Concomitant Photoresponsive Chiroptics and Magnetism in Metal-Organic Frameworks at Room Temperature

Stimulus-responsive metal-organic frameworks(MOFs)can be used for designing smart materials.Herein,we report a family of rationally designed MOFs which exhibit photoresponsive chiroptical and magnetic properties at room temperature.In this design,two specific nonphotochromic ligands are selected to construct enantiomeric MOFs,{Cu_(2)(L-mal)_(2)(bpy)_(2)(H_(2)O)·3H_(2)O}n(1)and{Cu_(2)(D-mal)_(2)(bpy)_(2)(H_(2)O)·3H_(2)O}_(n)(2)(mal=malate,bpy=4,4’−bipyridine),which can alter their color,magnetism,and chiroptics concurrently in response to light.Upon UV or visible light irradiation,long-lived bpy−radicals are generated via photoinduced electron transfer(PET)from oxygen atoms of carboxylates and hydroxyl of malates to bpy ligands,giving rise to a 23.7%increase of magnetic susceptibility at room temperature.The participation of the chromophores(-OH and-COO^(−))bound with the chiral carbon during the electron transfer process results in a small dipolar transition;thus,the Cotton effects of the enantiomers are weakened along with a photoinduced color change.This work demonstrates that the simultaneous responses of chirality,optics,and magnetism can be achieved in a single compound at room temperature and may open up a new pathway for designing chiral stimuli-responsive materials.