Structure- and phase-transformable coordination polymers/metal complexes with fluorinated anions

Abstract

Materials that can undergo structural or phase transformations have attracted considerable attention as functional materials in many fields for electric, magnetic, optical, adsorption, separation, or catalysis applications. Outstanding examples of structure-switchable or phase-changeable metal complexes with fluorinated anions have been reported. This review focuses on recent advances in the literature on coordination polymers and metal complexes with fluorinated anions. For representative examples, the physical/chemical properties (crystal-to-crystal, crystal-to-plastic crystal, and crystal-to-liquid phase changes, guest accommodation/removal, magnetic properties, etc.) induced by external stimuli such as temperature/pressure changes are discussed, with comparisons to the properties of coordination polymers/metal complexes with nonfluorinated anions. In addition, ELM-11 (ELM = elastic layer-structured metal–organic framework) with fluorinated BF4 anions, which is the first discovered structure-switchable, crystalline coordination polymer with fluorinated anions showing gate adsorption/desorption properties, is examined. The coordination states of fluorinated anions in coordination polymers/metal complexes, together with the adsorption/separation properties, are also considered. These insights can aid in understanding the roles and features of fluorinated anions in such materials.