of the interlocked rings and exocyclic substituents are important structural parameters that regulate the exposure of the metal coordination sphere, which also influences the coordination geometry, electronic structures, spectroscopic, photophysical and electrochemical properties, as well as thermodynamic stability, ligand exchange kinetics, and chemical reactivity of the coordinated metal. Relationship between the structural features of the catenane and the extent of these effects is also revealed. These insights not only faciliate the rational design of a new type of switchable catenane catalyst wherein the interlocked structure is preserved, but also establish new principles for leveraging the unique effects of mechanical interlocking for diverse applications involving coordination complexes.