Control of the Single-Molecule Magnet Behavior of Lanthanide-Diarylethene Photochromic Assemblies by Irradiation with Light

Lanthanide-based extended coordination frameworks showing photocontrolled single-molecule magnet (SMM) behavior were prepared by combining highly anisotropic Dy-III and Ho-III ions with the carboxylato-functionalized photochromic molecule 1,2-bis(5-carboxyl-2-methyl-3-thienyl)perfluorocyclopentene (H(2)dae), which acts as a bridging ligand. As a result, two new compounds of the general formula [{Ln(2)(III)(dae)(3)(DMSO)(3)(MeOH)}center dot 10MeOH](n) (M=Dy for 1a and Ho for 2) and two additional pseudo-polymorphs [{Dy-2(III)(dae)(3)(DMSO)(3)(H2O)}center dot xMeOH](n) (1b) and [{Dy-2(III)(dae)(3)(DMSO)(3)-DMSO)}center dot xMeOH](n) (1c) were obtained. All four compounds have 2D coordination-layer topologies, in which carboxylate-bridged Ln(2) units are linked together by dae(2-) anions into grid-like frameworks. All four compounds exhibited a strong reversible photochromic response to UV/Vis light. Moreover, both 1a and 2 show field-induced SMM behavior. The slow magnetic relaxation of 1a is influenced by the photoisomerization reaction leading to the observation of the cross-ffect: photocontrolled SMM behavior.