Stimuli-Responsive Photoswitch-Actinide Binding: A Match Made in MOFs

Abstract

The fundamentals of switchable actinide-ligand binding modes are central for designing new platforms for addressing challenges associated with, for example, isolation of pure radiological daughters for nuclear medicine or methods for efficient nuclear stockpile recycling. This study is the first to report actinide binding modes controlled by an external stimulus via photochromic moieties, realized through probing thermodynamics and kinetics aspects, including changes in photoswitch isomerization constants upon metal coordination and enthalpies associated with the synergistic actinide-switch photochromic processes. A comprehensive analysis of the presented concept was executed through evaluation of data acquired through a multivariate strategy involving isothermal titration calorimetry, crystallography, spectroscopy, and theoretical modeling on the example of actinide-containing compounds based on thorium(IV)-, and uranium(IV, VI), as well as transuranic elements such as plutonium(IV) in solution and within a metal-organic framework (MOF) matrix for the first time. Overall, the presented concept could usher in an alternative direction in stimuli-responsive actinide-based platforms that could be adapted to confront current and upcoming challenges in f-block chemistry.