Molecular Lanthanide Switches for Magnetism and Photoluminescence

Solvation of [(CNT)Ln(η$^8$-COT)] (Ln=La, Ce, Nd, Tb, Er; CNT=cyclononatetraenyl, i.e., C$_9$H$_9$−; COT=cyclooctatetraendiid, i.e., C$_8$H$_8$$^2−$) complexes with tetrahydrofuran (THF) gives rise to neutral [(η$^4$-CNT)Ln(thf)$_2$(η$^8$-COT)] (Ln=La, Ce) and ionic [Ln(thf)$_x$(η$^8$-COT)][CNT] (x=4 (Ce, Nd, Tb), 3 (Er)) species in a solid-to-solid transformation. Due to the severe distortion of the ligand sphere upon solvation, these species act as switchable luminophores and single-molecule magnets. The desolvation of the coordinated solvents can be triggered by applying a dynamic vacuum, as well as a temperature gradient stimulus. Raman spectroscopic investigations revealed fast and fully reversible solvation and desolvation processes. Moreover, we also show that a Nd:YAG laser can induce the necessary temperature gradient for a self-sufficient switching process of the Ce(III) analogue in a spatially resolved manner.