Photoresponsive Magnetic Relaxation Behavior of a Highly Stable ??? Interaction-Stacked Framework Based on a Dy^III Single-Ion Magnet

A highly stable and photoresponsiveLn-SIM system has beenachieved by designing and synthesizing a & pi;& BULL;& BULL;& BULL;& pi;interaction-stacked framework (& pi;OF) based on Dy-III-SIMs, which suggests a new strategy to fabricate stable and/or photoresponsiveLn-SIMs. Endowing lanthanide single-ion magnets (Ln-SIMs) withhigh stabilityand stimulus responsiveness is of significance for the practical applicationsof these novel magnetic materials, but still of challenge at present.Herein, we report on a highly stable and photoresponsive Ln-SIM systemachieved by designing and synthesizing a & pi;& BULL;& BULL;& BULL;& pi;interaction-stacked framework based on Dy-III-SIM (& pi;OF-1). Its molecular formula is [Dy(thqa)] (H(3)thqa = tris[(8-hydroxyquinoline-2-yl)methylene]amino). Each of its C (3)-symmetric molecules consists of a thqa(3-) ligand and a Dy-III ion, and it is linkedto three neighbors by intermolecular & pi;& BULL;& BULL;& BULL;& pi;interactions, forming a supermolecular two-dimensional (2D) honeycombedtopology. Such unique structure endows & pi;OF-1 with not only air and thermal stability but also excellentchemical stability in different solvents, even in alkali solutions,including a 20 M NaOH aqueous solution. Dual magnetic relaxation behaviorwas observed in & pi;OF-1. Magnetic dilutionrevealed that it is related to & pi;& BULL;& BULL;& BULL;& pi;-mediatedintermolecular magnetic interactions. More significantly, both thestatic magnetic susceptibility and the dual-relaxation behavior of & pi;OF-1 show response to photoirradiation,which could be ascribed to the photo-triggered intermolecular & pi;& RARR; & pi;* charge transfer (CT). So far as we know, & pi;OF-1 could be the first Ln-SIM system possessing botha high stability and photoresponsiveness, and also the first photoresponsiveLn-SIM supermolecular system that does not rely on the single-crystalto single-crystal (SCSC) structural transformation. Its successfuldesign and synthesis suggests that the introduction of & pi;& BULL;& BULL;& BULL;& pi;interactions can be a new strategy to fabricate stable and/or photoresponsiveLn-SIMs.